Lecture 2: Pt 2. Human Development and Biologic Sex

we have this many copies of each gene

two copies

fertilization

Process in sexual reproduction in which male and female gametes (sperm and egg) join to form a new cell called a zygote

Sertoli cells

provide metabolic support for the spermatids and make Mullerian Inhibiting Substance (MIS)

male gonads

testes

Genital folds (aka urogenital folds)

portion of indifferent genitalia that will become either the labia minora and vestibular bulbs or part of the penis

Autosomes

The first 22 pairs of chromosomes containing genetic information necessary to build and operate a human body

Testosterone

Testosterone in males stimulates the growth of the male sex organs in the fetus and the development of the male sex characteristics during puberty

XY

Male (SRY gene is present)

SRY gene

sex determining region of the Y chromosome; if present, signals the gonads to develop into testes. If absent, gonads will become ovaries.

Zygote

the fertilized egg

Diploid

an organism or cell having two sets of chromosomes or twice the haploid number: example is the zygote and all other body cells except gametes

Testicular descent

When the testes move out of the abdomen and down into the scrotum in late fetal life or in the first few months after birth

Female Gonads

Ovaries

Urogential sinus

part of indifferent genitalia that will become either urethra and lower part of vagina or urethra

Genital Tubercle

portion of indifferent genitalia that will become either the clitoris or part of the penis

Labioscrotal swelling

portion of indifferent genitalia that will become either labia majora or scrotum

Wolffian ducts

Early embryonic ducts that develop into male internal genitalia if testosterone is present and seen. If no testosterone present, will degenerate.

Indifferent Genitalia

In early embryonic development: genital tubercle, (uro)genital folds, and labioscrotal swellings.

Cryptorchidism

undescended testicle

Embryogenesis

the formation and development of an embryo, the first eight weeks of fetal development

Hypospadias

abnormal opening of the male urethra on the undersurface of the penis 

Female Development

Default development pathway when no testosterone is present. Wolffian ducts degenerate and Mullerian ducts develop.

Mullerian-inhibiting Substance (MIS)

Produced by the fetal testes, will cause degeneration of the Mullerian ducts

Mullerian ducts

Earlier embryonic ducts that develop into female internal genitalia (fallopain tubes, uterus, upper vagina) in the absence of MIS. If MIS is present, they will degenerate.

Leydig cells

A cell that produced testosterone

XX

female (No SRY gene present)