1. Topic 11: Human Health and Physiology
11.3 The Kidney

2. Define excretion
Explain the reabsorption of glucose, water and salts in the proximal convoluted tubule, including the roles of microvilli, osmosis and active transport.
Draw and label a diagram of the kidney
Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water balance of the blood
Annotate a diagram of a glomerulus and associated nephron to show the function of each part
Explain the process of ultrafiltration, including blood pressure, fenestrated blood capillaries and basement membrane
Explain the difference in the concentration of proteins, glucose and urea between the blood plasma, glomerular filtrate and urine
Define osmoregulation
Explain the presence of glucose in untreated diabetic patience

3. 11.3.1 Define excretion 11.3.5 Define osmoregulation
Excretion - the removal of waste products that are a result of metabolic processes
characteristic of all living things
Osmoregulation - The control of water balance of the blood, tissue and cytoplasm of an organism
Water moves from the filtrate into the body tissue in two places
The Loop Henle – through osmosis
The collecting duct – hormonally controlled

4. 11.3.2 Draw and label a diagram of the kidney

5. 11.3.3 Annotate a diagram of a glomerulus and associated nephron to show the function of each part
afferent vessel – takes blood to the glomerulus
glomerulus – performs ultrafiltration
distal convoluted tubule – the reabsorption of salt
Bowman's capsule – receives the filtrate from the glomerulus
efferent vessel – takes blood away from the glomerulus
proximal convoluted tubule – the location of most of the reabsorption of water, glucose and salt
Loop of Henle – location of the reabsorption water and transport of salts
collecting duct – reabsorption of urea, salt and water. Regulated by the hormone ADH

6. Explain the process of ultrafiltration, including blood pressure, fenestrated blood capillaries and basement membrane
The main purposes of the nephron are:
Ultrafiltration
Selective reabsorption
secretion
Ultrafiltration
in the glomerulus, water and small useful molecules (glucose, amino acids, ions) are forced out of the capillaries and into the lumen of the bowman’s capsule
The force is cause by blood pressure because the afferent capillary (input) is larger than the efferent capillary (output).

7. Explain the process of ultrafiltration, including blood pressure, fenestrated blood capillaries and basement membrane
The capillaries are called fenestrated capillaries because they have small holes to allow some substances to pass through
Glucose, water, salts, urea, amino acids and proteins CAN pass through
Erythrocytes, leucocytes and platelets CANNOT pass through
There is a second layer called the basement membrane and the third layer is composed of cells called podcytes. They are also fenestrated
This is the second level of filtration and do not let larger plasma proteins to pass into the filtrate.
The filtrate continues through the nephron where selective reabsorption occurs.

8. Explain the reabsorption of glucose, water and salts in the proximal convoluted tubule, including the roles of microvilli, osmosis and active transport.
The fluid in the proximal convoluted tubule is very similar to the blood plasma (glucose, amino acids, vitamins, hormones, urea, salt, ions and water)
Most reabsorption takes place here
All of the following are reabsorbed into the blood:
Glucose
Hormones
amino acids
Vitamins
Water
Salts

9. Explain the reabsorption of glucose, water and salts in the proximal convoluted tubule, including the roles of microvilli, osmosis and active transport.
Osmosis is the force that allows water to be reabsorbed
It follows the active transport of glucose and Na+
Glucose and amino acids follow by co-transport
Cl- is passively transported
There are many mitochondria to supply the energy needed for active transport
The interior of the proximal convoluted tubule contain microvilli to increase surface area and to maximize reabsorption

10. Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water balance of the blood
Loop of Henle
The Loop of Henle consists of the descending and ascending limb
In the descending portion of the loop of Henle water exits the nephron by osmosis due to the increasing concentration of salt.
The walls of the descending limb are impermeable to Na+
This water is immediately passed into the capillaries and taken from the kidneys

11. Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water balance of the blood
The ascending limb of the loop of Henle is impermeable to water
Salt is passed into the medulla from the filtrate by active transport
The amount of salt that is actively transported in the ascending limb is more than diffuses into the descending limb

12. Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water balance of the blood
The salt remains in the medulla in this area of the loop of Henle to maintain the concentration gradient in the medulla
The filtrate that leaves the loop of Henle is less concentrated than the tissue in the medulla

13. Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water balance of the blood
Medulla
The concentration gradient of the medulla is maintained by “vasa recta countercurrent exchange”
There is no direct exchange between filtrate and blood, but instead, the substances pass through the interstitial region of the medulla

14. Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water balance of the blood
Collecting duct
Collecting duct is where the water content of the blood is regulated by the hormone ADH (antidiuretic hormone).
When water content in the blood is low antidiuretic hormone (ADH) is secreted from the posterior lobe of the pituitary gland
When water content is high no ADH is secreted

15. Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water balance of the blood
Collecting duct
Collecting duct is where the water content of the blood is regulated by the hormone ADH (antidiuretic hormone).
The walls of the collecting duct are variably permeable caused by the presence of ADH
When water content in the blood is low (you’re thirsty) antidiuretic hormone (ADH) is secreted from the posterior lobe of the pituitary gland.
Aquaporin channels in the cells of the collecting duct open and allow water to enter back into the blood (keep blood in your body)

16. Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water balance of the blood
When water content is high (you drank too much water) no ADH is secreted by the pituitary gland
A large amount of dilute urine is formed
If you drink too much alcohol it suppresses ADH secretion and you have to pee.

17. Explain the difference in the concentration of proteins, glucose and urea between the blood plasma, glomerular filtrate and urine
The composition of our urine is very variable depending on things like diet, exercise, environmental conditions, etc...
However, blood must stay at a constant composition

18. Explain the difference in the concentration of proteins, glucose and urea between the blood plasma, glomerular filtrate and urine
Blood
Blood in the renal artery contains more salts, urea and sometimes water than is necessary
Blood leaving the kidney from the renal vein contains optimum amounts of water, salts, and little urea

19. Explain the difference in the concentration of proteins, glucose and urea between the blood plasma, glomerular filtrate and urine
Glomerular filtrate
Similar to blood plasma minus the large proteins

20. Explain the difference in the concentration of proteins, glucose and urea between the blood plasma, glomerular filtrate and urine
Urine
Urine contains less water, less salt and no proteins, no glucose and no amino acids
But contains more urea than the glomerular filtrate

21. 11.3.9 Explain the presence of glucose in untreated diabetic patience
Since diabetics are unable to absorb glucose into the cells, large quantities of glucose can occur in the blood
The kidney cannot reabsorb such high levels and some of the glucose is passed out of the body in the urine