10.1 The Blood Vessels

Question 1

circulatory system

Answer 1

type of organ system containing heart and blood vessels responcible for moving blood and substances through body

Question 2

define arteries, capillaries, veins

Answer 2

arteries: carry oxygen rich blood away from heart to capillaries
capillaries: permit exchange of materials with tissues
veins: return oxygen poor blood from capillaries to heart

Question 3

what is the endothelium

Answer 3

simple squamous epithelium attached to a connective tissue basement membrane that contains elastic fibres

Question 4

what is a simple squamous epithelium

Answer 4

single layer of flat cells in contact with the basal lamina (one of the two layers of the basement membrane) of the epithelium
often permeable and occurs where small molecules need to pass quickly through membranes via filtration or diffusion.

Question 5

describe the layers of the arteries

Answer 5

innermost: endothelium
middle: thickest layer, smooth muscles that contract to regulate blood flow and blood pressure
outer: fibrous connective tissue near middle layer, lose connective tissue at its periphery

Question 6

what is the aorta

Answer 6

largest artery in human body about 25mm in diameter

carries oxygen rich blood from the heart to other parts of the body

Question 7

what are the arterioles and describe its layers

Answer 7

small arteries visible to the naked eye about 0.5mm in diameter

inner: endothelium
middle: elastic tissue but mostly smooth muscle fibres that encircle arteriole

Question 8

what is the relation between the arterioles and blood pressure

Answer 8

when muscles fibres contact there is a smaller diameter, what muscle fibres relax there is a bigger diameter

• whether arterioles are constricted/dialated affects blood pressure
• greater the number of vessels dialted lower the bp

Question 9

how does blood flow in the arteries and veins

Answer 9

arteries: blood flow through pumping heart
veins: blood flow due to skeletal muscle contractions

Question 10

how does blood get to the heart from the veins

Answer 10

• veins and venules take oxygen poor blood from the capillary beds to the heart
• first venules (small veins) drain blood from capillaries and then join to form a vein
• blood flow in veins due to skeletal muscle contractions

Question 11

describe the layers of a vein

Answer 11

same as artery but less smooth muscle and connective tissues

Question 12

what are the valves

Answer 12

veins have valves that prevent blood from flowing backwards when closed and only allow blood to flow towards heart when opened

Question 13

what is varicose veins

Answer 13

when valves in veins become damaged because of age, or disease, does not work and blood pools in the veins causing them to be enlarged and visible
old ppl legs have this

Question 14

why do veins act as a blood reservoir

Answer 14

-walls of veins are thinner and can be expanded to a greater extent, so 70% of blood is in veins

Question 15

what do veins do when blood is lost due to bleeding

Answer 15

-nervous stimulations causes veins to constrict providing more blood to the rest of the body

Question 16

what are the largest veins in the body

Answer 16

superior vena cava (20mmwide) and inferior vena cava (35mm wide)

Question 17

what do the capillaries do

Answer 17

• join arterioles to venules
• contribute to homeostasis because exchange of substances takes place across their thin walls
• oxygen and nutrients (glucose) diffuse out of capillary into tissue fluid that surrounds cell
• waste (CO2) diffuse into capillary, water leave capillary
• excess is picked up by lymphatic vessels

Question 18

describe capillaries (3)

Answer 18

• 8 to 10 microm wide
• composed of single layer of endothelium with basement membrane
• vast networks abt 6000m surface area

Question 19

why is the cornea of the eye different than other parts of the body

Answer 19

almost capillary free so light can pass through, cells in cornea obtain nutrients from diffusion from tears on outside surface and fluid from inside surface

Question 20

what are anastomoses

Answer 20

arteriovenous shuts that allow blood to go directly from arterioles to venules bypassing the capillary bed

Question 21

what is the purpose of contracted precapillary sphincter muscles

Answer 21

prevent blood from enterring capillary vessels

Question 22

what is postprandial somnolence

Answer 22

sleepiness after eating

Question 23

what happens in capillary beds after you finish eating

Answer 23

capillary beds that serve thedigestive system are mostly open and those that serve the muscles are mostly closed
-only certain capillary beds are completely open at any given time