Reproductive Systems Flashcards
What is the role of internal genitalia?
Transport, storage, nutrition & maturation of gametes
What is the role of the external genitalia?
Transfer of gametes
What is fertilisation?
Fusion of haploid gametes, ovum and sperm
When is genetic sex determined?
At fertilisation
XX female
XY male
Karyotype
When does genital development start?
Week 7
At similar time to gut rotation
Where does the Genito urinary system develop from in the three layered embryonic disc?
Intermediate mesoderm
What occurs at 3 weeks in the development of a gonad?
Primordial diploid germ cells arise in yolk-sac which reflect genetic sex of new individual
What occurs at 6 weeks in the development of a gonad?
Intermediate mesoderm becomes raised into paired genital ridges
Epithelium proliferates and penetrates mesenchyme to form primitive sex cords in an indifferent gonad
Germ cells migrate from yolk sac by amoeboid action and invade genital ridges and indifferent gonad
Induce development of indifferent/primordial gonad into testis or ovary
What state is the gonad in at week 6?
Indifferent/primordial
What happens to the indifferent gonad for it to become an ovary?
Germ cells are XX
Colonise cortex of primordial gonad
Surface epithelium continues to proliferate
Germ cells become surrounded by clusters of mesenchymal cells-primordial follicles
Remaining cords degenerate
What happens to the indifferent gonad if no germ cells arrive?
Cortex develops and they follow the ovary lineage
What happens to the indifferent gonad to become a testis?
Germ cells are XY (genes on Y chromosome influence subsequent
masculinisation)
Primitive sex cords continue to proliferate
Colonise medullary region of primordial gonad to form medullary or definitive sex cords
Dense tunica albuginea separates cords from surface epithelium
Sertoli cells differentiate from surface epithelium
Leydig cells differentiate from mesenchyme
Secretion of Testosterone by leydig cells in 8th week-influences further sexual differentiation of genitalia of embryo
Sex cords acquire a lumen at puberty as seminiferous tubules
Where do the gonads move to?
Gonads develop on posterior abdominal wall
Testis descends to end up in scrotum
Ovary descends to end up in pelvis
Describe the descent of the male gonad
Fold of peritoneum, processus vaginalis descends into labioscrotal folds (developing scrotum)
Passes through abdo wall, carries with it fascial layers of abdo wall
Gonad follows caudal descent as it is attached to abdominal wall by gubernaculum
Testis passes through inguinal canal into the scrotum
What forms the tunica vaginalis?
Lower part of processus vaginalis (fold of parietal peritoneum) forms tunica vaginalis
Why do the testis descend?
Testes need lower temperature of scrotum to permit maturation of sperm
When do testes descend?
28 weeks- migrate through inguinal canal
33 weeks - entering scrotum
Both testes in scrotum in 97% of male newborns at term
Gonad drags its supply lines with it
What is tissue is the testicle a derivative of?
Intermediate mesoderm derivative that develops high on posterior abdominal wall
Where does lymph drain to from the testicle and why?
Point of origin relevant to blood supply origin and lymph drainage
Blood supply & lymph vessels dragged with testicle
Lymph drains to para-aortic nodes ~L2 (not inguinal nodes)
Descends through inguinal canal (via gubernaculum)
Spermatic cord coverings = layers of anterior abdo. wall
What are the primordia for the male and female internal genitalia?
Fetus has primordia for male and female internal ducts Mesonephric ducts (Wolffian) - male Paramesonephric ducts (Mullerian) - female
Describe the development of the male internal genitalia
Para mesonephric (Mullerian) duct growth inhibited by Mullerian inhibitory hormone (MIH) Secreted by Sertoli cells Mesonephric (Wolffian) duct growth is stimulated by testosterone from leydig cells Develops into Epididymis, Vas deferens and Seminal vesicles
Describe the development of the female internal genitalia
Paramesonephric (Mullerian) duct develops into Fallopian tubes, Uterus, Cervix, Upper part of vagina
Mesonephric (Wolffian) duct regresses spontaneously
What do Uterine tubes and uterus develop from?
Paired paramesonephric ducts
What can Uterine & vaginal malformations lead to?
Primary amenorrhoea, infertility/problematic pregnancy