The Circulatory System – The HeartSection 12.1

The Heart Contracts and relaxes rhythmically and

involuntarily without becoming tired.

Made up of cardiac muscle.

Keeps blood flowing (by pumping) In one direction only which keeps the oxygen-rich blood separate from the oxygen-poor blood.

Heart Structure Four chambers – a top and bottom each on the left

and right sides.

Atria – the top chambers will with blood returning from the body or the lungs.

Ventricles – bottom chambers receive blood from the atria and pump it out to the body or lungs.

Septum – muscular wall that separates the atria and ventricles.

The right Side of the heart Receives blood coming back from the body and

pumps it out to the lungs.

Vena cava (2 large blood vessels) open into the right atrium.

Superior Vena Cava collects oxygen-poor blood coming from tissues in the head, chest, and arms.

Inferior Vena Cava collects oxygen-poor blood from the tissues elsewhere in the body.

The right Side of the heart The oxygen-poor blood flows from the right

atrium into the right ventricle and then out into the pulmonary trunk.

It then travels to the pulmonary arteries and then to the lungs for gas exchange.

The pulmonary arteries carry blood from the heart to the lungs and are the only arteries to carry oxygen-poor blood.

The left side of the heart Receives oxygen-rich blood from the left and right lungs

and pumps it out to the body.

Pulmonary veins carry oxygen-rich blood from lungs to the left atrium. They are the only veins that carry oxygen-rich blood.

The left atrium pumps blood into the left ventricle where the blood going to the body leaves through the aorta.

The aorta is the largest vessel in the body.

Heart valves The heart has four valves inside of it to ensure the

blood flows the correct direction.

Atria and ventricles are separated by atrioventricular valves. Right side is called the tricuspid valve because it has 3

flaps. Left side is called bicuspid valve because it has 2 flaps.

Other valves are called semi-lunar valves because of their half-moon shape. They carry blood away from the heart. (pulmonary arteries and aorta)

Blood vessels Arteries

Carry blood away from the heart. Smaller-diameter arteries are called arterioles.

Veins Carry blood toward the heart. Smaller-diameter veins are called venules.

Capillaries Joins the arteries and the arterioles with venules and

veins. One cell thick and facilitate gas exchange.

Arteries Elastic walls allow arteries to expand as a wave of

blood flows through it during the contraction of the ventricles and then snap back when the ventricle relaxes.

When you measure your pulse, you’re feeling the rhythmic expansion and contraction of an artery as blood passes through it.

Veins Have thinner walls than arteries and lager inner circumference.

Veins are less elastic than arteries.

Muscle contractions keep blood flowing through veins. (not contractions of the veins)

Have one-way valves to keep blood flowing in one direction. (very important in legs because they ensure blood moves up your leg against gravity.)

The Mammalian Circulatory System Called a double-circulatory system.

Blood is pumped through one circuit between the heart and the lungs and it’s pumped through a second circuit between the heart and the rest of the body.

https://www.youtube.com/watch?v=HZ9Et5TyJXM

Pulmonary Circulation The movement of blood from the heart to the lungs

and then from the lungs back to the heart.

Lungs to heart carries waste carbon dioxide (blue)

As it passes through lungs, gas exchange occurs and carbon dioxide is replaced with oxygen.

Oxygen rich blood returns to the heart. (red)

Systemic Circulation The movement of oxygenated blood from the heart

to the tissues and organs throughout the body.

After circulating throughout the body, the blood returns to the heart carrying waste carbon dioxide from the body tissues.

The blood then re-enters pulmonary circulation.

80-90% of your blood is in systemic circulation.

Cardiac circulation

The movement of blood through the heart.

Homework #2, 7 and 10 P468 Heart diagram worksheet