T3: Circulatory System (cont.) Flashcards
What is the normal blood flow rate of humans?
5L/min
What is the vital function of the cardiovascular system?
Chemical and gaseous exchange between blood and interstitial fluid.
across capillary walls
What is the function of capillaries?
transport gases, nutrients and waste products.
What are the three types of capillaries?
- continuous
- fenestrated
- discontinuous
What is the function of continuous capillaries?
- permit diffusion of water, small solutes and lipid soluble materials into the surrounding interstitial fluid
- prevent the loss of blood and plasma cells
What is the function of fenestrated capillaries?
Exchange of water and solutes (as large as small peptides) between plasma and interstitial fluid.
Where are continuous capillaries located?
all tissues except:
- epithelia
- cartilage
Where are fenestrated capillaries located?
- Kidneys: glomerulus
- GI tract: gut
Where are sinusoidal capillaries located?
- liver
- bone
- spleen
- endocrine glands (pituitary, adrenal glands)
What is microcirculation comprised of?
- arterioles
- capillaries
- venules
- terminal lymphatic vessels
What is a precapillary sphincter? What is its function?
- a circular band of smooth muscle at the entrance to the capillary
- regulates number of perfused capillaries
How do substances pass through the capillary wall?
- diffusion (O2, CO2)
- filtration
- osmosis
What is fluid movement across capillary walls determined by?
- hydrostatic pressure
- osmotic pressure
What is an arteriovenous anastomose? What is its function?
- direct connections between arterioles and venules
- allows blood to bypass the capillary bed and flow directly into the venous circulation
What is the function of capillary beds?
allow gas, nutrient and waste exchange
What is the function of arterioles (in relation to capillaries)?
- regulate capillary hydrostatic pressure
- influence capillary fluid exchange
How do venules play a role in regulating capillary hydrostatic pressure?
Sympathetic innervation of larger venules can alter venular tone which plays a role in regulating capillary hydrostatic pressure.
What is the function of valves?
- keep blood flowing towards the heart
- allow blood flow against the force of gravity