Introduction to the Heart and Circulatory System

Have a Heart!

Secretariat

How Big is the Heart?• A human heart is about 10.5 ounces• The average Thoroughbred horse heart weighs 9

pounds– Secretariat: Could finish the quarter mile race

at speeds of 49 MPH(Man O War only maxed out at about 40 MPH)

– Upon autopsy found that his heart weighed about 22 pounds!• Found to be a genetic factor carried on the X

chromosome of the mare• Not a mutation because the heart was in

correct proportion

Functions of the Circulatory System

• Transports oxygen, nutrients, and other essential compounds to all cells.

• Transports CO2 and other wastes away from cells for elimination from the body.

• Helps maintain Homeostasis of body cells.

Three Main Parts

• Heart• Blood Vessels• Blood

Heart• The Main Pump• The heart is divided into 4 chambers

that are connected by valves– Valves are flap-like structures that allow

blood to only flow in one direction– The audible sounds heard in the heart (Lub-

dub) are actually the valves closing• When a valve is not working properly the

sound will be different creating a “Murmer”

The Chambers of the Heart• There are 4 chambers divided into

“upper” and “lower” chambers• There are two hemispheres of the heart;

the right and left side, divided by the septum

Atria– Upper Chambers of the Heart– Right Atrium:

•Receives blood from the vena cava as it returns to the heart

– Left Atrium:•Receives blood returning to the heart from the pulmonary veins

Ventricles• The lower chambers of the heart• Right Ventricle:

•Receives blood from the right atrium and pumps it to the pulmonary artery

• Left Ventricle:•Receives blood from the left atrium

and pumps it to the aorta

The Heart

The Heart Diagram

• Using your heart diagram, fill in the missing answers

Blood Flow through the Heart

• De-oxygenated blood flows from the vena cava into the right atrium

• The right atrium empties its contents into the right ventricle

Blood Flow Continued

• De-oxygenated blood is pumped into the pulmonary artery

• The pulmonary artery carries blood to the lungs where it picks up oxygen

• The blood is returned to the left atrium by the pulmonary vein

Flow of blood through the heart!

Un-oxygenated blood enters through the vena cava right atrium through the tricuspid valve into the right ventricle through the pulmonary artery (away) to the lungs to get oxygen back through the pulmonary vein into the left atrium through the mitral valve into the left ventricle out the aorta

Pericardium

• Pericardial Membranes– Fibrous

• Outer fibrous sac– Parietal

• Lies between visceral and fibrous

– Visceral• Outer layer of

the wall of the heart

• Fluid filled sac around the heart

• Function– Keeps the heart

in the chest cavity

– Prevents the heart from over expanding

– Limits heart motion

Heart Wall

• Epicardium– Outer layer of the wall of the heart– Provides protection

• Myocardium– Muscular middle layer of the heart– Stimulates heart contractions to pump blood

from the ventricles and relaxes to allow the atria to receive blood

• Endocardium– Inner layer of the heart– Participates in the contraction of the heart

Heart Health

• Oh My! Maybe I should lay off of the corn!

• Because swine and humans are so compatible, heart valves are commonly used from pigs to repair those in humans!

Are you Ready Doctor?

• http://www.pbs.org/wgbh/nova/eheart/transplantwave.html