Blood Vessels

Question 1

What is a LUMEN?

Answer 1

a hollow passageway through which blood flows.

Question 2

Why do arteries and arterioles have thicker walls than veins?

Answer 2

they are closer to the heart and receive blood that is surging at a far greater pressure

Question 3

What are the walls of arteries and veins mostly composed of?

Answer 3

living cells and their products (including collagenous and elastic fibers); the cells require nourishment and produce waste.

Question 4

In larger arteries, there is a thick, distinct layer of elastic fibers known as the what?

Answer 4

the internal elastic membrane (also called the internal elastic lamina)

Question 5

The internal elastic membrane (also called the internal elastic lamina) is located where?

Answer 5

at the boundary with the tunica media

Question 6

What are the 3 Tunics called?

Answer 6

Tunic interna, tunic media, and tunic externa

Question 7

Specifically in arteries, what decreases blood flow as the smooth muscle in the walls of the tunica media contracts, making the lumen narrower and increasing blood pressure?

Answer 7

Vasoconstriction

Question 8

What happens during vasodilation?

Answer 8

increased blood flow as the smooth muscle relaxes, allowing the lumen to widen and blood pressure to drop.

Question 9

vasoconstriction and vasodilation are regulated in part by small vascular nerves, known as ________ that run within the walls of blood vessels.

Answer 9

nervi vasorum, or “nerves of the vessel”

Question 10

Appearing wavy in slides (microscope), ______ separates the tunica media from the outer tunica externa in larger arteries.

Answer 10

the external elastic membrane (also called the external elastic lamina)

Question 11

Besides being innervated by the nervi vasorum, what else controls the vaso consticion/dilation of the blood vessels?

Answer 11

Hormones and local chemicals

Question 12

What is the outer tunic, the tunica externa (also called the tunica adventitia)?

Answer 12

It is a substantial sheath of connective tissue composed primarily of collagenous fibers.

Question 13

What is a blood vessel that conducts blood away from the heart.

Answer 13

An artery

Question 14

What type of artery is close to the heart and has the thickest walls, containing a high percentage of elastic fibers in all three of the tunics.

Answer 14

an elastic artery

Question 15

Why is an elastic artery is also known as a conducting artery?

Answer 15

because the large diameter of the lumen enables it to accept a large volume of blood from the heart and conduct it to smaller branches.

Question 16

What is a very small artery that leads to a capillary.

Answer 16

Arteriole

Question 17

With a lumen averaging 30 micrometers or less in diameter, ________ are critical in slowing down—or resisting—blood flow and, thus, causing a substantial drop in blood pressure.

Answer 17

arterioles

Question 18

What are the primary mechanisms for distribution of blood flow.

Answer 18

The vasoconstriction and vasodilation in the arterioles.

Question 19

Why are arterioles so important in terms of blood flow?

Answer 19

They are the primary site of both resistance and regulation of blood pressure.

Question 20

The exchange of gases and other substances that occur in the capillaries between the blood and the surrounding cells and their tissue fluid (interstitial fluid) is what?

Answer 20

A process called perfusion.

Question 21

A microscopic channel that supplies blood to the tissues themselves is called a _____.

Answer 21

Capillary

Question 22

Flow through capillaries is often described as ______.

Answer 22

a microcirculation, just big enough form an erythrocyte to get through.

Question 23

What are three major types of capillaries?

Answer 23

Continuous, fenestrated, and sinusoid capillaries. All differ according to their “leakiness”.

Question 24

What is a type of vessel that has structural characteristics of both an arteriole and a capillary?

Answer 24

Metarteriole

Question 25

Circular smooth muscle cells that surround the capillary at its origin with the metarteriole, tightly regulate the flow of blood from a metarteriole to the capillaries it supplies.

Answer 25

The precapillary sphincters

Question 26

What is an extremely small vein, generally 8–100 micrometers in diameter.

Answer 26

A venule

Question 27

What is a vein?

Answer 27

A blood vessel that conducts blood toward the heart.

Question 28

What is the capacity to distend (expand) readily to store a high volume of blood, even at a low pressure called?

Answer 28

capacitance

Question 29

What are capacitance vessels?

Answer 29

The large lumens and relatively thin walls of veins make them far more distensible than arteries.

Question 30

The volume of blood that is approximately 21 percent of the venous blood is located in venous networks within the liver, bone marrow, and integument is called what?

Answer 30

The venous reserve

Question 31

Refers to the movement of blood through a vessel, tissue, or organ, and is usually expressed in terms of volume of blood per unit of time.

Answer 31

Blood flow

Question 32

This phenomenon discusses the factors that impede or slow blood flow?

Answer 32

Resistance

Question 33

The force exerted by blood upon the walls of the blood vessels or the chambers of the heart.

Answer 33

Blood pressure