1. Need for transport system
Chapter 19

2. Exchange of materials
Efficient exchange of materials requires a large surface area
Small objects have large surface area:volume ratio
Increased volume = decreased surface area
Larger organisms have less of inner tissues close to outside surface
- therefore less surface area
Nomogram – estimates human surface area
Small organisms – absorb directly through cell membrane
- diffusion is adequate
Large organisms – need transport systems & absorbing surfaces
- e.g alveoli, villi

3. Blood Vessels - known as exchange vessels Arteries
– pulsate due to pumping of heart
- thick walls, narrow lumen
Veins
– wide lumen = low resistance
- have valves
Arteries branch into arterioles
Veins branch into venules
Capillaries
- between venules and arterioles
- known as exchange vessels

4. Tissue Fluid Blood: cells, platelets, & dissolved substances
– bathed in plasma
Blood from arteriole to capillary undergoes pressure filtration
Plasma squeezed out through capillary walls = tissue fluid
All living cells located close to a capillary bed
Dissolved substances diffuse along conc gradient
Tissue fluid returns to capillaries at venule side by osmosis
Some tissue fluid enters lymphatic system
- fluid known as lymph

5. Heart & Circulation
Allows exchange between blood & external/internal environment
Heart structure
Valves:
Between atria & ventricles
- atrio-venticular (AV) valves
Right AV valve (3 flaps)
– tricuspid
Left AV valve (2 flaps)
– bicuspid (mitral)
Semi-Lunar valves
– separate ventricles from arteries

6. Heart & Circulation (2) Pulmonary System –
circulates blood between heart & lungs
Systemic system
– circulates blood between heart & rest of the body
Hepatic Portal vein
– carries blood from intestinal capillary bed to liver capillary bed
Liver has 3 blood vessels associated with it
- artery, vein & portal vein

7. Coronary Blood supply Coronary arteries – branched off from the aorta
Divide to form many capillaries
Cardiac muscle cells within 10um of a capillary (avg. is 60-80)
Coronary veins return blood to vena cava
Restricted or blocked supply = coronary heart disease
Deprived oxygen supply = muscle cell death
- myocardial infarction

8. Coronary Heart Disease
Atherosclerosis:
Plaques of fatty material on inner coat of artery
– atheromas
Enlarged by lipids & cholesterol, hardened by calcium
Restrict blood flow to an organ
Angina:
pain from insufficient blood supply to heart
- due to atherosclerosis

9. Coronary Heart Disease (2)
Coronary Thrombosis:
Blockage of coronary artery by a blood clot
Caused by blood flowing over uneven atheromas
Blood clots (thrombus) occur
Complete blockage = ‘heart attack’
Clots can break loose and cause blockages elsewhere

10. Diagnosis, Treatment & Risk
Partial blockage detected by an arteriography
- produce angiograms
If too advanced, coronary bypass is required
Aorta & coronary artery joined by veins from patients leg
Risk factors:
Smoking
Stress
Poor diet – excess cholesterol/fat
Obesity
Lack of exercise