Respiratory Systems role in the functioning body

Word Count: 10293 |

Whether it is sleeping, talking, walking or running all these activities require one important factor, the ability to breath. From the first breath after birth to our very last breathe taken, the rate and depth of respiration is unconsciously monitored and matched to the body’s activity. Although the human body has the ability to stop breathing, within a few minutes it will require to breathe again. Breathing is so highly characterised with life and living that apart from our pulse it is one of the first things checked to determine whether a person is alive. (Seeley R. 2005) The term respiration, otherwise commonly known as breathing, refers to three separate, yet very related principle functions. These functions are ventilation, oxygen utilisation and gas exchange (respiration). Briefly, the latter function allows for oxygen from air to enter the blood while allowing carbon dioxide (CO2), produced by cells, to leave the body. Respiration is a necessary body system because all living cells within the body require oxygen. The respiratory system performs this function and is solely responsible for producing the body’s oxygen requirements. (Ross M. 2006) (Myers A. 2002)

The major structures that make up the respiratory system are the nasal cavity, pharynx, (Conducting portion or upper respiratory system) larynx and trachea, the bronchi, bronchioles, and the pulmonary alveoli within the lungs (Respiratory portion or lower respiratory system). These structures all work together to perform four basic functions. Providing oxygen to the blood stream while removing carbon dioxide, enabling sound production or vocalization, assisting in abdominal compression, required during urination, defecation and childbirth. It allows for protective and reflexive breathing movements, the ability to cough and sneeze. (Myers A. 2002) The respiratory system is a highly intricate system that provides human beings with many abilities. It requires the use of many cells, tissues and other body systems working simultaneously together. (Hlastala, M.P. 1996) These features are highlighted within figure 1.1.
Fig 1.1: Highlights the main component of the respiratory system.
Sourced: http://emptynosesyndrome.org/pics/image001.gif
The purpose of this essay will be to outline further the key functions, role and mechanisms of the respiratory system, while highlighting the various tissues that comprise of the system. Additionally, these various tissues types will be discussed individually, with emphasis placed on their key features and their role in the functioning of this body system. Tissue types that will be discussed are Epithelium Tissue, Muscular Tissue, Nervous tissue and Connective Tissue. This will further illustrate the role each tissue plays within the system while highlighting the inner workings of the respiratory system itself.

In order to understand the function, role and mechanics required for performing respiration one must first understand what tissues are and the different types of tissues that the system is comprised of. It is these tissues that in turn allow for respiration to occur. Tissues are aggregations of similar cells and cell products that work together to perform specific functions. (Lawrence E. 2006) Although it is understood that cells are the basic functional units of the body, it can be argued that tissues are the functional units of the body. (Seeley R. 2005) It is the collaboration of all the individual cells present within tissues that are responsible for maintaining body function. It is a cells ability to communicate which allows for this collaboration to occur. (Campbell N. 2006) Understanding tissue mechanics highlights that it is the cells, which make up the tissue that provide their function and role. (Ross M. 2006) The human body is comprised of four basic tissues, Epithelium Tissue (Epithelial tissue), which covers body surfaces, lines body cavities, ducts and forms glands, Connective Tissue, which underlies, supports, binds and protects the other basic tissues structurally and functionally, Muscular Tissue which contracts to produce movement while Nervous Tissue receives and transmits information received from outside and inside the body in the form of nerve impulses. (Ross M. 2006) (Myers A. 2002)

Fig 2.2: Illustrates the basic differences between each type of tissue.
Sourced: http://health.allrefer.com/pictures-images/tissue-types.html
These four major tissues are broken down further on the basis of specific characteristics. In the case of epithelium, the number of cell layers and shape of the surface result in the terminology refecting their structure, for this reason Epithelium tissue is subdivided into the following classifications, cell shapes included squamous, cuboidal and columnar while layers are classified by simple (single layer) or stratified (multiple layers). (Ross M. 2006) (Lawrence E. 2006) (Seeley R. 2005). Connective tissue (C.T) is primarily classified accordingly to it composition and organization, and is characterised by the amount of extracellular material that separates cells from one another. This extracellular material is comprised of three major components, protein fibres, ground substances and fluid. For this reason connective tissue is subdivided into Areolar C.T, Adipose Tissue, Dense regular C.T, Dense irregular C.T, Elastic C.T, Reticular C.T and Cartilage (Hyaline, Fibro and Elastic). While muscular and nervous tissue is based on their function rather then their structure. Muscular tissue is unique in this way as it has the ability to contract and relax which makes movement possible. This movement is achieved through the shortening of muscle fibres in response to a stimulus. There are four types of muscular tissue, Skeletal, Visceral striated, Cardiac and Smooth muscular tissue. Smooth muscle tissue, skeletal and visceral striated muscle is the predominant muscle type present within the respiratory system and for this reason will be the main muscular tissues focused on. (Gillison M. 1966) (Myers A. 2002) Nervous tissue is composed of neurons, these neurons respond to stimuli and conduct impulses to and from all body organs. There are three principal components in nervous tissue, cell body, dendrites and axons. (Myers A. 2002) These tissues play important roles structurally and functionally throughout the body. Although not all subunits of each basic tissue play a direct role in respiration they are equally important within the body. The following paragraphs look to highlight the roles and functions of each subdivision involved in the respiratory system in closer detail.

As previously discussed Epithelium tissue is classed according to shape and layers thus only structure and not function is described. It is by describing the cell number and cell shape that the various configurations can be classified. Thus epithelium tissue can be divided into eight sub-types of epithelium. These are as follows, Simple squamous, simple cuboidal, simple columnar, pseudostratified, stratified squamous, stratified cuboidal, stratified columnar and transitional. (Ross M. 2006) (Van De Graaff K. 2002). Each type of epithelium can be seen to play a role within the respiratory system thus the functions it performs are vast. Epithelium tissue may serve one or more function but as previously discussed the function depends on the activity of the cell types that are present. For that reason epithelium can have diverse functions. The major functions of epithelium include protecting underlying structures and acting as a barrier. For example it prevents the movement of many substances form the epithelium layer. Other functions include the passage of substances through epithelium. (Ross M. 2006) Epithelium allows for the movement of many substances, a clear example of this can be seen within the respiratory system. Oxygen and carbon dioxide are exchanged between air and blood by diffusion through epithelium within the lungs. Epithelium also has the ability to secrete substances. This is an important role as the epithelium present in the respiratory portion secretes mucous produced by goblet cells. The mucous is responsible for warming, moistening and filtering inspired air. (Gillison M. 1966) (Myers A. 2002)

Fig 1.3: Illustrates the different shapes and layers which characterize each specific tissue. Sourced: http://en.wikipedia.org/wiki/Image:Illu_epithelium.jpg
Many examples exist to display the role each type of epithelium plays in the functioning of the respiratory system, however, only three are discussed in further detail. Simple Squamous Epithelium is a single layer of thin, flat cells. Substances can easily pass easily through this thin layer of tissue and for this reason it is often found where diffusion or filtration take place. A clear example is found in the respiratory passages, which ends as small sacs called alveoli. The alveoli consist of simple squamous epithelium and allow for the exchange of air into the blood. Air is diffused into the body while carbon dioxide is diffused out. (Myers A. 2002) Another example of the function epithelium plays within the respiratory system is psuedostratified ciliated columnar epithelium, a special type of epithelium. Its name implies that it has a layered appearance when in actual fact it is not multi layered (psuedo meaning false). It is found lining the walls of the trachea and bronchial tubes, for this reason it is commonly referred to as respiratory epithelium. Its function is to remove foreign objects such as dust and bacteria that have been trapped in the mucus. (Ross M. 2006) (Gillison M. 1966) Another illustration of the function of epithelium is found within the pharynx, which is the ventricle leading to the larynx, which makes up most of the esophageus. Stratified simple squamous and cuboidal epithelium line the pharynx as a protective mechanism. Stratified epithelium is made up of more then one layer and for this reason is well adapted to withstand moderate abrasion. The purpose of this is to protect the lining of the throat when hot food or rough substances are consumed. (Ross M. 2006) (Seeley R. 2005) (Van De Graaff K. 2002)

Connective tissue is the most abundant type of tissue in the body. It is a dominant architectural structure within the respiratory system. Despite this, just like epithelium tissue only several types of connective tissue are present within the respiratory system. However unlike epithelium tissue, which consists of tightly fitted cells, connective tissue contains a larger matrix (intercellular material) then just cells. (Seeley R. 2005) This extracellular matrix is largely responsible for the function and characteristics of each type of connective tissue. The classification of connective tissues is named according to the arrangement and function of the matrix. (1. Loose or Areolar C.T 2. Dense regular C.T, 3. Dense irregular C.T 4. Elastic C.T 5. Reticular C.T 6. Adipose C.T 7. Cartilage 8. Bone Tissue 9. Blood, vascular tissue) (Seeley R. 2005) Connective tissue performs and plays a crucial role in the functioning of many body systems. These sub-divisions of connective tissue are illustrated in figure 1.4. Although not all of these functions are highlighted within the respiratory system some particular functions that are performed by connective tissue are, support, mobility, protection and storage.

Fig 1.4: Histological depiction of the different types of Connective tissue.
All pictures sourced from: University of Delaware Biological Sciences website.
http://www.udel.edu/biology/Wags/histopage/histopage.htm

It has been established that connective tissue plays numerous functions within the body and that not all connective tissues play a particular function within the respiratory system. Examples of connective tissues involved in achieving respiration are elastic connective tissues, which are mainly comprised of elastic fibres that are arranged irregularly. They are a particularly unique muscle, due to their ability to stretch to one and half times their original size and return back to their former size. (Van De Graaff K. 2002) In the case of the respiratory system this particularly important as this connective tissue allows for the lungs to be filled with air upon inhaling while snapping back to its original size upon exhaling. Hyaline cartilage provides another example of the function of connective tissue within the respiratory system. Also commonly called ‘gristle’, it is the most abundant cartilage present within the body. It occurs in places such as the larynx and trachea and acts as an architectural frame in the shaped of circular disc. As most cartilage and connective tissue it plays a supportive and protective role within the larynx and trachea. (Van De Graaff K. 2002) (Ross. M. 2006)

Muscular tissues are responsible for the movement of materials through the body, the movement of a body part in respect to another one to perform locomotion. The tissue is characterized by aggregates of specialized, elongated cells that are arranged for the purpose of contraction. This contraction is a result of myofilaments interacting with the muscle cells. There are two types of myofilaments (thick and thin) and they occupy the bulk of the cytoplasm that is otherwise known as sarcoplasm. The muscle cells contain large amounts of contractile filaments that are used for the single purpose of locomotion.
It is these contractile cells as well as appearance that are the basis of classification. Muscular tissues have two principal types of classification, striated muscle and smooth muscle. Striated muscles are further sub-classed into skeletal, visceral and cardiac.

Fig. 1.5: Depiction of the three types of muscle tissue while providing a brief summary of location and function.
Sourced: www.agen.ufl.edu/…/ lect/lect_19/lect_19.htm
Smooth muscle tissue is common throughout the body being present in many body systems. It can be seen in the respiratory system as the smooth muscle lines the walls of the respiratory ducts. It is also responsible for regulating the size of organs and for forcing fluid through tubes and arteries. The contraction of smooth muscle is controlled autonomically, which means it is involuntary and controlled by the nervous system. Smooth muscle fibres are long in appearance and consist of spindle shaped cells. These cells are usually grouped together in flattened sheets. It is smooth muscle that lines the oesophagus, which allows for swallowing to happen. (Gillison M. 1966) Skeletal Muscle and Visceral striated, which is morphologically identical, are as its name suggests muscle attached to bone. They are responsible for movement of the skeletal frame while also maintaining body posture and position. These muscles play vital roles in speech, breathing and swallowing. Unlike smooth muscles, which are controlled autonomically, skeletal and visceral muscles are controlled voluntarily. It is this ability to consciously move these muscles that allows for the act of swallowing food to occur. Skeletal and visceral muscles line most parts of the conducting portion of the respiratory system. For this reason it plays an important role in respiration as it regulates the flow of air through the lungs. (Van De Graaff K. 2002) (Ross. M. 2006)

The brain, spinal cord and nerves are all comprised of nervous tissue. Nervous tissue is the fourth major class of vertebrate tissue. The function of nervous tissue is to communicate between parts of the body. For example, the conscious control of skeletal muscles and the unconscious regulation of cardiac muscle are all a result of nerve tissue. (Seeley R. 2005) The tissue is composed of neurons, which transmit impulses, as well as neuroglia, which function to protect and nourish the neurons. Many of the functions that are performed by the human body are dependent on the ability of the nervous tissue cells to communicate between one another and the cells involved in specific function. One such function is the ability to control the air intake into the lungs. (Slomianka L. 2006) Nervous tissue is comprised of many varieties of nerve cells, all of which can be characterised by the axon and stem like part of the cell. It is the axon and stem like part of the cell that send action potential signals from one cell to the next. It is the human body’s ability to react to stimuli that allows for a response. Nerve tissues, which branch throughout the body are made up of specialized nerve cells known as neurons. Each neuron has the ability to be stimulated easily and can transmit impulses quickly. It is the body’s ability to transmit impulses rapidly, which allows for the process of respiration to take place. The nerve tissue present within the respiratory system allows for the gas exchange to occur within the alveoli. These constant impulses are what instruct the muscles within the larynx and trachea to contract and expand the oesophagus. (Slomianka L. 2006) (Van De Graaff K. 2002) (Ross. M. 2006)

Fig 1.6: Histological depiction of neurons with nervous tissue.
Sourced: www.okc.cc.ok.us/…/ Nervous_tissue.htm

Fig 1.7: Typical structure of a neuron
Sourced: http://training.seer.cancer.gov/module_anatomy/unit5_2_nerve_tissue.html

Having discussed the four basic tissues present within the human body while highlighting the particular tissue types present and their function within the respiratory system, the remainder of the essay aims to highlight each tissues involvement within the various components of the respiratory system while providing further explanation to their specific role within the system.

The conducting portion of the respiratory system consists of the passages (Nasal cavities, nasopharynx, larynx, trachea and paired main bronchi) that lead to the lungs where gas exchange occurs. Within the lungs the main bronchi branch extensively to the distributing bronchioles (bronchial tree). It is the bronchioles, which are the terminal part of the conducting portion. The respiratory portion refers to the components involved in gas exchange (Respiratory bronchioles, Alveolar ducts, Alveolar sacs and Alveoli). The intimate relationship present between the pulmonary capillaries and terminal respiratory units (Alveoli) is the structural basis for gas exchange within the lungs. (Ross M. 2006) (Seeley R. 2005) However before air reaches this terminal structure, air must be conditioned. This process of conditioning occurs in the conducting portion and includes warming, moistening and the removal of particles. Mucous and serous produced by the epithelium plays an important role in the conditioning process but also prevents the dehydration of the underlying epithelium. (Ross M. 2006) (Seeley R. 2005)

Fig. 1.8: Details the location and names of the various components that make up the conducting portion.
Sourced: http://www.nanomedicine.com/NMI/Figures/8.11.jpg
The term nose refers to the visible structure that forms a prominent feature of the face. Most of the nose is composed of cartilage however the bridge is made up of bone. The nasal cavity consists of two paired chambers, each communicating anteriorly with the outside environment. The chamber can be divided into three sections, vestibule, respiratory segment and olfactory segment. The vestibule is the section of the nasal cavity, which communicates with the outside environment. It is lined with stratified squamous epithelium consisting of stiff hairs, which helps to trap foreign particles. The end of the vestibule is visually recognised by the transition of stratified squamous epithelium into pseudostratified epithelium, which is a clear characteristic of the respiratory segment. The respiratory segment is lined with ciliated, pseudostratified columnar epithelium, which serves to warm, moisten and cleanse the inspired air. The medial wall of the respiratory segment is smooth however the lateral walls are inverted in shelf like protrusions. These protrusions otherwise known as turbinates or conchae perform the dual role of causing turbulence in airflow to allow better conditioning while also increasing surface area. (Van De Graaff K. 2002) The ciliated, pseudostratified columnar epithelium consists of several cells, which highlight the epitheliums function. They are ciliated cells, which house cilia, goblet cells, which are responsible for mucous production, brush cells, small granule cells, which are similar to basal cell, however contain secretory granules and basal cells, which contain stem cells, these are the cell that give raise to other cells. (Ross M. 2006) (Seeley R. 2005) The epithelium present within the respiratory segment constitutes most of the epithelium lining the conductive portion of the respiratory system. Olfactory segment the final section of the nasal cavity and is lined with a special olfactory mucosa. This connective tissue contains numerous blood and lymphatic vessels and just like epithelium in the respiratory segment the olfactory epithelium is also pseudostratifeid, the only difference is the cells. The cells involved are responsible for such functions as sensory stimulation, physical support and maintenance. (Myers A. 2002) (Campbell N. 2006)

The paranasal sinuses are a further extension of the respiratory segment thus they are lined with respiratory epithelium. The sinuses are named accordingly to the bones in which they are found, thus, they are the maxillary, frontal, sphenoidal and ethmoidal sinuses. (Slomianka L. 2006) Each communicated via drainage ducts with the nasal cavity. The mucosal surface of the sinuses is thin, ciliated, pseudo-stratified epithelium containing numerous goblet cells. They are responsible for some sound resonance, but more importantly they function to decrease weight of the skull while providing structural strength. (Van De Graaff K. 2002) (Ross M. 2006)

The Pharynx is a funnel-shaped organ, which connects the nasal and oral cavities to the larynx and esophageus. It serves numerous roles by acting as a passageway for both air and food while also acting as a resonating chamber for speech. The supporting walls of the pharynx are composed of skeletal muscle. The pharynx can be further broken down regionally into three sections, nasopharynx, oropharynx and laryngopharynx. It is divided on the basis of location and function. Nasopharynx serves only as a passageway for air, yet, the oropharynx, which is the middle portion, swallows food, fluid and inhales air. The laryngopharynx is the lowermost portion of the pharynx and it is at this point that the digestive and respiratory systems become distinct. Swallowing of food and fluid are directed down the esophageus while air is directed anteriorly into the larynx. (Slomianka L. 2006) (Zhang S. 1999) (Johnson D.R. unknown)

The Larynx, more commonly known as the voice box, is the passageway between the oropharynx and the trachea. This tubular complex consists of irregular shaped plates of hyaline and elastic cartilage. It is an important section of the respiratory system as not only does it serve as a conduit for air but the larynx also serves as the origin for speech. More importantly the larynx stops both food and fluid from entering the trachea and lungs. Stratified squamous and ciliated psuedo-stratified columnar epithelium line the larynx, which serves to protect the mucosa from abrasion caused by rapid moving air. The remained of the larynx is lined with the psuedo-stratified columnar epithelium, which just like in the respiratory tract perform the same function. The connective tissue, which lines the larynx, contains mucoserous glands, which again help prevent abrasion of the epithelia tissue. (Ross M. 2006) (Van De Graaff K. 2002) (Slomianka L. 2006)

The trachea also commonly called the windpipe is a short, flexible tubular organ, which also assists in the conditioning of inspired air. It extends from the larynx to the two main bronchi. The wall of the trachea consists of four definable layers, which are known as the mucosa, sub-mucosa, cartilaginous layer and the adventitia. The mucosa is composed of ciliated pseudo-stratified epithelium and elastic fibres, slightly denser connective tissue comprises the submucosa, C shaped hyaline cartilage make up the cartilaginous layer, while the adventitia is composed mainly of connective tissues, which helps bind the trachea to surround structure. The cartilage ensures that the airway will always remain open while the epithelium again provides the same protection against dust or other particles. Medial to the lungs the trachea ends by splitting in two to form the right and left bronchi. (Van De Graaff K. 2002) (Ross M. 2006)

Fig. 1.9 Illustrates the structure of the lungs. Highlight the position of the trachea , bronchi and bronchioles.
Sourced: www.virtualsciencefair.org/. ../whatarelungs.html
The bronchial tree is so named because of it resembles to a tree, it is composed of several respiratory tubes that branch off into progressively smaller and smaller tubes, which extend into the lungs. Each bronchus is composed of hyaline cartilage rings, which are located within the surrounding walls. They make sure that the bronchi tubes remain open. Initially the bronchi have the same histological feature as the trachea. It is not until the bronchi enter the lungs do the structure of the bronchial wall change. These cartilage rings are replaced with cartilage plates. The branching of the bronchi continues until the airway reaches a diameter of about 1mm. (Zhang S. 1999) It is from this point that the cartilage plates disappear and the branch is now designated a bronchiole. There is little cartilage present within bronchioles instead thick smooth muscle encircles and is present within the walls. The beginning of the bronchioles is also visual represented by the transition of pseudo-stratified columnar epithelium to simple cuboidal epithelium. Respiratory bronchioles constitute an intermediary zone in the respiratory system because they play are role in both air conduction and gas exchange. (Van De Graaff K. 2002) The conduction portion ends at the terminal bronchioles while the respiratory portion beings at the respiratory bronchioles. It is the respiratory bronchioles that lead into the alveolar ducts and then into the alveolar sacs. (Zhang S. 1999)

Fig. 1.10: Depiction of the Alveolar ducts and alveoli. Also illustrated is the smooth muscle raped around the trachea as well as the connective tissue surrounding the alveoli.
Sourced: http://academic.kellogg.cc.mi.us/herbrandsonc/bio201_McKinley/Respiratory%20System.htm

Alveoli are the site where gas exchange actually takes place and is the terminal air space of the respiratory system. The surface area that is available for gas exchange is increased by the lung alveoli. The alveoli are surround by capillaries, which are responsible for bringing blood into close proximity to the inhaled air. This allows for the blood to be oxygenised. Alveolar epithelium plays a vital role in the gas exchange process. It is composed of two types of alveolar cells. (Zhang S. 1999) Type one are extremely thin squamous cells, which join to one another and other cells of the alveolar epithelium to create an effective barrier which prevents oxygen from leaving the lungs. Type two is secretory cell, comprised of cuboidal cells that produce a surface-active agent called surfactant. This surfactant reduces the air tension on the epithelium tissue. The alveolar septum refers to the air space present between the alveolar and capillaries. A thin air blood barrier is produce so that gas may be exchanged. (Van De Graaff K. 2002) (Ross M. 2006) (Zhang S. 1999)

Fig.1.11: Closer look at the alveoli while also depicting the main components.
Sourced: http://academic.kellogg.cc.mi.us/herbrandsonc/bio201_McKinley/Respiratory%20System.htm

It is the pulmonary circulation produced by the heart, which supplies the capillaries of the alveolar septum. The oxygenated blood is collected by the pulmonary venous capillaries then pumped back to the heart. From there the oxygenated blood is pumped around the body thus the process of respiratory system is completed. It is a cycle that is continually happening within us whether we are sleeping or awake. Breathing is an important part of everyday life, which involves the collaboration of many tissues to make it function. (Campbell N. 2006) (Zhang S. 1999) (Ross M. 2006)

Bibliography

Campbell N. A, Reece J.B, Meyers N. 2006. Biology. 7th Edit. Pearson Education Australia. Frenchs Forest, NSW, Australia.

Gillison M. 1966. A histology of the Body Tissues: with consideration of their functions. 2nd Edit. E. & S. Livingstone LTD. Edinburgh and London.

Heffner L.J. 2001. Human Reproduction at a Glance. Marston Book Service Ltd, Abingdon, Oxon, England

Hlastala, M.P, Berger, A.J. 1996 Physiology of respiration. New York : Oxford University Press, 1996.

Johnson D.R. unknown. Introductory Anatomy: Respiratory System. Faculty of Biological Sciences, University of Leeds, England
http://www.leeds.ac.uk/chb/lectures/anatomy7.html

Lawrence E. 2005. Henderson’s Dictionary of Biology. 13th Edit. Pearson Education Australia, Frenchs Forest, NSW, Australia.

Myers A. Mcgowan P, Jerffries A, Turley A. 2002. Respiratory System: A crash course. Elsevier Mosby, Philadelphia.

Ross M.H, Pawlina W. 2006. Histology: A Text and Atlas. Lippincoot Williams & Wilkins, Philadelphia.

Seeley R.R, Stephens T.D, Tate P. 2005. Essentials of Anatomy and Physiology. Mcgraw-Hill Higher Education, Avenue of the Americans, New York, NY

Slomianka L. 2006. Blue Histology: Respiratory System. School of Anatomy and Human biology: The University of Western Australia
http://www.lab.anhb.uwa.edu.au/mb140/

Van De Graaff K.M. 2002. Human Anatomy. 6th Edit. McGraw-Hill Higher Education, Avenue of the Americans, New York, NY

Atlas. Zhang S. 1999. An atlas of histology. Springer Date, New York.
Select a body system of interest to you. Describe the various tissues that comprise the system, their key features and their role in the functioning of this body system. You can use diagrams/pictures to make your points

Whether it is sleeping, talking, walking or running all these activities require one important factor, the ability to breath. From the first breath after birth to our very last breathe taken, the rate and depth of respiration is unconsciously monitored and matched to the body’s activity. Although the human body has the ability to stop breathing, within a few minutes it will require to breathe again. Breathing is so highly characterised with life and living that apart from our pulse it is one of the first things checked to determine whether a person is alive. (Seeley R. 2005) The term respiration, otherwise commonly known as breathing, refers to three separate, yet very related principle functions. These functions are ventilation, oxygen utilisation and gas exchange (respiration). Briefly, the latter function allows for oxygen from air to enter the blood while allowing carbon dioxide (CO2), produced by cells, to leave the body. Respiration is a necessary body system because all living cells within the body require oxygen. The respiratory system performs this function and is solely responsible for producing the body’s oxygen requirements. (Ross M. 2006) (Myers A. 2002)

The major structures that make up the respiratory system are the nasal cavity, pharynx, (Conducting portion or upper respiratory system) larynx and trachea, the bronchi, bronchioles, and the pulmonary alveoli within the lungs (Respiratory portion or lower respiratory system). These structures all work together to perform four basic functions. Providing oxygen to the blood stream while removing carbon dioxide, enabling sound production or vocalization, assisting in abdominal compression, required during urination, defecation and childbirth. It allows for protective and reflexive breathing movements, the ability to cough and sneeze. (Myers A. 2002) The respiratory system is a highly intricate system that provides human beings with many abilities. It requires the use of many cells, tissues and other body systems working simultaneously together. (Hlastala, M.P. 1996) These features are highlighted within figure 1.1.
Fig 1.1: Highlights the main component of the respiratory system.
Sourced: http://emptynosesyndrome.org/pics/image001.gif
The purpose of this essay will be to outline further the key functions, role and mechanisms of the respiratory system, while highlighting the various tissues that comprise of the system. Additionally, these various tissues types will be discussed individually, with emphasis placed on their key features and their role in the functioning of this body system. Tissue types that will be discussed are Epithelium Tissue, Muscular Tissue, Nervous tissue and Connective Tissue. This will further illustrate the role each tissue plays within the system while highlighting the inner workings of the respiratory system itself.

In order to understand the function, role and mechanics required for performing respiration one must first understand what tissues are and the different types of tissues that the system is comprised of. It is these tissues that in turn allow for respiration to occur. Tissues are aggregations of similar cells and cell products that work together to perform specific functions. (Lawrence E. 2006) Although it is understood that cells are the basic functional units of the body, it can be argued that tissues are the functional units of the body. (Seeley R. 2005) It is the collaboration of all the individual cells present within tissues that are responsible for maintaining body function. It is a cells ability to communicate which allows for this collaboration to occur. (Campbell N. 2006) Understanding tissue mechanics highlights that it is the cells, which make up the tissue that provide their function and role. (Ross M. 2006) The human body is comprised of four basic tissues, Epithelium Tissue (Epithelial tissue), which covers body surfaces, lines body cavities, ducts and forms glands, Connective Tissue, which underlies, supports, binds and protects the other basic tissues structurally and functionally, Muscular Tissue which contracts to produce movement while Nervous Tissue receives and transmits information received from outside and inside the body in the form of nerve impulses. (Ross M. 2006) (Myers A. 2002)

Fig 2.2: Illustrates the basic differences between each type of tissue.
Sourced: http://health.allrefer.com/pictures-images/tissue-types.html
These four major tissues are broken down further on the basis of specific characteristics. In the case of epithelium, the number of cell layers and shape of the surface result in the terminology refecting their structure, for this reason Epithelium tissue is subdivided into the following classifications, cell shapes included squamous, cuboidal and columnar while layers are classified by simple (single layer) or stratified (multiple layers). (Ross M. 2006) (Lawrence E. 2006) (Seeley R. 2005). Connective tissue (C.T) is primarily classified accordingly to it composition and organization, and is characterised by the amount of extracellular material that separates cells from one another. This extracellular material is comprised of three major components, protein fibres, ground substances and fluid. For this reason connective tissue is subdivided into Areolar C.T, Adipose Tissue, Dense regular C.T, Dense irregular C.T, Elastic C.T, Reticular C.T and Cartilage (Hyaline, Fibro and Elastic). While muscular and nervous tissue is based on their function rather then their structure. Muscular tissue is unique in this way as it has the ability to contract and relax which makes movement possible. This movement is achieved through the shortening of muscle fibres in response to a stimulus. There are four types of muscular tissue, Skeletal, Visceral striated, Cardiac and Smooth muscular tissue. Smooth muscle tissue, skeletal and visceral striated muscle is the predominant muscle type present within the respiratory system and for this reason will be the main muscular tissues focused on. (Gillison M. 1966) (Myers A. 2002) Nervous tissue is composed of neurons, these neurons respond to stimuli and conduct impulses to and from all body organs. There are three principal components in nervous tissue, cell body, dendrites and axons. (Myers A. 2002) These tissues play important roles structurally and functionally throughout the body. Although not all subunits of each basic tissue play a direct role in respiration they are equally important within the body. The following paragraphs look to highlight the roles and functions of each subdivision involved in the respiratory system in closer detail.

As previously discussed Epithelium tissue is classed according to shape and layers thus only structure and not function is described. It is by describing the cell number and cell shape that the various configurations can be classified. Thus epithelium tissue can be divided into eight sub-types of epithelium. These are as follows, Simple squamous, simple cuboidal, simple columnar, pseudostratified, stratified squamous, stratified cuboidal, stratified columnar and transitional. (Ross M. 2006) (Van De Graaff K. 2002). Each type of epithelium can be seen to play a role within the respiratory system thus the functions it performs are vast. Epithelium tissue may serve one or more function but as previously discussed the function depends on the activity of the cell types that are present. For that reason epithelium can have diverse functions. The major functions of epithelium include protecting underlying structures and acting as a barrier. For example it prevents the movement of many substances form the epithelium layer. Other functions include the passage of substances through epithelium. (Ross M. 2006) Epithelium allows for the movement of many substances, a clear example of this can be seen within the respiratory system. Oxygen and carbon dioxide are exchanged between air and blood by diffusion through epithelium within the lungs. Epithelium also has the ability to secrete substances. This is an important role as the epithelium present in the respiratory portion secretes mucous produced by goblet cells. The mucous is responsible for warming, moistening and filtering inspired air. (Gillison M. 1966) (Myers A. 2002)

Fig 1.3: Illustrates the different shapes and layers which characterize each specific tissue. Sourced: http://en.wikipedia.org/wiki/Image:Illu_epithelium.jpg
Many examples exist to display the role each type of epithelium plays in the functioning of the respiratory system, however, only three are discussed in further detail. Simple Squamous Epithelium is a single layer of thin, flat cells. Substances can easily pass easily through this thin layer of tissue and for this reason it is often found where diffusion or filtration take place. A clear example is found in the respiratory passages, which ends as small sacs called alveoli. The alveoli consist of simple squamous epithelium and allow for the exchange of air into the blood. Air is diffused into the body while carbon dioxide is diffused out. (Myers A. 2002) Another example of the function epithelium plays within the respiratory system is psuedostratified ciliated columnar epithelium, a special type of epithelium. Its name implies that it has a layered appearance when in actual fact it is not multi layered (psuedo meaning false). It is found lining the walls of the trachea and bronchial tubes, for this reason it is commonly referred to as respiratory epithelium. Its function is to remove foreign objects such as dust and bacteria that have been trapped in the mucus. (Ross M. 2006) (Gillison M. 1966) Another illustration of the function of epithelium is found within the pharynx, which is the ventricle leading to the larynx, which makes up most of the esophageus. Stratified simple squamous and cuboidal epithelium line the pharynx as a protective mechanism. Stratified epithelium is made up of more then one layer and for this reason is well adapted to withstand moderate abrasion. The purpose of this is to protect the lining of the throat when hot food or rough substances are consumed. (Ross M. 2006) (Seeley R. 2005) (Van De Graaff K. 2002)

Connective tissue is the most abundant type of tissue in the body. It is a dominant architectural structure within the respiratory system. Despite this, just like epithelium tissue only several types of connective tissue are present within the respiratory system. However unlike epithelium tissue, which consists of tightly fitted cells, connective tissue contains a larger matrix (intercellular material) then just cells. (Seeley R. 2005) This extracellular matrix is largely responsible for the function and characteristics of each type of connective tissue. The classification of connective tissues is named according to the arrangement and function of the matrix. (1. Loose or Areolar C.T 2. Dense regular C.T, 3. Dense irregular C.T 4. Elastic C.T 5. Reticular C.T 6. Adipose C.T 7. Cartilage 8. Bone Tissue 9. Blood, vascular tissue) (Seeley R. 2005) Connective tissue performs and plays a crucial role in the functioning of many body systems. These sub-divisions of connective tissue are illustrated in figure 1.4. Although not all of these functions are highlighted within the respiratory system some particular functions that are performed by connective tissue are, support, mobility, protection and storage.

Fig 1.4: Histological depiction of the different types of Connective tissue.
All pictures sourced from: University of Delaware Biological Sciences website.
http://www.udel.edu/biology/Wags/histopage/histopage.htm

It has been established that connective tissue plays numerous functions within the body and that not all connective tissues play a particular function within the respiratory system. Examples of connective tissues involved in achieving respiration are elastic connective tissues, which are mainly comprised of elastic fibres that are arranged irregularly. They are a particularly unique muscle, due to their ability to stretch to one and half times their original size and return back to their former size. (Van De Graaff K. 2002) In the case of the respiratory system this particularly important as this connective tissue allows for the lungs to be filled with air upon inhaling while snapping back to its original size upon exhaling. Hyaline cartilage provides another example of the function of connective tissue within the respiratory system. Also commonly called ‘gristle’, it is the most abundant cartilage present within the body. It occurs in places such as the larynx and trachea and acts as an architectural frame in the shaped of circular disc. As most cartilage and connective tissue it plays a supportive and protective role within the larynx and trachea. (Van De Graaff K. 2002) (Ross. M. 2006)

Muscular tissues are responsible for the movement of materials through the body, the movement of a body part in respect to another one to perform locomotion. The tissue is characterized by aggregates of specialized, elongated cells that are arranged for the purpose of contraction. This contraction is a result of myofilaments interacting with the muscle cells. There are two types of myofilaments (thick and thin) and they occupy the bulk of the cytoplasm that is otherwise known as sarcoplasm. The muscle cells contain large amounts of contractile filaments that are used for the single purpose of locomotion.
It is these contractile cells as well as appearance that are the basis of classification. Muscular tissues have two principal types of classification, striated muscle and smooth muscle. Striated muscles are further sub-classed into skeletal, visceral and cardiac.

Fig. 1.5: Depiction of the three types of muscle tissue while providing a brief summary of location and function.
Sourced: www.agen.ufl.edu/…/ lect/lect_19/lect_19.htm
Smooth muscle tissue is common throughout the body being present in many body systems. It can be seen in the respiratory system as the smooth muscle lines the walls of the respiratory ducts. It is also responsible for regulating the size of organs and for forcing fluid through tubes and arteries. The contraction of smooth muscle is controlled autonomically, which means it is involuntary and controlled by the nervous system. Smooth muscle fibres are long in appearance and consist of spindle shaped cells. These cells are usually grouped together in flattened sheets. It is smooth muscle that lines the oesophagus, which allows for swallowing to happen. (Gillison M. 1966) Skeletal Muscle and Visceral striated, which is morphologically identical, are as its name suggests muscle attached to bone. They are responsible for movement of the skeletal frame while also maintaining body posture and position. These muscles play vital roles in speech, breathing and swallowing. Unlike smooth muscles, which are controlled autonomically, skeletal and visceral muscles are controlled voluntarily. It is this ability to consciously move these muscles that allows for the act of swallowing food to occur. Skeletal and visceral muscles line most parts of the conducting portion of the respiratory system. For this reason it plays an important role in respiration as it regulates the flow of air through the lungs. (Van De Graaff K. 2002) (Ross. M. 2006)

The brain, spinal cord and nerves are all comprised of nervous tissue. Nervous tissue is the fourth major class of vertebrate tissue. The function of nervous tissue is to communicate between parts of the body. For example, the conscious control of skeletal muscles and the unconscious regulation of cardiac muscle are all a result of nerve tissue. (Seeley R. 2005) The tissue is composed of neurons, which transmit impulses, as well as neuroglia, which function to protect and nourish the neurons. Many of the functions that are performed by the human body are dependent on the ability of the nervous tissue cells to communicate between one another and the cells involved in specific function. One such function is the ability to control the air intake into the lungs. (Slomianka L. 2006) Nervous tissue is comprised of many varieties of nerve cells, all of which can be characterised by the axon and stem like part of the cell. It is the axon and stem like part of the cell that send action potential signals from one cell to the next. It is the human body’s ability to react to stimuli that allows for a response. Nerve tissues, which branch throughout the body are made up of specialized nerve cells known as neurons. Each neuron has the ability to be stimulated easily and can transmit impulses quickly. It is the body’s ability to transmit impulses rapidly, which allows for the process of respiration to take place. The nerve tissue present within the respiratory system allows for the gas exchange to occur within the alveoli. These constant impulses are what instruct the muscles within the larynx and trachea to contract and expand the oesophagus. (Slomianka L. 2006) (Van De Graaff K. 2002) (Ross. M. 2006)

Fig 1.6: Histological depiction of neurons with nervous tissue.
Sourced: www.okc.cc.ok.us/…/ Nervous_tissue.htm

Fig 1.7: Typical structure of a neuron
Sourced: http://training.seer.cancer.gov/module_anatomy/unit5_2_nerve_tissue.html

Having discussed the four basic tissues present within the human body while highlighting the particular tissue types present and their function within the respiratory system, the remainder of the essay aims to highlight each tissues involvement within the various components of the respiratory system while providing further explanation to their specific role within the system.

The conducting portion of the respiratory system consists of the passages (Nasal cavities, nasopharynx, larynx, trachea and paired main bronchi) that lead to the lungs where gas exchange occurs. Within the lungs the main bronchi branch extensively to the distributing bronchioles (bronchial tree). It is the bronchioles, which are the terminal part of the conducting portion. The respiratory portion refers to the components involved in gas exchange (Respiratory bronchioles, Alveolar ducts, Alveolar sacs and Alveoli). The intimate relationship present between the pulmonary capillaries and terminal respiratory units (Alveoli) is the structural basis for gas exchange within the lungs. (Ross M. 2006) (Seeley R. 2005) However before air reaches this terminal structure, air must be conditioned. This process of conditioning occurs in the conducting portion and includes warming, moistening and the removal of particles. Mucous and serous produced by the epithelium plays an important role in the conditioning process but also prevents the dehydration of the underlying epithelium. (Ross M. 2006) (Seeley R. 2005)

Fig. 1.8: Details the location and names of the various components that make up the conducting portion.
Sourced: http://www.nanomedicine.com/NMI/Figures/8.11.jpg
The term nose refers to the visible structure that forms a prominent feature of the face. Most of the nose is composed of cartilage however the bridge is made up of bone. The nasal cavity consists of two paired chambers, each communicating anteriorly with the outside environment. The chamber can be divided into three sections, vestibule, respiratory segment and olfactory segment. The vestibule is the section of the nasal cavity, which communicates with the outside environment. It is lined with stratified squamous epithelium consisting of stiff hairs, which helps to trap foreign particles. The end of the vestibule is visually recognised by the transition of stratified squamous epithelium into pseudostratified epithelium, which is a clear characteristic of the respiratory segment. The respiratory segment is lined with ciliated, pseudostratified columnar epithelium, which serves to warm, moisten and cleanse the inspired air. The medial wall of the respiratory segment is smooth however the lateral walls are inverted in shelf like protrusions. These protrusions otherwise known as turbinates or conchae perform the dual role of causing turbulence in airflow to allow better conditioning while also increasing surface area. (Van De Graaff K. 2002) The ciliated, pseudostratified columnar epithelium consists of several cells, which highlight the epitheliums function. They are ciliated cells, which house cilia, goblet cells, which are responsible for mucous production, brush cells, small granule cells, which are similar to basal cell, however contain secretory granules and basal cells, which contain stem cells, these are the cell that give raise to other cells. (Ross M. 2006) (Seeley R. 2005) The epithelium present within the respiratory segment constitutes most of the epithelium lining the conductive portion of the respiratory system. Olfactory segment the final section of the nasal cavity and is lined with a special olfactory mucosa. This connective tissue contains numerous blood and lymphatic vessels and just like epithelium in the respiratory segment the olfactory epithelium is also pseudostratifeid, the only difference is the cells. The cells involved are responsible for such functions as sensory stimulation, physical support and maintenance. (Myers A. 2002) (Campbell N. 2006)

The paranasal sinuses are a further extension of the respiratory segment thus they are lined with respiratory epithelium. The sinuses are named accordingly to the bones in which they are found, thus, they are the maxillary, frontal, sphenoidal and ethmoidal sinuses. (Slomianka L. 2006) Each communicated via drainage ducts with the nasal cavity. The mucosal surface of the sinuses is thin, ciliated, pseudo-stratified epithelium containing numerous goblet cells. They are responsible for some sound resonance, but more importantly they function to decrease weight of the skull while providing structural strength. (Van De Graaff K. 2002) (Ross M. 2006)

The Pharynx is a funnel-shaped organ, which connects the nasal and oral cavities to the larynx and esophageus. It serves numerous roles by acting as a passageway for both air and food while also acting as a resonating chamber for speech. The supporting walls of the pharynx are composed of skeletal muscle. The pharynx can be further broken down regionally into three sections, nasopharynx, oropharynx and laryngopharynx. It is divided on the basis of location and function. Nasopharynx serves only as a passageway for air, yet, the oropharynx, which is the middle portion, swallows food, fluid and inhales air. The laryngopharynx is the lowermost portion of the pharynx and it is at this point that the digestive and respiratory systems become distinct. Swallowing of food and fluid are directed down the esophageus while air is directed anteriorly into the larynx. (Slomianka L. 2006) (Zhang S. 1999) (Johnson D.R. unknown)

The Larynx, more commonly known as the voice box, is the passageway between the oropharynx and the trachea. This tubular complex consists of irregular shaped plates of hyaline and elastic cartilage. It is an important section of the respiratory system as not only does it serve as a conduit for air but the larynx also serves as the origin for speech. More importantly the larynx stops both food and fluid from entering the trachea and lungs. Stratified squamous and ciliated psuedo-stratified columnar epithelium line the larynx, which serves to protect the mucosa from abrasion caused by rapid moving air. The remained of the larynx is lined with the psuedo-stratified columnar epithelium, which just like in the respiratory tract perform the same function. The connective tissue, which lines the larynx, contains mucoserous glands, which again help prevent abrasion of the epithelia tissue. (Ross M. 2006) (Van De Graaff K. 2002) (Slomianka L. 2006)

The trachea also commonly called the windpipe is a short, flexible tubular organ, which also assists in the conditioning of inspired air. It extends from the larynx to the two main bronchi. The wall of the trachea consists of four definable layers, which are known as the mucosa, sub-mucosa, cartilaginous layer and the adventitia. The mucosa is composed of ciliated pseudo-stratified epithelium and elastic fibres, slightly denser connective tissue comprises the submucosa, C shaped hyaline cartilage make up the cartilaginous layer, while the adventitia is composed mainly of connective tissues, which helps bind the trachea to surround structure. The cartilage ensures that the airway will always remain open while the epithelium again provides the same protection against dust or other particles. Medial to the lungs the trachea ends by splitting in two to form the right and left bronchi. (Van De Graaff K. 2002) (Ross M. 2006)

Fig. 1.9 Illustrates the structure of the lungs. Highlight the position of the trachea , bronchi and bronchioles.
Sourced: www.virtualsciencefair.org/. ../whatarelungs.html
The bronchial tree is so named because of it resembles to a tree, it is composed of several respiratory tubes that branch off into progressively smaller and smaller tubes, which extend into the lungs. Each bronchus is composed of hyaline cartilage rings, which are located within the surrounding walls. They make sure that the bronchi tubes remain open. Initially the bronchi have the same histological feature as the trachea. It is not until the bronchi enter the lungs do the structure of the bronchial wall change. These cartilage rings are replaced with cartilage plates. The branching of the bronchi continues until the airway reaches a diameter of about 1mm. (Zhang S. 1999) It is from this point that the cartilage plates disappear and the branch is now designated a bronchiole. There is little cartilage present within bronchioles instead thick smooth muscle encircles and is present within the walls. The beginning of the bronchioles is also visual represented by the transition of pseudo-stratified columnar epithelium to simple cuboidal epithelium. Respiratory bronchioles constitute an intermediary zone in the respiratory system because they play are role in both air conduction and gas exchange. (Van De Graaff K. 2002) The conduction portion ends at the terminal bronchioles while the respiratory portion beings at the respiratory bronchioles. It is the respiratory bronchioles that lead into the alveolar ducts and then into the alveolar sacs. (Zhang S. 1999)

Fig. 1.10: Depiction of the Alveolar ducts and alveoli. Also illustrated is the smooth muscle raped around the trachea as well as the connective tissue surrounding the alveoli.
Sourced: http://academic.kellogg.cc.mi.us/herbrandsonc/bio201_McKinley/Respiratory%20System.htm

Alveoli are the site where gas exchange actually takes place and is the terminal air space of the respiratory system. The surface area that is available for gas exchange is increased by the lung alveoli. The alveoli are surround by capillaries, which are responsible for bringing blood into close proximity to the inhaled air. This allows for the blood to be oxygenised. Alveolar epithelium plays a vital role in the gas exchange process. It is composed of two types of alveolar cells. (Zhang S. 1999) Type one are extremely thin squamous cells, which join to one another and other cells of the alveolar epithelium to create an effective barrier which prevents oxygen from leaving the lungs. Type two is secretory cell, comprised of cuboidal cells that produce a surface-active agent called surfactant. This surfactant reduces the air tension on the epithelium tissue. The alveolar septum refers to the air space present between the alveolar and capillaries. A thin air blood barrier is produce so that gas may be exchanged. (Van De Graaff K. 2002) (Ross M. 2006) (Zhang S. 1999)

Fig.1.11: Closer look at the alveoli while also depicting the main components.
Sourced: http://academic.kellogg.cc.mi.us/herbrandsonc/bio201_McKinley/Respiratory%20System.htm

It is the pulmonary circulation produced by the heart, which supplies the capillaries of the alveolar septum. The oxygenated blood is collected by the pulmonary venous capillaries then pumped back to the heart. From there the oxygenated blood is pumped around the body thus the process of respiratory system is completed. It is a cycle that is continually happening within us whether we are sleeping or awake. Breathing is an important part of everyday life, which involves the collaboration of many tissues to make it function. (Campbell N. 2006) (Zhang S. 1999) (Ross M. 2006)

Bibliography

Campbell N. A, Reece J.B, Meyers N. 2006. Biology. 7th Edit. Pearson Education Australia. Frenchs Forest, NSW, Australia.

Gillison M. 1966. A histology of the Body Tissues: with consideration of their functions. 2nd Edit. E. & S. Livingstone LTD. Edinburgh and London.

Heffner L.J. 2001. Human Reproduction at a Glance. Marston Book Service Ltd, Abingdon, Oxon, England

Hlastala, M.P, Berger, A.J. 1996 Physiology of respiration. New York : Oxford University Press, 1996.

Johnson D.R. unknown. Introductory Anatomy: Respiratory System. Faculty of Biological Sciences, University of Leeds, England
http://www.leeds.ac.uk/chb/lectures/anatomy7.html

Lawrence E. 2005. Henderson’s Dictionary of Biology. 13th Edit. Pearson Education Australia, Frenchs Forest, NSW, Australia.

Myers A. Mcgowan P, Jerffries A, Turley A. 2002. Respiratory System: A crash course. Elsevier Mosby, Philadelphia.

Ross M.H, Pawlina W. 2006. Histology: A Text and Atlas. Lippincoot Williams & Wilkins, Philadelphia.

Seeley R.R, Stephens T.D, Tate P. 2005. Essentials of Anatomy and Physiology. Mcgraw-Hill Higher Education, Avenue of the Americans, New York, NY

Slomianka L. 2006. Blue Histology: Respiratory System. School of Anatomy and Human biology: The University of Western Australia
http://www.lab.anhb.uwa.edu.au/mb140/

Van De Graaff K.M. 2002. Human Anatomy. 6th Edit. McGraw-Hill Higher Education, Avenue of the Americans, New York, NY

Atlas. Zhang S. 1999. An atlas of histology. Springer Date, New York.

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Ever since I was a young kid I have always been interested with aircraft. I was so curious of how airplane's fly. I remember taking my toys apart to see how it works. As a kid I wanted to go to the airport to watch the airplanes land and fly and pondered how this happens. Other kids wanted to go to the amusement places. As I grew older I became more and more interested in aircraft and the technology behind it. I always involved myself with aviation early on. I read books and magazines on aviation, took museum tours, built model airplanes. When I was younger my father would take me to aircraft repair facilities where I would watch in great fascination. In my teens, went up to the military bases and befriended many soldiers involved with aircraft and asked them numerous questions. I got to meet many aeronautics engineers and borrowed their old textbooks and read them till the wee hours of the morning. As technology improved with information superhighway, I logged on the web. Stayed up for hours and hours searching through web pages and web pages of information about aircraft and technology. I started my elementary school in the Philippines, then we moved to U.S. and continued my high school education and graduated. Enrolled at the CCSF to pursue my college education and now I am in the 2nd year in CCSF taking aeronautics. My goal now is to obtain my AS degree from the City College of San Francisco (CCSF) so I can transfer to a University and get a Bachelors degree and to continue for my Masters degree in Aeronautics Engineering. I will strive hard to reach the peak level of my career which is a Professor and hopefully to be an aeronautic professor so...

Circus Circus Enterprises Case Studies

Executive Summary: Circus Circus Enterprises is a leader and will continue to be in the gaming industry. In recent years, they have seen a decline in profit and revenue; management tends to blame the decrease on continuing disruptions from remodeling, expansion, and increased competition. Consequently, Circus has reported decreases in its net income for 1997 and 1998 and management believes this trend will continue as competition heightens. Currently the company is involved in several joint ventures, its brand of casino entertainment has traditionally catered to the low rollers and family vacationers through its theme park. Circus should continue to expand its existing operations into new market segments. This shift will allow them to attract the up scale gambler. Overview Circus Circus Enterprises, Inc founded in 1974 is in the business of entertainment, with its core strength in casino gambling. The company?s asset base, operating cash flow, profit margin, multiple markets and customers, rank it as one of the gaming industry leaders. Partners William G. Bennett an aggressive cost cutter and William N. Pennington purchased Circus Circus in 1974 as a small and unprofitable casino. It went public in 1983, from 1993 to 1997; the average return on capital invested was 16.5%. Circus Circus operates several properties in Las Vegas, Reno, Laughlin, and one in Mississippi, as well as 50% ownership in three other casinos and a theme park. On January 31,1998 Circus reported net income of 89.9 million and revenues of 1.35 billion, this is a down from 100 million on 1.3 billion in 1997. Management sees this decline in revenue due to the rapid and extensive expansion and the increased competition that Circus is facing. Well established in the casino gaming industry the corporation has its focus in the entertainment business and has particularly a popular theme resort concept....

Effect Of Civil War On American Economy

The Economies of the North and South, 1861-1865 In 1861, a great war in American history began. It was a civil war between the north and south that was by no means civil. This war would have great repercussions upon the economy of this country and the states within it. The American Civil War began with secession, creating a divided union of sorts, and sparked an incredibly cataclysmic four years. Although the actual war began with secession, this was not the only driving force. The economy of the Southern states, the Confederacy, greatly if not entirely depended on the institution of slavery. The Confederacy was heavily reliant on agriculture, and they used the profits made from the sale of such raw materials to purchase finished goods to use and enjoy. Their major export was cotton, which thrived on the warm river deltas and could easily be shipped to major ocean ports from towns on the Mississippi and numerous river cities. Slavery was a key part of this, as slaves were the ones who harvested and planted the cotton. Being such an enormous unpaid work force, the profits made were extraordinarily high and the price for the unfinished goods drastically low in comparison; especially since he invention of the cotton gin in 1793 which made the work all that much easier and quicker. In contrast, the economical structure of the Northern states, the Union, was vastly dependent on industry. Slavery did not exist in most of the Union, as there was no demand for it due to the type of industrial development taking place. As the Union had a paid work force, the profits made were lower and the cost of the finished manufactured item higher. In turn, the Union used the profits and purchased raw materials to use. This cycle...

Evaluation Of The Effectiveness Of Trade Embargoes

Although I am a strong critic of the use and effectiveness of economic sanctions, such as trade embargoes, for the sake of this assignment, I will present both their theoretical advantages and their disadvantages based upon my research. Trade embargoes and blockades have traditionally been used to entice nations to alter their behavior or to punish them for certain behavior. The intentions behind these policies are generally noble, at least on the surface. However, these policies can have side effects. For example, FDR's blockade of raw materials against the Japanese in Manchuria in the 1930s arguably led to the bombing of Pearl Harbor, which resulted in U.S. involvement in World War II. The decades-long embargo against Cuba not only did not lead to the topple of the communist regime there, but may have strengthened Castro's hold on the island and has created animosity toward the United States in Latin America and much suffering by the people of Cuba. Various studies have concluded that embargoes and other economic sanctions generally have not been effective from a utilitarian or policy perspective, yet these policies continue. Evaluation of the effectiveness of Trade Embargoes Strengths Trade embargoes and other sanctions can give the sender government the appearance of taking strong measures in response to a given situation without resorting to violence. Sanctions can be imposed in conjunction with other measures to achieve conflict prevention and mitigation goals. Sanctions may be ineffective: goals may be too elusive, the means too gentle, or cooperation from other countries insufficient. It is usually difficult to determine whether embargoes were an effective deterrent against future misdeeds: embargoes may contribute to a successful outcome, but can rarely achieve ambitious objectives alone. Some regimes are highly resistant to external pressures to reform. At the same time, trade sanctions may narrow the...