18-1: Anatomy of vessels

Question 1

arteries

Answer 1

all vessels carrying blood away from the heart; have the thickest strongest walls composed of 3 tunics surrounding the lumen

Question 2

lumen

Answer 2

central open space that contains the blood

Question 3

tunic intima

Answer 3

innermost layer made of endothelial tissue (simple squamos epithelium)

Question 4

tunica media

Answer 4

middle layer made of smooth muscle and elastic fibers; the autonomic nervous system innervates this muscle

Question 5

tunica externa

Answer 5

outer covering composed to loosely woven collagen fibers that protect the blood vessel and anchor it to surrounding structures

Question 6

What are the major properties of arteries?

Answer 6

elasticity (expand to receive blood; as heart relaxes, elastic recoil propels blood forward: this elasticity allows blood to flow fairly smoothly)

contractility (ability to change diameter due to smooth muscle in artery walls)

Question 7

vasoconstriction

Answer 7

sympathetic stimulation causes the smooth muscle to contract and the lumen narrow

Question 8

vasodilation

Answer 8

widening of the lumen due to smooth muscle relaxation

Question 9

vasomotor tone

Answer 9

normal state of partial contraction

Question 10

elastic arteries

Answer 10

aka conducting arteries - large arteries that carry blood away from the heart (eg. aorta, pulmonary trunk)

Question 11

muscle arteries

Answer 11

aka distributing arteries - medium-sized arteries that deliver blood to specific organs (eg. renal artery); once inside, they branch into smaller vessels

Question 12

arterioles

Answer 12

smallest arteries, they deliver blood to the capillaries; blood flow to capillary beds is determined by arteriole diameter

Question 13

pulse

Answer 13

alternate expansion and recoil of elastic artery walls during each cardiac cycle. This pressure wave can be felt at any artery lying close to the skin; commonly taken at the radial artery

(pulse points are also called pressure points)

Question 14

capillaries

Answer 14

microscopic vessels connecting arterioles to venules

Question 15

How many layers do capillary walls have?

Answer 15

just one - tunica intima - walls are often only one layer of endothelial cells thick

Question 16

Blood moves very ___ through capillaries due to __.

Answer 16

slowly; narrow diameter (RBCs move through single file)

Question 17

There are rich capillary supplies in areas of ___.

Answer 17

high activity (though no cell is very far from capillary)

Question 18

What is the role of capillaries?

Answer 18

exchange of gasses and nutrients between blood and tissues

Question 19

capillary beds

Answer 19

extensive branching networks providing a large surface area for the exchange of gasses and nutrients; when metabolic needs are low, only a small part of the network is used

Question 20

What are some examples of tissues that lack capillaries?

Answer 20

cartilage, epithelium, cornea and lens of eye, tendons, ligaments

These tissues receive nutrients from blood vessels in nearby tissues

Question 21

veins

Answer 21

all vessels carrying blood back towards the heart

Question 22

venules

Answer 22

small vessels that collect blood from capillaries and drain into larger veins

Question 23

Compared to arteries, veins have __ walls, and their lumens are __; because of this, they can hold ___. Blood pressure in the veins is ___.

Answer 23

thinner, less elastic walls; wider lumens; large volume of blood (reservoir); low

Question 24

What are adaptations of veins to compensate for low pressure?

Answer 24

walls and large lumens result in little resistance to blood flow

valves in veins prevent backflow (blood can go upwards, but not slip back down)

Question 25

varicose veins

Answer 25

weak venous valves cause blood to pool in veins of the legs. This stretches venous valves, making them elastic and flabby. Superficial veins are especially suscepitble because of little support from surrounding tissue

causes: prolonged standing, obesity, pregnancy, heredity