1. Department of Histology and Embryology
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. 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. (neuroendocrine cell)
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. bronchi →intrapulmonary bronchial tree
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 bronchi→small bronchi (from lobar bronchi to small bronchi) mucosa:
1) Conducting portion
① bronchi→small bronchi
(from lobar 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. ---wall: alveoli or alveolar sac opening
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. ---with opening alveolar sac
④   alveoli:
---with opening alveolar sac
0.2mm in diameter,
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. osmiophilic multilamellar body
EM:
secreting granules:
osmiophilic multilamellar body 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

52. (respiratory memebrane) ---components: a layer of liquid
Blood-air barrier
(respiratory memebrane)
---components:
a layer of liquid
type I alveolar cell and basement membrane Ct
capillary endothelial cell and basement membrane

54. alveolar pore: 10-15 um ---balance the air-pressure between alveoli
---lober pneumonia - bacteria or inflammatory spread through the pore

55. alveolar marcophage:
---dust cell:
phagocytose carbon or duct particles

56. alveolar macrophages:

57. heart failure cell:
lung edema
the alveolar marcophage phagocytose RBC
digest the hemoglobin
hemosiderin (pigment)
accumulated them within macrophage

58. Pulmonary blood vessels
Pulmonary artery and vein
Function: contain venous blood to be oxygenated
Bronchial artery and vein
Function: nourish the bronchial tree

59. Review Test
1. Which of the following statements concerning terminal bronchioles is TRUE?
(A) They are part of the conducting portion of the respiratory system
(B) They function in gas exchange
(C) They do not contain ciliated cells
(D) They have cartilage plates present in their walls
2. Alveoli in alveolar sacs possess all of the following components EXCEPT?
(A) elastic fibers in their walls
(B) a simple squamous lining epithelium
(C) reticular fibers in their walls
(D) smooth muscle in their walls

60. Homework
1. Compare the structure of bronchiole with that of terminal bronchiole.
2. Describe the morphology and function of type I cell and type II cell in lung in detail.
3. What is the air-blood barrier (or respiratory memebrane) composed of ?

61. Reference book and website
成令忠主编.组织学与胚胎学.第4版.北京；人民卫生出版社.1995
Junqueira LC ,Carneiro J,Kelley RO.Basic Histology.9th ed.New York;Appleton & Lange.Stamford,Connecticut,2005.
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