Prac 6 CVRS - Heart Flashcards
What is the Pericardium
is a fibroserous, fluid-filled sack that surrounds the muscular body of the heart and the roots of the great vessels (the aorta, pulmonary artery, pulmonary veins, and the superior and inferior vena cavae).
Two layers of the Pericardium
a tough external layer known as the fibrous pericardium, and a thin, internal layer known as the serous pericardium (to overextend the orange metaphor, the outer peel could be thought of as the fibrous layer, with the inner white stuff being the serous layer).
Structure and Function of the Fibrous pericardium
Continuous with the central tendon of the diaphragm, the fibrous pericardium is made of tough connective tissue and is relatively non-distensible. Its rigid structure prevents rapid overfilling of the heart, but can contribute to serious clinical consequences (see cardiac tamponade).
Structure of Serous pericardium
Enclosed within the fibrous pericardium, the serous pericardium is itself divided into two layers: the outer parietal layer that lines the internal surface of the fibrous pericardium and the internal visceral layer that forms the outer layer of the heart (also known as the epicardium). Each layer is made up of a single sheet of epithelial cells, known as mesothelium.
mesothelium.
Each layer is made up of a single sheet of epithelial cells
Pericardial cavity structure and function
Found between the outer and inner serous layers. contains a small amount of lubricating serous fluid. The serous fluid serves to minimize the friction generated by the heart as it contracts.
Fart Police Smell Villains
F – Fibrous layer of the pericardium
P – Parietal layer of the serous pericardium
S – Serous fluid
V – Visceral layer of the serous pericardium
How does the pericardium Fix the heart
in the mediastinum and limits its motion. Fixation of the heart is possible because the pericardium is attached to the diaphragm, the sternum, and the tunica adventitia (outer layer) of the great vessels
How does the pericardium Prevent overfilling
The relatively inextensible fibrous layer of the pericardium prevents the heart from increasing in size too rapidly, thus placing a physical limit on the potential size of the organ
How does the pericardium Lubrication
A thin film of fluid between the two layers of the serous pericardium reduces the friction generated by the heart as it moves within the thoracic cavity
How does the pericardium Protection from infection
The fibrous pericardium serves as a physical barrier between the muscular body of the heart and adjacent organs prone to infection, such as the lungs.
Myocardium structure
This is composed of branching chains of cardiac myocytes joined end to end by complex junctions called intercalated discs.
Similarities and differences between skeletal muscle and myocardium
Like voluntary (skeletal muscle) these cells contain myofibrils with repeat sarcomeres that give rise to visible striations. Unlike voluntary muscle, the cells remain separate and do not form a syncitium. Each has its own nucleus placed centrally within the cell. Unlike voluntary muscle the fibres branch giving a characteristic appearance.
Why are The myocytes of the atria are normally smaller than those of the ventricles
due to differences in resistance and workload.
What do atrial myocytes contain?
Atrial myocytes, especially those of the right atrium contain small secretion granules close to their nucleus. These contain atrial natriuretic peptide (ANP), a hormone that is released when the cells are stretched excessively.
What does atrial natriuretic peptide do
This hormone increases the excretion of water and sodium and potassium ions by the kidney. It also inhibits renin secretion causing a lowering of blood pressure.
What do intercalated discs contain and do
Individual myocytes are joined together by intercalated discs.
These complex junctions contain desmosomes and adherent junctions that bind the cells together.
They also contain gap junctions that allow the cells to become electrically coupled.
Describe the structures of the SAN and AVN
These nodes are composed of very small, irregularly arranged myocytes adapted for impulse conduction rather than contraction. They are surrounded by numerous blood vessels and nerve plexuses.
The S.A. node is located?
on the medial side of the superior vena cava at its junction with the right atrium.
A.V. node is located
at the base of the inter-atrial septum, anterior to the opening of the cardiac sinus.
What and where at the Purkinje fibers?
These are large modified muscle fibres lying mostly just beneath the endocardium in the interventricular septum.
Why don’t purkinje fibres appear with H&E
The cells have large vacuoles but have few myofibrils.
They contain stores of glycogen that allows them to be easily visualised with the PAS staining procedure.
General Structure of valves
They consist of thick collagen fibres with occasional strands of elastic tissue. Both surfaces are covered by a layer of endothelial cells.
How are the atrio-ventricular and mitral valves connected to papillary muscles
by fibrous chordae tendinae
Which the outermost layer of the heart?
Visceral pericardium
From the outside, the layers of the heart are the (visceral) pericardium, epicardium, myocardium and endocardium. The parietal pericardium is a fibrous sac that contains the heart. (The cells lining the visceral and parietal layers of the pericardium are the same.)
What type of epithelium is the pericardium
The pericardial epithelium is a simple squamous epithelium. Because of its embryological derivation it is known as mesothelium. This is the same epithelium found in the pleura and peritoneum.
Structure of cardiac myoctyes
Cardiac myocytes are branching cells each with a single nucleus. They do not form from the fusion multiple myoblasts (that is skeletal muscle). Their myofibrils are in register, and so they appear striated. Atrial myocytes (but not those in the ventricles) secrete a hormone (atrial natriuretic peptide).
Where are purkinje fibres found
They are found immediately below the endocardium.
How do the myocytes of the sinoatrial node differ from normal cardiac myocytes
Have no intercalated discs
The myocytes of the SAN are smaller than regular cardiac myocytes. Although they are joined by desmosomes, they do not have intercalated discs. The are embedded in fibrous connective tissue. All cardiac myocytes have a nucleus and mitochondria.
Which cell type lines the mitral valve?
Endothelial
What other heart features are lines by endothelial cells?
The inner surface of the heart, including the surface of the cardiac valves, is lined by vascular endothelial cells
Where in the heart will you find the nodules of Arantius
Aortic valve cusps
What are the nodules of arantius
The nodules of Arantius are nodules of fibroelastic tissue on the centre of the free edge of each of the valve cusps in the aortic valve and pulmonary valve. They are more prominent in the aortic valve (due to increased pressure in that side of the circulation).
What yellow/brown pigment accumulates in cardiac myocytes with increasing age?
Lipofuscin
What is lipofuscin and how is it formed
Lipofuscin is a ‘wear and tear’ pigment formed by peroxidation of membrane lipids. It accumulates in cardiac myocytes with advancing age.
Pericytes are associated with
capillaries and venules
Where do the coronary arteries run
The coronary arteries are medium-sized muscular arteries that run in the epicardium. They do have an external elastic lamina.
what are Weibel-Palade bodies and where are they found
Weibel-Palade bodies are storage granules found within the cytoplasm of endothelial cells (in the heart and elsewhere). They contain von Willebrand factor and other vascular mediators.
Almost all tissues have lymphatics, except
cartilage, the eye, bone marrow and perhaps spinal cord.
