Questions and Answers
Which process converts a bilaminar disc into a trilaminar disc?
What component of the mesoderm gives rise to the urinary system?
What is the name of the structure that forms through the condensation of the intermediate mesoderm?
What is the function of the pronephros?
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Where does the mesonephros develop?
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What structure plays an important role in the development of the urinary system?
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What is the mesonephros composed of?
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During which week does the pronephros develop in the cervical region of the nephrogenic cord?
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What develops from the pronephros with abduct tubules in the thoracolumbar region?
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What process is responsible for the formation of the renal pelvis, major and minor calyces, and collecting tubules?
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What connects to the mesonephric duct?
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What becomes the primitive urinary system up until week 10?
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What stimulates the metanephric blastoma?
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What develops from the metanephric blastoma?
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What separates the cloaca into the bladder and anal canal?
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What eventually degenerates and is replaced by the metanephros?
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Study Notes
Development of the Urinary System
- The foundation for developing the urinary system is the intermediate mesoderm, which is formed during gastrulation.
- Gastrulation is the process that converts a bilaminar disc into a trilaminar disc, consisting of the ectoderm, mesoderm, and endoderm.
Components of Mesoderm
- The mesoderm has three components:
- Paraxial mesoderm
- Intermediate mesoderm (the component that forms the urinary system)
- Lateral plate mesoderm (divided into the somatic layer and splanchnic layer)
Formation of the Urogenital Ridge
- The intermediate mesoderm condenses and forms the urogenital ridge, which will give rise to the urinary and reproductive systems.
- The urogenital ridge is formed through the condensation of the intermediate mesoderm near the splanchnic layer of the lateral plate mesoderm.
- The part of the urogenital ridge that forms the urinary system is called the nephrogenic cord.
Nephrogenic Cord
- The nephrogenic cord is a long, cord-like structure that spans the length of the embryo, located behind the gut tube.
- The nephrogenic cord will eventually form the urinary system.
- The gut tube, specifically the cloaca, plays an important role in the development of the urinary system.
Development of the Urinary System from the Nephrogenic Cord
- Around week 4, the pronephros develops in the cervical region of the nephrogenic cord.
- The pronephros consists of a duct and nephrotomes (little tubules) in front of it.
- However, the pronephros starts to degenerate by the end of week 4, and its purpose is not well understood.
Development of the Mesonephros
- By the end of week 4, the mesonephros starts to form, 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
- Mesonephros develops from the pronephros with abduct tubules in the thoracolumbar region
- Mesonephros becomes the primitive urinary system
- Mesonephric duct is connected to the cloaca
- Cloaca becomes the bladder and urethra
- Mesonephros will eventually degenerate and be replaced by the metanephros
Formation of the Collecting System
- Mesonephric duct grows and forms the ureteric bud
- Ureteric bud releases growth factors, stimulating the metanephric blastoma
- Metanephric blastoma releases growth factors, stimulating the ureteric bud
- This process is called reciprocal induction
- Ureteric bud grows and forms the renal pelvis, major and minor calyces, and collecting tubules
- Collecting tubules connect to the ureteric bud, which becomes the ureter
- The ureteric bud connects to the mesonephric duct
Formation of the Nephron
- Collecting tubule cells release growth factors, influencing the metanephric mesodermal cap
- Metanephric mesodermal cap proliferates and condenses into a singular structure
- This structure becomes the metanephric vesicle
- Metanephric vesicle becomes the metanephric tubule
- Metanephric tubule connects to the collecting tubule, forming the nephron
- Nephron consists of the glomerulus, Bowman's capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting tubule
Development of the Kidney
- Metanephros develops in the pelvic region
- Kidney develops from the metanephric blastoma
- Kidney takes over the job of the mesonephros by week 10
- Blood vessels from the common iliac arteries develop into the renal arteries
- Renal arteries supply the kidney with blood
Development of the Bladder and Urethra
- Cloaca separates into the bladder and anal canal
- Ureteral septum separates the cloaca into the bladder and anal canal
- Anterior portion of the cloaca becomes the bladder and urethra
- Middle portion of the urogenital sinus becomes the urethra in males and females
- Distal portion of the urogenital sinus becomes the penile urethra in males
- The ureter empties into the bladder
Other Important Points
- The structure that drained the cloaca is called the alantois
- Alantois becomes the urachus and eventually becomes the median umbilical ligament
Development of the Urinary System
- The intermediate mesoderm forms the foundation of the urinary system during gastrulation.
Components of Mesoderm
- Mesoderm has three components:
- Paraxial mesoderm
- Intermediate mesoderm (forms the urinary system)
- Lateral plate mesoderm (divided into somatic and splanchnic layers)
Formation of the Urogenital Ridge
- Intermediate mesoderm condenses to form the urogenital ridge, which gives rise to the urinary and reproductive systems.
- Urogenital ridge forms near the splanchnic layer of the lateral plate mesoderm.
- The part of the urogenital ridge that forms the urinary system is called the nephrogenic cord.
Nephrogenic Cord
- Nephrogenic cord is a cord-like structure that spans the length of the embryo, located behind the gut tube.
- Nephrogenic cord will eventually form the urinary system.
- The gut tube, specifically the cloaca, plays a crucial role in the development of the urinary system.
Development of the Urinary System from the Nephrogenic Cord
- Pronephros develops in the cervical region of the nephrogenic cord around week 4.
- Pronephros consists of a duct and nephrotomes (little tubules) in front of it.
- Pronephros degenerates by the end of week 4, and its purpose is not well understood.
Development of the Mesonephros
- Mesonephros forms by the end of week 4, extending from the thoracic region to the lumbar region and connecting with the cloaca.
- Mesonephros is made up of a mesonephric duct and mesonephric tubules.
- Mesonephros becomes the primitive urinary system up until week 10.
Primitive Urinary System
- Mesonephros develops from the pronephros with abduct tubules in the thoracolumbar region.
- Mesonephros becomes the primitive urinary system.
- Mesonephric duct is connected to the cloaca.
- Cloaca eventually becomes the bladder and urethra.
- Mesonephros will eventually degenerate and be replaced by the metanephros.
Formation of the Collecting System
- Mesonephric duct grows and forms the ureteric bud.
- Ureteric bud releases growth factors, stimulating the metanephric blastoma.
- Metanephric blastoma releases growth factors, stimulating the ureteric bud (reciprocal induction).
- Ureteric bud grows and forms the renal pelvis, major and minor calyces, and collecting tubules.
- Collecting tubules connect to the ureteric bud, which becomes the ureter.
- Ureteric bud connects to the mesonephric duct.
Formation of the Nephron
- Collecting tubule cells release growth factors, influencing the metanephric mesodermal cap.
- Metanephric mesodermal cap proliferates and condenses into a singular structure.
- This structure becomes the metanephric vesicle.
- Metanephric vesicle becomes the metanephric tubule.
- Metanephric tubule connects to the collecting tubule, forming the nephron.
- Nephron consists of the glomerulus, Bowman's capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting tubule.
Development of the Kidney
- Metanephros develops in the pelvic region.
- Kidney develops from the metanephric blastoma.
- Kidney takes over the job of the mesonephros by week 10.
- Blood vessels from the common iliac arteries develop into the renal arteries.
- Renal arteries supply the kidney with blood.
Development of the Bladder and Urethra
- Cloaca separates into the bladder and anal canal.
- Ureteral septum separates the cloaca into the bladder and anal canal.
- Anterior portion of the cloaca becomes the bladder and urethra.
- Middle portion of the urogenital sinus becomes the urethra in males and females.
- Distal portion of the urogenital sinus becomes the penile urethra.
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Description
Learn about the formation of the urinary system from the intermediate mesoderm during gastrulation. Understand the components of mesoderm and their roles in the development process.
