Chapter 26: Blood Blood

Makes up about 8% of normal body weight Average adult has 5 – 6 litres of blood What is the blood composed of? Red blood cells Platelets White blood cells Plasma

Red Blood Cell Platelets

Plasma  Pale golden liquid, makes up 55% of the blood  Made of: - 90% water - 7% plasma proteins: Antibodies- made by WBC to fight foreign bodies Clotting proteins- activate to form clots - 3% dissolved materials  Function: - Transport dissolved materials e.g. hormones, vitamins, urea, amino acids, CO 2, glucose etc. - Maintains body temperature  Serum is plasma without the clotting proteins

Plasma

Red Blood Corpuscles - Erythrocytes  Produced in the bone marrow e.g. ribs, breast bone  Bioconcave in shape (doughnuts) and consist of a flexible membrane, which contains the protein haemoglobin.  Can not repair themselves, only live ~4months  RBCs are broken down by liver and spleen.  The iron, from haemoglobin, is stored in liver and may be recycled – new haemoglobin, the remainder is converted to bile pigments.

 Function is to transport oxygen around the body - Haemoglobin joins with O 2 in areas of high O 2 conc. and releases O 2 in areas of low O 2 conc.  Anaemia is a lack of haemoglobin or RBCs - symptoms – pale, tiredness - treatment – iron (diet, tablets, injection)

Red Blood Corpuscles – Extended Study Higher Level Only  When first made RBC have a nucleus, but this is lost within a few days.  Also lack mitochondria.  Bioconcave in shape (doughnuts). This gives them large surface area for exchange of oxygen.

Red Blood Corpuscles – Extended Study Higher Level Only  Haemoglobin has the strong ability to form a loose chemical bond with oxygen: - Lungs – haemoglobin combines with four O 2 molecules forming OXYHAEMOGLOBIN - Body cells – haemoglobin loses O 2 very readily allowing it to supply the cells in the body with O 2 HAEMOGLOBINOXYHAEMOGLOBIN LUNGS BODY CELLS

White Blood Cells (Leucocytes)  Larger than RBC  Have a nucleus  No definite shape  Fewer in number than RBC  Made in bone marrow  Some mature in the lymph system  Leukaemia is a form of cancer in which the WBC produce to quickly and don’t mature  Leukaemia may be treated by radiation or drugs

 WBC function is to defend against and fight infection: They do this by engulfing (surrounding) the foreign substance. In this way they ‘eat’ bacteria therefore they are called phagocytes  There are different types of WBCs: - Phagocytes – this type of WBC engulfs bacteria/viruses and digests them e.g. Granulocytes & Monocytes - Lymphocytes – react to invading bacteria/viruses by producing antibodies, which play an important role in defending the body from infection.

Phagocytes(75%): Granulocytes: - large lobed nucleus - tiny granules in cytoplasm - made in red bone marrow - function is to engulf bacteria in the same way as amoeba feeds Monocytes(Macrophages): - large cells that act as scavengers and digest bacteria and other particles - kideny-shaped nucleus White Blood Cells – Extended Study Higher Level Only

White Blood Cells – Extended Study Higher Level Only Lymphocytes(25%): - made in bone marrow - stored in lymphatic system e.g. spleen, lymph nodes - large round nucleus - very little cytoplasm - survive from 3 months to 10 years - main function is to produce antibodies

Platelets (Thrombocytes)  Platelets are fragments made in the bone marrow from large cells called megacytes  No nucleus  Function is to clot blood by sticking together  Blood clots - cause the prevention of entry of microorganisms - reduce blood loss  Haemophiliacs cannot form blood clots as they lack a clotting protein (Factor VIII)  If a clot forms in a damaged vessel it will block it. This is called Thrombosis – strokes, heart attacks

When a blood vessel is cut three mechanisms help to reduce blood loss: (i) vessel narrows to reduce blood flow and so blood loss (ii) platelets stick to damaged cells forming a temporary clot (iii) complex clotting mechanisms occurs. This involves up to 30 chemicals as soluble fibrinogen is converted to insoluble fibrin and this forms a mesh at site of cut. The clot reduces blood loss and stops bacteria entering.

Red blood cells White blood cells Platelets Plasma Contain Haemoglobin (colour), Carry Oxygen, Donut shaped, no nucleus Fight infection, larger than RBC’s, no definite shape and have a nucleus. Produce Antibodies to fight infection, Some WBC’s can ‘eat’ bacteria or viruses These cells are involved in clotting. When activated they become sticky and bind together blocking the wound. No nucleus. Liquid part of blood. ~90% water. The rest is made up of cells and dissolved substances, such as protein, glucose, urea 4 Components of Blood

Functions of Blood 1. Transport Substance Carried FromCarried To OxygenLungsCells Carbon Dioxide CellsLungs GlucoseIntestinesCells UreaLiverKidneys HeatInternal Organs Around Body

2. Fighting Infection If Micro-organisms enter ‘invade’ our body we are said to have an infection. WBC’s (phagocytes and lymphocytes) fight these infections.. 3. Blood Clotting Platelets in the blood form a clot closing the wound and stopping the flow of blood. Repair System. Clots also prevent disease causing organisms entering through wounds. Functions of Blood

Blood Groups There are four major blood groups: - A, B, AB, O These are due to different antigens on the surface of red blood cells. Blood group O is called the universal donor because it can be given safely to all the other four blood groups. Blood Group AB is the universal recipient as they can receive blood from everyone

Blood Transfusion: if incorrect blood type is given to a person, the person will see it as foreign and produce antibodies against it. This will lead to clumping of blood cells. Blood Groups Donor/RecipientABABO AOkXX BX X ABOk OXXX

Blood Groups The Rhesus Factor: The rhesus system contains two groups: 1) rhesus positive (Rh+) – 85% of people 2) rhesus negative (Rh-) – 15% of people Rh+ means you have the rhesus protein (protein D) on your red blood cells Rh- means you do not have rhesus protein on your red blood cells. Rh- individuals consider Rh+ blood to be foreign and therefore cannot receive blood from them. Rh+ individuals can generally receive Rh- blood safely

Blood Groups Rhesus Factors and Pregnancy: A problem arises if Rh- mother is pregnant with Rh+ baby. On a second pregnancy this may cause antibodies from mother to damage blood cells of baby. This can cause anaemia, brain damage or death to baby. Treatment is an injection with a blood product to the mother on first pregnancy.