Heart• Objectives• Describe the location and surface anatomic features of the heart• Compare and contrast the two major

circulatory systems in the human body• Diagram, without reference to your notes or

book, the path of blood flow through the heart and lungs

• Identify the major blood vessels, chambers and valves of the heart

Systemic Circulation• –Carries oxygenated blood from the aorta to the

tissues• the left ventricle ejects blood into the aorta• The blood is distributed to 6 major• organ systems: brain, heart, kidneys,• muscle, GI system, and skin

• The circulatory system is often described

as a “tree”• – Blood vessels are arranged in parallel

The Pulmonary Circulation

• the pulmonary circulation carries deoxygenated blood (venous blood) to the lungs and then back to the heart• the right ventricle ejects blood into the pulmonary circulation• blood leaving the pulmonary circuit• (arterial blood) enters the left atrium

Summary

• Pulmonary circulation:• Path of blood from right ventricle through the

lungs and back to the heart.• Systemic circulation:• Oxygen-rich blood pumped to all organ

systems to supply nutrients.• Rate of blood flow through systemic

circulation = flow rate through pulmonary circulation.

Systemic and pulmonary circulation

The Cardiac Output

• the amount of blood pumped by the ventricles per unit time

• under resting conditions, the left and right ventricles each pump about 5 liters of blood per minute

• this value can be increased to as much as 30 liters per minute during maximal exercise

Superficial Anatomy of the Heart

• the heart is located behind the sternum, above the diaphragm

• 2/3 of the mass lies left of midline, and the apex points down and to the left.

• the heart is about 5 inches long, 3.5 inches wide and 2.5 inches thick

• the great vessels that emerge from the heart include the pulmonary arteries and veins, the aorta, and the superior and inferior vena cava.

Chambers of the Heart

• The mammalian heart is composed of four chambers

• – the right atrium• – the left atrium• – the right ventricle• – the left ventricle• • the left ventricle has much more muscle and is much thicker than the right ventricle

Note: wall of left ventricle is thicker than right ventricle

Heart Valves

• the heart has four “one-way” valves• The valves insure that the blood flows in one direction, from heart to tissues and back to the

heart• two atrioventricular valves (between atria and ventricles)• two semilunar valves (between LV and aorta and between RV and pulmonary trunk)

Atrioventricular Valves

• the left AV valve is also called the bicuspid or mitral valve, and separates the left atrium and left ventricle

• the right AV valve is also called the tricuspid valve, and separates the right atrium and right ventricle

Semilunar Valves

• The aortic semilunar valve separates the left ventricular chamber from the aorta.

• the pulmonary semilunar valve separates the right ventricular chamber from the main

pulmonary trunk.

• these valves are pressure dependent, meaning that they open and close in response to pressure differences in the vessels and ventricular chambers.

Pressure-dependent ValveFunction

• Aortic Pressure = 90 mmHg

• Ventricular Pressure = 85 mmHg; valves closed and blood is not ejected

• Aortic Pressure = 100 mmHg

• Ventricular Pressure = 101 mmHg; valves open and blood is ejected

Blood Supply to Heart Muscle• the tissues of the heart are supplied with blood

from the right and left coronary arteries

• the right coronary artery originates on

the ascending aorta

• the left coronary artery also originates

on the ascending aorta