Chaptser 18 Flashcards
pulmonary circuit
-The right side receives oxygen-poor blood from
tissues
§ Pumps blood to lungs to get rid of CO2,
pick up O2,
systemic circuit
-The left side receives oxygenated blood from
lungs
Right atrium
§ Receives blood returning from systemic circuit
Left atrium
§ Receives blood returning from pulmonary circuit
Right ventricle
§ Pumps blood through pulmonary circuit
Left ventricle
§ Pumps blood through systemic circuit
Location of heart
– 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
Pericardium
the double-walled sac that surrounds the heart; made up of two layers
Superficial fibrous pericardium:
functions to protect, and anchor heart to surrounding structures, and prevent overfilling
Superficial fibrous pericardium:
functions to protect, and anchor heart to surrounding structures, and prevent overfilling
Parietal layer
lines internal surface of fibrous pericardium
Visceral layer (epicardium)
on external surface of heart
pericardial cavity (decreases friction)
Two layers separated by fluid-filled
Three layers of heart wall
-Epicardium: a visceral layer of serous pericardium
– Myocardium: circular or spiral bundles of contractile cardiac muscle cells
§ Cardiac skeleton: crisscrossing, interlacing layer of connective
tissue
– Endocardium: innermost layer; is continuous with endothelial lining of blood vessels
Atria
the receiving chambers
– Small, thin-walled chambers; contribute little to propulsion of blood
Right atrium
receives deoxygenated blood from body
§ Anterior portion is smooth-walled
§ Three veins empty into right atrium:
– Superior vena cava: returns blood from body regions above the
diaphragm
– Inferior vena cava: returns blood from body regions below the
diaphragm
– Coronary sinus: returns blood from coronary veins
Left atrium
eceives oxygenated blood from lungs
§ Four pulmonary veins return blood from lung
Ventricles
the discharging chambers
– Make up most of the volume of heart
– Trabeculae carneae: irregular ridges of muscle on ventricular walls
– Papillary muscles: project into ventricular cavity
§ Anchor chordae tendineae that are attached to heart valves
– Thicker walls than atria
– Actual pumps of heart
Heart Valves
- Ensure unidirectional blood flow
through heart - Open and close in response to
pressure changes
- Two major types of valves
– Atrioventricular valves located
between atria and ventricles
– Semilunar valves located
between ventricles and major
arteries
trioventricular (AV) valves
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
– Chordae tendineae: anchor cusps of AV valves to papillary muscles that function
to:
§ Hold valve flaps in closed position
§ Prevent flaps from everting back into atria
semilunar (SL) valves
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
Incompetent valve
Blood backflows so heart repumps same blood over and over
Valvular stenosis
§ Stiff flaps that constrict opening
§ Heart needs to exert more force to pump blood
