1. The Circulatory System Unit III

2. The Circulatory System Circulation, or transportation of blood is a vital function; life can’t go on without it The Circulatory System is made up of: –The heart –The blood vessels –The blood

3. Blood Physical Characteristics: red, sticky, distinctive taste/smell, dries quickly Sometimes called ‘life stream’ – it flows through our bodies carrying necessities of life (oxygen, nutrients, chemical messengers) to the cells, as well as transporting away the wastes produced by the cells (carbon dioxide, heat, extra water) It only takes your blood 30 seconds to circulate through your entire body

4. The average human body contains about 5 litres of blood: –55% is made up of plasma (straw coloured fluid which is 90% water and carries many dissolved substances) –45% is solids (red and white blood cells, and platelets)

6. Red Blood Cells Called erythrocytes Produced in bone marrow Round with a hollow depression in each side It’s shape gives it a large surface area, while remaining small, allowing it to pass through very tiny blood vessels

8. No nucleus –An unusual characteristic for cells; they start off having one, but as the cells mature their nucleus shrinks and disintegrates Oxygen carriers of the body

9. Contain haemoglobin which is a compound containing iron The haemoglobin molecule can combine with four oxygen molecules creating the bright red compound called oxyhaemoglobin –It releases oxygen when your body needs it

10. Red blood cells are responsible for a lot of work, so they wear out quickly – they only last 3-4 months Old red blood cells are broken down in the liver and spleen and the iron in them is returned to the bone marrow for new cells to use –The replacement rate is 1-2 million cells per second

11. White Blood Cells Called leukocytes Contain a nucleus Colorless, and although are usually spherical they can change shape Larger than red blood cells, but are far less numerous There is 1 white blood cell for every 600 red blood cells

13. Most are produced in bone marrow, but some are also produced in lymph tissue at several sites in the body Several types of white blood cells Function – to protect the body from infection and disease-causing organisms (pathogens)

15. All white blood cells possess the following characteristics which help them perform their function: –Amoeboid Action: can move independently; can change shape and squeeze through tiny pores to move into and out of body tissue

16. –Phagocytes – can surround bacteria and digest their toxic proteins; can join together in order to surround large products which must be removed from the body –Chemical Properties – react to charged particles, proteins and other chemicals which may be present in areas of injury and inflammation; some cells produce chemicals called antibodies (proteins) to neutralize the effects of certain foreign chemicals

18. Platelets Much smaller than red blood cells – about 250 000 to 300 000 for each mm 3 Responsible for the initial stages of blood clotting, the process which prevents loss of blood from a wound. If blood doesn’t clot, you would loose too much blood and die.

19. No nucleus; not actual cells, but are tiny fragments of cells that contain a special enzyme that initiates clotting

20. Blood Types Determined by the presence or absence of certain antigens on the red blood cells Two types of antigens: A and B If A is present, type A blood; if B is present, type B blood; if both present, type AB; if neither are present, type O blood

21. The antibodies found in blood are always the opposite of their antigen (blood type) For example, type A blood contains the A antigen, but the B antibody (needed to fight off foreign antigens... things other than A

22. Type of BloodAntigens Present on Red Blood Cells Antibodies Present in Blood Plasma AAB BBA ABA and BNeither A or B O A and B

23. Rh factor This is an antigen (chemical) found on the red blood cells of most people If your blood has the chemical your blood is said to be Rh positive (Rh +) If your blood does not have it, your are Rh negative (Rh -)

24. Connected to your blood type –Ex) your blood may be AB+ It is particularly important for expectant mothers to know their blood’s Rh factor – if it is the opposite to the baby’s this could be a big problem and the baby’s life could be in danger since the mother’s blood may attack the baby’s

25. Moving Blood throughout the Body Blood flows through your body through a closed system of tubes called blood vessels Your body has three main types of blood vessels: –Arteries –Veins –Capillaries

26. Arteries –Carry blood away from the heart –Blood is rich in oxygen and nutrients –Cary the materials needed by the cells –Arterioles = small arteries

27. Veins –Carry blood from the body back to the heart –Blood in the veins carries dissolved waste material –Venules = smaller veins

28. Capillaries –Tiny and thin tubes that connect arterioles and venules –Most of the blood vessels in your body are capillaries

29. The Heart Blood is pumped throughout your body by the heart The heart is located in the thoratic cavity, well-protected by the rib cage The heart is nestled between the lungs, with its lower end slightly toward the left side

30. An adult heart is about the size of a large fist (300 g) It is not rigidly attached to any of the surrounding tissues, but is suspended by the large blood vessels attached to it –This allows it to move loosely in place as it contracts

31. Parts of the Heart The heart muscle has two separate pumps Right side: responsible for collecting blood from the body and pumping it to the lungs Blood flows back from the head and arms to this side of the heart through a large vein called the superior vena cava, which leads into the upper right-hand chamber called the right atrium

32. Blood from the trunk and legs enters the same chamber via the inferior vena cava Both the right and left atria are thin-walled chambers which lie above the ventricles – their function is to collect blood and to pass it to the ventricles (contracting vessels)

33. Right ventricle – connected to the right atrium via the tricuspid valve, which prevents blood from flowing back into the atrium when the ventricle contracts When the right ventricle contracts, it pushes blood into the pulmonary artery, which carries blood into the lungs where its load of CO 2 wastes are released and a fresh load of oxygen is absorbed

34. The newly oxygenated blood flows into the left atrium through the four pulmonary veins – this portion of the circulatory system (the heart to lungs and back) is called pulmonary circulation

35. Contractions of the left atrium push the blood through the bicuspid valve into the left ventricle (largest and most heavily muscled chamber of the heart), which forces blood to every part of the body as it contracts

36. The blood is pushed out from the left ventricle to the largest blood vessel in the body, the aorta – this portion of the circulatory system is called the systemic system since it supplies blood to the remaining body systems

37. Blood Pressure If the blood is to reach the hands and feet, the brain, and every part of the body, it must be pumped out of the heart under very considerable pressure Highest pressure occurs in the aorta

38. As blood passes into smaller vessels and the distance from the heart becomes greater, the pressure decreases The pressure in any vessel varies as a result of 5 major factors:

39. 1.The amount of blood – if there is loss of blood, the pressure in the system drops because of the decrease in volume 2.The heart rate – the faster the heart pumps blood, the greater the pressure which is built up (there is more blood); pressure falls as the heart rate decreases, especially during sleep/rest

40. 3.The size of the arteries – when arteries dilate (larger in diameter), the volume of the vessels increases and the pressure falls (more room to flow). If the arteries constrict pressure is built up because of the extra resistance to blood flow

41. 4.Elasticity – the walls of arteries must be flexible and elastic in order to expand as blood is forced out of the heart, and then relax after the blood has flowed through. If they can’t stretch properly they are ‘hardened.’ This is common in older people and results in high blood pressure

42. 5.The viscosity of blood – viscosity = thickness of blood; thick, sticky fluids flow less readily than thin, watery fluids

43. Measuring Blood Pressure Normal blood pressure is less than or equal to 120/80 mm Hg Systolic Pressure: numerator; the highest pressure generated when the ventricles contract Diastolic Pressure: denominator; when the ventricles relax and the elastic walls of the arteries offer the least resistance