blood grade 7.pdf

Subject: Biology Grade 7 TOPIC: BLOOD COMPONENTS LEARNING OBJECTIVES: List the components of blood as red blood cells, white blood cells, platelets and plasma Identify red and white blood cells, as seen under the light microscope, on prepared slides and in diagrams and ph...

Subject: Biology Grade 7 TOPIC: BLOOD COMPONENTS LEARNING OBJECTIVES: List the components of blood as red blood cells, white blood cells, platelets and plasma Identify red and white blood cells, as seen under the light microscope, on prepared slides and in diagrams and photomicrographs State the functions of the different components of blood. Describe the process of clotting as the conversion of fibrinogen to fibrin to form a mesh State the roles of blood clotting as preventing blood loss and preventing the entry of pathogens Blood components Blood is a liquid tissue Its is composed of : Plasma – Liquid part Red blood cells White blood cells Platelets Blood flows inside blood vessels. If blood vessels rupture blood may leak out and soon start clotting. Blood carries things you need, like oxygen and glucose, and waste products, such as carbon dioxide, around your body.  Component Function Each Red blood cell To carry oxygen from the lungs to every cell in the rest of the body component has a White blood cell To fight infection by pathogens function. and stop disease Carries the blood cells and Plasma platelets around the body Broken down parts of cells that Platelet form scabs PLASMA Liquid part of the blood. It is pale yellow colored fluid in which the blood cells and platelets are floating. 55% of the blood is plasma Plasma is made of 90-95 % water 5-10% are dissolved substances which include: Nutrients like glucose, amino acid, mineral ions, vitamins Waste products like Carbon – dioxide, urea, etc Clotting proteins Prothrombin and fibrinogen Protective proteins like Antibodies Plasma also contains hormones All these substances are being transported by the plasma from one place to another. Red blood cells Red blood cells are the most numerous cell in the blood. In one drop of blood there are around 3-5 million red blood cells. They are made in bone marrow. Red blood cells transport oxygen to all cells in the body. Red blood cells (RBCs) are highly specialised cells well adapted to transport oxygen efficiently: RBCs are biconcave disc shaped cells. This shape gives them a large surface area so that they can absorb a lot of oxygen RBCs have no nucleus. This provides extra space to fit in the red pigment called haemoglobin. This pigment is the oxygen carrier. RBCs contain the iron-rich protein called haemoglobin; give blood its red colour. This red pigment combines with oxygen to form oxyhaemoglobin and transports it to every cell in the body. RBCs also have a flexible cell membrane which enables them to stretch and change shape so that it can fit in the narrow capillaries. White blood cells White blood cells are part of the body’s immune system. They defend against infection by pathogenic microorganisms There are two main types, phagocytes and lymphocytes Phagocytes They kill the germs by engulfing them and then secreting enzymes to digest them. They have a lobed nucleus and are irregular in shape. 1. Bacteria recognized 3. Digested by 2. Bacteria engulfed and surrounded secreting enzymes This process is called phagocytosis Lymphocytes Produce antibodies to destroy the germs or pathogens They have a large round nucleus which takes up nearly the whole cell. Lymphocytes secrete antibodies and destroy the germs. Antigens attached to the surface of the germs and destroy them slowly. For every germ a specific antibody needs to be produced., https://www.youtube.com/watch?v=qCRwuxDpthY Platelets Platelets are fragments of cells that are involved in blood clotting where the skin has been cut or punctured When the skin is broken, platelets arrive to stop the bleeding SCAB: a dry, rough protective crust that forms over a cut or wound during healing. A series of reactions occur within the blood plasma Platelets release chemicals that cause soluble fibrinogen proteins to convert into insoluble fibrin and form an insoluble mesh across the wound, trapping red blood cells and therefore forming a clot The clot eventually dries and develops into a scab; this prevents further blood loss and acts as a barrier to pathogens https://quizlet.com/121981583/flashcards  Complete the worksheet given in the resource section.