Anatomy and physiology of respiratory system

The respiratory system (also respiratory apparatus, ventilatory system) is a biological system, consisting of specific organs and structures used for gas exchange in human.

and the knowledge of this system give details view regarding respiratory system and its abnormality

1. Anatomy And Physiology of Respiratory System

2. Introduction The body cell continually use oxygen for the metabolic reaction that release energy from nutrient molecule and produce ATP. At the same time , these reaction release carbon- di -oxide Because of excessive amount of carbon di oxide produces acidity that can be toxic to the cell, excess CO2 must be eliminated quickly and efficiently The respiratory system supports to supply oxygen and eliminate carbon- di -oxide

3. Definition The respiratory system (also respiratory apparatus , ventilatory system ) is a biological system, consisting of specific organs and structures used for gas exchange in human.

4. Organs of Respiratory System: Nose and nasal cavity. Pharynx (throat) Larynx (voice box) Trachea (wind pipe) Bronchi Bronchioles Lungs Conducting zone Alveolar ducts Alveolar sac Alveoli Respiratory zone

5. NOSE AND NASAL CAVITY POSITION AND STRUCTURE Main route of air entry. Especially Two cavities divided by a SEPTUM. Anteriorly consist hyaline cartilage. The roof is formed by ethmoid bone The floor is formed by roof of the mouth . The medial wall formed by the septum . The lateral wall formed by the maxilla.

6. RESPIRATORY FUNCTIONS OF THE NOSE The first of the respiratory passages. Warming - Due to the immense vascularity of the mucosa. Filtering and cleaning- This occurs due to hairs which trap larger particles. Humidification - As air travels over the moist mucosa, it becomes saturated with water vapour.

7. Pharynx The pharynx is the part of the throat that is behind the mouth and nasal cavity and above the esophagus and the larynx. Length- 12-14cm (extends from the base of the skull to the level of 6 th cervical vertebra.) Position Superiorly- Base of the skull. Inferiorly- Continuous with the oesophagus. Anteriorly -Incomplete wall because of the nose, mouth and larynx opening. Posteriorly - Areolar tissue & first 6 vertebra.

8. For descriptive purposes the pharynx is divided into three parts: The Nasopharynx The oropharynx The laryngopharynx The nasopharynx - The nasal part of the pharynx lies behind the nose. The oropharynx - The oral part of the pharynx lies behind the mouth. The laryngopharynx - The laryngeal part of the pharynx extends from the oropharynx .

9. STRUCTURE The pharynx is composed of three layers: Mucous membrane lining Fibrous tissue Smooth muscle Blood supply Facial artery Facial vein Internal jugular veins Nerve supply Vagus nerve Glossopharyngeal nerve

10. Functions Passageway for air and food. Warming and humidifying. Taste . There are olfactory nerve endings. Hearing . The auditory tube,extending from the nasopharynx to each middle ear. Protection . The lymphatic tissue of the pharyngeal tonsils produces antibodies. Speech . Act as a resonating chamber for sound ascending from the larynx.

11. Larynx POSITION The larynx or voice box extends from the root of the tongue. It lies in front of the laryngopharynx at the level of 3 rd , 4 th ,5 th and 6 th cervical vertebra. Until the puberty there is little difference in the size of the larynx between the sexes. It grows larger in the male. Superiorly- The hyoid bone & roof of the tongue. Inferiorly- Continuous with the trachea. Anteriorly -The muscle of the neck. Posteriorly- .The laryngopharynx and 3 rd to 6 th cervical vertebra.

12. STRUCTURE The larynx is composed of several irregularly shaped cartilages attached to each other by ligaments and membranes. The main cartilages are: 1 thyroid cartilage 1 cricoid cartilage hyaline cartilage 2 arytenoid cartilage 1 epiglottis elastic-fibro cartilage

13. The thyroid cartilage - This is the most prominent & consists of 2 flat pieces of hyaline cartilage & fused anteriorly forming the Adam’s apple . The cricoid cartilage - This lies below the thyroid cartilage & composed of hyaline cartilage. The arytenoid cartilages - These are two roughly pyramid-shaped hyaline cartilages situated on top of the broad part of the cricoid cartilage. The epiglottis - This is a leaf-shaped fibroelastic cartilage attached to the inner surface of the anterior wall of the thyroid cartilage. Blood and nerve supply Superior and inferior laryngeal arteries. Thyroid veins. Superior laryngeal nerves.

14. FUNCTIONS Production of sound Speech Protection of the lower respiratory tract During swallowing the larynx moves upwards and hinged epiglottis closes over the larynx. Passageway for air Humidifying Filtering Warming

15. Trachea Position The trachea or windpipe is a continuation of the larynx & extends downwards to about the level of T-5 where it divides into right & left primary bronchi. Length- 10-11cm Relation Superiorly- the larynx Inferiorly- the right & left bronchi Anteriorly - upper part- the thyroid gland, lower part- the arch of aorta & the sternum. Posteriorly- .the oesophagus Laterally- the lungs

16. STRUCTURE Composed of 3 layers of tissue. ( i ) fibrous & elastic tissue (ii) smooth muscle (iii) ciliated columnar epithelium Held open by between 16-20 incomplete cartilage rings (C-shaped) Blood supply Inferior thyroid artery Bronchial artery Venous drainage Inferior thyroid veins Nerve supply Laryngeal nerve

17. FUNCTIONS Support and patency Mucociliary escalator Cough reflex Warming Humidifying Filtering

18. Bronchi and Bronchioles The two primary bronchi when the trachea divides about the level of T-5. The right bronchus This is wider,shorter and more vertical than the left bronchus. Length-2.5cm After entering the right lung,it divides into 3 branches,one to each lobe.

19. The left bronchus This is narrower than the right Length-5cm After entering the left lung, it divides into 2 branches, one to each lobe. STRUCTURE Th e b r onch i a r e c omp o se d o f t h e same issues as the trachea. Are lined with ciliated columnar epithelium. Ciliated columnar mucous membrane changes gradually to non-ciliated cuboidal -shaped cells in the distal bronchioles.

20. Division Division of bronchi Bronchioles Terminal Bronchioles Respiratory bronchioles Alveolar ducts Alveoli

21. The wider passages are called conducting airways Conducting airways,bring air into the lungs & their walls are too thick to permit gas exchange. Blood supply Bronchial arteries Venous drainage Bronchial veins Nerve supply Vagus nerve Lymph drainage The Thoracic duct

22. FUNCTIONS Control of air entry Warming & humidifying Support & patency Removal of particulate matter Cough reflex

23. RESPIRATORY BRONCHIOLES & ALVEOLI Each lobule is supplied with air by a terminal bronchiole Which further subdivides into respiratory bronchioles, alveolar ducts and large numbers of alveoli ( air sacs ) About 150 million alveoli in the adult lung In these structures that the process of gas exchange occurs. As airways progressively divide & become smaller & smaller, their walls gradually become thinner. These distal respiratory passages are supported by a loose network of elastic connective tissue. Exchange of gases in the lungs takes place in alveoli

24. Nerve supply Vagus nerve FUNCTIONS External respiration This is exchange of gases by diffusion between the alveoli and the blood. Defence against microbes Protective cells present within the lung tissue, include lymphocytes & plasma cells, which produce antibodies. Exchange of gases

25. Lungs There are two lungs ,one lying on each side. Shape- cone Weight -600-700gms Length -20-24cm Colour -pinkish Lobes - three lobes in the right lung two lobes in the left lung Lobes are separate by the fissures The area between the lungs is the mediastinum .

26. Surfaces Apex A base Costal surface Medial surface Apex – rounded and rises into the root of the neck. A base -this is concave & semilunar in shape, lies on the thoracic surface of the diaphragm. Costal surface- this surface is convex & lies against the costal cartilages. Medial surface- this surface is concave & has a roughly triangular-shaped area,called the hilum.The pulmonary artery supplying the lung & two pulmonary veins draining it.

27. The pleura consists of a closed sac of serous membrane,one for each lung which contains a small amount of serous fluid . The lung is invaginated or pushed into this sac. It forms two layers : ( i )The visceral pleura (ii)The parietal pleura ( i )The visceral pleura - This is adherent to the lung ,covering each lobe & passing into the fissures that separate them. (ii)The parietal pleura - This is adherent to the inside of the chest wall & the thoracic surface of the diaphragm.

28. The pleural cavity The two layers of pleura are separated by a thin film of serous fluid which allows them to glide over each other. Preventing friction between them during breathing. The serous fluid is secreted by the epithelial cells of the membrane .

29. RIGHT LUNG The right lung has more lobes and segments than the left. It is divided into three lobes: Upper or superior lobe Middle lobe Lower or inferior lobe They separate by two fissures One oblique fissure which separates middle & lower lobe One horizontal fissure which separates middle & upper lobe

30. LEFT LUNG The left lung is divided into two lobes ( i ) upper lobe (ii) lower lobe They separate by the oblique fissure Left lung does not have a middle lobe The mediastinal surface of the left lung has a large cardiac impression or cardiac notch where the heart sits.

31. BLOOD SUPPLY Bronchial arteries Pulmonary capillaries,where there is exchange of oxygen & carbon dioxide take place between blood & tissues. VENOUS DRAINAGE Bronchial vein NERVE SUPPLY Vagus nerve

32. FUNCTION Control of air entry Warming & humidifying Support & patency Removal of particulate matter Cough reflex

33. respiration The term respiration means the exchange of gases between body cells and the environment. Breathing or pulmonary ventilation This is movement of air into and out of the lungs. Exchange of gases: This takes place: In the lungs: external respiration. In the tissues: internal respiration.

34. breathing Breathing supplies oxygen to the alveoli and eliminates carbon dioxide. MUSCLES OF BREATHING Expansion of the chest during inspiration occurs as a result of muscular activity partly voluntary and partly involuntary. The main muscles used in normal quiet breathing are the INTERCOSTAL MUSCLES and the DIAPHRAGM . During difficult or deep breathing they are assisted by muscles of the neck shoulders and abdomen.

35. INTERCOSTAL MUSCLES There are 11 pairs of intercostal muscles that occupy the spaces between the 12 pairs of ribs. They are arranged in two layers,the external and internal intercostal muscles The first rib is fixed. Therefore, when the intercostal muscles contract they pull all the other ribs towards the first rib.Because of the shape and sizes of the ribs they move outwards when pulled upwards,enlarging the thoracic cavity.

36. DIAPHRAGM The diaphragm is a dome-shaped muscular structure separating the thoracic and abdominal cavities. It forms the floor of the thoracic cavity and the roof of the abdominal cavity and consists of a central tendon from which muscle fibres radiate to be attached to the lower ribs and sternum and to the vertebral column by two crura . When the muscle of the diaphragm is relaxed ,the central tendon is pulled downwards to the level of the T-9,enlarging the thoracic cavity in length. This decreases pressure in the thoracic cavity and increases it in the abdominal and pelvic cavities.

37. The intercostals muscles and the diaphragm contract simultaneously, enlarging the thoracic cavity in all directions. CYCLE OF BREATHING The average respiratory rate is 12 to 15 breaths/minute. Each breath consists of three phases : ( i )Inspiration (ii)Expiration (iii)Pause.

38. Inspiration When the capacity of the thoracic cavity is increased by simultaneous contraction of the intercostal muscles and the diaphragm. The parietal pleura moves with the walls of the thorax & the diaphragm. This reduces the pressure in the pleural cavity to a level considerably lower than atmospheric pressure. The visceral pleura follows the parietal pleura ,pulling the lungs with it. This expands the lungs and the pressure within the alveoli and in the air passages drawing air into the lungs in attempt to equalise the atmospheric and alveolar air pressure.

39. The process of inspiration is ACTIVE as it needs energy for muscle contraction. Inspiration lasts about 2 seconds. (ii)Expiration Relaxation of the intercostal muscles and the diaphragm results in downward and inward movement of the rib cage and elastic recoil of the lungs. As this occurs pressure inside the lungs exceeds that in the atmosphere and so air is expelled from respiratory tract. The still contain some air are prevented from collapse by the intact pleura. This process is PASSIVE as it does not require the expenditure of energy.

40. Lungs Volume and Capacity Respiratory cycles -15/minute Tidal volume (TV)- this is the amount of air passing into and out of the lungs during each cycle of breathing. About 500ml is tidal volume. Minute ventilation(MV)- the total volume of air inhale and exhale each minute It is calculated by respiratory rate multiply by tidal volume

41. E.g.- if respiratory rate is 12 breath per minute. MB=12 br /min X 500 ml/ br =6 lit./min. The lower than normal minute ventilation usually is a sign of pulmonary mal-function. The apparatus commonly used to measure the volume of air exchanged during breathing and the respiratory rate is a spyrometer or respirometer .

42. Anatomic (Dead Space) Tidal volume varies from one person to another person and in same person at different time. About 70% of the tidal volume (350ml) actually reaches the respiratory zone of the respiratory system. The other 30% (150ml) remain in the conducting airway with air that does not undergo respiratory exchange are known as anatomical respiratory dead space.

43. Alveolar ventilation rate It is the volume of air per minute that actually reaches the respiratory zone is known as alveolar ventilation. Alveolar ventilation rate is tidal volume – respiratory dead space (500-150=350ml/ br ). Alveolar ventilation rate ( avr )=breath/min x alveolar ventilation. E.g.- if respiratory rate is 12 br /min. Avr =12 x 350=4200ml/min

44. Inspiratory Reserve Volume While taking a very deep breath, person can inhale good deal more than 500ml and this additional inhale air is called the inspiratory reserve volume. In average adult male=3100ml. In average adult female=1900ml.

45. Expiratory Reserve Volume Inhale normally and then exhale as forcly as possible one should be able to push out consideriable more air in addition to the 500ml of tidal volume is called expiratory reserve volume. In males =1200ml In females=700ml

46. Forced expiratory volume The volume of the air that can exhale from the lung in 1 sec. with maximum following the maximal inhalation.

47. Residual volume After the expiratory reserve volume is exhaled, air remain in the lungs because some atmospheric intra-pleural pressure keep the alveoli slightly inflated, and some air also remain in the non-collapsible airway this volume which cannot be measured by spyrometry is called residual volume. In males = 1200ml In female = 1100ml

48. Minimal volume If the thoracic cavity is opened the inta -pleural pressure rises to equal that atmospheric presure and fore out some of the residual volume the air remains is called minimal volume

49. Lung Capacities Lung capacities are combination of specific lung volume. Inspiratory capacity =tidal volume+inspiratory reserve volume In males= 500ml+3100ml=3600ml In females= 500ml+1900ml=2400ml functional residual capacity = residual volume+expiratory reserve volume In males= 1200ml+1200ml=2400ml In females= 1100ml+700ml=1800ml

50. Vital capacity = inspiratory reserve volume+ tidal volume+ expiratory reserve volume. In males=3100ml+500ml+1200ml=4800ml In females= 1900ml+500ml+700ml=3100ml Total lung capacity = vital capacity + residual volume In males= 4800ml+1200ml=6000ml In females= 3100ml+1100ml= 4200ml

51. Pulmonary Ventilation The process of gas exchange in the body for respiration has 3 basic steps- Pulmonary ventilation (breathing) is a inhalation exhalation of air and involves the exchange of air between the atmosphere and the alveoli of the lung. External respiration is the exchange of gases between the alveoli of lungs and the blood in pulmonary capillaries across the respirtory membrane. In this process pulmonary capilary blood gains O2 and looses CO2

52. internal respiration- It is the exchange of gases between blood in systemic capillaries and tissue cells. In this step the blood looses O2 and gain CO2 In pulmonary ventilation air flows between the atmosphere and the alveoli of the lungs because of altering pressure difference created by contraction and relaxation of respiratory muscles.

53. Pressure change during pulmonary ventilation Air moves into the lungs when the air pressure inside the lung is less then the air pressure in the atmosphere. Air moves out of the lung when the air pressure inside the lung is greater than the air pressure in the atmosphere Inhalation - the air pressure inside the lungs is equal to the air pressure in the atmosphere which at sea level is about 7600 mm Hg or one atm. For air to flow into the lung, the pressure inside the alveoli must become lower than the atmospheric pressure this condition is achieved by increasing the size of lung.

54. Exhalation – it is also due to pressure gradient but in this case the gradient is in the opposite direction. The pressure in the lungs is greater than the pressure in the atmosphere Normal exhalation during quite breathing unlikely inhalation it is a passive process because no muscular contraction are involved. Exhalation result from elastic recoil of the chest wall and lung both of which have a natural tendency to spring back after they have been stretched

55. Factor affecting pulmonary ventilation Surface tension of alveolar fluid. Compliances of the lung. Airway resistance.

56. EXCHANGE OF GASES Inhaled oxygen enters the lungs and reaches the alveoli. The layers of cells lining the alveoli and the surrounding capillaries are each only one cell thick and are in very close contact with each other. Oxygen passes quickly through air-blood barrier into the blood in the capillaries. Similarly, carbon dioxide passes from the blood into the alveoli and is then exhaled.

57. Diffusion of oxygen & carbon dioxide depends on pressure differences. DIFFUSION OF GASES External respiration External respiration refers to gas exchange across the respiratory membrane in the lungs. Each alveolar wall is one cell thick and sourrounded by a network of tiny capillaries. Carbon dioxide diffuses from venous blood down its concentration gradient into the alveoli. By the same process, oxygen diffuses from the alveoli into the blood.

58. Internal respiration Internal respiration refers to gas exchange across the respiratory membrane in the metabolizing tissues, like your skeletal muscles, for example. Blood arriving at the tissues has been cleansed of it’s CO2 & saturated with O2 during it’s passage through the lungs therefore has a higher O2 & lower CO2 than the tissues. This concentration gradients between capillary blood and the tissues lead gases exchange. O2 diffuses from the bloodstream through the capillary wall into the tissues. CO2 diffuses from the cells into the extracellular fluid then into the bloodstream towards the venous end of capillary.

59. Transport of blood oxygen & carbon dioxide is essential for internal respiration to occur. OXYGEN Oxygen is carried in the blood in as combination with haemoglobin as oxyhaemoglobin. CARBON DIOXIDE It is excreted by the lungs & transported by combined with haemoglobin as carbaminohaemoglobin. CONTROL OF RESPIRATION The respiratory centre: Medulla oblongata

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