Circulatory System

Question 1

How does the vasculature of the CVS change as it goes from the heart to the body?

Answer 1

from the heart, large arteries branch into progressively smaller arteries that deliver blood to various parts of the body

Question 2

What do arteries branch into when reaching an organ?

Answer 2

when a small artery reaches an organ, it branches into smaller arterioles , which branch into capillaries

Question 3

What do capillary networks do and what do they rejoin to form?

Answer 3

capillary networks exchange
substances between the blood and cells, then rejoin to form small venules

Question 4

What do small rejoin to form?

Answer 4

small veins progressively join to form larger veins that eventually become the veins that enter the heart

Question 5

What is the general structure of arteries? Why do they need this structure?

Answer 5

arteries have relatively large diameters to deal with higher blood pressures

Question 6

What are the three major layers of arteries?
(Describe what type of cells are in each layer)

Answer 6

artery walls consist of three major tissue layers
-an outer layer of connective tissue containing collagen and elastin fibers, which gives the vessel recoil ability
-a relatively thick middle layer of vascular smooth muscle cells, also mixed with elastin fibers
-a thin inner layer of flattened cells ( endothelium )

Question 7

What is the structure of capillaries? Why does it have this structure?

Answer 7

capillary walls consist of a single layer of endothelial cells through which gases, nutrients, and wastes are exchanged with the interstitial fluid

Question 8

How is blood flow through capillaries regulated?

Answer 8

blood flow through the capillary networks is controlled by contraction of smooth muscle in the arterioles

a small ring of smooth muscle (precapillary sphincter) at the junction between an arteriole and a capillary adjusts the rate of flow through the capillary network

Question 9

a small ring of smooth muscle (____ ____) at the junction between an arteriole and a capillary adjusts the rate of flow through the capillary networks

Answer 9

precapillary sphincter

Question 10

How is the flow of blood through and organ regulated?

Answer 10

the volume of blood flowing through an organ is adjusted by regulating the internal diameter of the arterioles of the organ

Question 11

How small is a capillary?

Answer 11

the diameter of capillaries is so small that red blood cells must squeeze through in single file

Question 12

What can pass through during vasoendothelial exchange?

Answer 12

narrow spaces between capillary endothelial cells allow water, ions, and small molecules such as glucose to pass freely between the blood and interstitial fluid

Question 13

resistance to blood flow in capillaries is ____?

Answer 13

High

Question 14

resistance to blood flow in capillaries is high. What does this cause and why is this necessary?

Answer 14

resistance to blood flow in capillaries is high, so blood slows down – rate of flow increases when blood returns to veins
slow movement of blood through capillaries maximizes the time for exchange of substances between blood and tissues

Question 15

What can pass through during vasoendothelial exchange and by what means does this occur?

Answer 15

narrow spaces between capillary endothelial cells allow water, ions, and small molecules such as glucose to pass freely between the blood and interstitial fluid

leukocytes are able to squeeze actively between the cells and pass from the blood to the interstitial fluid

Question 16

What drives exchange between capillaries and interstitial fluid?

Answer 16

two major mechanisms drive exchange of molecules and ions between capillaries and interstitial fluid: (1) diffusion along concentration gradients, and (2) bulk flow

Question 17

What is unable to pass through in vasoendothelial exchange?

Answer 17

erythrocytes, platelets, and plasma proteins are too large to pass between cells, and are retained inside the capillaries – except for molecules transported by specific carriers

Question 18

How does glucose, O2, and CO2 pass through endothelial cells plasma membrane?

Answer 18

O2 and CO2 diffuse directly through the lipid bilayer of endothelial cell plasma membranes – glucose passes by facilitated diffusion through transport proteins

Question 19

What does bulk flow do?

Answer 19

bulk flow carries water, ions, and molecules out of the capillaries through spaces between capillary endothelial cells

Question 20

Where is total diffusion in capillaries the greatest and why?

Answer 20

total diffusion is greatest near the arterioles, where the concentration differences between blood plasma and interstitial fluid are highest

Question 21

What is bulk flow driven by?

Answer 21

bulk flow is driven by blood pressure, which is higher than the pressure of the interstitial fluid

Question 22

Where is bulk flow the greatest?

Answer 22

like diffusion, bulk flow is greatest near the arterioles, where the pressure difference is highest

Question 23

What is the structure of veins?
What can they act as?

Answer 23

the walls of venules and veins are thinner than those of arteries and contain little elastin

many veins have interior flaps of connective tissue that form one-way valves that keep blood flowing toward the heart

the thin walls expand and contract over a relatively wide range, allowing venules and veins to act as blood reservoirs

Question 24

What is deep vein thrombosis?

Answer 24

lack of skeletal muscle activity can lead to blood clots ( deep vein thrombosis ) and cause serious medical problems

[Blood clot in deep veins of legs]

Question 25

Where atherosclerotic plaques form?
What can they cause?

Answer 25

atherosclerotic plaques may form at damaged sites, reducing blood vessel diameter and impeding blood flow

damaged endothelial lining may trigger formation of blood clots, which may break loose and block other blood vessels

Question 26

What can cause heart attacks and strokes?

Answer 26

atherosclerosis in the coronary arteries can reduce or block the flow of blood to heart muscle cells, causing a heart attack

blockage of arteries in the brain is a common cause of stroke (cerebrovascular disease), causing a loss of critical brain functions

Question 27

How atherosclerosis prevented?

Answer 27

risk of heart attacks and stroke can be reduced by avoiding conditions that damage blood vessel endothelium (regular exercise, for eg.)

Question 28

Why is lymphatic system important (3)?

Answer 28

under normal conditions, more fluid (from plasma) moves out of capillaries than into them
the lymphatic system collects excess interstitial fluid (lymph) and returns it to the venous blood

this system also collects fats that have been absorbed from the small intestine and delivers them to the blood circulation

the lymphatic system is a key component of the immune system

Question 29

Where do lymphatic vessels dump lymph?

Answer 29

lymphatic vessels collect lymph and transport it to lymph ducts that empty into veins of the circulatory system

Question 30

What are lymph capillaries?

Answer 30

lymph capillaries are thin walled vessels that are distributed throughout the body, associated with capillaries of the circulatory system (but slightly larger than blood capillaries)

Question 31

What is the relation between lymph and interstitial fluid?
How does this related to the structure of lymph capillaries?

Answer 31

interstitial fluid enters lymph capillaries (becoming lymph) where the endothelial cells overlap, forming a flap

Question 32

What does large opening in lymph capillaries allow?

Answer 32

the large openings admit all components of interstitial fluid, including bacteria, damaged cells, debris, and lymphocytes

Question 33

What is the path of lymphatic flow?

Answer 33

lymph capillaries merge into lymph vessels with one-way valves that prevent lymph from flowing backward
lymph vessels lead to the thoracic duct and the right lymphatic duct, which empty the lymph into a vein beneath the clavicles (collarbones)

Question 34

What prevents backflow of lymph?

Answer 34

One-way valves

Question 35

What helps move lymph?

Answer 35

movements of skeletal muscles and breathing movements help move the lymph through the vessels

Question 36

What are 5 lymphatic tissues/organs?

Answer 36

tissues and organs of the lymphatic system include the lymph nodes, spleen, thymus, and tonsils

patches of lymphoid tissue are also scattered in other regions of the body, such as the small intestine and appendix

Question 37

What do does lymph tissue/organs do?

Answer 37

filters viruses, bacteria, damaged cells, and cellular debris from the lymph and bloodstream, and help defend the body against infection and cancer

Question 38

Where lymph nodes located?

Answer 38

lymph nodes are clustered along the sides of the neck, in the armpits and groin, and in the abdomen and chest cavity

Question 39

What do lymph nodes contain?

Answer 39

the nodes contain macrophages that engulf and destroy cellular debris, infecting bacteria and viruses in the lymph

other leukocytes in lymph nodes produce antibodies that aid in the destruction of invading pathogens

Question 40

What happens to cancer cells in lymph nodes?

Answer 40

cancer cells in the nodes may be destroyed or may remain to grow and divide, forming new tumors within the nodes

Question 41

Study the study guide material for circular system!