22 - Sexual Development (online)

Question 1

Difference between genotypic, phenotypic and gonadal sex

Answer 1

genotypic: XX (female) XY (male)
phenotypic: based on appearance, compared to ‘typical’ individuals with XX or XY chromosomes
gonadal sec: ovaries (female) testes (male)

Question 2

5th week embrological structures

quiz GN

Answer 2

• mesonephric kidney
• mesonephric/Wolffian duct
• paramesonephric/Mullerian duct
• indifferent gonad (cortex-potential ovary, medulla-potential testis)
• cloaca
• urogenital sinus

Question 3

XY hormonal triggers in embryological development

Answer 3

sex determining region of Y chromosome (SRY gene) produces testis determining factor (TDF):
- stimulates sertoli cells in gonad which create anti-mullerian hormone (AMH)
- mullerian ducts regress
- stimulates leydig cells in gonad which produce testosterone
- mesonephric ducts develop into male structures

Question 4

persisten mullerian duct syndrome

Answer 4

typically caused by lack of AMH

testicles can remain in the abdomen or pelvis

AMH - anti-mullerian hormone

Question 5

inguinal descent of the testes

GN step diagrams

Answer 5

• testes descend to the scrotum through the inguinal canal
• canal has a deep ring (opens to abdomen) and superficial ring (opens to scrotum)
• testes move downwards with the gubernaculum
• pulls in a section of peritoneum which seals
  
  • sealed portion called: obliterated processus vaginalis
  • gap called: scrotal cavity
  • lining of gap: tunica vaginalis

Question 6

what controls the movement of the testicles?

Answer 6

movement upwards:
- cremaster muscle (striated/voluntary)

compresses the scrotum (shortens, brings testicles closer):
- dartos muscle (smooth/involuntary)

Question 7

non-muscular anatomical structure that aids in the cooling of the testicles

Answer 7

pampiniform plexus
- plexus of cool venous blood beside warm arterial blood
- cools oxygenated blood before reaching testicles

Question 8

direct inguinal hernia

Answer 8

mostly occurs in males
- intestine protrudes into the inguinal canal where the portion of the peritoneum was sealed
- direct because it protrudes directly through that abdominal wall

Question 9

external genitalia development
(5 weeks)

Answer 9

5 weeks:
- genital tubercle
- labioscrotal swelling
- urogenital (urethral folds)
- urogenital sinus

Question 10

external genitalia development
(10 weeks)

Answer 10

in presence of androgens:
- urogenital folds meet and seal
- labioscrotal swellings swell towards eachother
- genital tubercle becomes the glans penis
- urogenital sinus remains open

no androgens:
- urogenital folds remain seperate, form vestibule and labia minora
- labioscrotal folds remain seperate, form labia majora
- urogenital sinus forms urethral opening
- vaginal orifice develops

Question 11

external genitalia development
(15 weeks)

Answer 11

in presence of androgens:
- labioscrotal swellings fuse to form the scrotum
- fusion line called midline raphe
- urogenital sinus seals, forms urethra with an opening at the tip of the penis

Question 12

XX intersex

Answer 12

chromosomally female with external genitalia that appear male (eg: fused labia majora and clitoromegaly)
- triggered by an excess of male hormones during fetal development
- typically caused by an overactive adrenal gland (excess androgens) - congenital adrenal hyperplasia (CAH)
- in adulthood, they will prodominantly appear phenotypically male

Question 13

XY intersex

Answer 13

chromosomally male with external genitalia that appear female - micropenis, cryptorchid (scrotum lacking testicles) and hypospadias (urethra opens at the base of the penis)
- triggered by inadequate supply of or insensitivity to male hormones (poor production or lack of receptors)
- typically caused by dysfunctional androgen receptors - androgen insensitivity syndrome
- in adulthood, they will prodominantly appear phenotypically female