Module 10
Renal and Urologic System
Anatomy and physiology of the Renal System
1. Discuss the physiologic relationship between phosphorus and calcium.
Calcium
· 99% located in bone as hydroxyapatite
· Remainder in plasma and body cells
· Serves as enzymatic cofactor for blood clotting
· Required for hormone secretion and function of cell receptors
· Transmission of nerve impulses and contraction of muscles
Phosphorous
· 85% in bone
· Smaller amounts in intracellular and extracellular spaces
· Acts as intracellular and extracellular anion buffer in regulation of acid-base
balance
· In form of ATP, provides energy for muscle contraction
If one increases/decreases, the other increases/decreases:
· Regulated by 3 hormones
Parathyroid hormone
Secreted in response to low levels of serum calcium
Stimulates reabsorption of Ca along distal tubule of nephron
Inhibits phosphate reabsorption by proximal tubule of nephron
Net result=increase in serum Ca and increased urinary excretion of phosphate
Vitamin D
Fat soluble steroid ingested in food or synthesized in skin in presence of UV light
1st stage of activation—serum calcium level decreases and stimulates secretion of PTH
· Combination of low Ca and increased PTH causes renal activation of vitamin D
,Activated vitamin D circulates as hormone in plasma and acts to increase absorption of
calcium and phosphate in small intestine, enhance bone calcification, and increase
renal tubular reabsorption of Ca and phosphate
Calcitonin
Produced by C cells in thyroid decrease calcium levels by inhibiting osteoclastic activity
in bone
Released as calcium levels increase, suppression of PTH secretion, decreased renal
vitamin D activation, decreased intestinal calcium absorption, and increased renal
phosphate reabsorption
· Substances work together to determine amount of dietary calcium and phosphate
absorbed from intestine, deposition and absorption of calcium and phosphate from
bone, and renal absorption and excretion of calcium and phosphate by kidney
2. Discuss how calcium and phosphorus homeostasis is altered by renal disease and
the pathologic consequences.
(Page 1368) Bone and skeletal changes develop with alterations in calcium and
phosphate metabolism. These changes begin when the GFR decreases to 25% or less.
Hypocalcemia is accelerated by impaired renal synthesis of 1,25- dihydroxy- vitamin D3
(calcitriol) with decreased intestinal absorption of calcium. Renal phosphate excretion
also decreases and the increased serum phosphate binds calcium, further contributing
to hypocalcemia. Acidosis also contributes to a negative calcium balance. Decreased
serum calcium level stimulates parathyroid hormone secretion with mobilization of
calcium from bone and may cause calcium levels to approach normal. The combined
effect of hyperparathyroidism and vitamin d deficiency can result in renal
osteodystrophies. Other consequences of secondary hyperparathyroidism include soft
tissue and vascular calcification, cardiovascular disease, and less commonly, calcific
uremic arteriolopathy.
3. Examine the basic anatomy and physiology of the kidney.
Kidney Structure
Description of Role and Function:
The kidneys lay in the retroperitoneal space of the abdominal cavity, one on each side
of the spine. The kidneys have multiple functions which include:
the excretion of metabolic waste products
the maintenance of water balance
the regulation of acid base balance
blood pressure regulation
, secretion of erythropoietin which stimulates the growth of red blood cells.
Disorders which affect the kidney may result in a decrease in the production of
erythropoietin resulting in anemia. activates vitamin D. The active form assists
with the absorption of calcium in the intestines. The precursor to vitamin D is
ingested in the food that we eat (vegetables and meat). After it is absorbed it is
taken to the skin where UV light turns it into another precursor of vitamin D. This
precursor then is transported to the kidney where it is converted into the active
form of vitamin D, calcitriol. Calcitriol is then responsible for assisting with the
absorption of calcium in the intestines, promoting the release of calcium from the
bone (resorption), and decreasing renal calcium excretion. Disorders which affect
the kidney can result in a vitamin D deficiency and hypocalcemia.
renal capsule: outer most portion of the kidney and is made of a fibrous tissue.
renal fascia: fatty layer of tissue that adheres each kidney to the posterior wall of the
abdomen.
renal cortex: directly below the renal capsule and extends between the medullary
pyramids and houses the renal corpuscles and the proximal and distal tubules of the
nephron.
renal medulla: pyramid-shaped. It is the inner darker portion of the kidney tissue
consisting of renal pyramids, which contain the secreting and collecting tubules.
renal calyces: extend from the medulla and are responsible for collecting urine from
the medulla. The renal calyces extend from the medulla and merge together to form the
renal medulla.
renal medulla: gives rise to the ureter which extends to the bladder.
Nephron Structure
Nephron Function:
Glomerular Filtration
Filtration Rate
Tubular Transport
Proximal Convoluted Tubule
Loop of Henle and Distal Convoluted Tubules
Description of Role and Function:
Nephron Structure: The nephron is the functional unit of the kidney. There are two
types of nephrons:
1. cortical nephron which is located in the renal cortex
2. juxtamedullary nephron which lays close to and extends into the medulla.
, The nephron has three main functional parts:
1. Glomerulus: The glomerulus is a 2 collection of capillaries which receives blood
from the renal artery and is responsible for filtering the blood.
2. Bowman’s capsule: The bowman’s capsule partially encases the glomerulus
and extends to form the tubule system. Together the glomerulus and bowman’s
capsule are termed the renal corpuscle.
3. Tubular system: The tubule system is a collection of tubules which originate
from the bowman’s capsule.
proximal tubule: comes directly off of the bowman’s capsule and is the recipient of
the filtrate which flows from the glomerulus into the bowman’s capsule and then into the
proximal tubule. The proximal tubule reabsorbs all of the glucose (unless the threshold
for glucose is exceeded) and it reabsorbs amino acids. It also reabsorbs most of the
HCO3, Na, Cl, phosphate, potassium, and water. A serum glucose above 200mg/dL will
exceed the renal threshold for glucose and result in glucosuria and the damage
associated with diabetes mellitus. The proximal tubule when stimulated by the
parathyroid hormone will excrete phosphate. It is also the site of action for angiotensin II
which stimulates Na, water and bicarbonate reabsorption.
descending loop of Henle: extends from the proximal tubule, is impermeable to Na,
passively reabsorbs water and concentrates urine. The ascending loop of Henle
extends from the descending loop of Henle. It actively reabsorbs sodium, potassium
and chloride. It induces the reabsorption of magnesium and calcium and it is
impermeable to water; therefore, it makes the urine more dilute.
distal convoluted tubule: extends from the ascending loop of Henle, actively
reabsorbs Na, is impermeable to water and causes the urine to be more dilute. In the
distal convoluted tubule, the parathyroid hormone increases calcium reabsorption.
collecting tubule: extends from the distal convoluted tubule and connects with the
renal pyramids. It reabsorbs sodium in exchange for potassium and hydrogen. This
process is regulated by the hormone aldosterone, and this is the site of action for
antidiuretic hormone as well. Podocytes are epithelial cells in the bowman capsule
which wrap around the capillaries of the glomeruli. They form long processes (foot
projections) called pedicels which wrap around the glomerular capillaries and leave slits
between them. Blood is filtered through these slits.
juxtaglomerular apparatus (JGA): is located in the area just proximal to the renal
corpuscle, between the afferent & efferent arterioles and where the distal tubule loops
up and makes contact with the afferent arteriole. The JGA is a collection of cells
consisting of the juxtaglomerular cells, the macula densa, and the mesangial cells. The
juxtaglomerular cells are located in the wall of the afferent arterioles. They monitor renal
pressure and help to maintain normal GFR through the release of renin. When renal
perfusion is decreased these cells are responsible for releasing renin to help increase
Renal and Urologic System
Anatomy and physiology of the Renal System
1. Discuss the physiologic relationship between phosphorus and calcium.
Calcium
· 99% located in bone as hydroxyapatite
· Remainder in plasma and body cells
· Serves as enzymatic cofactor for blood clotting
· Required for hormone secretion and function of cell receptors
· Transmission of nerve impulses and contraction of muscles
Phosphorous
· 85% in bone
· Smaller amounts in intracellular and extracellular spaces
· Acts as intracellular and extracellular anion buffer in regulation of acid-base
balance
· In form of ATP, provides energy for muscle contraction
If one increases/decreases, the other increases/decreases:
· Regulated by 3 hormones
Parathyroid hormone
Secreted in response to low levels of serum calcium
Stimulates reabsorption of Ca along distal tubule of nephron
Inhibits phosphate reabsorption by proximal tubule of nephron
Net result=increase in serum Ca and increased urinary excretion of phosphate
Vitamin D
Fat soluble steroid ingested in food or synthesized in skin in presence of UV light
1st stage of activation—serum calcium level decreases and stimulates secretion of PTH
· Combination of low Ca and increased PTH causes renal activation of vitamin D
,Activated vitamin D circulates as hormone in plasma and acts to increase absorption of
calcium and phosphate in small intestine, enhance bone calcification, and increase
renal tubular reabsorption of Ca and phosphate
Calcitonin
Produced by C cells in thyroid decrease calcium levels by inhibiting osteoclastic activity
in bone
Released as calcium levels increase, suppression of PTH secretion, decreased renal
vitamin D activation, decreased intestinal calcium absorption, and increased renal
phosphate reabsorption
· Substances work together to determine amount of dietary calcium and phosphate
absorbed from intestine, deposition and absorption of calcium and phosphate from
bone, and renal absorption and excretion of calcium and phosphate by kidney
2. Discuss how calcium and phosphorus homeostasis is altered by renal disease and
the pathologic consequences.
(Page 1368) Bone and skeletal changes develop with alterations in calcium and
phosphate metabolism. These changes begin when the GFR decreases to 25% or less.
Hypocalcemia is accelerated by impaired renal synthesis of 1,25- dihydroxy- vitamin D3
(calcitriol) with decreased intestinal absorption of calcium. Renal phosphate excretion
also decreases and the increased serum phosphate binds calcium, further contributing
to hypocalcemia. Acidosis also contributes to a negative calcium balance. Decreased
serum calcium level stimulates parathyroid hormone secretion with mobilization of
calcium from bone and may cause calcium levels to approach normal. The combined
effect of hyperparathyroidism and vitamin d deficiency can result in renal
osteodystrophies. Other consequences of secondary hyperparathyroidism include soft
tissue and vascular calcification, cardiovascular disease, and less commonly, calcific
uremic arteriolopathy.
3. Examine the basic anatomy and physiology of the kidney.
Kidney Structure
Description of Role and Function:
The kidneys lay in the retroperitoneal space of the abdominal cavity, one on each side
of the spine. The kidneys have multiple functions which include:
the excretion of metabolic waste products
the maintenance of water balance
the regulation of acid base balance
blood pressure regulation
, secretion of erythropoietin which stimulates the growth of red blood cells.
Disorders which affect the kidney may result in a decrease in the production of
erythropoietin resulting in anemia. activates vitamin D. The active form assists
with the absorption of calcium in the intestines. The precursor to vitamin D is
ingested in the food that we eat (vegetables and meat). After it is absorbed it is
taken to the skin where UV light turns it into another precursor of vitamin D. This
precursor then is transported to the kidney where it is converted into the active
form of vitamin D, calcitriol. Calcitriol is then responsible for assisting with the
absorption of calcium in the intestines, promoting the release of calcium from the
bone (resorption), and decreasing renal calcium excretion. Disorders which affect
the kidney can result in a vitamin D deficiency and hypocalcemia.
renal capsule: outer most portion of the kidney and is made of a fibrous tissue.
renal fascia: fatty layer of tissue that adheres each kidney to the posterior wall of the
abdomen.
renal cortex: directly below the renal capsule and extends between the medullary
pyramids and houses the renal corpuscles and the proximal and distal tubules of the
nephron.
renal medulla: pyramid-shaped. It is the inner darker portion of the kidney tissue
consisting of renal pyramids, which contain the secreting and collecting tubules.
renal calyces: extend from the medulla and are responsible for collecting urine from
the medulla. The renal calyces extend from the medulla and merge together to form the
renal medulla.
renal medulla: gives rise to the ureter which extends to the bladder.
Nephron Structure
Nephron Function:
Glomerular Filtration
Filtration Rate
Tubular Transport
Proximal Convoluted Tubule
Loop of Henle and Distal Convoluted Tubules
Description of Role and Function:
Nephron Structure: The nephron is the functional unit of the kidney. There are two
types of nephrons:
1. cortical nephron which is located in the renal cortex
2. juxtamedullary nephron which lays close to and extends into the medulla.
, The nephron has three main functional parts:
1. Glomerulus: The glomerulus is a 2 collection of capillaries which receives blood
from the renal artery and is responsible for filtering the blood.
2. Bowman’s capsule: The bowman’s capsule partially encases the glomerulus
and extends to form the tubule system. Together the glomerulus and bowman’s
capsule are termed the renal corpuscle.
3. Tubular system: The tubule system is a collection of tubules which originate
from the bowman’s capsule.
proximal tubule: comes directly off of the bowman’s capsule and is the recipient of
the filtrate which flows from the glomerulus into the bowman’s capsule and then into the
proximal tubule. The proximal tubule reabsorbs all of the glucose (unless the threshold
for glucose is exceeded) and it reabsorbs amino acids. It also reabsorbs most of the
HCO3, Na, Cl, phosphate, potassium, and water. A serum glucose above 200mg/dL will
exceed the renal threshold for glucose and result in glucosuria and the damage
associated with diabetes mellitus. The proximal tubule when stimulated by the
parathyroid hormone will excrete phosphate. It is also the site of action for angiotensin II
which stimulates Na, water and bicarbonate reabsorption.
descending loop of Henle: extends from the proximal tubule, is impermeable to Na,
passively reabsorbs water and concentrates urine. The ascending loop of Henle
extends from the descending loop of Henle. It actively reabsorbs sodium, potassium
and chloride. It induces the reabsorption of magnesium and calcium and it is
impermeable to water; therefore, it makes the urine more dilute.
distal convoluted tubule: extends from the ascending loop of Henle, actively
reabsorbs Na, is impermeable to water and causes the urine to be more dilute. In the
distal convoluted tubule, the parathyroid hormone increases calcium reabsorption.
collecting tubule: extends from the distal convoluted tubule and connects with the
renal pyramids. It reabsorbs sodium in exchange for potassium and hydrogen. This
process is regulated by the hormone aldosterone, and this is the site of action for
antidiuretic hormone as well. Podocytes are epithelial cells in the bowman capsule
which wrap around the capillaries of the glomeruli. They form long processes (foot
projections) called pedicels which wrap around the glomerular capillaries and leave slits
between them. Blood is filtered through these slits.
juxtaglomerular apparatus (JGA): is located in the area just proximal to the renal
corpuscle, between the afferent & efferent arterioles and where the distal tubule loops
up and makes contact with the afferent arteriole. The JGA is a collection of cells
consisting of the juxtaglomerular cells, the macula densa, and the mesangial cells. The
juxtaglomerular cells are located in the wall of the afferent arterioles. They monitor renal
pressure and help to maintain normal GFR through the release of renin. When renal
perfusion is decreased these cells are responsible for releasing renin to help increase
