Cross section of a kidney - Taken in biology class dissection.

2.75 Urine

Key Points:
1. ADH influences the kidneys filtration of blood, in which more water may be retained.
2. Urine contains salts, water and urea.
3. The salts and h2o affect the composition of tissue fluid which is called osmoregulation (isotonic, hypertonic and hypotonic states)
4. The composition of urine varies upon the conditions in which a person is operating.

2.74 ADH

Key Points:
1. ADH = Anti Diuretic Hormone. ADH is produced in the hypothalomus of the brain. This flows through the blood stream and targets the kidney.
2. The effect of ADH is to control and alter the composition of water which is in blood. ADH has the ability to make the blood more or less concentrated. This is important because of the dangers of not having isotonic status.
3. ADH targets the collecting duct, where the water goes out, and the effect of ADH is that it allows more water to exit the collecting duct.
4. The collecting duct is responsible for the recycling of blood back into the bloodstream. ADH makes the collecting duct walls more porous, so the water can escape easier.
5. The consequence of the ADH secretion is that the urine would be more concentrated with a less volume. ADH secretion causes this.

On a hot day we lose water through sweat, and this means less water will be in the blood when it goes to the kidneys for ultrafiltration. As there is less water already, the ADH response would most likey be more than usual, causing us to retain more water and recycle it back into the blood stream. This is probably amplified with dehydration, as the loss of water through urine may be a life/death scenario, so it is probably likely that the ADH will have a greater effect upon the recycling of water, and more water will re-enter the bloodstream so that our bodies can keep going.
This is probably the opposite with a cold day.

2.73 Glucose Re-absorption

Key Points:
1. Selective reabsorption means the molecule is selected, and is reabsorbed from the glomerula filtrate back into the blood.
2. The filtration occurs in the Bowmans Capsule. In the formation of the fluid, high pressure, glucose is in the plasma which is then known as the filtrate.
3. Water is removed back into the blood via the collecting duct. At the end of the nephron is the urine, and normally urine doesn't contain glucose. If glucose is present in the urine, then that is a condition known as diabetes.
4. Glucose is in the filtrate at the proximal convoluted tubule, and then it is removed and is taken back into blood. Glucose is selectively reabsorbed into the blood via the proximal convoluted tubule.

2.72 Water re-absorption

Key Points:
1. In the Bowmans capsule, ultrafiltration takes place. The blood goes into the kidney under high pressure, and the plasma is forced into the bowmans capsule tube, or the glomerula filtrate, and this contrains glucose water, salts and urea. When the filtration occurs, too much water is filtered.
2. As the filtrate passes along the tubule, when it reaches the collecting duct, what happens is that water is removed from the filtrate.
3. That water is returned back to blood vessels.
4. The water has been selected and has been re-absorbed into the blood, or selective re-absorption.

2.71 Ultrafiltration

Key Points:
1. The diagram is of the nephron, and this is the part of the kidney that filters our blood. And the waste product is urine. The urine emerges from the bottom of the tubule. Urine is composed mostly of water, salts, and urea.
2. Urine is formed by a process. This starts in Bowmans capsule, and the process is known as ultrafiltration. The filtration of blood begins with blood in the kidney. When the blood enters the kidney it has a high pressure, and the blood enters a series of capsules known as the glomerialis, made up of smaller blood capsules. As the blood leaves, it goes through a blood vessle coming out of the bowmans capsule, and the diameter of this blood vessel is smaller. This is so that the blood pressure increases.
3. The high pressure forces the liquid within blood, plasma, and plasma contains all the useful things in blood such as salts urea glucose. These are all forced out of the blood vessel and into the inside of the Bowmans Capsule. The plasma becomes known as the filtrate, the glomarelia filtrate.

2.70 Nephron Structure

Key Points:
1. The nephron is the functioning area of the kidney. The Aorta passes by the kidneys, and the artery that branches off and connects to the kidney is called the renal artery. The kidney filters the blood, and the excretion is called urine. This is collected in the bladder and prepared for release.
2. The vein carrying the filtered blood from the kidney to the bladder is called the renal vein. The renal vein eventually returns to the vena cava.
3. If the kidney was sliced across exposing the different layers of the kidney, different things would be seen. The outer lighter region is called the cortex, and the inner region is called the medulla. The space at the very edge of the kidney is called the pelvic, and this is where the urine collects. The reason for the different colours is because the kidney is made of many tubular structures. The dead end structure is known as the bowmans capsule.
4. In more detail, the tube structure is known as a nephron. In the diagram, the dotted line shows the separation between cortex and the medulla. The tube is made up of twisted sections, convoluted tubules, and the tube on the end is known as the collecting duct. The tube dips back down into the medulla, and this is known as the loop of henele. This returns back to the cortex and comes to the dead end structure, Bowmans Capsule.
5.The tight knot of blood capsules around Bowmans Capsule is known as the glomarialis. The first twisted section is known as the proximal convoluted tubule, and the second section is known as the distill convoluted tubule