THE CIRCULATORY SYSTEM

Objectives:1. Explain the functions of the circulatory system2. State the main components of the circulatory system.3. Describe the structure and function of blood4. Know what types of blood are compatible with each

other and why.

Three Main Components of the Circulatory System

1. Fluid in which materials are transported (i.e. blood)

2. Vessels to provide controlled paths (i.e. veins, arteries, capillaries)

3. A pumping device to move the fluid around (i.e. heart)

BLOOD: IT’S ALIVE!- An average adult has 5L of blood

Function of Blood

1.Transports oxygen and nutrients to cells2. Transports carbon dioxide and wastes away

from cells3. Helps maintain homeostasis:

– Transports chemical messages throughout the body (ex. hormones),

– helps maintain acceptable fluid levels, – helps maintain a constant temperature

4. Is part of the immune system, used to transport immune cells throughout the body

Components of Blood

Blood cells are produced from stem cells in your bone marrow

1) Erythrocytes (RBC’s)• Made in the bone marrow• Destroyed in liver and spleen• Contain gas-binding haemoglobin

and iron; carry O2( combines with Fe) and CO2

• No nucleus or mitochondria• Blood types: different glycoproteins

on cell surface

•FOUR blood types: A, B, AB and O•Surface ANTIGENS or markers consisting of

glycoproteins (proteins with attached polysaccharides), are found on the plasma membranes of red blood cells

•There are two types of surface antigens, A or B

•The presence or absence of antigens A and B on the plasma membrane of the rbc of a person, determines that person’s blood type

•The body’s own blood type antigen(s) is recognized by the immune system as “self”, but other blood type antigens will be considered “non-self” by the body’s immune system

•Within the blood plasma there will be ANTIBODIES to the opposite blood type

•These antibodies have a complementary shape to the antigen and will bind to it.– eg. A person with antigen A on their red blood

cells will have antibody B (Anti-B) in the plasma – A person with antigen B on their red blood cells

will have – antibody A (Anti–A) in the plasma

BLOOD TYPE ANTIGEN ON RBC’s ANTIBODY IN PLASMA

A

B

AB

O

A B

B A

AB NONE

NONE AB

•When incompatible blood types combine, agglutination or clumping of red blood cells will occur.

•The antibodies present in the recipient’s plasma will attack and bind to the donated red blood cells’ antigens clumping the red cells together and preventing them from circulating.

•This creates blockages in small capillaries•For a donation to be successful, the

recipient’s plasma must NOT have an antibody that causes the donor’s cells to agglutinate.

Blood Types

Blood Type Can Receive

A

B

AB

O

 (NOTE: the antibodies in the plasma of the donor are not considered since they are very diluted during the transfusion and do not cause clumping.)

A and O

B and O

A, B, AB and O

O

•Another surface antigen important in blood typing is the Rh factor or Rhesus factor

•Rh+ means the antigen is present on red blood cells (85% of people)

•Rh – means the antigen is absent on red blood cells (15% of people)

 •e.g. type B+ means type B blood with the Rh factor present

• Rh+ has Rh antigen• Therefore Rh+ has no Rh antibodies.

• Rh- has no Rh antigen• Therefore Rh – has Rh antibodies.

• THEREFORE…– Rh+ can donate to Rh+ only– If Rh+ donated to Rh- the Rh antibodies in Rh- blood would

attack the antigens in the Rh+ blood being donated.– Rh- can donate to Rh- and Rh+ because Rh- has no

antigen to be attacked and Rh+ has no antibodies to do the attacking.

Blood Type Can ReceiveA-A+B-B+

AB-AB+O-O+

A- and O-A+ A- O+ and O-B- and O-

B+ B- O+ and O-A- B- and O-

Universal recipientO-

O+ and O-

2) Leukocytes (white blood cells)• Made in the bone marrow and lymph

nodes• Have a nucleus• Different types• Function: As part of the immune system,

they can produce antibodies to attack pathogens or they can be phagocytic and engulf pathogens.

3) Platelets• Repair wounds by releasing clotting

factors (proteins) to help cells stick together

• No nucleus• Produced in bone marrow

Your Task

• Read and complete the worksheet on ‘Blood and its Components’

• H/W complete worksheet on Blood Typing

Plenary

1. What is the function of blood?2. Name the two major components of blood.3. What is the function of hemoglobin?4. What is the function of red/white blood cells?5. What is an antigen/antibody?6. What is the difference between Rh-positive

and Rh-negative blood?7. A person with A- blood is given blood from a

donor with O+ blood. What happens and why?