Sexual Development - 21 Flashcards
Types of Sex
-genetic sex (xy male, xx female)
-phenotypic sex (appearance)
-gonadal sex (ovaries or testes)
-behavioural/psychological (how the person self-identifies)
-gender identity can be different than assigned sex (transexual)
Embryo at 5 Weeks LABEL
-mesonephric kidney (completely disapears)
-Mesonephric/Wolffian duct (comes out of mesonephric kidney)
-Paramesonephric/Mullerian duct
Indifferent gonad (hasn’t yet differentiated into ovary or testes)
Outside is potential ovary, inside/stroma is potential testes
*-Urogenital sinus (ducts terminate and leak through)
Cloaca (where ducts meet; eventually divides into rectum and bladder)
Urogenital development
- Urinary and reproductive systems develop together
- Right of metanephric duct is a bud, which forms the metanephric kidney (no bud = no kidney)
Kidney ascends, gonad descends, mesonephric duct follows gonad (makes vas deferens in males)
Mesonephric duct creates the ureter
XY genotype: start with Y chromosome has SRY gene (sex-determining region of the Y)
Label slide
- Makes TDF (testis determining factor)
-Stimulates Seroli cells in gonad (makes anti-
Mullerian hormone (AMH), causes regression of Mullerian ducts, female reproductive ducts)
-Stimulates Leydig cells in gonads to make
testosterone and other androgens (develops mesonephric ducts, making male reproductive structures)
XX genotype: outer part of indifferent gonad develops into ovary
-Mullerian ducts create uterine tubes, fuse to make uterus and some cervix and vagina
-Ovary descends into the pelvis
Persistent Mullerian duct syndrome
- Lack of anti-Mullerian hormone (or lack of receptors) leads to the creation of testicles and a persistent paramesonephric duct
o The testicles don’t descend properly because the duct didn’t regress and hold the testicles in the abdomen/pelvis
Inguinal descent of the testes
- Descent occurs through inguinal canal
o Deep ring opens into abdomen, superficial ring opens into scrotum - Gubernaculum moves the testes down to the scrotum
o Some peritoneum is pulled down through the inguinal canal; seals off to prevent bowel from coming in - Sits between the anterior superior iliac spine and the pubic symphysis
- Genital tubercle develops into the penis or clitoris; labioscrotal swelling becomes either the labia or scrotum
Hydrocoele
- Obliterated processus vaginalis: area where lingual was obliterated
- Scrotal cavity is a potential space formed from peritoneum
- Visceral layer of tunica vaginalis is a layer of peritoneum; superficial is the parietal layer
- Epididymis leads to vas deferens from testicle
- Damage to testicle results in the buildup of fluid in the scrotal cavity
o Regular fluid: hydrocoele
o With blood: hematocoele
Orchiopexy
- If testicle does not descend
- About 4% of male newborns; more common in premature babies (most descent happens in third trimester)
o If baby is premature, testicle will descend 75% of the time - If testicle doesn’t descend, orchidopexy can be done
o Testicle can’t be left in the abdomen; could become cancerous (help it descend or remove it)
o Artery, vein, nerve, and vas deferens are taken with it
o Seal off superficial ring of inguinal canal
Male gonads
- Outside the body for optimal sperm development (2-3 C below body temperature)
- Cremaster muscle moves testicles closer or further from body
o Cremaster muscle moves scrotum (part of internal oblique; striated)
o Dartos muscles pushes them scrotum (smooth) - Pampiniform plexus
o Gonadal artery is surrounded by venous plexus; warm arterial blood comes down, venous blood in plexus (cooler) cools down the arterial blood to maintain optimal temperature - Scrotum and testicles are exposed to damage
o Males can get inguinal hernias (inguinal canal leaves a weak point in the abdominal wall; makes it easier for bowel to push out of the abdominal cavity and into the inguinal canal
o Direct hernia (went directly through the abdominal wall); indirect is seen in newborns/young children with testicles (it goes through the inguinal canal, which hasn’t closed off yet)
o Acquired hernia
Male external genitalia development
- Indifferent stage (5 weeks)
o Genital tubercle, labioscrotal swellings on each side, with urogenital (urethral) folds in between
▪ GT: penis or clitoris
▪ LS: labia majora or scrotum
▪ Urethral folds: labia minora, part of urethra
o Urogenital sinus right down the middle (opens to the bladder later on) - 10 weeks (under influence of androgens in all fetus)
o Urethral folds meet and seal up to make a male urethra (in females, the folds don’t seal)
o Labioscrotal swellings swell towards each other
o Tip of genital tubercle becomes glans penis
o Still has urogenital sinus (still just an opening) - Further development (? weeks)
o Development of glans penis from genital tubercle
o Labioscrotal swellings join to form scrotum (join in the midline raphe; more obvious is newborns)
o Urethra has sealed off (from urethral folds), empties at glans penis
Female external genital development
- Labioscrotal swellings don’t fuse to make labia majora
- Urogenital folds don’t fuse to make labia minora
- Urethra is in the vestibule (where the urogenital folds didn’t fuse, between labia minora)
o Short urethra - Genital tubercle becomes clitoris
- Result in the absence of androgens
Intersex (disorder of sexual development, DSD)
- Having both male and female sexual characteristics and organs; ambiguous assignment of male/female cannot be made
- About 1-2/1000 newborns have some sort of surgery to “correct” ambiguous genitalia
- About 4/100 newborns fulfill the broadest definition of intersex
o Ex. baby born with 2 undescended testicles - There are very few gonadal intersexes (someone with ovaries and testes)
o More uncommon that they both work properly
XX intersex
X intersex
* 2 XX chromosomes; external genitalia appear male
* Typically, because of virilization of female fetus by androgens
o Testosterone usually comes from overactive adrenal gland in fetal development
* Fused labia majora, clitoris is large (clitoromegaly)
* Called congenital adrenal hyperplasia (CAH)
XY Intersex
- XY chromosomes; external genitalia is incompletely formed among male pattern
o Micropenis, cryptorchid (no testicles), hypospadias (urethra opens at base of penis; urethral folds didn’t fuse to make urethra) - Many causes; generally due to inadequate supply or receptors to androgens
o Androgen insensitivity syndrome (AIS): poorly formed/absence of receptors - Typically no female internal organs (anti-Mullerian hormone prevents this), except short, blind-ended vagina
