histology of the heart

Question 1

what are the 3 layers of the heart

Answer 1

Endocardium: inner layer

Myocardium: middle layer

Epicardium: outer layer

Question 2

describe the endocardium

Answer 2

Lines the entire surface of the heart, including the valves

Question 3

what is the endocardium composed of

Answer 3

an endothelium, a basal lamina, a thin layer of collagen fibres and a layer of denser connective tissue

Question 4

what is a subendocardium -

Answer 4

loose connective tissue which contains small blood vessels, nerves, and branches of the impulse conducting system

Question 5

what is the myocardium composed of

Answer 5

Bundles and layers of contractile cardiac muscle fires

Question 6

in the myocardium what are individual muscle fibres surrounded by

Answer 6

delicate, collagenous connective tissue with a rich capillary network

Question 7

what does the Intercalated dics attaching cardiac myocytes allow

Answer 7

the spread of electrical activity

Question 8

what sort of nucleus do cardiac muscles have

Answer 8

single central nucleuses

Question 9

what is the epicardium composed of

Answer 9

connective tissue and fat, lined on outer surface by simple squamous epithelial cells (mesothelium)

Question 10

what forms the epicardium

Answer 10

the visceral layer of the pericardium

Question 11

what are Fibroserous

Answer 11

fluid filled sac that surrounds the muscular body of the heart and the roots of the great vessels

Question 12

fibrous pericardium

Answer 12

Continuous with the central tendon of the diaphragm, made of tough fibrocollagenous connective tissue

Question 13

what is the serous pericardium composed of

Answer 13

a layer of mesothelium, backed by a basal lamina and connective tissue

Question 14

Parietal serous pericardium:

Answer 14

lines inner surface of fibrous pericardium

Question 15

Pericardial cavity:

Answer 15

separates two layers of serous pericardium, contains pericardial fluid which provides lubrication for heart movement

Question 16

Visceral serous pericardium:

Answer 16

covers the surface of the heart (also known as the epicardium)

Question 17

what is the fibrous ‘skeleton’ of the heart formed from

Answer 17

thick bands of fibrous connective tissue around the heart valves, between the atria, and between the ventricles

Question 18

what does the fibrous ‘skeleton’ of the heart do

Answer 18

Supports the valves and provides attachment for cardiac muscle fibres

Question 19

what is the lamina fibrosa

Answer 19

the core of a heart valve and is dense irregular connective tissue that is continuous with the fibrous skeleton of the heart

Question 20

what are the 3 types of cardiac muscle cells

Answer 20

Contractile cells, Pacemaker cells, Conducting cells

Question 21

what are pacemaker cells

Answer 21

they are Considerably smaller than contractile cardiac myocytes and are embedded in a more extensive matrix of connective tissue

Question 22

how do pacemaker cells appear

Answer 22

• Appear pale histologically (P Cells)
• few organelles
• Few myofibrils, little glycogen and no proper T-tubule system

Question 23

describe Conducting cells - Purkinje fibres

Answer 23

• Larger than normal cardiac muscle cells
• Appear pale histologically with a very pale centre

Have abundant glycogen, no T-tubules, no intercalated discs

Actin and myosin filaments are sparse and tend to be found in the cell periphery

• Distribute excitatory activity so that ventricular contraction generally occurs from inferior to superior

Question 24

where are conducting cells found

Answer 24

• Found in the subendocardial layer just deep to the endocardium