Urinary Embryology (S2 stuff done) Flashcards
Fter gastrulation, what are the two areas of the trilaminar disk where endo- and ectoderm are in direct contact?
Buccopharyngeal membrane (rostrally)
Cloacal membrane (caudally)
What are the 3 primitive kidney systems and from what tissue do they develop?
Pronephros
Mesonephros
Metanephros
All develop from Intermediate mesoderm
Identify the red and yellow structures and label the lines
Yellow
Gut tube
Red
Intermediate mesoderm
Boxes from top clockwise:
Pronephros
Mesonephros
Pronephric Duct
Metanephros
Cloaca
What is the function of the pronephros?
Never functions as a filtration system
The pronephric duct is the only useful structure as it drives the development of the next developemental stage
Describe the development of the pronephros
Begins developing in the cervical region of the intermediate mesoderm
Drops the long pronephric duct down caudally, running parallel to the gut tube
Finally connecting to the caudal gut tube at the cloaca
What structure develops after the pronephros?
The urogenital ridge is created as intermediate mesoderm continues to develop cranially to caudally
What structures are found within the urogenital ridge?
The mesonephros
The mesonephric duct (What used to be the pronephric duct)
Gonad
What are the structures and functions of the embryonic kidney?
Structures:
Mesonephric tubules
Mesonephric duct
Function:
Mesonephric tubules developing in the mesonephros can perform primitive renal function (can’t conserve water)
Mesonephric duct sprouts the uretic bud which induces definitive kidney development
Mesonephric duct has important role in male reproductive system development
Label the boxes
Top then Bottom:
Mesonephros
Mesonephric duct
Describe the development of the metanephros and ureteric bud
Ureteric bud appears on the mesonephrotic duct
This stimulates a zone of special intermediate mesoderm to develop/differentiate into the metanephric blastema
The ureteric bud contacts the blastema and starts to expand and branch, later developing into the ureter, renal pelvis, calycies and collecting ducts (collecting system) while the blastema (excretory component) develops around it
Label this diagram of metanephric development
Boxes From top left clockwise:
Uretic bud contacts metanephros
Bud expands and branches
Minor calyx
Major calyx
Renal pelvis
During it’s development, the metanephros moves.
Describe where it moves
What is the mechanism of movement?
Where:
Metanephros undergoes an ‘apparent’ caudal to cranial shift into its final position in the lumbar region
Crosses the arterial fork formed by vessels returning blood from fetus to placenta
Mechanism:
Largely due to elongation of the trunk
Some genuine movement of the metanephros
Describe how the kidneys are vascularised during ascent
How is this relevant clinically?
Blood is supplied by a series of arteries from the aorta
One artery is present at a time
As kidney moves cranially, another artery develops to supply it
Previous artery degenerates
Clinical:
This sequence explains the common appearance of multiple renal arteries, if one artery fails to degenerate then multiple will be seen in the adult
What might happen if a ureteric bud fails to interact with the intermediate mesoderm?
Renal agenesis
Usually uni-lateral
Compatible with life if unilateral
What is a Wilm’s Tumour?
Cancer of the kidney’s that normally affects <5s but may occur fetally
Describe how ectopic ureteral orifices might come about and where they may open
Splitting of the ureteric bud can lead to development of multiple ureters developing
The symptomatic consequence is multiple ureteric orifices
These may drain into the vagina or the urethra (potentially cuasing incontinence)
What leads to the development of multicystic kidney disease and how does it present?
Atresia of the ureter
Large fluid filled (urine) cysts present in the kidney due to lack of urine outflow
What is polycystic kidney disease?
Genetic disease
Presents early
Poor prognosis
Results in the appearance of large fluid filled cysts in the kidneys
Early in development, where do the GI, urinary and reproductive tracts end?
The Cloaca
As development progresses how are the GI and urinary tracts split?
The development of the urorectal septum divides the hindgut (endoderm) into the urinary tract (urogenital sinus) and the GI tract
Early in development what is the only structure associated with the urogneital sinus?
What is the adult form?
The urachus
Median umbilical ligament
Describe the Urogenital sinus’s structure and what each part will later develop into
Divided into 3 parts
Largest upper part:
Future bladder
Pelvic and phallic:
Parts of the future urethra
Label the image on the left with what these sections will develop into
Label the image on the right with the embryonic names of thes sections
Right, Top to bottom:
Bladder
Urethra
Left, Top to bottom:
Future bladder
Phallic part
Pelvic part
These diagrams show the development of what sex?
Label these diagrams with the process occuring at this point in development?
Male
Boxes from top left:
Mesonephric ducts reach urogenital sinus
Ureteric bud sprouts from MDs
Smooth musculature appears and UGS expands
UBs and MDs make independent openings in the UGS
MDs become reproductive ducts maintained by androgens
Prostate and prostatic urethra formed
Development of what sex is shown?
Label the boxes with the process occuring at each respective stage
Female
Boxes from top left:
Mesonephric ducts reach urogenital sinus
Ureteric buds sprout from MDs
UGS expands, MDs begin to regress
MD regression continues, Ureteric buds open into UGS
MD regression completes
What structures do the urethras of each sex develop from?
Hint: Include origin of each urethral section
Female:
Urethra develops from the pelvic part of the urogenital sinus
Male:
Pre-prostatic, prostatic and membranous urethra develop from pelvic section of UGS
Spongy urethra develops from the phallic section of the UGS
What are the basic embryonic components of the external genitalia?
Describe in few words the difference in development of the male and femal external genitalia
Components:
Genital tubercle
Genital folds
Genital swellings
Label this diagram
Top row far left:
Indifferent stage
Diagrams all from anus clockwise:
7 weeks:
Genital swelling
Genital fold
Genital tubercle
Urogenital sinus
9 weeks:
Genital swelling
Genital fold
Phallus
Urogenital sinus
Male, 12 weeks:
Scrotum
Wall of urethral groove
Glans penis
Urethral groove
Scrotal raphe
Female, 12 weeks:
Labia minora
Labia majora
Clitoris
Urethra orifice
Vaginal orifice
What are some the congenital abnormalites related to development of structures arising from the urogenital sinus?
Fistulae
Exstrophy of the bladder
Ectopic ureteral orifices
Hypospadias
Describe hypospadias
Arises from defect in the fusion of urethral folds
Urethra opens onto the ventral surface of the penis rather than at the glans
