Embryology Flashcards
What is gastrulation?
Formation of trilaminar disc (ectoderm, endoderm, mesoderm)
What are the 3 main groups of the mesoderm?
Paraxial
Intermediate
Lateral plate
How are the definitive endoderm and mesoderm formed?
Invaginatino of epiblast cells through primitive streak
From what layer is the urogenital system derived?
Immediate mesoderm
What are the 3 parts to the urinary system?
Pronephric
Mesonephric
Metanephric
What will the metanephric system form?
Kidney
In what structure will excretory ducts enter?
Cloaca
How will primitive germ cells from the yolk sac enter the immediate mesoderm?
Via migration through the dorsal mesentery
What weeks will the PGCs from the yolk sac migrate to the mesoderm?
4-6
What is the genital ridge?
Coelomic epithelium proliferation
What are the primitive sex chords?
Proliferating epithelium forming somatic supportive cells enveloping the PGCs
What are the 2 genital ducts?
Mesonephric (wollfian) = male
Paramesonephric (mullerian) = female
Where will the mesonephric and paramesonephric ducts connect?
Posterior wall of urogenital sinus
At what time will sexual differentiation occur?
Week 7
What determines the male development?
Presence of SRY (short arm of Y chromosome) transcription factor
What is the function of SRY?
Formation of sertoli cells
What will somatic support cells in the male form?
Sertoli cells
What will the primary sex cords in the male form?
Testis which engulf the PGCs
What will the rete testis connect?
Mesonephric tubules to testis cords
What lies between the coelomic epithelium and the testis cords?
Thickened layer of connective tissue; tunica albuginea
What will sertoli cells secrete in terms of male development?
AMH
Gonadal ridge cells to form leydig cells (testosterone)
What will testosterone help develop in the male?
Epididymis
Vas deferens
Seminal vesicles
External genitalia
What will AMH do in male development?
Degeneration of paramesonephric duct
What will persistent mullerian duct syndrome present as?
Uterus, vagina and uterine tubes
Testes in ovarian localtion
Male external genitalia
At what level do the testes originate?
T10
How are the testes pulled through the abdominal cavity?
Fibrous attachment to the gubernaculum
What is undescended testes called?
Cryptorchidism
When do the male accessory glands develop?
Week 10
What are the male accessory glands?
Prostate endoderm invagination) Bulbourethral glands Seminal vesicle (mesonephric duct)
What will germ cells differentiate into?
Oogonia and then to primary oocytes
What will somatic support cells in females differentiate into?
Granulosa cells
Surround primary oocyte
What will the female gonad form?
Primordial follicles and theca cells
What will the paramesonephric ducts in females form?
Uterine tubes
Uterus
Superior vagina
What are the 3 parts to the paramesonephric duct?
Cranial; opens into the coelomic cavity
Horizontal; crosses the mesonephric duct
Caudal; fuses with the paramesonephric duct on opposite side
What forms the uterovaginal canal?
Fused caudal portion of paramesonephric duct
What forms the vaginal lumen and fornices?
Vacuolization of paramesonephric portion of vag and sinuvaginal bulbs
When will external genitalia be distinguishable?
Around week 14
How is the spongy urethra formed?
Proximal to distal zipping of urethral groove
How is the prepuce (foreskin) formed?
Circular ingrowth of ectoderm around the periphery of the glans (week 12)
What is hypospadias?
External urethral opening lies in an abnormal position along the ventral aspect of penis
