Histo Block I: Heart Flashcards
Why are valves present in the heart?
Valves are present at the exits from the chambers to prevent backflow of blood
what is the 2-stage dual pump?
the right atrium and right ventricle receiving returning blood from the body via the inferior & superior vena cava and pumping this blood to the lungs for oxygenation (pulmonary circulation). And the left atrium and left ventricle receiving the returning blood from the lungs via the 4 pulmonary trunks and pumping it into the aorta for distribution throughout the body (systemic circulation)
the heart consisting of the atria and ventricles can be consideres to be a modified ________ _________
blood vessel
what are the 3 layers of the wall of the heart?
- epicardium (on outside)
- myocardium (in middle)
- endocardium (lining of heart interior)
identify
Micrograph of left atrial and ventricular walls
identify
Heart valve and endocardium
describe the epicardium
The epicardium consists of a layer of simple squamous mesothelial cells on the outer surface of the heart and the connective tissue underlying the mesothelium.
identify
mesothelial layer of surface of ovary
what is the function of mesothelium?
The mesothelium secretes a fluid that lubricates the space between the visceral and parietal layers of the pericardial sac.
how is the epicardium in the atrium vs ventricle
The epicardium representing the visceral layer of the pericardial sac is thicker on the atrium than the ventricle.
in which layer of the heart do blood vessels )coronary vessels) and nerves which supply the heart, lie?
epicardium
Whta tissue can be find in the loos CT of the epicardium?
Adipose tissue particularly in the portion covering the atria, acting as cushion for movement of the heart in the pericardial sac.
identify
Micrograph of left atrial and ventricular walls
describe the cell layer of the endocardium
The endocardium lines the inner surface of the heart and consists of an endothelial layer with a relatively thick region of CT below it
identify
endocardium
describe the layer of the endocardium
- A surface layer of simple squamous endothelial cells and their associated basal lamina and subendothelial CT
- A middle layer of CT with elastic fibers and smooth muscle cells
- A deeper layer of CT called the subendocardial layer which is continuous with the CT of the myocardium.
identify
Endocardium without Purkinje fibers; elastic stain
identify
Endocardium with Purkinje fibers
Where does the impulse conducting system of the heart lie?
lies in the subendocardial layer of the endocardium
Which layer of the wall of the heart is the thickest?
myocardium and consists of cardiac muscles cells
describe the myocardium of the ventricle vs atria
The myocardium of the ventricle is much thicker than in the atria
how are the cells in the ventricle and how does this relate to its function?
The ventricle is characterized by larger diameter cardiac cells and bundles than are present in the atria, consistent with its function as a contractile pump vs. the atria which produce much less contractile force.
identify
myocardium of atrium vs ventricle
identify
cardiac muscle
what are atrial granules and where can we find theM?
present in atrial cells and are membrane-limited granules 0.2-0.3 microns diameter. Most common in the cardiac muscle cells of right atrium
what hormones is present in atrial granules?
They contain precursor of hormone - atrial natriuretic factor (auriculin, atriopeptin) and brain natriuretic factor
how are hormones in the atrial granules release and what is the main function?
The hormones are released upon stretching of the atrial cells by high blood pressure and act on kidney to increase the excretion of sodium and water from the proto-urine thus lowering blood pressure. Thus the atrial cells can play a role in regulating blood pressure
identify
Atrial granules inn cardiac muscle
What does the fibrous skeleton of the heart consists of?
dense irregular CT
What does the fibrous skeleton form?
- 4 fibrous rings which surround the valve orifices
- The left and right fibrous trigone regions connecting the fibrous rings
- The membranous parts of the interventricular and interatrial septa
What are the functions of the fibrous skeleton?
- The fibrous skeleton provides strength to the base of the aorta and pulmonary trunk arteries leaving the heart, and to the openings between the atria and ventricles.
- The fibrous rings also act as strong attachment points for the valves.
- The fibrous skeleton also provides electrical isolation between the atrial and ventricular myocardium. This allows the atria to contract first and move the blood into the ventricle prior to contraction of the ventricle.