Difference between revisions of "Intermediate Mesoderm Development - Anatomy & Physiology"
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==Introduction== | ==Introduction== | ||
The intermediate mesoderm exists as a strip of tissue between the lateral plate mesoderm and somites. It gives rise to the urinary system and some parts of the reproductive system. Kidney development includes three forms: | The intermediate mesoderm exists as a strip of tissue between the lateral plate mesoderm and somites. It gives rise to the urinary system and some parts of the reproductive system. Kidney development includes three forms: | ||
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==Pronephros== | ==Pronephros== | ||
− | *''The earliest kidney. Develops in the anterior of the animal (adjacent to somites | + | *''The earliest kidney. Develops in the anterior of the animal (adjacent to somites 1 - 10). Eliminated in later development''. |
#At intervals along the intermediate mesoderm, dorsal evaginations occur. | #At intervals along the intermediate mesoderm, dorsal evaginations occur. | ||
#Evaginations extend caudally and eventually fuse with more caudal evaginations. | #Evaginations extend caudally and eventually fuse with more caudal evaginations. | ||
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==Mesonephros== | ==Mesonephros== | ||
− | *''Development occurs in an anterior to posterior direction; the mesonephros | + | *''Development occurs in an anterior to posterior direction; the mesonephros kidney is found at the thoracic to lumbar level''. |
#The medial portion of the intermediate mesoderm forms a cup in the region of the capillaries. | #The medial portion of the intermediate mesoderm forms a cup in the region of the capillaries. | ||
#*This is an early Bowman's capsule and improves waste removal. | #*This is an early Bowman's capsule and improves waste removal. | ||
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#*Excretory duct now known as the '''Wolffian Duct'''. | #*Excretory duct now known as the '''Wolffian Duct'''. | ||
*Amphibians and fish use the mesonephric kidney. | *Amphibians and fish use the mesonephric kidney. | ||
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==Metanephros== | ==Metanephros== | ||
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#*It subsequently develops into a nephron. | #*It subsequently develops into a nephron. | ||
#The remaining branch splits into two, and repeats the process. | #The remaining branch splits into two, and repeats the process. | ||
+ | #The primary branch forms the ureter; the remainder leads to the compact kidney of mammals. | ||
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+ | {{OpenPages}} | ||
+ | [[Category:Developmental Biology]] | ||
+ | [[Category:Urinary System - Anatomy & Physiology]] |
Latest revision as of 19:08, 28 June 2012
Introduction
The intermediate mesoderm exists as a strip of tissue between the lateral plate mesoderm and somites. It gives rise to the urinary system and some parts of the reproductive system. Kidney development includes three forms:
- Pronephros
- Mesonephros
- Metanephros
Mammals develop all three, and continue to use the metanephros in adult life. More primitive animals have only the first one or two.
Pronephros
- The earliest kidney. Develops in the anterior of the animal (adjacent to somites 1 - 10). Eliminated in later development.
- At intervals along the intermediate mesoderm, dorsal evaginations occur.
- Evaginations extend caudally and eventually fuse with more caudal evaginations.
- The caudal - most evagination fuses with the cloaca.
- Forms a continuous excretory tube to the cloaca.
- Capillaries develop at the medial aspect of the intermediate mesoderm so that waste can diffuse from the blood to the excretory channel.
- Connections between the intermediate mesoderm and somites as well between the intermediate mesoderm and lateral plate mesoderm break down.
Mesonephros
- Development occurs in an anterior to posterior direction; the mesonephros kidney is found at the thoracic to lumbar level.
- The medial portion of the intermediate mesoderm forms a cup in the region of the capillaries.
- This is an early Bowman's capsule and improves waste removal.
- The excretory channel pinches off from all surrounding tissue (lateral plate mesoderm) to become entirely closed.
- Excretory duct now known as the Wolffian Duct.
- Amphibians and fish use the mesonephric kidney.
Metanephros
- Formation of the metanephros employs recipricol signalling.
- At the level of the sacrum, a block of intermediate mesoderm breaks off from the Wolffian duct. It is called a metanephric blastema.
- The metanephric blastema signals to the Wolffian duct.
- Wolffian duct is induced to grow, and a bud of Wolffian duct moves towards the metanephric blastema.
- The bud is called the ureteric duct.
- The ureteric duct contacts the blastema, and divides into two branches.
- One of the branches induces adjacent mesenchyme to undergo a mesenchymal to epithelial transition.
- It subsequently develops into a nephron.
- The remaining branch splits into two, and repeats the process.
- The primary branch forms the ureter; the remainder leads to the compact kidney of mammals.
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