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Lec # 1 physical therapy physiology students
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- 2. Respiration isthe process by which oxygen is taken in and carbon dioxide is given out. The first breath takes place only after birth. Fetal lungs are non-functional. So, during intrauterine life the exchange of gases between fetal blood and mother’s blood occurs through placenta. After the first breath, the respiratory process continues throughout the life. Permanent stoppage of respiration occurs only at death.
- 3. Normal RespiratoryRate at Different Age Newborn : 30 to 60/minute Early childhood : 20 to 40/minute Late childhood : 15 to 25/minute Adult : 12 to 16/minute.
- 4. TYPES OF RESPIRATION Respiration is classified into two types: 1. External respiration that involves exchange of respiratory gases, i.e. oxygen and carbon dioxide between lungs and blood 2. Internal respiration, which involves exchange of gases between blood and tissues.
- 5. PHASES OF RESPIRATION Respiration occurs in two phases: 1. Inspiration during which air enters the lungs from atmosphere 2. Expiration during which air leaves the lungs. During normal breathing, inspiration is an active process and expiration is a passive process.
- 6. FUNCTIONAL ANATOMY OF RESPIRATORYTRACT Respiratory tract is the anatomical structure through which air moves in and out. It includes nose, pharynx, larynx, trachea, bronchi and lungs.
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- 8. Pleura Eachlung is enclosed by a bi-layered serous membrane called pleura or pleural sac. Pleura has two layers namely inner visceral and outer parietal layers. Visceral layer is attached firmly to the surface of the lungs. At hilum, it is continuous with parietal layer, which is attached to the wall of thoracic cavity.
- 10. Intra-pleural Spaceor Pleural Cavity Intra-pleural space or pleural cavity is the narrow space in between the two layers of pleura. Intra-pleural Fluid Intra-pleural space contains a thin film of serous fluid called intra-pleural fluid, which is secreted by the visceral layer of the pleura. Functions of intra-pleural fluid 1. It functions as the lubricant to prevent friction between two layers of pleura. 2. It is involved in creating the negative pressure called intra-pleural pressure within intra-pleural space.
- 11. Pleural Cavityin Abnormal Conditions In some pathological conditions, the pleural cavity expands with accumulation of air (pneumothorax), water (hydrothorax), blood (hemothorax) or pus (pyothorax).
- 12. Tracheobronchial Tree Tracheaand bronchi are together called tracheobronchial tree. It forms a part of air passage. Components of tracheobronchial tree Trachea bifurcates into two main or primary bronchi called right and left bronchi Each primary bronchus enters the lungs and divides into secondary bronchi Secondary bronchi divide into tertiary bronchi.
- 13. In rightlung, there are 10 tertiary bronchi and in left lung, there are 8 tertiary bronchi Tertiary bronchi divide several times with reduction in length and diameter into many generations of bronchioles When the diameter of bronchiole becomes 1 mm or less, it is called terminal bronchiole Terminal bronchiole continues or divides into respiratory bronchioles, which have a diameter of 0.5 mm.
- 15. Upper and LowerRespiratory Tracts Generally, respiratory tract is divided into two parts: o Upper respiratory tract that includes all the structures from nose up to vocal cords; vocal cords are the folds of mucous membrane within larynx that vibrates to produce the voice o Lower respiratory tract, which includes trachea, bronchi and lungs.
- 16. RESPIRATORY UNIT Parenchymaof lungs is formed by respiratory unit that forms the terminal portion of respiratory tract. Respiratory unit is defined as the structural and functional unit of lung. Exchange of gases occurs only in this part of the respiratory tract.
- 17. STRUCTURE OF RESPIRATORYUNIT Respiratory unit starts from the respiratory bronchioles. Each respiratory bronchiole divides into alveolar ducts. Each alveolar duct enters an enlarged structure called the alveolar sac. Space inside the alveolar sac is called antrum. Alveolar sac consists of a cluster of alveoli. Few alveoli are present in the wall of alveolar duct also. Each alveolus is like a pouch with the diameter of about 0.2 to 0.5 mm. It is lined by epithelial cells.
- 18. Thus, respiratoryunit includes: 1. Respiratory bronchioles 2. Alveolar ducts 3. Alveolar sacs 4. Antrum 5. Alveoli.
- 19. NON-RESPIRATORY FUNCTIONS OF RESPIRATORYTRACT Besides primary function of gaseous exchange, the respiratory tract is involved in several non-respiratory functions of the body. Particularly, the lungs function as a defense barrier and metabolic organs, which synthesize some important compounds.
- 20. Non-respiratory functionsof the respiratory tract are: 1. OLFACTION Olfactory receptors present in the mucous membrane of nostril are responsible for olfactory sensation. 2. VOCALIZATION Along with other structures, larynx forms the speech apparatus. However, larynx alone plays major role in the process of vocalization. Therefore, it is called sound box.
- 21. 3. PREVENTION OFDUST PARTICLES Dust particles, which enter the nostrils from air, are prevented from reaching the lungs by filtration action of the hairs in nasal mucous membrane. Small particles, which escape the hairs, are held by the mucus secreted by nasal mucous membrane. Those dust particles, which escape nasal hairs and nasal mucous membrane, are removed by the phagocytic action of macrophages in the alveoli. Particles, which escape the protective mechanisms in nose and alveoli are thrown out by cough reflex and sneezing reflex.
- 22. 4. DEFENSE MECHANISM Lungs play important role in the immunological defense system of the body. Defense functions of the lungs are performed by their own defenses and by the presence of various types of cells in mucous membrane lining the alveoli of lungs. These cells are leukocytes, macrophages, mast cells, natural killer cells and dendritic cells.
- 23. 5. MAINTENANCE OFWATER BALANCE Respiratory tract plays a role in water loss mechanism. During expiration, water evaporates through the expired air and some amount of body water is lost by this process. 6. REGULATION OF BODY TEMPERATURE During expiration, along with water, heat is also lost from the body. Thus, respiratory tract plays a role in heat loss mechanism.
- 24. 7. REGULATION OFACID-BASE BALANCE Lungs play a role in maintenance of acid base balance of the body by regulating the carbon dioxide content in blood. 8. ANTICOAGULANT FUNCTION Mast cells in lungs secrete heparin. Heparin is an anticoagulant and it prevents the intravascular clotting. 9. SECRETION OF ANGIOTENSINCONVERTING ENZYME Endothelial cells of the pulmonary capillaries secrete the angiotensin converting enzyme (ACE). It converts the angiotensin I into active angiotensin II, which plays an important role in the regulation of ECF volume and blood pressure.
- 25. 10. SYNTHESIS OFHORMONAL SUBSTANCES Lung tissues are also known to synthesize the hormonal substances, prostaglandins, acetylcholine and serotonin, which have many physiological actions in the body including regulation of blood pressure.
- 26. 26 Functions of theRespiratory System Gas Exchange O2, CO2 Acid-base balance CO2 +H2O←→ H2CO3 ←→ H+ + HCO3- Pulmonary defense Pulmonary metabolism and handling of bioactive materials Regulation of blood pH: Altered by changing blood carbon dioxide levels Carbonic acid Buffer system Sound production: Movement of air past vocal folds makes sound and speech Olfaction: Smell occurs when airborne molecules drawn into nasal cavity
- 27. 27 Ventilation: Action of breathingwith muscles and lungs Gas exchange: Between air and capillaries in the lungs. Between systemic capillaries and tissues of the body 02 utilization: Cellular respiration in mitochondria Breathing
- 28. 28 Conducting Airways Includes: FromTrachea --> Terminal bronchioles Trachea --> right and left main stem bronchi. Right main stem vulnerable to foreign particles Main stem bronchi -->lobar bronchi. Dichotomous branching: ~16 generations of airways Convection Flow
- 29. 29 Respiratory Zone Respiratoryzone Region of gas exchange between air and blood - Respiratory bronchioles - Alveolar ducts, Alveolar Sacs and - Alveoli
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- 32. 32 Respiratory Zone Alveoli Air sacs Honeycomb-likeclusters ~ 300 million. Large surface area (60–80 m2 ). Each alveolus: only 1 thin cell layer. Total air barrier is 2 cells across (2 mm) (alveolar cell and capillary endothelial cell).
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- 34. 34 Respiratory Zone Alveolar cells Alveolartype I 95% : structural cells. Alveolar type II 5%: secrete surfactant.
- 35. Alveolus and RespiratoryMembrane
- 36. 36 Thoracic Cavity Diaphragm: Sheets of striated muscle divides anterior body cavity into 2 parts. Above diaphragm: thoracic cavity: Contains heart, large blood vessels, trachea, esophagus, thymus, and lungs. Below diaphragm: abdominopelvic cavity: Contains liver, pancreas, GI tract, spleen, and genitourinary tract.
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- 39. Mechanism of Breathing Types of respiration: 1) External Respiration 2)Internal respiration Process of Respiration: 1) Inspiration 2) Expiration Types of breathing: 1) Abdominal or diaphragmatic breathing 2) Costal or thoracic breathing
- 40. 40 Inspiration Inspiration –Active process Diaphragm contracts -> increased thoracic volume vertically. Intercostals contract, expanding rib cage -> increased thoracic volume laterally. More volume -> lowered pressure -> air in. Negative pressure breathing
- 41. 41 Expiration Expiration –Passive Due to recoil of elastic lungs. Less volume -> pressure within alveoli is just above atmospheric pressure -> air leaves lungs. Note: Residual volume of air is always left behind, so alveoli do not collapse.
- 42. 42 Intrapleural space: “Space”between visceral & parietal pleurae. Visceral and parietal pleurae (membranes) are flush against each other. Lungs normally remain in contact with the chest wall. Lungs expand and contract along with the thoracic cavity. Mechanics of breathing
- 43. 43 Mechanics of breathing Compliance: This the ability of the lungs to stretch during inspiration lungs can stretch when under tension. Elasticity: It is the ability of the lungs to recoil to their original collapsed shape during expiration Elastin in the lungs helps recoil
- 44. Compliance Compliance isdefined as change in volume per unit change in pressure ∆V/∆P Measure of the ease with which lungs and thorax expand The greater the compliance, the easier it is for a change in pressure to cause expansion A lower-than-normal compliance means the lungs and thorax are harder to expand Conditions that decrease compliance Pulmonary fibrosis Pulmonary edema Respiratory distress syndrome
- 45. 45 Respiration It isthe process by which the body takes in oxygen and utilizes and removes CO2 from the tissues into the expired air It comprises of Ventilation by the lungs inspiration and expiration Gas exchange across alveolar membrane Diffusion in the alveoli. Transport of gases by blood (haemoglobin) Uptake of O2 and release of CO2 by tissues Diffusion at the cellular level
- 46. 46 Ventilation Mechanical process thatmoves air in and out of the lungs. Diffusion of… O2: air to blood. C02: blood to air. Rapid: large surface area small diffusion distance. Insert 16.1
- 47. 47 Alveoli 8 million alveolarducts 300 million alveoli (diameter 70-300 m) Total alveolar surface area ~ 60-80 m2 Alveolar membrane thickness < 1 m.
- 48. 48 Netter FH, CIBACollection of Medical Illustrations 2nd ed. 1980 vol.7, p. 29. Cross Section of Alveolus
- 49. 49 Alveolar capillary interface- schematic
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