ERS20 Development Of Reproductive System Flashcards
Male reproductive system
- Testis
- germ cell production
- hormone production - Epididymis
- reservoir for sperm (sperm maturation) - Vas deferens, Ejaculatory duct
- transport organ for sperm - Urethra
- transport organ for sperm
- urinary organ - Accessory sex glands (Prostate, Seminal vesicles, Bulbourethral gland)
- production of secretions (semen) - Penis
- copulatory and urinary organ
Female reproductive system
- Ovary
- germ cell production
- hormone production - Uterine tube
- site of conception
- transport organ for zygote - Uterus
- organ of incubation parturition - Greater and Lesser vestibular glands
- production of secretions - Vagina
- copulatory organ
- parturition - Labia majora and minora, Clitoris
- copulatory organs
Development of gonads
Indifferent / Bipotential stage (Morphologically identical, Primitive gonads)
1. Endoderm
—> endodermal cells from Allantois / Yolk sac migrate (active ameboid movements)
—> via Gut tube, Dorsal mesentery
—> to Gonadal ridges
—> become Primordial germ cells (earliest undifferentiated reproductive cells, large, spherical)
—> settle in between Gonadal cords
—> Sperms, Oocytes
- Mesoderm
—> Gonadal ridge (part of Urogenital ridge (i.e. from Intermediate mesoderm))
—> 2 types of somatic cells: - Mesenchymal cells (multipotent embryonic CT)
- Epithelial cells:
- **Gonadal cords —> finger-like extensions formed from proliferation of epithelial cells between mesenchymal cells
- **Mesodermal epithelium —> posterior abdominal wall —> cover Mesenchyme
Differentiation stage
- Primordial germ cells (Endoderm)
—> Spermatogonia / Oogonia
—> Spermatozoa / Ovum - Gonadal cords (Epithelial cells)
—> Seminiferous cords (male) / Primordial follicles (female)
—> Sertoli cells (male) / Granulosa cells (female) - Mesenchymal cells
—> Interstitial cells (supporting germ cells)
—> Leydig cells, other interstitial cells, Tunica albuginea, Interlobular septa, Mediastinum testis (male)
—> Theca cells, other interstitial cells, Tunica albuginea (female) - Mesodermal epithelium
—> Mesothelium
—> Visceral layer of Tunica vaginalis (male) / Germinal epithelium (female)
Development of Genital ducts and Accessory organs
Indifferent stage
1. Upper part:
Nephrogenic cord (part of Urogenital ridge, from Intermediate mesoderm)
—> Mesonephric ducts (Wolffian ducts) + Paramesonephric ducts (Mullerian ducts)
- Lower part:
Cloaca (from Endoderm)
—> Urogenital sinus
Differentiation stage
1. Mesonephric ducts (Wolffian ducts)
—> Transformation (male) / Degeneration (female)
—> Ducts: Efferent ductules, Epididymis duct, Vas deferens, Ejaculatory duct (male)
—> Glands: Seminal glands (male)
- Paramesonephric ducts (Mullerian ducts)
—> Degeneration (male) / Transformation (female)
—> Ducts: Uterine tubes, Uterus, Upper Vagina - Urogenital sinus
—> Distal urethra (male) / Uterovaginal primordium (female)
—> Penile urethra, Prostate, Bulbourethral glands (male)
—> Lower Vagina (with hymen), Greater vestibular glands (of Bartholin) (female)
Development of external genitalia
Indifferent stage
- Genital tubercle (just above Cloacal membrane)
- Urogenital folds
- Labioscrotal swellings
Differentiation stage
1. Genital tubercle
—> Primordial phallus (long) / Primordial phallus (short)
—> Glans penis, Shaft of penis / Clitoris
- Urogenital folds
—> fuse along ventral side of penis / NOT fuse
—> Penile urethra / Vestibule, Labia minora - Labioscrotal swellings
—> Scrotal folds fuse / NOT fuse, Labial folds
—> Scrotum / Labia majora
Homology
Development of organs in embryo
- in same manner
- from same origin (primordia)
- but look / perform differently
Examples:
- Testis, Ovary
- Scrotum, Labia majora
Gonads development: Indifferent stage
Upper lumbar spine
Urogenital ridge (bulge)
1. Gonadal ridge (origin of gonads)
2. Nephrogenic cord (origin of gonadal ducts + urinary system, contain Mesonephric duct + Paramesonephric duct)
Gonadal ridge:
- Mesothelium (posterior abdominal wall, covering Mesenchyme)
- Mesenchyme
- Gonadal cords —> finger-like extensions formed from proliferation of epithelial cells between mesenchymal cells
Endodermal cells
—> migrate from Allantois / Yolk sac (active ameboid movements)
—> via Gut tube, Dorsal mesentery
—> to Gonadal ridges
—> become Primordial germ cells (earliest undifferentiated reproductive cells, large, spherical)
—> settle in between Gonadal cords
—> Sperms, Oocytes
Overall:
Gonad = Mesothelium + Gonadal cords + Mesenchyme + Primordial germ cells
Male Gonads development: Differentiation stage
7th week:
Gonadal cords (enlarge, well-defined) + Germ cells
—> elongate
—> Seminiferous cords (no lumen until puberty)
—> Seminiferous tubules (area with Germ cells), Straight tubules (distal part without Germ cells)
—> Straight tubules continuous with Rete testis (from Mesonephric duct)
Seminiferous tubules
—> ***Sertoli cells
Mesenchyme
—> Interstitial cells (e.g. ***Leydig cells, Myoepithelial cells), Tunica albuginea (thick layer underneath Mesothelium), Interlobular septa, Mediastinum testis
Mesothelium
—> cover developing testes
—> Tunica vaginalis
Female Gonads development: Differentiation stage
7th week:
Gonadal cords (shorter) + Germ cells
—> Follicular / **Granulosa cells (from epithelium) + Oogonia (active cell division during fetal life, many degenerate before birth, no after birth —> become Primary oocytes)
—> **Gonadal cord break up
—> Primordial follicles (isolated cell clusters)
—> Gonadal cord extends into medulla (i.e. Rete ovarii)
—> rudimental Ovary
—> Rete ovarii (network of canals) degenerate (Ovary no relationship with Mesonephros)
Mesenchyme
—> ***Theca cells, other interstitial cells, Tunica albuginea (female)
Mesothelium
—> cover developing ovaries
—> Germinal epithelium (female)
Genital ducts and Accessory ducts development: Indifferent stage
Nephrogenic cord (Intermediate mesoderm)
Upper part (Genital ducts):
- Mesonephric (Wolffian) ducts (paired) (form Mesonephros with Nephron-like tubule)
- initially urinary function, later superseded by Metanephros - Paramesonephric (Mullerian) duct (paired)
- open cranially into abdominal cavity
—> Both ducts grow caudally open into Cloaca
Lower part:
Cloaca (Endoderm):
- common space at the end of digestive tract for release of both excretory and genital products
- initially closed by Cloacal membrane (no opening initially) —> later rupture
- split by Urorectal septum into Urogenital sinus (anterior) + Rectum (posterior)
- Urogenital sinus —> Urinary bladder + Urethra
- Allantois —> Urachus
Male Genital ducts and Accessory ducts development: Differentiation stage
8th week:
Mesonephric duct (Wolffian)
—> **Anti-Mullerian hormone (AMH) (from Testis)
—> cause Müllerian ducts to disappear
—> Mesonephric tubules fuse with Rete testis —> Efferent tubules (屬於Mesonephric duct)
—> **Testosterone (from Testis)
—> converts Mesonephric duct (becomes thick smooth muscle, narrow lumen)
—> Epididymis, Vas deferens, ***Seminal vesicle, Ejaculatory duct (open into Urogenital sinus)
—> DHT controls Prostate development
Urogenital sinus
Upper portion: Urinary bladder
Lower portion: Distal urethra
—> Penile urethra, **Prostate, **Bulbourethral glands
記住:
- Seminal vesicle —> Mesoderm (Mesonephric duct)
- Prostate, Bulbourethral glands —> Endoderm (Cloaca)
Female Genital ducts and Accessory ducts development: Differentiation stage
8th week: Paramesonephric duct (Mullerian) —> ***Absence of Testosterone —> cause Mesonephric duct to degenerate —> ***Absence of Anti-Mullerian hormone —> Paramesonephric ducts grow caudally —> Fallopian tube, Uterus (fused Paramesonephric ducts at midline), Upper vagina (Lower vagina from Urogenital sinus)
Paramesonephric ducts
—> partially fuse with Uterine septum (disappear later)
—> fuse with Sinus tubercle (Cloaca)
—> Sinovaginal bulb (Uterovaginal primordium)
Urogenital sinus (Urinary bladder moved aside)
—> a mass of cells form Sinus tubercle
—> fuse with Paramesonephric ducts
—> Sinovaginal bulb (Uterovaginal primordium)
***Sinovaginal bulb (Uterovaginal primordium)
—> centre degenerate —> a space
—> space enlarges —> a lumen
—> Vagina (with hymen), Greater vestibular glands (of Bartholin)
A mass of cell/tissue progressively grows caudally (向下劈開)
—> split Urogenital sinus
—> separate Urethra opening from Vagina opening
—> Urethra and Vagina separated
Cloacal membrane rupture
—> forming different openings
—> Urethra (superior), Vagina (open into Vestibule), Anus (posterior)
Congenital abnormalities of Uterus
- Paramesonephric ducts do not fuse
—> Double uterus - Uterine septum does not disappear
—> present in adult - One part of reproductive system underdeveloped / degeneration of one Paramesonephric duct
—> Rudimentary horn / Absent of half of uterus
External genitalia development: Indifferent stage
Just above Cloacal membrane (anterior of embryo)
—> Genital tubercle (proliferating Mesenchyme (Mesoderm) —> visible small bulb, origin of external genitalia)
—> rapidly elongate
—> Phallus
Each side of Cloacal membrane
—> **Urogenital folds x2 (中間) (Rectum and Urogenital sinus not separated yet) + Labioscrotal folds / swellings x2 (側面)
—> Urogenital folds pulled by elongating Phallus (become oval shape)
—> space between Urogenital folds: **Urethral groove (posterior wall formed by Cloacal membrane —> rupture to become Urogenital + Anal openings)
Anal folds (below Urogenital folds)
—> form Anus
—> fuse together around Anal opening
- Distinguishing sexual characteristics begin to appear during 9th week
- External genitalia not fully differentiated until 12th week
Male External genitalia development: Differentiation stage
10-12th week:
Genital tubercle
—> Primordial phallus (long)
—> Glans penis, Shaft of penis
—> Tip of Glans penis
—> Ectodermal / Endodermal cord grows towards Spongy urethra
—> Canalise and join Penile urethra
—> dilated part: Navicular fossa
—> move External urethral orifice to tip of Glans penis
—> fold of skin at base of Glans penis grow distally and surround entire Glans
—> Prepuce (包皮)
Urogenital folds
—> fuse
—> Inferior aspect closing Urethral groove
Urethral groove (Cloacal membrane)
—> extend on ventral side of Phallux
—> Penile urethra (meeting line visible as Perineal raphe)
Labioscrotal swellings
—> Scrotal folds fuse
—> Scrotum (meeting line visible as Perineal raphe)
—> 2 compartments separated by Median septum
Perineal raphe
- Fusion zone visible from Anus to apex of Phallus on underside of penis
