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Learning objectives BMS130 – Bec Biasotto
Urinary 1: Functions of the urinary system and anatomy of the kidney
State and describe 5 functions of the kidneys other than urine formation.
• Production and excretion of urine
• Blood plasma filtration: all the blood in our body passes through the kidneys, and the
kidneys remove waste products
• Regulation of blood volume: by conserving or eliminating urine, as water makes up
majority of urine
• Regulation of body fluid osmolarity: the kidneys regulate levels of Na+, K+, Ca2+, Cl-, and
phosphate ions by conserving or eliminating urine.
• Regulation of blood pressure: the kidneys secrete renin, which is an enzyme that
increases blood pressure by activating the renin-angiotensin-aldosterone pathway
• Production of erythropoietin: kidneys produce erythropoietin (EPO) which stimulates the
production of RBCs in the bone marrow.
• Production of calcitriol: the kidneys produce calcitriol, which aids in the absorption of
calcium from the gut and helps regulate calcium homeostasis.
• Regulation of blood pH: the kidneys excrete H+ and reabsorb HCO3- (bicarbonate ions),
which helps maintain acid-base balance
• Gluconeogenesis: the kidneys use the amino acid glutamine to synthesize new glucose,
release them into the blood and maintain blood glucose levels
[Extra info] There are six organs in the urinary system: x2 kidneys, x2 ureters, the urinary
bladder, and the urethra.
Name the major nitrogenous wastes and state their sources.
• Urea: the most abundant waste. Proteins are broken down (the process is called protein
catabolism), in particular amino acids, by removing the NH2 group. Removing the NH2
group forms ammonia, which the liver converts into urea.
• Uric acid: is made from nucleic acids, DNA and RNA, being broken down (nucleic acid
catabolism).
• Creatinine: is made from creatine phosphate (creatine phosphate catabolism).
Describe the location and gross anatomy of the kidneys.
, 2
Location, size, shape
• The kidneys are retroperitoneal, which means they are posterior to (behind) the
peritoneum of the abdominal wall
• They are on either side of the spine, at the thoracic and lumbar regions (T12 and L3)
• The right kidney is slightly lower, due to the lobe of the liver pressing onto it
• The top half of the kidneys are covered by the 12th rib
• Size: about the size of a bar of soap
• Shape: they are bean shaped
Gross anatomy
• On the medial surface is a slit to the inside called the hilum; the hilum receives renal
nerves, blood vessels, lymphatics and the ureter
• There are three protective connective tissue layers on the kidneys:
o Renal fascia: outermost layer that binds the kidney to the abdominal wall
o Perirenal fat capsule: middle layer of fat that cushions the kidney and holds it in
place. This is needed because the rib cage only protects a portion of the kidneys
o Fibrous capsule: encloses the kidney to protect it from trauma and infection.
o There are collagen fibres that extend from the fibrous capsule to the renal fascia,
holding the kidneys, meaning there is a three centimetre drop after standing up
from lying down
• The kidneys have two functional areas:
o Renal parenchyma: includes the two zones of the kidneys, the outer renal cortex
and the inner renal medulla
o Renal pelvis: is what the kidney and its structures drain into; it acts as a funnel for
urine entering the ureter
• Outer renal cortex:
, 3
o Contains corpuscles, tubules, blood vessels and collecting ducts
o Produces erythropoietin
• Inner renal medulla:
o Made up of columns and pyramids
o Renal columns: are extensions of the cortex
o Renal pyramids: contain nephrons and collecting ducts
o One pyramid + the outer cortex on top = one ‘lobe’ of the kidney
• Flow of the kidney’s structures:
o Each renal column separates the renal pyramids
o Each pyramid drains into a renal papilla
o Each papilla is within a minor calyx
o Minor calyces are branches of the major calyx
o Major calyces are branches of the renal pelvis
o The renal pelvis is continuous with the ureter
Trace the flow of blood through the kidneys & identify the vessels.
• The purple vessels are in and around individual nephrons
• The efferent arteriole flows to two different nephrons and therefore has two different
pathways
o Cortical nephrons: the efferent arteriole flows to peritubular capillaries
o Juxtamedullary nephrons: the efferent arteriole flows to vasa recta
Describe the nephron and its 2 parts (renal corpuscle and renal tubule).
, 4
The nephron is the function unit of the kidney, and is responsible for filtering blood and
forming urine. There are two sections of the nephron: the renal corpuscle, and the renal
tubule. There is approximately 1.2 million nephrons per kidney.
The renal corpuscle is responsible for plasma filtration. It consists of the glomerulus and
Bowman’s capsule.
• Glomerulus: is a specialised network of tubules in the nephron, which filters waste out of
plasma, producing filtrate.
• Bowman’s capsule: is a two-layered capsule around the glomerulus. There is an outer
parietal layer and an inner visceral layer, with capsular space between. The inner visceral
layer is made up of podocytes, which have ‘foot processes’ that interlock, creating
narrow slits that keep in larger molecules and allow fluid to pass.
The renal tubule is responsible for converting filtrate into urine. It consists of the proximal
convoluted tubule (PCT), the nephron loop, and the distal convoluted tubule (DCT).
• Proximal convoluted tubule (PCT): simple cuboidal epithelium with microvilli
• Nephron loop:
o Thick segment: simple cuboidal epithelium for active transport
o Thin segment: simple squamous epithelium that is highly permeable to water
• Distal convoluted tubule (DCT): simple cuboidal epithelium without microvilli
Learning objectives BMS130 – Bec Biasotto
Urinary 1: Functions of the urinary system and anatomy of the kidney
State and describe 5 functions of the kidneys other than urine formation.
• Production and excretion of urine
• Blood plasma filtration: all the blood in our body passes through the kidneys, and the
kidneys remove waste products
• Regulation of blood volume: by conserving or eliminating urine, as water makes up
majority of urine
• Regulation of body fluid osmolarity: the kidneys regulate levels of Na+, K+, Ca2+, Cl-, and
phosphate ions by conserving or eliminating urine.
• Regulation of blood pressure: the kidneys secrete renin, which is an enzyme that
increases blood pressure by activating the renin-angiotensin-aldosterone pathway
• Production of erythropoietin: kidneys produce erythropoietin (EPO) which stimulates the
production of RBCs in the bone marrow.
• Production of calcitriol: the kidneys produce calcitriol, which aids in the absorption of
calcium from the gut and helps regulate calcium homeostasis.
• Regulation of blood pH: the kidneys excrete H+ and reabsorb HCO3- (bicarbonate ions),
which helps maintain acid-base balance
• Gluconeogenesis: the kidneys use the amino acid glutamine to synthesize new glucose,
release them into the blood and maintain blood glucose levels
[Extra info] There are six organs in the urinary system: x2 kidneys, x2 ureters, the urinary
bladder, and the urethra.
Name the major nitrogenous wastes and state their sources.
• Urea: the most abundant waste. Proteins are broken down (the process is called protein
catabolism), in particular amino acids, by removing the NH2 group. Removing the NH2
group forms ammonia, which the liver converts into urea.
• Uric acid: is made from nucleic acids, DNA and RNA, being broken down (nucleic acid
catabolism).
• Creatinine: is made from creatine phosphate (creatine phosphate catabolism).
Describe the location and gross anatomy of the kidneys.
, 2
Location, size, shape
• The kidneys are retroperitoneal, which means they are posterior to (behind) the
peritoneum of the abdominal wall
• They are on either side of the spine, at the thoracic and lumbar regions (T12 and L3)
• The right kidney is slightly lower, due to the lobe of the liver pressing onto it
• The top half of the kidneys are covered by the 12th rib
• Size: about the size of a bar of soap
• Shape: they are bean shaped
Gross anatomy
• On the medial surface is a slit to the inside called the hilum; the hilum receives renal
nerves, blood vessels, lymphatics and the ureter
• There are three protective connective tissue layers on the kidneys:
o Renal fascia: outermost layer that binds the kidney to the abdominal wall
o Perirenal fat capsule: middle layer of fat that cushions the kidney and holds it in
place. This is needed because the rib cage only protects a portion of the kidneys
o Fibrous capsule: encloses the kidney to protect it from trauma and infection.
o There are collagen fibres that extend from the fibrous capsule to the renal fascia,
holding the kidneys, meaning there is a three centimetre drop after standing up
from lying down
• The kidneys have two functional areas:
o Renal parenchyma: includes the two zones of the kidneys, the outer renal cortex
and the inner renal medulla
o Renal pelvis: is what the kidney and its structures drain into; it acts as a funnel for
urine entering the ureter
• Outer renal cortex:
, 3
o Contains corpuscles, tubules, blood vessels and collecting ducts
o Produces erythropoietin
• Inner renal medulla:
o Made up of columns and pyramids
o Renal columns: are extensions of the cortex
o Renal pyramids: contain nephrons and collecting ducts
o One pyramid + the outer cortex on top = one ‘lobe’ of the kidney
• Flow of the kidney’s structures:
o Each renal column separates the renal pyramids
o Each pyramid drains into a renal papilla
o Each papilla is within a minor calyx
o Minor calyces are branches of the major calyx
o Major calyces are branches of the renal pelvis
o The renal pelvis is continuous with the ureter
Trace the flow of blood through the kidneys & identify the vessels.
• The purple vessels are in and around individual nephrons
• The efferent arteriole flows to two different nephrons and therefore has two different
pathways
o Cortical nephrons: the efferent arteriole flows to peritubular capillaries
o Juxtamedullary nephrons: the efferent arteriole flows to vasa recta
Describe the nephron and its 2 parts (renal corpuscle and renal tubule).
, 4
The nephron is the function unit of the kidney, and is responsible for filtering blood and
forming urine. There are two sections of the nephron: the renal corpuscle, and the renal
tubule. There is approximately 1.2 million nephrons per kidney.
The renal corpuscle is responsible for plasma filtration. It consists of the glomerulus and
Bowman’s capsule.
• Glomerulus: is a specialised network of tubules in the nephron, which filters waste out of
plasma, producing filtrate.
• Bowman’s capsule: is a two-layered capsule around the glomerulus. There is an outer
parietal layer and an inner visceral layer, with capsular space between. The inner visceral
layer is made up of podocytes, which have ‘foot processes’ that interlock, creating
narrow slits that keep in larger molecules and allow fluid to pass.
The renal tubule is responsible for converting filtrate into urine. It consists of the proximal
convoluted tubule (PCT), the nephron loop, and the distal convoluted tubule (DCT).
• Proximal convoluted tubule (PCT): simple cuboidal epithelium with microvilli
• Nephron loop:
o Thick segment: simple cuboidal epithelium for active transport
o Thin segment: simple squamous epithelium that is highly permeable to water
• Distal convoluted tubule (DCT): simple cuboidal epithelium without microvilli
