Histology of the heart and blood vessels Flashcards
What are the 3 layers of the blood vessels?
Tunica intima
Tunica media
Tunica adventitia
What makes up the tunica intima?
Squamous epithelium termed the endothelium which is supported by the basal lamina (Connective tissue)
What makes up the tunica media?
Smooth muscle and some elastic fibres
What makes up the tunica adventitia?
Supporting connective tissue
What is found between the tunica intima and tunica media?
The internal elastic membrane
What is found between the tunica media and tunica adventitia?
The external elastic membrane
Which vessels contain smooth muscle in their tunica adventitia?
Veins
Which vessels have the thickest tunica media?
Arteries
Which vessels have the thickest tunica adventitia?
Veins
What are vasa vasorum?
Blood vessels that branch from the main artery and move into the tunica adventitia in order to supply the outer most layers of the blood vessels with oxygen and nutrients
How many layers of smooth muscle is found in the tunica media of an arteriole?
1 to 2 layers
What are the characteristics of a meta-arteriole?
In meta-arterioles, the smooth muscle is replaced by discontinuous, non contractile cells called pericytes
What forms the walls of a capillary?
Endothelial cells and a basal lamina only, with pericytes at intervals
What are the 3 types of capillary?
Continuous
Fenestrated
Discontinuous/sinusoidal
Where are continuous capillaries found?
Connective tissue, muscle, lungs, skin and nerves
Where are fenestrated capillaries found?
Gut mucosa, endocrine glands and glomeruli
Where are discontinuous/sinusoidal capillaries found?
Liver, spleen and bone marrow
What are the characteristics of a fenestrated capillary?
Have occasional ~50mm pores in their walls
What are the characteristics of a discontinuous/sinusoidal capillary?
They lack a basal lamina and have large gaps, allowing macro molecules to pass through
What structures form the network between small arterioles and post capillary venules?
Meta-arterioles
Thoroughfare channels
Capillaries
Pre-capillary sphincters
What are the characteristics of a post capillary venule?
They are endothelial cell-lined and contain a thin layer of connective tissue and some pericytes
What is the difference between a post-cappilary venule and venule?
Venules form when post-capillary venules begin to acquire intermittent smooth muscle cells
What is different about the veins of the scalp?
They have no valves
What are the 3 layers of the heart wall?
Endocardium - Inner
Myocardium - Middle
Epicardium - Outer
What are the layers of the endocardium?
Endothelium
Basal lamina
Thin layer of collagen fibres
Layer of dense connective tissue
Some areas of sub endothelium containing loose connective tissue, small blood vessels and nerves
Describe the histology of the myocardium
Bundles and layers of contractile cardiac muscle
Individual muscle fibres, surrounded by delicate collagenous connective tissue and a network of capillaries
What are the characteristics of a cardiac muscle cell?
Single, central nucleus
Intercalated discs containing desmosomes, adherent junctions and gap junctions
What are the layers of the epicardium?
Mesothelium - single layer of flattened epithelium
Basal lamina
Fibroelastic connective tissue
Adipose tissue
What forms the fibrous pericardium?
Tough, fibrocollagenous connective tissue
What forms the serous pericardium?
A layer of simple epithelium (Mesothelium), backed by a basal lamina and connective tissue
What is the fibrous skeleton?
A supportive skeleton made up of bands of fibrous connective tissue around the heart valves, between the atria and between the ventricles
This supports the valves and provides attachment for muscle fibres
What is the structure of a heart valve?
They have an outer endothelial layer supported by a basal lamina
They also have a core of dense connective tissue called the lamina fibrosa which is in continuation with the fibrous skeleton
How do lymphatic capillaries begin?
Lymphatic capillaries begin as blind sacs
