L18 The peripheral circulation

Question 1

Descrtibe the composition of blood

Answer 1

Red + white blood cells
plasma - 55%
Platelets
Haematocrit = % of blood that is red blood cells

Question 2

Describe the structure + function of arteries, capillaries and vein

Answer 2

Walls made of smooth muscle, collagen, elastin and endothelium
Arteries away from the heart
Capillaries @ muscle sites. Diffusion
Veins, venous return

Question 3

What is vascular resistance?

Answer 3

= Measure of hindrance/opposition to blood flow through a vessel. Caused by friction between blood in the vessel wall

Question 4

Describe haemodynamics of fluid flow

Answer 4

Flow delivers O2 + nutrients to tissue.
Pressure is needed to maintain flow 
Resistance is provided by blood vessels 
Pressure generated by heart 
Most resistance by arteries and arterioles

Question 5

What are the mechanisms that determine the caliber of arterial resistance vessels by altering vascular smooth muscle tone

Answer 5

Neural - sympathetic nerves - vasodilate. Parasympathetic - vasoconstrict

Hormonal - Nor adrenaline released from adrenal glands. a-receptors dilate. b-receptors constrict

Myogenic - Arterial pressure increases therefore trans-neural pressure increases, which stretches arteries

Mechanical - tapping vein for blood sample will make it dilate

Metabolic - blood flow increases in relation to metabolic activity

EDRF - endothelial derived relaxing factors