Week 5, Lecture 3 Flashcards
If you place a stethoscope at the 2nd right intercostal space at the sternal border, what cardiac structure are you likely listening to?
A. The aortic valve
B. The pulmonic valve
C. The tricuspid valve
D. The mitral valve
A. The aortic valve
What structure brings oxygenated blood to the embryonic heart?
A. The cardinal vein
B. The umbilical artery
C. The dorsal aorta
D. The umbilical vein
D. The umbilical vein
What is the papillary muscle attached to?
A. The chordae tendinae of a semilunar valve
B. The chordae tendinae of an atrioventricular valve
C. Both the left and right aspects of the interventricular septum
D. Both the left and right aspects of the interatrial septum
B. The chordae tendinae of an atrioventricular valve
what is the mediastinum
the middle of the thorax
Between the mediastinal pleura
Posterior to the sternum
Anterior to the vertebrae
Superior to the diaphragm
Separates the two lateral pleural cavities
subdivisions of the mediastinum
Superior
Inferior
* Anterior
* Middle
* Posterior
where is the heart located
The heart and pericardial sac are approximately 2/3rd to the left and 1/3rd to the right of the median plane (middle mediastinum).
4 spots on the heart to listen to
aortic valve
pulmonary valve
tricuspid valve
mitral valve
in order from top to bottom where to listen on heart
APTM
aortic (upper middle)
pulmonary (upper left)
tricuspid (bottom middle)
mitral (bottom left)
mitral valve
(apex): 5th intercostal space at the midclavicular line.
tricuspid valve
lower left sternal border in the 4th/5th intercostal space.
aortic valve
2nd right intercostal space near the right sternal border.
pulmonic valve
2nd left intercostal space near the left sternal border.
pericardium function
Fibrous membrane that encloses the heart and the roots of the great vessels.
Anchors and protects the heart
Prevents overfilling
Allows it to work in a friction-free environment
2 layers of the pericardium
Outer fibrous pericardium (tough, inelastic CT)
Inner serous pericardium.
* Parietal layer (inner surface of the pericardium)
* Visceral layer (lines outer surface of the heart= epicardium)
what are the 2 parts of the inner serous pericardium? which is inner most layer of pericardium/outer layer of heart (epicardium)
parietal and visceral layer
visceral layer is inner most layer
pericardiophrenic ligament; the fibrous pericardium (outer layer) is continuous with what
the central tendon of the diaphragm
3 walls of the heart chamber from superficial to deep
- endocardium
- myocardium
- epicardium (outer most layer of heart, inner most layer or pericardium)
3 layers of heart chamber
- Endocardium: a thin internal layer (endothelium and subendothelial connective tissue) or lining membrane of the heart that also covers its valves
- Myocardium: a thick, helical middle layer composed of cardiac muscle
- Epicardium: a thin external layer (mesothelium) formed by the visceral layer of serous pericardium
epicardium is? what’s it made of?
is the outermost layer of the heart wall, also called the visceral layer of the serous pericardium
The serous pericardium is composed mainly of mesothelium.
what’s in the subepicardial layer
loose CT contains the coronary vessels, nerves and ganglia, also an area of fat storage of the heart
what type of cells are in the myocardium (hint contractile cells and conducting cells)
cardiomyocytes
purkinje fibers
cardiomyocytes
are the individual muscle cells that make up the myocardium.
* Striated, uninuclear, often with one or two branches * Full of myofibrils and mitochondria
purkinje fibers
are specialized cardiac muscle fibers that play a crucial role in the conduction of electrical signals within the heart.
- Glycogen-filled, large diameter fibres, gap junctions, few myofibrils or mitochondria
different between cardiomyocytes and purkinje fibers
cardiomyocytes have lots of mitochondria and myofibrils (for contraction)
purjinke fibers have glycogen and gap junctions (for conduction/ impulse generation)
3 components of myocardium
papillary muscles
pectinate muscles
trabecular carneae
papillary muscle found where? connect by?
located in the ventricles of the heart.
Connected to the AV valves by chordae tendineae.
pectinate muscles are found where? and help do what?
muscular structures found in the walls of the atria, particularly in the right atrium.
Contribute to the contraction of the atria.
trabecular carneae is found where and does what
irregular, mesh-like ridges or muscular columns found on
the inner walls of the ventricles.
Structural support for ventricles & maintain integrity of myocardium
intercalated discs in myocardium have
desmosomes and gap junctions and fascia adherents
Desmosomes: hold cells together; prevent cells
from separating during contraction
Gap junctions: directly connect the cytoplasm of 2 cells – allow ions to pass from cell to cell; electrically couple adjacent cells
* Allows heart to be a functional syncytium, a single coordinated unit
Fascia adherens: anchors actin filaments, helps to transmit contractile forces
endocardium forms the
lining of the atria and ventricles
endocardium is made up of what type of cell and what tissue
Simple squamous epithelium (endothelium)
Underlying layer of fibroelastic connective tissue with
scattered fibroblasts
Deeper layer of subendothelial fibroelastic CT.
- Contains: small blood vessels & nerves, Purkinje fibers
endocardial cells are found where
specialized cells that make up
the endocardium.
Form the inner lining of the AV and semilunar valves, ensuring they open and close efficiently during the cardiac cycle.
cardiac muscle cells
- how many nuclei?
-connected by?
-how many mitochondria?
-made of?
striated, short, branched, fat, interconnected
– Uninuclear cells
* Nucleus is situated at the center of the cell body
– Cells connected at intercalated discs
* Many gap junctions populate the intercalated discs
– Contain numerous large mitochondria (25–35% of cell volume) that
afford resistance to fatigue
– Rest of volume composed of sarcomeres
* Z discs, A bands, and I bands all present
– T tubules and cisternae present
* Sarcoplasmic Reticulum is simpler than in skeletal muscle
* T-tubules are larger
what are cardiac muscle fibers anchored to the heart by
fibrous skeleton
fibrous skeleton of the heart
-how many rings
This is a complex framework of dense collagen/fibroblastic tissue forming four fibrous rings that surround the orifices of the valves, a right and left fibrous
trigone (formed by connections between rings), and the membranous parts of the interatrial and interventricular septa.
trigones of the fibrous skeleton do what
Keeps the orifices of the AV and semilunar valves patent and
prevents them from being overly distended
(keep valves open so dont collapse)
function of fibrous skeleton
Provides attachments for the leaflets and cusps of the valves.
Provides attachment (origin and insertion) for the myocardium.
Forms an electrical “insulator” by separating the impulses of the atria and ventricles and by surrounding and providing passage for the initial part of the AV bundle of the conducting system of the heart.
CHART ON SLIDE 29
right side vs left side of myocardial walls
right side: More trabeculated, less muscle mass, thinner
left side: Less trabeculated, more muscle mass, thicker
left side vs right side AV valves
right: Tricuspid (3 leaflets, 3 sets of papillary muscles: anterior, posterior, septal)
left: Mitral/ Bicuspid (2 leaflets, 2 sets of papillary muscles: anterior and posterior)
conduction system on right side (none on left side)
where are the nodes found
SA node and AV nodes are in the right atrium
interatrail septum
Separates the right and left atria
Note: Fossa Ovalis
inter ventricular septum
Separates the right and left ventricles
Inferior: Large, muscular
Superior: Small,
membranous
Corresponds to the anterior and posterior IV sulcus.
auricles
Increase the capacity of the atrium and the volume of blood can be contained.
SA node is the what of the heart
pacemaker
where is SA node located
Located near the opening of the SVC in the RAh
how many impulses/min from SA node (aka HR)
~70
where does contraction signal from SA node go
The contraction signal spreads myogenically in both atria
what is SA node innervated by and inhibited by
Innervated by the sympathetic division of the autonomic nervous system and is inhibited by the parasympathetic division.
where is AV node located
The AV node is located on the floor of the RA (right atrium) near the opening of the coronary sinus, at the junction with IV septum.
what does the AV node connect
Only electrical connection between atria and ventricles (slows it down)
how does the AV node distribute the signal to the ventricles
through the AV bundle (of His)
what speeds up and slows down AV node conduction
SNS speeds up
PNS slows down
the AV bundle passes from the AV node through______
through the fibrous skeleton of the heart and along the membranous part of the IVS.
at the intraventricular septum what happens to the AV bundle
divides
into right and left bundles and form subendocardial branches (Purkinje fibres), which extend into the walls of the respective ventricles.
what stimulates the muscle of the intraventricular septum
The subendocardial branches of the right bundle stimulate the muscle of the IVS, the anterior papillary muscle through the septomarginal trabecula (moderator band), and the wall of the right ventricle
what does the left bundle of AV bundle divide into
divides near its origin into approximately six smaller tracts, which give rise to subendocardial branches that stimulate the IVS, the anterior and posterior papillary muscles, and the wall of the left ventricle.
what artery is the AV node supplies by
AV node is supplied by the AV nodal artery, the largest and usually the first IV septal branch of the posterior IV artery.
hear is supplied by
cardiac plexus (PNS and SNS nerve fibers and visceral afferents for reflexive and nociceptive fibers)
where is cardiac plexus
Located on the anterior surface of the bifurcation of the trachea and at the posterior aspect of the aorta and pulmonary trunk.
where does parasympathetic supply of cardiac plexus come from
presynaptic fibers of vagus nerve
Postsynaptic parasympathetic cell bodies (intrinsic ganglia) are near the SA and AV nodes and along the coronary arteries.
end circulation in the heart
only source of blood supply
microvasculatrure
the endocardium and some of the subendocardial tissue receive oxygen and nutrients through diffusion or microvasculature.
where are vessels embedded in the heart
embeddedinfat and run beneath the epicardium.
Parts of these blood vessels are embedded within the myocardium to ensure the myocardium receives oxygen and nutrients.
blood vessels of the heart are ____ control
autonomic
what supplies the myocardium and epicardium
- Right and left coronary arteries: first branches of the aorta, supply the
where do the coronary arteries arise from
from aortic sinuses, superior to the aortic valve, and pass around opposite sides of the pulmonary trunk.
what do coronary arteries supply
atria and ventricles
right coronary artery
- The right coronary artery (RCA) runs in the coronary/ atrioventricular sulcus.
- Gives an ascending SA nodal brand at its origin.
- Continues in the sulcus and gives the right marginal branch which supplies the right border.
- Turns left, gives posterior interventricular branch, also called the right posterior descending (RPD).
- At the posterior junction of the interatrial and interventricular septum, gives rise to the AV nodal branch.
CHART ON SLIDE 41 for right coronary artery
XXX
left coronary artery
- The left coronary artery
(LCA) arises from the left aortic sinus of the ascending aorta, passes between the left auricle and the left side of the pulmonary trunk, and runs in the AV sulcus. - Splits into 2 branches:
Anterior IV branch (supplies
walls of the ventricles) * Provides a diagonal
branch
Circumflex branch (supplies
walls of LV & LA) - Provides a marginal branch
2 branches of left coronary artery
anterior IV branch and circumflex branch
left coronary artery CHART ON SLIDE 43
XXX
dominance of the coronary arterial system is defined by
which artery gives rise to the posterior interventricular (IV) branch.
cardiac veins empty into
the coronary sinus or into the right atrium.
coronary sinus
main vein of the heart, runs from left to right in the posterior part of the coronary sulcus.
coronary sinus receives
he great cardiac vein (of anterior IV sulcus), middle cardiac vein (of posterior IV sulcus), and small cardiac veins (from the inferior margin).
what opens into the coronary sinus
The left posterior ventricular vein and left marginal vein
cardiac veins
- Thefirstpartofthegreatcardiac vein, the anterior interventricular vein, begins near the apex and runs with the anterior IV artery.
- Atthecoronarysulcus,itturns left, and its second part runs with the circumflex branch of the LCA to reach the coronary sinus.
Note: Blood is flowing in the same direction within a paired artery and vein! - Thegreatcardiacveindrainsthe areas of the heart supplied by the LCA.
- Small and middle cardiac veins drain the right side of the heart.
- The middle cardiac vein (posterior IV vein) accompanies the posterior interventricular arterial branch.
vasculogenesis
development of brand-new blood vessels from mesodermal cells (angioblasts)
angiogenesis
“sprouting” of existing blood vessels formed by vasculogenesis
Connects blood vessels to each other
what week does primitive circulation develop
week 3
how are blood islands formed
Mesenchymal cells –> angioblasts–> blood islands
– begins in extraembryonic mesoderm before intraembryonic mesoderm (umbilical vesicle and allantois)
what happens to angioblasts to form endothelial cells
Angioblasts flatten to form endothelial cells that “coat” the inside of the cavities in the blood island – early endothelium
vasculogenesis and angiogenesis
- The endothelium-lined cavities fuse to form networks of channels = vasculogenesis
- Vessels “sprout” into adjacent areas by endothelial budding and fuse with other vessels = angiogenesis
how do muscular and connective tissues of a blood vessels form
Mesenchyme surrounding the channels develops into the muscular and connective tissue of a blood vessel
3 paired veins drain into the tubular heart in week 4 embryo
Vitelline vein return poorly oxygenated blood from the umbilical vesicle.
o Follow the omphaloenteric duct (former yolk stalk) into the embryo
o They then enter the sinus venosus (venous end of the embryonic heart)
Umbilical vein carry well-oxygenated blood from the chorion to the fetus
Common cardinal veins return poorly oxygenated blood from the body of the embryo
Dorsal aorta – blood to the embryo
Umbilical artery – Returns blood to the placenta
lateral folding brings the heart tube
into the anterior part of the embryo, positioning it within the chest cavity.
cranial folding brings the heart tube
ventrally and caudally
what does intra embryonic coelom near the heart tube develop into
the pericardial cavity, pleural cavity, and peritoneal cavity
when does heart start to beat
day 21
The paired heart tubes are connected with the extra- embryonic vessels once the heart starts to beat on day 21
what do red blood cells develop first in? then in week 5 where are they from?
the extra-embryonic vessels
* Allantois, umbilical vesicle vessels
By the 5th week RBCs arise from the dorsal aorta
what day of gestation does the heart and great vessels begin to form- in which area?
At around 18-19 days of gestation, the heart and great vessels begins to form in a special region of the embryo called the cardiogenic area.
when do the endocardial heart tubes develop and what do they fuse to form?
Paired, longitudinal endothelial-lined channels—the endocardial heart tubes—develop during the 3rd week and fuse to form a primordial heart tube
primary heart field
Earliest region involved in heart development, located in the anterior lateral plate mesoderm.
Gives rise to the initial heart tube, which forms during the third week of development. This tube eventually differentiates into a portion of the atria and the left ventricle.
secondary heart field
Located adjacent to the PHF; visceral mesoderm ventral to the pharynx.
Contributes to the elongation of the heart tube. It forms the right ventricle, the outflow tract of both ventricles (conus cordis and truncus arteriosus), and parts of the atria.
what does the primary and secondary heart field form
primary= atria and left ventricle
secondary= right ventricle, outflow tract for ventricles and parts of atria
neural crest cells
Originate from the neural tube.
Contributes to the cardiac outflow tract and the aorticopulmonary septum.
what do the primary and secondary heart field both exhibit
left- right patterning (laterality)
laterality in the secondary heart field
Cells on the right side contribute to the left of the outflow tract region and those on the left contribute to the right; it explains the spiralling nature of the pulmonary artery and aorta.
when does the cardiac loop form
- As the outflow tract lengthens, the cardiac tube begins to bend on day 23.
- The cephalic portion of the tube bends ventrally, caudally, and to the right; and the atrial (caudal) portion shifts dorsocranially and to the left.
- This bending creates
the cardiac loop by day 28.
cardiac loop
- The atrial portion forms a common atrium and is incorporated into the pericardial cavity.
- The bulbus cordis forms the trabeculated part of the right ventricle. The midportion, the conus cordis, will form the outflow tracts of both ventricles. The distal part of the bulbus, the truncus arteriosus, will form the roots and proximal portion of the aorta and pulmonary artery.
Bulboventricular loop - When looping is completed, the smooth-walled heart tube begins to form primitive trabeculae in two sharply defined areas. The primitive ventricle, which is now trabeculated, is called the primitive left ventricle.
- Likewise, the trabeculated proximal third of the bulbus cordis is called the primitive right ventricle.
the embryonic structure -sinus venosus- becomes what adult stucture
Smooth part of atria, coronary sinus, nodal tissue
the embryonic structure -atrium- becomes what adult stucture
Rough part of the atrium
the embryonic structure -ventricle- becomes what adult stucture
Left ventricle
the embryonic structure -bulbus cordis- becomes what adult stucture
Trabeculated part of the right ventricle, outflow tracts of the ventricles (conus cordis)
the embryonic structure -truncus arteriosus- becomes what adult stucture
Outflow Tract (Pulmonary Trunk & Aorta)
how does blood flow in embryo
Blood flows from the sinus venosus into the primordial atrium, from there to primordial ventricle
Ventricle contracts, pushing blood into the bulbus cordis and truncus arteriosus
o Passes cranially to the pharyngeal arches arteries
o Passes caudally to the dorsal aorta
–>Distributed to the placenta, umbilical vesicle, and the rest of the embryo
when and where do endocardial cushions form
Towards the end of the 4th week, endocardial cushions form on the dorsal and ventral walls of the atrioventricular (AV) canal
As these masses of tissue are invaded by mesenchymal cells during the 5th week, the AV endocardial cushions approach each other and fuse, dividing the AV canal into right and left AV canals
These canals partially separate the primordial atrium from the primordial ventricle, and the endocardial cushions function as AV valves.
what are the endocardial cushion involved in the development of
the atrial and ventricular septa, as well as the atrioventricular valves
where does blood flow in the chambers in the embryo?
- During embryonic life, the blood from all chambers mixes, such that the heart acts like just one massive chamber
- However, the basic structure for separate right- and left-sided circulations must be developed and ready to operate once the child is born
development of partitioning - atria
- Septum primum grows from the roof of the atria towards the endocardial cushions
– The space underneath is called the foramen primum - It meets the endocardial cushions (primordial septum) and abruptly becomes holey and forms another foramen (foramen secundum) – this will remain until birth
he septum secundum now starts to develop, on the right side of the septum primum
* between the two flaps remains the foramen secundum
Note how the development of the septum primum, the septum secundum, and the foramen secundum allow one-way shunting of blood from right to left
* If pressure in the left atrium increases, the valve (formed by what?) will close
atrial septum
- Remnant of septum primum is now called the “valve of the oval foramen”
- Blood flows from the right atrium to the left atrium through the foramen ovale by pushing through the septum primum.
SLIDE 64
