Blood Vessel

Question 1

Blood Vessels

Answer 1

dynamic structures - pulse, constrict, dilate, relax, proliferate

Form a closed delivery system that starts and ends with the heart

60,000 miles of blood vessels in the human body

Question 2

Three type of blood vessels

Answer 2

Arteries
Capillaries
Veins

Question 3

Arteries

Answer 3

carry blood away from the heart

arteries branch into arterioles which feed into the capillary beds of the body’s tissues and organs

in systemic circulation, arteries carry oxygen-rich blood

Question 4

capillaries

Answer 4

thin-walled structures with direct tissue contact, the sites of exchange

O2, CO2, nutrients, hormones, and waste are exchanged between blood and interstitial fluid

wall consists of thin tunica intima

most tissues have rich capillary supply - exceptions include tendons, ligaments, cartilage, epithelia

Question 5

veins

Answer 5

return blood to heart

from the capillary beds, blood drains into venules which then converge into larger veins until they return to the heart

in systemic circulation, veins carry oxygen poor blood

Question 6

Lymphatic system

Answer 6

recovers the fluid that leaks from the blood vessels

Question 7

Three walls of blood vessels

Answer 7

Tunica Intima

Tunica Media

Tunica Externa

Question 8

Tunica Intima

Answer 8

innermost layer, contacts the passing blood

• contains endothelium, the epithelium lines all vessels and reduces friction
• endothelium is continuous with the endocardial lining of the heart
• vessels larger than 1 mm in diameter - a subendothelial layer supports the tunica intima

Question 9

Tunica Media

Answer 9

middle layer, circularly arranged smooth muscle cells and sheets of elastin

• more robust in arteries
• Activity of the smooth muscle is regulated by sympathetic vasomotor nerve fibers and chemicals
• Vasoconstriction
• Vasodilation
• small changes in Vessel diameter greatly influence blood flow and blood pressure

Question 10

Vasoconstriction

Answer 10

smooth muscle contacts, and the lumen decreases

Question 11

Vasodilation

Answer 11

smooth muscle relaxes, and the lumen increases

Question 12

Tunica Externa

Answer 12

loosely woven collagen fibers that protect, reinforces, and anchor the vessel

• called “Tunica Adventitia”
• infiltrated by nerve fibers, lymphatic vessels, and a network of elastin fibers
• larger vessels, the tunica Externa contains vasa vasorum - a network of tiny blood vessels that nourish the vessel itself

Question 13

Elastic arteries

Answer 13

elastin present in all three tunica, but tunica Media contains the most

despite smooth muscle, relatively inactive as vasconstrictors

act as pressure reservoirs - expand/recoil as the heart ejects blood

elastic arteries “smooth” pressure and make blood flow fairly continuously - projection for smaller arteries

Question 14

Muscular Arteries

Answer 14

deliver blood to specific body tissues/organs

example: (brachial, radia, common iliac, posterior tibial arteries)

have thickest tunica Media
- more smooth muscle, less elastin tissue
- more active vasoconstrictors, less capable of stretch

Question 15

Aterioles

Answer 15

smallest arteries

larger arterioles have all three tunica - tunica Media is chiefly smooth muscle with minimal elastin

smaller arterioles are largely a single layer of smooth muscle around endothelial

diameter varies in response to neural, hormonal, and local chemical influences

arterioles constrict, the tissue is largely bypassed

when arterioles dilate, blood flow into the local capillaries increases dramatically

Question 16

Types of Capillaries

Answer 16

Continuous
Fenestrated
Sinusoid

Question 17

Intracellular clefts

Answer 17

gaps of un-joined membrane

• allow limited passage of fluids and small solutes

Question 18

Continuous

Answer 18

most common, less permeable

• abundant in skin, muscle, lungs, and the CNS
• structural basis for the blood-brain barrier

Question 19

Renestrated

Answer 19

larger fenestration or pores increases permeability

• abundant in kidneys, small intestine, areas of hormone secretion

Question 20

Sinusoid

Answer 20

occur in limited locations, most permeable

• found in liver, bone marrow, spleen, aredanl medulla
• have large intracellular clefts and irregular shapes
• contain macrophages to catch prey

Question 21

Capillary Beds

Answer 21

capillaries do not function independently - they form interweaving networks called capillary beds

in most regions, a terminal artiorole branches into 10 to 20 capillaries - the capillary beds

the capillary beds drains into a post capillary venules

blood flow through the capillary beds is controlled by the diameter of the terminal arteriole - this is altered by chemical conditions and vasomotor nerve fibers

secondary to changes in arterioles diameter, a capillary beds may be flooded with blood or it may be bypassed - important rerouting

Question 22

Microcirculations

Answer 22

how blood flows from an arterioles to venules through a capillary bed

• gases, nutrients, hormones, and waste are exchanged during microcirculation