The Circulatory System

• The circulatory system is the body's transport system
• Its main function is to deliver water, nutrients, hormones, and oxygen to cells
• It picks up waste materials and carbon dioxide from cells

Components of the Circulatory System

• Heart
• Blood
• Blood vessels

Types of Blood Carried

• Oxygenated blood
• Deoxygenated blood

Oxygenated Blood

• Oxygen-rich
• Travels to the body cells
• Has a high oxygen content
• Has a low carbon dioxide content

Deoxygenated Blood

• Oxygen-poor
• Travels away from the body cells
• Has a low oxygen content
• Has a high carbon dioxide content

Blood

• Blood is composed of tissue cells and plasma
• It consists of 80% water and 20% solids

Red Blood Cells

• Also called erythrocytes
• Shaped like disks with two concave surfaces
• Thinner at the middle than at the edges
• Carries oxygen to the cells
• Smaller than white blood cells, but bigger than platelets
• Removes carbon dioxide from the body so one can breath
• Made in the bone marrow
• Typically live for about 120 days, then die

White Blood Cells

• Also called leukocytes
• About 1% of blood
• Protects against illness and disease
• Fights infection and prevents cancer cells from growing
• Produced in the bone marrow
• The number increases when fighting infection
• Immunity cells that are always at war
• Flows through the bloodstream to fight viruses, bacteria, and other foreign invaders
• Rushes to help destroy any harmful substance and prevent illness

Platelets

• Tiny blood cells that help the body form clots to stop bleeding
• Sends out signals to the platelets when blood vessels are damaged
• The platelets then rush to the site of damage and form a plug (clot) to fix the damage
• Fibrin forms a network that traps red blood cells to help the blood to clot and stop bleeding when a person is wounded
• Fibrinogen is a protein that sticks platelet together to form a strong tight seal
• Scabs form when the clot dries

Blood Plasma

• Plasma is a light yellow liquid
• Carries water, salts, enzymes, and waste products
• Plasma makes up about 55 percent of blood
• Carries out several key functions in the body, including transporting
• Plasma contains about 92 percent water, to fill up blood vessels, keeping blood and other nutrients moving through the heart
• Fibrinogen helps in clotting
• Albumin maintains a balance of fluid in the blood
• Globulins help fight various diseases

Blood Vessels

• Blood vessels are networks of tubes where the blood moves inside the body
• They are like water pipes that carry water to different places

Three Major Blood Vessels

• Arteries
• Veins
• Capillaries

Arteries

• Have thick muscle walls
• Expands every time the ventricles contract to withstand the full force of blood coming from the heart
• Carries oxygen-rich blood
• Carries blood away from the heart to various organs of the body
• Arterioles are small blood vessels, but larger than capillaries
• Arterioles connect arteries with capillaries

Veins

• Have thin muscle walls
• One-way valve that prevents blood from flowing backward
• Carries oxygen-poor blood
• Collect blood from different organs and bring it back to the heart
• Venule is the smallest vein
• Vena cava is the largest vein

Capillaries

• Tiny blood vessels
• Connects arteries to the veins
• Oxygen and nutrients pass from the arteries
• Carbon dioxide and body waste pass from the cells to the veins to the capillaries
• Exchange of material between the blood and surrounding cells takes place across the thin walls

Heart

• The organ at the center of the circulatory system
• A muscular organ also called cardiac muscle
• It is about the size of a fist
• Located just behind and slightly left of the breastbone
• Roughly the size of a large fist
• Weighs between about 10 to 12 ounces (280 to 340 grams) in men
• Weighs about 8 to 10 ounces (230 to 280 grams) in women
• Beats about 60 to 100 times per minute
• Sends blood throughout the body, carrying oxygen to every cell with each heartbeat
• Delivers oxygen, the blood returns to the heart
• Sends blood to the lungs to pick up more oxygen
• This cycle repeats over and over again

Four Chambers of the Heart

• Right Atrium receives deoxygenated blood from the body
• Left Atrium receives oxygenated blood from the lungs
• Right Ventricle pumps blood to the lungs for oxygen
• Left Ventricle pumps blood to all body parts

Septum

• The dividing wall between the right and left sides of the heart
• The word "septum" is borrowed from the Latin "saeptum" meaning a "dividing wall or enclosure"

Valves

• Tricuspid Valve separates right atrium from right ventricle
• Bicuspid Valve separates left atrium from left ventricle
• Pulmonary Valve is the valve between the right ventricle and the opening of the pulmonary vein
• Aortic Valve is the valve between the left ventricle and the aorta

Blood Circulation

• The systemic circulation provides organs, tissues, and cells with blood so that they get oxygen and other vital substances
• The pulmonary circulation is where the fresh oxygen we breathe in enters the blood