Exam 2 – cardio Ch 16 Flashcards
What is the function of microcirculation?
Important in the transport of nutrients to tissues
Site of waste product removal
Over 10 billion capillaries with surface area of 500-700 square meters perform function of solute and fluid exchange
How does the heart know how much blood to pump out of arteries?
How much venous blood flow returns
Heart pumps whatever comes to it
What is the structure of capillary wall?
Composed of unicellular layer of endothelial cells Surrounded by a basement membrane
What is the diameter of a capillary?
4-9 microns
How do solute and water move across capillary wall?
Intercellular cleft
By plasmalemma vesicles
What is the intercellular cleft?
Thin-slit, curving channel that lies at top of figure between adjacent endothelial cells
What do plasmalemma vesicles play a role in?
Endocytosis
Transcytosis
Why is it important that RBCs are biconcave?
Capillaries are smaller than RBCs so RBCs use concave characteristic and bend in order to move into capillary
What are the different types of capillaries?
Continuous
Fenestrated
Sinusoid
What are continuous capillaries?
Harder to get materials through
Continuous membrane
What are fenestrated capillaries?
A lot of fluid passes through
Ex: kidney
What are sinusoid capillaries?
Great big spaces
Nothing holding in blood
Ex: spleen
How does molecular size affect passage of molecules across the capillary wall?
The width of capillary intercellular slit pores is 6-7 nanometers
The permeability of the capillary pores for different substances varies according to their molecular diameters
What do capillaries in different tissues have extreme differences in?
Permeabilities
How do solutes and fluids cross the capillary wall?
Most important means by which substances are transferred between plasma and interstitial fluid is by diffusion
How do lipid soluble substances diffuse?
Directly through cell membrane of capillaries
CO2 and O2
How do lipid insoluble substances diffuse?
Cross capillary walls via intercellular walls
H20, Na, Cl, and glucose
What do concentration differences across capillaries enhance?
Diffusion
Look at relative permeability of muscle capillary pores to different-sized molecules chart
Look at relative permeability of muscle capillary pores to different-sized molecules chart
What is space between cells called?
Interstitium
What is fluid in the interstitium called?
Interstitial fluid
What are the two major types of solid structures in the interstitium?
Collagen fibers
Proteoglycan filaments
What are the purpose of collagen fibers in interstitium?
Provide most of tensional strength of tissues
What are proteoglycan filaments?
Coiled molecules composed of hyaluronic acid
What is almost all fluid in interstitium in the form of?
Gel
What is gel?
Fluid proteoglycan mixtures
Under normal conditions, is there a lot of free fluid?
No, very little free fluid
What is normal capillary hydrostatic pressure?
Approximately 17 mmHg