The Circulatory System (Chapter 30)

The Vertebrate Heart

Unlike the heart of a fish, the human heart is a DOUBLE LOOP. That is, it goes from the heart, to the lungs, back to the heart, and then to the body. (In fish, blood goes from the heart, passes through the gills and onto the rest of the body)

Double loop circulation is more efficient, because it gives the heart and extra pump to move blood to the body

The mammalian heart has 4 chambers, so that oxygenated and deoxygenated blood is completely separated - again increasing efficience.

The hearts of amphibians and reptiles have only 3 chambers, blood mixes in the ventricle. (Though crocodiles do have a 4 chambered heart)

The heart is roughly the size of your fist in humans

The Anatomy of the Human Heart

The heart is divided into 4 chambers:

1. Right Atrium (RA)
2. Right Ventricle (RV)
3. Left Atrium (LA)
4. Left Ventricle (LV) (largest part of the muscle, pumps blood to rest of body)

 

The right side of the heart collects oxygen poor blood and pumps it to the lungs

The left side of the heart collects oxygen rich blood (from the lungs) to the rest of the body

Valves

Tricuspid valve- between right atrium and right ventricle
Bicuspid valve - between the left atrium and the left ventricle
Semilunar (Pulmonary valve) - is at the exit of the Right Ventricle to pulmonary artery
Semilunar (Aortic valve) - is at the exit of the Left Ventricle to the Aorta

Contractions

Systole - ventricle contracts, pumping blood to the lungs and to the body

Diastole - atrium contracts, pumping blood to the ventricle

Flow of Blood (see figure 30.5)

Blood from the body flows:

1. to the Superior and Inferior Vena Cava,
2. then to the Right Atrium
3. through the Tricuspid Valve
4. to the Right Ventricle
5. through the Pulmonic Valve
6. to the Pulmonary Artery
7. to the Lungs

The blood picks up oxygen in the lungs, and then flows from the lungs:

1. to the Pulmonary Veins
2. to the Left Atrium
3. through Mitral valve
4. to the Left Ventricle
5. through the Aortic Valve
6. to the Aorta
7. to the body

Major Vessels

Aorta - pumps blood to the body (it connects to the left ventricle)
Pulmonary artery - connects to right ventricle, pumps oxygen-poor blood to the lungs
Pulmonary veins - bring oxygen rich blood from the lungs to the left atrium
Superior Vena Cava - brings oxygen poor blood from the upper body to the right atrium
Inferior Vena Cava - brings oxygen poor blood from the lower part of the body to the right atrium
Coronary Arteries - located on the outside of the heart, these vessels supply blood to the heart itself, a blockage in these arteries can lead to a heart attack.

Other Resources

If you want some good graphics and explanations of the heart, check out http://www.howstuffworks.com/heart.htm - HIGHLY RECOMMENDED!Heart

Animations

http://medlib.med.utah.edu/kw/pharm/hyper_heart1.html
http://www.medtropolis.com/VBody.asp

Try the Practice Quiz on the Heart

 

What about Blood?

Blood is a mixture of cells and plasma. Its job is to supply the body with oxygen and nutrients and to carry away waste.

Blood cells

Red Blood Cells carry oxygen from the lungs
White blood cells help fight infection
Platelets are used for clotting

Plasma

The liquid portion of the blood, contains nutrients and vitamins, hormones, and proteins.

*The human body contains approximately 5 liters of blood

Mini-Review Questions:

1. Trace the blood flow in the human heart.
2. Name the vessels that leave the heart
3. Why is the human heart called a "double loop"
4. What are the two components of blood?
5. Name the valves of the heart and describe their location.
6. Compare systole to diastole.