Respiratory system- physiology.pptx.72628

Physiology

1. University of Duhok College of Veterinary Medicine Department of Theriogenology, Anatomy and Physiology Physiology of Respiratory System L2 Prepared by Dr. Tareek Abdulqadir Abdal

2. Gas exchange in the lungs Air-Blood barrier (Pulmonary membrane, respiratory membrane, Alveolar-Capillary barrier): The membrane which gas exchange occurs which is about 0.2 µm. The alveolar-capillary barrier is composed of: A thin alveolar epithelium An epithelial basement membrane A thin interstitial space between the alveolar basement membrane and capillary basement membrane. A capillary basement membrane that in many places fuses with the alveolar epithelial basement membrane The capillary endothelial membrane

3. Partial pressures of O 2 and CO 2 : Partial pressure is the pressure exerted by an individual gas in a mixture of gases. The atmospheric pressure (at sea level) is about 760 mmHg, oxygen form 21% of atmosphere, and CO 2 form 0.04 % . Partial pressure of O 2 = 21% x 760 = 160 mm Hg Partial pressure of CO 2 = 0.04% x 760 = 0.3 mm Hg

4. Transport of ( O 2 ) and (CO2)in the blood: A. Transport of Carbon Dioxide (CO2): Carbon dioxide is transported in the blood from tissue to the lungs in three ways: Dissolved in plasma (7%): The solubility of CO2 in blood is about 20 times that of O2 , so that there is more CO2 than O2 in simple solution. Carbaminohemoglobin (CO2 -Hb) (23%): About 20% of the CO2 can binds to the amine (-NH2 ) groups in proteins, particularly Hb to form carbamino compounds. Bicarbonate ions (HC03 -): Most of the CO2 in the blood (70%) are transported as bicarbonic ion (HCO3 - ). The RBCs contain the enzyme carbonic anhydrase, which catalyzes the formation of carbonic acid (H2CO3) from CO2 and H2O. Carbonic acid immediately dissociates into bicarbonate ions (HCO3 - )and hydrogen (H+ ) ions.

5. C O 2 transport and chloride shift

6. B. Transport of oxygen (O 2 ) in blood: Oxygen is carried in two ways by the blood: Combined with hemoglobin : - Most of the O2 (98.5 %) is carried in combination with hemoglobin. Each hemoglobin molecule having the capacity to combine with four molecules of O2. 2. Dissolved in plasma : (1.5 %) Reverse chloride shift in lungs

7. Factors affecting the Hb saturation with O2 : The strength that O2 binds to Hb is affected by several factors such as: Blood H+ concentration pCO2 Temperature of the body 2,3-diphosphoglycerate (2,3-DPG) in RBCs. Fever (↑ temperature) ↑ CO2, acidosis (↑ H +) and (↑ 2,3-DPG) reduce the Hb affinity for O2 and making it easier to unload O2 at the tissue (Shift the curve to the right). Hypothermia (↓ temperature) ↓ CO2, alkalosis (↓ H +) and (↓ 2,3-DPG) increase the Hb affinity for O2 and Hb binds to O2 more strongly (Shift the curve to the left)

8. Regulation of Respiration: Respiration is controlled by two mechanism: Neural control of respiration: Voluntary control: - It is located in the cerebral cortex Involuntary control: - It is located in the respiratory center in the pons and medulla oblongata Pons: In the pons, the pontine respiratory group includes: Pneumotaxic centre : It mainly controls rate and depth of breathing (Respiratory rhythm). It inhibits the inspiration by sending signal to the dorsal respiratory group neuron to stop inspiration, so that expiration can take place (switching off between inspiration and expiration). Apneustic centre : It promote inspiration, and in the absent of pneumotaxic centre, it cause deep inspiration.

9. Medulla oblongata: The respiratory center in the medulla oblongata is divided into two groups: Dorsal respiratory group: It control normal quiet inspiration by sending signal to diaphragm and cause normal quiet breathing, and the expiration is passive by elastic recoil of lung and chest wall. Ventral respiratory group: It control forced inspiration and forced expiration (Labored respiration)

10. II. Chemical control of respiration: Central chemoreceptors (Chemosensitive area): It is located in the ventral surface of medulla and sensitive to change of PCO 2 and H + concentration. CO 2 readily penetrates membranes, including the blood-brain barrier. The CO 2 enters the brain and CSF is promptly hydrated to form H 2 CO 3 . The H 2 CO 3 dissociates into H + and HCO 3 - The rise in the local H + concentration rises stimulates respiration. The magnitude of the stimulation is proportionate to the rise in H + concentration. Chemoreceptors in the medulla oblongata

11. b). Peripheral chemoreceptors: They are located outside the brain in the: Carotid bodies in the bifurcation of the common carotid arteries. Aortic bodies along the arch of the aorta. - They are especially important for detecting changes in O 2 in the blood, and a lesser extent to changes in CO 2 and H + ion concentrations. - Peripheral chemoreceptors are stimulated by decreasing of PO 2 in blood, and also by increasing of PCO 2 and H + ions in blood. Peripheral chemoreceptors

12. Common Terms: - Eupnea: Normal, comfortable breathing at rest. Apnea: Cessation of breathing. Dyspnea: Shortness of breath, or difficulty in breathing Polypnea (Tachypnea): Rapid, shallow or panting respiration Hyperpnea: Increase in depth of breathing, which may or may not be accompanied by an increase in the respiratory rate

13. Pulmonary Disorders: - Acute respiratory disease syndrome (ARDS): It is a severe inflammatory disease of the lung. The inflammation leads to impaired gas exchange. Infant respiratory distress syndrome (IRDS): It is a syndrome caused by lack of surfactant in the lungs of premature infants. Pneumothorax: The presence of gas in the intrapleural space (the space between the visceral and parietal pleurae) causing the lungs to collapse. Pulmonary fibrosis: is a lung disease that occurs when lung tissue becomes damaged and scarred. This thickened, stiff tissue makes it more difficult for oxygen to pass into the bloodstream. Emphysema: It is a chronic disease of the lung, in which the alveoli are damaged and ruptured and creating larger air spaces. Bronchitis: It is an inflammation of the bronchial tubes, which causes a cough that often brings up mucus.

14. Pneumonia: It is an inflammation of the alveoli, which filled with fluid or pus, making it difficult to breathe. It is usually caused by infection with viruses or bacteria. Atelectasis: It is the collapse of alveoli due to obstruction of air way or lack of surfactant. Asthma: It is a chronic disease of the lung in which the airways are inflamed and narrowed and very sensitive. Cyanosis: The term cyanosis means blueness of the skin, due to excessive amounts of deoxygenated hemoglobin in the skin blood vessels, especially in the capillaries , it is most easily seen in the nail beds, mucous membranes, in the earlobes, and lips, where the skin is thin. Carbon monoxide (CO) poisoning: - The CO poisoning is toxic because it reacts with hemoglobin to form carboxyhemoglobin ( COHb ), the COHb cannot take up O2. Hypercapnia : The presence of too much carbon dioxide (CO2) in the blood, this is normally caused by hypoventilation of the body which leads to CO2 retention.

15. Hypoxia: It is O 2 deficiency at the tissue level. Hypoxia has been divided into four types: Hypoxic hypoxia (anoxic anoxia): It is a result of insufficient oxygen available to the lungs, so the PO 2 at the arterial blood is reduced. Anemic hypoxia: It is caused by insufficient amount of hemoglobin to carry O 2 . Stagnant Hypoxia: It is caused by decreased blood flow ( hypoperfusion ) to the tissues as occurs in shock, syncope , and less O 2 available to the tissues. Histotoxic Hypoxia: It is the inability of cells to take up or use oxygen from the bloodstream, despite physiologically normal delivery of oxygen to such cells and tissues. It is may be caused by cyanide poisoning.