1. VAN 504, Lecture 04
Systemic Histology: Study of Microscopic structure of organs of Respiratory and Digestive system

2. Respiratory System
The function of the respiratory system is to provide molecular oxygen for cellular oxidation and to remove carbon dioxide generated as a waste product of cell metabolism.
There must be vascular or circulatory transport AND air/gas transport
The pulmonary blood circulation transports gases to and from the alveoli of the lungs.

3. Functional Requirements
The Respiratory System has tubular components for air/gas conduction
Plus respiratory components for gas exchange.
Inspiratory pressure tends to collapse the conducting tubes. They must be held open.
Other essential functions include: warming; moistening; cleansing by removal of particulate matter; detoxification by absorption of harmful gases; and entrapment of harmful bacteria and viruses.

4. Conduction The nasal cavity is held open by bone and cartilage.
Most of the additional functions are carried out by pseudostratified columnar ciliated epithelial cells and goblet cells (mucous secretors) that line the airways. The cilia beat rhythmically in one direction only, moving debris and pathogen-laden mucous to the oropharynx and mouth where it is expectorated or swallowed.
Air temperature control is by the profuse capillary beds that are beneath the epithelium, and which warm or cool inspired air. Extensive venous plexi largely replace capillaries in the nasal cavities to modify air temperature

5. NASAL CAVITY 1.Vestibule. 2. Nasal Fossae (posterior portion of N.C.):
a- Olfactory portion.
b- Respiratory portion.
Nasal septum divides the nasal cavity into
two halves.

6. VESTIBULE OF NASAL CAVITY
Lining: is lined with skin.
1- Epidermis (Keratinized stratified Squamous epithelium).
2- Dermis.
3- Vibrissae.
4- Sebaceous glands.
5- Sweat glands.

7. RESPIRATORY AREA OF NASAL CAVITY
Epithelium:
Pseudo-stratified ciliated columnar epithelium with goblet cells (Respiratory epithelium).
(B) Lamina propria (Corium):
1- C.T.: richly (highly) vascularized.
2- Large arterial plexuses & venous sinuses
(Highly vascular),especially in region of conchae &
anterior part of nasal septum.
3- Many seromucous glands (acini).
4- Abundant lymphoid elements:
Including lymphoid nodules, plasma cells & mast cells.

8. RESPIRATORY EPITHELIUM
Pseudo-stratified columnar ciliated
epithelium with goblet cells.
E/M: 6 cell types ( all touch the basement m)
1- Ciliated columnar cells
2- Goblet cells
3- Basal cells: are stem cells
4- Brush cells (small granule mucous cells) are sensory receptors or degranulated goblet cells.
5- DNES cells (small granule cells) (K cells)
are neuroendocrine cells
6- Serous cells

9. RESPIRATORY MUCOSA OF NASAL CAVITY

10. RESPIATORY EPITHELIUM

11. OLFACTORY MUCOSA

12. OLFACTORY AREA OF NASAL CAVITY.
Structure:
Olfactory epithelium:
Pseudo-stratified columnar epith.
1- Supporting (sustentacular) cells
2- Olfactory cells (olfactory nerve cells)
1 & 2 are connected together by junctional complexes.
3- Basal cells.
(B) Lamina propria: contains:
1- Highly (richly) vascularized loose to dense C.T.
2- Bowman’s glands (serous acini).
3- Axons of olfactory nerve cells + Schwann cells.
4- Rich vascular plexus.
5- Numerous lymphoid elements.

13. OLFACTORY MUCOSA

14. OLFACTORY MUCOSA

15. LARYNX Mucous membrane: 1- Epithelium: (2 types: a- respiratory epith.
b- non-keratinized str.sq. epith.)
2- Lamina propria
There are 2 pairs of shelf-like mucosal folds
1- Vestibular folds:
Are immovable.
L/M: a- Resp. epith.
b- Lamina propria:
Loose C.T. with seromucous glands
lymphoid elements & adipose cells.
2- VOCAL FOLDS (CORDS): have:
a- Vocal ligament: bundles of parallel
elastic fibers (dense regular elastic C.T.).
b- Vocalis muscle: Skeletal muscle.

16. Cartilages:
1- Hyaline cartilages:
Thyroid,
Cricoid,
Body of arytenoids.
2- Elastic cartilages:
Epiglottis,
Corniculate,
Cuneiform,
Tips of arytenoids.
(C) Extrinsic and intrinsic muscles: all are skeletal.
(D) Ligaments.

17. LARYNX

18. LARYNX
Glands G
Thyroid cartilage

19. LARYNX

20. TRACHEA The wall of trachea is formed of: Mucosa. Submucosa.
Adventitia.

21. MUCOSA OF TRACHEA Epithelium: Respiratory epithelium Lamina propria:
Loose, fibroelastic C.T. containing:
a- Lymphoid elements (e.g. lymphoid nodules & lymphocytes).
b- Mucous & seromucous glands.
(3) Elastic lamina:
Dense layer (thick bundle) of elastic fibers.
It separates lamina propria from submucosa.
N.B. Mucosa is non-folded except posteriorly.

22. SUBMUCOSA OF TRACHEA ADVENTITIA OF TRACHEA Contents:
1- Dense irregular fibroelastic C.T. (others:loose)
2- Numerous mucous & seromucous glands.
3- Lymphoid elements.
4- Rich blood & lymph supply.
ADVENTITIA OF TRACHEA
Contents:
1- Fibroelastic C.T.
2- C-shaped rings (12-16) of hyaline cartilage.
Trachealis muscle (bundle of SMF) bridges (connects)
the open ends of each C-shaped ring of cartilage.
Perichondrium of C-shaped rings of hyaline cartilage
are connected together by dense fibroelastic CT.

23. TRACHEA

24. TRACHEA

25. Primary BRONCHUS
Generally have the same histological appearance as the trachea.
BRONCHUS

26. INTRAPULMONARY BRONCHUS

27. INTRAPULMONARY BRONCHUS

28. INTRAPULMONARY BRONCHUS

29. INTRAPULMONARY BRONCHUS

30. INTRAPULMONARY BRONCHUS

31. INTRAPULMONARY BRONCHUS

32. Secondry & Tertiary BRONCHI)
1- Mucosa.
2- Muscle coat.
3- Submucosa.
4- Adventitia.

33. NTRAPULMONARY BRONCHUS
1.Mucosa:
It has longitudinal mucosal folds.
a- Epithelium: Respiratory epith.
b- L.P.:
Fibroelastic C.T.
(loose C.T. rich in elastic fibers).
It contains seromucous glands.
“ “ lymphoid elements.
N.B. No elastic lamina.
2 . Muscle coat (complete):
Two distinct layers of SMF spirally arranged in opposite direction
(crisscrossing bundles of spirally arranged
SMF).

34. 3.Submucosa: It contains: a- Seromucous glands. b- Lymphoid elements.
4. Adventitia:
Contents: a- Loose C.T.:
Contains radially arranged elastic fibers to
connect with counterparts of neighbouring
bronchial tree.
b- Irregular plates of hyaline
cartilage (complete layer).
c- Solitary lymphoid nodules.
d- Seromucous glands.

35. BRONCHIOLES 1- Preterminal ( 1ry ) Bronchioles (Bronchioles).
3- Respiratory ( 3ry ) Bronchioles.

36. PRETERMINAL BRONCHIOLES
less in diameter. Each bronchiole supplies pulmonary lobule Mucosa: has longitudinal folds: (A) Epithelium: S. col. ciliated Epith. with occasional goblet cells only in the initial segments. Then, s. cuboidal partially ciliated with occasional Clara cells (in smaller pret. Br.) (B) Lamina propria: C.T. (rich in elastic fibers) (2) Smooth muscle: hellicaly arranged SM layers. (3) Adventitia: loose fibroelastic C.T. N.B. No cartilage, No glands, No lymphoid nodules.

37. Terminal Bronchioles Similar structure, but: Epithelium:
Simple cuboidal partially ciliated epithelium
With Clara cells.
Each supplies lung acinus.

38. BRONCHIOLE

40. Respiratory Bronchioles
Similar structure to terminal bronchioles
But their walls is interrupted by the presence
of few pulmonary alveoli.
RESPIRATORY BRONCHIOLE

41. RESP. BRONCGIOLE & ALVEOLUS

42. TERMINAL & RESPIRATORY BRONCHIOLES

44. Clara cells

45. Clara cells

46. CLARA CELLS Structure: columnar cells (non ciliated).
Dome-shaped apices with microvilli.
Numerous apical secretory granules
(of glycoproteins).
Abundant rER.
Function:
1- Protect the bronchiolar epith. By their
secretion.
2- Degrade toxins in inhaled air by cytochrome p-450 enzymes (produced by sER)
3- Divide to regenerate the bronchiolar epith
4- May produce surfactant-like material.

47. ALVEOLAR DUCTS The wall of alveolar duct consists almost of
pulmonary alveoli.
Lining Epith.: Squamous alveolar cells
(2) Lamina propria:
a- Elastic & Reticular fibers.
b- Smooth muscle cell surrounds the opening
of alveolus (small muscle knob)

49. PULMONARY ALVEOLI Interalveolar septa.
They are small out pouchings of respiratory
bronchioles, alveolar ducts & alveolar sacs.
Interalveolar septa.
*Blood-air barrier ( Blood-gas barrier)
*Alveolar epithelium.
*Lung macrophages (alveolar macrophages)
*Alveolar pores.

50. Blood-air barrier

51. ALVEOLAR EPITHELIUM

52. Interstitium of interalveolar septa
1. Pulmonary Capillaries:
-The richest capillary network in the body
- Continuous blood capillaries
- Endothelium shows numerous
pinocytotic vesicles.
2. Interstitial C.T.:
a- C.T. Fibers: elastic & reticular.
b- C.T. Cells: Fibroblasts, Macrophages,
Mast cells, Leucocytes.

53. BLOOD-GAS BARRIER
It is the region of the interalveolar septum that is traversed by O2 and CO2
Components:
1- Thin layer of surfactant.
2- Type I pneumocyte.
2- Fused basal laminae of type I pneumocytes &
endothelial cells of the pulmonary capillary.
3- Endothelial cells of the pulmonary capillary.

54. PLEURA 1.Parietal pleura. 2.Visceral pleura.
formed of two layers: Parietal and visceral. It is formed of simple squamous mesothelium. The two layers are separated by serous fluid. The visceral layer has sub-epithelium loose C.T that extends into the lung tissue