Cardiovascular System 42.3

Question 1

What do all blood vessels contain?

Answer 1

A central lumen (cavity) lined with an endothelium

they’re tubular

endothelium: a single layer of flattened epithelial cells, continuous with endocardium

Question 2

What does the smooth endothelial layer do?

Answer 2

minimizes resistance to fluid flow and can also produce chemicals

Question 3

What do capillaries walls consist of?

Answer 3

an endothelium and a surrounding extracellular layer called the basal lamina. there is no smooth muscle.

Question 4

Where does the exchange of substances between the blood and interstitial fluid occur?

Answer 4

Only in capillaries because only there are the vessels walls thin enough to permit this exchange, single file erythrocytes pass through here

Question 5

Difference between arteries and veins?

Answer 5

Arteries and veins have walls that consist of two layers of tissue surrounding the endothelium. The outer layer is formed by connective tissue that contains elastic fibers which allow the vessel to stretch and recoil, and collagen which provides strength. The next layer to the endothelium contains smooth muscle and more elastic fibers.

Question 6

Arterial walls are…

Answer 6

thick, strong and elastic. they can thus accommodate blood pumped at high pressure by the heart, bulging outward as blood enters and recoiling as the heart relaxes between contraction

Question 7

What do the smooth muscles in the walls of arteries and arterioles help regulate?

Answer 7

the path of blood flow. Signals from the nervous system and circulating hormones act on the smooth muscle of these vessels, causing dilation or constriction that modulates blood flow to different parts of the body.

Question 8

Why do veins not require thick walls?

Answer 8

because they convey blood back to the heart at a lower pressure

Question 9

What do veins have that arteries dont?

Answer 9

valves due to the need to prevent backflow due to a strong opposition because of gravity especially in veins

Question 10

Where is there a dramatic decrease in velocity?

Answer 10

from the arteries to the capillaries because of the increase in cross-sectional area and can hold more blood

Question 11

From the capillaries to veins and venules what happens to velocity?

Answer 11

There is a slight increase because cross sectional area decreases

Question 12

When is arterial blood pressure the highest?

Answer 12

when the heart contracts during ventricular systole , the pressure at this time is called systolic pressure

Question 13

What happens when the heart contracts?

Answer 13

Blood enters the arteries faster than it can leave, and the vessels stretch to a wider diameter from the rise in pressure

Question 14

why does blood flow continously into arterioles and capillaries?

Answer 14

because the arteries remain pressurized throughout the cardiac cycle

Question 15

How does homeostatic mechanisms regulate blood pressure?

Answer 15

by altering the diameter of arterioles.

Vasoconstriction: if smooth muscles in arteriole walls contract, the arterioles narrow. This increases blood pressure upstream in the arteries.

Vasodilation: when the smooth muscles relax, the arterioles increase in diameter that causes the bp in the arteries to fall.

Question 16

What is a major inducer of vasodilation and vasoconstriction

Answer 16

Nitric oxide, a gas and endothelin, a peptide (respectively). Cues from the nervous and endocrine systems regulate production of NO and endothelin in blood vessels where their opposing activites provide homeostatic regulation of bp

Question 17

How is fainting triggered?

Answer 17

When the nervous system detects the bp in your brain is below the level needed to provide adequate blood flow. By causing your body to collapse to the ground, fainting effectively places your head at the level of your heart, quickly increasing blood flow to your brain.

an animal that has long neck has adaptation for upper extremity, they have high systolic pressure.

Question 18

Given that capillaries lack smooth muscle, how is blood flow in capillary beds altered?

Answer 18

1) constriction or dilation of the arterioles that supply capillary beds
2) precapillary sphincters, rings of smooth muscle located at the entrance to capillary beds. The opening and closing of these muscular rings regulates and redirects the passage of blood into particular sets of capillaries. Act as valves, they can be controlled by chemical conditions around that area. During relaxation (open), there’s movement all throughout and goes through thoroughfare channel, the thoroughfare channel directly connects arterial and venule, traveling through “true” capillary. During constriction, we only have blood flow straight from arterial, through thoroughfare into venule without passing through “true” capillaries.
i. e during “flight or fight” diverting blood flow from digestive system

Question 19

What signals regulate mechanisms in capillary beds?

Answer 19

nerve impulses, hormones traveling throughout the bloodstream, and chemicals produced locally

Question 20

How does exchange occur?

Answer 20

A few macromolecules are carried across the endothelium in vesicles that form on one side by endocytosis and release their contents on the opposite side by exocytosis. Small molecules, such as oxygen and co2 simply diffuse across the endothelial cells or in some tissues through microscopic pores in the capillary wall. These openings also provide the route for transport of small solutes.

Question 21

What two opposing forces control the movement of fluid between the capillaries and the surrounding tissue?

Answer 21

Blood pressure tends to drive fluid out of the capillaries and the presence of blood proteins tends to pull fluid back.

Question 22

Osmotic pressure

Answer 22

the pressure produced by the difference in solute concentration across a membrane

Question 23

Why do many blood proteins remain in the capillaries?

Answer 23

they are too large to pass readily through the endothelium. These dissolved proteins are responsible for much of the blood’s osmotic pressure.

Question 24

Approximately how many liters of fluid does a adult human body lose to the surrounding tissue?

Answer 24

4-8 L

Question 25

Via what system are lost proteins and fluids recovered and returned to the blood?

Answer 25

Lymphatic system

Question 26

How does the lymphatic system work?

Answer 26

Fluid diffuses into the lymphatic system via a network of tiny vessels intermingled with capillaries. The recovered fluid, called lymph, circulates within the lymphatic system in one way valves before draining into a pair of large veins of the cardiovascular system at the base of the neck, subclavian veins (under clavicle). This joining of the lymphatic and cardiovascular systems completes the recovery of fluid lost from capillaries as as the transfer of lipids from the small intestine to the blood.

Question 27

What mechanisms assist movement of lymph?

Answer 27

1) Lymph vesses, like veins, have valves that prevent backflow of fluid. Rhythmic contractions of the vessel walls help draw fluid into the small lymphatic vessels.
2) in addition, skeletal muscle contractions play a role in moving lymph, because lacks muscular pump.

Question 28

What can disruptions in the movement of lymph result in?

Answer 28

fluid accumulation (edema) in affected tissues

Question 29

What is elephantiasis?

Answer 29

a condition marked by extreme swelling in limbs or other body parts due to parasitic worms lodged in lymph vessels and blocking lymph movement

Question 30

What organs are found along a lymph vessel?

Answer 30

small, lymph filtering, lymph nodes. Inside each lymph node is a honeycomb of connective tissue with spaces filled by white blood cells, which function in defense. When the body is fighting an infection, the white blood cells multiply rapidly, and the lymph nodes become swollen and tender.

Question 31

Where is overstretching more likely to occur?

Answer 31

artery because of the amount of stretching required because of the pressure

Question 32

velocity and area are?

Answer 32

inversely proportional, when we have high velocity we have a low cross sectional area

Question 33

why does velocity in veins not pick up as much as in the aorta?

Answer 33

due to the distance of vessels like veins and superior/inferior vena cava from initial kinetic energy after leaves left ventricle

Question 34

what is the drop in aortic pressure?

Answer 34

diastolic pressure

Question 35

Smooth muscle pathway

Answer 35

1) acetylcholine is our ligand and binds to a receptor found on the endothelial cells of blood vessels. As a result, it activates the result and production of IP3.
2) IP3 is a second messenger, so is a ligand that can bind to a ligand gated channel for IP3.
3) the binding of IP3 to that channel allows for calcium ions to leave the lumen of the endoplasmic reticulum down their concentration gradient out into the surround fluid (cytosol). There are calcium ATPases that help ensure that calcium ion concentration are low within cytosol so more sensitive to change in concentration.
4) presence of calcium ions in cytosol results in activation of nitric oxide synthase, which leads to production of nitric oxide gas. It is utilizing argenine available in cytosol to facilitate that process.
5) nitric oxide is capable of diffusing out of endothelial cells and nearby smooth muscle cells, helping stimulate cyclic GMP synthesis (GTP to GMP). The presence of cyclic GMP triggers smooth muscle to relax, increasing blood flow. Nitroglycerin is a drug that can be used to treat chest pest caused by insufficient blood flow to the heart (angina), triggering release of nitric oxide and increase blood flow. Syldenifol, inhibits phosphodiesterase activity (enzyme converting cGMP to GTP), increasing cGMP and promoting continued muscle relaxation, trademarked viagra.

Question 36

mechanisms help assist veinous return?

Answer 36

1) muscular pump, based on the movement of skeletal muscle. Skeletal muscle is surrounding the veins and as they contract & relax they’ll squeeze blood back to the heart. The valves will prevent any backwards flow.

people who stand still will have issues with blood pooling because they won’t have enough skeletal muscle contraction to ensure blood returning to heart effectively

Question 37

measuring bp

Answer 37

done in the brakial artery.
sphingmalmonometer- cuff goes around arm above elbow and inflate cuff with air appying enough pressure to exceed 120 mm Hg. Once we exceed this pressure, blood flow is going to stop and the brakial pulse isnt felt or heard. Reduce the cuff pressure gradually, we’re going to listen for sounds within brakial artery once drops below 120 mm Hg (first sound). The first sounds are heart when there’s a small amount of blood coming from restricted artery (systolic pressure). As the blood reduces even more and the blood flows freely the sounds wont be heard so when sounds top they’re the diastolic pressure (70 mm Hg).

Question 38

flow of blood from arterial to venule

Answer 38

microcirculation

Question 39

Where does most of the fluid exit out through?

Answer 39

arterial end, rather than veinous end which has to due with pressure seen at the arterial end.

Question 40

How is fluid returned?

Answer 40

through osmosis, so osmotic pressure is applied to capillaries. within the vessels there exists plasma proteins, the size of the proteins makes it impermissible can’t escape through the pores. Meaning theres an increase of proteins in blood plasma than seen in the interstitial fluid so water wants to enter the capillaries.

Question 41

Comparing arrows length?

Answer 41

regardless at which end of capillary end we’re at the plasma protein concentration is consist so the osmotic pressure is consistent.

Question 42

abnormal pressure

Answer 42

too much capillary blood pressure can cause too much fluid to enter interstitial fluid causing oedema (swelling of tissues) commonly seen in pregnancy.