blood vessel structure

Question 1

what is the pulmonary circuit

Answer 1

• supplied by right heart
• BV to and from heart to the lungs
• closed system

Question 2

what is the systemic circuit

Answer 2

• supplied by left heart
• BV to and from heart to systemic tissues
• closed system

Question 3

what is series flow

Answer 3

• blood flows in series through pulmonary and systemic circuits
• ensures all blood is oxygenated
• different pressure
• pulmonary and systemic
• exception: GI tract and liver connected in series

Question 4

what is parallel flow

Answer 4

• blood flows in parallel through different capillary beds of systemic circuit
• systemic
• advantages: each capillary bed receives oxygenated blood, independent regulation, same pressure
• exception: GI tract and liver connected in series

Question 5

what are blood vessels and the types of BV

Answer 5

• delivery system of dynamic structures
• ability to change shape and diameter
• heart, elastic arteries (big), muscular arteries, arterioles, capillaries, post capillary venules, small veins, large veins heart)

Question 6

describe the general structure of BV

Answer 6

• lumen: hollow interior, flow of blood, bigger in veins than arteries
• inner lining: lines lumen, endothelial cells, flat, smooth, undisturbed flow of blood without turbulence
• muscle: some have smooth, fibrous / elastic connective tissue
• tunics: main coverings of BV, three main layers, intima, media and externa

Question 7

describe the three main layers of tunics

Answer 7

• intima: most internal, endothelium (lines lumen), sub-endothelial layer and internal elastic membrane
• media: middle, smooth muscle, sheets of elastin, external elastic membrane, controlled by sympathetic vasomotor nerve fibres control, bigger in artery
• externa: collagen fibres (stability, protection, reinforcement) and vasa vasorum (vessels, nourish external layer)

Question 8

what are / different types of arteries

Answer 8

• carry blood away from the heart
• oxygenated except for pulmonary arteries and umbilical vessels of foetus
• elastic (conducting): large thick walled (2.5cm), large lumen (low resistance), pressure reservoir, expansion following contraction of H, regain original shape, e.g. (carotids, subclavian, pulmonary artery, iliac artery - branch off aorta)
• muscular (distributing): distal to elastic arteries, deliver blood to organs, thin (2-10mm), thick tunica media, active in vasoconstriction, two elastic layers (IEL and EEL), affect peripheral resistance maintain pressure

Question 9

what are arterioles

Answer 9

• small branch of arteries, conduct blood away from heart
• variable resistance, depends on contractile state of smooth muscle
• not many

Question 10

how is blood vessel diameter regulated in arterioles

Answer 10

• nervous input regulates smooth muscles contraction in vascular system
• potent agents can affect diameter CO2 (dilate), NO (dilate), adrenaline / noradrenaline (constrict), ADH (constrict), caffeine, stimulants, histamine

Question 11

what are / the types of capillaries

Answer 11

• microscopic, one cell thick, single RBC at a time
• contact tissue cells
• directly serve cellular needs
• passage of oxygen and nutrients
• all tissues except cartilage and epithelia
• continuous: abundant in skin and muscles, tight junctions connect endothelial
• fenestrated: contain pores, passage of bigger molecules, more permeable than continuous (kidney, intestine)
• sinusoidal: fewer tight junctions, larger intercellular clefts, large lumens, molecules pass between blood / tissue (liver only)

Question 12

explain what / how the blood brain barrier is formed

Answer 12

• protective mechanism (stop toxic substances / bacteria / viruses from reaching brain), - endothelial cells attach without synaptic cleft
• movement via diffusion (passive or active)
• CO2, O2, and alcohol can diffuse into the brain
• therapeutic targets aim to cross the BBB (develop compound able to cross, treatment of strokes)

Question 13

what are venules

Answer 13

• post capillary (PVC’s)
• very porous, allows fluids / WBC into tissues
• endothelium, few pericytes, thin endothelial cells
• 1-2 layers of smooth muscle

Question 14

what are muscular / medium veins

Answer 14

• from PVC’s to small muscular venules
• lead to medium veins
• low BP, surrounded by skeletal muscle (contraction = pushes blood to heart)
• valves prevent back flow

Question 15

what is atherosclerosis

Answer 15

• hardening of arteries and mild build up of plaque (fat, cholesterol, calcium)
• increased fatty diet, unhealthy lifestyle, genetic condition
• less BF to organ, inelastic arteries, increase BP
• plaque = clot, constriction, heart attack / stroke
• coronary artery: at risk, inside heart, gives blood and oxygen to heart tissue
• aorta at risk