Blood Vessels, Arteries, and Veins

Question 1

The three principal categories of blood vessels differ in?

Answer 1

General location
Direction of blood flow
Histological structure of their walls

Question 2

What are the 3 categories of blood vessels?

Answer 2

Arteries
Capillaries
Veins

Question 3

What are arteries?

Answer 3

Efferent (caries away) vessels of the cardiovascular system

Question 4

What are capillaries?

Answer 4

Microscopic, thin walled vessels that connect the arterioles and venules

Question 5

What are veins?

Answer 5

Afferent (carrying toward) vessels of the cardiovascular system

Question 6

What is the function of capillaries?

Answer 6

The exchange of nutrients/gases between the blood and tissue cells

Question 7

The walls of arteries and veins are composed of what 3 layers?

Answer 7

Tunica Interna
Tunica Media
Tunica Externa

Question 8

Describe the tunica interna?

Answer 8

(Also known as the tunica intima)
Presents in small blood vessels (small blood vessels must have this layer at least)
Consists of simple squamous epithelium called endothelium
Endthelium become continuous with endocardium (reduces friction to blood flow)

Question 9

Describe the tunica media?

Answer 9

The middle layer, is usually the thickest
Consist of smooth muscle and elastic tissue
Functions: strengthen the vessels and prevent the blood pressure from rupturing them, and to provide for vasomotion, changes in the diameter of the blood vessel

Question 10

Describe the tunica externa?

Answer 10

The outer most layer
consists of collagen fibers for strength
Small vessels called vasa vasorum supply blood to at least the outer half of the wall of a larger vessel. (Vasa vasorum is like coronary artery in the heart)

Question 11

Describe arteries?

Answer 11

Resistance vessels, strong resilient tissue that resists high blood pressure, more muscular than veins.

Question 12

How many types of arteries are there?

Answer 12

3:

Large, Medium, and Small

Question 13

Describe Large arteries?

Answer 13

Also known as Elastic or Conducting arteries (less function)
Examples: Aorts, common carotid, subclavian, pulmonary trunk, and common iliac
Expand during ventricular systole to receive blood, and recoil during diastole
More elastic fibers or connective tissue, less smooth muscle

Question 14

Describe Medium arteries?

Answer 14

Also known as Muscular and Distributing arteries
Examples: Brachial, femoral, renal, and splenic
Substantially more smooth muscle in tunica media
Smooth muscle controls diameter of blood vessel (vasodilation and vasoconstriction) and regional blood flow (Exponential impact)
Redirection of blood flow in response to changing metabolic needs controlled by medium arteries
Sympathetic activities control the diameter

Question 15

Describe Small arteries?

Answer 15

Also known as Resistance arteries or Arterioles
Examples: Blood flow in thumb (control localized blood flow)
More smooth muscle in tunica media, relatively little elastic tissue
Major resistance vessels, big impact on systemic blood flow
Aorta = No resistance > low pressure
drop
Arterioles = High resistance > huge
pressure drop
Functions: control blood flow to tissues, control systemic blood pressure (pinpoint)
Hemorrhage > blood pressure drop (drop in CO) > arteriole constrict to raise blood pressure

Question 16

Where are baroreceptors located?

Answer 16

In the blood vessel: Ascending aorta, aortic arch, and carotid artery

Question 17

What is the function of baroreceptors?

Answer 17

Stretch receptors that monitor blood pressure

Question 18

How do baroreceptors work?

Answer 18

Blood pressure rises > receptors stretch > wall of artery stretches > arterial impulse to brain > blood pressure lowers

Question 19

What are the locations and percentages for blood distribution?

Answer 19

Arteries: 11%
Capillaries: 5%
Heart: 12%
Lung: 18%
Veins: 54%

Question 20

Describe veins in terms of volume?

Answer 20

Thin walled and flaccid, and expand easily to accommodate an increased volume of blood
Have a greater capacity for blood containment than arteries do
At rest, about 54% of blood is found in the systemic veins (11% in systemic arteries)

Question 21

Describe blood flow in the veins?

Answer 21

Being distant from the ventricles of the heart > low blood pressure (about 10 mmHg)
Blood flow in the veins is steady, rather than pulsating with the heartbeat like flow in the arteries
Collapse when empty and thus have relatively flattened, irregular shapes in histological sections

Question 22

Describe venous valves that are found in veins?

Answer 22

Most veins have one way flaps called venous valves that prevent blood from flowing back and pooling in the lower extremities due to the effects of gravity
Ex: Skeletal muscle pump is a collection of skeletal muscles that aid the heart in the circulation of blood. It is especially important in increasing venous return to the heart

Question 23

How and why are varicose veins formed?

Answer 23

In people who stand for long periods, such as barbers and cashiers, blood tends to pool in lower limbs and stretch the veins.
This especially true of superficial veins, which are not surrounded by supportive tissue.
Stretching pulls the cusps of venous valves farther apart until the valves become incompetent to prevent the backflow of blood. As veins become further distended, their walls grow weak and they develop into varicose veins with irregular dilatations and twisted pathways.

Question 24

What else also promotes varicose veins?

Answer 24

Obesity and pregnancy by putting pressure on large veins of the pelvic region and obstructing drainage from the legs.
They sometimes develop because of hereditary weakness of the valves. With less drainage of blood, tissues of the leg and foot may become edematous and painful.
Hemorrhoids are varicose veins of the anal canal

Question 25

The flow of blood back to the heart is achieved by what 5 mechanisms?

Answer 25

1. Pressure Gradient 2. Gravity 3. Skeletal-muscle Pump 4. Thoracic Pump 5. Cardiac Suction

Question 26

Describe pressure gradient in terms of venous return?

Answer 26

Pressure generated by the heart is the most important force of venous flow When blood volume rises, venous pressure gradient and venous return rise also When veins diameter increases (dilates), venous pressure gradient and venous return increase If all the body's blood vessels constrict, venous return increases

Question 27

Describe gravity in terms of venous return?

Answer 27

Blood from the head and neck returns to the heart by simply flowing down hill Thus the venous pressure of large veins of the neck are close to zero

Question 28

Describe skeletal-muscle pumps as it relates to venous return?

Answer 28

In the limb, veins are surrounded and massaged by the muscles They squeeze the blood out of the compressed part of the vein The valves ensure that blood can go in only one direction - toward the heart.

Question 29

Describe the thoracic pump in relation to venous return?

Answer 29

Inhale > thoracic cavity expands > internal pressure drops > diaphragm moving downward > pressure in abdominal cavity raises If abdominal pressure on the inferior vena cava rises while thoracic pressure on it drops, then blood is squeezed upward toward the heart.

Question 30

Describe cardiac suction in relation to venous return?

Answer 30

During ventricular systole, the tendinous cords pull the AV valve cusps downward, slightly expanding the atrial space This creates a slight suction that draws blood into the atria from the vena cava and pulmonary veins

Question 31

How does exercise increase venous return?

Answer 31

1. The HR is faster, increasing CO and BP 2. Blood vessels of the skeletal muscles, lungs, and coronary circulation dilate, increasing flow. 3. The increase in respiratory rate and depth enhances the action of the thoracic pump. 4. Muscle contractions increase venous return by means of skeletal muscle pump. 5. Increased venous return increase CO, which is important in perfusion (passing of fluid) of muscles just when they need it most.

Question 32

What are the 3 characteristics of capillaries?

Answer 32

1. Incredibly thin wall (Tunica intima only) 2. High surface area or cross section area 3. Very slow velocity

Question 33

What do capillaries do?

Answer 33

Maximize diffusion

Question 34

Capillary beds contain?

Answer 34

Usually 10-100 capillaries supplied by a single metarteriole

Question 35

What are metarterioles?

Answer 35

Short vessels that link arterioles and capillaries (bypass between arteriole & venule) Continues as a thoroughfare channel leading directly to a venule (small vein).

Question 36

Describe a precapillary sphincter?

Answer 36

Open (dilated): capillaries well perfused with blood and engage in exchanges with tissue fluid Closed: most blood bypassing the capillaries to venule, and engages in little fluid exchange.

Question 37

Describe the amount of blood in the body versus the number of capillaries in the body?

Answer 37

Their is not enough blood in the body to fill all capillaries, about 3 quarters of the body's capillaries are shut down at any given moment. In skeletal muscle for example, about 90% of capillaries have little or no blood flow during rest. During exercise they receive an abundant blood flow, while capillary beds elsewhere shut down (skin & intestines) to compensate.

Question 38

Describe the metabolism of a capillary?

Answer 38

Low O2, high CO2 and waste material = relax the precapillary sphincter The open/closing frequency is higher in metabolically active cells.

Question 39

What is Edema?

Answer 39

The accumulation of excess fluid in a tissue Often shows as swelling of the face, fingers, abdomen, or ankles; but also occurs in internal organs. Occurs when fluid filters into a tissue faster than it is reabsorbed.

Question 40

What are the 3 fundamental causes of Edema?

Answer 40

1. Rise in capillary filtration 2. Decrease in capillary reabsorption 3. Obstructed lymphatic drainage

Question 41

Filtration occurs at which end of a capillary?

Answer 41

Arterial

Question 42

Reabsorption occurs at what end of capillary?

Answer 42

Venous

Question 43

Capillaries reabsorb what % of passing fluid?

Answer 43

85% of the fluid they filter, the other 15% is absorbed and returned to the blood by way of lymphatic system.