Blood and circulatory system

Fawzi A. BabikerDepartment of PhysiologyE-mail: fawzi.b@hsc.edu.kw

Reference: Human Physiology, by: Stuart Ira Fox; 11th Edition.

• Blood– Composition of Blood– Hematopoiesis– Blood types– Blood clotting

• The Circulation– Heart structure– Blood vessels– Cardiac cycle– Heart sounds– Electrical activity of the heart

Blood and Circulation

Major Parts of the Circulatory System

- Cardiovascular System:- Heart- Blood vessels- Blood

- Lymphatic System:- Lymphoid tissue- Lymph vessels- Lymph

Functions of the circulatory system

Transport:1- All substances essential for cellular metabolism. 2- Respiratory: oxygen and carbon dioxide.

3- Nutritive: digested food materials.

4- Excretory: metabolic wastes, excess water and ions.

Regulation:1- Hormonal: from sites of origin to the target tissues.

2- Temperature: diversion of blood between superficial and deeper vessels to control body temperature.

Protection:1- Clotting: protection against blood loss.

2- Immune: protection by leukocytes against infectious diseases.

Constituents of the blood

- Blood consists of :

1- Plasma: fluid part of blood contains proteins and electrolytes.

2- Formed elements: blood cells (erythrocytes, white blood cells, platelets).

Blood is about 8% of the total body weight (5L). It is either arterial blood or venous blood.

PlasmaPlasma: Straw-colored liquid consists of water and dissolved solutes.

Plasma

Blood cellsSerum: is similar to plasma onlyit is formed after blood clotting.It does not contain fibrinogen.

1- Electrolytes (ions): Na+, K+, Ca++, Cl-, HCO3

-

Contains:

2- Organic molecules: Cholestrol, glucose, protein, urea, lactic acid, etc.

3- Hormones: insulin, testosteron, growth hormone, etc.

4- Enzymes: lactate dehydrogenase (LDH), creatine phosphokinase (CPK), etc.

Plasma Proteins: 7%-9% of plasma volume.

i- Mainly albumins: account for 60% to 80% of the plasma proteins (produced by the liver).

ii- Globulins:

iiA- Alpha globulin and Beta globulin: transport lipids- and fats- dissolved vitamins.

iiB- Gamma globulins: antibodies produced by lymphocytes (immunity).

iii- Fibrinogen: essential for blood clotting (produced by the liver).

Plasma proteins

Formed elements of the blood

• Contain the protein haemoglobin.

• Haemoglobin carries oxygen around the body.

• At the centre of the haemoglobin molecule is an iron atom (heme).

1- Red blood cells (erythrocytes)

Hemoglobin

• Most abundant cells of the blood.

• Do not have a nucleus

• Biconcave discs, 7 m diameter and 2.2 m thick.

2- Platelets

• Called also Thrombocytes.

• The smallest of the formed elements.

• They play an important role in blood clotting.

3- White blood cells WBC (Leukocytes)

• Protective cells of the body. They contain nuclei, move in amoeboid fashion and they can pass the capillary wall (diapedesis or extravasation).

• They are granular or agranular (non granular).

• Neutrophils are the most abundant type of the granular cells.

Granular Agranular

1- Hematopoiesis

Blood cells are formed by a process of hematopoiesis.

During embryogenesis the blood cells are formed from stem cells in the liver.

Soon after birth the stem cells migrate to the bone marrow.

Erythropoiesis is the formation of erythrocytes.

Leukopoiesis is the formation of leukocytes.

Bone marrow

Formation of blood cells

A- Erythropoiesis

This process takes 3 days. 2 days in bone marrow and circulate in the blood in the 3rd day.

Life span of a blood cell is 120 days after which it is removed by the phagocytic cells of spleen, liver and bone marrow.

Erythropoieis = the process of formation of erythrocytes (RBCs). This process occurs in the bone marrow (myeloid tissue).

Bone marrow/myeloid tissue is the red tissue inside bones.

B- Leukopoiesis Leukopoieis = the process of formation of leukocytes (WBCs).

This process occurs in lymphoid tissue (lymph nodes, tonsils, spleen and thymus.)

Red blood cells antigens and blood types (ABO system)

Every antigen type is coupled with antibodies secreted by the lymphocytes act against the other antigens.

There are certain molecules on the surface of RBCs. These molecules are called antigens (agglutinogens).

As a part of our body defense system (immune system) some WBCs (lymphocytes) secret proteins called antibodies (agglutinins).

Antibodies can bind to antigens

Destroy RBCs

A blood group has A antigen which is shown as IA and antibodies for B.

Blood group B has B antigen which is shown as IB and antibodies for A.

O has no antigen and is shown as ii. It has antibodies for A and B.

A person with A may hve got gene A from each parent (IA IA ) or A from One parent and O gene from the other (IA i).

A person with group B is (IBIB) or (IBi).

A person with O group has got O gene from each parent (ii).

A person with AB blood group has got A gene from one parent and B gene from the other (IAIB).

GentotypingHere the normal genetic roles of inheritance applies:

Note that A and B aredominants and O is alwaysrecessive.

Genotyping of the blood groups

A O B O

A O A B B O O O

Transfusion reactions

Blood from a donor is usually checked by recipient serum.

A accepts A and O, but makes clot with B.

B accepts B and O, but clots with A.

AB accepts A, B and O and called universal recipient.

O can be given to A, B and AB and called universal donor.

O accepts only from O and clots with A and B because it has antibodies against them.

anti A anti B anti D-

If the donor is A and the recipient is B then agglutination will occur.

Blood typing Rhesus factor

Another group of antigens found on RBCs surface is called Rh factor. People who have this antigen on their RBCs are Rh positive (Rh+). People without Rh antigen are Rh negative (Rh-).

The Rh factor is very important when Rh- mother gives birth to Rh+ babies.

Rh- Mother

Rh+ Baby

RBC

RBC

1st pregnancy

No mixing of blood

Delivery

Bloods mixes

Anti-Rh+

Rh- Mother

Rh+ Baby

RBC

RBC

2nd pregnancy

Mother has antibodiesAgainst baby RBCs

Next pregnancy Anti-Rh+