Lecture 6 Unit 1 Flashcards
how do oxygen and nutrients move out of the blood?
by crossing the capillary wall and entering the interstitial fluid (ISF)
how do carbon dioxide and metabolic waste products move?
in the opposite direction
how long would body capillaries be if they were placed end to end?
60,000 miles and cross sectional area would be 5,000 cm^2
how long is the average capillary? and the lumen diameter?
capillary- 1 mm
lumen- 8 micrometers
what is the blow flow velocity in a capillary?
0.1 cm/sec
what is the concentration or density of capillaries in a given tissue proportional to?
the tissue’s metabolic activity
what does the term capillary bed refer to?
a network of capillaries where exchange of materials with the tissue cells can take place
how far is every cell tissue usually from a capillary?
~1.3 cell diameters
when is diffusion efficient?
only when diffusion distances are short
how do most substances move?
by diffusion
what can cross intercellular clefts?
pores, water and most small substances cross the capillary wall by diffusion through these pores
what can cross endothelial cell membranes?
some small molecules and gases can diffuse or be transported across the endothelial cell layer
what can cross fenestrations?
large molecules can pass easily through the fenestrations
what are the 3 routes for capillary exchange?
- intercellular clefts
- endothelial cell membranes
- fenestrations
where are continuous capillaries found?
found in lungs, skeletal muscle, and connective tissue
where are fenestrated capillaries found?
kidneys, endocrine glands, small intestine
what does fenestration mean?
little windows (70-100 nm)
where are sinusoidal capillaries found?
liver, spleen, bone marrow, and anterior pituitary gland
What two ways do materials pass through capillary walls?
active or passive transport
what is diffusion?
movement of molecules or ions from a region of higher concentration to one of lower concentration until equilibrium is reacher
is diffusion passive or active?
passive
what is bulk flow?
bulk flow refers to the movement of a fluid from a region of higher pressure to one of lower pressure
is bulk flow an active or passive process?
passive
what is transcytosis?
substances enter pinocytotic vesicles, move to endothelial cells via endocytosis, and exit on opposite side via exocytosis
is transcytosis active or passive?
active
What is fluid exchange between ISF and capillaries based on?
bulk flow
what are the two major forces that tend to push fluid out of capillaries and into ISF?
- blood hydrostatic pressure
- interstitial fluid osmotic pressure
what does blood hydrostatic pressure (BHP) do?
pushes fluid out through the capillary pores
what does interstitial fluid osmotic pressure (IFOP) do?
pulls fluid out via osmosis; this pressure is very small compared to the BHP
what are the two forces that pull fluid INTO the capillaries?
- blood colloid osmotic pressure (BCOP)
- interstitial fluid hydrostatic pressure
what does blood colloid osmotic pressure (BCOP) do?
the BCOP is the result of differences in protein concentration between plasma and ISF which tends to pull water from the ISF and into the capillaries
what is the interstitial fluid hydrostatic pressure (IFHP)?
the IFHP is due to the pressure exerted by interstitial fluid, but it is normally very small
what is the net filtration pressure?
the difference between the inward and outward pressures
what is the equation for the NFP?
NFP= (BHP + IFOP) - (BCOP+IFHP)
what determines the fluid movement across the capillary wall?
the BHP and BCOP
what does filtration result in?
a constant flow of fluid that washes over the tissue cells at the arterial end of the capillary carrying nutrients and oxygen with it
what does reabsorption result in?
a return of fluid to the capillary at the venous end, herby depositing wastes into the venous system
under normal conditions how much fluid leaves the capillaries?
slightly more fluid leaves than enters the capillaries (3L/day)
what do the lymphatic vessels do?
they absorb this excess fluid and return it to the circulatory system
