Circulatory System: Blood Vessels, Heart, and Fetal Circulation

What are arteries?

Efferent vessels carrying blood away from the heart.

What are veins?

Afferent vessels carrying blood toward the heart.

What are capillaries?

Microscopic vessels connecting small arteries to small veins, important for gas and nutrient exchange.

What are the three layers of blood vessel walls?

Tunica interna (intima), tunica media, and tunica externa (adventitia).

What is the function of the tunica interna?

It is the inner layer made of simple squamous endothelium, providing a slick lining for smooth blood flow.

What is the role of the tunica media?

It is the middle layer responsible for vasoconstriction and vasodilation, containing smooth muscle and collagen.

What does the tunica externa do?

It is the outer layer made of loose connective tissue that anchors the vessel to its surroundings.

What are conducting arteries?

Largest arteries that absorb and maintain pressure; example: aorta.

What are distributing arteries?

Midsized arteries that distribute blood to specific organs; example: femoral artery.

What are resistance arteries?

Smallest arteries leading to capillary beds, containing precapillary sphincters.

What is the function of capillaries?

They are exchange vessels where nutrients, wastes, and hormones move between blood and tissue fluid.

What is a continuous capillary?

Capillaries with endothelial cells joined by tight junctions, found in most organs.

What is a fenestrated capillary?

Capillaries with filtration pores facilitating exchange, commonly found in the kidneys.

What is a sinusoid capillary?

Discontinuous capillaries with irregular passages and wide gaps, found in the liver and spleen.

What happens to precapillary sphincters when a tissue is active?

They relax (open) and capillaries fill with blood.

What are capacitance vessels?

Veins that contain most of the blood at any given time in the circulatory system.

What are postcapillary venules?

Very porous veins that allow for some exchange.

What are muscular venules?

Venules with smooth muscle in the wall (tunica media).

What are the major types of veins?

Medium veins (individually named, contain valves) and large veins (smooth muscle in all tunics).

What is the skeletal muscle pump?

Muscle activity squeezes veins and forces blood through one-way valves toward the heart.

What is a portal system?

A sequence of two capillary beds.

What is an anastomosis?

A vessel merger without an intervening capillary bed.

What is the pulmonary trunk?

An unpaired vessel that carries oxygen-poor blood from the right ventricle.

What do pulmonary veins carry?

Oxygen-rich blood from the lungs to the left atrium.

What is the hepatic portal vein?

It carries blood from the gastrointestinal tract to the liver before returning to the heart.

What is arteriosclerosis?

The stiffening of vessels that generally occurs due to old age.

What is atherosclerosis?

The growth of lipid deposits in arterial walls, often due to poor lifestyle choices or aging.

What are the changes at birth in fetal circulation?

Closure of foramen ovale, constriction of ductus arteriosus, and degeneration of umbilical arteries and veins.

What is the function of the foramen ovale in fetal circulation?

It allows blood to bypass the lungs by flowing directly from the right atrium to the left atrium.