Physiology Flashcards
What are the main functions of the vulva
Sensory tissue during intercourse
Assist in micturition (direct flow of urine)
Protect internal reproductive tract from infection
What are the main roles of the vagina
Transport of ejaculate to uterus
Channel of delivery in childbirth
Channel for outflow of menstrual fluid
What are the 5 main ligaments of the ovaries
Broad ligament
Round ligament
Ovarian ligament
Cardinal ligament
Uterosacral ligament
What are the 3 sections of the fallopian tubes
Infundibulum
Ampulla
Isthmus
What is the indifferent stage of gonad development
Not able to distinguish between male and female gonads
Begin as genital ridges
In 4th week, germ cells migrate from yolk sac to genital ridges
Epithelium of genital ridges and intermediate mesoderm form primitive sex cords
How do the testes develop
SRY gene on Y chromosome stimulates development of testes
Cords become seminiferous tubules during puberty
Leydig cells start producing testosterone in 8th week
How do the ovaries develop
Without SRY gene, primitive sex cord degenerates
Epithelium of gonad proliferates, producing cortical cords
How do the male internal genitalia develop
Testosterone causes mesonephric duct to develop into primary male genital duct
Paramesonephric duct degenerates due to presence of anti-Mullerian hormone
How do the female internal genitalia develop
Lack of testosterone causes mesonephric ducts to degenerate
Paramesonephric ducts develop due to lack of anti-Mullerian hormone
What is coitus
Sexual intercourse that results in the deposition of sperm at the vagina, at the level of the cervix
What are the main phases of the sex response
Sexual arousal
Excitement
Plateau
Orgasmic
Resolution
Explain the excitement phase of the sexual response in males
Sacral parasympathetic neurones
Vasodilation in corpora cavernosa
Increased penile blood flow
Penile filling = latency, penile tumescence = erection
Explain the plateau phase of the sexual response in males
Sacrospinous reflex
Venous engorgement and decreased arterial inflow
Testes become engorged and elevated
Secretions from accessory glands (5% of ejaculate)
Lubrication of distal urethra
Explain the orgasmic phase of the sexual response in males
Emission
- Thoracolumbar sympathetic reflex
- Contraction of smooth muscles and urethral sphincters
- Semen pools in urethral bulb
Ejaculation
- Spinal reflex with cortical control
- Contraction of glands, ducts, and sphincters
- Filling of internal urethra (stimulation of pudendal nerve, contraction of genital organs, expulsion of semen)
Explain the resolution phase of the sexual response in males
Thoracolumbar sympathetic pathway
Contraction of arterial smooth muscle in corpora cavernosa
Increased venous return
Detumescence and flaccidity
Explain the excitement phase of the sexual response in females
Sacral parasympathetic neurons
Vasocongestion
Vaginal lubrication
Clitoris engorges with blood
Uterus elevates
Increased muscle tone, heart rate, blood pressure
Inner 2/3 of vagina lengthens and expands
Explain the plateau phase of the sexual response in females
Sacrospinous reflex
Further increased muscle tone, heart rate, blood pressure
Clitoris withdraws under hood
Bartholin gland secretions lubricate vestibule
Uterus fully elevates
Orgasmic platform in lower 1/3 vagina
Explain the orgasmic phase of the sexual response in females
Spinal reflex with cortical control
Orgasmic platform contracts 3-15 times
Uterus contracts
Anal sphincter contracts
Explain the resolution phase of the sexual response in females
Thoracolumbar sympathetic pathway
Clitoris and labia return to normal
Uterus descends
Vagina shortens and narrows back to unaroused size
No refractory period
What factors are involved in the transport of sperm
Oxytocin (causes uterine contractions, helps sperm travel further)
Capacitation (tail changes from beat-like to whip-like movements)
Removal of protein coat (exposing sperm acrosome enzymes, needed for penetrating zona pellucida)
What happens once sperm has penetrated the zona pellucida
Sperm and oocyte membranes fuse
Calcium enters oocyte (cell depolarises, prevents polyspermy, egg undergoes final meiotic division)
What are the endocrine system maternal adaptations
Increased progesterone (by corpus luteum, then placenta)
Increased oestrogen (by placenta)
Increased thyroid-binding globulin (due to high oestrogen)
Increased human placental lactogen, prolactin, and cortisol (all anti-insulin, so get reduced peripheral glucose uptake)
Increased lipolysis (risk of ketoacidosis)
What are the cardiovascular system maternal adaptations
Decreased diastolic blood pressure (due to increased progesterone (decreased systemic vascular resistance))
Increased cardiac output (by 30-50%)
Increased sodium and water retention
What are the respiratory system maternal adaptations
Upward displacement of diaphragm
Increased tidal volume
Increased minute ventilation rate
Some may get hyperventilation
What are the gastrointestinal system maternal adaptations
Upward displacement of stomack (increased intra-gastric pressure - reflux, nausea, vomiting)
Appendix in right upper quadrant
Smooth muscle relaxation (progesterone) - constipation, gallstones
What are the urinary system maternal adaptations
Increased eGFR (50-60%)
Relaxation of ureters and bladder (progesterone) - more UTIs and pyelonephritis
What are the haematology system maternal adaptations
Increased fibrinogen and clotting factors
Increased VTE risk (use LMWH)
Dilutional anaemia
How do the breasts develop during pregnancy
Hypertrophy of ductular-lobular-alveolar system
- Prominent lobules form, differentiate to form milk
Not a lot of milk secretion (still have high progesterone:oestrogen)
What is colostrum
Breast milk following delivery
More proteins (antibodies) and fat-soluble vitamins
Less fats, sugars, and water-soluble vitamins
How is milk production regulated
Controlled by prolactin
Alveoli respond to prolactin after delivery of placenta
Prolactin release from anterior pituitary controlled by dopamine
Promoted by suckling (releases dopamine)
Suckling at one feed prepares milk for next feed
Explain the milk let-down reflex
Oxytocin released in response to suckling
Causes myoepithelial cells to contract, squeezing milk out of breast
Can be triggered by cry/sight/preparation for nursing
How is milk production maintained
Need enough suckling stimulation at each feed to maintain prolactin secretion
Can get milk suppression with steroids
Prolactin from suckling reduces fertility
What is puberty
Developmental changes that a child undergoes to become sexually mature and physiologically ready for reproduction
Female: 8-14
Male: 10-16
What are the hormonal changes in puberty
Controlled by HPG axis
Hypothalamus releases pulsatile GnRH
Anterior pituitary releases FSH and LH
What effect does FSH have on the gonads
Oestrogen synthesis and oogenesis
Onset of sperm production
What effect does LH have on the gonads
Increased progesterone
Increased testosterone
What are the female physical changes in puberty
Thelarche
- Breast buds at 9-10
- Continue to develop after menarche
Pubarche
- Mediated by testosterone
Menarche
- 1st period 1.5-3 years after thelarche
- Due to FSH and LH
- Average age 12.8
What are the male physical changes in puberty
Genital changes
- Increased testicular size
- Scrotal skin thinner, darker, hangs down
- 1st ejaculation possible 1 year after testes begin to grow
- Growth of penis (length, then girth)
Pubarche
- Initially at base of penis
- On rest of the body 2 years after pubarche
What causes growth spurts in puberty
Interaction between
- Sex steroid hormones
- Growth hormones
- Insulin-like growth factor
Voice breaks in males (larynx and vocal cords enlarge)
What are the phases of the ovarian cycle
Follicular phase
Ovulation
Luteal phase
What happens during the follicular phase of the ovarian cycle
Follicles mature
Low steroid hormones and inhibin
Less negative feedback on HPG axis
Increased FSH and LH
Follicular growth and oestrogen production
Negative feedback reduces FSH
One follicle survives
Follicular oestrogen causes positive feedback on HPG axis
Increased GnRH and gonadotropins
Get LH surge
What happens during the ovulation phase of the ovarian cycle
Mature oocyte released in response to LH surge
Follicle releases oestrogen and progesterone
Get negative feedback on HPG axis
Cycle stalls in preparation of fertilisation
What happens during the luteal phase of the ovarian cycle
Corpus luteum releases oestrogen, progesterone, and inhibin
Corpus luteum regresses after 14 days
Significant fall in hormones
Less negative feedback on HPG axis
If fertilisation occurs, corpus luteum maintains HCG levels
At 4 months, placenta able to produce enough hormones
What happens during the proliferative phase of the uterine cycle
Alongside follicular phase
Oestrogen causes:
- Fallopian tube formation
- Endometrial thickening
- Increased growth and motility of myometrium
- Thin cervical mucus production
What happens during the secretory phase of the uterine cycle
Alongside luteal phase
Progesterone causes:
- Endometrial thickening
- Myometrium thickening
- Thick cervical mucus
- Changes in mammary tissue
- Metabolic changes
What happens during the menses phase of the uterine cycle
Absence of fertilisation
Corpus luteum breaks down
Inner lining of uterus shed
Lats 2-7 days
10-80ml blood loss
What is the average age of menopause in the UK
51 years
Early menopause 40-45 years
What are the main symptoms of menopause
Hot flushes
Urinary incontinence
Increased UTIs
Irregular vaginal bleeding
At what point is menopause diagnosed
Amenorrhoea for 12 months
What are the hormonal changes associated with menopause
Reduced circulating oestrogen
- Due to reduced sensitivity of ovaries to FSH and LH
Significant increase in FSH and LH
What are the vasomotor changes associated with menopause
Hot flushes
Due to pulsatile LH release
What are the urogenital changes associated with menopause
Atrophy of vagina
Thinning of myometrium
Thinning and dryness of vaginal walls
Bladder and urethra atrophy
What happens to bone density after menopause
Increased bone reabsorption (decreased oestrogen)
Increased risk of fractures
What happens to the rates of heart disease after menopause
Increase
Protection from oestrogen now gone
