1. Aims To examine components of the blood To examine the functions of the blood

2.  Blood is a viscous fluid.  It is slightly alkaline with a pH of 7.35-7.45.  Blood temperature is 38°C.  It makes up approximately 8% of a person ’ s body weight.  On average, males have 5-6 litres and females 4-5 litres.  Blood is made up of plasma, red blood cells, platelets and white blood cells.

3.  Plasma accounts for 55% of blood volume.  It is the liquid portion of blood.  When separated from blood, it is a pale, yellow fluid.  91-2% of plasma is water.  8-9% is made up of dissolved substances called solutes.

4.  Can you name functions of the blood?  Blood is involved in…  Transport – of nutrients, wastes, gases, hormones and heat.  Regulation – of pH, BP and temperature.  Protection – against blood loss and infection.

5.  Nutrients absorbed in the digestive system are transported to cells and tissues – can you provide examples?  Wastes such as CO 2 – Where is this made? Where is it taken to?  CO2 is transported in 3 ways – approx. 7% is dissolved in plasma; 23% attached to haemoglobin and 70% is carried as bicarbonate.  Plasma also carries other wastes such as urea.

6.  Hormones – are transported from endocrine glands to cells/tissues/other glands. Example?  Electrolytes (a substance that dissociates into ions; these carry an electric charge and can conduct electricity)  Examples include: sodium (Na⁺), calcium (Ca²⁺), potassium (K⁺), bicarbonate (HCO 3 ⁻).  These have many and varied functions in the body.

7.  Plasma proteins account for the biggest proportion of solutes in plasma (7%). 1. Albumin – made in the liver controls how much water is present between blood and tissues and regulates blood volume. Also transports some steroid hormones. 2. Globulins – globulins made by the liver carry substances through the blood e.g. fat and fat soluble vitamins. Globulins made by a type of WBC (B cells) are immunoglobulins or antibodies and are involved in defence against disease. 3. Fibrinogen - made by the liver is involved in blood clotting. Normally dissolved in plasma, it comes out of solution during the blood clotting process.

9. RBCs are biconcave This means they have a larger surface area to transport O 2. They are flexible T o squeeze through capillaries. RBCs lack a nucleus T his allows more room to transport oxygen. RBCs - Erythrocytes

10.  There are approx. 5 million RBCs in 1mm ³ of blood.  RBCs are packed with an iron-bearing protein called haemoglobin.  When haemoglobin combines with oxygen, it is referred to as oxyhaemoglobin.  Oxyhaemoglobin is unstable and readily releases O 2 in places where the O 2 concentration is low.  Oxygen then diffuses from blood capillaries into cells.

11.  Are not complete cells; they are irregularly shaped cell fragments.  There are between 250,000 – 300,000 platelets in 1mm ³ of blood.  Platelets are essential during the blood clotting process to prevent blood loss.  Normally, platelets travel through the blood in an inactive state and their appearance is uniform.  When activated e.g. because of damage to a blood vessel, platelets become activated, change shape and become ‘sticky’.

13. Along with other components of blood, a series of chemical reactions take place whereby a mesh of fibrin covers the damaged vessel. Activated platelets along with red and white blood cells become trapped in the mesh of fibres to ‘plug’ the damaged area.

14. There are approximately 10,000 WBCs in 1mm ³ of blood. They are complete cells and contain nuclei and organelles. WBCs prevent the body from infection. Unlike RBCs, some WBCs can leave the blood in order to protect tissues. There are many different types of white blood cell.

16.  WBCs work in different ways. Some release antibodies and chemicals to destroy pathogens whereas others have the ability to ‘eat’ pathogens.  Neutrophils and monocytes (and to a lesser degree, eosinophils) have the ability to ingest disease causing organisms.  This is a specialised form of endocytosis called phagocytosis.

17. Phagocytosis The phagocyte encounters a pathogen. In the diagram, viruses are depicted. 1

18. Phagocytosis Projections of the phagocyte’s membrane called pseudopods surround the virus. 2

19. Phagocytosis The pseudopods wrap around the virus and the virus is taken into the phagocyte. It is held in a vesicle called a phagosome. 3 phagosome

20. Phagocytosis The phagosome merges with lysosome(s) inside the cell to form a phagolysosome The virus particle is destroyed by digestive enzymes. 4

21. Phagocytosis The digested pathogen is then removed from the phagocyte by exocytosis. 5-6

23.  http://www.stolaf.edu/people/giannini/flasha nimat/cellstructures/phagocitosis.swf http://www.stolaf.edu/people/giannini/flasha nimat/cellstructures/phagocitosis.swf

24. Neutrophils These are the most abundant WBC. (40-70%) Lobed nucleus. Contains granules & stains pale pink/lilac. Active phagocytes. Numbers increase during acute infections. Can leave capillaries and are capable of independent movement.

25. Monocytes 2-8% of WBCs Largest WBC Large kidney- shaped nucleus Type of phagocyte They leave blood and migrate to tissues where they are known as macrophages.