histology of the heart Flashcards
what are the 3 layers of the heart
Endocardium: inner layer
Myocardium: middle layer
Epicardium: outer layer
describe the endocardium
Lines the entire surface of the heart, including the valves
what is the endocardium composed of
an endothelium, a basal lamina, a thin layer of collagen fibres and a layer of denser connective tissue
what is a subendocardium -
loose connective tissue which contains small blood vessels, nerves, and branches of the impulse conducting system
what is the myocardium composed of
Bundles and layers of contractile cardiac muscle fires
in the myocardium what are individual muscle fibres surrounded by
delicate, collagenous connective tissue with a rich capillary network
what does the Intercalated dics attaching cardiac myocytes allow
the spread of electrical activity
what sort of nucleus do cardiac muscles have
single central nucleuses
what is the epicardium composed of
connective tissue and fat, lined on outer surface by simple squamous epithelial cells (mesothelium)
what forms the epicardium
the visceral layer of the pericardium
what are Fibroserous
fluid filled sac that surrounds the muscular body of the heart and the roots of the great vessels
fibrous pericardium
Continuous with the central tendon of the diaphragm, made of tough fibrocollagenous connective tissue
what is the serous pericardium composed of
a layer of mesothelium, backed by a basal lamina and connective tissue
Parietal serous pericardium:
lines inner surface of fibrous pericardium
Pericardial cavity:
separates two layers of serous pericardium, contains pericardial fluid which provides lubrication for heart movement
Visceral serous pericardium:
covers the surface of the heart (also known as the epicardium)
what is the fibrous ‘skeleton’ of the heart formed from
thick bands of fibrous connective tissue around the heart valves, between the atria, and between the ventricles
what does the fibrous ‘skeleton’ of the heart do
Supports the valves and provides attachment for cardiac muscle fibres
what is the lamina fibrosa
the core of a heart valve and is dense irregular connective tissue that is continuous with the fibrous skeleton of the heart
what are the 3 types of cardiac muscle cells
Contractile cells, Pacemaker cells, Conducting cells
what are pacemaker cells
they are Considerably smaller than contractile cardiac myocytes and are embedded in a more extensive matrix of connective tissue
how do pacemaker cells appear
- Appear pale histologically (P Cells)
- few organelles
- Few myofibrils, little glycogen and no proper T-tubule system
describe Conducting cells - Purkinje fibres
- 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
where are conducting cells found
- Found in the subendocardial layer just deep to the endocardium
