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

- Ventilation (VVentilation (VEE))- Gas transport (GT)Gas transport (GT)- Tissue respiration (TR)Tissue respiration (TR)- Functional anatomy of the RSFunctional anatomy of the RS- Basic mechanism of VBasic mechanism of VEE

- Biophysics of VBiophysics of VEE - Pressure-volume relations of lung and Pressure-volume relations of lung and

chestchest- Elastic and non-elastic properties of lungs Elastic and non-elastic properties of lungs

and thoraxand thorax

RespResp is the use of O 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 diffusion2) gas diffusion3) gas transport3) gas transport4) 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 mixture Each gas in a mixture of gases exerts a pres commensurate of gases exerts a pres commensurate with its own conc (partial pressures)with its own conc (partial pressures)– OO22 is 21% of air is 21% of airTherefore, at 760mmHg(atmospheric Therefore, at 760mmHg(atmospheric

pres), the POpres), the PO22=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 transport

The gases are transported in the blood in 2 forms; The gases are transported in the blood in 2 forms; eithereither

1- Dissolved in the plasma, OR1- Dissolved in the plasma, OR

2- Combine with Hb2- Combine with Hb

Under normal circumstances, approx 97-99% of Under normal circumstances, approx 97-99% of OO22 in a given vol of blood is transported in RBCs, in a given vol of blood is transported in RBCs, bound to Hb.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 RSFunctional anatomy of the RSAnatomy 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 gas The main function of the lungs is to provide continuous gas exchange between inspired air and blood in the pulmonary exchange between inspired air and blood in the pulmonary circulation, supplying Ocirculation, supplying O22 and removing CO and removing CO22, which is then cleared , which is then cleared from the lungs by subsequent expiration.from the 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 VBasic mechanism of VEE

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 downwards ↑↑ the vol of the thoracic cavity, and the vol of the thoracic cavity, and the intercostals muscles pulls the ribs up the intercostals muscles pulls the ribs up expanding the rib cage and further expanding the rib cage and further ↑↑ 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, its original vol, ↑↑ the air pressure in the lungs, the air pressure in the lungs, and forcing the air out.and forcing the air out.

Biophysics of VBiophysics of VEE: Pres vol relationship of the lungs : Pres vol relationship of the lungs and chestand chest

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

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

Elastic properties of the lungs and thoraxElastic properties of the lungs and thoraxCompliance is defined as a change in vol Compliance is defined as a change in vol resulting from a change in pres.resulting from a change in pres.Because compliance is an expression of the Because compliance is an expression of the distensibility of the elastic resp system, distensibility of the elastic resp system, measured values of compliance depend upon measured values of compliance depend upon the elastic recoil properties of the lungs and the elastic recoil properties of the lungs and chest wall. chest wall. Elastic recoil pres means that when the airways Elastic recoil pres means that when the airways are open and there is no airflow, elastic recoil are open and there is no airflow, elastic recoil pressure is equal to transpulmonary pressure.pressure is equal to transpulmonary pressure.

Pstl = Palv - Ppl Pstl = Palv - Ppl Elastic properties of the thoraxElastic properties of the thorax: If the volume of : If the volume of the thorax-diaphragm is reduced by contraction the thorax-diaphragm is reduced by contraction of the muscles of expiration, the chest wall tends of the muscles of expiration, the chest wall tends to resist compression and, by tending to recoil to resist compression and, by tending to recoil outward to its resting vol, creates a –ve pres outward to its resting vol, creates a –ve pres within the system. within the system.

Volume-pressure relationships of isolated lungsVolume-pressure relationships of isolated lungs

Volume-pressure relationships of isolated chest wallVolume-pressure relationships of isolated chest wall