Lecture 7: Urogenital System

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Lecture 7:Urogenital System


Intermediate Mesoderm Forms Much of the Urogenital System


Paraxial mesoderm (somite) Intermediate mesoderm

Body cavity

Lateral plate mesoderm

Mesoderm in the Chick Embryo


3 Kidney Systems

4.5 weeks


5 Weeks

Urogenital Ridge (red box)

Intermediate Mesoderm Forms the Urogenital Ridge


The Ureteric Bud Forms as an Outgrowth from the Mesonephric Duct

5.5 Weeks


Collecting System Forms from the Ureteric Bud

6-7 Weeks


The Ureteric Bud Induces the Metanephric Blastema to Form Filtration Units


Molecular Regulation of Kidney Development


Kidneys Develop in the Pelvic Region


Ascent of the Kidneys


Pelvic and Horseshoe Kidneys

Ureter


Polycystic Kidney

Recessive form: 1:5000; cysts from collecting tubules; renal failure in infancy

Dominant form: 1:500-1000: cysts from anywhere; renal failure in adulthood


Duplications of the Ureters


Bladder Development

6 Weeks

7 Weeks

8 Weeks

Proctodeum


Bladder Development: Incorporation of the Mesonephric Duct


Possible Positions for Ectopic Ureters


Final Position of the Ureters and Mesonephric Duct (Vas Deferens)

Ejaculatory duct


Urorectal Septal Defects and Imperforate Anus


Urachal Abnormalities


Relationship of the Genital Ridge to the Mesonephric System

Cut Line


4 Weeks (early) 6 Weeks

Migration of the Germ Cells


6 Weeks

Relationship of Germ Cells to the Epithelium of the Genital Ridge


8 weeks 16 weeks

Sertoli cells: derived from epithelium; serve as nurse cells for sperm and produce antimüllerian hormone (AMH; also called müllerian-inhibiting substance [MIS])

Interstitial cells (of Leydig): derived from mesenchyme of genital ridge; secrete testosterone (mesonephric ducts, tubules, etc.; dihydrotestosterone, external genitalia)

Formation of the Seminiferous Tubules


16 Weeks 9 Months

Male Tubules and Ducts


Formation of Primary Oocytes and Follicular Cells

7 Weeks 20 Weeks


8 Weeks

9 Months

Derivatives of the Paramesonephric Ducts


Growth of the Urogenital Ridge Produces Fusion between the Paramesonephric Ducts


Formation of the Ovarian Ligaments


Induction of the Vagina by the Paramesonephric Ducts

9 Weeks 12 Weeks Newborn


Vaginal Development


Uterine Abnormalities


Testis and Ovary Development


Genetic Signals: Male vs. Female


External Genitalia: Indifferent Stage

4 Weeks 6 Weeks


10 Weeks Newborn

Penis and Scrotal Development


8 Weeks

Male


12 Weeks

Male


Hypospadias

Glandular Hypospadius Urethral and GlandularHypospadias


11 Weeks

Female


Female External Genitalia

Newborn

6 Weeks

5 Months


Female Pseudohermaphrodism (Adrenogenital Syndrome)


Androgen Insensitivity Syndrome (Testicular Feminization)


Signals for Sexual Differentiation

SRY

–SRY, +WNT4


Descent of the Testes

8 Weeks 19 Weeks

28 Weeks Newborn

Cryptorchidism: Failure of the testes to reach the scrotal sac (3% of newborns)


Layers Covering the Testis


Indirect Inguinal Hernias and Hydroceles


Remnants of the Mesonephric Duct in Females

Documents

Lecture 7: Urogenital System