Reproductive System Flashcards
What happens in the hypothalamus in the reproductive system?
GnRH from the hypothalamus causes the release of follicle stimulating hormone (FSH) and luteinising hormone (LH) from the anterior pituitary
What do FSH and LH do at the gonads?
They act together to effect:
- Gametogenesis: sperm production in the testes and follicle development around ova in the ovary
- Steroidogenesis: hormone production; male - testosterone and inhibin, female - estrogen, progesterone and testosterone
Where does sperm mature?
In the epididymis
Where does sperm production take place?
In seminiferous tubules
What cells does FSH act on in the male reproductive system?
On the sertoli cells which drives the production of inhibin which inhibits the production of FSH from the anterior pituitary gland.
Sertoli cells are also known as support cells for spermatogenesis
What cells does LH act on in the male reproductive system?
On the leydig cells which drives the production of testosterone
What is the seminal fluid?
- Makes sperm motile
- Provide nutrients for sperm motility
- Neutralise acidic environment (urethra and vagina)
What is the prostatic fluid?
- Neutralise acidic environment
- Antibiotic
What is the bulbo-urethral glands?
- Mucus to neutralise acidic environment
- lubrication of penis tip
What are androgens?
Sex hormones that bring on puberty
Is testosterone lipid or water soluble?
Testosterone is a lipid soluble hormone. Which means that it travels bound and drives gene transcription.
What 3 developmental time points elevate testosterone levels?
- During development
- Following birth there is another peak
- Puberty
What is senescence?
Progressive loss of testosterone over time - but despite the loss of testosterone, males can still produce sperm throughout their lifetime
How long does the ovarian cycle go for?
~28 days
How many follicles does a female have?
2 million follicles waiting to mature and thats all you ever have. They die throughout the lifespan (limited number of ova in the female ovary)
What drives the development of follicles into different stages?
Once a female goes through pubertal onset, they develop more layers of cells around the egg.
What are granulosa cells and where are they located?
FSH stimulates granulosa cells which stimulates the growth of follicles.
Granulosa cells are closer to the egg.
Granulosa cells produce inhibin and estrogen
What are theca cells and where are they located?
LH stimulates theca cells which stimulates the production of androgens like production of estrogen.
Theca cells sit around the outside of the egg.
Theca cells produce testosterone
What hormones does the corpus luteum produce?
Produces large amounts of progesterone and estrogen
What happens in the follicular phase of the ovarian cycle?
Day 1-14
Maturation of a primary follicle to secondary follicle due to the influence of FSH. Only one follicle will mature and progress through to ovulation. As the follicle develops, it secretes estrogen, which stimulates the thickening of the uterus lining
What happens during ovulation?
Around day 14
Ovulation is triggered by a spike in LH. The mature follicle ruptures, releasing the follicle into the fallopian tube, ready for fertilisation
What happens in the luteal phase?
Day 15-28
After ovulation, the empty follicle transforms into the corpus luteum, which secretes progesterone and some estrogen. If the oocyte is not fertilised, the corpus luteum degenerates, hormone levels drop and the endometrium lining of the uterus sheds off, causing menstruation. If fertilisation does occur, the ova gets buried in the endometrium.
At what phases is there negative and positive feedback occurring from estrogen?
Follicular phase - negative feedback
Ovulation - positive feedback
Luteal Phase - negative feedback
How does estrogen provide negative and positive feedback?
Estrogen switches from negative to positive feedback at the level of the brain and the pituitary gland. Positive feedback means that instead of inhibiting the release of GnRH, it increases it which causes a huge increase in LH, known as the LH surge, which is critical for ovulation. The follicle then remodels into the corpus luteum which produces progesterone and estrogen and that returns to providing negative feedback to the brain.
What are the functions of estrogen and progesterone?
- They act through intracellular receptors to drive gene transcription in many target tissues
- Important in mood, cognitive function, libido
- Important in bone growth and strength
- Protective in heart, brain and metabolic health
- Can contribute to reproductive tissue cancers
What type of feedback does testosterone provide?
Negative feedback
In the male system, what type of feedback does inhibin provide?
Negative feedback of FSH
How are GnRH and LH secreted?
In discrete pulses ~1/hour. The frequency and amplitude of these pulses change over the menstrual cycle.
What makes the pulses of GnRH and LH slower?
After the LH surge there are lots of estrogen and progesterone produced in the luteal phase which makes our pulses slower because progesterone causes dramatic negative feedback.
What are the 12 stages of hormonal control of the menstrual cycle?
- low estrogen: LH and FSH increase so multiple follicles develop
- estrogen (from follicles) rises
- dominant follicle: secretes estrogen and inhibin
- increased estrogen and inhibin reduce FSH
- estrogen switches to positive feedback
- LH surge
- ovulation
- corpus luteum forms
- corpus luteum secretes estrogen and progesterone
- FSH and LH are inhibited
- corpus luteum degenerates so estrogen and progesterone decrease
- FSH and LH levels rise
What is the difference in feedback for females and males?
Females have both negative and positive feedback
Males have negative feedback only (tonic secretion)
What are barrier methods of contraception?
- condom
- female condom
- diaphragm
- cervical cap
- contraceptive sponge
What are fertility awareness methods of contraception?
- rhythm method
- basal body temperature
- saliva method
What are hormonal methods of contraception?
- oral contraceptives “the pill”
- implants
- depo provera
- post-coital contraception
- spermicides
What are other methods of contraception?
- intrauterine device
- surgery (vasectomy, tubal ligation, hysterectomy)
- abstinence
How does the oral contraceptive pill work?
The pill contains either estrogen and progesterone or progesterone only. This provides negative feedback to the hypothalamus and the pituitary gland to reduce GnRH and LH/FSH release. It maintains high levels of estrogen and progesterone which limits follicle maturation and avoids the LH surge. The hormones also thicken cervical mucus to restrict the movement of sperm.
What are androgenic anabolic steroids?
They mimic testosterone negative feedback in the brain and anterior pituitary gland
What do androgenic anabolic steroids do at the seminiferous tubules in testes?
- More testosterone is being pharmacologically made which inhibits the gonadotrophins and GnRH which drives the reduction of sperm made at the testes
- testicular atrophy
- infertility
- higher risk of cancers
What do androgenic anabolic steroids do at the follicles in the ovary?
- provides too much negative feedback
- high pharmacological levels of testosterone reduces the production of natural estrogen, inhibin and testosterone
- impaired menstrual cycle
- infertility
- higher risk of cancers
What is polycystic ovary syndrome (PCOS)?
- most common cause of infertility associated with ovarian failure
- associated with a metabolic syndrome, depression and endometrial cancer
- diagnostic criteria: 2 or 3 symptoms
What happens in polycystic ovary syndrome?
- The negative feedback is impaired so the brain is unable to sense the signal coming from the ovary, so it sends out more hormone
- PCOS causes more LH secreted in the high pulsatile manner which drives testosterone and androgen production
What is eumenorrhea?
A normal, healthy menstrual period
What is amenorrhea?
The absence of menstrual periods
What are the pros of cycle syncing?
- Aims to promote the most beneficial exercise at different cycle stages
- Acknowledges sex differences and menstruation and the impact of estrogen and progesterone on several body systems
What are the cons of cycle syncing?
- Based on a very limited amount of data, mostly from elite female athletes
- Reductionist: suggests sex hormones are the most influential force on exercise motivation and ability
What is the female athlete triad?
- leads to infertility and poor health outcomes
- absent or infrequent menstrual periods
- low caloric intake/ high use of caloric intake (low energy)
- low bone mineral density
- its common in endurance athletes or those with low body weight
- signals of stress and reduced metabolic reserves inhibit GnRH secretion from the hypothalamus
What happens from puberty to menopause?
- the reproductive axis is initiated 3 times: prior to birth, shortly after birth and puberty
- puberty begins with increased night time GnRH/LH/FSH release, characterised by growth and secondary sex characteristics
- the reproductive axis is silent during childhood, prior to puberty onset
- menopause signals the end of the female reproductive life span and is characterised by a loss of gonadal steroid hormones and feedback
(testosterone falls gradually from midlife while estrogen falls more dramatically with menopause)
What is android body composition?
- “Apple shape” (above the waist)
- Typically males (XY) - testosterone dominated
- increased skeletal muscle mass
- decreased total adipose tissue
- increased visceral adipose tissue
- decreased subcutaneous adipose
What is gynoid body composition?
- “pear shape” (below the waist)
- typically females (XX) - estradiol dominated
- decreased skeletal muscle mass
- increased total adipose tissue
- decreased visceral adipose tissue
- increased subcutaneous adipose
What effect does testosterone have on the cardiovascular system?
increases red blood cell number which increases the oxygen carrying capacity of blood
What effect does estrogen have on the cardiovascular system?
protects against fatty deposits in arteries which reduces the risk of blocked arteries
How does menopause change the body composition?
- increases GnRH/LH/FSH production
- decreases estrogen, progesterone and testosterone
- increased fat mass and decreased lean muscle mass
- switch from pear to apple body composition
- estrogens are highly protective during reproductive life and when they fall it causes health risks
How does sex differences affect athletic performance?
Pre-puberty
- similar athletic performance in males and females
Post-puberty
- sex differences in performance driven by testosterone
- sport dependent
What is sexual intercourse in reproductive terms?
delivery of sperm into the vagina
What happens in the arousal phase of sexual intercourse?
Male:
- penile arteries dilate
- erection
Female:
- dilation of arteries
- increased BP
- lubrication
Parasympathetic nerve activity
What happens in the orgasm phase of sexual intercourse?
Male:
- contractions of vas deferens
- ejaculation of semen
Female:
- rhythmic contractions of vaginal and uterine muscles
Sympathetic nerve activity
What is the path of sperm from intercourse to conception?
Stored in the epididymis –> vas deferens –> ejaculatory duct –> urethra –> into the uterus and then somewhere in the fallopian tube
What is the path of the egg/ovum from intercourse to conception?
From the ovary –> fallopian tube –> uterus
Where does fertilisation occur?
It takes several days for the egg to reach the uterus so most commonly, fertilisation happens somewhere along the fallopian tube
What is the human chorionic gonadotrophin hormone?
- its known as the pregnancy hormone
- signal from dividing fertilised egg that maintains the corpus luteum in the ovary for ~3 months
During pregnancy, where does estrogen and progesterone come from?
- comes from the corpus luteum (first 3 months) and then the placenta
What does prolactin do in regards to lactation?
- its secreted from the anterior pituitary
- prolactin is normally inhibited by dopamine coming from the hypothalamus, so when dopamine secretion decreases, prolactin can be secreted
- when secreted, prolactin promotes milk production in the breast - milk synthesis
What does oxytocin do in regards to lactation?
- its secreted from the posterior pituitary
- Oxytocin promotes milk ejection from the breast
- Its important for the ‘milk ejection reflex’ which is the contraction of smooth muscles around milk ducts which causes milk to be ejected from the nipple
What are prolactin and oxytocin controlled by?
Both are controlled by sensory neurons responding to the suckling stimulus
