1. 33.1 The Circulatory System
Lesson Overview
33.1 The Circulatory System

2. Functions of the Circulatory System
The circulatory system transports oxygen and nutrients to the body tissues, and removes wastes from tissues.
A city’s transportation system is a network of streets and highways that deliver goods to the city and remove wastes from it.
Similarly, the human body’s major transportation system is a system made up of a heart, blood vessels, and blood.

3. Blood Vessels: Arteries
Arteries = carry blood away from the heart to the tissues of the body
Arteries have thick walls that help them withstand the powerful pressure produced when the heart contracts and pumps blood through them.
Smooth muscle regulates the diameter of arteries
Except for the pulmonary arteries, all arteries carry oxygen-rich blood.

4. Capillaries The smallest blood vessels are the capillaries.
Most are so narrow that blood cells pass through them in single file.
Capillaries = exchange substances between body and blood
Their extremely thin walls allow oxygen and nutrients to diffuse from blood into tissues, and carbon dioxide and other waste products to move from tissues into blood.

6. Veins
After blood passes through the capillaries, it returns to the heart through veins
Veins contain oxygen-poor blood, except for the pulmonary vein [which carries oxygen-rich blood from the lungs to the heart]
Blood often must flow against gravity so many veins are located between skeletal muscles that squeeze the veins and push blood toward the heart.
Veins contain valves that close to ensure blood continues to flow in one direction

7. Draw the vessels and summarize their details:

8. Circulation
The heart functions as two pumps. One pump pushes blood to the lungs, while the other pump pushes blood to the rest of the body.

9. 1) Pulmonary Circulation
Pulmonary means lungs
Pulmonary circulation = Right side of the heart pumps oxygen-poor blood from the heart to the lungs
In the lungs, carbon dioxide diffuses from the blood, and oxygen is absorbed by the blood
Oxygen-rich blood then flows to the left side of the heart

10. 2) Systemic Circulation
Systemic means whole body
Systemic circulation = left side of the heart pumps oxygen-rich blood to the rest of the body
Cells absorb much of the oxygen and load the blood with carbon dioxide.
This now oxygen-poor blood returns to the right side of the heart for another trip to the lungs to pick up oxygen

11. Label the circulation diagram:

12. Heart Structure The heart is divided into four chambers:
Atrium (right and left side) = Each upper chamber receives blood coming into the heart
Each atrium pumps blood to the ventricle on the same side [ie: left atrium pumps to left ventricle]
Ventricle (right and left side) = Each lower chamber pumps blood out of the heart
Right ventricle pumps to the lungs and left ventricle pumps to the whole body

13. Blood Flow Through the Heart
Blood from the body enters the heart through the right atrium
Blood from the lungs enters through the left atrium.
When the atria contract, blood flows into the ventricles.

14. Atrioventricular (AV) valves = Flaps of connective tissue located between the atria and the ventricles that prevent blood from flowing backward into the atria when the ventricles contract
Tricuspid Valve = AV valve between right atrium & ventricle “if you tri (try), you’ll get it right”
Mitral Valve = AV valve between left atrium & ventricle

15. Semilunar Valves = located at the exits of each ventricle
Aortic valve = semilunar valve between left ventricle and aorta
Pulmonary valve = semilunar valve between right ventricle and pulmonary artery
This system of valves keeps blood moving through the heart in one direction.

16. Major Blood Vessels
Pulmonary Arteries = carry blood away from right ventricle to lungs
Pulmonary Veins = carry blood from lungs to left atrium
Aorta = carries blood from left ventricle to entire body
Superior & Inferior Vena Cava = carry blood from entire body to right atrium

17. Go back to page 4 and add the names of the major blood vessels:

19. On page 5, start in right atrium, identify pathway: