Anatomy of the Heart Flashcards
where is the heart located?
in the mediastinumbetween the sternum. vertebrae, and lungs
give the range of the weight of the heart in dogs
between 0.5-16 oz
give the weight range of the heart in horses
between 8-10lbs
where does about 2/3 of the mass of the heart lie?
on the left side of the midline of the body
describe the apex of the heart (location)
- bottom pointy part
- directed anteriorly, inferiorly, and to the left
describe the base of the heart
- basal part
- directed posteriorly, supreriorly, and to the right
what is the pericardium?
the sac of tissue (membrane) that protects the heart and holds it in place
how many parts does the pericardium have? list and describe location
- fibrous (most superficial)
- serous (innermost)
describe the fibrous portion of the pericardium (4; 3 are functions)
- outer, thicker layer made of tough, inelastic connective tissue
- prevents overstretching of the heart
- provides protection
- anchors heart to the mediastinum
describe the serous portion of the pericardium (2)
- more delicate, inner membrane layer
- has two parts that form a double layer around the heart: parietal and visceral
describe the visceral part of the serous portion of the pericardium; give an alternative name
adheres tightly to the surface of the heart; also called epicardium
what is found between the visceral and parietal layers of the serous portion of the percardium? what is its function?
pericardial fluid; reduces friction as the heart moves
what is pericarditis, generally?
inflammation of the pericardium
what are the 2 main types of pericarditis?
- acute
- chronic
describe acute pericarditis (how common, possible link, symptoms, duration, how treated)
- the most common type
- sudden onset with no known cause usually
- sometimes linked to viral infection
- chest pain that may extend to left shoulder and arm
- lasts about 1 week
- treat to reduce inflammation and pain
what are the 2 types of chronic pericarditis?
- effusive
- constrictive
escribe chronic pericarditis (generally, not the types yet)
- gradual onset, long lasting
- can be life threatening if great fluid accumulation
- most causes are unknown but sometimes related to cancer or TB
- treat by draining excess fluid through needle passed into pericardial cavity
describe effusive chronic pericarditis
more common, fluid-filling or accumulation
describe constrictive chronic pericarditis
fibrous scar tissue forms around the heart, meaning the heart can’t fill properly and leads to heart failure
how does fluid accumulation in chronic pericarditis lead to badness?
it compresses the heart, resulting in cardiac tamponade
list the 3 layers of the heart wall, from outer to innermost
- epicardium/ visceral serous pericardium
- myocardium
- endocardium
describe the epicardium of the heart wall
outermost, thin, transparent layer of the heart wall. also called visceral layer of serous pericardium
describe the myocardium of the heart wall (4)
- made of cardiac muscle tissue
- makes up the bulk of the heart
- responsible for the pumping action
- cardiac muscle fibers swirl diagonally around the heart in bundles
describe the endocardium of the heart wall (4)
- thin layer of endothelium overlying a thin layer of connective tissue
- privides smooth lining for chambers of the heart
- covers valves of the heart
- continuous with endothelial lining of large blood vessels attached to the heart
what is myocarditis?
inflammation of the myocardium
how is myocarditis usually caused?
usually a complication of viral infection, rheumatic fever, or exposure to radiation
describe the symptoms of myocarditis
often no symptoms but if any will be
1. fever
2. fatigue
3. vague chest pain
4. irregulaar heart beat
5. joint pain
6. breathlessness
describe severity and longevity of myocarditis
usually mild with recovery within 2 weeks
what can a severe case of mycarditis result in?
cardiac failure
what is endocarditis? what does it usually involve and what is it typically cuased by?
inflammation of the endocardium; usually involves the heart valves and caused by bacteria
what are the symptoms of endocarditis?
- fever
- heart murmur
- irregular heart beat
- fatigue
- loss of appetite
- night sweats
- chills
how is endocarditis usually treated?
intravenous antibiotics
give 3 risk factors that would make one more susceptible to endocarditis
- congenital heart issues
- dental procedures
- heart surgery
what are auricles? (3)
- the anterior surface of each atrium
- wirnkled, puch-like structures
- slightly increase capacity of atrium so it can hold greater volume of blood
what are sulci? (2)
- grooves in the heart
- contain coronary blood vessels and fat
what is the deep coronary sulcus?
encircles most of the heart and marks boundary between superior atria and inferior ventricles
what 3 sources does the right atrium receive blood from?
- superior vena cava
- inferior vena cava
- coronary sinus
what is the tricuspid valve? what is it also called? what is its function
also called the right atrioventricular (AV) valve; has three cusps and allows blood to pass from the right atrium to the right ventricle
what is the right AV valve/tricuspid valve composed of?
dense connective tissue covered by endocardium
what does the right ventricle form?
most of the anterior surface of the heart
give 3 structures that the right ventricle contains
- trabeculae carneae
- chordae tendineae
- intraventricular septum
what are trabeculae carneae? provide function
a series of ridges formed by raised bundles of cardiac muscle fibers that convey part of the conduction system of the heart
what are chordae tendineae?
tendon-like chords connected to the cusps of the tricuspid valve that are also connected to the conec shaped trabeculae carnea called papillary muscles
how is the right ventricle separated from the left ventricle?
by the interventricular septum
where does blood flow from the right ventricle?
through the pulmonary valve into the pulmonary trunk, which divides into R and L pulmonary arteries
what forms most of the base of the heart?
the left ventricle
where does the left atrium receive blood from and through what?
the lungs through 4 pulmonary valves
what does blood have to pass through to enter the left ventricle from the lungs? what is this also called?
the bicuspid valve/mitral valve/left AV valve; has two cusps
what forms the apex of the heart?
the left ventricle
name 2 structures that the left ventricle contains
- trabeculae carneae
- chordae tendineae
what is the function of the trabeculae carneae and chordae tendineae in the left and right ventricles?
to prevent backflow into the atria
where doesgo when the left ventricle contracts?
through the aortic valve into the ascending aorta, and some of the blood flows into the coronary arteries that branch from the ascending aorta, while the remainder of the blood passes into the aortic arch and into the descending aorta then to the body
what is the reason for the variation of myocardial thickness of each chamber?
they all perform different functions, so need different muscle thickness
why are the atria relatively thin-walled of myocardium?
the only have to deliver blood to adjacent ventricles
why do the ventricles have thicker myocardium?
the have to pump blood a greater distance
compare and contract the R and L ventricles (4)
- they are two separate pumps
- they simultaneously eject EQUAL quantities of blood
- the right ventricle has a smaller workload
- the left ventricle pumps blood a much greater distance
why does the right ventricle have a smaller workload than the left ventricle?
it only pumps blood to the lungs at lower pressure and it only has to overcome a small resistance to blood flow
describe the resistance and pressure the left ventricle must overcome to pump blood
much greater resistance against much higher pressure to deliver blood to the rest of the body
what is the stabilizing factor for the heart valves?
the fibrous skeleton of the heart
what is the fibrous skeleton of the heart made of?
dense connective tissue forming 4 rings that surround the valves of the heart, fuse with one another, and merge with the interventricular septum
what is the role of the fibrous skeleton of the heart? (3)
- prevents overstretching of valves as blood passes through them
- serves as a point of insertion for bundles of cardiac muscle fibers
- acts as an electrical insulator between atria and ventricles
where are the atrioventricular valves located?
between the atria and the ventricles
give the two atrioventricular valves and what side they’re on
tricuspid on the right, biscupid on the left
when the AV valves are open, where do the pointed ends of the cusps project?
into the ventricle
describe the chordae tendineae and papillary muscles when the ventricles are relaxed and what happens to blood in this state
papillary muscles: relaxed
chordae tendineae: slack
blood moves from high pressure in atria to lower pressure in ventricles
describe the chordae tendineae and papillary muscles when the ventricles are contracting and what happens to blood in this state
papillary muscles: contract and pull on chordae tendineae as the pressure of the blood drives the cusps of AV valves upward so the edges meet and close the opening
what could happen if the AV valve or chordae tendineae are damaged?
blood may regurgitate into atria when ventricles contract
in what direction do the cusps of the AV valves fall?
in the direction of blood flow
what is the overall purpose of the AV valves, chordae tendineae, and papillary muscles?
to prevent leakage
what state are the ventricles in when the AV valves are closed?
ventricles contracting when AV valves are closed
what are the 2 semilunar valves? what are they made up of?
aortic and pulmonary; made up of 3 crescent moon shaped cusps
what is the function of the semilunar valves?
allow ejection of blood from heart into arteries and prevent backflow of blood into ventricles
where do the borders of the cusps of the semilunar valves project?
into the lumen of their arteries
what happens to the pressure in the ventricles when they contract?
the pressure in the chamber of the ventricle increases
when do the semilunar valves open? what does this result in?
when pressure in the ventricle exceeds the pressure in the arteries; blood is ejected into the pulmonary trunk and aorta
what happens when the ventricles relax and what does this result in?
blood starts to flow back to the heart, filling the valve cusps, which causes the semilunar valves to close tightly
give the 4 major differences between the semilunar and AV valves
- high pressure in arteries at the end of systole causes SL valves to snap to closed position in contrast to the softer closure of AV valves
- because of the smaller openings, the velocity of blood ejection through the aortic and pulmonary claves is much greater than through the much larger AV valves
- because of the rapid closure and rapid ejection, the edges of the aortic and pulmonary valves are subjected to much greater mechanical stress than AV valves (more likely to get roughed up)
- AV valves are supported by the chordae tendineae, the SL valves are not
what are the heart sounds heard on auscultation and what do they indicate?
lubb (AV valve closure and turbulence) dupp (SL valve closure and turbulence)
which of the heart sounds is quicker and why?
the dupp is quicker because the SL valves close quicker and have more blood turbulence
are there any valves giarding the junctions between the right atrium/vena cavae or left atrium/pulmonary veins? why or why not?
no valves because any loss where blood comes into the atria is insignificant and as atrial muscles contract, they compress and nearly collapse the venous entry points (most backflow minimized)
what are the 2 types of heart valve disorders? describe generally
- stenosis: narrowing of heart valve opening that restricts blood flow
- insufficiency or incompetence: failure of valve to close completely
what is mitral stenosis?
scar formation or congenital defect causes narrowing of mitral valve
what is mitral insufficiency?
backflow of blood from L ventricle to L atrium
what can mitral valve insufficiency be caused by?
mitral valve prolapse (MVP)
what is mitral valve prolapse (MVP)? also give prevalence
- one or both cusps of the mitral valve protrude into L atrium during ventricular contraction
- one of the most common valve disorders (30% of population!!)
- more common in women
what is aortic stenosis? who affected more and why?
- when the aortic valve is narrowed
- takes time (decades) to develop so often see elderly affected more
when is aortic stenosis often noticed and why?
during exercise (will pass out)
what is the most common valvular disorder in the western world?
aortic stenosis
what are 3 common causes of aortic stenosis?
- rheumatic fever
- calcium imbalance
- endocarditis
what is rheumatic fever?
an autoimmune disease that often results from strep or scarlet fever that targets that aortic and mitral valves
what are the 2 closed circuits in which the heart pumps blood? describe how related
- systemic
- pulmonary
the output of one becomes the input of the other
what is the left side of the heart a pump for?
systemic circulation
describe systemic circulation involving the left side of the heart (9)
- left atrium receives O2 rich blood from pulmonary circulation (lungs)
2.passes through left AV valve into left ventricle - left ventricle ejects blood into the aorta
- blood enters progressively smaller systemic arteries then goes to organs (not lungs)
- exchange of nutrients and gases occur across thin-walled capillaries
- blood unloads O2 and picks up CO2
- blood flows through one capillary and enters systemic venule
- venues carry deO2 blood away from tissues and merge to form larger systemic veins
- blood flows back to R atrium
what is the right side of the heart a pump for?
pulmonary circulation
describe pulmonary circulation invovling the right side of the heart
- right atrium receives deO2 blood coming from systemic circulation
- blood pases through right AV valve into R ventricle, which ejects blood into the pulmonary trunk
- the pulmonary trunk brances into pulmonary arteries and carries blood to the lungs
- blood unload CO2 in pulmonary capillaries (whihc is exhaled)
- O2 is inhaled and oxygenated blood flows into pulmonary veins, returning to L atrium
what is coronary circulation?
the myocardium’s network of blood vessels
what do R and L coronary arteries branch from and form?
the ascending aorta to encircle the heart
describe blood flow in coronary circulation whule the heart is contracting and why
low blood flow because coronary arteries are squeezed shut
describe what happens in the coronary arteries when the heart is relaxed and why
high pressure in the aorta proels blood through coronary arteries and into capillaries, then to into coronary veins
how are all areas of the myocardium supplied with blood?
R and L coronary arteries branch from the ascending aorta then branch further to supply
what are anastomoses? (3) what do they do?
- connections where 2 or more arteries supply the same region of tissue
- end-to-end union of blood vessels (lymphatic vessels or nerves)
- provide alternate routes for blood to reach an organ or tissue
what happens in the coronary veins after blood passes through the coronary arteries and flows into capillaries?
- blood delivers O2 and nutrients to heart muscle
- blood collects CO2 and waste
- then moves into coronary veins
where does most deoxygenated blood drain into from the coronary veins?
into the large vascular sinus (coronary sinus) in the coronary sulcus
what happens to the deoxygenated blood in the coronary sinus?
empties into the R atrium
what is reperfusion?
reestablishment of blood flow after blockage of the coronary artery deprives myocardium of O2
how can reperfusion damage myocardial tissue further? (3)
- formation of oxygen free radicals from reintroduced O2
- these unstable and highly reactive molecules cause chain reactions that lead to cellular damage/death
- during myocardial reperfusion, a burst of oxygen-derived free radicals overwhelms normal cellulaar defenses
- they can oxidize lipids, leading to membrane dysfunction and also alter nucleic or other proteins
how are sources of ROS elicited by early reperfusion?
- variations within the mitochondrial electron chain
- disruption of normal metabolism
what are superoxide dismutase and catalase?
enzymes that convert free radicals to less reactive substances (the body’s protection from ROS)
what are 2 methods to lessen reperfusion issues?
- ischemic post conditioning: rapid, intermittent introduction of blood flow
- antioxidant treatment
what is myocardial ischemia?
partial obstruction of blood flow in coronary arteries
what is caused by myocardial ischemia? (2)
- hypoxia (reduced O2 supply)
- may weaken cells without killing them
what is angina pectoris (5)
- strangled chest
- severe pain that usually accompanies myocardial ischemia
- tightness or squeezing sensation
- pain often to the neck, chin, and down the left arm
- may indicate impending heart attack! (Act fast!)
what is myocardial infarction?
a heart attack; complete obstruction to blood flow in coronary artery
what does infarction mean?
death of tissue because of interrupted blood supply
what happens as a result of myocardial infarction always (2)
- heart tissue distal to the obstruction dies and is replaced by non-contractile scar tissue
- heart loses some of its strength
what can happen as a result of myocardial infarction depending on size and location of infarcted area? (2)
- may be disruption of conduction system
- may cause sudden death by triggering ventricle fibrillation
give 3 treatments for mycoardial infarction
- clost dissolving (thrombolytic) agent and heparin
- coronary angioplasty (trying to open vessel)
- coronary artery bypass grafting
contrast cardiac muscle to skeletal muscle
shorter in length and hella branched
describe the inercalatede discs of cardiac muscle
irregular trasnverse thickenings of sarcolemma
what are sarcolemma
cell membranes that separate individual cardiac muscles from on another
what do intercalated discs do
connect the ends of cardiac muscle fibers
what do intercalated discs contain, what do they do? (2)
- desmosomes that hold the fibers together
- gap junctions that allow rapid diffusion of ions (action potentials) to travel easily from one cardiac msucle cell to the next
describe the concept of syncytium
when one heart muscle cell contracts, the rest of the cells in the area also contract; allows for coordinated contraction
conpare cardiac muscle cell mitochondria to skeletal muscle cell mitochondria
cardiac cells have more mitochondria
compare cardiac and skeletal msucle fibers
- same arrangement of actin and myosin
- same bands, zones, and Z disks
contrast tranverse tubules in cardiac muscle versus skeletal muscle cells
wider transverse tubules in cardiac but less abundant; smaller sarcoplasmic reticulum because smaller intracellular reserve of Ca2+
