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Understanding Blood Vessels and Cardiac Cycle

Learn about arteries, capillaries, veins, and the phases of the cardiac cycle in this comprehensive lesson. Explore the functions and characteristics of each blood vessel type and the intricate workings of the heart's contraction and relaxation phases.

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Understanding Blood Vessels and Cardiac Cycle

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  1. Lesson 2 • Blood vessels • Cardiac cycle • Heart Sounds

  2. Blood vessels • There are three types of blood vessels: • Arteries • Capillaries • Veins

  3. Blood vessels

  4. Arteries • Carry blood away from the heart • Thick muscular wall to withstand high pressure of blood • Narrow lumen • Most collagen (tough fibrous protein)- tough and durable • Elastic fibres and smooth muscle- allows stretch & recoil

  5. Arteries… cont • No valves • Branch into smaller and smaller vessels- arterioles • Contraction of smooth muscle of arterioles allows blood to be diverted to different parts of the body • e.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 10mm in diameter • Exchange of nutrients and waste with tissues occurs here • Extensive branching network (capillary bed) throughout body tissues • Only certain capillary beds open at one time to allow shunting of blood from one area to another

  8. Capillaries… cont • Most numerous type of blood vessel in the body • Permeable walls • Carry blood at low pressure and low flow rate • Reduces fluid loss through permeable capillary walls • Allows sufficient time for exchange of materials

  9. Veins • Carry blood back to the heart • Thin muscular wall as blood at low pressure • Wide lumen- reduces resistance to blood flow • Less collagen, elastic fibres and smooth muscle

  10. Veins… cont • Have valves • Blood 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

  11. Veins… cont

  12. Describe three things that this graph shows.

  13. Major BloodVessels NB heart muscle itself is supplied with blood by coronary arteries

  14. Cardiac Cycle • A pattern of contraction (systole) and relaxation (diastole) by heart in 1 heart beat • Lasts about 0.8 seconds (based on heart rate of 75bpm) • Chambers alternately contract and relax • Blood always flows towards low pressure

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

  16. Atrial systole • Blood flows into LA and RA under low pressure • LA & RA contract simultaneously • AV (bicuspid & tricuspid) valves open • Blood forced into LV & RV • At this point LV & RV in diastole & SL valves closed

  17. Ventricular systole • 0.1 secs later • AV (bicuspid & tricuspid) valves close • Blood forced into LV & RV which contract • & push blood through open SL valves to arteries • High pressure in ventricles

  18. Diastole • Atria & ventricles relax • Elastic recoil of relaxing heart walls lowers pressure in atria & ventricles • Blood under high pressure in arteries drawn back into heart from veins

  19. Heart Sounds • Lub dub • Lub- closing of AV valves • Dub- closing of SL valves • Human heart sounds • Feline heart sounds

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