Cardiovascular System

Cardiovascular system

Circulates blood and oxygen throughout the body.

Heart, arteries, veins, capillaries

Components of the cardiovascular system

Human circulatory system

System responsible for transporting blood, oxygen, and nutrients to the body.

Heart, blood vessels, blood

Three main parts of the circulatory system

Functions of the circulatory system

Protection, blood production, waste excretion, blood clotting, and nutrient transport.

Protection

White blood cells help defend the body from diseases and infections.

Blood production

Bone marrow produces stem cells that develop into blood cells.

Waste excretion

Blood carries waste products to excretory organs for elimination.

Blood clotting

Platelets close wounds and promote healing by coagulation.

Nutrients for cells

Blood carries vitamins, minerals, and proteins to cells.

Tunica intima, tunica media, tunica adventitia

Three main layers of the circulatory system wall

Tunica intima

Inner lining made up of endothelium, subendothelium, and internal elastic lamina.

Endothelium

Single layer of flattened epithelial cells (simple squamous epithelium).

Subendothelium

Basement membrane of loose connective tissue with few smooth muscle cells.

Internal elastic lamina (IEM)

Thin band of elastic fibers separating tunica intima from tunica media.

Tunica media

Middle muscular layer made of smooth muscle cells and elastic fibers.

External elastic lamina (EEM)

Separates tunica media from tunica adventitia.

Tunica adventitia (tunica externa)

Outer supporting layer made of Type I collagen and elastic fibers.

Heart

Muscular organ that pumps blood through the body; has four chambers: two atria (upper) and two ventricles (lower).

Blood flow through the heart

1. Right atrium receives deoxygenated blood.

2. Blood moves to right ventricle and goes to lungs for oxygenation.

3. Left atrium receives oxygenated blood from lungs.

4. Left ventricle pumps oxygenated blood to the body.

Epicardium

Outermost layer; made of connective tissue and epithelium; protects and reduces friction.

Myocardium

Thick middle layer of cardiac muscle; responsible for heart contractions.

Endocardium

Innermost layer; endothelial lining of chambers and valves.

Four chambers

Two atria (upper) and two ventricles (lower).

Atria

Receive blood returning to the heart.

Ventricles

Pump blood out of the heart.

Right atrium

Receives deoxygenated blood from the body via superior and inferior vena cava; pumps through tricuspid valve to right ventricle.

Left atrium

Receives oxygenated blood from lungs via pulmonary veins; pumps through mitral valve to left ventricle.

Right ventricle

Pumps deoxygenated blood through pulmonary valve to pulmonary artery → lungs.

Left ventricle

Pumps oxygenated blood through aortic valve to aorta → body.

Tricuspid valve

Between right atrium and right ventricle; 3 flaps; opens in diastole, closes in systole to prevent backflow.

Pulmonary valve

Between right ventricle and pulmonary artery; 3 flaps; controls blood flow to lungs.

Mitral valve

Between left atrium and left ventricle; 2 flaps; allows oxygenated blood to enter left ventricle.

Aortic valve

Between left ventricle and aorta; 3 flaps; allows blood into aorta during systole.

Systole

Heart contraction.

Diastole

Heart relaxation.

Blood vessels

Tubes that transport blood; include arteries, veins, and capillaries.

Artery

Thick-walled vessel that carries blood away from the heart under high pressure.

Capillary

Thinnest vessel; allows exchange of oxygen, nutrients, and wastes between blood and tissues.

Vein

Less muscular vessel that carries blood back to the heart under low pressure; contains valves to prevent backflow.

Aorta

Largest artery; carries oxygenated blood from left ventricle to body.

Pulmonary artery

Carries deoxygenated blood from right ventricle to lungs.

Elastic arteries

Largest arteries (aorta, pulmonary trunk, carotid, subclavian, iliac); contain many elastic fibers.

Muscular arteries

Medium-sized distributing arteries branching from elastic arteries.

Arterioles

Smallest arteries; deliver blood to capillaries.

Structural pattern of arteries

Tunica intima with endothelium, subendothelial tissue, and internal elastic membrane.

Arterial wall characteristics

Thick tunica media; rigid even after death; small lumen compared to wall thickness.

Veins

Return deoxygenated blood to the heart; walls thinner than arteries; have valves.

Superior vena cava

Returns deoxygenated blood from upper body.

Inferior vena cava

Returns deoxygenated blood from lower body.

Pulmonary veins

Four veins (two per lung); carry oxygenated blood from lungs to heart.

Capillaries

Tiny, thin-walled vessels connecting arteries and veins; site of exchange between blood and tissues.

Continuous capillaries

Most common; complete endothelial lining with tight junctions for controlled exchange.

Fenestrated capillaries

Contain pores allowing more exchange (found in kidneys, intestines, endocrine glands).

Discontinuous capillaries (sinusoids)

Have gaps and incomplete membranes; allow large molecules through (found in liver, spleen, bone marrow).

Blood

Specialized fluid circulating in vessels; transports oxygen, nutrients, and waste.

Red blood cells

Carry oxygen and nutrients; remove carbon dioxide.

White blood cells

Defend against disease and infection.

Platelets

Help in blood clotting and wound healing.

Plasma

Straw-colored liquid carrying blood cells, nutrients, hormones, and waste.