2.75 Urine

2.75 recall that urine contains water, urea and salts

Urine contains:
- Salts
- Water
- Urea
Amount varies on the condition a person is operating

Salt + H2O affects the composition of tissue fluid
[Osmoregulation]

Urea - Excretion of metabolic waste

2.74 ADH

2.74 describe the role of ADH in regulating the water content of the blood

Anti diuretic hormone - ADH

Produced in the hypothalamus
- Flows to the bloodstream
- Target is the kidney

Effect of ADH
- Control and alter the quantity of water in the blood
- Ability to make the blood more or less concentrated
- Tissue fluid needs to be isotonic with the cytoplasm of the cell

ADH targets the collecting duct
- Allows more water to come out of the collecting duct
- Collecting duct ===selective reabsorption===> Blood
         - ADH makes collecting duct walls more porous
- Water goes back into the blood

Consequence of ADH secretion
- Urine more concentrated
- Lower volume

ADH response to hot days, cold days, dehydration

2.73 Glucose reabsorption

2.73 understand that selective reabsorption of glucose occurs at the proximal convoluted tubule

Selective reabsorption of glucose
Reabsorption - Glomerular filtrate => Blood

End of the nephron: Urine
- Normally urine does not have glucose
- If there is glucose in the urine - diabetes

Proximal convoluted tubule (first)
- Glucose is removed
- Taken back into the blood

2.72 Water reabsorption

2.72 understand that water is reabsorbed into the blood from the collecting duct

Bowman's Capsule - location of ultrafiltration

Dissolved contents of the blood are forced into glomerular filtrate
When filtration occurs - will filter out too much water therefore selective reabsorption occurs

Selective reabsorption of water occurs in the collecting duct:

Filtrate reaches the collecting duct
- Water is removed from the filtrate
- Returned back into the blood vessels
- Back into the bloodstream
- Selected and reabsorbed into the blood

2.71 Ultrafiltration

2.71 describe ultrafiltration in the Bowman’s capsule and the composition of the glomerular filtrate

Nephron - Structure which carries out the filtration of blood

Produces:

- Filtered blood ("cleaned blood")

- Urine (the waste)

Urine - Water (H2O), salts, urea (N)

Beginning of the nephron structure begins at the Bowman's capsule

Where ultrafiltration begins

Filtration of blood:

1. Blood arriving in the kidney

Afferent arteriole

High pressure (come from an artery)

2. Blood leaving the kidney

Efferent arteriole

Narrow blood vessel (smaller than afferent arteriole)

3. Afferent ==> Efferent

Blood develops a high pressure

Blood pressure increases in glomerulus

4. High pressure forces the liquid in blood (plasma, which includes H2O, salts, amino acids, glucose, urea) into the inside of the Bowman's capsule (and consequently into the glomerula filtrate)

5. Glomerula filtrate

Plasma contains H2O, salts, amino acids, glucose, urea

Blood has been filtered by high pressure

Forces the liquid into the tube

Source: http://click4biology.info/c4b/11/11.3/glomerulus.gif

2.70 Nephron Structure

2.70 describe the structure of a nephron, to include Bowman’s capsule and glomerulus, convoluted tubules, loop of Henlé and collecting duct

Nephron - functional unit of the kidney (filtration, controlling of composition of blood)

Aorta - taking blood into the kidney (renal artery)
Urine goes down into the ureters and into the bladder for excretion
Filtered blood goes back into the bloodstream through the renal vein (returns to the vena cava)

- Cortex
- Medulla
- Pelvic region - Space where the urine collects and drains down into the ureter

Kidney made up of millions of tubular structures (nephrons)
Tube starts on the edge of the medulla - dead end structure shown in diagram

Bowman's capsule - the dead end structure

Nephron - Tubular structure

Convoluted tubules - twisted sections
Dip in the nephron - Loop of Henlé

Bowman's Capsule - contains tight knot blood vessels [Glomerulus]

First twisted section - PCT (Proximal convoluted tubules)
Second twisted section - DCT (Distal convoluted tubules)

Source: http://www.beltina.org/pics/nephron.jpg