Biology Notes: Transport in humans

General Overview:

Diffusion is not viable in large organisms. A transport system is necessary for humans. 2 types of systems: blood system and lymphatic system. Blood system transports blood. Blood consists of plasma, blood cells(corpuscles) and platelets.

Composition of blood:

Plasma

Soluble proteins such as fibrinogen, prothrombin and antibodies.o Fibrinogen and prothrombin aid in blood clotting.o Antibodies help fight diseases.

Dissolved mineral salts.o Bicarbonates, chlorides, sulfates and phosphates of calcium, sodium and potassium.o These exist as ions in the plasma.o Calcium is essential for blood clotting.

Food substances.o Glucose, amino acids, fats and vitamins.

Excretory products.o Urea, uric acid and creatinine.o Carbon dioxide is present as bicarbonate ions.

Hormones.o Insulin.

The amounts of soluble proteins, mineral salts and glucose in the blood plasma are kept relatively constant.

Red blood cells/Erythrocytes

Contain hemoglobin, an iron-containing pigment which combines with oxygen.o This enables transport of oxygen around the body.

Circular, flattened and biconcave.o This increases the cell’s SA:V ratio. Absorption and release of oxygen occurs at a

faster rate. Have no nucleus. Elastic.

o Can squeeze through narrow blood vessels.

Red blood cells are produced by bone marrow and are broken down by the spleen. Hemoglobin is broken down by the liver.

White blood cells/Leucocytes

Two main kinds of white blood cells: Lymphocytes and Phagocytes.o Lymphocytes are produced by the bone marrow and mature in the lymph nodes.o They produce antibodies to protect the body from microorganisms.o Phagocytes ingest foreign particles such as bacteria.o This process is known as phagocytosis.o Phagocytosis is aided by antibodies.o The dead phagocytes and bacteria form pus.o Lymphocytes have a rounder nucleus while phagocytes have lobed nuclei.

White blood cells help the body fight diseases.

Blood platelets/Thrombocytes

Not true cells. Aid in blood clotting.

Blood Groups

Blood groups are important when considering blood transfusions. Agglutination (clumping) of blood cells can occur if the blood groups are not compatible.

Agglutination occurs when antibodies from the recipient’s blood react with antigens on the red blood cells of the donor’s blood.

There are 4 blood groups: A, B, AB and O.

Antigens and antibodies present in the groups:

Blood Groups Antigen on RBC Antibody in serumA antigen A antibody bB antigen B antibody a

AB antigen A and B no antibodiesO no antigen antibodies a and b

Transfusion possibilities:

Recipient’s blood group

Antibody in recipient’s

serum

Donor’s blood groupA (antigen

A)B (antigen

B)AB (antigen

A & B)O (no

antigens)A b - + + -B a + - + -

AB no antibodies - - - -O a and b + + + -

Functions of blood

Transport

Digested food substances from capillaries in the small intestine to all parts of the body. Excretory products from the tissues to the excretory organs.

o Nitrogenous waste (urea, uric acid & creatinine) are removed by the kidney.o Carbon dioxide is expelled from the lungs in exhalation.

Hormones from glands. Oxygen, combined with hemoglobin in red blood cells.

o Hemoglobin has a great affinity for oxygen.o Oxygen binds reversibly with hemoglobin to form oxyhemoglobin.o This gives oxygenated blood the bright color.o This is affected by carbon monoxide.o Carbon monoxide bonds irreversibly with hemoglobin to form carboxyhemoglobin.o This prevents red blood cells from transporting oxygen.o At high altitudes, the concentration of oxygen in the atmosphere is lower.o The body must produce more red blood cells to compensate for the less oxygen.o This is known as acclimatization.

Heat produced in respiration, maintains uniform temperature.

Protection

Clotting/Coagulation of bloodo Clotting prevents excessive loss of blood as well as foreign particles from

entering the bloodstream.o Damaged tissues and platelets secrete thrombokinase.o Thrombokinase converts prothrombin to thrombin. This is catalyzed by Ca2+ ions.o Thrombin converts fibrinogen into insoluble fibrin threads.o Fibrin threads entangle blood cells which form a clot.o The liquid left behind is serum.o The inability to form a blood clot is hemophilia.o In undamaged vessels, heparin prevents clotting. Thrombokinase neutralizes

heparin.

Tissue Rejection

Tissue rejections occur when the tissues of the recipient and the donor do not match. Tissue rejection causes the recipient’s immune system to attack the donated tissue. Tissue rejection can be prevented in two ways.

o Tissue matching reduces the risk of rejections. The donor should be as genetically close as possible. Close relatives are likely to have similar genes.

o Immunosuppressive drugs also reduce the risk of rejection. However, the recipient has lower resistance to infection and the drugs have to be taken for the rest of the recipient’s life.