Questions and Answers
What is the main function of the mesonephros?
What connects the mesonephric duct to the cloaca?
What is the fate of the pronephros?
What stimulates the formation of the ureteric bud?
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What connects to the collecting tubules to form the distal convoluted tubule?
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What drains into the bladder and urethra?
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What is the final stage of nephron development?
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What is the name of the process in which the bilaminar disc transforms into a trilaminar disc?
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What is the function of the metanephric mesoderm?
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Which of the following is NOT a component of the mesoderm?
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What is the name of the structure that forms from the condensation of the intermediate mesoderm?
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What is the part of the urogenital ridge that will become the urinary system?
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What is the name of the duct that the pronephros is made up of?
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During which week does the pronephros develop from the nephrogenic cord?
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What is the name of the cavity that forms from the epiblast cells during gastrulation?
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What is the process that results in a structure that resembles the internal organs?
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Study Notes
Development of the Urinary System
- The urinary system develops from the intermediate mesoderm.
- The intermediate mesoderm is formed during gastrulation, when the bilaminar disc (amniotic cavity and epiblast) transforms into a trilaminar disc (ectoderm, mesoderm, and endoderm).
- The mesoderm has three components: paraxial mesoderm, intermediate mesoderm, and lateral plate mesoderm.
Gastrulation and Folding
- During gastrulation, the epiblast cells move through the primitive streak and replace the hypoblast cells, converting them into endoderm.
- The mesoderm is formed above the endoderm, and the epiblast cells differentiate into ectoderm.
- The trilaminar disc undergoes lateral folding and cranial-caudal folding, resulting in a structure that resembles the internal organs.
Intermediate Mesoderm and Urogenital Ridge
- The intermediate mesoderm condenses and forms a bulge near the splanchic layer of the lateral plate mesoderm, creating a structure called the urogenital ridge.
- The urogenital ridge will develop into the urinary system and reproductive system.
- The part of the urogenital ridge that will become the urinary system is called the nephrogenic cord.
Nephrogenic Cord
- The nephrogenic cord is a long, narrow structure that spans the length of the embryo behind the gut tube.
- In a sagittal section, the nephrogenic cord is visible behind the gut tube, which is divided into foregut, midgut, and hindgut.
- The nephrogenic cord will develop into the urinary system.
Development of the Urinary System from the Nephrogenic Cord
- The nephrogenic cord interacts with the cloaca, which will become the bladder and urethra.
- Around week four, the pronephros develops from the nephrogenic cord in the cervical region.
- The pronephros is made up of a duct and nephrotomes, but it starts degenerating by the end of week four.
- Around week five, the mesonephros develops from the pronephros, extending from the thoracic region to the lumbar region and connecting with the cloaca.
- The mesonephros is made up of a mesonephric duct and mesonephric tubules.
- The mesonephros becomes the primitive urinary system up until week 10.### Primitive Urinary System Development
- Formation of the duct and tubules from the pro-nephros
- Mesonephros develops from the pro-nephros in the thoracolumbar region
- Mesonephros will become the primitive urinary system
- Mesonephric duct connected to the cloaca
- Cloaca drains into the bladder and urethra
- Degeneration of the pro-nephros
- Pronephros degenerates, and the mesonephric duct and tubules remain
- Mesonephric duct and tubules form a bowman's capsule around the glomerulus
Formation of the Primitive Kidney
- Mesonephric duct and tubules grow and develop into the primitive kidney
- Mesonephric duct connected to the cloaca, which drains into the bladder and urethra
- Cloaca receives both urine and feces
- The primitive urinary system functions from week 5-10
Formation of the Metanephros
- Development of the metanephros in the pelvic region
- Intermediate mesoderm condenses to form the metanephric mesoderm
- Metanephric mesoderm releases growth factors, stimulating the mesonephric duct to form a ureteric bud
- Ureteric bud grows and forms a renal pelvis, major calyx, minor calyx, and collecting tubules
- Collecting tubules connect to the ureter, which is connected to the mesonephric duct
Nephron Development
- Formation of the nephron from the metanephric mesoderm and collecting tubules
- Metanephric mesoderm cap forms around the collecting tubules
- Growth factors released by the collecting tubules stimulate the metanephric mesoderm cap to proliferate and condense
- Metanephric vesicle forms, and then develops into an S-shaped metanephric tubule
- Metanephric tubule connects to the collecting tubule, forming the distal convoluted tubule
- Distal convoluted tubule forms a loop of Henle, and then develops into the proximal convoluted tubule
- Proximal convoluted tubule forms the bowman's capsule, and the entire structure becomes the nephron
Formation of the Mature Kidney
- Ascent of the kidneys and development of the renal arteries
- Common iliac arteries degenerate, and the kidneys ascend to the upper quadrants of the abdomen
- Lateral branches of the aorta develop and invade the kidney, forming the renal arteries
- Renal arteries supply blood to the nephrons
- Takeover of the metanephros as the functional urinary system
- By week 10, the metanephros takes over the function of the mesonephros
- The metanephros becomes the functional urinary system
Formation of the Bladder and Urethra
- Development of the bladder and urethra from the cloaca
- Urorectal septum forms and separates the cloaca into the bladder and anal canal
- Anterior portion of the cloaca forms the bladder and urethra
- Ureter and mesonephric duct connect to the bladder
- Development of the urogenital sinus
- Urogenital sinus forms from the anterior portion of the cloaca
- Proximal portion of the urogenital sinus forms the bladder
- Middle portion forms the urethra (prostatic and membranous urethra in males, and urethra in females)
- Distal portion of the urogenital sinus forms the penile urethra in males
Additional Facts
- Elantois: a structure that drains the cloaca, which becomes the uracus and then the median umbilical ligament
- The development of the urinary system is closely related to the development of the reproductive system
Development of the Urinary System
- The urinary system develops from the intermediate mesoderm, which is formed during gastrulation.
- Gastrulation involves the transformation of the bilaminar disc (amniotic cavity and epiblast) into a trilaminar disc (ectoderm, mesoderm, and endoderm).
- The mesoderm has three components: paraxial mesoderm, intermediate mesoderm, and lateral plate mesoderm.
Gastrulation and Folding
- The epiblast cells move through the primitive streak and replace the hypoblast cells, forming endoderm during gastrulation.
- The mesoderm is formed above the endoderm, and the epiblast cells differentiate into ectoderm.
- The trilaminar disc undergoes lateral folding and cranial-caudal folding, resulting in a structure that resembles the internal organs.
Intermediate Mesoderm and Urogenital Ridge
- The intermediate mesoderm condenses and forms a bulge near the splanchic layer of the lateral plate mesoderm, creating the urogenital ridge.
- The urogenital ridge will develop into the urinary system and reproductive system.
- The part of the urogenital ridge that will become the urinary system is called the nephrogenic cord.
Nephrogenic Cord
- The nephrogenic cord is a long, narrow structure that spans the length of the embryo behind the gut tube.
- In a sagittal section, the nephrogenic cord is visible behind the gut tube, which is divided into foregut, midgut, and hindgut.
- The nephrogenic cord will develop into the urinary system.
Development of the Urinary System from the Nephrogenic Cord
- The nephrogenic cord interacts with the cloaca, which will become the bladder and urethra.
- Around week four, the pronephros develops from the nephrogenic cord in the cervical region.
- The pronephros is made up of a duct and nephrotomes, but it starts degenerating by the end of week four.
Pronephros and Mesonephros
- Around week five, the mesonephros develops from the pronephros, extending from the thoracic region to the lumbar region and connecting with the cloaca.
- The mesonephros is made up of a mesonephric duct and mesonephric tubules.
- The mesonephros becomes the primitive urinary system up until week 10.
Primitive Urinary System Development
- The pronephros degenerates, and the mesonephric duct and tubules remain.
- The mesonephric duct and tubules form a Bowman's capsule around the glomerulus.
- The mesonephros will become the primitive urinary system.
Formation of the Primitive Kidney
- The mesonephric duct and tubules grow and develop into the primitive kidney.
- The mesonephric duct is connected to the cloaca, which drains into the bladder and urethra.
- The cloaca receives both urine and feces.
- The primitive urinary system functions from week 5-10.
Formation of the Metanephros
- The metanephros develops in the pelvic region from the intermediate mesoderm.
- The metanephric mesoderm releases growth factors, stimulating the mesonephric duct to form a ureteric bud.
- The ureteric bud grows and forms a renal pelvis, major calyx, minor calyx, and collecting tubules.
- The collecting tubules connect to the ureter, which is connected to the mesonephric duct.
Nephron Development
- The nephron forms from the metanephric mesoderm and collecting tubules.
- The metanephric mesoderm cap forms around the collecting tubules.
- Growth factors released by the collecting tubules stimulate the metanephric mesoderm cap to proliferate and condense.
- The metanephric vesicle forms, and then develops into an S-shaped metanephric tubule.
- The metanephric tubule connects to the collecting tubule, forming the distal convoluted tubule.
- The distal convoluted tubule forms a loop of Henle, and then develops into the proximal convoluted tubule.
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Description
Learn about the development of the urinary system from the intermediate mesoderm and the process of gastrulation and folding in embryonic development.
