Embryology Flashcards
From where does the urinary tract originate?
The cloaca
What adult structures are formed from the ureteric bud (mesonephric duct)?
Collecting tubules and ducts
Minor and major calyces
Ureters
Renal pelvis
What adult structures are formed from the metanephric blastema/mesoderm/metanephros?
The nephrons
Over what period does organogenesis take place?
Normally weeks 3-8
What makes up the urineferous tubule?
The nephron plus the collecting duct
What makes up the nephron?
Renal corpuscle
PCT
Loop of Henle
DCT
During what week of development does gastrulation take place?
3rd week
What happens in gastrulation?
The bilaminar disk becomes trilaminar and three three primary germ layers form, from which all body tissues develop - ectoderm, endoderm, mesoderm
What forms the kidney and ureter?
The intermediate mesoderm
What forms the bladder and urethra?
The cloaca
What does the paramesonephric duct form?
Uterus and uterine tubules
What does the mesonephric duct form?
Ductus deferens
What are the three sets of kidneys which develop before the genital system?
1st set: Pronephros
2nd set: Mesonephros
3rd: Metanephros
What is the pronephros?
The first set of ‘kidneys’ which appear as the nephrogenic cord is subdivided. They are rudimentary and non-functioning and appear early in week 4
What are the mesonephros?
Well developed set of early kidneys which function briefly during the early foetal period, appear late in week 4. They function as interim kidneys for four weeks
What are the metanephros?
The primordia of permanent kidneys that develop in the 5th week
What are the two sources of the metanephros from which the permanent kidneys develop?
Ureteric bud - drains the metanephros and will become the adult ureter
Metanephrogenic blastema
Describe the development onwards of the ureteric bud
The stalk of the bud becomes the ureter and the cranial part becomes the collecting tubules. The first 4 generations of tubules become the major calyces and the second 4 generations of tubules become the minor calyces
Describe the ascent of the kidneys
The ascent is mainly due to the differential growth of the lower body inferiorly away from the kidneys so they appear to ascend
The hilum rotates 90 degrees from ventral to medial
The ascent stops when contact with adrenal glands is made
What divides the cloaca and what is it divided into?
The urorectal septum
Into the urogenital sinus and the rectal canal
What do the three parts of the urogenital sinus go on to form?
Cranial part - bladder
Pelvic part - prostatic and membranous urethra in males, entire urethra in females
Caudal part - penile urethra in males
What forms the trigone of the bladder?
The incorporation of the inferior parts of the mesophrenic ducts
What adult structures are formed from the cloaca (urogenital sinus)?
Urethra
Bladder
What are some abnormalities related to induction or differentiation of kidney tissue?
Duplication of the urinary tract - premature division of the ureteric bud resulting in either a double kidney or duplicated ureter and renal pelvis
Nephroblastoma (Wilm’s tumour) - malignant
Polycystic kidney disease
What are some abnormalities relating to the ascent of the kidneys?
Pelvic kidney - one or both kidney(s) stay in the pelvis rather than ascending
Horseshoe kidney - the two developing kidneys fuse ventrally into a single kidney that gets trapped in the abdomen by the inferior mesenteric A
Supernumerary arteries - often more than one renal artery per kidney, can compress ureter and cause back up of fluid into kidney - hydronephrosis
What are some abnormalities relating to the formation of the bladder?
Trigonitis -sensitive to sex hormones and can undergo metaplasia leading to obstruction
Abnormal attachment of the ureters - the ureters can sometimes be attached to either the urethra or parts of the reproductive tracts
Urachal fistulas, sinuses and cysts - occur when some of the allantois persists
