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a and p 2 chapter 20


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how much does the heart pump per year?
over 1 million gallons
how many miles of blood vessels are there?
over 60,000
where is the heart located?
area from the sternum to the vertebral column and between the lungs
directed anteriorly, inferiorly and to the left
directed posteriorly, superiorly and to the right
anterior surface
deep to the sternum and ribs
inferior surface
rests on the diaphragm
right border
faces right lung
left border
(pulmonary border)
faces left lung
what is located under the diagphragm?
stomach and esophagus
what are the hearts surfaces and borders?
surfaces anterior/inferior
borders right/left
fibrous pericardium
dense irregular ct
protects and anchors the heart prevents overstretching
serous pericardium
thin delicate membrane
what does the serous pericardium contain?
parietal layer-outer layer
pericardial cavity with pericardial fluid
visceral layer (epicardium)
visceral layer of serous pericardium
cardiac muscle layer is the bulk of the heart
chamber lining and valves
muscle bundels of the myocardium
cardiac muscle fibers swirl diagonally around the heart in interlacing bundles
what are the chambers of the heart?
2 upper atria
2 lower ventricles
sulci of the heart
grooves on the surface of the heart containing coronary blood vessels and fat
coronary sulcus
anterior interventricular sulcus
posterior interventricular sulcus
coronary sulcus (sinus)
most important
encircles heart and marks the boundary between the atria and ventricles
anterior interventricular sulcus
marks the boundary between the ventricules anteriorly
posterior interventricular sulcus
marks the boundary between the ventricles posteriorly
pulminary arteries have what type of blood?
pulminary arteries are the only artery that is
right atrium
receives blood from 3 sources
interatrial septum partitions the atria
fossa ovalis
tricuspid valve
fossa ovalis
a reminant of the fetal foramen ovale
right atrium tricuspid valve
blood flows through into right ventricle
has 3 cusps composed of dense ct covered by endocardium (epithelial tissue)
the right ventricle forms most of
anterior surface of the heart
right ventricle
papillary muscles
chordae tendineae
interventricular septum
pulmonary semilunar valve
papilary muscles
are coned shaped trabeculae carneae ( raised bundles of cardiac muscles)
chordae tendineae
chords between valve cusps and papillary muscles
interventricular septum
partitions ventricles ( stops tricuspid valve from opening up)
pulmonary semilunar valve
blood flows into pulmonary trunk
left atrium forms most of
the base of the heart
left atrium
receive blood from lungs
bicuspid (mitrol) valve
left atrium receives blood from lungs
4 pulmonary veins (2 right and 2 left)
bicuspid valve
(mitral valve)
blood passes through into left ventricle
has 2 cusps
left atrioventricular, mitral, or bicuspid valve (lamb)
left ventricle forms
the apex of the heart
left ventricle
chordae tendinae anchor bicuspid valve to papillary muscles (also has trabeculae carneae like right ventricle)
-aortic semilunar valve
aortic semilunar valve
-blood passes through valve into the ascending aorta
-just above the valve are the openings to the coronary arteries
myocardial thickness and function
thickness of myocardium varies according to the function of the chamber
atria are
thin walled, deliver blood to adjacent ventricles
ventricle walls
are much thicker and stronger than the atria walls
-right ventricle supplies blood to the lungs (little flow resistance)
-left ventricle wall is the thickest to supply systemic circulation
what wall is the thickess of the cardiac walls?
myocardium of left ventricle is much thicker than the right
fibrous skeleton of heart
dense ct rings surround the valves of the heart, fuse and merge with the interventricular septum
-support structure for heart valves
-insertion point for cardiac muscle bundles
-electrical insulator between atria and ventricles
electrical insulator between atria and ventricles
prevents direct propagation of ap's (action potentials) to ventricles
atrioventricular valves open
a-v valves open and allow blood to flow from atria into ventricles when ventricular pressure is lower than atrial pressure
-occurs when ventricles are relaxed, chordae tendineae are slack and papillary muscles are relaxed
atrioventricular valves close
a-v valves close preventing backflow of blood ino atria
-occurs when ventricles contract, pushing valve cusps closed, chordae tendinae are pulled taunt and papillary muscles contract to pull cords and prevent cusps from everting
semilunar valves
-sl valves open with ventricular contraction
-sl valves close with ventricular relaxation
sl valves open with ventricular contraction
allow blood to flow into pulmonary trunk and aorta
sl valves close with ventricular relaxation
prevents blood from returning to ventricles, blood fills valve cusps, tightly closing the sl valves
function of atria
atria contract, blood fills ventricles through a-v valves
function of ventricles
ventricles contract, blood pumped into aorta and pulmonary trunk through sl valves
blood circulation
2 closed circuits, the systemic and pulmonic(systemic circulation and pulmonary circulation)
systemic circulation
-left side of heart pumps blood through body
-left ventricle pumps oxygenated blood into aorta
-aorta branches into many arteries that travel to organs
-arteries branch into many arterioles in tissue
-arterioles branch into thin walled capillaries for exchange of gases and nutrients
-deoxygenated blood begins its return in venules
-venules merge into veins and return to right atrium
pulmonary circulation
-right side of heart pumps deoxygenated blood to lungs
-right ventricle pumps blood to pulmonary trunk
-pulmonary trunk branches into pulmonary arteries
-pulmonary arteries carry blood to lungs for exchange of gases
-oxygenated blood returns to heart in pulmonary veins
blood flow colors
coronary circulation
blood supply to the heart
-heart as a very active muscle needs lots of o2
-when the heart relaxes high pressure of blood in aorta pushes blood into coronary vessels
-many anastomoses
connections between arteries supplying blood to the same region, provide alternate routes if one artery becomes occluded
coronary arteries
branches off aorta above aortic semilunar valve
-left coronary artery
-right coronary artery
coronary veins
-collect wastes from cardiac muscle
-drains into a large sinus on posterior surface of heart (coronary sinus)
-coronary sinus empties into right atrium
where does the coronary sinus empty into?
right atrium
cardiac muscle histology
branching intercalated discs with gap junctions, involuntary, striated, single central nucleus per cell
conduction system of heart
coordinates contraction of heart muscle
-autorhythmic cells
-sa node
-av node
-av bundle of His
autorythmic cells
cells fire spontaneously, act as a pacemaker and form conduction system for the heart
sa node
-cluster of cells in wall of rt. atria
-begins heart activity that spreads to both atria
-exicitation spreads to av node
av node
in atrial septum, transmits signal to bundle of His
av bundle of His
the conection between atria and ventricles
divides into bundles branches and purkinje fibers, large diameter fibers that conduct signals quickly
rythm of conduction system
-sa node fires spontaneously 90-100 times per minute
-av node fires at 40-50 times per minute
-if both nodes are suppresed fibers in ventricles by themselves fire 20-40 times per minute
rythm of cs
-artificial pacemaker is needed if pace is to slow
-extra beats are forming at other sites are called ectopic pacemakers(increased by cafeine and nicotine)
-cardiac cell resting membrane potential is-90mv
-excitation spreads through gap junctions
-fast na channels open for rapid depolarization
plateau phase
-250 msec (only 1msec in neuron)
-slow ca2 channels open, let ca2 enter from outside cell and from storage in sarcoplasmic reticulum, while k channels close
-ca2 binds to troponin to allow for actin-myosin cross-bridge formation and tension development
-ca2 channels close and k channels open and -90mv is restored as potassium leaves the cell
refratory period
very long so heart can fill
one cardiac cycle
what happens to the heart in one beat at 75 beats/min, one cycle requires 0.8 sec.
-end diastolic volume (edv)
-end systolic volume (esv)
-stroke volume (sv)
at 75 beats/min, one cycle requires 0.8 sec.
systole and diastole of both atria, plus the systole and diastole of both ventricles
volume in ventricle at end of diastole, about 130ml
volume in ventricle at end of systole, about 60ml
-the volume ejected per beat from each ventricle, about 70ml
isovolumetric relaxation
all relaxing at the same time(closed)
atriums filing up(coronary sinus)
ventricular filing
- rapid ventricular filing as blood flows from full atria
-diastasis:as blood flows from atria in smaller volume
-atrial systole pushes final 20-25 ml blood into ventricle
atrial ventricular valves open
ventricular systole
-isovolumetric contraction: brief period, av valves close before sl valves open
-ventricular ejection:as sl valves open and blood is ejected to ventricule
bp in aorta
120mm hg
bp in pulmonary trunk
30mm hg
differences in ventricle wall thickness allows
heart to push the same amount of blood with more force from the left ventricle
the volume of blood ejected from each ventricle is
70ml (stroke volume)
sound of the heart beat are from
turbulence in blood flow caused by valve closure
what are the 2 sounds of the heart?
is created with the closing of the atrioventricular valves
is created with the closing of semilunar valves
cardiac output
amount of blood pushed into aorta or pulmonary trunk by ventricle
determined by stroke volume and heart rate
cardiac reserve
maximum output/output at rest
influences on stroke volume
preload (affect of stretching)
frank-starling law of heart
-more muscle is stretched, greater force of contraction
-more blood more force of contraction results
autonomic nerves, hormones, ca+2 or k+ levels
-amount of pressure the heart has to overcome
-high blood pressure creates high afterload
regulation of heart rate
-nervous control from the cardiovascular center in the medulla
-heart rate is also affected by hormones
nervous control from the cardiovascular center in the medulla
-sympathetic impulses increase heart rate and force of contraction
-parasympathetic impulses decrease heart rate
baroceptors (pressure receptors) detect change in bp and send info to the cardiovascular center(located in the arch of the aorta and carotid arteries)
what hormones affect heart rate?
-epinephrine, norepinephrine, thyroid hormones
-ions (na+, k+, ca2+)
-age, gender, phsical fitness, and temp.
factors in heart disease
diabetes mellitus
genetic predisposition
male gender
high blood levels of fibrinogen
left ventricular hypertrophy
what should the total cholesterol be for an adult?
under 200 mg/dl

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