4.7 - Blood Vessel Histology Flashcards
The blood vascular system is composed of
Heart
arteries and arterioles
capillaries
veins and venules
What has the largest and least amount of blood distribution in the body?
largest = systemic veins and venules
Smallest = systemic capillaries
Function of the circulatory system
Pump and carry blood with O2, remove CO2, electrolytes, hormones, and metabolites
Arteries carry
oxygenated blood away from the heart
Veins carry
deoxygenated blood towards the heart
What are the layers of blood vessels?
(inner to outer)
Tunica intima
Tunica media
Tunica adventitia
Describe tunica intima
- Innermost layer of blood vessels
- endothelium + basal lamina
- Internal elastic lamina
- Subendothelial layer
Describe tunica media
- Middle layer
- smooth muscle
- elastic fibers and elastic lamellae
- Reticular fibers
- Pericytes
Describe tunica adventitia
- Outermost layer
- Loose collagen and elastic fibers
Describe vasa vasorum
- In the tunica adventitia
- Vascular supply to the walls of large blood vessels
Define innervation
Blood vessels contain both sympathetic and parasympathetic nerves to control blood vessel size by constriction or dilation
Describe capillaries
Endothelium - tight junctions
Basal lamina
Pericytes
What are pericytes?
- Present in capillaries
- sit on outside of basal lamina
- contain contractile proteins
- can transform into other cell types
- Change diameter of capillary wall
Capillary diameter is large enough to fit how many erythrocytes at a time?
1
What are the types of capillaries?
Continuous - somatic
Fenestrated - visceral
Discontinuous - sinusoidal
Describe continuous capillaries
- Also called somatic
- Most common type
- Endothelial cells have numerous pinocytotic vesicles
Where can you find continuous (somatic) capillaries?
Muscle
CT
Exocrine glands
Nerve tissue (blood brain barrier)
Describe fenestrated (visceral) capillaries
- Large fenestrae (L. window) in walls of endothelial cells
- Holes in capillary
What are the types of fenestrated capillaries and where are they located?
Diaphragm fenestrated (tighter than non-diaphragm)
- Kidney, intestine, and endocrine glands
Non-diaphragm-fenestrated
- renal glomerulus
Describe discontinuous (sinusoidal) capillaries
- large diameter
- Fenestrations w/o diaphragm - some w/ large gaps
Where can you find discontinuous (sinusoidal) capillaries?
Liver and hematopoietic organs
Describe arterioles
- Small arteries
- 1-2 concentric layers of smooth muscle
- Thin tunica intima and subendothelial layer
- NO external elastic lamina
- Thin adventitia
Describe muscular arteries
- Prominent internal elastic laminae
- external elastic laminae
- Vaso vasora
Describe elastic arteries
- Thick tunica intima and subendothelial layer
- Internal and external elastic lamina but indistinguishable
- Tunic media
- tunica adventitia underdeveloped
- vasa vasora
What’s the thickest layer of arteries?
Tunica media
What’s the thickest layer of veins?
Tunica adventitia
Describe venules
- Thin walls
- Pericytes in small postcapillary venules
- Usually accompany arteriole
Where are valves located in small and medium sized veins
in the lumen
Describe large veins
- Thick tunica media
- Well-developed tunica adventitia
- NO valves
Describe metarterioles
- Arterioles w/ discontinuous layer of smooth muscle
- Slows down blood flow into capillaries
- Maintains pressure differences between arterial and venous systems
Where can you find metarterioles?
In the mesentery and brain
Describe precapillary sphincters
- Complete ring of smooth muscle at junction of metarterioles and capillaries
- Constriction STOPS blood flow into capillaries
Where can you find precapillary sphincters?
Mesentery and brain
- associated with metarterioles
Describe arteriovenous anastamoses
- Shunts blood from arteries to veins
- Bypasses capillary beds
- In skin and mesentery
Describe portal systems
- 2 capillary beds w/ arterioles or venules between them
Where can you find the arteriol portal system
Kidney glomerulus
Where can you find the venous portal system
In the liver
