The proper function of the cardiovascular system depends on:
-the activity of the heart
-heart can vary its pumping capacity depending on the needs of the peripheral tissues.
The cardiovascular system can be subdivided into two closed circuits that occur in series..
-Pulmonary circuit
-Systemic circuit
Pulmonary circuit
carries oxygen-poor blood from the heart to the lungs and back.
Systemic circuit
transports oxygen-rich blood from the heart to the rest of the body and back.
Arteries
Blood vessels that carry blood AWAY from the heart.
Veins
blood vessels that carry blood BACK to the heart.
capillaries
-the smallest blood vessels which connect the smallest arteries with the smallest veins. -Nourishment and fluid noramlly trapped in thick walled arteries and veins can easily pass through the delicate walls of the capillaries
The heart contains four chambers
-Right atrium and ventricle
-Left atrium and ventricle
left & right ventricle
-are muscular chambers that propel the blood out of the heart.
-the RIGHT ventricle to the lungs
-the LEFT ventricle to all other organs
left atrium
hold the blood returning to the heart, and at just the right moment empty into the right and left ventricles.
the atria & the ventricles
Atria-collect blood returning to the heart
Ventricles-discharge blood into vessels to leave the heart
Pericardial cavity
Area surrounding the heart
pericardium
-a double-layered serous membrane that surrounds the heart
-lines the pericardial cavity
pericardial fluid
-Small amount of lubricating fluid in heart.
-Helps reduce friction as the heart moves within the pericardial sac.
The visceral pericardium
(Epicardium)
-covers the hearts outer surface
parietal pericardium
-the tough outermost layer of the pericardium that is attached to the diaphragm and the sternum
-Membrane that forms the inner layer of the pericardial sac
pericardial sac
-surrounds the heart and helps prevent overfilling.
mediastinum
the heart lies in the anterior portion of the mediastinum
the heart contains three layers
1.Epicardium (visceral pericardium)
2.Myocardium (muscular wall of the heart)
3.Endocardium (epithelium covering the inner surfaces of the heart including the valves.
epicardium
-the outermost layer of the heart
-visceral pericardium
myocardium
-thick middle muscle layer of the heart
-pumps blood through the circulatory system
endocardium
-epithelium covering the inner surfaces of the heart including the valves
-Inner layer of the heart
cardiocytes
-cardiac muscle cells
-smaller than skeletal muscle cells
-almost totally dependent on aerobic respiration
coronary arteries
the two arteries that supply blood to the heart muscle.
what do cardiac muscles not require?
-they do not require nervous stimulation to contract
intercalated discs
-interconnect cardiocytes
-specialized bands of tissue inserted between myocardial cells that increase the rate in which the action potential is spread from cell to cell.
how do intercalated discs join cardiac muscle?
-through desmosomes, myofibrils, and gap junctions.
-because cardiac muscle cells are connected in this way, they function like a single enormous cell.
fibrous skeleton
the internal connective tissue of the heart
the function of the fibrous skeleton of the heart
-stabilize the heart's contractile cells and valves
-support the muscle cells, blood vessels, and nerves
-distribute the forces of contraction
-add strength and elasticity
-physically isolate the atria from the ventricles
auricle (atrial appendage)
-expandable extension of the atruim
-One of the two chambers of the heart which receives the blood from the veins.
coronary sulcus
deep groove that marks border between atria and ventricles
anterior interventricular sulcus
depression on anterior surface of the heart - makes the division of left and right ventricles
posterior interventricular sulcus
depression on the posterior surface of the heart - marks the division of the left and right ventricles
where are the great vessels connected to on the heart?
-they are connected to the superior end of the heart at the BASE.
apex
the inferior pointed end of the heart which extends slightly to the left and rests on the diaphragm
what axis of the body does the heart sit?
-sits at an angle to the longitudinal axis of the body
the borders of the heart
-superior
-inferior
-left
-right
the heart has the following surfaces:
-sternocostal surface
-diaphragmatic surface
sternocostal surface
formed by the anterior surfaces of the RIGHT atrium and ventricle
diaphragmatic surface
is formed primarily by the posterior, inferior wall of the LEFT ventricle.
interatrial septum
The wall or septum that divides the left and right atria.
interventricular septum
separates the right and left ventricles
the openings of the atria and ventricles contain:
-folds of connective tissue covered by the endocardium
-these valves maintain a one-way flow of blood
the right atrium receives blood from the systemic circuit through two great veins:
1. the superior vena cava
2. the inferior vena cava
pectinate muscles
-prominent muscular ridges within the atria walls
coronary veins
return blood to the coronary sinus which opens into the right atrium.
coronary sinus
a short sinus receiving most of the veins of the heart
foramen ovale
-during embryonic development an opening penetrates the interatrial septum.
-it closes after birth and leaves a depression
fossa ovalis
A small depression left in the interatrial septum as a result of the closure of the foramen ovale after birth
atrioventricular valve
-A valve in the heart between each atrium and ventricle that prevents a back-flow of blood when the ventricles contract.
-consists of 3 cusps of fibrous tissue braced by the tendinous chordae tendineae
chordae tendineae
heart strings" are tiny white collagenic cords that anchor the cusps to the ventricular walls. They originate from the papillary muscles.
pulmonary trunk
-the artery that carries venous blood from the right ventricle of the heart
-divides into the right and left pulmonary arteries
the left atrium receives oxygenated blood from the left
-left and right pulmonary veins
-it has thicker walls than those of the right atrium
left atrioventricular valve (AV)
-where blood flow to when it leaves the left atrium
-valve with two cusps (mitral or bicuspid)
which ventricle is the largest and thickest of the four chambers and why?
-left ventricle
-because it must pump blood to the entire body
what does blood pass through after it has left the left ventricle?
-passes through the aortic valve and into the systemic circuit via the ascending aorta.
what does blood go through after it passes the ascending aorta?
-through the aortic arch and into the descending aorta
ascending aorta
-Branches off the left ventricle; carries oxygen rich blood to parts of the body above the heart
-Provides blood to the head, neck, and arms.
aortic arch
the bend of the aorta between its ascending and descending portions
descending aorta
the descending part of the aorta that branches into the thoracic and abdominal aortae
right ventricle
-has thin walls
-develops low blood pressure when pumping into the pulmonary circuit to and from the adjacent lungs.
why is low blood pressure necessary for the right ventricle?
-because the pulmonary capillaries at the gas exchange surfaces of the lungs are very delicate.
why does the left ventricle have a thick wall?
because it pumps blood throughout the systemic circuit
The AV valves have four components:
1. a ring of connective tissue attached to the fibrous skeleton of the heart
2. cusps
3.chordae tendineae
4. papillary muscles
the two semilunar valves are:
-Aortic valve
-Pulmonary valve
Aortic valve
a semilunar valve between the left ventricle and the aorta
Pulmonary valve
-a semilunar valve
-gaurds the exits of the left and right ventricles
Why do the valves normally permit blood flow in only one direction?
-to prevent regurgitation (back flow) of blood
The closure of the valves are rushing of blood through the heart cause:
-characteristic "heart sounds" that can be heart during auscultation
heart sounds
Lub-dub. 1st: AV valves close. 2nd: aortic and pulmonary valves close
Blood travels from the right atrium to the right ventricle through what valve?
tricuspid valve
tricuspid valve
The right atrioventricular valve which consists of three cusps
the coronary circulation
supplies blood to the muscles of the heart to meet the high oxygen and nutrient demands of cardiac muscle cells
where do the coronary arteries originate?
-the base of the ascending aorta
-each give rise to two branches
Right coronary artery
-two branches:
1. Right marginal branch
2. Posterior interventricular branch
-supplies blood to right atrium, portions of both ventricles and cells of AV nodes and SA node.
right marginal branch
A branch given off by the RCA that supplies the right border of the heart towards the apex
posterior interventricular branch
from RCA, posterior descending artery, runs toward the apex within the posterior interventricular sulcus
left coronary artery
-gives blood to LV, LA, and interventricular septum
-gives rise to both:
1. Circumflex branch
2. Anterior interventricular branch
Interconnections between artieres are called:
-Anastomoses
-ensure a constant blood supply
The great and middle cardiac veins carry blood from the coronary capillaries to the?
-coronary sinus
the anterior cardiac veins
-drain the anterior surface of the right ventricle and empty directly into the right atrium.
the cardiac cycle consists of period of
-atrial & ventricular "systole"
-atrial & ventricular "diastole
Systole
contraction of heart & the AV valves are closed
Diastole
-relaxation/filling phase of the heart
Cardiac muscle tissue contracts on its own, without neural or hormonal stimulation, this is called?
automaticity or autorthythmicity
Nodal cells (nodes)
-establish the rate of cardiac contraction
-depolarize spontaneously and determine the heart rate
Conducting fibers
distribute the contractile stimulus to the general myocardium.
Pacemaker cells
-found in the sinoatrial node (cardiac pacemaker)
-normally establish the rate of contraction
the main pacemaker region of the heart is in
the wall of the right atrium
from the sinoatrial (SA) node the stimulus travels...
the stimulus travels over the internodal pathways to the atrioventricular (AV) node, then to the AV bundle, which divides into a right and left bundle branch.
Sinoatrial (SA) node
known as the pacemaker of the heart; electrical impulse originates here
internodal pathways
carries action potential to the AV Node
atrioventricular node
fibers located at the base of the right atrium near the ventricle that carry electrical stimulation to the bundle
AV bundle
receives signals from the AV node sends them to the punkinje fibres in ventricles
-divides into right & left bundle branch
purkinje cells
convey the impulses to the ventricular myocardium
during one cardiac cycle the heart spends most of its time in...
diastole
during the period of systole
the inner volume of the atrial chambers decreases