HUBS192 Lecture 7 - Cardiovascular System, Circulatory System Anatomy, Capillaries and Lymphatics Flashcards
what is the function of capillaries?
site of exchange between blood and tissues
what 3 things does the function of capillaries demand?
1) very thin walls
2) large total CSA of capillary bed
3) slow & smooth blood flow
what determines slower blood flow of capillaries?
large total CSA area of the capillary bed compared to arterioles means much slower blood flow
what is a capillary composed of?
endothelial cells
what are endothelial cells?
specialised cells that form the barrier between the blood and the tissues that wrap around to form junctions creating the thin cellular tube
what is the lumen?
the inside space of a tubular structure (an opening)
what is the size of a lumen of a capillary?
8-10μm
how do you get from the lumen to the surrounding tissue?
by passing through the endothelial cell either by passive diffusion or active transport (continuous capillary because the cell forms a continuous interface barrier)
what happens when pre-capillary sphincters constrict?
they stop blood going into the side branches forcing the blood to shot through the central channel and straight out the other side
what is a vascular shunt?
a thoroughfare channel from an arteriole to a venule controlled by involuntary muscle
how does the structure of capillaries vary according?
varies according to the rate of exchange needed and how controlled the exchange must be
what are the 3 types of capillaries and how leaky are each of them?
1) continuous (tight=controlled)
2) fenestrated (leaky)
3) sinusoidal (very leaky)
what is the diameter of a continuous capillary?
8-10μm (lumen is the the diameter of a red blood cell)
what are endothelial cells?
specialised type of epithelial cell
what is another name for the basement membrane?
basal laminar
what is the basement membrane?
layer of connective tissue that is produced by the epithelial cells to help stick themselves down to the underlying connective tissue
what are the 3 components of a continuous capillary?
1) basement membrane
2) endothelial layer (tunica intima)
3) intercellular cleft
where are continuous capillaries found?
in skeletal muscle and cardiac muscle
what is the diameter of fenestrated capillaries?
8-10μm
what are fenestrations?
small openings/holes
where are fenestrated capillaries found?
in the kidney and in the small intestine
what is the diameter of a sinusoidal capillary
30-40μm
what 2 components make up a sinusoidal capillary?
1) incomplete basement membrane
2) intercellular gap
what is the function of an incomplete basement membrane?
to allow cells in the surrounding tissues can be wedged up in the sinusoidal openings
what is different about sinusoidal capillaries compared to continuous and fenestrated capillaries?
sinusoidal capillaries is more about nutrient exchange of plasma and blood rather than gas exchange
what are the 3 ways you can get out of the lumen of a continuous capillary?
1) diffusion through membrane (lipid-soluble)
2) movement through intercellular clefts (water-soluble)
3) transport via vesicles
what are the 4 ways you can get out of the lumen of a fenestrated and a sinusoidal capillary?
1) diffusion through membrane (lipid-soluble)
2) movement through intercellular clefts (water-soluble)
3) movement through fenestrations (water-soluble)
4) transport via vesicles
what are the 4 functions of the lymph vascular system?
1) drains excess tissue fluid & plasma proteins from tissues and returns them to the blood
2) filters foreign material from the lymph
3) ‘screens’ lymph for foreign antigens & responds by releasing antibodies & activated immune cells
4) absorbs fat from intestine and transports to blood
