Arteries, Capillaries, And Veins Flashcards
What is the function of arteries?
To convey blood at high pressure from the ventricles to the tissues of the body and lungs
What is another name for tunica intima?
Narrow lumen
What is the function of the tunica intima?
Maintains high blood pressure (80 to 120 MM Hg)
What is the function of the tunica externa/adventitia?
Outer layer of collagen that prevents the artery from rupturing under high pressure
What is the function of the tunica media?
Contains an inner layer of muscle in elastic fibers to maintain pulse flow (it can contract and stretch)
What are the functions of muscle fibers?
Contractor near the lumen which increases pressure between pumps and maintains blood pressure
What are the functions of elastic fibers?
Allow the walls of the arteries to stretch and expand upon the flow of a pulse through the lumen
What is elastic recoil?
Pressure that is exerted on an arterial wall is returned to the blood when the artery returns to its normal size
What is vasoconstriction?
When the circular muscles around the arteries resist the outward pressure and constrict
What is vasodilation?
The smooth muscles around the arteries relax
When does systolic blood pressure occur?
When the arteries experience the highest pressure during vasoconstriction
When does diastolic blood pressure occur?
When the pressure in the arteries is the slowest during vasodilation
What is the function of capillaries?
To exchange materials between the cells and tissues in blood traveling at low pressure (less than 10 MM Hg)
What are the diameter of capillaries?
~ 5 µm
Why is the capillary wall made of a single layer of cells?
To minimize the diffusion distance for permeable materials
What other structures aid in permeability in capillaries?
Basement membrane and pores
What can limit permeability of large molecules in capillaries?
The capillary wall maybe continuous with endothelial cells held together by tight junctions
In what type of tissues may the capillary wall be fenestrated?
In tissue is specialized for absorption (ex. intestines, kidneys)
What capillaries have open spaces between cells for permeability of large molecules?
Sinusoidal capillaries (ex. liver)
What materials are force from the bloodstream into the tissue fluid due to higher hydrostatic pressure?
Oxygen and nutrients (cell respiration)
What materials enter from the tissues into the bloodstream due to lower hydrostatic pressure?
Carbon dioxide and urea (cell waste)
What is the function of veins?
To collect blood from tissues and transport it to the atria of the heart
What is the function of the valves in veins?
Prevents backflow into stop blood from pulling at the lowest extremities
Why do veins have very wide lumen in their tunica intima?
To maximize blood flow for more effective return
