Week 2 Flashcards
Name the layers of structure of the vessels
- Tunica intima
- Tunica Media
- Tunica externa
Tunica Intima
Innermost layer containing endothelial cells - very smooth to minimise friction
Tunica Media
Middle layer of elastic and smooth muscle fibres. Much thicker in arteries. Allows for vasoconstriction/dilation
Tunica externa
Outermost layer. Constructed from connective tissue. these fuse with adjacent tissue to anchor vessel.
Elastic arteries
Largest in the body. Contain a higher proportion of elastic fibres in tunica media. Helps blood flow away from the heart (walls are distended during ventricular systole- recoil during ventricular diastole). Elastic fibres function as pressure reservoirs- stretched elastic fibres store mechanical energy which is converted into kinetic energy to push blood forward when the artery recoils. Hence, aorta is an elastic artery.
Muscular arteries
Distributing arteries. Tunica media contains more smooth muscle fibres than elastic. Greater ability to vasoconstriction/dilate. Continuous partial muscle contraction known as vascular tone (helps maintain pressure and blood flow as well as helps to shunt blood to specific areas).
Arterioles
Small arteries. Only 1-2 layers of smooth muscle cells. Regulate blood flow across capillary networks
Types of capillaries
- Continuous
- Fenstrated
- Sinusoid
Continuous capillaries
Most numerous
Found in CNS, lungs, muscle , and skin
Endothelial cells form a continuous tube
Fenestrated capillaries
Found in kidneys, small intestine villi, choroid plexus, ciliary process
Endothelial cells have small holes called fenestrations
Sinusoid capillaries
Found in liver, red bone marrow, spleen, ant. Pituitary, adrenal glands, parathyroid
Larger diameter
Can have larger fenestrations
Incomplete or no basement membrane
Large clefts between endothelial cells
Permit the passage of large proteins and blood cells.
What two factors is blood flow dependent on
- Pressure difference
- Vascular resistance
What is pressure difference
Blood flows from an area of higher pressure to lower pressure
What is vascular resistance
Caused by friction between the blood and vascular wall.
Dependent on 3 factors:
1. Lumen size of blood vessel (smaller size=increased resistance)
2.Viscosity of blood (increased viscosity= increased resistance)
3.Length of blood vessel (longer blood vessel= increased resistance)
What is blood pressure produced by?
Ventricular contraction