Topic 11: Human Health and Physiology

11.3 The Kidney

11.3.1 Define excretion

11.3.2 Draw and label a diagram of the kidney

11.3.3 Annotate a diagram of a

glomerulus and associated nephron to

show the function of each part

11.3.4 Explain the process of ultrafiltration, including blood pressure, fenestrated blood capillaries and basement membrane

11.3.5 Define osmoregulation

11.3.6 Explain the reabsorption of

glucose, water and salts in the proximal

convoluted tubule, including the roles of

microvilli, osmosis and active transport.

11.3.7 Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water balance of the blood

11.3.8 Explain the difference in the

concentration of proteins, glucose and

urea between the blood plasma,

glomerular filtrate and urine

11.3.9 Explain the presence of glucose in untreated diabetic patience

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

11.3.2 Draw and label a diagram of the kidney

http://www.ib.bioninja.com.au/_Media/kidney_med.jpeg

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

efferent vessel – takes blood away from the glomerulus

glomerulus – performs ultrafiltration

Bowman's capsule – receives the filtrate 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

distal convoluted tubule – the reabsorption of salt

collecting duct – reabsorption of urea, salt and water. Regulated by the hormone ADH

11.3.4 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).

11.3.4 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.

11.3.6 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

11.3.6 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

11.3.7 Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water

balance of the bloodLoop 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

11.3.7 Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water

balance of the bloodThe 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

11.3.7 Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water

balance of the bloodThe 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

11.3.7 Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water

balance of the bloodMedulla

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

11.3.7 Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water

balance of the bloodCollecting 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

11.3.7 Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water

balance of the bloodCollecting 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)

11.3.7 Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water

balance of the bloodWhen 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.

11.3.8 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

11.3.8 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

11.3.8 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

11.3.8 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

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