Blood Vessels Flashcards
Where does the intracellular and extracellular fluid lie?
Describe the pressure at the arterial end of capillary beds
What does it favour?
- Relatively high hydrostatic, relatively low oncotic capillary pressure
- favours filtration (delivery)
Describe the pressure at the venous end of capillary beds
What does it favour?
- Relatively low hydrostatic, high oncotic capillary pressure
- Favours reabsorption
What are the 4 Starling forces?
- Capillary hydrostatic pressure (filtration)
- Plasma colloid osmotic pressure (reabsorption)
- Interstitial hydrostatic (reabsorption)
- Except in lungs due to lymphatics
- Interstitial colloid osmotic (filtration)
What are the 3 layers of blood vessel?
- Tunica intima
- Tunica media
- Tunica adventitia
What is found in the tunica intima?
- Thin endothelial layer
- Few SM fibres
What is found in the tunica media?
- Very thick layer of a lot of smooth muscle cells
- Abundant extracellular matrix- collagen, proteoglycans, elastin
What is found in the tunica adventitia?
- CT, fibroblasts, mast cells etc.
- Nerves
- Blood vessels - vasa vasorum
What does stimulation of Alpha1 adrenergic receptors cause
Vasoconstriction
On what vessels are Beta 1 and 2 receptors located?
On the smooth muscle segments of coronary vessels
What does stimulation of B1 and 2 AR cause
vasodilation
What is an Aneurysm?
Excessive localised swelling of the artery
What are the 3 types of Aneurysms?
What are the 2 types of arteries?
- Elastic (closest to heart)
- Muscular
What is the significant feature of elastic arteries and what are 3 resulting functions?
- High amounts of elastin
1. Withstand the pressure of ejection from the ventricles → hence prevents over expansion
2. Helps buffer the pulsatile ejection of blood from the heart so it has a more even flow
3. The elastic recoil also helps move blood forward into the rest of the circulatory system
SM oposes stretch to maintain integrity
Muscular arteries are vasoactive
What does this mean?
Means they are capable of:
- Vasodilation (through beta1 adrenergic receptors)
- Vasoconstriction (through smooth muscle bracelet contraction).
This helps modulate blood pressure and blood flow
What factors control vascular smooth muscle?
- Membrane potential
- Hormones
- Myogenic mechanism
How does membrane potential affect vascular smooth muscle
How do hormones affect vascular smooth muscles
How does the myogenic mechanism affect vascular smooth muscle?
- Stretch of vessel wall
- Opens mechanical Ca2+ gates
- Contraction of vessel wall
What are the 3 different types of capillaries
- Continuous
- Fenestered
- Sinusoid
What are the characteristic features of continuous capillaries?
- Tight jucntions between endothelium
- Only some small solutes pass through intercellular clefts
- e.g. the blood brain barrier, retina and testis)
