Sexuality and Sexual Development

Question 1

what makes us male or female (biologically)?

Answer 1

• chromosomes ~ XX = female ; XY = male
• prenatal stages ~ gonads development, internal organ development, external genitalia development
• puberty

Question 2

Development of the gonads

Answer 2

• ovaries in females
• testes in males
  up until the 6th week of development, no sexual differentiation has occurred ~ ovaries and testes are both able to develop, homologous structures
• at 6 weeks, the sex determining region of the Y - chromosome becomes active (SRY) ~ produces testis-determining factor, causes the development of male gonads
• w/o the SRY gene working, ovaries develop
• if the SRY gene is inserted into genetically female mice, testes develop

Question 3

what is the internal organ development?

Answer 3

• up until about 3 months, all fetuses have male “Wolffian” system and a female “Mullerian” system

Question 4

What else abput internal organ development?

Answer 4

• in males, testosterone causes Wolffian system to fully develop~ anti- mullerian hormone causes the degeneration of the wolffian system ; w/o anti-mullerian hormone, the female system will fully develop

Question 5

What is a trend in sexual development?

Answer 5

• in order to develop a biological male, hormones needs to influence the fetus
• if no hormones interact with the fetus, a female will develop - think of the female as the “default” , unless something changes the course of development, a female will develop automatically

Question 6

What is the external genitalia?

Answer 6

• males: penis and scrotum
  females: labia, clitoris, outer part of the vagina
• in males, testosterone and 5-alpha-reductase combine to form 5-alpha-dihydrotestosterone ; it causes the formation of male external genitalia
• in females, no hormone actiity is needed, the lack of activity leads to the formation of female external genitalia

Question 7

What is puberty?
in

Answer 7

• sexual maturation
• spermarche: first ejaculation for males
• Menarche: first menstrual period for females

Question 8

What did Pfeiffer (1936) observe?

Answer 8

• observed that testicular implants in neonatal female rats blocked ovulation
• attributed this to hormone differences

Question 9

So, is the pituitary gland where sexual differences exist?

Answer 9

• a later study transplanted adult male rat pituitary glands into adult females
• found that ovulation continued nomrally
• both male and female pituitary glands are capable of producing the same hormones
• the difference must be in the signals from the brain to the pituitary gland