Week 1 - CVS Histology Flashcards
List the 3 layers making up the walls of arteries and veins, from the innermost to outermost layers.
Tunica intima
Tunica media
Tunica adventitia
The tunica media is thicker in veins. True or false?
False - thicker in arteries
What are the components of the tunica intima?
Endothelium
Subendothelial layer
Internal elastic lamina
Give one example of an elastic artery.
The aorta.
What is contained within the walls of the tunica adventitia of elastic and muscular arteries?
Vasa vasorum
What is the function of vasa vasorum? Why are they needed?
Supply the artery wall with blood.
Wall too thick to rely on diffusion from the blood in the lumen.
What is the tunica media of elastic arteries made up of?
40 - 70 elastic membranes
How do arteriole walls differ from elastic lamina walls?
Arterioles - tunica media has just 1 - 3 layers, and there is very little adventitia.
Elastic arteries - thick tunica media and significant adventitia with vasa vasorum.
What is the key feature of metarterioles?
Pre-capillary sphincters
What is a pre-capillary sphincter?
Smooth muscle cell encircles capillary at the point at which it branches off from the metarteriole. Contracts and relaxes to control blood flow into the capillary.
RBCs are almost as large as a capillary lumen. What benefit does this have?
Reduces path length for diffusion
Is blood through capillaries fast or slow? Why?
Slow - allows longer time for nutrient exchange
Describe a capillary wall
Endothelium and basement membrane only
What are the 3 types of capillary?
- Continuous
- Fenestrated
- Discontinous/sinusoidal
What feature leads a capillary to be referred to as a “continuous” capillary?
The endothelium in the wall is continuous
What does it mean if a capillary is fenestrated?
There are interruptions in the endothelium, bridged by a thin membrane
Where may you find discontinuous capillaries? Why?
Liver, spleen and bone marrow
Large gaps in the endothelium which allow whole cells through
What sort of cell may surround continuous or fenestrated capillaries?
What is their function?
Pericytes
Divide into myocytes or fibroblasts
In which vessels do valves begin to appear?
Venules
What are valves formed from?
Extensions of the tunica intima
What are venae commitantes?
Pairs of veins which lie either side of an artery.
The pulsating of the artery aids venous return.
Are venae commitantes wrapped in a single sheath, or is each vessel individually wrapped?
Single sheath
Compare and contrast the structure of large veins and elastic arteries.
Veins:
Wall thinner - thin tunica intima and thin tunica media
Lumen wide and irregular
Valves
But generally similar in size and structure
Veins have a thin tunica media. Which are the exceptions, and why?
The superficial veins of the legs - need muscle to resist gravity
List the vessels in order of size, starting with the elastic arteries and ending with the large veins.
Elastic arteries Muscular arteries Arterioles Metarterioles Capillaries Post-capillary venules Venules Medium veins Large veins
