Embryology - 3 Flashcards
Where does the kidneys, ureter and gonads arise from?
Intermediate mesoderm
What is the urogenital ridge?
Nephrogenic cord and the gonadal ridge
Part of urinary system and reproductive system develop from this
What does the urogenital ridge differentiate into?
Gonadal ridge medially which gives rise to gonad and nephrogenic cord laterally to form kidneys and ureter
When does the urinary system develop?
Ahead of repro system
From 4th week of embryo development
What 2 overlapping systems in nephrogenic cord does the kidney and ureter develop from?
Pronephros, mesonephros and metanephros
Describe the course of the kidneys when developing
Develop in pelvis then ascend into abdomen with the final position taken by 12 week
Where is the bladder and urethra developed from?
Urogenital sinus (part of cloaca) which also gives rise to female and male repro tracts
What are the 3 stages of development of the nephrogenic cord?
Pronephros - non functional
Mesonephros - functional but transient
Metanephros - final kidney
What does the metanephric mesenchyme form?
Kidneys
What does the ureteric duct form?
Ureter
What does the nephric duct drain into?
Cloaca - common temporary outlet for digestive, urinary and genital tract in embryonic life
What are some types of renal anomalies?
Renal agenesis
Horseshoe kidney
Pelvic kidney
Duplex kidney
Duplex ureter and calyceal system
What is the cloaca?
Caudal end of the enfolded yolk sac
Covered by cloacal membrane
What forms the cloaca?
Fusion of the ectoderm and endoderm
What is formed from the urorectal septum dividing the cloaca?
Urogenital sinus and anal canal
What does the urogenital sinus form?
Bladder and urethra
What does the mesonephric duct form?
Incorporated into bladder as the trigone
Where does the indifferent gonad develop in?
Gonadal ridge - closely related to the mesonephros
Describe primordial germ cells during embryo development
Don’t originate in the gonadal ridge but migrate to gonads from endoderm lining of yolk sac via hindgut around 6 weeks of gestation
What does the epithelium of the gonadal ridge form?
Primitive sex cords
What does the germ cells and primitive sex cord form?
Indifferent gonads which is capable of developing into testis or ovary
What does the Y chromosome contain?
SRY gene - sex determining region of Y which produces testes determining factor - SRY protein
Describe SRY protein
Acts on indifferent gonad to promote the formation of testis
Describe the development of the ovary
Migrating germ cells enter ovary
Primitive sex cord extends into medulla but degenerates
Secondary sex cords develop and surround germ cells to form ovarian primordial follicles
When is the ovarian follicle pool determined?
20 weeks of gestation
Describe the development of the testis
Migrating germ cells enter testis
Primitive sex cords extend into medulla and form testis cords
What so testis cords transform into?
Future seminiferous tubules and rete testis
What are Sertoli cells derived from?
Surface epithelium under effect of AMH
What are Leydig cells formed from?
Intermediate mesoderm and produce testosterone from 8 weeks onwards
Describe testicular descent
Gonads originate in posterior abdominal wall
Testes reach deep inguinal ring by 7 months of pregnancy
What is the management for undescended testicle?
Cryptorchidism requires early surgery
