7a. Human Transport System: Blood

Question 1

Blood Plasma

Composition & Function

Answer 1

Composistion:

• Plasma is a yellowish fluid made of 91.5% water and 8.5% solutes.
• Solutes include dissovled food substances (glucose, amino acids, lipids), mineral salts, O₂, CO₂, metabolic waste, plasma proteins, hormones and antibodies.

Function:

• Transports dissolved substances (mentioned above) and blood throughout the body.
• Maintains homeostasis of body (optimum pH, water potential & temperature of blood).

Question 2

Red Blood Cells (Erythocytes)

Function & 4 Structural Adaptations

Answer 2

Function:

• Transports oxygen to body cells and carbon dioxide away from body cells.

Structural adaptations:

1. Presence of haemoglobin: which combines with oxygen reversibly to form oxyhaemogoblin, to enable red blood cells to transport oxygen from the lungs to all cells in the body.
2. Circular, flattened biconcave disc: increases surface area to volume ratio to increase rate of diffusion of oxygen and carbon dioxide.
3. Absence of nucleus: allows more haemoglobin to be packed in the cell.
4. Elastic, flexible and can turn bell-shaped: to be able to squeeze through blood vessels smaller than itself in diameter without breaking.

Question 3

White Blood Cells (Leucocytes)

Function & Types

Answer 3

Function:

• Protect the body against disease-causing organisms.

Types of leucocytes:

1. Phagocytes
2. Lymphocytes

Question 4

Phagocytes

Structure & Function

Answer 4

Structure:

• Irregular in shape
• Lobed nucleus

Function:

• Englufs and ingests foregin particles such as bacteria by phagocytosis

Phagocytosis is the process of engulfing and ingesting foreign particles.
In the process, some phagocytes are killed with the bacteria, forming pus.

Monocytes transform into macrophages to carry out phagocytosis

Question 5

Lymphocytes

Structure & Function

Answer 5

Structure:

• Round in shape
• Large nucleus

Function:

• Lymphocytes are stimulated when pathogens or disease-causing organisms enter the bloodstream, to produce antibodies to protect the body against bacteria by:

1. Agglutination: causing pathogens to clump together and attract phagocytes to engulf the clumped bacteria by phagocytosis
2. Neutralise harmful toxins produced by pathogens

Immunisation or vaccination directly induces lymphocytes to produce antibodies by exposing a person to dead or weakened forms of the pathogen

Question 6

Platelets (Thrombocytes)

Structure & Function

Answer 6

Structure:

• Membrane-bound bodies without nucleus (not considered cells)

Function:

• Prevent excessive blood loss
• Prevent the entry of pathogens

Question 7

Mechanism of Blood Clotting

Process + What do undamaged blood vessels contain?

Answer 7

1. When blood vessels are damaged, damaged tissue and platelets produce thrombokinase (enzyme).
2. Thrombokinase converts prothrombin into thrombin (enzyme).
3. Thrombin converts soluble fibrinogen into insoluble fibrin threads that trap blood cells and the whole mass forms a clot or a scab.

Undamaged blood vessels contain an anti-clotting substance called heparin.
When thrombokinase is relased in damaged tissues, it neutralises heparin so clotting can take place.

Question 8

Blood Groups A, B, O, AB

Antigens present on RBC & Antibodies present in blood

Answer 8

Blood Group A:

• Antigen A
• Anti-B antibody

Blood Group B:

• Antigen B
• Anti-A antibody

Blood Group O (Universal Donor):

• No antigen
• Anti-A & anti-B antibodies

Blood Group AB (Universal Acceptor):

• Antigens A & B
• No antibodies

Question 9

Blood Transfusion

Incompatible transfusions

Answer 9

Incompatible transfusions can result in agglutination of red blood cells, when antibodies in the recepient’s blood binds onto antigens on donated red blood cells.
Released haemoglobin may cause kidney damage.

The reaction between the donor’s antibodies in plasma and the recepients antigens on red blood cells is not singificant as the donor’s antibodies are diluted in the recepient’s plasma.

Question 10

Blood Transfusion

Universal Donor & Universal Acceptor

Answer 10

Universal Donor: Blood Group O

• No antigens on the donor’s red blood cells, thus the recepient’s antibodies would not cause agglutination of the donor’s blood.

Universal Acceptor: Blood Group AB

• No antibodies in the plasma of the recipient, which could cause agglutination of the donor’s blood.

Question 11

Blood Typing

Anti-A serum & Anti-B serum

Answer 11

Anti-A serum (contains Anti-A antibody): if blood agglutinates when serum used, red blood cells contain antigen A

Anti-B serum (contains Anti-B antibody): if blood agglutinates when serum used, red blood cells contain antigen B