Histology of Blood Vessels Flashcards
What are the 3 blood circulatory systems?
- Systemic
- Pulmonary
- Portal
What are the 3 concentric layers of a blood vessel?
- Tunica intima = lining of squamous cells supoorted by connective tissue and bounded by an internal elastic lamina
- Tunica media = smooth muscle cells, some collagen and elastin
- Tunica adventitia = supporting layer of dense, fibroelastic connective tissue
Give some examples of elastic arteries
Aorta, common carotid, subclavian and pulmonary arteries
Describe each of the tunica layer in elastic arteries
Intima = single layer of endothelial cells, rich in elastin, contains fibroblasts Media = concentric fenestrated sheets of elastin, separated by collagen and smooth muscle cells Adventita = collagenous connective tissue containing vasa vasorum
Give some properties of muscular arteries
- thin tunica intima
- tunica media made of smooth muscle cells to withstand pressure
- internal and external elastin lamina
- contraction stimulated by sympathetic nerves
What is the equation for viscous resistance to flow?
constant / radius ^ 4
Explain the process of microcirculation
- part of the circulatory system concerned with exchange of gases, nutrients and waste products
- exchange occurs mainly in capillaries
- capillaries drain into venules
- blood flow into the capillary bed is controlled by arterioles and sphincters
What are the 3 types of capillaries?
continuous, fenestrated, discontinuous
Describe continuous capillaries
- tube of endothelial cells linked by a tight junction
- embraced by pericytes which are important for survival and stabilisation of endothelial cells
- some small molecules can diffuse through the endothelial cells
- permeability to large molecules depends on the tightness of the junction
- transport of large molecules involves transcytosis across endothelial cell
Where does transcytosis occur? Explain the process that this occurs
Various macromolecules are transported across the interior of the cell.
Flask - like pits called caveolae bud of vesicles which cross the cell and fuse with caveolae on the opposite face of the endothelial cell.
Explain the structure of a fenestrated capillary
Found at sites where there is rapid movement of macromolecules into or out the blood system.
Luminal and basal plasma membranes of endothelial cells come together to form fenestrae.
Fenestrations are usually closed by a diaphragm. Basal lamina is continuous across the fenestrations.
Explain where discontinuous endothelium is found. What does it allow you to do?
Sinusoids of liver and spleen.
Large gaps between the endothelial cells.
Basal Lamina is discontinuous also.
Allows for free passage of large macromolecules or even red blood cells in the spleen.
What is the main site for the entry and exit of white blood cells and why?
Post - capillary venule due to the presence of seals.
Postcapillary venules unite to form collecting venules.
Collecting venules drain into muscular venules.
What are veins formed from?
Explain each of the 3 tunica layers in a vein.
How can you tell a vein from an artery?
Formed from the union of muscular venules.
Intima - few more layers than the endothelium
Media - 2 or more layers of smooth muscle cells
Adventitia - broadest layer
Can tell a vein from an artery as a vein has a wider lumen compared to smooth muscle.
Low pressure collecting system for return of blood from —- to the heart. Blood flow is passive and assisted by — pressure within the chest during inspiration. Return of blood from the limbs aided by muscular —-.
Capillaries
Negative
Contraction