ANATOMY: 1.4 - the circulatory system

Components of the circulatory system

Heart, blood vessels, and blood

Heart

A muscular pump made of cardiac muscle that sends blood to the lungs and body

Blood vessels

A system of hollow tubes that transport blood

Blood

A fluid that carries substances like oxygen, nutrients, and waste

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Pulmonary circulation

Right side of heart sends deoxygenated blood to lungs

Systemic circulation

Left side of heart sends oxygenated blood to the body

Why do we need valves?

To prevent backflow of blood when the heart contracts

Atrioventricular valves

Prevent blood from flowing from ventricles back into the atria

Semilunar valves

Prevent blood from flowing back into ventricles from arteries

Which chambers have thicker walls?

Ventricles have thicker walls than atria because they pump blood farther

Why is the left ventricle thicker than the right?

It pumps blood to the entire body, requiring more force

Pericardium

A protective sac around the heart; anchors it, reduces friction, prevents overfilling and infection

What direction does blood flow in veins?

Toward the heart

What direction does blood flow in arteries?

Away from the heart

How thick are vein walls?

Thinner walls, larger internal diameter due to lower pressure

How think are the walls of arteries?

Thicker walls due to higher pressure

How elastic are veins?

Less elastic because they are under low pressure

How elastic are arteries?

More elastic to handle high pressure

Do veins have valves?

Yes; valves and skeletal muscles help maintain one-way blood flow

Do arteries have valves?

No; rely on pressure and elasticity for one-way blood flow

What helps maintain blood flow in veins?

Skeletal muscles and valves

What to valves in veins do When muscles are relaxed

Valves in veins close

What do valves do in veins When muscles contract

Valves above contract and push blood upward

Varicose veins

Occur when valves fail and blood pools or flows the wrong way

Capillaries

Tiny vessels with one-cell-thick walls where gas/nutrient exchange occurs

Function of capillaries

Connect arterioles to venules; enable diffusion of substances

Plasma

Liquid portion of blood; mostly water with dissolved nutrients, gases, wastes, and more

Red blood cells (erythrocytes)

Transport oxygen; no nucleus to make room for hemoglobin

Hemoglobin

Protein that binds oxygen; contains iron and 4 heme groups

White blood cells (leukocytes)

Fight infection using phagocytosis or antibody production

Platelets (thrombocytes)

Cell fragments that help with blood clotting

What does the circulatory system transport?

Transports O2, nutrients, and waste between systems and cells

What can the circulatory system do in terms of temperature regulation?

It can help cool the body when hot and warm the body when cold

What does the circulatory system protect you from?

Protects from disease-causing pathogens and blood loss

How does blood help regulate temperature?

Blood vessels expand or constrict to control heat loss through the skin

Vasoconstriction

Vessels get smaller; less blood near skin; body stays warmer

Vasodilation

Vessels widen; more blood near skin; heat is lost and body cools