free essays
Free essays

Anatomy and Physiology of the Respiratory System


Anatomyand Physiology of the Respiratory System


Theribs, thoracic wall and muscles and the diaphragm in human beings areeasily movable and their movement alters the volume of the chestcavity to bring about inhalation and exhalation. During a restinginspiration both the external intercostals muscle and the diaphragmcontract so as to provide room for the lungs to increase its volume.The diaphragm moves downward increasing the capacity of the thoraciccavity, and the external intercostals muscles lug the ribs upward andoutward, and in the process expanding the rib cage and furtheraugmenting the volume of the chest (Lalley,2012). The increase in thoracic volume reduces the pressure in thelungs and this lowers the pressure inside as compared to thebarometric pressure. Since air moves from a region of higher pressureto a region of low pressured, it travels in through the nostril,throat, larynx and trachea into the alveoli of the lungs (Reyes etal, 2000).

Duringthe process of expiration in a resting person, the diaphragm and theexternal intercostals muscle relax so as to restore the originalvolume of the thoracic cavity (smaller volume). The internalintercostals muscle contract to cause pressure inside the pleuralcavity to increase, and as a result reducing the alveolar volume andaugmenting the intrapulmonary pressure over the barometric airpressure (Reyes et al, 2000). The pressure variation brought by thesephysiological movements of diaphragm, rib cage and intercostalsmuscle air pushes air out of the lungs.

Atrest the rate of metabolic activity is low and the rate of breathingis also low. Inhalation and exhalation is controlled by a group ofchemo receptors positioned in the arteries that examine the amount ofoxygen and carbon dioxide in blood. When the amount of oxygen presentin the body tissues reduce, the rate of ventilation increases toincrease oxygen supply. This is achieved through the discharge ofcarbonic acid from carbon IV oxide which forms hydrogen ions whichincrease the rate of breathing (Saroj, 2006).


Duringperiods of strenuous physical activity the amount of oxygen needed inthe body increases considerably and the ventilation rate and depth ofbreathing is increased. The volume of the lungs increases by up to15% during exercise to meet all the oxygen need. The human lungs areincased in the rib cage which can only expand to a certain limit(Lalley,2012). The expansion of the rib cage, by moving upwards and outwardsduring inhalation together with the contraction of diaphragm allowthe volume of the lungs to change. Tidal volume refer to the amountof air breathe in at rest. At periods of intense physical activitythe tidal volume increases significantly to allow the lungs toaccommodate more air (oxygen) to meet the body demands (Kathleen L,2010).

Duringforced inspiration such as at period of intense physical activity thepulmonary ventilation is 15-20 times greater than at rest (George,2005). Expansion of the abdominal wall muscle (internal and externaloblique, rectus abdominis and transversusabdominis) help to decreaseintra-abdominal pressure which pulls the diaphragm downwards. Thereare other accessory muscles that help in lifting of the rib cage upand outwards rapidly during vigorous breathing. These include thesternocleidomastoid muscles that originate from the manubriumsterniand medial third of the clavicle. These muscles play a significantrole in raising the ribs cage up and outwards. Particularly duringphysical activity, the contribute to inhalation together with theserratus,trapezius muscles and minor and major pectoral muscles(Kathleen L, 2010).This decreases in vertical dimension of thethoracic cavity which leads to increase in the intra-alveolar andintrapleural pressure that pushes air out into the atmosphere.Exhalation involves the movements of the same muscles, but theintercostals muscles move in reverse direction while the diaphragmretains its normal position to increase pressure and push air out ofthe lungs.


Thoracicwall, diaphragm, lungs and other related muscles undergoes a range ofphysiological and anatomical changes with age. As people get oldercalcification comes about at the junction between the rib, thesternum and the spinal column. The deformity of the chest wall andthe thoracic spine due to osteoporosis weakens the respiratory systemconformity resulting to increase in work of breathing. Loss ofelasticity occurs to most of the muscle of the lungs and chest,significantly limiting the expansion of the chest (Lalley,2012).Muscle atrophy leads to reduction in muscle capacity, strength andendurance. The lungs of a human mature between the ages of 20 -25 andafterward aging are linked with reduced lung function.(Sharma&ampGoodwin,2006).The alveoli which forms the surface where gas exchange takesplace becomes stiffer and are unable to completely relax and empty.The dead space in the alveolar increases as one age and consequentlythe total amount of air that is allowed in the alveoli and the rateat which the air flow out is substantially reduced. Aging causes thelung parenchyma to lose its supporting structure resulting toincreased dilation of air spaces, a phenomenon referred to as senileemphysema.

Hardeningof the thoracic cage caused by increase calcification of the rib cagediminishes the capacity and ability of the thoracic cage to expandduring inspiration and exerts a mechanical limitation to thediaphragm to yield effective contraction. The change in volume of thechest wall and lungs due to changes in pressure is affected by thecompliance of the chest wall and lungs. Due to aging the structure ofthe thoracic cage is altered decreasing chest wall compliance(Kathleen L, 2010).


Physicalexercise is paramount in maintaining a healthy respiratory system. It contributes to body fitness, controlling body weight, building andsustaining healthy bone density, muscle strength and generalphysiological wellbeing (Garrett, 2000). The skeletal muscle controlsthat movement of the diaphragm and intercostals muscle whose movementis pivotal in inspiration and expiration. Long term physical exerciseimproves endurance and strength of these respiratory musclespermitting deeper, fuller and more efficient inhalation. Capillariesform the walls through which gaseous exchange takes place. Exercisecontinually increases the dilation of blood vessels including thecapillaries. Long term exercise leads to an increase in the numberand size of alveolar capillaries which makes gaseous exchange moreefficient. This rapid inflow and outflow of air during exercise helpto wipe out excessive mucus along the respiratory system (Centers forDisease Control &amp Prevention, 1996). Excessive build up of mucusalong the respiratory system increases the risk to bacterialinfections. Regular physical activity in the long term counteractsmucus build up in the lungs allowing free movement of air in and outof the lungs. All the aforementioned respiratory response improvesthe efficiency of the lungs (Treas &amp Wilkinson, 2013). Exercisecreates a higher demand for oxygen in the body due to increased rateof metabolism to produce energy. At this time the brain stimulate thelungs to work extra hard to cater for increase oxygen requirement.The diaphragm is an vital muscle in the breathing process and regularexercise improves the efficiency of the lungs and diaphragm. Exerciseis also important to the respiratory system since it help to reducethe chances of contracting respiratory


Garrett,W. E. (2000). Exerciseand sport science.Philadelphia [u.a.: Lippincott Williams &amp Wilkins.

George,R. B. (2005). Chestmedicine: Essentials of pulmonary and critical care medicine.Philadelphia, PA: Lippincott Williams &amp Wilkins.

Gulshan,S.&ampGoodwin,J.(2006). Effectof aging on respiratory system physiology and immunology.National Institute of Health

KathleenLutz. (2010). NewJersey Department of Health and Senior Services.Retrieved April 2 fromhttp://www.state.nj.us/health/ems/documents/news/respiratory_issues.pdf

Lalley,P. (2012). The aging respiratory system—Pulmonary structure,function and neural control. RespiratoryPhysiology &amp Neurobiology187 (2013) 199– 210

Reyes,A., Santiago, G., Hidalgo, G. (2000). Biologyfor Non-science Majors.Rex Bookstore, Inc. Retreived from:http://books.google.com/books?id=3ngjzVVZOtYC&amppg=PA78&ampdq=Inhalation+and+expiration+in+human+beings&amphl=en&ampsa=X&ampei=Apk7U6qkK8SshQe0i4GQCg&ampredir_esc=y#v=onepage&ampq=Inhalation%20and%20expiration%20in%20human%20beings&ampf=false

Saroj,P. (2006).The Pearson Guide to the B.Sc. (Nursing) Entrance Examination.Pearson Education India.

Treas,L. S., &amp Wilkinson, J. M. (2013). Basicnursing: Concepts, skills, &amp reasoning.Philadelphia, PA: F.A. Davis.

UnitedStates. (1996). Physicalactivity and health: A report of the Surgeon General : ExecutiveSummary.Atlanta, Ga: U.S. Dept. of Health and Human Services, Centers forDisease Control &amp Prevention, National Center for Chronic DiseasePrevention and Health Promotion.