Cardiovascular System Flashcards
what are the chambers of the heart?
2 receiving chambers: right and left atrium (‘entranceway’)
2 main pumping chambers: the right and left ventricles (‘hollow belly’)
describe the left and right atrium?
receives blood returning from the 2 circuits
describe the left and right ventricles?
pumps blood around the 2 circuits
describe the shape of the heart?
Hollow cone-shaped organ about the size of the fist
typical weight 250-350g
what is the largest organ in the mediastinum?
located between the lungs and oblique position with the apex lying left to the midline
what are the four corners of the heart?
Superior right
Inferior right
Superior left
Inferior left (apex point)
why is the four corners of the heart important?
imaginary lines that connect the 4 corner points delineate the normal size and location of the heart
where is the superior right corner?
at costal cartilage of 3rd rib and sternum
where is the Inferior right corner?
at costal cartilage of 6th rib lateral to the sternum
where is the superior left corner?
at costal cartilage of 2nd rib lateral to the sternum
where is the inferior left (apex point) corner?
lies in the 5th intercostal space at the midclavicular line
what is the pericardium?
a triple-layered sac that encloses the heart
what are the layers of the pericardium? describe them
fibrous and serous pericardium
fibrous pericardium, strong outer layer of dense CT (connective tissue)
serous pericardium, formed from 2 layers: the outer parietal pericardium adheres to the inner surface of the fibrous pericardium and is continuous with the visceral layer or epicardium
what are the coverings of the heart?
pericardium and pericardial cavity
what is the pericardial cavity?
between parietal and visceral layers
what is the function of the pericardial cavity?
- epithelial cells secrete a lubricating serous fluid
- reduce friction between the heart and outer wall of the pericardial sac
what are the three layers of the heart?
Epicardium
Myocardium
endocardium
what is the epicardium?
visceral layer of the serous pericardium (often infiltrated with fat)
what is the myocardium?
forms the bulk of the heart
what is the endocardium?
sheet of endothelium resting on a thin layer of CT
what is the myocardium made of?
consists of cardiac muscle tissue (layer that contracts)
CTs bind the cells into elongated circular and spiral bundles
what is the endocardium made of?
sheet of endothelium resting on a thin layer of CT
- lines the heart chambers and covers the heart valves
what are the bundles of the heart?
Function to squeeze blood through the heart in the proper directions
- inferiorly through the atria
- superiorly through the ventricles
what are the superior chambers?
Right and Left atria
divided longitudinally by the interatrial septum
what are the inferior chambers?
Right and Left ventricles
divided longitudinaly by the interventricular septum
how can you delineate the chambers from the outside?
External boundaries marked by 2 grooves
1) Coronary sulcus forms a crown by circling the boundary between the atria and the ventricles 2) Anterior and posterior interventricular sulci
what is the right atrium?
Forms right border of heart - receives oxygen-poor blood returning from the systemic circuit via veins
what are the names of the veins that receive oxygen poor blood returning from the systemic circuit via veins?
superior and inferior vena cava and the coronary sinus
what are the 2 internal parts of the right atrium?
smooth walled posterior and anterior part lined by pectinate muscles separated by the crista terminalis
what is the crista terminalis?
landmark used to locate sites where veins enter the right atrium
where is the fossa ovalis located?
the right atrium
what is the fossa ovalis?
depression in interatrial septum which is the remnant of the foramen ovale of the fetal heart
the right atrium opens into the right ventricle through the _____?
tricuspid valve (rt. AV valve)
what is the right ventricle?
Forms most of the anterior surface – receives blood from right atrium
what does the right ventricle pump blood into?
pulmonary trunk
what are the internal walls of the right ventricle marked by?
trabeculae carneae (‘little beams of flesh’)
these cone shaped muscles project from the walls of the right ventricle?
papillary muscles
these are thin strong bands from the papillary muscles to the flaps (cusps) of the tricuspid (right AV)?
chordae tendinae
this is found in the right ventricle that has an opening between the right ventricle and the pulmonary trunk?
Pulmonary semilunar valve (pulmonary valve)
what is the left atrium?
Most of the heart’s posterior surface - receives oxygen-rich blood returning from the lungs
- through 2 right and 2 left pulmonary veins
- anteriorly only left auricle is visible
describe the interior atrial wall of the left atrium?
smooth and the pectinate muscles line only the auricle
what does the left atrium open into?
the left ventricle through the mitral valve (left atrioventricular valve)
what is the left ventricle?
Forms the apex of the heart – dominates the inferior surface of the heart
what do the internal walls of the left ventricle contain?
trabeculae carneae, papillary muscles, chordae tendineae, and cusps of an AV (mitral valve)
how does the left ventricle open up?
Superiorly opens into the aorta of the systemic circulation
pumps blood through systemic circuit via the aortic semilunar valve (aortic valve)
describe the path of blood around the circuits?
Beginning with oxygen-poor systemic blood as it arrives at the right side of the heart
superior to the diaphragm enters the rt atrium via the SVC
body regions inferior to the diaphragm enters via the IVC
from heart wall collected by and enters through the coronary sinus
what does the blood pass through from the right atrium to the right ventricle? how is it propelled? how does the right ventricle propel blood?
the tricuspid valve; gravity and right atrium contraction
ventricle contracts propels blood through the pulmonary semilunar valve into the pulmonary trunk and to the lungs through the pulmonary circuit for oxygenation
how does oxygenated blood return to the heart? once there how does it get into the left ventricle?
via the 4 pulmonary veins to the left atrium; passes through the mitral valve to the left ventricle propelled by gravity and left atrium contraction
how does the blood leave the left ventricle?
- delivers oxygen and nutrients to the body tissues through systemic capillaries
- oxygen-poor blood returns through the systemic veins to the right atrium then the cycle continues
T/F, 2 atria always contract together, followed by the simultaneous contraction of the 2 ventricle?
T
what is a heart beat?
Single sequence of atrial contraction followed by ventricular contraction
70 – 80 beats per minute at rest
what is systole?
contraction of a heart chamber
what is diastole?
when a heart chamber relaxes and fills with blood
what do diastole and systole refer to?
the stage of heartbeat when ventricles contract and expand
describe the wall thickness of the atria?
atria are thinner (filling by gravity)
describe the wall thickness of the ventricle?
thicker walls than the right ventricle (pulmonary pump)
T/F, Left ventricle generates more force and pumps blood at a higher pressure
T
is the systemic circuit longer or shorter than the pulmonary circuit? is there more or less resistance to blood flow?
longer; more resistance
how thick is the left ventricle?
Left ventricle – three times thicker than right
Exerts more pumping force and Flattens the right ventricle into a crescent shape
how is one way flow of blood through the heart enforced?
Paired AV and semilunar valves from the atria to the ventricles and into the great arteries that leave the superior part of the heart
how many cusps does each valve consist of? how are the flaps reinforced?
2 or 3 cusps; flaps of endocardium reinforced by cores of dense CT
where are the AV valves?
between atria and ventricles where the right AV is the tricuspid and left AV is the bicuspid (aka mitral)
where are the aortic and pulmonary valves located?
at junction of ventricles and great arteries
where does the fibrous skeleton lie? what is it composed of?
in the plane between the atria and the ventricles and surrounds all 4 heart valves; composed of dense CT
what is the function of the fibrous skeleton?
- Anchors the valve cusps
- Prevents overdilation of valve openings
- Main point of insertion for bundles of cardiac muscle
- Blocks direct spread of electrical impulses from the atria to the ventricles
- critical for proper coordination of atrial and ventricular contractions
describe the function of the AV valves?
blood returning to the heart fills the atria, putting pressure against AV valves; AV valves are forced open
as ventricles fill, the AV valve flap hangs limply into the ventricles
atria contract forcing additional blood into the ventricles
ventricles contract, forcing blood against AV valve cusps
AV valves close
papillary muscles contract and chordae tendinae tighten preventing valve flaps from everting into the atria
additionally
When the ventricles are relaxed, the valves are forced open by the blood pressure exerted on their atrial side
ventricles contract, forcing the contained blood superiorly, and so the valves are pushed shut
describe the function of the semilunar valves?
1) During ventricular contraction, the valves are pushed open, and their cusps are flattened against the artery walls
2) When the ventricles relax, the backflowing blood closes the valves
what is the term used with the Closing of the valves causing vibrations in the adjacent blood and heart walls?
‘lub-dup’ is the sound of valves closing
what is the lub sound?
produced by closing of the AV valves at the start of ventricular systole
what is the dub sound?
produced by the closing semilunar valves at the end of ventricular systole
in terms of heart sounds, how is each valve sound heard best?
near a different heart corner
what forms the thick layer of the cardiac muscle tissue?
contains cardiac muscle cells and CT
how do contractions of the heart cells pump blood through the heart and into blood vessels?
sliding filament mechanism
describe the cardiac muscle cells?
short and branching with 1 or 2 nuclei - striated like skeletal muscle
how are the cells joined?
at intercalated discs – complex junctions that form cellular networks (cardiac fibers)
how are the cells separated?
by endomysium – binds adjacent cardiac fibers and contains blood vessels and nerves
describe the complex junctions of the intercalated discs?
Complex junctions where the sarcolemmas of adjacent cells interlock through meshing ‘fingers’
describe the Transverse regions contain long desmosome like junctions called? what do these bind?
fasciae adherens; bind adjacent cells together and transmit the contractile force
what do longitudinal regions contain?
gap junctions which allow ions to pass between cells, transmitting the contractile signal to adjacent cells
what is the ion that triggers contraction of heart muscle in response to action potential?
by Ca2+ entering the sarcoplasm
rise in intracellular calcium signals the SR to release its stored Ca2+
ions diffuse into the sarcomeres triggering the sliding filament mechanism
are all cardiac cells innervated? if not, then how?
no;
- isolated cardiac cells will still contract rhythmically
- inherent rhythmicity is the basis for rhythmic heartbeat
how do cardiac muscle tissue generate and conduct impulses?
intrinsic ability to generate and conduct impulses these stimulate these same cells to contract rhythmically and do not depend on extrinsic nerve impulses
what is the conducting system of the heart?
- a series of specialized cardiac muscle cells carry impulses throughout the heart musculature
- signals heart chambers to contract and initiating each contraction sequence thereby setting the heart rate
what are the components of the conducting system?
- sinoatrial node, internodal fibers, AV node, AV bundle, right and left bundle branches and subendocardial branches (Purkinje fibers)
Sequence that controls each heartbeat?
first,
atrial contraction followed by ventricular contraction
- SA node – impulses spread along the cardiac fibers of the atria to signal the atria to contract
- some travel along an internodal pathway to the AV node
- At the AV node impulses are delayed for a fraction of a second
- Impulses race through the AV bundle (bundle of His) and enter the interventricular septum and divide
- Right and left bundle branches (crura)
- Purkinje fibers – halfway down the crura become subendocardial branches
