Week 26 / Circulatory System 4

Question 1

Question: What causes the 1st heart sound (lub)?

Answer 1

Answer: The 1st heart sound (lub) is caused by the closure of the AV valves at the start of ventricular contraction [ systole].

Question 2

Question: What causes the 2nd heart sound (dub)?

Answer 2

Answer: The 2nd heart sound (dub) is due to the closure of the aortic and pulmonary valves at the end of ventricular systole.

Question 3

Question: When is the 3rd heart sound heard, and what causes it?

Answer 3

Answer: The 3rd heart sound is heard in early diastole, caused by the inrush of blood during rapid ventricular filling.

Question 4

Question: When is the 4th heart sound heard, and what causes it?

Answer 4

Answer: The 4th heart sound is heard immediately before the 1st heart sound, during late diastole, and is caused by ventricular filling.

Question 5

Question: What is the vascular system also called?

Answer 5

Answer: The vascular system is also called the “Vascular Tree.”

Question 6

Question: What is the function of the vascular system?

Answer 6

Answer: The vascular system is a closed system of vessels that directs the flow of blood from the heart to organs and tissues and back to the heart.

Question 7

Question: What are the main types of blood vessels in the vascular system?
[Arteries,Arterioles,Capillaries,Venules,Veins]

Answer 7

Answer:
Arteries: Carry blood away from the heart to tissues.

Arterioles: Smaller branches of arteries within organs.

Capillaries: Smaller branches of arterioles that facilitate exchanges between blood and surrounding cells.

Venules: Formed when capillaries re-join and return blood to the heart.

Veins: Formed when venules re-join and return blood to the heart.

Question 8

Question: What is the function of the pulmonary circulation?

where does gas exchange occur?

Answer 8

Answer: Pulmonary circulation involves the flow of blood from the heart to the lungs and back,

where gas exchange occurs in the pulmonary capillaries.

Question 9

Question: What is the path of blood in pulmonary circulation?

Answer 9

Answer:

Blood flows from the heart into the pulmonary arteries to pulmonary arterioles.

It then moves into the pulmonary capillaries in the lungs for gas exchange.

The blood is returned to the heart via the pulmonary veins.

Question 10

Question: What is the function of the systemic circulation?

Answer 10

Answer: Systemic circulation carries oxygenated blood from the heart to the tissues and organs and returns deoxygenated blood back to the heart.

Question 11

Question: What is the path of blood in systemic circulation?

Answer 11

Answer:

Blood is pumped from the heart into the aorta (major systemic artery).
It travels through smaller arteries to supply various tissues.
Blood flows into the systemic capillaries for nutrient and gas exchange.
Blood is returned to the heart through venules and veins.

Question 12

Question: What are the three tunics (layers) of blood vessel walls?
[what are they made from?]

Answer 12

Answer:

Tunica externa (adventitia): The outer layer, made of connective tissue and elastin fibers.

Tunica media: The middle layer, composed of smooth muscle.

Tunica interna (intima): The innermost lining, made of squamous endothelium, a basement membrane, and a layer of elastin.

Question 13

Question: What is the function of the tunica externa?

Answer 13

Answer: The tunica externa provides structural support and protection to the blood vessel.

Question 14

Question: What role does the tunica media play in blood vessels?

Answer 14

Answer: The tunica media controls the diameter of the blood vessel through smooth muscle contraction and relaxation, regulating blood flow and blood pressure.

Question 15

Question: What is the purpose of the tunica interna?

Answer 15

Answer: The tunica interna provides a smooth lining that reduces friction between the blood and vessel walls, aiding in the efficient flow of blood.

Question 16

Question: What are the main functions of arteries? [2]

Answer 16

Answer:

Rapid-transit conduits: Arteries transport blood quickly from the heart to organs.

Pressure reservoirs: Arteries provide the driving force for blood flow during diastole, acting as a reservoir for pressure.

Question 17

Question: What are the two main types of arteries?

Answer 17

Answer:

Elastic arteries (e.g., aorta, pulmonary artery): Have numerous layers of elastin fibers, allowing them to expand during systole and recoil during diastole.

Muscular arteries (e.g., femoral, coronary arteries): Have less elasticity but thicker smooth muscle layers, resulting in smaller changes in diameter as blood pressure rises and falls.

Question 18

Question: What is the function of elastic arteries during the cardiac cycle?

Answer 18

Answer: Elastic arteries expand when the pressure from ventricular systole increases and recoil when the ventricles relax, helping maintain continuous blood flow.

Question 19

Question: How do muscular arteries differ from elastic arteries? [2]

Answer 19

Answer: Muscular arteries have less elastin and thicker smooth muscle, which causes less fluctuation in diameter compared to elastic arteries.

Question 20

Question: What are arterioles and where are they located?

Answer 20

Answer: Arterioles are smaller branches of arteries within organs, responsible for regulating blood flow to specific tissues.

Question 21

Question: Why do arterioles adjust the blood to individual organs?

[Why do arterioles adjust their radius in individual organs?] , what does it help regulate?

Answer 21

Answer: The vessel radius of arterioles can be adjusted independently to distribute cardiac output according to the body’s momentary needs and help regulate arterial blood pressure.

Question 21

Question: What is the primary role of arterioles in the circulatory system? [2]

Answer 21

Answer: Arterioles are major resistance vessels that facilitate a large pressure drop,

helping to regulate blood flow to organs and distribute cardiac output efficiently.

Question 22

Question: How is the tone (constriction or dilation) of arterioles controlled?

Answer 22

Answer: The tone of arterioles is controlled via nervous and chemical mechanisms, which regulate their constriction or dilation.

Question 23

Question: What causes normal arteriolar tone? [8]

Answer 23

Answer: Normal arteriolar tone is caused by:

Myogenic activity
Oxygen (O2)
Carbon dioxide (CO2) and other metabolites
Endothelin
Sympathetic stimulation
Vasopressin
Angiotensin II
Cold

Question 24

Question: What happens during vasoconstriction in arterioles? [

Answer 24

Answer: Vasoconstriction involves increased contraction of the circular smooth muscle in the arteriolar wall, leading to increased resistance and decreased flow through the vessel. It is caused by: Myogenic activity Increased CO2 and other metabolites Sympathetic stimulation Histamine release Cold

Question 25

Question: What happens during vasodilation in arterioles?

Answer 25

Answer: Vasodilation involves decreased contraction of the circular smooth muscle in the arteriolar wall, which leads to decreased resistance and increased blood flow through the vessel. It is caused by: Nitric oxide Heat Decreased sympathetic stimulation

Question 26

Question: What are capillaries and where are they located and what is there function?

Answer 26

Answer: Capillaries are smaller and densely packed branches off arterioles and metarterioles within organs, serving as the sites for the exchange of nutrients and wastes between blood and surrounding tissue cells.

Question 27

Question: How does exchange of materials occur in capillaries?

Answer 27

Answer: The exchange of materials in capillaries largely occurs via diffusion due to their thin walls, which consist of a single layer of flat endothelial cells and a thin basement membrane.

Question 28

Question: What features allow capillaries to facilitate exchange?

Answer 28

Answer: Capillary walls are perforated by water-filled pores, which allow the passage of small, water-soluble substances.

Question 29

Question: What regulates blood flow through capillaries?

Answer 29

Answer: Precapillary sphincters regulate blood flow through capillaries by contracting and relaxing, depending on the body's needs.

Question 30

Question: What are the three main types of capillaries? [CFS]

Answer 30

Answer: Capillaries are classified based on the size of their water-filled pores: Continuous capillaries: Have small pores, allowing limited substance exchange. Fenestrated capillaries: Contain larger pores, allowing more rapid exchange of larger molecules. Sinusoidal capillaries: Have very large pores, allowing the passage of even larger molecules and cells.

Question 31

Question: What are the characteristics of continuous capillaries? [types of pores , where are they found]

Answer 31

Answer: Endothelial cells are continuous or closely joined. Narrow intercellular pores (~4 µm) permit the passage of small molecules. Found in skeletal and cardiac muscle, lungs, and adipose tissue.

Question 32

Question: What are the characteristics of fenestrated capillaries? [types of pores , where are they found]

Answer 32

Answer: Have larger holes (20-100 µm) in addition to narrow pores. Provide greater permeability and facilitate rapid exchange. Found in kidneys, intestines, and endocrine glands.

Question 33

Question: What are the characteristics of discontinuous (sinusoidal) capillaries? [types of pores , where are they found]

Answer 33

Answer: Endothelial cells are discontinuous, leading to very large intercellular pores. They are leaky, allowing the passage of larger molecules and cells. Found in liver, spleen, and bone marrow.

Question 34

Question: What are the two main mechanisms of capillary exchange between blood and surrounding tissues?

Answer 34

Answer: Passive diffusion: Movement of solutes down their concentration gradient. Bulk flow: Ultrafiltration and reabsorption of protein-free plasma.

Question 35

Question: What are the determinants of bulk flow in capillary exchange?[4]

Answer 35

Answer: The bulk flow is determined by the following pressures: Capillary blood pressure (P): Outward pressure, that pushes fluid out of the capillaries. Plasma-colloid osmotic pressure (π): Inward pressure, that pulls fluid into the capillaries. Interstitial fluid hydrostatic pressure (P): Inward pressure exerted by fluid in the interstitial space. Interstitial fluid colloid osmotic pressure (πf): Outward pressure , that pulls fluid from the capillaries into the interstitial space.

Question 36

Question: How does passive diffusion differ from bulk flow in capillary exchange?

Answer 36

Answer: Passive diffusion involves the movement of solutes based on concentration gradients. Bulk flow refers to the movement of fluid and solutes, influenced by pressure differences, such as capillary blood pressure and osmotic pressures.

Question 37

Question: What is the role of the venous system in the circulatory system?

Answer 37

Answer: The venous system is a low resistance system that returns blood from tissues to the heart.

Question 38

Question: What are the characteristics of systemic veins?

Answer 38

Answer: Large radius: Results in low resistance to flow. Thin walls: Contain little smooth muscle or elastin, making them highly distensible with minimal elastic recoil. Blood reservoir: Serve as capacitance vessels for storing blood.

Question 38

Question: What does the venous system consist of?

Answer 38

Answer: Venules Small veins Large, systemic veins

Question 39

Question: How do veins ensure blood flows toward the heart?

Answer 39

Answer: One-way valves prevent backflow of blood. The skeletal muscle pump assists blood flow by contracting muscles around veins, pushing blood toward the heart.