1. Human Physiology Lesson 12c- Blood Vessels

2. Circulation Question

3. Transport of Blood
How is blood transported around the body?

4. Blood Vessels

5. Blood Vessels NEED TO KNOW
THE DIFFERENT TYPES AND HOW THEY ARE ADAPTED TO THEIR FUNCTION

6. Blood vessels Where does blood have to move most quickly? Why?
Where does blood have to slow down, and why?

9. Blood Vessels
Draw, describe and explain the structure and function of an artery, a capillary and a vein (use page 238)
Describe the job of the coronary arteries and the problems that arise if they are blocked

10. Blood Vessels

12. Artery

13. ARTERY STRUCTURE
Lumen-Relatively small. Blood travels at a high resistance
Smooth Muscle- Contracts to move blood along the artery. This contraction of smooth muscle is known as peristalsis. Smooth muscle makes up the majority of an artery
Elastic tissue-fairly large proportion of elastic tissue because the blood in an artery is under very high pressure. The elastic tissue maintains the shape of the artery.

14. Artery Function
Transportation of OXYGENATED BLOOD to organs (exception is the pulmonary artery which transports deoxygenated blood to the lungs)
Carries blood at a very high pressure
Always leaves the heart

20. Arteries and arterioles

21. Veins

22. Veins and venules STRUCTURE
Lumen relatively large. A lot larger than the lumen of an artery. This allows blood to flow with little resistance.
Less elastic tissue and smooth muscle than an artery
Contains valves. This prevents the back flow of blood.
Positioned between large muscles. When the muscles contract they force blood along

23. Veins Blood is at lower pressure Walls thinner Walls less muscular
As muscles contract they pinch the veins
Valves ensure blood flows back to the heart 23

24. Vein Function
Transportation of DEOXYGENATED BLOOD to organs (exception is the pulmonary vein which transports oxygenated blood from the lungs)
Always to the heart apart from the pulmonary vein

27. Veins and valves

29. Capillaries How are they adapted? Adaptation Importance Very small
Thin-walled
Numerous 29

30. Capillaries How are they adapted? Adaptation Importance Very small
5-20µm in diameter
High surface area to volume ratio
When RBCs squeeze out, surface area increases & increase of diffusion
Thin-walled
Thin layer of endothelium and its basement membrane, no connective tissue
Smooth, thin and flexible
Numerous
Form capillary bed
Provides large surface area 30

31. Use the diagram to compare arteries, capillaries and veins31

32. 32

33. Arteries and Arterioles
Veins and Venules
Capillaries
Arteries and Arterioles
                                                         
                                                              
                                                        

34. Blood Vessels
ARTERY
VEIN
CAPILLARY

35. Blood Vessels ARTERY VEIN CAPILLARY Thick muscular wall
Thin muscular wall
No elastic tissue
Elastic tissue
Contains valves
No muscular wall
Small lumen
Large lumen
Constricts
Impermeable
Permeable
Little elastic tissue

36. How blood is transported
Arteries:
Structures that carry blood away from the heart
Rigid to take pressure of blood right out of heart
Veins:
Looser to expand more
Store great quantities of blood
Capillaries:
Very narrow tubes between arteries and veins where diffusion occurs 36

37. Arteries Capillaries Veins37

38. Arteries Capillaries Veins
Thick muscular wall
Large amount of elastic tissue
Small lumen
Blood under high pressure
Valves when aorta and pulmonary artery begin in the heart
No muscle
No elastic tissue
Relatively large lumen
Blood under low pressure
No valves
Thin muscle wall
Little elastic tissue
Semi-lunar valves maintain one-way flow of blood 38

39. What does this diagram show?39

40. VASOCONSTRICTION: reduction of blood flow
-Arterioles connect arteries with capillaries
-They become smaller as approach target tissues
-Can be constricted = reduce blood flow
-Can be dilated = increase blood flow
VASOCONSTRICTION: reduction of blood flow
VASODILATION: increase of blood flow 40

41. Key Questions
Suggest why arteries close to the heart have more elastic fibres in their walls than arteries further away from the heart
In the disease atherosclerosis, or ‘hardening of the arteries’, layers of cholesterol build up inside artery walls, reducing their elasticity. Why is this dangerous?
How does the size of capillaries enable them to carry out their function of metabolic exchange
Suggest a reason for the following:
a) Normal venous pressure in the feet is about 25mmHg. When a soldier stands at attention the blood pressure in his feet rises very quickly to about 90mmHg
b) When you breathe in, that is when the volume of the thorax increases, blood moves through the veins towards the heart 41

42. Elastic fibres allow the artery to stretch and recoil as blood pulses through. Nearer the heart, the pressure is higher so more elastic fibres are needed to cope with these large pressures and pressure changes
If arteries cannot expand as a surge of blood at high pressure enters them, they are more likely to burst. Moreover, the build-up cholesterol narrows the lumen, so forcing blood through a narrower space, which can increase its pressure, further increasing the risk of the vessel bursting. There is also a risk of the vessel becoming permanently blocked.
Capillaries are small, thin walled, and very numerous – maximising the rate of exchange of metabolic substances by diffusion
Gravity pulls blood downwards. Normally, contraction and relaxation of leg muscles squeezes in on leg veins; valves in them ensure blood moves upwards and not downwards. When standing to attention, these muscles are still, so blood accumulates in the feet.
4b.As thoracic volume increases, pressure inside the thorax decreases. This decreases the pressure in the blood vessels in the thorax. The effect is very small in the arteries, but more significant in the veins. The relatively low pressure of the blood in the veins in the thorax, compared with the pressure in the veins elsewhere, produces a pressure difference causing blood movement towards the thorax. 42