Sex Determination and Differentiation Flashcards
What hormones are necessary for breast milk ?
Hypothalamic Hormone: PRH
Anterior Pituitary Hormone: Prolactin
Non-Endrocrine tissue: Breast
What is special about Prolactin and GH?
They are the only two anterior pituitary hormones whose secretion is controlled by BOTH releasing hormones and inhibiting hormones
Structure of the breast
- Mammary gland has 15-20 milk lobes divided by adipose tissue.
- Each lobe is subdivided into lobules, which contain alveoli, which secrete milk
- Alveoli secrete milk into secondary tubules, which form into mammary ducts, then the lactiferous duct, then drain at the nipple
- The lumen of the duct is where milk accumulates during nursing.
Negative Inhibition of prolactin for breast milk
During pregnancy milk production is prevented because the estrogen is high, so secretion of prolactin is inhibited.
>estrogen works o hypothalamus which secretes PIH that acts on to inhibit the anterior pituitary and prolactin secretion
After birth, the placenta is gone, so estrogen levels go down, and there is an increase in secretion of prolactin.
Hormones needed to release breast milk
Prolactin from the ANTERIOR pituitary for milk production
Oxytocin from POSTERIOR pituitary for milk release
>release can be stimulated by visual or auditory cues (brain stimuli) or even the thought of the child
Why is oxytocin made by both males and females?
Oxytocin is a neuropeptide that plays a key role in social attachment and affiliation in non-human mammals and causes a substantial increase in trust among humans
What is the SRY gene ?
Sex Determining Region of the Y
Found on the Y chromosome of all animals and is highly conserved; thought to be important for male determination
How does sex differentiation begin in the fetus ?
Begins with the development of the gonad from a bipotential primordium at 6 weeks
Describe how females are determined post-bipotential primordium
At 10 weeks female sex is determined.
- There is an absence of SRY protein - gonadal tissues develops into ovaries
- Since there is no testosterone, the Mullerian inhibition factor (MIF) is not made from Sertoli cells. So Wolffian duct degenerates. MULLERIAN DUCT IS MAINTAINED.
- Absence of MIF allows the Mullerian duct to become the Fallopian tube, uterus and vagina.
Describe how males are determined post-bipotential primordium?
Sex determination for males occurs at 10 weeks
- Presence of SRY protein - gonadal tissue develops into testes
- Presence of testerone, so MIF is made from Sertoli cells which causes the Wolffian duct to be maintained, while the Mullerian duct degenerates
- Testosterone allows Wolffian duct to become seminal vesicle, vas deferens, and epididymis
Genetic markers of males and females
Genetic Females are XX
> Females inherit one X from each parent
Genetic Males are XY
>Males inherit one X from mother and Y from father
** Y chromosome carriers SRY gene
SRY gene recombination
SRY gene is normally found on the Y chromosome but due to recombination, the SRY gene can transfer onto the X chromosome and can result in XX males and XY females
True hermaphrodites
An intersex condition where individuals have both ovary and testis tissue, can be 46XX with SRY mosaicism
>karyotypes are 47XXY, 46XX/46XY, or 46XX/47XXY, and various degrees of mosaicism
Pseudohermaprodites
Pseudohermaphroditism is an ENDOCRINE DISORDER
>These are MALES with a defective gene for 5a-reductase
Congenital condition - person has external genitalia of one sex, and internal sex organs of the other sex
describe the condition of pseudohermaphroditism (male)
- normal testosterone
- defective 5a-reductase
- inadequate levels of DHT
- inappropriate exposure to androgens during early gestation
- male external genitalia and prostate gland fail to develop fully during fetal development
- at birth they appear female and are raised as such
- at puberty testes secrete testerone again
- causes masculinization of the external genitalia, voice, etc.
