✅ EMBRIOLOGÍA del SISTEMA GENITAL 👦🏻👧🏻 | Sistema UROGENITAL

Introduction

The video introduces the topic of embryology of the urogenital system, specifically focusing on the genital system. It mentions that sexual differentiation is a complex process involving genes and the Y chromosome plays a key role in sexual dimorphism.

Embryology of the Urogenital System Part Two

• Sexual differentiation is a complex process involving many genes, including some autosomal ones.

• The Y chromosome contains the gene called GEN SRY, which governs the formation of testicles.

• Gonads do not acquire male or female morphological characteristics before the seventh week of development.

• Primordial germ cells originate from the epiblast and migrate through the primitive streak towards the third week.

• During the fourth week, they migrate with an amoeboid movement through the dorsal mesentery and reach the primitive gonads at the beginning of the fifth week.

• If primordial germ cells do not reach the genital ridges by the sixth week, gonads do not develop.

• The Genital Crest epithelium proliferates shortly before and during primordial germ cell arrival and forms Primitive Sex Cords.

• In male embryos, Primitive Sex Cords continue to proliferate under the influence of SRY GENE on Y chromosome to constitute Testicle or Medullary Cords.

• Testicular cords are composed of primitive germ zones, Sustentacular Cells or Sertoli Cells, and Interstitial Leyding Cells located between them.

• Leyding cells begin to produce testosterone around eighth week of gestation, influencing sexual differentiation of genital ducts and external genitalia in males.

Embryology of Female Genital System

• In female embryos, Primitive Sex Cords dissociate into irregular cell groups occupying most of medullary part of ovary. These groups will later disappear and be replaced by vascular stroma, giving rise to the Ovarian Medulla.

• The superficial epithelium of the female gland continues to proliferate and creates a second generation of cords known as Cortical Cords in the seventh week.

• In the third month, these cords divide into isolated groups of cells that continue to proliferate and surround each Oogonium with a layer of epithelial cells called Follicular Cells, forming Primary Follicles.

Genital Ducts

• Male and female embryos initially have two pairs of genital ducts: Mesonephric Ducts (Wolff) and Paramesonephric Ducts (Müller).

• The Paramesonephric Duct empties into the abdominal cavity with a funnel-like structure in the cranial region. In the caudal region, it moves laterally with the mesonephric duct before crossing it ventrally and growing medially.

• Initially separated by a partition, the Paramesonephric Duct from one side merges with its counterpart to form the Uterine Cavity. The caudal tip of both canals projects into the posterior wall of the Urogenital Sinus, forming a small bump called Paramesonephric or Müllerian Tuber.

• The Mesonephric Ducts open into the Urogenital Sinus on both sides of the tuber.

Conclusion

The video concludes by summarizing key points about embryology of urogenital system part two, including sexual differentiation processes in males and females, development of testicles and ovaries, and formation of genital ducts.

Timestamps are approximate and may not be 100% accurate.

The Excretory Tubules and Paradídimo

This section discusses the excretory tubules along the caudal pole of the testis, known as Paragenital Tubules, which do not join the cords of the testicular network. These tubules are referred to as Paradídimo.

• The excretory tubules along the caudal pole of the testis are called Paragenital Tubules.

• These tubules do not join the cords of the testicular network.

• The vestiges of these tubules are given the name Paradídimo.

Main Genital Ducts and Epididymis

• With the exception of the most cranial portion, known as the appendix of Epididymis, mesonephric ducts persist and form the main genital ducts.

• Immediately below the entrance of vas deferens, mesonephric ducts elongate and contour to form Epididymis. From there to seminal vesicles, they receive a thick muscular layer and create vas deferens.

• The region behind seminal vesicles is called Ejaculatory Duct.

Female Genital Ducts

This section focuses on female genital duct development.

• Paramesonephric ducts become main genital ducts in women.

• Each paramesonephric duct has three parts:

• A vertical cranial part that empties into the abdominal cavity.

• A horizontal part that crosses the mesonephric duct.

• A caudal vertical part that merges with its counterpart from the opposite side.

• After the descent of the ovary, the first two parts become Uterine Tuba or Fallopian Tube, and the caudal parts merge to form Uterine Cavity.

• The merging of ducts in the midline creates a wide transverse pelvic fold called Broad Uterus Ligament.

• The Uterus and Wide Ligaments divide the pelvic cavity into Uterorectal Pouch and Uterovesical Pouch.

Vaginal Development

This section discusses vaginal development.

• Solid evaginations called Senovaginal Bulbs appear from the pelvic part of the breast, resulting in a solid vaginal plate. Proliferation continues at the caudal end of the plate, increasing distance between uterus and urogenital sinus.

• By the fifth month, this evagination is completely channeled, forming vaginal fornixes derived from paramesonephros.

• The vagina has a double origin:

• Upper part derives from uterine cavity.

• Lower part derives from urogenital sinus.

• The lumen of vagina and urogenital sinus are separated by a thin tissue plate called Hymen.

External Genitalia Development

This section focuses on the development of external genitalia.

• In the undifferentiated phase, mesenchymal cells migrate around the cloacal membrane to form cloacal folds.

• Cloacal folds unite with the cloacal membrane in the cranial position to form Genital Tubercle.

• In the caudal region, cloacal folds subdivide into anterior urethral folds and posterior anal folds.

• Another pair of elevations called genital bumps become visible on both sides of urethral folds, which later give rise to Scrotal Bumps in males and labia majora in females.

Male and Female External Genitalia Development

This section discusses the development of external genitalia in males and females.

• Androgens secreted by fetal testes influence male external genitalia development.

• The Genital Tubercle elongates to create the Phallus.

• The phallus pulls urethral folds forward, forming lateral walls of Urethral Groove.

• Urethral Plate is formed by epithelial lining of sulcus from endoderm.

• Urethral folds close over Urethral Plate, creating Penile Urethra at the end of third month.

• Distal portion of urethra appears during the fourth month, with ectodermal cells forming External Urethral Meatus.

• Estrogens stimulate female external genitalia development.

• The Genital Tubercle lengthens to create the Clitoris.

• Urethral Folds do not fuse and become Lips Minor.

Descent of the Testicles

This section discusses the descent of the testicles in both males and females.

Development of Male Genitalia

• The primitive excretory tubules, such as the epigenital tubules, come into contact with the testicular cords and form the deferent ducts of the testicle. These excretory tubules along the caudal pole of the testicle are called paragenital tubules.

• The mesonephric ducts persist and form the main genital ducts, except for the most cranial portion which forms the appendix of the epididymis.

• Below the entrance of the deferent ducts, the mesonephric ducts elongate and curve to form the epididymis. From its tail to the tips of seminal vesicles, these ducts receive a thick muscular layer and create the vas deferens.

• The region behind seminal vesicles is called ejaculatory duct.

Development of Female Genitalia

• The paramesonephric ducts develop into female genital ducts. They have three parts: a cranial vertical part that opens into abdominal cavity, a horizontal part that crosses over mesonephric duct, and a caudal vertical part that fuses with its counterpart from opposite side.

• After ovarian descent, first two parts become uterine tubes or fallopian tubes while caudal parts fuse to form uterine cavity.

• After fusion in midline, a broad transverse pelvic fold called Broad Ligament is formed extending from lateral sides of fused paramesonephric duct towards pelvic wall. This divides pelvic cavity into Uterorectal Pouch and Uterovesical Pouch.

• Solid evaginations appear from pelvic part of urogenital sinus, called Sinovaginal Bulbs, which proliferate to form a solid Vaginal Plate. The proliferation continues at the caudal end of the plate, increasing the distance between uterus and urogenital sinus.

• Vaginal fornices develop from paramesonephros. Thus, vagina has a dual origin - upper part derived from uterine cavity and lower part derived from urogenital sinus. A thin tissue plate called Hymen separates the vaginal lumen from the urogenital sinus lumen.

Development of External Genitalia

• In the third week of development, mesenchymal cells migrate around cloacal membrane to form cloacal folds. These folds unite cranially with cloacal membrane to constitute genital tubercle. Caudally, they subdivide into anterior urethral folds and posterior anal folds.

• Another pair of elevations called genital swellings become visible on both sides of urethral folds, later giving rise to scrotal swellings in males and labia majora in females.

• Male external genitalia development is influenced by androgens secreted by fetal testicles. The genital tubercle elongates rapidly to form phallus, pulling urethral folds forward to create lateral walls of urethral groove. The epithelial lining originating from endoderm forms urethral plate which eventually closes over to form penile urethra by the end of third month. Distal portion of urethra appears during fourth month when ectodermal cells from glans penetrate to form short epithelial cord that later develops a lumen, known as external urethral meatus.

The transcript is in Spanish, and the notes are provided in English as per the given instructions.

Desarrollo en la Región Inguinal

This section discusses the development in the inguinal region.

Development in the Inguinal Region

• The transcript does not provide any specific information or details about the development in the inguinal region.

• No timestamps are available for this section.