MUCOUS BLANKET AND SMELL .pptx

Smell

1. Mucociliary Blanket of Nose and Paranasal Sinuses Physiology of Smell Capt ; Pyae Htay Oo PG-1 ORL-HNS 1

2. Functions of nose tion of nose Respiration Air-conditioning of inspired air Protecting of lower airway ( mucociliary mechanism ) Vocal resonance Nasal reflex function Olfaction 2

3. Lining Membranes of internal Nose 1. Vestibule – It is lined by skin and contains hairs,hair follicles and many sebaceous glands. 2. Olfactory region- upper one third of lateral wall ( up to superior concha ),corresponding part of nasal septum and roof of nasal cavity form olfactory region. He re, mucous membrane is olfactory neuro- epithelium and pale in color. 3

4. 3.Respiratory region-Lower two third of nasal cavity form the respiratory region. -Here, mucous membrane shows variable thickness being thickest over the nasal conchae, especially at their end, and -Quite thick over the nasal septum but very thin in the meatuses and floor of the nose. 4

5. -It is highly vascular and also contains erectile tissues.It’s surface is lined by pseudostratified ciliated columner epithelium which contains plenty of goblet cells. -In the submucous layer of mucous membrane are situated serous, mucous,both serous and mucous secreting glands, the ducts of which open on the surface of mucosa. 5

6. 6

7. 7

8. Respiratory and Olfactory Membranes 8

9. Protection of lower Airway (1)Mucociliary mechanism Nasal mucosa is rich in goblet cells, secreting glands both mucous and serous. Their secretion forms a continuous sheet called mucous blanket spread over the normal mucosa. Mucous blanket consists of superficial mucous layer and a deep serous layer. 9

10. 10

11. Mucociliary flow is the main mechanical defence of the nasal mucosa because it physically cleans inspired air . Mucus flows from the front of nose to posterior. Mucus from the sinus joins the stream on lateral wall. 11

12. This stream flows through the middle meatus and then around the E tube orifice before being swallowed. The mucociliary transport system is made up of cilia of the respiratory epithelium as well as a mucous blanket. Floating on the top of cilia are constantly beating to carry it like a ‘conveyer belt’ toward the nasopharynx. 12

13. Figure . “Conveyor belt” mechanism of mucus blanket to entrap and carry organisms and dust particles. 13

14. Mucous blanket moves at a speed of 5–10 mm/min and the complete sheet of mucus is cleared into the pharynx every 10–20 min. Presence of turbinates is almost double the surface area to perform this function and a bout 600–700 mL of nasal secretions are produced in 24 hr. 14

15. Viscoelastic properties enable it to trap larger particles. This mechanical defence is predominant and expels filtered particles and debris into the nasopharynx and oropharynx as well as elimination through sneezing and coughing. 15

16. Ciliary action Beat frequency of cilia in body temp – 7-16 Hz It remains constant between 32 – 40 ℃ In mammals, cilia beat 10-20 times per second at room temperature. They have a rapid propulsive/effective stroke and a slow recovery stroke. 16

17. During propulsive phase, cilia are straight & tip engaged the viscous layer of mucus blanket. During recovery phase,cilia are bent over & lie in aqueous layer. The mucous blanket is propelled backward by metachronous movement of cilia. 17

18. In immotile cilia syndrome, cilia are defective and cannot beat effectively, leading to stagnation of mucous in the nose and paranasal sinuses and bronchi causing chronic rhinosinusitis and bronchiectasis . 18

19. Factors affecting ciliary action Drying, Excessive heat or cold - stop the ciliary action. - below 10 ℃ & >45 ℃, ciliary movements stop. Isotonic saline - preserved ciliary action but solution >5% & <2% paralysis of ciliary movement. Infections, allergy 19

20. pH - cilia beat above pH 6.4 - cilia beat function slightly in alkaline pH 8.5 Drugs -neurotransmitter – acetylcholine -↑ the rate - adrenaline - ↓ the rate Smoking, Noxious fumes like sulfur dioxide and carbon dioxide 20

21. Cilia The ultrastructure of all cilia remains the same , but nasal cilia are short. The surface membrane of a cilium encloses an organized ultrastructure. 21

22. The nine outer-paired microtubules enclose a single inner pair of microtubules. The outer pairs of microtubules are linked to one another by nexins and to the inner pair of microtubules by central spokes. In addition, outer pairs of microtubules have both outer and inner dynein arms that are made up of an ATPase. 22

23. Fig. Ultrastructure of cilia 23

24. (2)Enzymes and immunoglobulins Nasal secretions also contain an enzyme called muramidase (lysozyme) which kills bacteria and viruses. Mucus consists of compounds that are able to neutralize antigens through innate mechanisms, learned, and adaptive immunological responses. Immunoglobulin A (IgA ) and immunoglobulin E ( IgE ) are found on the surface, and they act whenever the mucosa is breached. 24

25. In most cases, bacterial allergens are destroyed, but there are other viruses and bacteria that require the activation of the cell-mediated immune responses. IgA is the main immunoglobulin in secretions and has distinctive characteristics. IgA has two subgroups, namely IgA1 and IgA2 . IgA1 with a monomeric structure, is frequent in serum while IgA2 with a dimer structure, is common in nasal secretions. Immunoglobulin A constitutes 70% of the total proteins in nasal secretions. 25

26. (3) Sneezing It is a protective reflex. Foreign particles which irritate nasal mucosa are expelled by sneezing. Copious flow of nasal secretions that follows irritation by noxious substances helps to wash them out. 26

27. The pH of nasal secretion is nearly constant at 7 . The cilia and the lysozyme act best at this pH. Alteration in nasal pH, due to infections or nasal drops, seriously impairs the functions of cilia and lysozyme. 27

28. Olfaction(Physiology of Smell) Smell is important for pleasure and for enjoying the taste of food. When nose is blocked, food tastes bland and unpalatable. Vapours of ammonia are never used to test the sense of smell as they stimulate fibres of the trigeminal nerve and cause irritation in the nose rather than stimulate the olfactory receptors. 28

29. Olfactory Region Olfactory region – Upper one-third of lateral wall of nasal cavity ( upto superior turbinate), corresponding part of nasal septum, and roof of nasal cavity Aera:200-400mm² with a density of approximately 5×10 receptor cells/mm² 29

30. 30

31. Olfactory Epithelium Lies in the superior part of each nasal cavity. Within this epithelium, contains 10-1000 million olfactory receptors. The olfactory epithelium consists of three kinds of cells: 1.olfactory receptors cells 2.supporting cells or sustentacular cells 3.basal cells 31

32. Olfactory receptors They are actually bipolar nerve cells derived from the CNS. There are about 100 million of these cells in the olfactory epithelium. The mucosal end of the olfactory cell forms a knob. From knob,4-25 olfactory cilia project into the mucus that coats the inner surface of nasal cavity. These projecting cilia form a dense mat in the mucus. These cilia react to odours in the air and stimulate the olfactory cells . 32

33. (2) Supporting cells The receptors cells in the olfactory epithelium are interspersed among supporting cells or sustentacular cells. Supporting cells are columnar epithelial cells. They provide physical support, nourishment and electrical insulation for olfactory receptors. They help detoxify chemicals that come in contact with the olfactory epithelium. 33

34. (3)Basal cells Basal cells are stem cells located between the bases of the supporting cells. They continually undergo cells division to produce new olfactory receptors, which live for only a month or so before being replaced. This process is remarkable – olfactory receptors are neurons, and mature neurons are generally not replaced. 34

35. Bowman’s glands and Olfactory mucus The space among the olfactory cells in the olfactory membrane are many small Bowman’s glands that secrete mucous onto the surface of the olfactory membrane— mucus is carried out to the surface of the epithelium by ducts. The secretion moistens the surface of the olfactory epithelium and dissolves odorants so that transduction can occur. When odorants molecules reach olfactory region, must interact with mucus overlying the receptor cells, produced by Bowman’s glands and adjacent respiratory mucosa (goblet cells). 35

36. Adrenergic, cholinergic, and peptidergic agents change the properties of mucus overlying the olfactory receptors. In the olfactory mucus-epithelial system, clearing odorants is equall as important as absorption. Olfactory mucus may exert a differential role in deactivating, removing, or desorbing odorants from the olfactory area. 36

37. 37

38. 38

39. Excitation of olfactory cells The portion of each olfactory cell that respond to the olfactory chemical stimuli is the olfactory cilia. The odorant substance on coming in content with the olfactory membrane surface, first diffuses into the mucous that covers the cilia. Then, it binds with receptor proteins in the membrane of each cilium and couples to G-protein. 39

40. Olfaction is mediated by G-protein coupled receptors in the cells which interact with a specific adenyl cyclase within neuroepithelium. Stimulus ( odours )>> Receptors(G-protein coupled receptor cell protein)>> cAMP pathway>> opening Na ion channels>> action potential>> excitation the olfactory neuron>> Olfactory nerve>> CNS 40

41. Olfactory Pathway Olfactory nerves -They carry sense of smell and supply olfactory region of nose. They are the central filaments of the olfactory cells and are arranged into 12–20 nerves which pass through the cribriform plate and end in the olfactory bulb. 41

42. C ribriform plate has multiple small perforation through which an equal number of small nerves pass upward from the olfactory membrane in the nasal cavity to enter the olfactory bulb in the cranial cavity. Olfactory bulb lies over the cribriform plate, separating the cranial cavity from the upper nasal cavity. 42

43. Both olfactory bulb and tract are anterior outgrowth of brain tissue from the base of the brain. Short axons from the olfactory cells terminate in multiple globular structures within the olfactory bulb called glomeruli. Each glomerulus is the terminus for dendrites from about 25 large mitral cells and about 60 smaller tufted cells, the cell bodies of which lie superior to the glomeruli in the olfactory bulb. 43

44. Mitral and tufted cells send axons through the olfactory tract to transmit olfactory signals to higher levels in the CNS. Mucus-cilia >>> Olfactory receptor cells >>> Axons of these cells>>> Glomeruli in olfactory bulb>>> Dendrites of mitral & tufted cells in bulb>>> Axons of mitral and tufted cells in tract>>> CNS. 44

45. 45

46. CNS Smell Pathway Olfactory tract enters the brain at the anterior junction between the mesencephalon and cerebrum . There, o lfactory tract divides into two pathways; Medially –the medial olfactory area(stria)of the brain stem-(very old olfactory system) Laterally- the lateral olfactory area(stria)- newer and less old system 46

47. Very old olfactory system , -medial olfactory stria >>Septal nuclei >>Hypothalamus (limbic system) -more primitive responses to olfaction ,salivation ,liking lips and primitive emotional drives to smell. 47

48. Lateral olfactory area-anteromedial portion of the temporal lobe (cerebral cortex) Less Old Olfactory System, - This is the only area of the entire cerebral cortex where sensory signals pass directly to the cortex without passing first through the thalamus. Prepyriform and pyriform cortex plus portion of amygdaloid nuclei>>limbic system (hippocampus) Learn control of food intake and aversion to food that have caused nausea and vomiting 48

49. The newer pathway, passes through the thalamus passing to the dorsomedial thalamic nucleus >>orbitofrontal cortex. Conscious perception and analysis of odour ( odour discrimination) 49

50. Olfactory Pathway 50

51. 51

52. 52

53. 53

54. Disorders of Smell It is essential for the perception of smell that the odorous substance be volatile and that it should reach the olfactory area unimpeded. The healthy state of olfactory mucosa and the integrity of neural pathways, i.e. olfactory nerves, olfactory bulb and tract and the cortical center of olfaction are necessary. 54

55. Anosmia is total loss of sense of smell while hyposmia is partial loss. They can result from nasal obstruction due to nasal polypi, enlarged turbinates or oedema of mucous membrane as in common cold, allergic or vasomotor rhinitis . 55

56. Parosmia is perversion of smell; the person interprets the odours incorrectly. Often these persons complain of disgusting odours . It is seen in the recovery phase of postinfluenzal anosmia. Intracranial tumour should be excluded in all cases of parosmia. 56

57. Olfactometry( Odour Measurement) Qualitative olfactometry , -Olfactory sense is assessed by taking a solution. -Following primary odours are usually tested : 1.Etherial –ether 2.Camphoraceous –camphor 3.Flora 1-salicyldehyde 4.Musky-phenyl acetic acid 5.Minty –mint 6.Pungent –formalin 7.Putrid-thiophenol 57

58. Quantitative Olfactometry - Measurement of olfactory sense is done with an olfactometer. -Olfactometry gives information about the following: 1.The extent of the field of smell 2.Gives an idea about patient’s acuity of smell 3.Possible parosmia(perverted smell) 58

59. THANKS FOR YOUR ATTENTION 59