Cardiovascular system

What are the three layers (tunics) of a blood vessel wall

Tunica intima (endothelium + subendothelial layer), tunica media (smooth muscle + elastic fibers), and tunica externa (connective tissue).

Which layer is thickest in arteries, and why

Tunica media; arteries need to withstand and regulate high-pressure blood flow using smooth muscle contraction and elasticity.

How does the tunica media differ between arteries, veins, and lymphatic vessels

Arteries have a thick tunica media with lots of smooth muscle and elastic fibers for pressure control; veins have a thinner tunica media with less muscle since they operate under low pressure; lymphatic vessels have the thinnest tunica media, relying on valves and external muscle movement for flow.

Which vessels contain valves, and what’s their purpose

Veins and lymphatic vessels; prevent backflow in low-pressure flow, especially in limbs.

What are the three types of capillaries and where are they found

Continuous (most tissues), Fenestrated (kidneys, endocrine glands), Discontinuous/Sinusoidal (liver, spleen, bone marrow).

What is a metarteriole and its function

A small vessel connecting arterioles to venules; precapillary sphincters regulate blood flow through capillaries.

What are baroreceptors and where are they located

Pressure sensors in carotid sinuses and aortic arch that detect BP changes and send signals to the medulla.

How does the body respond to high blood pressure

Baroreceptors trigger the cardioinhibitory center → slower HR and vasodilation → lower BP.

How does the body respond to low blood pressure

Baroreceptors reduce firing → cardioacceleratory center increases HR and vasoconstriction → raises BP.

Difference between hypertension and hypotension

Hypertension = long-term high BP; Hypotension = low BP that can lead to shock.

What instrument measures blood pressure

Sphygmomanometer (from Étienne-Jules Marey’s sphygmanograph).

How does total cross-sectional area of blood vessels affect blood flow velocity

Blood velocity is inversely related to total cross-sectional area; flow is slowest in capillaries (large total area) to allow time for exchange.

How does blood pressure change as blood moves through the circulatory system

Pressure is highest in arteries, decreases through arterioles and capillaries, and is lowest in veins due to friction and distance from the heart.

How does blood distribution change during exercise

Blood shifts from digestive/renal organs to skeletal muscles and skin.

What causes portal hypertension and ascites

Blocked or damaged liver vessels increase portal vein pressure → fluid leaks into abdomen (ascites).

What is the purpose of valves in veins

Prevent blood backflow when returning blood to the heart under low pressure.

What physiological mechanism assists venous return

The muscular pump—skeletal muscle contractions push blood through veins.

What does a thick left ventricle indicate functionally

It pumps blood through the systemic circuit, requiring more force.

What happens if the precapillary sphincters close

Blood bypasses capillary beds via the metarteriole to maintain minimal flow.

What condition could result from baroreceptor dysfunction

Chronic hypertension or hypotension due to poor pressure regulation.