Chapter 21 Cardiovascular System

A vein is a blood vessel that carries blood from the tissues back to the heart. Unlike arteries, which carry oxygenated blood away from the heart, veins carry deoxygenated blood back to the heart to be reoxygenated. Veins have thinner walls and less elasticity compared to arteries, as the blood flow in veins is under lower pressure. Veins also have valves that prevent the backflow of blood. Overall, veins play a crucial role in the circulatory system by returning blood to the heart for oxygenation and nutrient replenishment.

The pulmonary trunk is a blood vessel that carries deoxygenated blood from the right ventricle of the heart to the lungs. It divides into the right and left pulmonary arteries, which then carry the deoxygenated blood to the right and left lungs, respectively. These arteries further branch out into smaller vessels within the lungs, allowing for the exchange of oxygen and carbon dioxide between the blood and the air sacs in the lungs. Therefore, the correct answer is "right and left pulmonary arteries".

The tunica media is responsible for vasoconstriction. This layer of the artery wall contains smooth muscle cells that can contract and relax to regulate the diameter of the blood vessel. When the smooth muscle cells contract, the blood vessel constricts, leading to vasoconstriction. This helps regulate blood flow and blood pressure. The tunica interna is the innermost layer of the artery wall and is responsible for providing a smooth surface for blood flow. The tunica externa is the outermost layer and provides support and protection to the artery. The tunica albuginea is a different structure found in the testes and ovaries and is not related to vasoconstriction.

Diffusion is the most important capillary exchange method because it is the primary mechanism by which molecules move across the capillary walls. Diffusion occurs due to the concentration gradient between the capillary and surrounding tissues, allowing small molecules such as oxygen, carbon dioxide, and nutrients to pass through the capillary walls. This process is crucial for the exchange of gases and nutrients between the bloodstream and the surrounding tissues. Transcytosis, bulk flow, and active transport also play roles in capillary exchange, but diffusion is the most significant and prevalent method.

When an artery or arteriole is damaged, the smooth muscle in the vessel wall contracts, causing a decrease in the diameter of the blood vessel. This contraction is known as a vascular spasm. The purpose of a vascular spasm is to reduce blood flow to the damaged area, which helps to prevent excessive bleeding. It is a protective mechanism that occurs in response to injury and is part of the body's natural response to minimize blood loss and promote healing.

Arterioles are small blood vessels that connect arteries to capillaries. They play a crucial role in regulating blood flow into capillaries by constricting or dilating their walls. This constriction and dilation help control blood pressure and distribute blood to different organs and tissues according to their needs. Therefore, arterioles are responsible for regulating blood flow into capillaries, making them the correct answer.

The radial artery is a pulse point at the wrist. It is located on the thumb side of the wrist and is commonly used to measure the pulse rate. It is easily accessible and can be felt by placing two fingers (usually the index and middle fingers) on the inner side of the wrist, just below the base of the thumb. The radial artery is an important artery that supplies blood to the hand and forearm.

The mesenteric artery supplies blood to the intestine. This artery branches off from the abdominal aorta and delivers oxygenated blood to the small and large intestines. It plays a crucial role in providing nutrients and removing waste products from the intestines.

Valves are not found in arteries but are found in veins. Valves in veins help to prevent the backflow of blood and ensure that blood flows in one direction towards the heart. Arteries, on the other hand, have thicker walls with three layers known as tunica externa, tunica media, and tunica interna. These layers provide strength and elasticity to the arteries, allowing them to withstand the high pressure of blood being pumped from the heart.

The renal artery is the correct answer because it is the blood vessel that supplies blood to the kidney. The hepatic artery supplies blood to the liver, the mesenteric artery supplies blood to the intestines, and the coronary artery supplies blood to the heart.

The tibial vein is the correct answer because it is responsible for draining blood from the lower leg. The jugular vein drains blood from the head and neck, the superior vena cava drains blood from the upper body, and the coronary vein drains blood from the heart. However, none of these vessels are specifically responsible for draining blood from the lower leg.

Blood osmotic pressure is the correct answer because it is the force that draws fluid back into the blood vessels from the interstitial fluid. Osmotic pressure is created by the concentration of solutes, such as proteins, in the blood. This concentration gradient causes water to move from an area of lower solute concentration (interstitial fluid) to an area of higher solute concentration (blood vessels), promoting reabsorption of fluids into the blood. Tissue hydrostatic pressure, tissue osmotic pressure, and blood hydrostatic pressure do not directly promote reabsorption of fluids into the blood from the interstitial fluid.

Capillaries are known as exchange vessels because they are the smallest blood vessels in the body and they play a crucial role in the exchange of oxygen, nutrients, and waste products between the blood and the surrounding tissues. Capillaries have thin walls that allow for the efficient exchange of substances, such as oxygen and carbon dioxide, through a process called diffusion. This exchange of substances is essential for the proper functioning of organs and tissues in the body.

A decreased cardiac output means that the heart is pumping less blood per minute. Since blood pressure is determined by the force of blood against the walls of the blood vessels, a decreased cardiac output would result in less blood being pumped and therefore lower blood pressure. Therefore, a decreased cardiac output would not increase blood pressure.

The cardiovascular center is located in the medulla oblongata. This is because the medulla oblongata is a part of the brainstem that controls many vital functions, including the regulation of heart rate and blood pressure. It receives sensory information from the body and sends out appropriate signals to adjust the cardiovascular system accordingly. The medulla oblongata acts as a control center for maintaining homeostasis in the cardiovascular system, making it the correct answer.

Continuous capillaries can be found in skeletal muscle, smooth muscle, and connective tissue. Continuous capillaries are characterized by their continuous endothelial lining, which forms a tight barrier between the blood and surrounding tissues. This type of capillary allows for the exchange of nutrients, gases, and waste products between the blood and the tissues. Skeletal muscle, smooth muscle, and connective tissue all require a constant supply of oxygen and nutrients, making continuous capillaries essential for their proper functioning. Therefore, the correct answer is "ALL OF THE ABOVE."

The correct answer is "IN A RESTING PERSON IS NORMALLY ONE MINUTE". This suggests that in a person who is at rest, the circulation time, which refers to the time it takes for blood to circulate through the entire body, is typically one minute. This implies that the blood flows efficiently through the circulatory system, delivering oxygen and nutrients to the body's tissues and organs within a relatively short period of time.

The given correct answer states that the superficial temporal artery, brachial artery, and dorsal artery of the foot are all pulse points. This means that these arteries are easily accessible and can be used to palpate or measure the pulse in order to assess the heart rate and rhythm.

The correct answer is FORAMEN OVALE. In fetal circulation, there is a temporary opening between the right and left atria called the foramen ovale. This opening allows oxygenated blood from the placenta to bypass the non-functioning fetal lungs and enter the left atrium, where it can be pumped out to the rest of the body. After birth, the foramen ovale closes and becomes a small depression known as the fossa ovalis.

Veins and venules make up the largest blood reservoir because they have a larger total cross-sectional area compared to arteries and arterioles. This allows them to hold a larger volume of blood at any given time. Additionally, veins have thinner walls and less elastic tissue than arteries, allowing them to expand and accommodate more blood. Venules, which are small veins, also contribute to the blood reservoir by collecting blood from capillaries and delivering it to larger veins.

Arteries are the blood vessels that distribute oxygenated blood from the heart to various parts of the body. They carry oxygen-rich blood away from the heart to deliver it to the tissues and organs. Arteries have thick, elastic walls that help maintain blood pressure and facilitate the flow of blood. Capillaries, on the other hand, are the smallest blood vessels where the exchange of oxygen and nutrients with tissues occurs. Veins, in contrast, carry deoxygenated blood back to the heart.

Elastic arteries are responsible for maintaining blood pressure and acting as a pressure reservoir. These arteries have a high amount of elastic fibers in their walls, allowing them to stretch and recoil in response to the force exerted by the blood flow. This elasticity helps to maintain continuous blood flow during diastole (relaxation phase of the heart) and prevents a sudden drop in pressure. Therefore, elastic arteries serve as a pressure reservoir, ensuring a constant blood supply to the tissues and organs.

Chemoreceptors in blood vessels measuring high levels of blood carbon dioxide would not cause decreased respiratory rate. When blood carbon dioxide levels are high, chemoreceptors in the blood vessels detect this and send signals to the respiratory centers in the brain to increase the respiratory rate. This is done to remove excess carbon dioxide from the body through increased breathing. Therefore, the correct answer is that increased levels of blood carbon dioxide would not cause a decreased respiratory rate.

The jugular vein is the correct answer because it is responsible for draining blood from the head and neck. It is a large vein that carries deoxygenated blood from the brain, face, and neck back to the heart. The carotid vein is incorrect because it carries oxygenated blood from the head to the heart. The inferior vena cava is incorrect because it drains blood from the lower body. The axillary vein is incorrect because it drains blood from the armpit region. Therefore, the jugular vein is the only option that correctly matches the given description.

The inferior vena cava is the correct answer because it is the largest vein in the body that carries deoxygenated blood from the lower body to the right atrium of the heart. The superior vena cava also carries deoxygenated blood, but it drains blood from the upper body to the right atrium. The tibial vein is a vein in the leg, and the coronary vein is a vein that drains blood from the heart muscle.

Collateral circulation refers to the alternate route of blood flow to a body part through an anastomosis. Anastomosis is a connection between two blood vessels, allowing blood to flow from one vessel to another. In cases where there is a blockage or restriction in the main blood vessel supplying a particular body part, collateral circulation helps to maintain blood supply to that area by redirecting blood flow through the anastomosis. This mechanism ensures that the tissues receive adequate oxygen and nutrients, preventing damage or dysfunction.

Capillaries are the smallest blood vessels in the body and connect arteries to veins. They are responsible for the exchange of oxygen, nutrients, and waste products between the blood and surrounding tissues. Unlike arteries and veins, capillaries have thin walls and a small diameter, which allows for efficient diffusion of substances. Due to their small size and delicate structure, the pulse cannot be felt in capillaries. The pulsation of the heartbeat is only noticeable in larger blood vessels like arteries, where the pressure of the blood flow is higher.

The tunica externa is the correct answer because it is the outermost layer of the artery and is primarily made up of elastic and collagen fibers. These fibers provide strength and support to the artery, allowing it to withstand the pressure and forces exerted on it. The tunica externa also contains blood vessels that supply nutrients to the artery.

Blood flow refers to the volume of blood that moves through any tissue in a given time period. It is a measure of the rate at which blood circulates in the body. Blood flow is essential for delivering oxygen and nutrients to tissues, as well as removing waste products. It is influenced by factors such as blood pressure, the diameter of blood vessels, and the viscosity of blood. Understanding blood flow is crucial in assessing the health and functionality of various tissues and organs in the body.

Blood flow depends on both blood pressure and systemic vascular resistance. Blood pressure is the force exerted by the blood against the walls of the blood vessels, and it is necessary for the blood to flow through the circulatory system. Systemic vascular resistance refers to the resistance encountered by the blood as it flows through the blood vessels. When blood pressure is high and systemic vascular resistance is low, blood flow increases. Conversely, when blood pressure is low and systemic vascular resistance is high, blood flow decreases. Therefore, both blood pressure and systemic vascular resistance play a crucial role in determining blood flow.

The myogenic response refers to the ability of smooth muscles to contract more forcefully when they are stretched. This response helps to maintain blood flow and regulate blood pressure in various organs and tissues. When smooth muscles are stretched, it triggers a reflexive contraction to prevent overstretching and maintain the appropriate tension. This mechanism is essential for the proper functioning of organs such as blood vessels and the urinary bladder.

The correct answer is "SUPER AND INFERIOR VENA CAVA AND CORONARY SINUS". This is because the systemic circulation is responsible for carrying oxygenated blood from the heart to the rest of the body and returning deoxygenated blood back to the heart. The veins of the systemic circulation drain into the superior vena cava, inferior vena cava, and coronary sinus, which then deliver the deoxygenated blood to the right atrium of the heart. Therefore, all of these vessels play a role in draining the veins of the systemic circulation.

Blood viscosity refers to the thickness or stickiness of blood. It is determined by the concentration of red blood cells (RBC) and plasma in the blood. When the ratio of RBC to plasma volume is higher, the blood becomes more viscous. This increased viscosity can affect blood flow and put more strain on the heart and blood vessels. Therefore, blood viscosity plays a significant role in determining the resistance to blood flow and overall cardiovascular health.

Atrial natriuretic peptide (ANP) is a hormone released by the heart in response to increased blood volume and pressure. It acts to decrease blood pressure by promoting vasodilation and increasing urine production, which leads to the excretion of sodium and water. Therefore, ANP would not cause an increase in blood pressure.

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Muscular activity is the most important factor in forcing blood flow through veins. When muscles contract and relax during physical activity, they squeeze the veins and help push the blood towards the heart. This action is known as the skeletal muscle pump. It increases venous return and helps maintain proper blood circulation throughout the body. Heart rate, stroke volume, and blood velocity also play a role in blood flow, but muscular activity has a more direct and immediate impact.

Filtration is the correct answer because it refers to the pressure-driven movement of fluids and solutes from blood into interstitial fluid. This process occurs across a semipermeable membrane, allowing smaller molecules to pass through while retaining larger molecules. Filtration is an important mechanism in various physiological processes, such as the formation of urine in the kidneys and the exchange of nutrients and waste products between blood vessels and tissues.

Pulse pressure is the difference between systolic and diastolic blood pressure. It provides information about the condition of the cardiovascular system, such as atherosclerosis and patent ductus arteriosus. A high pulse pressure may indicate stiff arteries or increased risk of cardiovascular disease, while a low pulse pressure may suggest reduced cardiac output or heart failure. Therefore, monitoring pulse pressure can help detect abnormalities in the cardiovascular system and guide further diagnosis and treatment.

This layer consists of a lining of simple squamous epithelium, a basement membrane, and a layer of elastic tissue. The correct answer is A.

After birth, when the umbilical cord is cut off, the umbilical arteries fill with connective tissue. This is because the umbilical arteries, which were previously responsible for carrying deoxygenated blood from the fetus to the placenta, undergo a process called obliteration. During this process, the arteries close off and are gradually replaced by connective tissue, eventually forming the remnants of the umbilical cord known as the umbilical ligaments.

Decreased vessel length does not increase systemic vascular resistance because systemic vascular resistance is determined by the total length of blood vessels in the systemic circulation. When the length of blood vessels decreases, there is less resistance to blood flow, resulting in a decrease in systemic vascular resistance.

A decrease in the frequency of action potentials arising from the baroreceptors would result in decreased parasympathetic stimulation. This would lead to a decrease in heart rate and stroke volume. However, it would also result in a decrease in the inhibitory signals sent to the vasomotor center in the brainstem, causing an increase in sympathetic stimulation and ultimately leading to increased blood pressure.

Hypovolemic shock is characterized by a decrease in blood volume, which can be caused by severe bleeding, dehydration, or fluid loss. In this type of shock, the body does not have enough blood to adequately perfuse the organs and tissues, leading to decreased oxygen delivery and organ dysfunction. Increased blood volume is not associated with hypovolemic shock, as it is the opposite condition. Cardiogenic shock is caused by a failure of the heart to pump effectively, vascular shock is caused by widespread vasodilation and low systemic vascular resistance, and obstructive shock is caused by a mechanical obstruction of blood flow.

The correct answer is B because capillary walls commonly found in the kidneys, villi of the small intestine, choroid plexuses, and some endocrine glands are known as fenestrated capillary walls. Fenestrated capillaries have small pores or fenestrations in their endothelial cells, allowing for increased permeability and the rapid exchange of fluids and solutes between the blood and surrounding tissues. This type of capillary is especially suited for filtration and absorption processes in organs like the kidneys and small intestine.

The figure represents the mechanism of the skeletal muscle pump. The skeletal muscle pump is a mechanism in which the contraction of skeletal muscles helps in the movement of venous blood back to the heart. This pumping action occurs when the muscles contract and squeeze the veins, pushing the blood towards the heart. It is an important mechanism in maintaining venous return and preventing blood pooling in the lower extremities.

The given correct answer is B. This is because the layer described in the statement, consisting mainly of elastic fibers and smooth muscle fibers that extend circularly around the lumen, is known as the muscularis externa. This layer is responsible for the contraction and relaxation of the gastrointestinal tract, allowing for the movement of food through the digestive system.

The release of vasoconstrictors is not a response to hypovolemic shock. Hypovolemic shock occurs when there is a significant loss of blood volume, leading to a decrease in blood pressure. In response to hypovolemia, the body activates the renin-angiotensin-aldosterone (RAA) system, which helps to increase blood volume and blood pressure. The secretion of antidiuretic hormone (ADH) also occurs, which promotes water reabsorption by the kidneys, further increasing blood volume. Additionally, the sympathetic division of the autonomic nervous system is activated, causing vasoconstriction to maintain blood pressure. However, the release of vasoconstrictors is not a specific response to hypovolemic shock.

The metarteriole is located at position B.

Thoroughfare channels are responsible for controlling the flow of blood through a capillary bed. These channels provide a direct pathway for blood to flow from arterioles to venules without passing through capillaries. They bypass the capillaries when they are closed and allow blood to flow through them when they are open. This regulation of blood flow helps in maintaining proper oxygen and nutrient supply to tissues and organs.

The correct answer is C because if a capillary wall has an incomplete or absent basement membrane, it means that both options A and B are true. Option A refers to a capillary wall with an incomplete basement membrane, while option B refers to a capillary wall with an absent basement membrane. Therefore, option C, which includes both A and B, is the correct answer.