Heart Anatomy
What is the heart’s approximate size?
Approximately the size of a fist
Weighs less than 1 pound
What side of the heart pumps oxygen-poor blood?
Right side receives oxygen-poor blood from tissues
Pulmonary circuit: Pumps blood to lungs to get rid of CO2, pick up O2
What is the outermost layer of the heart wall?
epicardium
What is the function of heart valves?
Ensure unidirectional blood flow through heart
Open and close in response to pressure changes
What is pericarditis?
Inflammation of pericardium
Roughens membrane surfaces, causing pericardial friction rub (creaking sound) heard with
stethoscope
Where is the heart located in the thoracic cavity?
Location
In mediastinum between second rib and
fifth intercostal space
On superior surface of diaphragm
Two-thirds of heart to left of midsternal
line
Anterior to vertebral column, posterior to
sternum
Where does the right ventricle pump blood?
Right ventricle
Pumps blood through pulmonary circuit
into pulmonary arteries
What is the function of the myocardium?
circular or spiral bundles of
contractile cardiac muscle cells
Name the two atrioventricular (AV) valves.
Atrioventricular (AV) Valves
Two AV prevent backflow into atria when
ventricles contract
Tricuspid valve (right AV valve): made
up of three cusps and lies between right
atria and ventricle
Mitral valve (left AV valve, bicuspid
valve): made up of two cusps and lies
between left atria and ventricle
Attached to each AV valve are collagen
cords called chordae tendineae that are
attached to papillary muscle and prevent
valve from flowing backward
What is an incompetent valve?
Blood backflows so heart repumps same blood over and over
What are the two circuits of blood circulation?
Heart is a transport system consisting of two side-by-side pumps
Right side receives oxygen-poor blood from tissues
Pulmonary circuit: Pumps blood to lungs to get rid of CO2, pick up O2
Left side receives oxygenated blood from lungs
Systemic circuit: Pumps blood to body tissues
What vessels return oxygenated blood to the left atrium?
pulmonary veins
What is the function of the pericardial cavity?
Two layers separated by fluid-filled pericardial cavity (decreases friction)
Where are the semilunar valves located?
Two SL prevent backflow from major
arteries back into ventricles
Open and close in response to
pressure changes
Each valve consists of three cusps
that roughly resemble a half moon
Pulmonary semilunar valve:
located between right ventricle and
pulmonary trunk
Aortic semilunar valve: located
between left ventricle and aorta
What is cardiac tamponade?
Excess fluid that leaks into pericardial space
Can compress heart’s pumping ability
Treatment: fluid is drawn out of cavity (usually with syringe)
What are the heart’s four chambers?
Receiving chambers of heart
Right atrium
Receives blood returning from systemic circuit
Left atrium
Receives blood returning from pulmonary circuit
Pumping chambers of heart
Right ventricle
Pumps blood through pulmonary circuit
Left ventricle
Pumps blood through systemic circuit
What is the role of the pulmonary circuit?
Pulmonary circuit: Pumps blood to lungs to get rid of CO2, pick up O2
What are the two layers of the pericardium?
Pericardium: double-walled sac that surrounds heart; made up of two layers
1. Superficial fibrous pericardium: functions to protect, anchor heart to surrounding structures, and
prevent overfilling
2. Deep two-layered serous pericardium
Parietal layer lines internal surface of fibrous pericardium
Visceral layer (epicardium) on external surface of heart
What prevents AV valves from inverting?
Attached to each AV valve are collagen
cords called chordae tendineae that are
attached to papillary muscle and prevent
valve from flowing backward
What is valvular stenosis?
Stiff flaps that constrict opening
Heart needs to exert more force to pump blood
What structure separates the atria?
Two superior atria separated by the interatrial septum
Trace the path of blood from the right atrium to the lungs.
Right side of the heart:
• Superior vena cava
(SVC), inferior vena
cava (IVC), and
coronary sinus
• Right atrium
• Tricuspid valve
• Right ventricle
• Pulmonary semilunar
valve
• Pulmonary trunk
• Pulmonary arteries
• Lungs
Left side of the heart:
• Four pulmonary
veins
• Left atrium
• Mitral valve
• Left ventricle
• Aortic semilunar
valve
• Aorta
• Systemic
circulation
How does the cardiac skeleton help the heart?
Cardiac skeleton: crisscrossing, interlacing
layer of connective tissue
Anchors cardiac muscle fibers
Supports great vessels and valves
Limits spread of action potentials to specific paths
What is the difference between the pulmonary and aortic semilunar valves?
Atrioventricular (AV) Valves
Two AV prevent backflow into atria when
ventricles contract
Tricuspid valve (right AV valve): made
up of three cusps and lies between right
atria and ventricle
Mitral valve (left AV valve, bicuspid
valve): made up of two cusps and lies
between left atria and ventricle
Semilunar (SL) Valves
Two SL prevent backflow from major
arteries back into ventricles
Open and close in response to
pressure changes
Each valve consists of three cusps
that roughly resemble a half moon
Pulmonary semilunar valve:
located between right ventricle and
pulmonary trunk
Aortic semilunar valve: located
between left ventricle and aorta
How is a defective valve treated?
Defective valve can be replaced with mechanical, animal, or cadaver valve