Lecture 7: CIRCULATORY SYSTEM ANATOMY - PART 2 Flashcards
What is the function of capillaries?
Site of exchange between blood and tissues
What does the function of capillaries require?
Very thin walls, large total cross sectional area of capillary bed and slow and smooth blood flow
How does the total area of capillaries compare to arterioles?
Much larger which means much slower blood flow
What is found in a capillary?
Layer of endothelial cells, nucleus, red blood cells and intercellular (tight) junction
What is the size of a red blood cell?
8-10 micrometres
What is found in a capillary bed?
Terminal arteriole, precapillary sphincters, vascular shunt and post capillary venule
What is the terminal arteriole?
The end of the supply netwokk
What is included in the vascular shunt?
Metarteriole and thoroughfare channel
What is the post capillary venule?
Start of the drainage network
What are precapillary sphincters composed of?
Smooth muscle cells under involuntary control
What are precapillary sphincters able to do?
Constrict and prevent blood flowing into the capillary bed
What does the vascular shunt do?
Pushes blood straight from the supply to drainage without passing through the exchange network
What are the 3 types capillaries?
Continuous, fenestrated and sinusoidal
What are continuous capillaries?
Most widespread
What are fenestrated capillaries?
Leaky
What are sinusoidal capillaries?
Very leaky
What is the diameter of continuous capillaries?
8-10 micrometres (single file flow of RBC)
What is the most common form of capillary?
Continuous capillaries
What do continuous capillaries also have?
A surrounding basement layer of extracellular tissue produced by the endothelial cells which the substances must also pass through
what is the diameter of fenestrated capillaries?
8-10 micrometers (single file flow of RBC)
What do fenestrated capillaries have?
Porous openings called fenestrations
What is an example of fenestrated capillaries?
Glomerulus in the kidneys which filter the blood
What is the diameter of sinusoidal capillaries?
30-40 micrometres (multiple RBC flow)
What does the larger diameter of sinusoidal capillaries mean?
They are more likely to be involved in transport of nutrients and toxins rather than gases as RBC are further from the capillary wall
What are the size of the openings in sinusoidal capillaries?
Larger than fenestrations