surfaces of the heart
- the heart is a cone-shaped structure about the size of a closed fist
- it is located in the mediastinum, near the midline of the thoracic cavity, and rests on the diaphragm
- it is composed of an apex, base, left and right border, inferior and anterior
Apex
the pointed portion directed anterior, inferior and to the left
Base
the part opposite the apex, directed posteriorly, superiorly, and to the right
Left border
faces the left lung and extends from the base to apex
Right border
faces the rright lung and extends from the inferior surface to the base
inferior surface
surface on the diaphragm between the apex and the right border
anterior surface
portion against the sternum and ribs
Location of the heart
found between the third through sixth costal cartilage's and between the second through the fifth intercostal spaces
pericardium
sac-like membrane surrounding the heart with two layers
Fibrous pericardium
-a tough, dense irregular connective tissue bag tht prevents the heart from overstretching, protects and anchors the heart in the mediastinum
Serous pericardium
a deeper thinner double layer of membrane with two parts
parietal layer- outer portion fused to the fibrous pericardium
visceral later- inner layer also know as the epicardium which adhears to the heart
Periocardial cavity
space between the parietal and visceral layers which contains a slippery fluid called pericardial fluid, which protects the membranes from friction as the heart moves
Pericarditis
Inflammation of the pericardium which can be caused from an increase or diminished amount of pericardial fluid.
-too much pericardial fluid can compress the heart, due to the lack of stretch in the pericardium, called cardiac tamponade.
Name the layers of the heart wall
epicardium, myocardium, endocardium
epicardium
the outer smooth slippery layer (visceral layer of the serous pericardium)
Myocardium
the middle layer consisting of cardiac muscle tissue which make up the most of the heart
endocardium
innermost thin layer of connective tissue, providing the smooth lining of the chambers and valves of the heart
Chambers of the heart
The heart contains four chambers, two upper chamber or atria and two lower chambers or ventricles
auricle
pouch-like structure on the anterior surface of each atrium
sulci
grooves on surface of heart which contain blood vessels, fat, and mark the external boundaries of the heart
Coronary sulcus
encircles of the heart and is the boundary between the atria and ventricles
anterior interventriclar sulcus
anterior boundary between the left and right ventricles
posterior interventricular sulcus
posterior boundary between the ventricles
Functions of the right atrium
-forms the right border of the heart and is supplied blood by three veinsl the superior vena cava (SVC), inferior vena cava (IVC) and the coronary sinus
pectinate muscles (right atrium)
found in the anterior wall of the atrium and auricle and give it a rough wavy appearance
interatrial septum (right atrium)
thin partition between atria
Foassa ovalis (right atrium)
small oval depression of the septum which is the remnant of the foramen ovale of the fetal heart
tricupsid valve (right atrium)
a three leaf or sup valve which allows blood to flow into the right ventricle from the right atrium
Right Ventricle
forms most of the anterior surface of the heart.
trabeculae carneae (R&L ventricle)
ridges in the walls of the ventricles which carry some of the conducion system of the heart
Chordae tenineae (R&L ventricles)
cords that attach the cusps of the tricuspid valve
Papillary muscles (R&L ventricle)
cone-shaped trabeculae carneae that connects to cords
interventicular septum
partition of separtation between the ventricles
pulmonary valve (R Ventricle)
blood is pumped from the right ventricle through this valve into a large artery the pulmonary trunk wihich divides into left and right pulmonary arteries going to the lungs
Left atrium
forms most of the base of the heart, receives blood from four pulmonary veins.
-it has a smooth posterior wall and smooth anterior wall due to the lack of presence of trabeculae
Bicuspid (mitral) valve (L atrium)
a two susp valve for the passage of blood from the left atrium to the left ventricle
Left ventricle
form the apex of the heart
Aortic valve (L ventricle)
the valve in the left ventricle through which, blood passes into the ascending aorta, the largest artery of the body
coronary arteries (L ventricle)
supply blood to the heart wall
variations of thickness of myocardium in the chambers of the heart
-atria are thin-walled for less workload
-ventricles are thicker walled for more workload
-the left ventricle has a thicker wall than the right for pumping harder against resistance
Atrioventricular valves (AV)
the bi and tricuspid valves located between the atria and ventricle which open when atrial pressure is greater than ventricular pressure
Semilunar (SV) valves
the pulmonary and aortic valves which prevent backflow of blood into the ventricles and open when ventricular pressure is greater than arterial pressure
Fibrous skeleton of the heart
functions to serve as attachment points for the valves, prevent overstretching of the valves, and acts as an electrical insulator that prevents the direct spread of action potentials from the atria to ventricles.
the parts the fibrous skeleton consist of (4)
1. four fibrous rings around the valves
2. right fibrous trigone- a mass of fibrous connective tissue between the left atrioventricular, aortic, and right atrioventricular fibrous rings
3. left fibrous trigone- a smaller connective tissue mass between the
Left coronary artery
passes inferior to the left auricle and divides into the anterior interventricular branch and the circumflex branch
anterior interventricular branch
runs in the anterior interventricular sulcus and supplies both ventricles
circumflex branch
runs in the coronary culcus and supplies the left atrium and ventricle
Right coronary artery
runs inferior to the right auricle and supplies the right atrium before dividing into the marginal and posterior interventricular branches
Marginal branch
branch off of the right coronary artery, supplies the right ventricle
Posterior interventricular branch
branch off of the right coronary artery, runs in the posterior interventricular sulcus and supplies the ventricles
Anastomosis
connection between two different arteries in the same region
-provide detours for arterial blood if a main route becomes obstructed
Coronary veins
collect deoxygenated blood and drains into the coronary sinus on the posterior surface of the heart the coronary sinus then empties into the right atrium
What are the major veins that drain into the cardiac sinus?
Great cardiac vein and middle cardiac vein
What are the differences between skeletal muscle fibers and cardiac muscle fibers?
- shorter length, diameter, Y-shaped fibers
-centrally located nucleus
-more sarcoplasm, less sarcoplasmic reticulum
- larger and more numerous mitochondria
- less transverse tubules and found at Z disks
- intercalated disks containing desmosomes and gap
Autorhythmic (pacemaker) cells of the heart
repeatedly and rhythmically produce action potentials and act as the pacemaker of the heart forming the conduction system
Conduction system of the heart
sinoatrial (SA) node > atrioventricular (AV) node > atrioventricular bundle (bundle of His) > right and left bundle branches > conduction bundles (pukinje fibers)
ectopic pacemaker and factors that cause it
site other than the SA node that becomes the self-excitable pacemaker, usually producing an irregular heartbeat.
Factors causing ectopic activity include caffeine, nicotine, electrolyte imbalances, hypoxia, and toxic reactions to drugs like digitalis
ECG
a graph of the eclectrical changes accompanying the heartbeat
P wave
spread of the action potential from the SA node through the two atria
QRS wave
spread of action potential through the ventricles
T wave
indicates ventricular relaxation
What is going on in as far as contraction goes in the atrias and ventricles during a normal heart beat
When the two atria contract the two ventricles are relaxing. When the ventricles contract the two atria relax
Systole/diastole
phase of contraction/phase of relaxation
Explain the cardiac cycle
1. relaxation period
2. ventricular filling
3. ventricular systole
Relaxation period
all four chambers are in diastole and blood starts to flow from the pulmonary trunk and aorta back into the ventricles
-pressure falls in the ventricles, the AV valves open and ventricles start filling
Ventricular filling
ventricles fill to about 75% capacity then the atria contract to fill the remaining 25%
-semilunar valves are closed
Ventricular systole
ventricular contraction forces blood to close the AV valves and open the semilunar valves to force blood from the heart.
-semilunar valves of the ventricles relax
Heart sounds
During each cardiac cycle four heard sounds are generated but only two are usually heard with a stethoscope.
-S1 (lubb sound) is the first sound generate by the closure of the AV valves soon after ventricular systole begins
-S2 (dub sound) is the second s
Auscultation
listening to sounds within the body (usually with a stethoscope)