1. HISTOLOGY OF CIRCULATORY SYSTEM III

2. MEDIUM SIZED, MUSCULAR ARTERIES
T. INTIMA
Subendothelial layer thin
Prominent internal elastic lamina
T. MEDIA
Smooth muscles- 40 layers
Elastic fibers
T. ADVENTITIA
Connective tissue, vasa vasorum, lymphatics

5. SMALL ARTERIES & ARTERIOLES
<0.5mm lumen
Thin subendothelial connective tissue
Int. elastic lamina absent in small arterioles
T. Media: smooth muscle layer
Adventitia is thin
Hypertension

6. CAPILLARIES Diameter : 5-7 µm
Single layer of endothelium; permit metabolic exchange
Function in groups- Capillary Beds
Richness conforms to metabolic activity of tissue
Structure and pulsatile flow of blood through capillaries and thoroughfare channel.

8. TYPES
Continuous
Fenestrated
Sinusoidal

9. CONTINUOUS CAPILLARIES
No fenestrations, complete basal lamina
Pinocytic vesicles
Location:
Muscles, nervous tissue, exocrine glands

10. FENESTRATED CAPILLARIES
Transcellular openings (80nm)
Limited by cell membrane
Covered by diaphragm ( thinner than cell membrane, proteoglycans)
In endocrine glands
Kidneys etc

11. SINUSOIDAL CAPILLARIES
Diameter 30-40µm
Endothelial cells discontinuous layer
Fenestrations without diaphragm
Incomplete basal lamina
Macrophages
Found in liver, hematopoietic organs

12. PERICYTES Cells at periphery of continuous capillaries
enclosed in own basal lamina
Mesenchymal origin
Actin, myosin– contractile properties
Role in repair process
Diabetic Microangiopathy

14. POST CAPILLARY VENULE Diameter 0.5-1mm
Endothelium + thin subendothelial connective tissue
Media– pericytes
MUSCULAR VEINS
Thin subendothelial layer, may be absent
Media: smooth muscles + reticular fibers
valves

15. Inflammation & Edema

17. LARGE VEINS Well developed intima Thin media Very thick adventitia
Further three layers
Smooth muscles

19. LYMPH VASCULAR SYSTEM LYMPH CAPILLARIES: Single layer of endothelium
Incomplete basal lamina
LYMPH VESSELS:
Structure similar to veins, thinner walls
LARGE DUCTS:
Similar to veins, smooth muscles

22. Medical Application
Metastasis
Lymph edema