Chapter 26: 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 cellsPlatelets

White blood cellsPlasma

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 bodiesClotting proteins- activate to form clots- 3% dissolved materials

Function:- Transport dissolved materials e.g.

hormones, vitamins, urea, amino acids, CO2,

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 O2 in areas of high O2 conc. and releases O2 in areas of low O2

conc. Anaemia is a lack of haemoglobin or RBCs

- symptoms – pale, tiredness

- treatment – iron (diet, tablets, injection)

Red Blood Corpuscles – Extended StudyHigher 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 StudyHigher Level Only

Haemoglobin has the strong ability to form a loose chemical bond with oxygen:

- Lungs – haemoglobin combines with four O2 molecules forming OXYHAEMOGLOBIN

- Body cells – haemoglobin loses O2 very readily allowing it to supply the cells in the body with O2

HAEMOGLOBINHAEMOGLOBIN OXYHAEMOGLOBINOXYHAEMOGLOBINLUNGS

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 StudyHigher Level Only

White Blood Cells – Extended StudyHigher 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 Blood1. Transport

Substance Carried From Carried To

Oxygen Lungs Cells

Carbon Dioxide

Cells Lungs

Glucose Intestines Cells

Urea Liver Kidneys

Heat Internal 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/Recipient A B AB OA Ok X X OkB X Ok X Ok

AB Ok Ok Ok OkO X X X Ok

Blood GroupsThe Rhesus Factor:The rhesus system contains two groups:

1) rhesus positive (Rh+) – 85% of people2) 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 GroupsRhesus 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.