The document discusses the circulatory system in mammals, including the different types of blood vessels (arteries, veins, capillaries) and their structures and functions. It also covers the exchange of substances between blood and tissues that occurs in capillaries, as well as the formation and movement of tissue fluid and its collection by lymphatic vessels. Key points include: - Arteries carry oxygenated blood away from the heart and have thick muscular walls to withstand high blood pressure. - Veins return deoxygenated blood to the heart and have thinner walls with valves to prevent backflow. - Capillaries are the smallest vessels and facilitate rapid exchange of substances through their thin, porous walls.

2. Chapter Overview Transport in Mammals 8.2 The Blood & Blood vessels 8.1 The Circulatory System - Introduction & Anatomy 8.3 The Hear t & Cardiac Cycle 8.4 Heart Diseases 8.1.1 The need for transport 8.1.2 Double Circulation 8.3.1. Structure and Function of heart 8.3.2 Heart valves, Systole and Diastole 8.2.1 Components of the Tissue Fluid a) Blood Plasma b) Red Blood Cells c) White Blood Cells d) Platelets 8.2.2 Exchange of Substances and The Lymphatic System 8.2.3 Haemoglobin 8.2.4 Rejection and ABO Blood Group 8.2.5 Structure-function of blood vessels 8.4.1 Myocardial infarction 8.4.2 Causes of Heart Diseases

3. Objectives Relate the structure of arteries, veins and capillaries to their functions. (b) Describe the transfer of materials between capillaries and tissue fluid.

4. TB PG 152 Organisation of Blood Vessels Arteries  arterioles  capillaries venules veins

5. TB PG 153 The Blood Vessels There are 5 types of vessels in the mammalian circulatory system. Arteries Arterioles Veins Venules Capillaries

7. Transports oxygenated bloodaway from the heart (except pulmonary artery) Wavy elastic band External layer(Loose connective tissue) Middle layer (Smooth muscle & elastic fibres) (Inner layer) Endothelium Lumen

9. Carry deoxygenated bloodtowardsthe heart(except pulmonary vein) External layer (loose connective tissue Middle layer (Thinner smooth muscle and elastic fibre Endothelium

11. Exchange of substances between blood and surrounding tissue (facilitated by one cell thick endothelium)One cell thick endothelium

13. Branches into smaller vessels called arterioles

15. Smaller vessels called venules come together to form vein

17. Smallest vessels of all

21. Smooth muscles contract or dilates  lumen constrict or dilate thus controlling blood flow

23. Smaller lumen than veins Due to presence of thicker layer of muscles

25. Less elastic, muscular walls

26. Presence of valves  prevent backflow of blood

28. Walls are less thick and muscular and contain less elastic tissue Blood is under lower pressure, so walls need not be as strong

30. MJR Biology Department Vein Semi-lunar valve 1. Muscles contract, push against the walls of the blood vessels 2. Narrowing of vein causes blood cells to be pushed forward 7/12/2010 16

31. Varicose Vein Varicose veins are distended branches of the major veins in the leg. They become distended due to failure of the valves in the main veins which allows blood to fall back down the leg (reflux)

32. Varicose Vein Varicose veins are more common in women than in men, and are linked with heredity[6]. Other related factors are pregnancy, obesity, menopause, aging, prolonged standing, leg injury and abdominal straining. Varicose veins are bulging veins that are larger than spider veins, typically 3 mm or more in diameter

36. TB PG 164 Cell Transport function Cell Cell Cell Cell RBC Cell RBC Cell Cell Cell Cell Arteriole Capillaries Venule Cell Cell Cell Exchange of substances Useful materials such as glucose and oxygen are transported from plasma /RBC (higher concentration) to tissue fluid (lower concentration), down a concentration gradient, by diffusion. The useful materials in the tissue fluid will diffuse to the cells when concentration of these useful materials in the tissue fluid becomes higher than that in the cells. Osmosis will also occur. Cell Cell Cell Cell Cell

37. TB PG 164 Cell Transport function Cell Cell Cell Cell RBC Cell RBC Cell Cell Cell Cell Arteriole Capillaries Venule Cell Cell Cell Exchange of substances Cell Waste products such as carbon dioxide and urea are transported from cells (higher concentration) to tissue fluid (lower concentration), down a concentration gradient, by diffusion. The waste products in the tissue fluid will diffuse to the plasma when concentration of the waste products in tissue fluid is higher than plasma. Cell Cell Cell Cell

38. TB PG 164 Venule end Arteriole end Formation of tissue fluid What are the small or elastic molecules in blood? What is the structure of capillaries? Partially permeable - Plasma (water + small soluble molecules) - WBC What does partially permeable mean? Allows small molecules to move through. Elastic molecules maybe able to squeeze through as well. What are the big or less elastic molecules in blood? - RBC - Plasma proteins

39. TB PG 164 Water, small soluble molecules Water, small soluble molecules and WBC Venule end Arteriole end Water, small soluble molecules Water, small soluble molecules and WBC Red blood cells and big plasma proteins continue to move in the capillaries. As blood flows from the arteriole to venule end, the blood becomes concentrated with solutes, such as plasma proteins. Water from tissue fluid moves into the blood by osmosis at the venule end and small soluble molecules move into the blood by diffusion. High pressure at the arteriole end forces water, small soluble molecules and white blood cells out of capillaries through the partially permeable endothelium into the tissue fluid. Formation of tissue fluid Remaining tissue fluid is collected by lymphatic vessels. The fluid in lymphatic system is known as lymph. Lymph will be emptied to blood circulation through a vein near heart.

40. Blood pressure in different blood vessels

42. Comparing the Blood Vessels

43. Comparing the Blood Vessels

44. The figure below shows three types of blood vessels (not drawn to scale) in the human body. Which of the following is true?

46. Blood plasma hence forced to leave capillaries

47. And enter body tissues

48. Soluble proteins cannot pass through capillaries.

49. Hence the fluid that enters the body tissues does not contain these proteins.