2. Vascular System
Dr. Samar Asker

3. Arteries
Large Arteries: aorta
caries blood from the
heart.
Medium-sized arteries:
cary blood to organs
Small Arteries
(arterioles):regulate blood
flow to capillaries.

4. General Structure of Blood Vessels
T.Intima
T.Media
T.Adventitia

5. Large
arteries
Aorta

6. Tunica intima 10%
simple squamous
epithelium
Subendothelial C.T.
rich in elastic fiber.
Undifferentiated
Internal elastic lamina.

7. Tunica Media70%:
Fenestrated elastic
membrane (40-70
layer)
Smooth muscle in()
Collagen fibers.

8. Tunica adventitia 20%:
 Loose CT rich in elastic
fibers.
 Contain vasa vasora which
is a small blood vessels
that supply the outer part
of T. media & T.
adventitia

9. 10%
70%
20%

10. Medium sized artery
Wall
Thick wall.
Lumen
Narrow lumen.
Not contain blood after
death.
No valve in the lumen.
Flow of
Blood
It has a rapid flow of
arterial blood.
Medium sized vein
Thin wall.
Wide lumen usually contains
blood after death.
Valve present.
It has a slow flow of venous
blood.

11. T.
Intima
Medium sized artery
Thick.
Folded due to
internal elastic
lamina.
Medium sized vein
Thin.
Not Folded.

12. Medium sized artery
T. Media
Thick.
Some elastic membrane.
External elastic lamina may
be present
Adventitia
Thin and contain elastic
fibers.
Medium sized vein
Thin.
Formed of few smooth
muscle fibers.
No external elastic lamina.
Thicker
No elastic fibers

15. Peripheral circulation
Arterioles give plexus of
capillaries to supply tissues

16. The Blood capillaries

17. Narrow vessels
formed by rolling
of an endothelial
cell
Length: 0.251mm
Diameter: 8 μm.

18. 1 layer of endothelial cells
Resting on basement membrane
Which split to enclose pericytes

19. Types of
capillaries

20. Continuous capillaries:
Continuous endothelium
(no pores)
Continuous basement
membrane
Sites:
C. T., bone, brain , skin
and exocrine glands.

21. Fenestrated or visceral:
Endothelium has pores closed
by membrane or diaphragms
except renal capillaries
Site:
Intestine
Endocrine glands.
Glomerular capillary of kidney,

22. Sinusoidal capillaries:
Dilated irregular capillaries,
(5-40) µm.
Fenestrated endothelium have
pores without diaphragms.
The basement membrane
either non continuous or absent.
Macrophages extend pseudopodia inside () the endothelial
cells to engulf any foreign body.

23. Sites :
In bone marrow:Carry blood cells, to the
circulation.
In spleen:
Carry stored blood cells
to circulation & filter the
blood.

24. liver: carry
plasma proteins to
blood
In endocrine
glands: carry
hormones to blood.