Flashcards in Heart II Deck (49)
What structures flowing into the right atrium have functional valves?
None. The IVC and the coronary sinus have valves, but they are not functional. The SVC does not have a valve
The terminal sulcus indicates the position of what?
the terminal crest, which is located on the inside of the right atrium under the terminal sulcus (the terminal sulcus is a ridge running from the SVC to IVC on the surface of the right atrium)
The smooth-walled portion of the right atrium is referred to as the?
The sinus venarum is the remnant of what?
fetal sinus venosus
What structures enter the sinus venarum?
the SVC and IVC
The crista terminalis (internally, and sulcus terminalis externally) separates the sinus venarum from what part of the right atrium?
the original fetal atrium
The original fetal atrium has what structures associated with it?
ridges called pectinate muscles and also has the ear-like appendage called the auricle.
In utero, what shunts blood from the placenta directly from the right atrium to the left atrium?
foramen ovale (closes after birth)
What causes the foramen ovale to close at birth
pressure of the left atrium becoming higher than the right
What is the remnant of the foramen oval after birth?
the fossa ovalis and limbus of the fossa ovalis
What side of the heart is at higher pressure during development?
right. After birth, right side pressure becomes significantly reduced as the lungs expand, so left side pressure increases in a relative sense
What anchors the tricuspid valve?
Papillary muscles are attached to the edges of the valve leaflets by the chordae tendinae
What are the three cusps of the tricuspid valve?
anterior, posterior, and septal. Each cusp receives chordae tendinae from more than one papillary muscle
The conus arteriosus is aka?
What lines the walls of the right ventricle (not the bulbs cordis part)
trabeculae carneae (The remnants of the bulbus cordis are also smooth-walled)
The septomarginal trabecula is aka?
What is the role of chordae tendinae and papillary muscles?
keeping the valve leaflets of the tricuspid valve from ballooning back into the right atrium, potentially allowing blood to regurgitate
The papillary muscles contract when the ventricles contract
The AV valve leaflets are too thin to function on their own without being anchored at their free border
What marks the boundary between the embryonic ventricle and bulbus cordis?
The supraventricular crest
T or F. The left atrial wall has a smooth surface, except for the auricle, which contains pectinate muscles
What empties into the left atrium?
Four pulmonary veins
What is different about the membranous septum from the rest of the left ventricle?
near the aortic valve the interventricular septum becomes smooth and much thinner than the rest of the ventricular musculature.
has a different embryonic development
where does the left bundle branch of the conducting system passes into the left ventricle?
The pulmonary semilunar valves are designated?
anterior, right and left
The aortic semilunar valve cusps are designated?
right, left, and posterior
What makes semilunar valves more stable than AV valves?
Their semilunar shape. They do not require support from chordae tendinae
What are the parts of semilunar valves and their roles?
Slightly concave sinuses form in the aortic and pulmonary walls behind the cusps. The free edge is formed by a lunula on either side of the centrally placed nodule. The nodule is dense connective tissue, but the lunula is virtually free of connective tissue and composed mainly of two layers of epithelium, making for a tighter fit when the valves close. The lunula of each cusp makes intimate contact with the others and the nodules come together to plug any tendency toward a central deficiency.
the coronary arteries arise from what structure?
What are the names of the mitral valve cusps?
anterior and posterior
What forms the 'skeleton' of the heart?
not formed by bone, but by fibrous rings of connective tissue around the AV valves and around the aortic and pulmonary semilunar valves.
The connective tissue essentially forms an electrical barrier that separates atria and ventricles and to which the muscles from either side attach
Where does a heart beat begin? Why?
SA node, an accumulation of specialized cardiac muscle in the right atrium near the entrance of the SVC
How do SA node cells spread an electrical signal?
they exhibit a spontaneous, rhythmic depolarization that spreads rapidly through the atrial muscles to cause them to contract
NOTE: its rate of depolarization is faster than the spontaneous depolarization that would occur in the AV nodal cells, bundle of His, or Purkinje fibers in the absence of the SA node.
How does depolarization spreads form the SA node into the right and left atria?
interatrial bundles of muscle cells
Depolarization also spreads via the very large numbers of gap junctions between cardiac muscle cells. Gap junctions allow very rapid propagation of the contraction impulse from cell to cell.
Where do internodal bundles run from?
go from SA node to the atrioventricular (AV) node
When the wave of depolarization approaches the AV valves, what happens?
there is a brief pause. If the ventricular muscles weren’t electrically insulated from the atrial muscles by the skeleton of the heart, all four chambers would contract virtually at the same time.
The pause in depolarization is important, but eventually the atrioventricular (AV) node fibers fire
How are electrical signals passed from the AV node to ventricles?
From the AV node, a bundle of fibers, the Bundle of His, passes through a hole in the connective tissue skeleton into the ventricular musculature. At the lower edge of the membranous portion of the interventricular septum, the Bundle of His divides into the right and left bundle branches. The smaller terminal divisions of these bundles in the ventricular wall are called Purkinje fibers.
The cardiac plexus is situated in relation to the aortic arch. A superficial portion of the plexus lies on the anterior surface of the aortic arch and it gets branches mainly from?
the left vagus and left sympathetic trunk
The deep portion receives innervation from right vagus and sympathetics, and also from some left vagus.
What happens in the P phase of an EKG?
What happens in the QRS phase of an EKG?
What happens in the T phase of an EKG?
ventricles repolarize [atrial repolarization is hidden under the much larger ventricular response].
Where is the mitral valve located?
located slightly to the left of the sternum in the 4th intercostal space
Where is the tricuspid valve located?
directly behind sternum at 4th intercostal level
Where can you hear the ASL valve?
right 2nd intercostal space, right sternal border
Where can you hear the PSL valve?
left 2nd intercostal space, left sternal border
Where can you hear the mitral valve?
left 5th intercostal space, mid-clavicular line
Where can you hear the tricuspid valve?
left 5th intercostal space, lower left sternal border
What are AV valves made of?
is a core of collagen fibers covered by an epithelial layer called the endocardium.
What is the nodule of a semilunar valve made of?
What is the lunula of a semilunar valve made of?
two layers of epithelium (no CT)