1. HGH produced in pituitary gland
B5: The living body
Growth: Plants
Plants grow continuously throughout their lives.
They grow at certain points called MERISTEMS, in the tips of the roots and shoots.
Growth: Animals
Animals grow in the early stages of life, and stop growing at a certain point. In humans, generally around age 18.
Animals grow by a process of cell division called MITOSIS. This is when a cell reproduces itself by splitting to form two identical offspring.
Human Growth Hormone is produced in the Pituitary Gland in the brain. It stimulates growth, especially in long bones.
HGH produced in pituitary gland
Liver
IGF-1
Indirect
Indirect effect: HGH sent to the liver, where IGF-1 is then produced, which triggers increased production of cartilage in the long bones, resulting in increase in length.
Direct effect: Stops fat being stored in cells and releases it for energy and growth.
Other factors affecting growth are diet (protein for muscle growth, calcium and Vit D for bones), exercise (makes body release more growth hormone), genetics, health and disease.
Direct

2. Transplants
Mechanical Replacements
Biological Replacements
Knee joint
Hip joint
Heart
Lens of Eye
Kidney
Lungs
Bone marrow
Heart and lung machines (used during an operation), iron lungs (used to be used for sufferers of polio) and kidney dialysis machines are outside of the body.
With mechanical replacements, there can be problems such as;
Size – must fit in the place of the original organ
Power supply – battery would have to be replaced
Material – must not react with substances in the body
With biological replacements, there can be problems such as;
Size – must fit in the place of the original organ
Tissue must match, same blood type etc.
Shortage of donors on the register.
Organs can also be ‘rejected’ by the body, as they are seen as a foreign tissue. This means that the patient must take immuno-suppressant drugs to ensure this does not happen.

3. The Kidney aorta Vena Cava – returns blood to heart
Aorta – brings blood form heart
Renal artery – blood to kidney containing urea (made in liver from amino acids in protein)
Renal Vein – blood away from kidney
Ureter – urine from kidney taken to bladder
Bladder – temporary store for urine
The tubule, the structure of which is a NEPHRON, filters the blood. The Glomerulus is a collection of blood capillaries. An area of high pressure is built up which squeezes small molecules (water, urea, sugar) out of the blood – ULTRAFILTRATION. Big molecules like protein and red blood cells stay in the blood. As this liquid flows through the nephron, selective reabsorption occurs. Water, sugars and ions are absorbed actively against the concentration gradient.
The waste liquid left is urine, and this is taken to the bladder via the ureter.
Tubule

4. Water Regulation
Depends on how porous the collecting duct wall is. This is controlled by ANTI - DIURETIC HORMONE.. A negative feedback mechanism ensures that water levels are regulated.
Water lost
by sweating
Concentration of blood increases.
Sensed by receptors in hypothalamus
ADH produced
Walls become porous
Lots of water reabsorbed. Concentrated urine.
Water gained from drinking
Concentration of blood decreases.
Sensed by receptors in hypothalamus
ADH stops being produced
Walls become not porous
Little of water reabsorbed. Dilute urine.

5. Kidney Dialysis
If the kidneys have stopped working, the patient may receive dialysis treatment. The machine acts as an artificial kidney, removing urea from blood.
Urea molecules are small, and diffuse through the artificial membrane. The dialysis fluid is like normal blood plasma, so levels of Na and C6H12O6 remain the same.
HAEMODIALYSIS is when the person goes on a dialysis machine for 9 hours 3 times a week.
PERITONEAL DIALYSIS is when the dialysis takes place all day every day while the person goes about their daily lives.