Week 26 / Circulatory System 4 Flashcards
Question: What causes the 1st heart sound (lub)?
Answer: The 1st heart sound (lub) is caused by the closure of the AV valves at the start of ventricular contraction [ systole].
Question: What causes the 2nd heart sound (dub)?
Answer: The 2nd heart sound (dub) is due to the closure of the aortic and pulmonary valves at the end of ventricular systole.
Question: When is the 3rd heart sound heard, and what causes it?
Answer: The 3rd heart sound is heard in early diastole, caused by the inrush of blood during rapid ventricular filling.
Question: When is the 4th heart sound heard, and what causes it?
Answer: The 4th heart sound is heard immediately before the 1st heart sound, during late diastole, and is caused by ventricular filling.
Question: What is the vascular system also called?
Answer: The vascular system is also called the “Vascular Tree.”
Question: What is the function of the vascular system?
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: What are the main types of blood vessels in the vascular system?
[Arteries,Arterioles,Capillaries,Venules,Veins]
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: What is the function of the pulmonary circulation?
where does gas exchange occur?
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: What is the path of blood in pulmonary circulation?
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: What is the function of the systemic circulation?
Answer: Systemic circulation carries oxygenated blood from the heart to the tissues and organs and returns deoxygenated blood back to the heart.
Question: What is the path of blood in systemic circulation?
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: What are the three tunics (layers) of blood vessel walls?
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: What is the function of the tunica externa?
Answer: The tunica externa provides structural support and protection to the blood vessel.
Question: What role does the tunica media play in blood vessels?
Answer: The tunica media controls the diameter of the blood vessel through smooth muscle contraction and relaxation, regulating blood flow and blood pressure.
Question: What is the purpose of the tunica interna?
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: What are the main functions of arteries? [2]
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: What are the two main types of arteries?
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: What is the function of elastic arteries during the cardiac cycle?
Answer: Elastic arteries expand when the pressure from ventricular systole increases and recoil when the ventricles relax, helping maintain continuous blood flow.
Question: How do muscular arteries differ from elastic arteries? [2]
Answer: Muscular arteries have less elastin and thicker smooth muscle, which causes less fluctuation in diameter compared to elastic arteries.
Question: What are arterioles and where are they located?
Answer: Arterioles are smaller branches of arteries within organs, responsible for regulating blood flow to specific tissues.
Question: What allows arterioles to adjust the blood flow to individual organs?
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: What is the primary role of arterioles in the circulatory system?
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: How is the tone (constriction or dilation) of arterioles controlled?
Answer: The tone of arterioles is controlled via nervous and chemical mechanisms, which regulate their constriction or dilation.
Question: What causes normal arteriolar tone? [8]
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: What happens during vasoconstriction in arterioles?
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: What happens during vasodilation in arterioles?
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: What are capillaries and where are they located?
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: How does exchange of materials occur in capillaries?
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: What features allow capillaries to facilitate exchange?
Answer: Capillary walls are perforated by water-filled pores, which allow the passage of small, water-soluble substances.
Question: What regulates blood flow through capillaries?
Answer: Precapillary sphincters regulate blood flow through capillaries by contracting and relaxing, depending on the body’s needs.
Question: What are the three main types of capillaries?
[CFS]
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: What are the characteristics of continuous capillaries?
[types of pores , where are they found]
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: What are the characteristics of fenestrated capillaries?
[types of pores , where are they found]
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: What are the characteristics of discontinuous (sinusoidal) capillaries?
[types of pores , where are they found]
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: What are the two main mechanisms of capillary exchange between blood and surrounding tissues?
Answer:
Passive diffusion: Movement of solutes down their concentration gradient.
Bulk flow: Ultrafiltration and reabsorption of protein-free plasma.
Question: What are the determinants of bulk flow in capillary exchange?[3]
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: How does passive diffusion differ from bulk flow in capillary exchange?
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: What is the role of the venous system in the circulatory system?
Answer: The venous system is a low resistance system that returns blood from tissues to the heart.
Question: What are the characteristics of systemic veins?
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: What does the venous system consist of?
Answer:
Venules
Small veins
Large, systemic veins
Question: How do veins ensure blood flows toward the heart?
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.
