ch. 19: circulatory system THE HEART Flashcards
overview of the cardiovascular system
cardiology
study of the heart and its disorders
overview of the cardiovascular system
cardiovascular system
consists of heart and blood vessels
overview of the cardiovascular system
heart is a pump that keeps blood
flowing through the vessels
overview of the cardiovascular system
vessels deliver blood to
body tissues and returns it to the heart
overview of the cardiovascular system
arteries
all vessels that carry blood AWAY from heart
overview of the cardiovascular system
veins
all vessels that carry blood TOWARD heart
overview of the cardiovascular system
capillaries
microscopic vessels that connect the smallest arteries to the smallest vessels
overview of the cardiovascular system
circulatory system
refers to heart
vessels blood
pulmonary and systemic circuits
pulmonary circuit
carries blood to lungs for gas exchange and back to heart
pulmonary and systemic circuits
systemic circuit
supplies oxygenated blood to all tissues of the body and returns it to the heart
pulmonary and systemic circuits
cardiovascular system has 2 major divisions
pulmonary and systemic circuits
pulmonary and systemic circuits
right side of heart supplies the pulmonary circuit
- oxyen POOR blood arrives from body tissues
blood sent to
alveoli of lungs
via pulmonary trunk and pulmonary arteries
picks up oxygen
returns to heart via pulmonary veins
pulmonary and systemic circuits
left side of heart supplies systemic circuit
- fully oxygenated blood sent to body tissues via aorta which branches into smaller vessels
- blood releases oxygen at the tissues; deoxygenated blood returns to heart via superior vena cava and inferior cava
the major arteries and veins entering and leaving the heart are called the
great vessels
position, size, and shape of the heart
heart located in mediastinum
space between lungs
position, size, and shape of the heart
base
wide
superior portion of heart
large vessels attach here
position, size, and shape of the heart
apex
tapered inferior end
tilts to the left
position, size, and shape of the heart
size of heart in adult
weighs 10 oz
3.5 in wide at base
5 in from base to apex
at any age heart is size of fist
pericardium
heart enclosed by
pericardium
a double walled sac
pericardium
allows heart to beat without
friction
provides room to expand
yet resists excessive expansion
pericardium
anchored to diaphragm
inferiorly and sternum anteriorly
structure of pericardium
fibrous pericardium
outermost layer
tough, fibrous sac
structure of pericardium
serous pericardium
parietal layer : lines fibrous pericardium
visceral layer : (epicardium) adheres to heart surface and outermost layer of heart itself
structure of pericardium
pericardial layer
- space between parietal and visceral layers of serous pericardium
- filled with 5 to 30 mL of pericardial fluid
structure of pericardium
pericarditis
inflammation of the pericardium
may result in friction rub
the heart wall
the heart wall has 3 layers
- epicardium
- myocardium
- endocardium
the heart wall
epicardium
- visceral layer of serous pericardium
- serous membrane covering heart
- adipose in thick layer in some places
- coronary blood vessels travel through this layer
the heart wall
endocardium
- smooth inner lining of heart and blood vessels
- covers the valve surfaces and is continous with endothelium of blood vessels
the heart wall
myocardium
- layer of cardiac muscle, thickness is proportional to workload
- muscle spirals around heart called the vortex of the heart arrangement produces wringing motion during contraction
the heart wall
fibrous skeleton
- framework of collagenous and elastic fibers
- provides structural support & attachment for cardiac muscle and anchor for valve tissue (fibrous rings)
- electrical insulation between atria and ventricles; important in timing and coordination of contractile activity
the chambers
the heart has 4 chambers
2 atria
2 ventricles
the chambers
right and left atria
- 2 superior chambers that receive blood returning to the heart; seperated from each other by interventricular septum
- each has an associated auricle– an earlike flap that increases the chamber volume
- right atrium and both auricles contains pectinate muscles–internal ridges of myocardium
- thin, flaccid walls; pump blood to the ventricles
the chambers
right and left ventricles
- 2 inferior chambers that eject blood into the arteries; seperated from each other by interventricular septum
- left ventricle wall is 2-4X thicker than right ventricle, which reflects its greater workload in pumping blood to the entire body (vs to the lungs)
- both ventricles contain trabecular carnae– internal muscular ridges; help chambers expand and refill more easily
chambers of the heart
external features
- boundaries marked by sulci (grooves) filled with fat and coronary vessels
- cornonary sulcus– seperates atria above from ventricles below; encircles heart near base
- anterior and posterior interventricular sulci–seperate left and right ventricles; overlie the interventricular septum and extend obliquely down heart, from base to apex
valves
vale ensure one-way flow of blood through
heart
valves
each valve has 2 or 3 fibrous flaps
cusps or leaflets
valves
atrioventricular (AV) valves
control blood flow between atria and ventricles
atriventricular valve
right AV (tricuspid) valve
usually has 3 cusps
atriventricular valve
left AV valve (mitral valve)
usually has 2 cusps
atriventricular valve
tendinoud cords
(chordae tendineae)
strings of connective tissue that attach valve cusps to papillary muscles on floor of ventricle
* prevent AV valves from flipping or bulging into atria when ventricles contract
heart valves
semilunar valves
conrol flow from ventricles into great arteries
semilunar valves
pulmonary valve
controls the opening between right ventricle and pulmonary trunk
semilunar valves
aortic valve
controls the opening between left ventricle and aorta
semilunar valves
each has 3 cusps shaped like shirt pockets
- during ventricular contraction and blood ejection, cusps pressed up against arterial walls
- when ventricules relax blood flows back toward ventricles and fills cusps causing valves to close
Blood Flow Through the Chambers
Pathway of blood from right atrium, through body, and back to the starting point
- Blood enters right atrium from superior and inferior venae cavae.
- Blood in right atrium flows through right AV valve into right ventricle.
- Contraction of right ventricle forces pulmonary valve open.
- Blood flows through pulmonary valve into pulmonary trunk
- Blood is distributed by right and left pulmonary arteries to the lungs,
where it unloads carbon dioxide and loads oxygen. - Blood returns from lungs via pulmonary veins to left atrium.
- Blood in left atrium flows through left AV valve into left ventricle.
- Contraction of left ventricle (simultaneous with step 3) forces aortic
valve open. - Blood flows through aortic valve into ascending aorta.
- Blood in aorta is distributed to every organ in the body, where it
unloads oxygen and loads carbon dioxide. - Blood returns to right atrium via venae cavae.
The Coronary Circulation
Heart has its own supply of vessels to deliver blood to
myocardium
coronary circulation
19.2e The Coronary Circulation
Left coronary artery (LCA)
branches off ascending aorta
Left coronary artery (LCA)
Anterior interventricular branch
[left anterior descending (LAD)
branch]
* Supplies blood to both ventricles and anterior two-thirds of the
interventricular septum
Left coronary artery (LCA)
Circumflex branch
- Passes around left side of heart in coronary sulcus
- Gives off left marginal branch and then ends on the posterior side of
the heart - Supplies left atrium and posterior wall of left ventricle
Right coronary artery (RCA)
Right marginal branch
Supplies lateral aspect of right atrium and ventricle
Right coronary artery (RCA)
Posterior interventricular branch
Supplies blood to posterior walls of both ventricles and interventricular
septum
The Coronary Circulation
Flow through coronary arteries is greatest when heart
relaxes
- During ventricular contraction: coronary arteries compressed, open
aortic valve blocks blood flow into them - During ventricular relaxation: blood in the aorta surges back toward
the heart and into the openings of the coronary arteries
Angina and Heart Attack
Angina pectoris
chest pain from partial obstruction of coronary
blood flow
* Pain caused by ischemia of cardiac muscle
* Obstruction partially blocks blood flow; myocardium shifts to
anaerobic fermentation, producing lactate and thus stimulating
pain
Angina and Heart Attack
Myocardial infarction (MI)
sudden death of a patch of
myocardium resulting from long-term obstruction of coronary
circulation
* Atheroma (blood clot or fatty deposit) often obstructs coronary
arteries; cardiac muscle downstream of the blockage dies
* Heavy pressure or squeezing pain radiating into the left arm
* Some painless heart attacks may disrupt electrical conduction
pathways, leading to fibrillation and cardiac arrest
Venous drainage
Venous drainage
route by which blood leaves an organ
* 5% to 10% of coronary blood drains directly into heart
chambers (mostly right ventricle) by way of the small
cardiac veins;
Venous drainage
most coronary blood returns to right atrium
by:
- The great cardiac vein—blood from anterior aspect of heart
- Posterior interventricular (middle cardiac) vein—blood from
posterior aspect of heart - Left marginal vein—travels from apex up left margin of heart
- Coronary sinus—transverse vein in coronary sulcus on posterior
heart; receives blood from veins listed above, empties into right
atrium
Cardiac Muscle and the Cardia Conduction System
Heartbeat is myogenic
signal originates in the heart itself
Structure of intercalated discs:
Mechanical junctions:
Interdigitating folds
Electrical junctions
Structure of intercalated discs:
Mechanical junctions:
- Fascia adherens—broad band in which the actin of the thin
myofilaments is anchored to the plasma membrane; cells linked by
transmembrane proteins - Desmosomes—mechanical linkages that prevent contracting
cardiomyocytes from being pulled apart from each other
19.3b Metabolism of Cardiac Muscle
Cardiac muscle depends almost exclusively on aerobic
respiration to make ATP
- Rich in myoglobin and glycogen
- Huge mitochondria: fill 25% of cell
- Fatigue resistant because it makes little use of anaerobic
fermentation or oxygen debt mechanisms; does not
fatigue for a lifetime
19.3b Metabolism of Cardiac Muscle
Cardiac muscle is adaptable to different organic fuels
- Fatty acids (60%); glucose (35%); ketones, lactate, and
amino acids (5%) - More vulnerable to oxygen deficiency than lack of a
specific fuel
19.3c The Conduction System
cardiac conduction system
coordinates the heartbeat;
consists of an internal pacemaker and nerve-like conduction
pathways through myocardium
Electrical and Contractile Activity of the Heart
The heart cycles through contraction and relaxation
- Contraction is called systole
- Relaxation is called diastole
- These terms can refer to contraction and relaxation of
either type of chamber, they usually refer to the action of
the ventricles
