Male Infertility - Science Flashcards
How is the chromosomal sex of a male established?
An ovum with an X chromosome is fertilised by a sperm with a Y chromosome to form an embryo with XY chromosomes
What does a Y chromosome have that an X chromosome does not?
Sex determining region
What is the role of the sex determining region of the Y chromosome?
To stimulate the bipotential gonad to differentiate into testes
What is male gonadal sex?
The presence of testes
What two hormones are secreted by the foetal testes?
Testosterone and Mullerian inhibiting factor
What is the role of testosterone secreted by the foetal testes?
Causes undifferentiated external genitalia to develop along male lines i.e. penis and scrotum, and it transforms the Wolffian duct into the male reproductive tract
What is the role of Mullerian inhibiting factor secreted by the foetal testes?
Degeneration of the Mullerian ducts
What is male genital sex?
The presence of male external genitalia
At what point in development do external genitalia start to differentiate? When can the sex be determined on a scan?
9 weeks / 16 weeks
In the development of a male embryo, without the stimulus of male testicular hormones, what would happen?
The foetus would develop a female internal genital tract
What happens to the Wolffian and Mullerian ducts in the development of a female embryo?
The Wolffian duct degenerates and the Mullerian duct goes on to become the female reproductive tract
In terms of embryonic development, what happens in androgen insensitivity syndrome?
Insensitivity to androgens means that the androgen induction of the Wolffian duct does not occur, but Mullerian duct inhibition does occur
What would be the karyotype (chromosomal sex) of an individual with androgen insensitivity syndrome?
XY
What would be the gonadal sex of an individual with androgen insensitivity syndrome?
They would have developed testes but they would not have descended
What would be the genital sex of an individual with androgen insensitivity syndrome?
Phenotypically female external genitalia, but with no uterus/ovaries and a short vagina
Individuals with androgen insensitivity syndrome are usually brought up as what gender?
Female
How may individuals with androgen insensitivity syndrome present?
At puberty, with a lack of pubic hair and primary amenorrhoea
Individuals with diagnosed androgen insensitivity syndrome usually continue life as what gender?
Female
How are individuals with androgen insensitivity syndrome treated?
HRT, removal of the undescended testes, and fertility treatment (surrogacy, egg donation) if they want to conceive
How is androgen insensitivity syndrome inherited?
X-linked autosomal recessive
In utero, where do the testes develop?
In the abdominal cavity of a foetus
Where do the testes end up before birth? What is this dependent on?
In the scrotal sac, which is dependent on androgen
Why is it important that the testes descend?
Because it is a lower temperature outside the body which is needed to facilitate spermatogenesis
Outside the body, what structure is responsible for temperature control of the testes?
Dartos muscle
What are the two functions of the testes?
Spermatogenesis and the production of testosterone
What structures are responsible for spermatogenesis?
Seminiferous tubules
What cells of the testes are responsible for the production of testosterone?
Leydig cells
What is cryptorchidism?
The individual has reached adulthood and the testes have not descended
What is the advantage of unilateral cryptorchidism?
It maintains fertility
Why is it cryptorchidism dangerous?
Increases the risk of testicular germ cell cancer
What is the treatment of cryptorchidism if the individual is < 14 years of age?
Orchidoplexy (descending the testes)
What is the treatment of cryptorchidism if the individual is an adult?
Orchidectomy
How often are LH and FSH secreted in males?
They are secreted constantly
When does GnRH start to be released in males? How often is it released?
GnRH release starts at puberty, and from then is secreted in bursts every 2-3 hours
What is the role of GnRH?
Stimulates the anterior pituitary gland to secrete LH and FSH
GnRH in males is under negative feedback control by what hormone?
Testosterone
LH acts on which cells in males?
Leydig cells
What is the role of the Leydig cells once LH has acted on them?
Regulate testosterone secretion
FSH acts on which cells in males?
Sertoli cells
What is the role of the Sertoli cells once FSH has acted on them?
Enhances spermatogenesis
FSH is under negative feedback control by what hormone(s)?
Testosterone and inhibin
Where is inhibin secreted from?
Sertoli cells
LH is under negative feedback control by what hormone(s)?
Testosterone
What type of hormone is testosterone?
Steroid hormone
Where is testosterone produced?
Leydig cells
Where is testosterone secreted into from the Legdig cells?
The blood and seminiferous tubules
Testosterone exerts negative feedback on where?
The hypothalamus (GnRH) and anterior pituitary (LH and FSH)
What is the role of testosterone at puberty?
Promotion of puberty and development of secondary male characteristics
What are the roles of testosterone in an adult?
Controls spermatogenesis, secondary sex characteristics, libido and erection, and may have a role in aggressive behaviour
What type of hormones are inhibin and activin?
Peptide hormones
Inhibin and activin are secreted by which cells?
Sertoli cells
Inhibin and activin exert feedback on which hormone?
FSH
After ejaculation, a series of biochemical and electrical events take place before fertilisation. Where does this occur?
Ampulla of the fallopian tube
What are the roles of the epididymis and vas deferens?
Exit route from testes to urethra, concentrates and stores sperm, site of sperm maturation
What 4 things are secreted by the seminal vesicles?
Seminal fluid, fructose, prostaglandins and fibrinogen
What are the roles of the prostate gland?
Produces alkaline fluid to neutralise the vagina and produces clotting enzymes to clot semen within a female
What is the role of the bulbourethral gland?
Secretes mucus to act as a lubricant
Describe the structures the sperm would pass through from testes to urethra?
Testes, epididymis, vas deferens, ejaculatory duct, urethra
When a man is erect, which part of the penis fills with blood?
Corpus cavernosa
Erection is under control by which branch of the autonomic nervous system?
Parasympathetic
Ejaculation is under control by which branch of the autonomic nervous system?
Sympathetic
