Respiratory system

1. Respiratory system By SindhuPriya E S

2. Introduction • Respiration Respiration can be defined as the process of gaseous exchange between an organism and its environment. • Respiratory system The human respiratory system is a series of organs responsible for taking in oxygen and expelling carbon dioxide. 

3. Functions of Respiration • Exchange of gases • Maintaining Acid-base balance by excretion of CO2 • Purification of inspired air by the hair & mucous of the respiratory tract • Excretion of volatile substances like ammonia, ketone bodies, water vapour through expiration • Helps in maintaining homeostasis of metabolism in tissue • Temperature regulation • Water regulation

4. Parts of respiratory system • Nose • Pharynx • Larynx • Trachea • Two bronchi • Bronchioles & small air passages • Two lungs & their coverings, the pleura • Muscles of breathing – intercostal muscles & the diaphragm

5. functionally respiratory system is divided into

6. Anatomically Respiratory tract is divided into • Upper respiratory tract : organs present outside the thoracic region • Lower respiratory tract : Organs present in the thoracic region

7. Nose and nasal cavity Position and structure • Major entrance and exit for respiratory system • Only visible part of respiratory system • Structurally divided into • External portion / Nose • Internal portion / Nasal cavity • Consists of large irregular cavity divided into equal passages by a septum • Posterior bony part is formed by ethmoid bone and anteriorly by hyaline cartilage

8. Position and structure • Roof - ethmoid bone, sphenoid bone, frontal and nasal bone. • Floor - roof of oral cavity-PALATE • Medial wall is formed by septum • Lateral walls are formed by ethmoid bone and maxilla • Posterior wall is formed from posterior wall of pharynx

9. Lining of the nasal cavity Nasal cavity is lined with vascular ciliated columnar epithelial cells containing mucous secreting goblet cells

10. Openings into nasal cavity • Anterior nares / Nostrils : Openings from exterior to nasal cavity • Posterior nares : Openings from nasal cavity into pharynx • Paranasal sinuses : Cavities present in the bones of face and cranium containing air

11. Paranasal sinuses • The main sinuses are • Maxillary sinuses in the lateral walls • Frontal & sphenoidal sinuses in the roof • Ethmoidal sinuses in the upper part of the lateral walls

12. Functions of nose • Warming • Filtering & cleaning • Humidification • Olfactory function

13. PHARYNX • The pharynx is a 12-14 cm long tube like passage that connects the posterior nasal and oral cavities to the larynx and oesophagus • Pharynx is divided into • Nasopharynx – lies above the level of soft palate – pharyngeal tonsils • Oropharynx – lies below soft palate till hyoid bone – palatine tonsils • Laryngopharynx – lies below hyoid bone

14. Structure The wall of pharynx contains different layers • Mucosal membrane lining • Nasopharynx – Ciliated columnar epithelium • Oro and laryngopharynx – tougher stratified squamous epithelium

15. Fibrous tissue Thicker in the Nasopharynx where there is little muscle. Thinner towards the lower end where thick muscle layer • Smooth muscle Involuntary muscles which are helpful in swallowing. Upper end of the oesophagus is closed by the lower constrictor muscle, except during swallowing

16. Functions of pharynx • Passage for air and food • Warming & humidifying • Taste • Hearing • Protection against microbes

17. Larynx- Voice box • It extends from the root of tongue and the hyoid bone to the trachea. • It lies at the level of 3rd, 4th , 5th & 6th cervical vertebrae.

18. Cartilages Irregularly shaped structures • Thyroid cartilage - above • Cricoid cartilage - below • Arytenoid cartilages • Epiglottis - Elastic fibrocartilage • Leaf like structure – superior part of larynx closing glottis • Vocal cords- mucous membrane folds in glottis • Adducted-when muscles contracted • Abducted-when muscles relaxed Hyaline cartilage

19. Functions of larynx • Production of sound • Speech • Protection of lower respiratory tract • Passage way for air • Humidifying, filtering & warming

20. trachea • Wind pipe connecting larynx and bronchi • 12 cm long extends upto 5th thoracic vertebrae • Contains 16-20 ‘C’ shaped cartilagenous rings whose ends are connected by Trachealis muscle

21. Layers of trachea • Outer layer • fibrous and elastic tissue covering cartilage • Middle layer – c cartilages, smooth muscles and aereolar connective tissue • Inner layer- ciliated columnar epithelial cells

22. Functions of trachea • Support and patency • Mucociliary escalator • Cough reflex • Warming, humidifying and filtering of air.

23. Bronchi and bronchioles

24. Lungs • Lungs are fibrous elastic sacs that are expanded and compressed by movements of the rib cage and diaphragm during breathing. • Cone shaped organs in thoracic cavity • A pair of lungs are separated by the heart which is situated in mediastenum

25. Lobes

26. Pleura alveoli Serous membrane Functional unit of lungs • Serous membrane covering both the lungs

27. Pulmonary circulation

28. Respiratory muscles • Intercoastal muscles - 11 pairs • External intercoastal muscles • Internal intercoastal muscles • Diaphragm • Dome shaped • Consists of central tendon and muscle fibres • Stimulated by phrenic nerves

29. Respiration / pulmonary ventilation • 12-15 cycles of respiration per minute • Cycle of respiration contains 3 phases • Inspiration • Expiration • Pause

30. Mechanism of respiration Inspiration Expiration

31. Diffusion of gases • Diffusion of gases occurs due to difference in the partial pressures across semi-permeable membrane (Pressure gradient) Lower pressure Higherpressure

32. External respiration It is exchange of gases by diffusion between the alveoli and the blood

33. Internal respiration • Exchange of gases between capillary blood and tissue cells

34. Respiratory volumes • Tidal Volume (about 500 ml) This is the amount of air which passes into and out of the lungs during each cycle of quiet breathing • Inspiratory reserve volume (2000-3300 ml) This is the extra volume of air that can be inhaled into the lungs during maximal inspiration. • Expiratory reserve volume (1000 - 1100 ml) This is the largest volume of air which can be expelled from the lungs during maximal expiration.

35. Respiratory volumes • Residual volume (1200 ml) This cannot be directly measured but is the volume of air remaining in the lungs after forced expiration. • Alveolar ventilation This is the volume of air that moves into and out of the alveoli per minute = (TV- anatomical dead space) x respiratory rate = (500-150) x 15 = 5.25 litre / min

36. Respiratory capacities • Vital capacity (4000-5000 mL) This is the maximum volume of air which can be moved into and out of the lungs: VC = Tidal volume + IRV + ERV Factors affecting vital capacity • Age • Sex • Body size • Body position • Athletes • Pregnancy • Exercise • Pathological Condition

37. Significance of vital capacity • To assess the lung function test • To assess the prognosis of respiratory disease • To assess the physical fitness of athletes Total lung capacity It is the total volume of air a person can hold in the lungs after a forceful exhalation TLC = VC + RV = 4600 + 1200 = 5800 ml

38. Transport of respiratory gases • Oxygen • 98.5% of blood O2 present in combination with haemoglobin as oxyhaemoglobin • 1.5% of blood O2 dissolved in plasma water Hb + O2 Hb-O2(Bright red colour)

39. Factors affecting dissociation of oxyhaemoglobin • Increased carbondioxide content of tissue fluid • Raised temperature • 2,3-diphosphoglycerate (2,3-DPG)

40. carbondioxide It is transported by 3 major mechanisms • 70% of blood CO2 is transported in the form of bicarbonate ions (HCO3-) in plasma carbonic anhydraseCO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO−3 • 7% of CO2 is dissolved in the plasma • 23%of CO2 is carried in erythrocytes as carbaminohaemoglobin CO2 + Hb ⇌ HbCO2

41. Transport of gases

42. Regulation of respiration Respiration is generally involuntary • Nervous regulation • Medulla oblongata • Inspiratory centre • Expiratory centre • Pons • Apneustic centre • Pneumotaxic centre • Chemical regulation (chemoreceptors) • Conc of CO2 in blood • Conc of H+ ion or pH in blood • Conc of O2 in the blood

44. Other factors influencing respiration • Speech • Singing • Emotional displays (crying, laughing, fear) • Drugs (sedatives, alcohol) • Sleep

45. Artificial respiration Def: The restoration or stimulation of respiration Two main methods of artificial respiration are • Manual methods • Shafer’s method • Sylvester’s method • Eve’s rocking method • Mouth to mouth method • Instrumental methods • Drinker’s method • Bragg Paul’s method • Cardiopulmonary resuscitation

46. Different manual methods of resuscitation

47. Respiratory diseases • Infectious and inflammatory diseases • Common cold and influenza • Sinusitis • Tonsillitis • Pharyngitis • Laryngitis • Dyptheria • Hay fever (allergic rhinitis) • Tumours

48. Diseases of bronchi • Acute bronchitis • Chronic bronchitis • Asthma Disorders of lung • Emphysema • Pneumonia • Lung abscess • Tuberculosis

49. references • Tortora – Anatomy and Physiology textbook • Ross and Wilson – Human Anatomy and Physiology textbook • Mahesh Prasad et al., Human Anatomy and PhysiologyII (Niraliprakashan) • S.B.Bhise and Yadav Human Anatomy and PhysiologyII (Niraliprakashan)