The Circulatory

System

What is the circulatory system?

• The system of the body responsible for internal transport. Composed of the heart, blood vessels, lymphatic vessels, lymph, and the blood.

• The Circulatory Systems is a combination of vessels and muscle that help and control the flow of blood around the body.

• This is known as CIRCULATION.

The circulatory system has three functions:

1. Transporting substances around the body. These include oxygen, glucose, carbon dioxide, nutrients, water and waste products.

3. Protecting the body. Blood contains cells and anti-bodies that fight infection and clotting agents to stop bleeding.

2. Controlling body temperature.

• The circulation of blood moves blood to a site or sites where it can be oxygenated and wastes can be disposed of.

• Oxygenated blood is carried from the lungs to the tissues of the body and is brought back

• As oxygen and other chemicals diffuse out of the cells of the body’s tissues, waste produced in the body’s tissues diffuses into the blood to be carried away

• Blood circulates through organs such as the liver and kidneys where waste is removed and then back to the lungs to be replenished with oxygen.

body’scells

lungsDeoxygenated blood is pumped from the heart to the lungs through the pulmonary artery.

Oxygenated blood returns to the heart through the pulmonary vein.

Oxygenated blood is pumped at high pressure from the heart to the body through the aorta.

Deoxygenated blood returns to the heart through the vena cava.

• Not all animals have circulatory systems. Many tiny invertebrates have cells close enough to the external environment that gases nutrients and wastes diffuse into and out of the cells

• Animals with multiple layers of cells are too far from the external environment for diffusion to be effective. These organisms need a circulatory system to deliver gas and nutrients and to remove wastes.

Two types of Circulatory Systems:

1. Open Circulatory System• No heart or capillaries• Blood vessels act as pumps,

moving blood between open areas called sinuses

• Found in insects and mollusks

2. Closed Circulatory System• Completely enclosed system of blood in veins, arteries

and capillaries• Earthworms: have no real heart• Fish and amphibians: 2 chambered heart, 1 atrium, 1

ventricle• Reptiles: 4 chambered imperfect• Mammals and birds: 4 chambered heart

How the blood travels

• Blood from the head and arms enter the heart through the right atrium from the superior vena cava

• Blood from the body trunk and legs enters the heart from the inferior vena cava

• From the right atrium blood flows through the tricuspid valve to the right ventricle

• It then moves through the pulmonary valve and is taken to the lungs by the pulmonary artery to pick up oxygen

• After picking up oxygen the blood flows back to the left atrium of the heart via the pulmonary veins

• It moves from the left atrium through the mitral valve to the left ventricle, then through the aortic valve to the aorta

• The aorta carries oxygenated blood to all the regions of the body

http://www.youtube.com/watch?v=CWFyxn0qDEU

Blood Vessels

• Part of the closed extensive network of narrow elastic passageways which function to circulate blood to all regions of the body

There are three types of blood vessels, as shown in this magnified part of the circulatory system.

blood from the heart

blood to the heart

arterycarries blood

back intothe heart

vein

carries blood away fromthe heart

carries blood to and from the body’s cells

1. Capillaries

• Minute vessels that allow gases, nutrients and wastes to pass through their walls to and from the body cells

• Walls are semi-permeable membranes between blood and tissue fluid

• Carry blood between smallest arteries (arterioles) and smallest veins (venules)

2. Arteries

• Blood arrives at the heart muscles through two coronary arteries, supplying the muscle with oxygen

• These arteries branch immediately from the aorta, and carry oxygenated blood to the heart

• A blood clot in these arteries can lead to a fatal heart attack

Aorta: largest artery emerging from the left ventrical