How Is Blood Circulation Regulated Flashcards
Tunica intima
- endothelium.
- basement membrane.
- lamina propria (CT layer).
- internal elastic membrane (gene strayed layer of elastic fibers.
Tunica media
- smooth muscle cell bodies arranged circularly around the blood vessel.
- vasoconstriction and dilation (smooth muscle control).
Tunica externa (adventitia)
- connective tissue.
- varies from dense regular near the vessel to loose that merges with the surrounding C.T.
Elastic artery characteristics and examples
- elastic tissue.
- expand and recoil.
- are pressure reservoirs.
- conducting arteries.
- e.g. Aorta and major branches.
Muscular arteries characteristics and examples
- thick walls: 25+ layers of muscle.
- undergo vasoconstriction and vasodilation.
- distributing arteries.
- e.g. Medium size arteries.
Arteriole characteristics and examples
- decreasing in size with gradual loss of wall layers down to terminal arterioles.
- e.g. Small muscular arteries.
Venules
- Very small veins that drain capillary network.
- as diameter of venules increases, amount of smooth muscle increases.
- endothelial cells and basement membrane with a few smooth muscle cells.
Characteristics of veins
- smooth muscle cells form continuous layer: addition of tunica adventitia.
- have valves.
- thin wall and large lumens.
- are very compliant: 24x more than arteries.
What are capacitance vessels of the circulation
-veins: hold a lot of blood at very low pressure.
Capillary characteristics
- endothelial cells sitting on a basement membrane and delicate layer of loose connective tissue.
- for rapid exchange of nutrients and metabolites between blood and interstitial fluid.
What are the three types of capillaries
- continuous.
- fenestrated.
- sinusoids.
Continuous capillary characteristics and examples
No gaps between endothelial cells e.g. Muscle, skin.
Fenestrated capillary characteristics and examples
Highly permeable e.g. Kidney, endocrine glands.
Sinuoid capillary characteristics and examples
Large diameter and large fenestrae e.g. Liver, bone marrow, spleen.
What controls blood flow between the capillaries?
Controlled by the opening and closing of pre-capillary sphincters.
What does blood flow through capillary beds depend on?
Metabolic activity of the tissue.
What are arteriovenous anastomoses?
The connecting vessels through which blood can bypass capillaries and flow directly into post-capillary venules.
What are capillary beds?
The functional areas of the circulation where fluid, nutrient and metabolic exchange occurs between the blood, interstitial fluid and the cells.
What is filtration out?
Fluid exchange at the arteriolar end of a capillary: ~30L/day.
What is reabsorption in?
Fluid exchange at the venous end: ~27L/day.
Where are any excess filtered fluid and leaked proteins from the capillaries drained?
Into lymphatic capillaries which return lymph to the blood: ~3L/day.
Movement of capillary fluid when there is: positive filtration pressure?
Fluid moves out of capillary (net hydrostatic pressure>net osmotic pressure).
Movement of capillary fluid when there is: negative filtration pressure?
Fluid moves in to capillary (net hydrostatic pressure < net osmotic pressure).
What percentage of blood volume is in blood vessels at any given time? (In the systemic circulation)
84% (64% in veins, 13% arteries, 7% capillaries).