Session 10 A Embryology Flashcards
Describe the 3 sets of excretory organs
Pronephros
Mesonephros and duct
Metanephros
Features of the development of the kidney system
Organisation of intermediate mesoderm
3 systems develop sequentially
Disappearance of one system marks the onset of development of the next developmental stage
1st kidney system forms in the
Cervical region
The Pronephros
What are these
Intermediate mesoderm goes on to form
Pronephros
Mesonephros
Metanephros
What day does the intermediate mesoderm start to form the primitive kidney system
Day 28, pulls down
Importance of Pronephros
First kidney system, never functions in humans
Pronephric duct extends from the cervical region to the cloaca, drives the development of the next stage (Mesonephros)
Mesonephric ducts develop caudal to the
Pronephric region
Embryonic kidney is made up of
Mesonephric tubules and duct
What is lacking in the Mesonephros
No water conserving function
Why do we need to know about the Mesonephros
Important in development of male reproductive system
Spouts the ureteric bud which induces development of the definitive kidney
What forms Metanephros
Undifferentiated intermediate mesoderm, caudal to the Mesonephros
Ureteric bud induces development of the true kidney, Metanephros in this tissue
What does this show
What drives the development of the definitive kidney
Ureteric bud
The collecting system is derived from the
Ureteric bud itself
The excretory component is derived from the
Intermediate mesoderm under the influence of the ureteric bud
Describe the ascent of the kidney
Metanephric kidney first appears in the pelvic region
Undergoes an apparent caudal to cranial shift, crossing the arterial fork formed by vessels returning blood from the fetus to the placenta
What does this show
Abnormalities in ureter development
Ureteric bud fails to interact with the intermediate mesoderm (renal agenesis)
Migration goes awry
Duplication defects
Ectopic ureter
Cystic disease
Structural abnormalities related to migration
Duplication defects and ectopic urethral orifices
Splitting of ureteric bud
Partial or complete
Symptomatic consequence is ectopic ureteral opening
to begin with, the reproductive tract, urinary tract and GI tract share a common
Caudal opening
hindgut ends in
A dilated structure- the cloaca
Closed to the outside by the cloacal membrane- no mesoderm
Urogenital sinus is created from
Hindgut by urorectal septum
Urogenital sinus is continuous with
Umbilicus
Urachus closes to become the
Medial umbilical ligament
What is this
Features of urogenital sinus
Superior part connects to umbilicus
Majority differentiates to form the urinary bladder
Inferior part develops into the urethra (sex differences in structural development)
Lower part of the urogenital sinus (urethra) forms what in men and women
Women: all urethra, clitoris
Men: membranous and prostatic urethra, spongy tissue of penis
Female development vs men
Female: MD reach UGS, UB sprouts from MD, UGS begins to expand, MD regresses
Men: MD reach UGS, UB sprouts from MD, UGS begins to expand, smooth musculature begins to appear, UB and MDs make independent openings in UGS
The nephrogenic cord gives rise to three sets of foundational renal structures
Pronephros- degrade at end of week 4
Mesonephros- form the trigone
Metanephros- permanent kidney
Metanephric blastema releases
growth factors, these cause uteric bud to form from Mesonephric duct
Mesonephric duct releases growth factors which cause the
Metanephric blastema to grow
Forms ureteric stalk- renal pelvis, minor and major calyx, millions of collecting tubes
Metanephric blastema- nephron
From 5-6 weeks the
Mesonephric duct absorbed into bladder to form trigone
By week 10
The kidney is functional and the urinary system is developed enough to secrete urine
