Reproduction system: during the lifetime Flashcards
What is the role of the SRY gene?
It is the Sex-determining Region on the Y chromosome
What is sex determination?
The primitive gonad to develop into either a testis or an ovary
What is sex differentiation?
The phenotype development of genital structures
In mammals vs other classes how is sex determined?
Genetically in mammals, in other species can be determined by temperature (reptiles), social pressures (fish) etc
How many chromosomes do humans have? How many of them are non-sex linked?
46 chromosomes/23 pairs, 22 pairs are autosomal (1 pair of sex chromosomes FYI)
What is the genetic change the differentiates between sexes in mammals?
The presence of a Y chromosome (i.e. XY) creates a male, the absence of a Y chromosome (i.e. XX) creates a female
What does the SRY gene do?
Provides the pathways for the testes to develop
What does the presence of a testis determine?
Determines the sexual fate of the embryo (i.e. no testis/SRY gene = female, testis/presence of SRY gene = males)
What internal genitalia’s are present in only developed males OR females but both are present in the early embryo?
Mullerian duct (female) and the Wolffian duct (male)
What is the gonad considered when it is non-sex differentiated?
Bipotential gondad
What does the Mullerian duct develop into in females? What happens to the Wolffian duct?
The internal female genitals (i.e. uterus, uterine duct and upper vagina)
Wolffian duct regresses
What does the Wolffian duct develop into in males? What happens to the Mullerian duct?
Develops into the internal male genitals
Mullerian duct regresses
How does the development of the female genitals from the Mullerian duct differ from the development of the male genital from the Wolffian duct?
The female genitals will develop spontaneously (i.e. no hormones are needed to drive the development of the female genitals or the regression of the Wolffian duct)
The male genitals require hormones to drive their development (i.e. Testosterone needed to drive Wolffian duct development and Anti-mullerian hormone [AMh] needed to cause Mullerian regression)
Label the diagram. Why are there no arrow in the female genitalia development vs males development?
It happens spontaneously in females (i.e. default mode) but males need the hormones to drive their development
What cells cause the suppression of the Mullerian duct in males? How do they do this?
Sertoli cells produce anti-mullerian hormone (AMh)
What cels cause the development of the Wolffian duct in males? How do they do this?
leydig cells produce testosterone
What does the Wolffian duct develop into in the males?
The epididymis, vas deferens and seminary vesicles
How does the speed of development of male and female sex differentiation differ? Why?
The male sex differentiation develops faster (in about 7 weeks) vs female sex differentiation (in about 10 weeks) as the male process is hormone driven
What does the Mullerian duct develop into in the female?
The fallopian/uterine tubes, uterus, cervix and upper vagina
What do both the male and female external genitalia develop from?
A single biopotential precursor (not the biopotential gonad as this develops into the internal organs FYI)
How does external genitalia differ between males and females?
Males: Urethral folds fuse and enclose the urethral tube forming the shaft of the penis, labioscrotal swellings fuse forming scrotum, glans area expands forming the the glans penis
Females: Urethral fold and labioscrotal swellings remain open and gnalns area forms clitoris
What hormone drives the development of male and female external genitalia?
For males it is androgen (a male sex hormone such as testosterone)
For females it is the default developmental mode and doesn’t require any hormones
What is androgen resistance syndrome? What causes it?
Where a person is XY (i.e. genetically a male) but has the physical appearance of a female
It is when the person has a mutation in their androgen receptor gene which prevents androgen functioning
What is the purpose of puberty?
It is the ‘re-awakening’ of the reproductive system
What is the first endocrine (i.e. hormonal) sign of puberty?
An increase in plasma LH which is due to an increase in GnRH release
When does GnRH secretion occur during puberty?
During early puberty during the night, late puberty throughout the day
What are the major sex steroids? How do they respond to increasing plasma LH during puberty?
Males = Testosterone, Females = Oestrogen
Each increases respectively in each sex due to an increase in LH
What is the staging criteria used to identify secondary sexual characteristics? What does it show?
Tanner stage
It is used to identify if individuals are outliers in their puberty development
When does the growth spurt for males and females occur? How does this create differences between sexes?
Females: ~11, Males: ~14
Means that males have a slightly longer period of time for growth as after their growth spurt their bones fuse so males are generally taller
What causes bone grown to stop?
Epiphyseal closure by oestrogen
What is menarche?
The first menstrual bleed (for females obviously…)
Does ovulation and menarche begin at the same time? Why?
No because the positive feedback mechanism of oestrogen are not developed by menarche
From what age is motile sperm produced? How is this indicated?
At ~13 when motile sperm (i.e. cells capable of moving) in the urine
What is required for females to undergo menarche? Why?
They must reach a critical weight (~47kg) in order for the hypothalamus - pituitary - adrenal axis to activate
It is when the female body is large enough to carry a baby
What is the onset of puberty marked by?
Pulses of LH secretion triggers by GnRH pulses
How do the GnRH pulses change during puberty into adulthood?
The pulses increase in frequency until the adult pattern is establihsed
What causes menopause?
It is when the ovaries run out of follicles
What are the phases of menopause? Explain them and their approximate ages of occurring
Pre-menopause: From ~40 when the menstrual cycle is normal
Menopausal transition: ~46 when the menstrual cycles start to become less regular and a single cycle will last longer due to a longer period of time needed to get a health follicle for ovulation
Post-menopause: ~50 is when menopause (the last menstruation) has occurred and the female is no longer fertile
How does the function of the ovary change during menopause?
From ~46 when irregular menopause begins is called peri-menopause and is when the ovary is beginning to stop functioning normally
A couple of years after menopause, peri-menopause finishes and ovarian senescence occurs which is when the ovary stops producing any significant hormones
After ovarian senescence, what major hormone is no longer produced there?
Oestrogen (it is actually reduced to less than 10% of production FYI but pretty insignificant amount)
How does the female produce oestrogen after ovarian senescence?
Oestrone (a weak version of oestrogen) is produced from the stromal cells of adipose tissue
What are the symptoms of premenopausal symptoms?
Loss of vasomotor control (i.e. hot flushes, nigh sweats), genitourinary symptoms (vaginal dryness), decrease in bone metabolism (osteoporosis) and behavioural changes (depression, tension , anxiety, mental confusion and decreased libido)
What is the main reason for most of the symptoms of peri-menopause?
Rapid deprivation of oestrogen
