Reproductive System Embryology PDF

1  Reproductive System Session 1 Origin of the Sexes Lecture 1 Development of Male and Female Reproductive System 2  Indifferent Embryo Between week 1 and 6, female and male embryos are phenotypically indistinguishable, even though the genotype (XX or XY)...

1  Reproductive System Session 1 Origin of the Sexes Lecture 1 Development of Male and Female Reproductive System 2  Indifferent Embryo Between week 1 and 6, female and male embryos are phenotypically indistinguishable, even though the genotype (XX or XY) of the embryo is established at fertilization. By week 12, some female and male characteristics of the external genitalia can be recognized. By week 20, phenotypic differentiation is complete. 3  Indifferent Embryo The indifferent gonads develop in a longitudinal elevation or ridge of intermediate mesoderm called the urogenital ridge Primordial germ cells arise from the lining cells in the wall of the yolk sac at weeks 3-4. At week 4-6, primordial germ cells migrate into the indifferent gonad.  Male germ cells will colonise the medullary region and the cortex region will atrophy.  Female germ cells will colonise the cortex of the primordial gonad so the medullary cords do not develop. 4 5 6  Sex determining region on Y Phenotypic differentiation is determined by the Sry gene, which is located on the short arm of the Y chromosome. The key to sexual dimorphism is 1. The Sry gene encodes for a protein called testes- determining factor (TDF). 2. As the indifferent gonad develops into the testes, Leydig cells and Sertoli cells differentiate to produce Testosterone and Mullerian-inhibiting factor (MIF), respectively. 3. In the presence of TDF, testosterone, and MIF, the indifferent embryo will be directed to a male phenotype. 4. In the absence of TDF, testosterone, and MIF, the indifferent embryo will be directed to a female phenotype. 7 The components of the indifferent embryo that are remodeled to form the adult female and male reproductive systems are: 1. Gonads 2. Paramesonephric (Mullerian) duct 3. Mesonephric (Wolffian) duct 4. Phallus 5. Urethral folds 6. Genital swellings 8 9  Indifferent Embryo Adult Female Adult Male Testes, Seminiferous Ovary, Primordial Follicles, Gonads Tubules, Tubuli Recti, Leydig Rete Ovarii Cells, Sertoli Cells Uterine Tubes, Uterus, Cervix, Upper Third of Paramesonephric Ducts Appendix Testes Vagina*, Hydatid of Morgagni SEED Epididymis, Ductus Appendix Vesiculosa, Duct of Deferens, Seminal Vesicles, Mesonephric Ducts Gartner Ejaculatory Duct, Appendix Epididymis Efferent Ductules, Mesonephric Tubules Epoophoron, Paroophoron Paradidymis Glance and Body of the Phallus Clitoris Penis Urethral Folds Labia Minora Ventral Aspect of the Penis Genital Swellings Labia Majora, Mons Pubis Scrotum * Lower two-thirds develops from vaginal plate of urogenital sinus Structures written by red color refers to vestigial structures Genital Ducts in the Sixth Week A: Male; B: Female 11  A:Genital ducts in the female at the end of the second month,B: Genital ducts after descent of ovary 12  Formation of the Uterus and Vagina A. 9 weeks, B. At the end of the third month, C. Newborn 13  Formation of the Uterus and Vagina A. 9 weeks, B. At the end of the third month, C. Newborn 14  Main Abnormalities of the Uterus and Vagina 15 A: Genital ducts in the male in the fourth month. B: Genital ducts after descent of the testis. 16 Descent of the Ovary and Testes The ovaries and testes develop within the abdominal cavity but later descend into the pelvis and scrotum, respectively. This descent involves the gubernaculum (a band of fibrous tissue) and the processus vaginalis (an invagination of peritoneum). 17  Testes 1. The gubernaculum extends from the testes to the genital swellings (forming the gubernaculum testes in the adult male, which anchors the testes within the scrotal sac). 2. The processus vaginalis forms the tunica vaginalis in the adult male. 3. Cryptorchidism??? 18 Descent of the testis: A. During the 2nd month; B. In the middle of the 3rd month; C. In the 7th month; D. Shortly after birth. 19 Drawing showing the coverings of the testes that are derived from constituents of the abdominal wall 20  Ovary 1. The gubernaculum extends from the ovary to the junction of the uterus and uterine tubes (forming the ovarian ligament in the adult female) and the continues into the labia majora (forming the round ligament of the uterus in the adult female). 2. The processus vaginalis is obliterated in the adult female 21 22 Development of Prostate Gland The prostate gland develops from multiple outgrowths of the prostatic urethra. Dihydrotestosterone (DHT) is the main mediator of prostatic growth in males. 23  External Genitalia Indifferent Stage A. Approximately 4 weeks; B. Approximately 6 weeks 24  External Genitalia in the Male A. Development of external genitalia in the male at 10 weeks; B. Transverse sections through phallus during formation of penile urethra; C. Newborn 25  Hypospadias and Epispadias Hypospadias showing the various Epispadias combined with exstrophy of locations of abnormal urethral orifices the bladder. Bladder mucosa is exposed 26 Development of the External Genitalia in the Female:- A: at 5 months; B: in the newborn 27  LANGMAN”S Medical Embryology PROBLEMS TO SOLVE??? 28 29