Histology Of The Heart Flashcards
What are the 3 layers of the heart then pericardium layers
1.) endocardium: inner
2.) myocardium: middle layer
3.) epicardium:outer layer
4.) visceral layer of serous pericardium
5.) pericardial cavity
6.) parietal layer of serous pericardium
7.) fibrous pericardium
8.) adipose tissue
What does the endocardium line and what is its structure?
Lines entire inner surface of heart, including valves
Structure:
- endothelium
- basal lamina
- thin layer of collagen fibres
- layer of denser connective tissue
- some areas also have a subdenocardium of loose connective tissue containing small blood vessels and nerves and the branches of the impulse conducting system
What is the myocardium’s (thick middle layer) structures?
- Bundles and layers of contractile cardiac muscle
- individual muscle fibres are surrounded by delicate, collagenous connective tissue with a rich network of capillaries
-the cardiac muscle cells have a single central nucleus and intercerlated discs passing across the fibres at irregular intervals
What’s the epicardium (outer layer) structure (visceral layer of the serous pericardium)?
- on the surface of the heart: a single layer of flattened epithelium calles mesothelium
- basal lamina
- fibroblastic connective tissue and, in some places, adipose tissue
What are the parts and structure of the pericardium?
- fibrous pericardium: sac of tough fibrocollagenous connective tissue
-serous pericardium: made of a layer of simple squamous epithelium (mesothelium), backed by basal lamina and connective tissue. The serous pericardium lines the inner surface of the fibrous pericardium (where it is called parietal serous pericardium), and also covers the surface of the heart (where it is called the visceral serous pericardium)
These two mesothelium layers are separated by a thin pericardial cavity which contain a small amount (15-50ml) of pericardial fluid - providing lubrication for heart movement
What is the structure and function of the fibrous ‘skeleton’ of the heart
This fibrous ‘skeleton’ formed by thick bands of fibrous connective tissue is situated around the heart valves, between the atria and between the ventricles.
Use:
-Supports the valves
-Provides attachment for the cardiac muscle fibres
Structure of heart valves?
-Outer endothelial layer with basal lamina
-Layer of collagen and elastin fibres
-Core of dense connective tissue, called lamina fibrosa, that is continuous with the fibrous skeleton
-The leaflets of the AV valves are anchored to papillary muscles in the wall of the ventricle by collagenous strands called the chordate tendineae, which merge with the lamina fibrosa (core of the heart valve)
-No blood vessels in valves
What are the 3 types of cardiac muscle cells
Contractile cells (99%)
Pacemaker cells
Conducting cells
What cells make the SA node?
Pacemaker cells which are highly specified muscle cells
Describe the route of electrical conduction from the junction of the atria and ventricles
At the junction of the atria and ventricles, the depolarisation is picked up by the atrio-ventricular node and after a delay, conducted rapidly down the interventricular septum via the atrioventricular bundle. As it descends it produces left and right bundle branches. When these fibres reach the apex they turn upwards. The conducting system activates and contracts the network of Purkinje fibres beneath the endocardium of the ventricles
At this point the fibrous skeleton electrically isolated the atria from the ventricles
Where are purkinje fibres found?
Found in the subendothelial layer just deep to the endocardium
What do pukrkinje fibres do?
Distribute the excitatory activity such that the ventricular contraction generally occurs from the inferior to superior
What is the basic role of the lymph vascular system
Consists of lymphatic vessels that drain tissue fluid (lymph), eventually returning it to the veins in the base of the neck
How does lymphatic vessels move the lymph e.g. to lymph nodes for immunological surveillance
Smooth muscle in walls, hydrostatic pressure in the tissue and compression of the vessels by voluntary muscle, combined with valves to produce flow
