1. The circulatory system

2. Evolution of the heart.
In insects there is a 2 chambered heart. It is a very simple heart design shared by fish and some birds.

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

4. The vertebrate heart The mammalian heart has 4 chambers, so that
oxygenated and
deoxygenated blood is
completely separated –
again increasing efficiency.

5. 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 heart is roughly the size of your fist in humans

6. 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)

7. 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

8. 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

9. Contractions
Systole - ventricle contracts, pumping blood to the lungs and to the body
Diastole - atrium contracts, pumping blood to the ventricle

10. Flow of Blood 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

11. 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

12. 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.

13. Electrical System
Have you ever wondered what makes your heart beat? How does it do it automatically, every second of every minute of every hour of every day?

14. The natural pacemaker of the heart is called the sinoatrial node (SA node). It is located in the right atrium. The heart also contains specialized fibers that conduct the electrical impulse from the pacemaker (SA node) to the rest of the heart

15. The electrical impulse leaves the SA node (1) and travels to the right and left atria, causing them to contract together. This takes .04 seconds. There is now a natural delay to allow the atria to contract and the ventricles to fill up with blood. The electrical impulse has now traveled to the atrioventricular node (AV node) (2). The electrical impulse now goes to the Bundle of His (3), then it divides into the right and left bundle branches (4) where it rapidly spreads using Purkinje fibers (5) to the muscles of the right and left ventricle, causing them to contract at the same time.

16. 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