Respiratory System

1. Respiratory System Prof. Ji-Cheng Li Department of Histology and Embryology

2. Objectives • Components of the conducting and respiratory portions of the respiratory system. • Wall structure and key distinguishing features of the trachea and the various segments of the bronchial tree. • Structure of the alveolar wall and components of the gas-blood barrier. • Structure of the type I, II alveolar cells.

3. Components Nasal cavity The pharynx (digestive system) The larynx The trachea The bronchi The lung

4. 1.Nasal cavity (study by yourself) Ep: stratified squamous epi. LP: sebaceous and sweat gland vestibular region respiratory region olfactory region Ep: pseudostratified ciliated columnar epi. LP: vascular network Olfactory cells Supporting cells Basal cells Ep: olfactory epi. LP: serous gland (Bowman gland, olfactory gland)

8. 2. Trachea and main bronchi Structure: • Mucosa • Submucosa • Adventitia

9. (1) Mucosa : Epithelium Pseudostratified ciliated columnar epithelium • Ciliated cell • Goblet cell • Brush cell • Basal cell • Small granule cell

11. Epithelium Figure 17-6: Ciliated respiratory epithelium

12. ciliated cell • with cilia • To provide a sweeping motion from the farthest reaches towards larynx

13. Goblet cell • to synthesize and secrete mucus • the secretion covers the epithelium surface

14. Brush cell -columnar, microvilli, -EM: RER, no granules -function: not very clear i. become into ciliated cell ii.receive sensory stimuli

15. Small granule cell (neuroendocrine cell) -EM: dense-core granules -Function: secret hormones to regulate contract of SM and secretion of gland i. 5-hydroxytryptamine(serotonin) ii. Calcitonin

16. Basal cell stem cell

18. (2) Submucosa LCT, containing mixed glands with diffuse LT and LN SIg A = secretory component (secreted by epithelum cell) + Ig A ( produced by plasma cell)

19. (3) Adventitia: cartilage ring: 16-20 “C ” shaped circular ligament: elastic fiber posterior part (membrane part): SM, elastic fiber, tracheal gland

20. 3. Lung ---paired organ, located in thoracic cavity

21. General structure: ---capsule: visceral layer of pleura- serous membrane ---parenchyma: all branches of bronchi and alveoli ---interstitia

23. Conducting portion: bronchi →intrapulmonary bronchial tree (lobar bronchial tree, segmental bronchi and small bronchi) →small bronchi →bronchioles →terminal bronchioles • Function: inspire air (cleaned, moistened, warmed)

24. Respiratory portion respiratory bronchioles →alveolar duct →alveolar sac → alveoli Function: gas exchange

25. 1) Conducting portion ① bronchi→small bronchi (fromlobar bronchi to small bronchi) • mucosa: Pseudostratified ciliated columnar epithelium -epithelium : thinner -goblet cell: number ↓ -lamina propria: thinner, -SM ↑ • submucosa:gland ↓ • adventitia:cartilage ↓

26. ② bronchiole: • diameter< 1mm • pseudostratified ciliated columnar epithelium • goblet cell, Gland, cartilage↓ or disappear • smooth muscle ↑ • circular mucosa plica ↑

27. *pulmonary lobule: one bronchioles and its all branches and all alveoli cone or pyramidal-shape 0.1 cm in diameter

28. *Asthma • Allergy--"the epidemic of the 21st century". • Asthma is a serious disease that affects the lungs and the airways that deliver air to the lungs.

29. ③ terminal bronchiole: Diameter < 0.5 mm ---goblet cell, gland, cartilage disappear ---SM: form a whole layer of circumferential SM ---Wall: • simple ciliated columnar epithelium two types of cells

30. i.   ciliated cell ii.  secreting cell: Clara cell non-ciliated and contain rich secretory granules (proteolytase) function: • dissolve the mucus • undifferentiated cell→ ciliated cell

32. Clara cell

33. Summary: Changes of conduction portion • The cartilages become irregular,and are smaller. • The amount of muscle in the bronchial wall increase. • Glands become fewer,and are absent in the bronchioles. • The epithelium become thinner.

34. bronchi →small bronchi bronchiole terminal bronchiole

36. 2) respiratory portion ①     respiratory bronchiole • simple columnar or cuboidal epithelium • smooth muscle less

37. ②  alveolar duct: ---wall: alveoli or alveolar sac opening simple cuboidal epithelium or squamous epithelium

38. ③   alveolar sac: ---many alveoli open to it

39. ④   alveoli: ---with opening alveolar sac 0.2mm in diameter, 300-400 million/per lung, total area: 70-80mm2 ---wall squamous epithelium

41. Summary

42. Respiratory bronchiole Alveolar duct Alveolar sac Alveoli

43. Epithelium of Alveoli • type I alveolar cells: • squamous, • cover 95% of the alveolar surface • type II alveolar cell • cuboidal • cover 5% of the alveolar surface

44. ---type I alveolar cell: EM: • plasmalemmal vesicles • tight junction Function: constitute the blood-air barrier

45. ---type II alveolar cell: secretory cells • contain osmiophilic multilamellar bodies • to release the surfactant to lower the surface tension • differentiate into type I alveolar cells.

46. EM: secreting granules: osmiophilic multilamellar body -0.1-1.0 um contains: phospholipid, glycosaminoglycan protein surfactant

48. alveolar septum: Ct , elastic and reticular fibers Fibroblast, macrophage, plasma cell, mast cell capillary: endothelium + basement membrane

50. Elastic fiber