Functions of Blood

• Transport of dissolved substances

• Regulation of pH and ions

• Restriction of fluid losses at injury sites

• Defense against toxins and pathogens

• Stabilization of body temperature

The Composition of Whole Blood

• Blood volume (liters) = 7% of body weight

– Adult male: 5 to 6 liters

– Adult female: 4 to 5 liters

• Three General Characteristics of Blood

– 38°C (100.4°F) is normal temperature

– High viscosity

– Slightly alkaline pH (7.35–7.45)

Plasma Is the Fluid Part of Blood

• Plasma = 55% of whole blood– Made up of mostly water (92%)– Other substances (8%)– Used to transport:

• Blood cells and platelets• Proteins• Hormones• Ions• Nutrients, e.g., sugars and amino acids• Various gases

The Composition of Whole Blood• Three Types of Cells (makes up

45% of whole blood)– Red blood cells (RBCs): Transport

oxygen.• The oxygen binds to a special iron based

protein called hemoglobin found on the RBC.

– White blood cells (WBCs): Part of the immune system.

– Platelets: Cell fragments involved in clotting.• Clotting: The process of plugging a

damaged blood vessel to decrease blood loss.

Production of Red Blood Cells

• They are produced in the red bone marrow found in certain bones in our body (arms, legs, hips)– They mature from stem cells found inside

the bones.• In a healthy person RBC count is

between 4-6 million RBC/ml of blood.• RBC live for about 120 days.

How Clotting Works

Blood Typing

• There are 4 different blood types individuals can have A, B, O, and AB.– They are genetically determined.

• To determine which blood type is present you have to look at the cells membrane’s proteins.– These surface proteins are called antigens.– Each blood type has its own specific combination of antigens

present.– Your body cells are able to tell the difference between your

antigens and someone else’s antigens.– If you body recognizes the antigens a foreign (called non-self

antigens) it will cause an immune response and try to destroy the non-self cells.

Blood Typing• Based on your specific blood type your body will also

have antibodies (a special type of white blood cell destroys foreign antigens) floating in your blood that are looking for antigens that do not match your special combination.

• For example: if you have type A blood, you have antigens on your cells that represent type A blood.– You also have antibodies called Anti-B antibodies.– These antibodies are looking for cells that have the B antigen

present on their cells, and if it recognizes them the antibody sees those cells as foreign because they do not match your red blood cells, so those antibodies will try to kill the cells.

Blood Types and Cross-Reactions

Blood Types and Cross-Reactions• If your body reacts to foreign cells that do not match

yours the immune reaction that occurs is called agglutination (which is clumping or clotting that occurs in the body).– It can be dangerous and cause death.

Blood Typing• In addition to the blood types A, O, AB and B an

additional factor is taken into account called the Rh factor.– The Rh Factor, also called the D antigen determines

positive vs. negative blood types.• For example someone that has both the A antigen and

the Rh antigen as an A+ blood type.– If someone has the A and B antigens but no Rh antigen they

have an AB- blood type.• Individuals that are Rh negative also have an extra

antibody present called the anti-Rh antibody that looks for cells that have the Rh antigen.

Red Blood Cell Disorders

• Anemia: occurs when there is not enough RBC to deliver oxygen to the body.– May be due to:• Low RBC count (like donating blood or loosing a lot of

blood)• Abnormal hemoglobin• Abnormal shape of cell

(like sickle cell anemia)