chapter 19- The Heart
what is the orientation of the heart?
- 2nd rib can help locates the 4 corners of the heart - superior right part lies where the coastal cartilages of the 3rd rib joins the sternum - superior left part lies at the coastal cartilages of 2nd rib, a fingers bread lateral to the sternum - inferior right part: lies at the costal cartilahe of the 6th rib - lateral to the sternum - inferior left part (apex part): 5th intercostal space at the midclavicle line- a line extending inferiorly from midpoint of the left clavicle
circumflex artery
- a branch of the left coronary artery - flows coronary sulcus posteriorly and supplies the left atrium and posterior part of the left ventricle - supplies blood to the left atrium, side and back of the left ventricle
serous pericardium
- a closed 2 layer sac sandwiched bw the fibrous pericardium and the heart - 1) parietal layer-- outer layer that adheres to inner surface of fibrous pericardium -2) visceral layer-- layer that lies on the heart and is considered a part of the heart wall -3) pericardial cavity
coronary sulcus
- a groove that marks an external boundary of the 4 chambers - forms a "crown" by circling the boundary bw the atria and ventricles
anterior interventicular sulcus
- a groove that marks an external boundary of the 4 chambers - marks the anterior position of the interventicular septum bw the 2 ventricles
posterior interventicular sulcus
- a groove that marks an external boundary of the 4 chambers - separates the 2 ventricles on the heart's inferior surface
right atrium auricle
- a part of the external surface of the right atrium that overlaps the superior vena cava and seen on the anterior surface
what is referred to as a heartbeat?
- a single sequence of atrial contraction followed by ventricle contraction
anterior interventicular branch
- aka Anterior descending artery - a branch of the left coronary artery - descends in anterior interventicular sulcus toward the apex of heart, sending branches into the interventicular septum and anterior walls of both ventricles - supplies blood to the front and bottom of the left ventricle and the front of the septum
what is Coronary artery disease?
- aka: CAD - waxy substance called plaque builds up inside the coronary arteries - atherosclerosis: accumulation of fatty deposits in the inner lining of the bodys arteries that can blcok blood flow through these arteries - when atherosclerosis affects the coronary arteries, it leads to coronary artery disease (CAD) in which the arteries supplying the heart wall are narrowed or blocked
posterior interventicular artery
- aka: posterior descending artery - a branch from the right coronary artery that continues into posterior part of coronary sulcus into the posterior interventicular sulcus
What blood vessels does the heart get its blood supply from?
- although heart is filled with blood, heart walls are too thick to obtain nutrition by diffusion from this continued blood - instead, blood supply to the muscular walls and tissues of the heart is delivered by the right and left coronary arteries (connected to aorta)
anterior cardiac veins
- anterior surface of the right ventricle contains several horizontal anterior cardiac veins that empty directly into the right atrium
what are the heart vessels that supply/ drain the heart?
- arteries- right and left coronary (in atrioventicular groove), marginal, circumflex, and anterior interventicular arteries - veins- small cardiac, anterior cardiac, and great cardiac vein
what is the significance of intercalated discs?
- at these junctions, the sarcolemmas (cytoplasm) of adjacent cells interolock through meshing "fingers" - they consist of 2 regions: 1) transverse regions contain desmosome-like called fasciae adhesions that function to bind adjacent cells together and transmit the contractile force to adjacent cells 2) longitudinal regions contain gap junctions that allow ions to pass bw cells, transmitting the contractile signal to adjacent cells
how do cardiac muscle cells contract? what is the conducting system?
- cardiac muscle cells have an intrinsic ability to generate and conduct electrical impulses that stimulate these cells to contract rhythmically ---- don't depend on extrinsic nerve impulses - conducting system: series of specialized cardiac muscle cells: autorhythmic cells that carries impulses throughout the heart musculature, signaling heart chambers to contract in proper sequence --- also initiates each contraction sequence which sets the basic heart rate
what is the role of the chordae tendinae and papillary muscles in the AV valves?
- chordae tendinae and the papillary muscles that attach to these valves look like the chords to an open parachute, limiting the closed cusps so that they cant fly up and allow reflux of ventricular blood into the atria - the papillary muscles begin to contract slightly before the rest of the ventricles contracts, pulling on the chordae tendinae and preventing the AV valves from everting - if cusps were not anchored in this manner, they would be forced superiorly into the atria
what makes heart sounds?
- closing of valves causes vibrations in adjacent blood and heart walls that account for the familiar " lub-dup" sounds of each heartbeat
intercalated discs
- complex junctions that join cardiac muscle cells
how is the autonomic input to the heart controlled? how is parasympathetic and sympathetic in specific controlled?
- controlled by cardiac centers in the reticular formation of the medulla in the brain - in medulla, cardio-inhibitory center influences parasympathetic neurons whereas cardio-acceletory center influences sympathetic neurons - these medullary centers, in turn, are influenced by such higher brain regions as the hypothalamus, preaqueductal gray matter, amygdala, and insular cortex
what is the purpose of the brief delay in contraction of the AV node?
- enables the ventricles to fill completely before they start to contract - bc the fibrous skeleton bw the atria and ventricles is nonconducting, it prevents the impulses in the atrial wall from proceeding directly to the ventricular wall - as a result, only the signals that go through can continue on
endocardium
- endothelial layer of the inner myocardial surface - located deep to the myocaridum us a sheet of simple squamous epithelium resting on a thin layer of connective tissue - lines the heart chambers and covers the heart valves
pulmonary arterial hypertension
- enlargement and ultimate failure of the right ventricle resulting from elevated blood pressure in pulmonary circuit - blockage of constriction of vessels in the lungs increases resistance to blood flow which increases blood pressure and forces right ventricle to work harder - acute cases develop from an embolism in pulmonary vessels but chronic cases associated with chronic lung diseases such as emphysema
where is the right ventricle located? where does it receive blood flow from?
- forms most of the anterior surface of the heart - receives blood from the right atrium and pumps into the pulmonary circuit via an artery called the pulmonary trunk
what is the cardiac muscle tissue?
- forms the thick myocardium of the heart wall - contains cardiac muscle cells and the connective tissue that surrounds these cells - the contractions of the cardiac muscle cells pump blood through the heart and into through the blood vessels of the circulatory system
congetsive heart failure and its causes
- heart enlarges while pumping efficiency progressively declines - affects 5 million americans and increases in frequency - hypothesis of causes: 1) initially weakened heart causes sympathetic nervous system to stimulate the heart to pump harder 2) increased demand further weakens the heart which again causes stimulation of sympathetic system, etc
what is the innervation to the heart?
- hearts inherent rate of contraction is set by the SA node, but rate can be altered by extrinsic neural controls - nerves to the heart consist of visceral sensory fibers, parasympathetic fibers that slow heart rate and sympathetic fibers that increase the rate and force of heart contractions -
pectinate muscles
- horizontal ridges that line the right atrium
what are the heart chambers divided by internally?
- internally, heart chambers are divided longitudinally by a portion called either: interatrial septum, or interventricular septum-- this septum is composed of cardiac muscle
what are the internal parts of the right atrium?
- internally, the right atrium has 2 parts: 1) smooth-walled posterior part 2) anterior part lined by ridges (horizontal) called the pectinate muscles ---- the posterior and anterior part are separated by a large c-shaped ridge called the crista terminalis -- continuous with the SA node ----crista= important landmarks to locate the sites where veins enter the right atrium ---- superior vena cava opens into the right atrium just posterior to the superior bend of the crista --- inferior vena cava opens into atrium just posterior to the inferior bend of the crista ---- coronary sinus opens into the atrium just anterior to the inferior end of the crista ---- additionally, posterior to this end of the crista is the fossa ovalis, a depression in the internal septum that marks the spot where an opening existed in the fetal heart -
what are the features of the right ventricle?
- internally, the ventricular walls are marked by irregular ridges of muscle called the trabeculae carneae - additionally, cone-shaped papillary muscles project from the walls into the ventricular cavity - thin, strong bands called the chordae tendinae - the "heart strings" project superiorly from the papillary muscles - superiorly, the opening bw the right ventricle and pulmonary trunk contains the pulmonary semiulnar valve (aka pulmonary valve)
coronary sinus
- largest of the cardiac veins - occupies the posterior part of the coronary sulcus and returns almost all of the venous blood from the heart wall to the right atrium
endomysium
- loose fibrous connective tissue in the intercellular spaces around each cardiac fiber - aids to bind adjacent cardiac fibers together and contains the vessels and nerves that serves the muscle cells - groups of cardiac fibers form the cardiac muscle bundles in the myocardium - the connective tissue surrounding the cardiac fiber merge with fibrous skeleton of the heart and thus function to anchor the muscle cells and transmit the contractile forces produced by insertions of skeletal muscles
myocardium
- muscle heart - cardiac muscler layer forming the bulk of the heart - the layer that actually contracts - cardiac muscle cells in myocardium are connective tissues that bind these cells together into elongates circulatory and spirally arranged networks called bundles - these bundles function to squeeze blood through the atria and superiorly through the ventricles - connective tissues of myocardium form fibrous skeleton of the heart which reinforces the myocardium internally and anchors the cardiac muscle fibers
small cardiac vein
- one of the 3 tributaries that drain into the coronary sinus - location: runs along heart's inferior right atrium
middle cardiac vein
- one of the 3 tributaries that drain into the coronary sinus - located in posterior interventicular sulcus
great cardiac vein
- one of the 3 tributaries that drains into the coronary sinus - located in anterior interventicular sulcus
what is the function of the valves?
- open (to allow blood flow) and close (prevent backflow of blood) in response to differences in blood pressure on each side of the valves
how do parasympathetic nerves arise to the heart?
- parasympathetic nerves arise as branches of the vagus nerve in the neck and thorax
fossa ovalis
- posterior to the end of the crista - a depression in the internal septum that marks the spot where an opening existed in the fetal heart - part of the right atrium
what is heart failure? what are some causes?
- progressive weakening of heart as it fails to keep pace with the demand of pumping blood and can not meet body's need for oxygenated blood - causes: 1) weakened ventricles 2) failure of ventricles to fill completely during diastole 3) overfilling of ventricles 4) congestive heart failure is most common cause
what are the vessels that convey blood away from the heart?
- pulmonary trunk, which splits into right and left pulmonary arteries - ascending aorta (3 branches)- brachiocephalic, left common carotid, and subclavian arteries
how does the parasympathetic innervation influence the heart?
- restricted to the SA and AV nodes and coronary arteries - releases neurotransmitter at the SA nodes that decrease the heart rate
description of the SA node
- sinoatrial node - crescent-shaped mass of muscle cells that lies in the wall of the right atrium, inferior to the entrance of the superior vena cava - this structure contains auto rhythmic cells - SA node sets the basic heart rate by generating 70-80 electrical impulses per minute - it is the hearts pacemaker
what are the vessels of the heart returning blood to the heart?
- superior and inferior vena cavae - right and left pulmonary veins
what is the location of the heart?
- superior surface of the diaphragm - left of the midline - anterior to the vertebral column, posterior to the sternum - largest organ of the mediastinum- bw the 2 lungs
hows does the sympathetic innervation influence the heart?
- sympathetic fibers innervate these same areas and project to the cardiac musculature throughout the heart ---> bc sympathetic fibers affect both rate and strength of contraction - accelerator nerve releases neurotransmitter to the SA node that increases the heart rate
how does the fibrous layer of the heart contribute to the valves?
- the fibrous skeleton of the heart lies in the plane bw the atria and the ventricles and surrounds all 4 heart valves like hand cuffs
what is the pathway in which the heart conducting system travels?
1) Sinoatrial Node (SA): crescent-shaped mass of muscle cells that lies in the wall of the right atrium, inferior to the entrance of the superior vena cava - the signal initiated by the SA node spreads throughout the myocardium signaling the atria to contract through the gap junctions in the intercalated discs - communicates bw nodes through internodal pathways 2) Atrioventicular (AV) Node: through the interatrial septum where they are delayed for a fraction of a sec - located at bottom of the right atrium 3) Atrioventicular (AV) Bundle: connects the atria to ventricles - enters the interventicular septum and divides into left and right bundle branches 4) Bundle branches (AV bundle splits into Left and right bundle branches) - conduct the impulses through the interventicular septum 5) Purkinje Fibers - stimulate the contractile cells of both ventricles - approach the apex of the heart and down the ventricular walls - arrangement ensures that contraction of the ventricles begins at the apex (to travel from bottom up) of the heart and travels superiorly so that the ventricular blood is ejected superiorly into the great arteries
what is the role of the fibrous layer of the skeleton of the heart on the heart valves?
1) anchors valve cusps 2) prevents overdilation of valve openings as blood passes through 3) point of attachment for the bundles of cardiac muscle in the atria and ventricles 4) it blocks the direct spread of electrical impulses from the atria to the ventricles ---> this function is critical for the proper coordination of atrial and ventricular coordinations
what is a common symptom of coronary artery disease?
1) angina pectoris - thoracic pain caused by inadequate oxygenation of the heart muscle cells, which weaken but do not die - although pain from angina usually results from tissue hypoxia, it can also result from stress-induced spasm of atherosclerotic coronary arteries - occur mostly during exercise when vigorously contrasting heart may demand more O2 than narrow coronary arteries 2) myocardial infarction (aka heart attack): - a sharp pain strikes with lightening speed through the chest (and sometimes the left arm and side of the neck) and does not subside - when blockage of a coronary artery is more complete or prolonged, then O2 starved cardiac muscles cells die causing a heart attack - bc cardiac muscle has no satellite cells as skeletal muscles do, it does not regenerate effectively - myocardial damage from a heart attack is irreversible - heart attack is 1st and only symptom of CAD -
what are the heart valves titled in pairs? what is their function?
1) atrioventicular valves 2) semiulnar valves - enforce one-way flow of blood through the heart from the atria to ventricles and into great arteries that leave the superior part of the heart
what is the title of the 2 valves on the right side of the heart?
1) bw atria and ventricle: right atrioventicular valve= tricuspid valve 2) bw the ventricle and the artery: right semiulnar valve/ pulmonary valve
where are the valves located?
1) bw atria and ventricles 2) bw ventricles and their respective arteries
what is the title of the 2 valves on the left side of the heart?
1) bw the atria and the ventricle: left atrioventicular valve= mitral valve/ bicuspid valve 2) bw the ventricle and the artery= aortic valve/ left semiulnar valve
how can you contrast cardiac muscle to skeletal muscle?
1) cardiac muscle has more mitochandria and has branching of the myofibrils which makes the striations be less apparent 2) unlike cells of skeletal muscle, not all cardiac muscle cells are innervate-- no neurons needed to allow blood flow 3) only cardiac muscle cells have intercalated discs-- desmosomes and gap junctions
what are disorders of the heart?
1) coronary artery disease 2) heart failure
what are the external heart chambers of the heart marked by?
1) coronary sulcus: forms a crown by circling the boundary bw the atria and the ventricles 2) anterior interventicular sulcus 3) posterior interventicular sulcus
what are the layers of the heart wall?
1) epicardium (aka visceral layer of serous pericardium) 2) myocardium (muscle heart) 3) endocardium
what is the pathway of the blood throughout the heart?
1) oxygenated-poor blood: body---> superior/ inferior vena cava--> right atrium--> tricuspid valve--> right ventricle--> pulmonary semiulnar valve--> pulmonary arteries --> lungs 2) oxygenated blood: lungs--> pulmonary veins--> left atrium --> bicuspid valve --> left ventricle--> aortic semiulanr valve --> aorta --> systemic circulation
what are the functions of the pericardium?
1) protects and anchors the heart 2) prevents overfilling of the heart with blood 3) allows for the heart to work in a relatively friction-free environment
what are the 2 receiving chambers of the heart?
1) right atrium - receive blood returning from the systemic circuit 2) left atrium - receive blood returning from the pulmonary circuit
what are the 2 functions of the heart?
1) right side- receives oxygen-poor blood from the body tissues and then pumps this blood to the lungs to pick up O2 and disperse CO2 2) left side- receives oxygenated blood returning from lungs and pumps this blood throughout the body to supply O2 and nutrients to the body tissue
what are the 2 main pumping chambers of the heart?
1) right ventricle- pumps blood to the pulmonary artery leading to the pulmonary circuit 2) left ventricle- pumps blood to the aorta leading to the systemic circuit
How can you compare cardiac muscle cells to skeletal muscle cells?
1) striations- as a result of myofibrils with typical sarcomeres composed of: A bands, I band, H zones, titin, Z discs, and M lines 2)contractions 3) sarcoplasmic reticulum 4) T tubules 5) force generation depends on muscle cell's length
disorders of the conduction system? what do they lead to?
1) ventricular fibrillation 2) atrial fibrillation - they lead to atrial fibrillation
what is the thickness of the chambers?
1) walls of the atria are much thinner than those of the ventricles bc much of the ventricular filling is done by gravity and thus the atria exert little effort to propel blood inferiorly into the ventricles 2) walls of the left ventricle (systemic pump) is at leats 3 xs thicker than right ventricle (pulmonary pump) - left ventricle can generate more force than the right ventricle and pumps the blood at a higher pressure - higher pressure in the systemic circuit reflects the fact systemic circuit is much longer than pulmonary circuit and offers greater resistance to blood flow - thick walls of the left ventricle gives this chamber a circular shape and flattens the cavity of the adjacent right ventricle into the shape of a crescent
what are the steps by which the semiulnar valves open and close?
1) when the ventricles contract and raise the intraventicular pressure the semiulmnar valves are forced open and their cusps are flattened against the arterial walls as blood rushes past them 2) when ventricles relax, blood that tends to flow back toward the heart fills the cusps of the semiulnar valve and forces them shut
what are the steps of the valves opening and closing of the atrioventicular valves?
1) when ventricles are relaxed, the cusps of the AV valves hang into the ventricular chambers while blood flows into the atria and down through the open AV valves into the ventricles 2) when the ventricles start to contract, the pressure within them rises and forces the blood superiorly against the valve cusps pushing the edges of the cusps together and closing the AV valves
what are the coverings of the heart (outer to inner layer)
1. Pericardium - double-walled sac around the heart - fibrous pericardium - serous pericardium -----> parietal layer -----> pericardial cavity -----> visceral layer 2. epicardium (aka visceral layer of the serous membrane) 3. myocardium 4. endocardium
what are the 4 chambers of the heart?
1. right atria 2. left atria 3. right ventricle 4. left ventricle
what does each valve consist of?
2 or 3 cusps which are composed of flaps of endocardium reinforced by cores of dense connective tissues
Right (acute) marginal artery
a branch formed by the right coronary artery - forms at the inferior border of the heart
Pericardium
a double-walled sac around the heart composed of: 1) superficial fibrous pericardium 2) deep 2 layer serous pericardium -- parietal layer lines the internal surface of the fibrous pericardium -- the visceral layer or epicardium lines the surface of the heart -- they are separated by the fluid-filled pericardial cavity
crista terminalis
a large C-shaped ridge that separates the posterior part and interior part of the right atrium - internally, it is continuous with the SA node
what position does the heart assume?
an oblique position in the thorax with its pointed apex lying to the left of the midline and anterior to the rest of the heart
what are gap junctions? where are they located? what is their advantage?
an organized collections of protein channels in the intercalated discs of cardiac muscle - the free movement of ions bw cells allows the direct transmission of an electrical impulse through the entire network of cardiac muscle cells - the impulse stimulates all the muscle cells in a heart chamber (atria or ventricles) to contract at the same time
describe the pathway of the left coronary artery and the branches it has? what part of the heart does it supply blood to?
arises from the left side of the aorta, passes posterior to the pulmonary trunk, and then divides into 2 branches: 1) anterior interventicular 2) circumflex artery ---- contains left marginal artery - supplies blood to left atrium and left ventricle
what is silent ischemia? who commonly gets it? how can it be detected?
blood flow of heart is interupted often, as in angina, but w/o any pain to provide warning - can also occur in some heart attack survivors - can be detected by measuring the heart rhythm through an ECG in exercise ----> treadmill test
pulmonary circuits
blood vessels that carry blood to and from the lungs
where do all nerves pass before entering the heart?
cardiac plexus on the trachea
what are the cardiac veins?
carry deoxygenated blood from the heart wall into the right atrium, also occupy the sulci on the heart surface - largest of these veins: - coronary sinus - draining into coronary sinus are 3 tributaries: - great cardiac vein - middle cardiac vein - small cardiac vein
what is the systole phase?
describes the contraction of the ventricles
describe the pathway of the right coronary artery and the branches it forms? what part of the heart does the right coronary artery supply blood to?
emerges from the right side of the aorta and descends in the coronary sulcus on the anterior surface of the heart, bw the right atrium and right ventricle - branches formed from the right coronary artery: - Right (acute) marginal artery - posterior interventicular artery - overall, it supplies blood to the right atrium and almost all of the right ventricle
where does the left ventricle receive the blood from? where is it located? what features does it contain?
forms the apex of the heart and dominates the hearts inferior surface - pumps blood into the systemic circuit - like the right ventricle, it contains trabeculae carnae, papillary muscles, chordae tendinae and cusps of the anterioventicular (mitral) valve - superiorly, the left ventricle opens into the stem artery of the systemic circulation (the aorta) through the semiulnar valve (or simply, aortic valve)
where is the right atrium located? what kind of blood does it receive? how does it receive blood?
forms the entire right border of the human heart - receiving chamber for oxygen-poor blood returning from systemic circuit - right atrium receives blood via 3 veins: superior vena cava, inferior vena cava, and coronary sinus
where does the left atrium receive the blood from and where does it flow the blood to? what kind of blood? where is it located? what is the internal structure?
makes up most of the hearts posterior surface - receives O2-rich blood returning from the lungs through the 2 right and and 2 left pulmonary veins - only part visible anteriorly is the triangular left auricle - internally, most of the atrial wall is smooth with pectinate muscles lining the auricle only. - the left atrium opens into the left ventricle through the mitral valve (left atrioventicular valve)
do the AV valves close at the same time and do the Semiulnar valves close at the same time? what is the timing at which the valves close?
mitral valve closes slightly before the tricuspid closes and aortic valve generally closes just before the pulmonary valve closes - bc of these differences, the clinician can discern the closing of each of the valves
what is the function of the AV valves?
prevent the backflow of blood into the atria during contraction of the ventricles
what is the function of the semiulnar valves?
prevents backflow from great arteries into the ventricles
how is the lub sound of the heart produced?
produced by the closing of the AV valves at the start of the ventricular contraction
how is the dup sounds of the heart produced?
produced by the closing of the semiulnar valves at the end of ventricular contraction
what is the size of the heart?
proximately the size of your wrist
characteristics of the cardiac muscle cells
short, branching cell with one nucelus centrally-located - striated (with sarcomeres) - each cell is about 25 -120 micrometers in diameter - adjacent cardiac muscle cells are joined together at ends to form cellular networks - these branching networks of cardiac muscles cells are called cardiac fibers
what is the pericardial cavity
slitlike space bw the parietal and visceral layers of the serous pericardium - epitheial cells of the serous pericardium that line the pericardial cavity secrete a lubricating film of serous fluid into the pericardial cavity - fluid reduces friction bw beating heart and outer wall of pericardial sac - pericardial cavity--> division of embryonic coelom that separates the inner tube from the outer tube
fibrous pericardium
strong layer of dense connective tissue - adheres to diaphragm inferiorly and superiorly it is fused to the roots of the great vessels that leave and enter the heart - tough outer coat that holds the heart in place and keeps it from overfilling with blood
how do the sympathetic nerves arise to the heart?
sympathetic nerves travel to the heart from the cervical and upper thoracic chain ganglia
what is the diastole phase?
the phase at which the ventricles are relaxing and filling with blood
systemic circuit
vessels that transport blood to and from all body tissues
epicardium
visceral layer of the serous pericardium - this membrane is often infiltrated with fat, especially in older people