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(HS) Biology 12 > 10.1 The Blood Vessels > Flashcards

10.1 The Blood Vessels Flashcards

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1
Q

What are the 3 types of blood vessels?

A

arteries, capillaries, veins

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2
Q

What do all 3 vessel types have?

A

an inner endothelium

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3
Q

What is an endothelium?

A

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

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4
Q

What do all blood vessels require?

A

like other tissues, they require oxygen and nutrients

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5
Q

What do arteries do?

A

carry blood away from the heart to the capillaries

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6
Q

What do capillaries do?

A

permit exchange of material with the tissues

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7
Q

What do veins do?

A

return blood from the capillaries to the heart

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8
Q

What are the 3 arterial walls?

A

inner (endothelium)
middle
outer

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9
Q

Describe the middle layer of the artery.

A

the thickest layer and consists of smooth muscle that can contract to regulate blood flow and blood pressure

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10
Q

Describe the outer layer of the artery.

A

fibrous connective tissue near the middle layer, but it becomes loose connective tissue at its periphery

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11
Q

What is the largest artery in the human body?

A

aorta

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12
Q

What does the aorta do?

A

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

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13
Q

What are arterioles?

A

small arteries just visible to the naked eye

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14
Q

What is the inner layer of arterioles?

A

endothelium

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15
Q

Describe the middle layer of arterioles?

A

composed of some elastic tissue but mostly of smooth muscle with fibres that encircle the arteriole

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16
Q

What happens when the muscle fibres of arterioles contract?

A

the vessel has a smaller diameter (is constricted)

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17
Q

What happens when the muscle fibres of arterioles are relaxed?

A

the vessel has a larger diameter (is dilated)

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18
Q

How do arterioles affect blood pressure?

A

the greater the number of vessels dilated, the lower the blood pressure

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19
Q

What do capillaries join together?

A

arterioles to venules

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20
Q

What is the structure of capillaries?

A

extremely narrow, with thin walls composed only of a single layer of endothelium with a basement membrane

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21
Q

What are capillary beds and where are they present?

A

networks of many capillaries, and are present in nearly all regions of the body

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22
Q

Why is the cornea of the eye capillary-free?

A

so light can pass through

23
Q

How do the cells of the cornea obtain nutrients?

A

by diffusion from the tears on the outside surface, and from the fluid on the inside surface

24
Q

What are capillaries’ role in homeostasis?

A

an exchange of substances takes place across their thin walls

25
Q

What diffuses out of capillaries?

A
  • oxygen and nutrients (ie. glucose) diffuse out of capillary into the tissue fluid that surrounds cells
  • some water

*any excess is picked up by lymphatic vessels

26
Q

What is the relative consistency of tissue fluid dependent on?

A

capillary exchange

27
Q

What are anastomoses?

A

each capillary bed has arteriovenous shunts (called anastomoses) that allow blood to go directly from arterioles to venules, bypassing the bed

28
Q

What do contracted precapillary sphincter do?

A

prevent the blood from entering the capillary vessels

29
Q

What are venules and what do they do?

A

they are small veins that drain blood from the capillaries and then join to form a vein

30
Q

How is the structure of veins compared to artieries?

A

the walls of veins and venules have the same 3 layers as arteries, but there is less smooth muscle and connective tissue

THEREFORE, THE WALL OF A VEIN IS THINNER THAN THAT OF AN ARTERY

31
Q

What do veins often have?

A

valves

32
Q

What do valves do?

A

allow blood to flow only toward the heart when open and prevent blood from flowing backward when closed

33
Q

Where are valves found?

A

in the veins that carry blood against the force of gravity, especially the veins of the lower limbs

34
Q

How is blood flow kept moving in the arteries?

A

by the pumping of the heart

35
Q

How is blood flow kept moving in the veins?

A

primarily due to skeletal muscle contraction

36
Q

What will happen if valves become damaged?

A

blood may begin pooling in the veins, causing them to enlarge and be visible as varicose veins

*most commonly occurs in the lower legs of older individuals

37
Q

How do veins act as a blood reservoir?

A

because their walls are thinner, they can expand to a greater extent, at any time 70% of the blood is in the veins

38
Q

What happens if blood is lost due to bleeding?

A

nervous stimulation causes the veins to constrict, providing blood to the rest of the body

39
Q

What are the largest veins?

A

venae cavae, which include the superior vena cava, and the inferior vena cava

both veins deliver oxygen-poor blood into the heart

40
Q

Where do smaller arteries branch off from?

A

the aorta, and eventually the form a large number of arterioles

41
Q

Approximately how wide is the aorta?

A

25 mm

42
Q

Approximately how wide are arterioles?

A

0.5 mm in diameter

43
Q

Approximately how wide are capillaries?

A

8-10 micrometers

44
Q

What is the total surface area of capillaries in the human body?

A

6000 m^2

45
Q

Why do arteries have a thicker wall than veins?

A

they have a larger middle layer

46
Q

Do veins or arteries have a larger holding capacity?

A

veins because they are generally larger in diameter

47
Q

What diffuses into capillaries?

A

wastes (ie. carbon dioxide)

48
Q

What can the heart and other vessels of the circulatory system be thought of in terms of capillaries?

A

the means by which blood is conducted to and from the capillaries, because the capillaries serve the cells

49
Q

When are capillary beds completely open?

A

only certain capillary beds are completely open at any given time

ie. after eating, capillary beds that serve the digestive system are mostly open, and those that serve the muscle are mostly closed

50
Q

What is postprandial somnolence?

A

the sleepiness that people feel after eating

51
Q

What can cause postprandial somnolence?

A
  • a decreased blood flow to the brain after meals

- hormones released by the digestive tract

52
Q

What is the blood supply to the brain maintained under?

A

most physiological conditions (including ingestion of heavy meals)

53
Q

Describe the blood flow through a capillary bed.

A

a capillary bed forms a maze of capillary vessels that lies between an arteriole and a venule

when precapillary sphincter muscles are relaxed, the capillary bed is open, and blood flows through the capillaries

when sphincter muscles are contracted, blood flows through a shunt (anastomosis) that carries blood directly from an arteriole to a venule

as blood passes through a capillary in the tissues, it gives up oxygen

therefore, blood goes from being oxygen-rich in the arteriole, to being oxygen-poor in the vein

(HS) Biology 12 (46 decks)

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