Sexual development and Differentiation Flashcards
What is the difference between exocrine + endocrine glands?
Exocrine glands: Duct-based (e.g. sweat glands) - release their chemicals into the ducts
Endocrine glands: Ductless - release hormones straight into the circulatory system
- Organs with primary function of hormone release
Which structure in the hypothalamus controls the pituitary gland?
- Hypothalamus releases hormones which activate hormones in the pituitary and help regulate hormonal activity in the rest of the body
- Hypothalamus has a diverse regulatory function
- Paraventricular nucleus: Controls anterior + posterior pituitary gland function
Which hormones with some sex-related function are released by anterior and posterior pituitary?
Posterior pituitary: Involved with the release of oxytocin + vasopressin
Anterior pituitary: a regulatory centre involved in the cascade effect of the release of hormones lower down the system (e.g. adrenal gland + testes)
- Releases gonadotropins such as follicle stimulating hormone (FSH) and luteinising hormone (LH) that are involved in sexual functioning
What are the three main types of hormone + which glands release these?
Amino acid derivative hormones: Released by the adrenal medulla (e.g. epinephrine- adrenaline)
Peptide hormones (chains of amino acids): Released by pituitary gland
- Anterior pituitary releases prolactin, ACTH, and gonadotropins
- Posterior pituitary releases oxytocin (role in childbirth + lactation) and vasopressin (role in water regulation + mating-related behaviours)
Steroid hormones - synthesised from cholesterol, released by adrenal cortex
- Gonads also produce + release steroid hormones
Adrenal gland also releases sex hormones - important as if there’s problems with the gonads, testosterone can still affect sex drive
What is different between the action of steroid hormones on one hand and peptide and amino acid derived (AAD) hormones on the other?
Peptides + AADs are water soluble so have restrictions in how they can enter cells
- Cells have a fatty layer that restricts the entry of water soluble hormones but not fat soluble hormones
- So, water soluble cells rely in binding with receptors to transfer their signal through cell membrane
Steroid hormones are fat soluble so can penetrate cell membranes + bind to receptors in cytoplasm or nucleus
What are the two areas of the adrenal gland that secrete sex steroids and epinephrine?
Adrenal medulla: involved in releasing epinephrine (adrenaline)
Adrenal cortex: Releases cortisol + sex hormones such as testosterone
What is SRY + what effect does it have on gonads?
SRY = Sex determining region on the Y chromosome
When present, it masculinises the primordial gonads
At 6 weeks after contraception, the primordial gonads of XX and XY individuals are identical
- Under the influence of the Y chromosome, the medulla of gonad develops into a testis
- If Y chromosome not present, cortex of gonad develops into an ovary
How does the presence of testosterone affect the fate of the Wolffian + Müllerian systems?
When testosterone is present, the Wolffian (male) system develops and Müllerian-inhibiting substance causes the Müllerian system to degenerate
Which two areas of the hypothalamus play a role in male + female sex behaviour?
Ventromedial nucleus- female sexual behaviour
Medial preoptic area- male sexual behaviour
Which sex differences were noted in terms of adult behaviour?
- Many differences due to prenatal testosterone
- Large differences in neurological + psychiatric diseases
- Susceptibility to autism + dyslexia is greater in males
- Females are better on some verbal functions
- Males are better on some spatial functions
What does orchidectomy tell us about testosterone level and sexual desire in males?
Orchidectomy: Removal of testicles
- Sex drive is uncorrelated with blood testosterone
- So injecting testosterone does not increase sex drive
- Sexual desire and behaviour not straightforwardly linked to testicular testosterone
- Males who have had the procedure show a variety of responses ranging from total loss of sexual interest at one extreme to continued sexual engagement
How can small mutations have significant consequences for sexual development?
Androgenic Insensitivity Syndrome:
- Renders androgen receptors unresponsive
- Genetic male (XY)
- Testes release testosterone
- Body does not respond because of the mutation to the androgen receptor gene
- Development along the female lines
Congenital Adrenal Hyperplasia:
- Defect in the release of cortisol
- Excessive release of androgens (hyperandrogenism)
- Uncertain effect on sexual development
- CAH tends to result in male-typical behaviour in development + adulthood
5a-Reductase 2 deficiency:
- Genetic male (XY)
- 5a-Reductase 2 converts T into DHT
DHT drives primary male sexual development
- Body develops as female
- Male secondary sexual characteristics emerge during puberty
What are the differences between males + females and how might we determine whether these differences are social or genetic?
- Females experience higher levels of auto-immune/inflammatory disorders
- Males experience greater levels of cancer + infections
- Evidence suggests females have a stronger/more responsive immune system -> helps fight disease but leaves them more susceptible to auto-immune disorders
- Women generally score higher on average on personality scores
- Higher neuroticism in women strongly associated with anxiety
- Large sex differences in agreeableness
-Men more likely to engage in risk taking behaviour
What is the role played by prenatal androgen exposure in the development of gendered behaviour?
- Females with CAH (exposed to increased prenatal T) exhibit male typical behaviour
Evaluate the ratios of male:female neurological and psychiatric disorders
Males more likely to suffer from Severe learning disability, substance abuse, schizophrenia, dyslexia, ADHD, autism
Females more likely to suffer from Anorexia, bulimia, anxiety disorder, dementia, posttraumatic stress disorders
