RESPIRATORY RESPIRATORY

PHYSIOLOGYPHYSIOLOGY

Dr. Waheeb AlharbiDr. Waheeb Alharbi

ReferencesReferences

(1) Physiological basis of medical practice.(1) Physiological basis of medical practice.

By; John B. WestBy; John B. West

(2) Medical physiology (2) Medical physiology

By; Arthur C. Guyton & John E. HallBy; Arthur C. Guyton & John E. Hall

(3) Concise Human Physiology(3) Concise Human Physiology

By; M. Y. Sukkar, H. A. El-Munshid By; M. Y. Sukkar, H. A. El-Munshid

& M. S. m. Ardawi& M. S. m. Ardawi

Lecture 1Lecture 1- Defin of respDefin of resp- Func of respFunc of resp- VentVent- Gas transGas trans- Tissue respTissue resp- Functional anatomy of the resp Functional anatomy of the resp

systemsystem- Basic mechanism of ventBasic mechanism of vent- Biophysics of ventBiophysics of vent

Resp is the use of OResp is the use of O22 by the living cell for oxidation of by the living cell for oxidation of nutrients. This result in production of COnutrients. This result in production of CO22..

Resp can be divided into 4 main events;Resp can be divided into 4 main events;1) pulmonary vent 1) pulmonary vent 2) gas diffu2) gas diffu3) gas trans3) gas trans4) regulation of resp 4) regulation of resp

Vent is the movement of air between the environment and Vent is the movement of air between the environment and the alveoli. It can be spontaneous or artificial.the alveoli. It can be spontaneous or artificial.

Air is a mixture of gases. According to Dalton’s Law, the Air is a mixture of gases. According to Dalton’s Law, the total pres of a mixture of gases is the sum of the pres of the total pres of a mixture of gases is the sum of the pres of the individual gases (Pindividual gases (Ptotaltotal = P = P11 + P + P22 + P + P33 ……). ……).

VVEE = fr X V = fr X VTT

Dalton’s LawDalton’s Law

Dalton’s Law:Dalton’s Law: Each gas in a Each gas in a mixture of gases exerts a pres mixture of gases exerts a pres commensurate with its own conc (partial commensurate with its own conc (partial pressures)pressures)– Oxygen is 21% of airOxygen is 21% of air

At 760mmHg(atmospheric pres), the At 760mmHg(atmospheric pres), the POPO22=0.21 X 760=160mmHg =0.21 X 760=160mmHg

Partial pres of water (P HPartial pres of water (P H220): 47 mmHg0): 47 mmHg

At 760mmHg, POAt 760mmHg, PO22 = (760-47) X 0.21 = 150 = (760-47) X 0.21 = 150 mmHgmmHg

Gas transportGas transportThe gases are transported in the blood in 2 forms; The gases are transported in the blood in 2 forms;

1- Dissolved in the plasma1- Dissolved in the plasma

2- Combine with Hb2- Combine with Hb

Under normal circumstances, more than 98% of Under normal circumstances, more than 98% of the Othe O22 in a given vol of blood is transported in in a given vol of blood is transported in RBCs, bound to Hb.RBCs, bound to Hb.

Tissue respirationTissue respirationIt means getting energy out of glucose.It means getting energy out of glucose.

The most efficient form of resp is aerobic (require The most efficient form of resp is aerobic (require OO22) and anaerobic resp (does not require O) and anaerobic resp (does not require O22).).

Aerobic respAerobic resp: It is the normal process by which : It is the normal process by which food substances are broken down and oxidized to food substances are broken down and oxidized to provide energy.provide energy.

Glucose + OGlucose + O22 → CO → CO22 + H + H22O + energy releasedO + energy released

Anaerobic respAnaerobic resp: It means that energy can be : It means that energy can be derived from food substances without the derived from food substances without the simultaneous utilization of Osimultaneous utilization of O22..

Glucose → lactic acid + much less energy releasedGlucose → lactic acid + much less energy released

Functional anatomy of the resp systemFunctional anatomy of the resp systemAnatomy of the resp system is composed of;Anatomy of the resp system is composed of;1) the resp air ways1) the resp air ways2) the lungs2) the lungs3) the resp muscles3) the resp muscles4) the neural centers4) the neural centers

The main function of the lungs is to provide continuous GE The main function of the lungs is to provide continuous GE between inspired air and blood in the pulmonary circulation, between inspired air and blood in the pulmonary circulation, supplying Osupplying O22 and removing CO and removing CO22, which is then cleared from the , which is then cleared from the lungs by subsequent expiration.lungs by subsequent expiration.

The functional structure of the lung can be divided into; The functional structure of the lung can be divided into; 1- The Conducting zone, and1- The Conducting zone, and 2- The respiratory zone.2- The respiratory zone.

The Conducting zone (air flow): The Conducting zone (air flow): Air comes into the nose and the Air comes into the nose and the mouth through the pharynx, larynx and then through the trachea.mouth through the pharynx, larynx and then through the trachea.The respiratory zone (gas diffusion): The respiratory zone (gas diffusion): It begins when alveoli start to It begins when alveoli start to appear in the walls of the bronchioles.appear in the walls of the bronchioles.

Basic mechanism of ventBasic mechanism of vent

Breathing consists of 2 phases; inspiration (active Breathing consists of 2 phases; inspiration (active process) and expiration (passive process).process) and expiration (passive process).During inspiDuring inspi: The diaphragm and intercostals : The diaphragm and intercostals muscles contract. The diaphragm moves muscles contract. The diaphragm moves downwards increasing the vol of the thoracic downwards increasing the vol of the thoracic cavity, and the intercostals muscles pulls the ribs cavity, and the intercostals muscles pulls the ribs up expanding the rib cage and further increasing up expanding the rib cage and further increasing this vol. this vol. During expiDuring expi: The diaphragm and intercostals : The diaphragm and intercostals muscles relax. This returns the thoracic cavity to muscles relax. This returns the thoracic cavity to its original vol, increasing the air pressure in the its original vol, increasing the air pressure in the lungs, and forcing the air out.lungs, and forcing the air out.

Biophysics of vent: Pres vol relationship of the Biophysics of vent: Pres vol relationship of the lungs and chestlungs and chest

Compliance means the ability to expand or stretch.Compliance means the ability to expand or stretch.The compliance of a container is the change in its vol that The compliance of a container is the change in its vol that results from imposing a press differences across its walls. results from imposing a press differences across its walls. The larger the vol change in response to a given pres The larger the vol change in response to a given pres change, the greater the compliance.change, the greater the compliance.

Factors affecting the compliance include;Factors affecting the compliance include;1) the connective tissue structure of the lung1) the connective tissue structure of the lung2) the level of surfactant production2) the level of surfactant production3) the mobility of the thoracic cage3) the mobility of the thoracic cage

The significance of the balance of forces between the lung The significance of the balance of forces between the lung and chest wall is evident in what happens during thoracic and chest wall is evident in what happens during thoracic surgery or penetrating injury to the chest.surgery or penetrating injury to the chest.

Pleural pressurePleural pressure: It is the pres in the narrow space between : It is the pres in the narrow space between the lung pleura and chest wall pleura.the lung pleura and chest wall pleura.Alveolar pressureAlveolar pressure: It is the pres inside the lung alv.: It is the pres inside the lung alv.