Introduction to Respiration PDF

INTRODUCTION TO RESPIRATION By Dr. Eman Ibrahim El-gizawy Assitant proffesseur of medical physiology department ,faculty of medicine ,menoufia university Respiration (ventilation)(breathing) Definition: Uptake of O2 and withdrawal of CO2 into ext...

INTRODUCTION TO RESPIRATION By Dr. Eman Ibrahim El-gizawy Assitant proffesseur of medical physiology department ,faculty of medicine ,menoufia university Respiration (ventilation)(breathing) Definition: Uptake of O2 and withdrawal of CO2 into external environment Subdivided into 3 major steps External respiration Respiratory function of blood Internal respiration or tissue respiration Normal respiratory rate at different ages: Newborn: 30 -60 cycle/min Late childhood: 15-25 cycle/min Early childhood: 20 -40cycle/min Adult: 12 -16 cycle /min. Respiratory unit: Is the structural and functional unit of the lung.it is the terminal portion of the respiratory tract and exchanges of gases occurs in this portion Include : respiratory bronchiole Þ alveolar duct Þ alveolar sac Þantrum Þ alveoli Respiratory membrane: o Is membranous structure through which exchange of gases occurs. o Separates air in the alveoli from blood in capillary. o Formed of alveolar membrane and capillary membrane. o Its surface area 70 m2 & thickness 0.5 micron Non Respiratory functions of respiratory tract: 1. Olfaction (nostrils) 2. Vocalization (larynx) 3. Prevention of dust particles (nasal hairs , nasal mucous membrane, phagocytic action of macrophage) 4. Maintenance of water balance 5. Respiratory protective reflexes  cough reflex sneezing reflex swallowing reflex irritants irritants while swallowing of food stimulus respiration arrested for a while deep inspiration deep inspiration swallowing apnea during mechanism followed by forced followed by forced pharyngeal stage expiration with expiration with closed glottis opened glottis pathway Receptor along RT nasal mucosa pharynx Afferent vagus- trigeminal trigeminal glossopharyngeal Efferent vagus trigeminal vagus center medulla oblongata medulla oblongata medulla oblongata  Pulmonary circulation Pulmonary blood vessel: o Pulmonary artery: carry deoxygenated blood from right ventricle to the alveoli ( pulmonary circulation) Divided until it form capillary plexus that has intimate relationship with alveoli o Bronchial artery: supply oxygenated blood to other structure of the lungs Physiological shunt : Diversion through which the venous blood is mixed with arterial blood Flow of deoxygenated blood from bronchial circulation into pulmonary veins Characteristic features of pulmonary blood vessels 1. Pulmonary artery has a thin wall its thickness is only about 1/3 of the thickness of the systemic aortic wall. 2. Pulmonary blood vessels are highly elastic and distensible 3. smooth muscle coat isn't well developed 4. true arterioles have less smooth muscle fibers 5. pulmonary capillaries larger than systemic capillaries 6. Vascular resistance in pulmonary circulation is very low 1/10th of the systemic circulation 7. pulmonary vascular system is a low pressure system  Pulmonary blood flow lungs accommodate amount of blood which is equal to the amount accommodated by the whole body Pulmonary blood pressures systolic pressure: 25 mmHg diastolic pressure: 10 mmHg mean arterial pressure: 15 mmHg pulmonary capillary pressure: 7mmHg This pressure is sufficient to pull exchange of gases between alveoli and the blood.