Exam 2 - Chapters 21-23

Question 1

Arteries

Answer 1

Carry blood AWAY from the heart, to other organs.

Question 2

Arterioles

Answer 2

Smallest form of arteries

(Last stop before reaching the capillaries)

(progresses from large elastic arteries leaving the heart, those divide into medium sized arteries, these divide into small arteries, which eventually divide into arterioles).

Question 3

Capillaries

Answer 3

Site of gas exchange

(Transition point between arteries [oxygenated blood coming AWAY from the heart] and veins [deoxygenated blood going TOWARD the heart])

Question 4

TUNICA INTERNA

Answer 4

• Innermost layer, inner lining of blood vessels; in direct contact with the blood.
• The innermost portion of the tunica interna is made of endothelial tissue (aka, endothelium).

Question 5

BASEMENT MEMBRANE

Answer 5

Very good tensile strength, rich in collagen fibers.

Question 6

TUNICA MEDIA

Answer 6

Middle layer, made up of smooth muscle, also has some elastic fibers.

KNOW the smooth muscle/tunica media is very thin on the veinous side, but pretty thick on the arterial side. THIS IS WHERE vasoconstriction and vasodilation occurs, making the lumen bigger or smaller (greater ability to vasoconstrict/vasodilate in the arteries than in the veins)

Question 7

TUNICA EXTERNA

Answer 7

OUTERMOST LAYER, made up of elastic and collagen fibers.

Question 8

Similarities and Differences in Blood Vessels

Answer 8

Both arteries and veins have the same three layers (tunica interna, tunica media, tunica externa), but the TUNICA MEDIA is MUCH THICKER in ARTERIES than it is in the veins.

ALSO, two extra layers of elastic lamina within the arterial wall, which give the arteries much greater ability to recoil as they are stretched.

Question 9

SMOOTH MUSCLE in the TUNICA MEDIA layer…

Answer 9

Is innervated by ANS sympathetic fibers that provide for:

vasoconstriction (decrease in lumen diameter)

vasodilation (increase in lumen diameter)

Question 10

Elastic Arteries

Answer 10

SIZE: Largest arteries in the body.

TUNICA INTERNA: Well-defined internal elastic lamina.

TUNICA MEDIA: Thick and dominated by elastic fibers and well defined external elastic lamina.

TUNICA EXTERNA: Thinner than tunica media.

FUNCTION: Conduct blood from heart to muscular arteries.

Question 11

Muscular Arteries

Answer 11

SIZE: Medium-sized arteries

TUNICA INTERNA: Well-defined internal elastic lamina.

TUNICA MEDIA: Thick and dominated by smooth muscle; thin elastic lamina.

TUNICA EXTERNA: Thicker than tunica media.

FUNCTION: Distribute blood to arterioles.

Question 12

Arterioles

Answer 12

SIZE: Microscopic (15µm - 300µm in diameter).

TUNICA INTERNA: Thin, with a fenestrated internal elastic lamina that disappears distally.

TUNICA MEDIA: One or two layers of circularly oriented smooth muscle; distalmost smooth muscle cell forms a precapillary sphincter.

TUNICA EXTERNA: Loose collagenous connective tissue and sympathetic nerves.

FUNCTION: Deliver blood to capillaries and regulate blood flow from arteries to capillaries.

Question 13

Capillaries

Answer 13

SIZE: Microscopic; smallest blood vessels (5µm-10µm).

TUNICA INTERNA: Endothelium and basement membrane.

TUNICA MEDIA: None.

TUNICA EXTERNA: None.

FUNCTION: Permit exchange of nutrients and waste between blood and interstitial fluid; distribute blood to postcapillary venules.

Question 14

Postcapillary Venules

Answer 14

SIZE: Microscopic (10µm-50µm in diameter).

TUNICA INTERNA: Endothelium and basement membrane.

TUNICA MEDIA: None.

TUNICA EXTERNA: Sparse.

FUNCTION: Pass blood into muscular venules; permit exchange of nutrients and waste between blood and interstitial fluid and function in white blood cell emmigration.

Question 15

Muscular Venules

Answer 15

SIZE: Microscopic (50µm-200µm in diameter).

TUNICA INTERNA: Endothelium and basement membrane.

TUNICA MEDIA: One or two layers of circularly oriented smooth muscle.

TUNICA EXTERNA: Sparse.

FUNCTION: Pass blood into veins; act as reservoirs for accumulating large volumes of blood (along with postcapillary venules).

Question 16

Veins

Answer 16

SIZE: Range from .5mm-3cm in diameter.

TUNICA INTERNA: Endothelium membrane and basement membrane; no internal elastic lamina; contain valves; lumen much larger than accompanying artery.

TUNICA MEDIA: Much thinner than in arteries; no external elastic lamina.

TUNICA EXTERNA: Thickest of the three layers.

FUNCTION: Returns blood to heart, facilitated by valves in veins in limbs.

Question 17

What is the function of the elastic fibers and smooth muscle in the tunica media of arteries?

Answer 17

The primary role of the smooth muscle cells (which extend circularly around the lumen like a ring encircles your finger) is to regulate the diameter of the lumen; the elastic fibers help it to vasoconstrict (decrease diameter of lumen; sympathetic activation) and to vasodilate (increase diameter of lumen; decrease in sympathetic activation).

Question 18

How are the elastic arteries and the muscular arteries different?

Answer 18

ELASTIC ARTERIES

TUNICA MEDIA = Thick, but dominated by elastic fibers; *external lamina is well defined; *SIZE = largest of the arteries; TUNICA EXTERNA = thinner than tunica media.

vs. MUSCULAR ARTERIES

TUNICA MEDIA = Thick, but dominated by smooth muscle; external lamina is thin; SIZE = medium-sized; TUNICA EXTERNA = thicker than tunica media.

Question 19

What structural features of capillaries allow the exchange of materials between blood and body cells?

(PART I)

Answer 19

PART I

The capillaries have no tunica media or tunica externa; instead, capillary walls are composed of a single layer of endothelial cells and a basement membrane. Thus, a substance in the blood only has to pass through one cell layer to reach the interstitial fluid and tissue cells. (Exchange only occurs through walls of capillaries and the beginning of venules - the walls of other blood vessels are too thick.)