MCAT Biology : Blood Vessels and Vasculature

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

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Example Question #871 : Biology

Nutrients absorbed in the small intestine follow which of the following pathways before entering the tissues of the body?

Possible Answers:

Hepatic portal circulation -> liver -> vena cava -> heart

Vena cava -> heart -> hepatic portal circulation -> liver

Liver -> hepatic portal circulation -> vena cava -> heart

Vena cava -> heart -> liver -> hepatic portal circulation

Correct answer:

Hepatic portal circulation -> liver -> vena cava -> heart

Explanation:

It is important to remember that these nutrients go through the liver before entering the general circulation. Amino acids and carbohydrates are absorbed through the intestine's epithelial cells into the hepatic portal circulation, then to the liver, through the inferior vena cava, and finally into the heart. From the heart, these nutrients are pumped from the left ventricle to the rest of the body's tissues.

Example Question #21 : Blood Vessels And Vasculature

Of the listed answer choices, where would you expect blood pressure to be highest during normal, healthy circulation?

Possible Answers:

Venules

Capillaries

Veins

Arterioles

Correct answer:

Arterioles

Explanation:

Of the available answer choices, we would expect blood pressure to be the highest in the arterioles because they are closest to the aorta and major arteries, from where blood is directly pumped. Of the choices blood pressure is greatest in the arterioles and lowest in the veins.

Note that overall blood pressure is highest in the aorta, however the question specifies that we are only looking a a select portion of answers.

Example Question #22 : Blood Vessels And Vasculature

Which of the following vessels serves as the body's reservoir of blood?

Possible Answers:

Capillaries

Arterioles and arteries

Veins and venules

Arterioles and capillaries

Correct answer:

Veins and venules

Explanation:

Veins and venules hold approximately 65% of blood in the body at rest. Because of their large luminal diameters, veins are capable to storing much of blood in the human body.

Arteries carry blood away from the heart and have thick, elastic layers that allow for build up of high pressures due to high volume flow. Capillaries are the smallest vessels in the body, and act to facilitate exchange of gas, nutrients, and waste products between blood and tissues. 

Example Question #23 : Blood Vessels And Vasculature

 

In which component of the circulatory system is blood flowing the fastest?

Possible Answers:

Arterioles

Right ventricle

Aorta

Veins

Capillaries

Correct answer:

Aorta

Explanation:

Once blood enters the left ventricle, the left ventricle contracts and pushes blood out of the heart into the aorta. The contraction of the left ventricle pumps blood into the aorta at a fast velocity. Blood velocity becomes slower as it reaches the capillaries and then speeds up again in the veins. Veins must use valves to pump blood against gravity, and therefore does not move blood as quickly as the aorta. The aorta is the best answer.

Example Question #21 : Blood Vessels And Vasculature

Where would one find the most deoxygenated blood?

Possible Answers:

Left ventricle

Left atrium

Pulmonary arteries

Aorta

Femoral artery

Correct answer:

Pulmonary arteries

Explanation:

The circulatory system follows both the systemic and pulmonary circuits. Deoxygenated blood is returned from the systemic circuit through the vena cavae into the right atrium. It then goes into the right ventricle after passing through the tricuspid valve. From the right ventricle it enters the pulmonary circuit through the pulmonary artery, which carries deoxygenated blood from the right ventricle to the lungs, where it gets oxygenated. From the lungs it goes through the pulmonary veins into the left atrium. From the left atrium it goes into the left ventricle through the mitral valve, and is returned to the systemic circuit through the aorta.

Deoxygenated blood would be found in mostly in systemic veins, including the vena cavae, pulmonary arteries, and the right side of the heart. Oxygenated blood would be found in systemic arteries, such as the femoral artery, pulmonary veins, and the left side of the heart.

Example Question #81 : Circulatory And Respiratory Systems

The interaction between blood pressure and kidney function in humans requires coordination by the renin-angiotensin-aldosterone system (RAAS). This system involves the dynamic interplay of the kidneys, lungs, and blood vessels to carefully regulate sodium and water balance.

A normal human kidney has cells adjacent to the glomerulus called juxtaglomerular cells. These cells sense sodium content in urine of the distal convoluted tubule, releasing renin in response to a low level. Renin is an enzyme that converts angiotensinogen to angiotensin I (AI). AI is converted to angiotensin II (AII) by angiotensin converting enzyme (ACE) in the lung.

AII stimulates aldosterone secretion in the zona glomerulosa of the adrenal gland. Aldosterone then acts to upregulate the sodium-potassium pump on the basolateral side of distal tubule epithelial cells to increase sodium reabsorption from the urine, as well as increasing potassium excretion.

Angiotensin II is a potent vasoconstrictor. Vasoconstriction is most likely to be drive constriction of which of the following blood vessels?

Possible Answers:

Veins

Venules

Arteries

Non-fenestrated capillaries

Fenestrated capillaries

Correct answer:

Arteries

Explanation:

Arteries and arterioles have smooth muscle surrounding their endothelial walls that allows vasoconstrictors, such as angiotensin II or epinephrine, to increase blood pressure. Veins and venules may have limited constrictive abilities due to small amounts of smooth muscle interaction, but their effects on blood pressure are extremely small compared to those exerted by arteries and arterioles. Capillaries do not have smooth muscle, and are comprised of a singular layer of endothelial cells.

Example Question #82 : Circulatory And Respiratory Systems

The largest volume of blood is contained in which of the following types of vessel?

Possible Answers:

Venules 

Arterioles

Veins

Arteries

Correct answer:

Veins

Explanation:

It is important to understand the relative sizes of the vessels through which blood flows. After exiting the heart from the left ventricle, the blood enters the aorta, the largest artery. The blood then flows into smaller arterioles, into capillaries, back into venules, and eventually into the vena cavae, which return the blood to the heart.

The larger veins contain the largest volume of blood because they are the most distensible, meaning they can stretch to accommodate large volume. Arteries and arterioles are hampered by the smooth muscle surrounding them. Veins contain about 64% of the circulating blood, acting as blood reservoirs. Blood is constantly pushed through the arteries and arterioles from the pumping heart, but the pulse does not have a large effect on the veins. The veins instead rely on the actions of shunts to help return slow-flowing blood to the heart. The combination of slow blood flow and vessel flexibility allow the veins to store large blood volumes.

Example Question #83 : Circulatory And Respiratory Systems

Smooth muscle that surrounds arteries and arterioles in the systemic vasculature allows for both local and global control of blood pressure. Which of the following does not increase blood pressure by constricting smooth muscle?

Possible Answers:

Norepinephrine stimulation

Beta-adrenergic stimulation

Alpha-adrenergic stimulation

Epinephrine stimulation

Correct answer:

Beta-adrenergic stimulation

Explanation:

The smooth muscle that surrounds arteries and arterioles constricts when acted upon by sympathetic nervous stimulation (alpha-adrenergic receptors) and by the tyrosine-based hormones epinephrine and norepinephrine, which are produced and secreted from the adrenal medulla.

Beta-adrenergic receptors, in contrast, promote smooth muscle relaxation.

Example Question #84 : Circulatory And Respiratory Systems

The two main pressures found in capillary beds are oncotic pressure and hydrostatic pressure. Following the pathway from an arteriole to a venule (through a capillary bed), which of the following will have the biggest change in pressure from start to end?

Possible Answers:

Oncotic pressure—the oncotic pressure lowers as proteins exit into the interstitial fluid from the capillaries

Hydrostatic pressure—the hydrostatic pressure raises in the capillaries as fluid and nutrients are forced from the capillaries into the interstitial fluid

Oncotic pressure—the oncotic pressure raises as proteins exit into the interstitial fluid from the capillaries

Hydrostatic pressure—the hydrostatic pressure lowers in the capillaries as fluid is forced from the capillaries into the interstitial fluid

Correct answer:

Hydrostatic pressure—the hydrostatic pressure lowers in the capillaries as fluid is forced from the capillaries into the interstitial fluid

Explanation:

The hydrostatic pressure becomes much lower as blood travels through capillary beds. This is because the fluid pressue lessens as fluid leaves the inside of the capillaries and is forced into the interstitial fluid. The oncotic presssure remains relatively constant, since proteins are large and do not readily move across vessel walls. As fluids exit the capillary, the concentration of proteins within the vessel increases.

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