Blood Vessels Chp. 19 (Test 2) Flashcards
What is the normal route of blood flow?
heart –> arteries –> arterioles –> capillary network –> venules –> veins –> heart
What is a portal system?
where blood flows through two consecutive capillary beds before returning to the heart. example: liver and kidneys.
What are the three layers of artery and vein walls and describe them?
tunica externa: holds blood supply for vessels.
tunica media: changes diameter of vessels.
tunica intima: exposed to blood. veins contain valves.
What are arterioles?
smallest of arteries. smooth muscle is one cell thick.
What is a metarterioles?
short vessels, link between arterioles and capillary beds. contains precapillary sphincter.
What is precapillary sphincters?
bands of muscle. open and close based on tissues need of blood (oxygen)
What is a capillary?
smallest blood vessels
What are the three types of capillaries?
1) continuous capillaries- most abundant
2) fenestrated capillaries- windows/pores. quick exchange. kidneys, intestines, endocrine glands.
3) sinusoid capillaries- leaky. in liver, bone marrow, spleen, and adrenal glands.
What is a vein?
carry blood from capillary beds to lungs. contain a larger lumen.
Why do veins have valves?
to prevent backflow
What is blood pressure?
the force that blood exerts against the wall of arteries.
What is the systolic pressure number?
peak arterial pressure during ventricular systole.
What is the diastolic pressure number?
lowest arterial pressure during ventricular diastole.
What is normal blood pressure for a young adult?
120/80
What is pulse pressure?
systolic - diastolic = pulse pressure
What is mean arterial mean pressure(MAP)?
pressure that propels blood to tissues. average pressure throughout cardiac cycle. used as a risk assessment tool. influenced by gravity.
MAP = diastolic pressure + 1/3(pulse pressure)
What is venous return?
flow of blood back to heart.
What are the five ways make venous return possible?
1) pressure gradient
2) gravity
3) skeletal muscle pump
4) respiratory pump
5) smooth muscle
How does pressure gradient effect venous return?
blood flows from high pressure to low pressure
How does the skeletal muscle pump effect venous return?
veins get squeezed which pushes blood toward the heart.
How does the respiratory pump effect venous return?
there is slightly higher pressure in abdominal cavity then thoracic cavity while inhaling, diaphragm contracts downward causing increase in thoracic volume, and decrease in thoracic pressure. blood flows faster from abdominal cavity to thoracic cavity.
How does that smooth muscle effect venous return?
smooth muscle constricts to increase venous return. occurs under sympathetic nervous system stimulation.
What happens if the skeletal muscle pump is idle too long while a person is upright?
the end diastolic volume lowers, cardiac output, decreased flow to the brain, causing syncope or fainting
