Learning Objectives

• Describe the main function and components of the circulatory system.

• Explain the structure of the heart and the path of blood circulation.

• Differentiate between the structure and function of arteries, veins, and capillaries.

• Identify the components of blood and describe their important functions.

• Recognize common cardiovascular diseases and ways to maintain a healthy heart.

Key Vocabulary

Artery

A type of blood vessel that carries blood away from the heart to the lungs or body.

Vein

A type of blood vessel that brings blood toward the heart from the lungs or the body.

The smallest blood vessel, connecting small arteries and veins found throughout the body.

Blood Pressure

The force that is exerted by circulating blood on the walls of the blood vessels.

Pulmonary Circulation

The part of the circulatory system carrying deoxygenated blood between the heart and the lungs.

Systemic Circulation

The part of the circulatory system carrying oxygenated blood between the heart and the body.

Capillary

The Heart

• The heart is a muscular, fist-sized organ that pumps blood throughout the body.

• It has four chambers: two upper atria and two lower ventricles.

• Valves ensure one-way blood flow; their closing creates the heartbeat sound.

• The pacemaker, in the right atrium, sends electrical signals to regulate the heartbeat.

The Three Major Types of Blood Vessels

Arteries

• ​Carry blood away from the heart to the body.

• ​​Have thick, muscular walls to handle high blood pressure.

• ​Transport blood that is typically rich in oxygen.

Veins

• ​Carry blood from the body back toward the heart.

• ​​Their walls are thinner and less muscular than arteries.

• ​Transport blood that is typically low in oxygen.

Capillaries

• ​Are the smallest and most numerous blood vessels.

• ​​Connect arteries and veins, forming vast networks.

• ​Allow exchange of oxygen, nutrients, and waste products.

Components of Blood

• Plasma is the golden-yellow fluid part of blood that carries other blood cells.

• Red blood cells contain hemoglobin, a protein that carries oxygen throughout the body.

• White blood cells are part of the immune system and fight against pathogens.

• Platelets are small cell fragments that help your blood to clot after an injury.

Path of Blood Flow

Pulmonary Circuit

• Carries oxygen-poor blood from the heart to the lungs to pick up oxygen.

• Blood flows from the right atrium to the right ventricle and then to the lungs.

• In the lungs, blood drops off carbon dioxide and collects a fresh supply of oxygen.

Systemic Circuit

• Carries oxygen-rich blood from the heart to all other parts of the body.

• Blood flows from the left atrium to the left ventricle and out through the aorta.

• After delivering oxygen, the blood returns to the heart to start the cycle again.

Cardiovascular Health

• Cardiovascular disease (CVD) affects the heart and blood vessels.

• Atherosclerosis is when plaque builds up in arteries, reducing blood flow.

• Hypertension, or high blood pressure, puts extra force on artery walls.

• Regular exercise and a healthy diet help keep your heart strong.

Common Misconceptions

Summary

• The circulatory system transports oxygen, nutrients, and waste through the body.

• The heart pumps blood through the pulmonary circuit to the lungs and the systemic circuit to the body.

• Arteries carry blood away from the heart, veins return it, and capillaries connect them.

• A healthy lifestyle with a balanced diet and exercise is crucial for heart health.