Blood and blood vessels Flashcards
What are the 3 layers of the blood vessel wall?
Tunica intima, Tunica media and Tunica externa/adventitia
What are the 2 components of the Tunica intima?
Squamous Endothelium supported by a basal lamina and sub-endothelial connective tissue
What is the tunica media composed of?
Smooth muscle (some elastic fibres and external elastic lamina)
What is the Tunica externa/adventitia formed from?
Connective tissue
What is the name given to the blood cells that supply the tunica externa/adventitia?
Vasa vesorum
What layer separates the Tunica intima and the Tunica media?
The internal elastic membrane
What layer operates the Tunica media and the Tunica adventitia?
The external elastic membrane
What colours does Verhoeff’s/Mason trichome stain colour the walls of an elastic artery?
Elastic fibres - Black, Collagen - Green, Smooth muscle cells - Red
What adaptation occurs within the largest arteries (e.g. the aorta)?
A large amount of the smooth muscle within the tunica media is replaced my many sheets of elastic fibres to provide elastic recoil
Which layers of the blood vessel wall are supplied by the vasa vasorum?
The tunica adventitia and the furthest parts of the tunica media
What supplies the vasa vasorum with its blood?
The artery itself
What is the typical diameter of an arteriole?
30-200 micrometres
What are the 4 main structures between the small arteriole and the post-capillary venue?
metaarterioles, thoroughfare channels, capillaries and precapillary sphincters
What is the structure and function of the a pre-capillary sphincter?
They are composed of smooth muscle at the beginning of the capillary to help control blood flow through the network
What is the diameter of a capillary?
4-8 micrometres
What type of tissues contain no capillaries?
Epithelial cells resting on the basement membrane, the epidermis of the skin, hair and nails, the cornea of the eye and hyaline cartilage.
How are the epithelial cells resting on the basement membrane supplied?
They diffuse up from the lamina propria
What are the 3 types of capillary?
Continuous, Fenestrated and Discontinuous/Sinusoidal
Where are continuous capillaries found?
Muscle, nerve, lung and skin
What is the average size of the fenestrations within a fenestrated capillary?
50 nanometres
What type of endothelium is found in a continuous capillary?
Continuous epithelium
What are the characteristics of the epithelium of a fenestrated capillary?
They have no breaks, but small fenestrations
What are the characteristics of the epithelium of a sinusoidal capillary?
Breaks between epithelial cells
Where are fenestrated capillaries found?
Gut mucosa, endocrine glands and in the kidneys
Where are discontinuous/sinusoidal capillaries found?
In the liver, spleen and bone marrow
What is the diameter of a post-capillary venule?
10-30 micrometres
What is the structure and function of a post-capillary venule?
They are endothelial cell lined and contain a thin layer of connective tissue. They are important sites of exchange e.g. cells moving into the tissue during inflammation
At what point does a post-capillary venue become a venule?
When they begin to acquire intermittent smooth muscle cells in the tunica media
What are the characteristics of a vein?
They have a Tunica intima, a thin but continuous tunica media, typically consisting of a few layers of smooth muscle cells. There is an obvious Tunica adventitia
What are the characteristics of the Tunica adventitia of a large vein?
It incorporates bundles of longitudinally orientated smooth muscle
How do small veins prevent the back flow of blood?
They have valves which are inward extensions of the Tunica intima
What is the function of the lymph system?
They drain excess tissue fluid into the blood stream and transport lymph to lymph nodes for immunological surveillance
How does the lymph system produce flow?
Though there is no central pump, smooth muscle in the vessel walls, hydrostatic pressure in the tissue and compression of the vessels by voluntary muscle all produce flow
What percentage of the blood is made up of formed elements?
45%
What percentage of the blood is made up of plasma?
55%
What are the 3 main types of formed elements?
Red cells, white cells and platelets