1. HISTOLOGY OF CIRCULATORY SYSTEM II

2. DIVISIONS
MACROVASCULATURE: > 0.1µm, large arterioles, muscular & elastic arteries, muscular veins
MICROVASCULATURE: < 0.1µm, arterioles, capillaries, post capillary venules
Exchange vessels

3. TISSUE COMPONENTS Endothelium Muscular tissue
Connective tissue (Elastic elements)

4. STRUCTURAL PLAN OF BLOOD VESSELS
TUNICA INTIMA
Endothelium
Basal lamina
Sub endothelial connective tissue
Internal elastic lamina
TUNICA MEDIA
Smooth muscles
Elastic lamellae, reticular fibers
Ground substance elements
External elastic lamina

5. TUNICA ADVENTITIA
Collagen & elastic fibers
VASA VASORUM
Vessels of vessels
Arterioles, capillaries, venules in adventitia
INNERVATION
Sympathetic fibers (norepinephrine)
Vasoconstriction
Arteries in Skeletal Muscles- cholinergic vasodilator fibers

6. ENDOTHELIUM: Semi permeable barrier Nonthrombogenic surface;
Monitor bidirectional exchange
Nonthrombogenic surface;
heparin, tissue plaminogen activator & Von Willibrand factor
Regulate Vascular tone & Blood flow;
Contraction: endothelin 1 & ACE
Relaxation: NO & Prostacyclin
Inflammation & Local Immune response;
Adhesion of WBCs, expression of P-Selectin, Weibel Palade Bodies
Growth Factors;
VEGF in Vasculogenesis, Angiogenesis,
role of Angiopoeitins
Lipolysis
Produce Vasoactive substances
Thrombosis, emboli (Role of TPA)

7. VASCULAR SMOOTH MUSCLES
Present in all vessels EXCEPT capillaries and post capillary venules
Enclosed in basal lamina & connective tissue
Arranged helically
Connected by gap junctions
VASCULAR CONNECTIVE TISSUE
Variable proportion
Collagen, IV, III, I
Elastic fibers
Ground substance; heterogenous gel

8. Medical Application Arteriosclerosis
Thickening of walls of small arteries
Monkeberg’s calcific sclerosis
Atherosclerosis

9. LARGE ELASTIC ARTERIES
T. INTIMA
Intima is thicker; smooth muscles in sub endothelial connective tissue
Internal elastic lamina, though present not prominent
T. MEDIA
Concentric lamellae of elastic fibers (40-70)
Reticular fibers, smooth muscles
T. ADVENTITIA
Less developed

11. Arterial Sensory Receptors
Carotid & Aortic Sinus:
Baroreceptors
Tunica Media is thin--- allows distension
Afferent impulses via 9th cranial nerve
Vasomotor center in brain
Efferent adjust lumen to control BP
Carotid & Aortic Bodies:
Chemoreceptors
Para ganglia with rich capillary network
Glomus type I cells; dense core granules containing Dopamine, Ach
Supported by Satellite Type II cells
Ion channels in Glomus cells respond to Low Oxygen, High CO2 or Acidosis
Afferents to brain efferents to cvs or respiratory system