22 Flashcards
What embryonic layer gives rise to the kidneys?
The intermediate mesoderm.
Are the kidneys the organ system we most understand the development of?
Yes
What are some of the functions of the kidneys?
Removal of wastes, regulation of blood fluid volume, control of blood pH, production of hormones and processing of metabolites
What are the three stages of the kidney from most to least developed?
Metanephros, mesonephros, pronephros
What is the function of the pronephros in fish and amphibians? Does this differ in amniotes?
In fish and amphibians it’s an osmoregulatory organ and it triggers the development of later kidneys.
In amniotes there is no known physiological function beyond inducing the development of later kidneys.
What is the function of the mesonephros in fish and amphibians? Does this differ in amniotes?
In fish and amphibians it is the adult kidney and it’s a linear array of thousands of nephrons.
In amniotes it has variable physiological function with 20-40 linear nephrons, and it induces development of later kidneys.
What week and approximate day do the pronephroi, mesonephroi, and metanephroi develop?
Pronephroi: early in week 4, ~day 24
Mesonephroi: late in week 4, ~day 25-28
Metanephroi: early in week 5, ~day 32
What is the functioning window of the mesonephros in the developing human? What happens to it after this window?
6-10 weeks. It degenerates.
What is reciprocal induction in the development of the mammalian kidney?
The process by which each bud generates a nephron and then induces the budding of another
What are the steps of ureteric bud growth? What hormones and receptors are involved?
On the surface of the developing mesonephric duct or wolffian duct there are Ret RTK receptors. A clump of metanephrogenic mesenchyme produces and secretes GDNF, which binds to these receptors, inducing the formation of a ureteric bud. The mesenchyme will condense around the bud and undergo an MET as the bud buds into the mesenchyme, and continues to bud within it.
When does kidney branching stop in developing humans?
Week 32.
What happens in a heterozygous and homozygous knock out for GDNF?
Het: There is less ureteric branching
Homo: there is no ureteric branching or budding
What are the functions of these Wnts in kidney development: Wnt9b, Wnt11, and Wnt4. Where are they expressed?
Wnt9b: Induces the mesenchyme to condense around it. Expressed in ureteric bud and wolffian duct.
Wnt11: Triggers bud branching. Expressed at the tip of the bud.
Wnt4: Required in an autocrine manner for MET. Expressed by condensing mesenchyme.
What is the role of Hox genes in the healthy development of the kidney?
HOX11 paralog proteins induce expression of GDNF in the metanephrogenic mesenchyme and thus is crucial for forming the metanephros and allowing ureteric budding to occur. Mice with homozygous null mutations in Hoxa/c/d11 have NO kidney development.
What is the difference between the ureter and the urethra?
The urethra connects the bladder to the exterior of the body and allows for the voiding of wastes. It is made of endoderm.
The ureter connects the kidneys to the bladder and drains nitrogenous waste filtered by the kidneys into the bladder. It is made of intermediate mesoderm.
