1 Lesson 2 zBlood vessels zCardiac cycle zHeart Sounds

2 Blood vessels zThere are three types of blood vessels: zArteries zCapillaries zVeins

3 Blood vessels

4 Arteries zCarry blood away from the heart zThick muscular wall to withstand high pressure of blood zNarrow lumen zMost collagen (tough fibrous protein)- tough and durable zElastic fibres and smooth muscle- allows stretch & recoil

5 Arteries… cont zNo valves zBranch into smaller and smaller vessels- arterioles zContraction of smooth muscle of arterioles allows blood to be diverted to different parts of the body ze.g. fight or flight more blood to skeletal muscles and less to digestive system

6 Arteries… cont

7 Capillaries  Tiny vessels- 1 cell thick wall 10  m in diameter zExchange of nutrients and waste with tissues occurs here  Extensive branching network (capillary bed) throughout body tissues zOnly certain capillary beds open at one time to allow shunting of blood from one area to another

8 Capillaries… cont zMost numerous type of blood vessel in the body zPermeable walls zCarry blood at low pressure and low flow rate yReduces fluid loss through permeable capillary walls yAllows sufficient time for exchange of materials

10 Veins zCarry blood back to the heart zThin muscular wall as blood at low pressure zWide lumen- reduces resistance to blood flow zLess collagen, elastic fibres and smooth muscle

11 Veins… cont zHave valves zBlood at low pressure- return blood against gravity- so lie close to muscles- when muscle contract they squeeze the veins to temporarily increase the blood pressure

12 Veins… cont

14

Describe three things that this graph shows.

16 Major Blood Vessels NB heart muscle itself is supplied with blood by coronary arteries

17 Cardiac Cycle zA pattern of contraction (systole) and relaxation (diastole) by heart in 1 heart beat zLasts about 0.8 seconds (based on heart rate of 75bpm) zChambers alternately contract and relax zBlood always flows towards low pressure

18 Cardiac Cycle…cont 3 phases to the cycle: 1.Atrial systole 2.Ventricular systole 3.Diastole Decrease in volume Increase in pressure Blood forced out

19 Atrial systole zBlood flows into LA and RA under low pressure zLA & RA contract simultaneously zAV (bicuspid & tricuspid) valves open zBlood forced into LV & RV zAt this point LV & RV in diastole & SL valves closed

20 Ventricular systole z0.1 secs later zAV (bicuspid & tricuspid) valves close zBlood forced into LV & RV which contract z& push blood through open SL valves to arteries zHigh pressure in ventricles

21 Diastole zAtria & ventricles relax zElastic recoil of relaxing heart walls lowers pressure in atria & ventricles zBlood under high pressure in arteries drawn back into heart from veins

23 Heart Sounds zLub dub zLub- closing of AV valves zDub- closing of SL valves zHuman heart sounds zFeline heart sounds