Prac 6 CVRS - Heart

Question 1

What is the Pericardium

Answer 1

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).

Question 2

Two layers of the Pericardium

Answer 2

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).

Question 3

Structure and Function of the Fibrous pericardium

Answer 3

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).

Question 4

Structure of Serous pericardium

Answer 4

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.

Question 5

mesothelium.

Answer 5

Each layer is made up of a single sheet of epithelial cells

Question 6

Pericardial cavity structure and function

Answer 6

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.

Question 7

Fart Police Smell Villains

Answer 7

F – Fibrous layer of the pericardium
P – Parietal layer of the serous pericardium
S – Serous fluid
V – Visceral layer of the serous pericardium

Question 8

How does the pericardium Fix the heart

Answer 8

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

Question 9

How does the pericardium Prevent overfilling

Answer 9

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

Question 10

How does the pericardium Lubrication

Answer 10

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

Question 11

How does the pericardium Protection from infection

Answer 11

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.

Question 12

Myocardium structure

Answer 12

This is composed of branching chains of cardiac myocytes joined end to end by complex junctions called intercalated discs.

Question 13

Similarities and differences between skeletal muscle and myocardium

Answer 13

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.

Question 14

Why are The myocytes of the atria are normally smaller than those of the ventricles

Answer 14

due to differences in resistance and workload.

Question 15

What do atrial myocytes contain?

Answer 15

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.

Question 16

What does atrial natriuretic peptide do

Answer 16

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.

Question 17

What do intercalated discs contain and do

Answer 17

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.

Question 18

Describe the structures of the SAN and AVN

Answer 18

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.

Question 19

The S.A. node is located?

Answer 19

on the medial side of the superior vena cava at its junction with the right atrium.

Question 20

A.V. node is located

Answer 20

at the base of the inter-atrial septum, anterior to the opening of the cardiac sinus.

Question 21

What and where at the Purkinje fibers?

Answer 21

These are large modified muscle fibres lying mostly just beneath the endocardium in the interventricular septum.

Question 22

Why don’t purkinje fibres appear with H&E

Answer 22

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.

Question 23

General Structure of valves

Answer 23

They consist of thick collagen fibres with occasional strands of elastic tissue. Both surfaces are covered by a layer of endothelial cells.

Question 24

How are the atrio-ventricular and mitral valves connected to papillary muscles

Answer 24

by fibrous chordae tendinae

Question 25

Which the outermost layer of the heart?

Answer 25

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.)

Question 26

What type of epithelium is the pericardium

Answer 26

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.

Question 27

Structure of cardiac myoctyes

Answer 27

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).

Question 28

Where are purkinje fibres found

Answer 28

They are found immediately below the endocardium.

Question 29

How do the myocytes of the sinoatrial node differ from normal cardiac myocytes

Answer 29

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.

Question 30

Which cell type lines the mitral valve?

Answer 30

Endothelial

Question 31

What other heart features are lines by endothelial cells?

Answer 31

The inner surface of the heart, including the surface of the cardiac valves, is lined by vascular endothelial cells

Question 32

Where in the heart will you find the nodules of Arantius

Answer 32

Aortic valve cusps

Question 33

What are the nodules of arantius

Answer 33

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).

Question 34

What yellow/brown pigment accumulates in cardiac myocytes with increasing age?

Answer 34

Lipofuscin

Question 35

What is lipofuscin and how is it formed

Answer 35

Lipofuscin is a ‘wear and tear’ pigment formed by peroxidation of membrane lipids. It accumulates in cardiac myocytes with advancing age.

Question 36

Pericytes are associated with

Answer 36

capillaries and venules

Question 37

Where do the coronary arteries run

Answer 37

The coronary arteries are medium-sized muscular arteries that run in the epicardium. They do have an external elastic lamina.

Question 38

what are Weibel-Palade bodies and where are they found

Answer 38

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.

Question 39

Almost all tissues have lymphatics, except

Answer 39

cartilage, the eye, bone marrow and perhaps spinal cord.