Reproductive System and Physiology Flashcards
What is the basis of the hypothalamic pituitary gonadal axis?
Hypothalamus releases GnRH
GnRH stimulates anterior pituitary to produce luteinising hormone (LH) and follicle stimulating hormone (FSH)
LH and FSH stimulate development of follicles in ovaries.
Theca granulosa cells around follicles - oestrogen.
Oestrogen has negative feedback effect on hypothalamus and anterior pituitary - suppresses GnRH, LH and FSH.
What is oestrogen and where does it act?
Steroid sex hormone
Produced by ovaries in response to LH and FSH
Acts on tissues with oestrogen receptors to promote female secondary sexual characteristics
Breast tissue development
Growth and development of female sex organs
Blood vessel development in the uterus
Development of endometrium
What is progesterone and where does it act?
Steroid sex hormone
Produced by corpus luteum after ovulation
Taken over by placenta from 10 weeks if pregnant
Acts on tissues previously stimulated by oestrogen
Thicken and maintain the endometrium
Thickens cervical mucus
Increases body temperature
When do girls tend to start puberty?
8-14
When do boys tend to start puberty?
9-15
Why do overweight children start puberty earlier?
Aromatase enzyme found in adipose tissue
More adipose tissue present, higher quantity of aromatase responsible for oestrogen creation
What is the tanner scale for females?
Stage I - under 10
No pubic hair, no breast development
Stage II - 10-11
Light and thin, breast buds behind areola
Stage III - 11-13
Course and curly
Breasts begin to elevate beyond areola
Stage IV - 13-14
Adult like, not reaching thigh
Areolar mounds form, project from surrounding breast
Stage V - above 14
Hair extends to medial thigh
Areolar mounds reduce, and adult breasts form
What is the tanner scale for males?
Tanner I
testicular volume less than 1.5 ml; small penis (prepubertal; typically age 9 and younger)
Tanner II
testicular volume between 1.6 and 6 ml; skin on scrotum thins, reddens and enlarges; penis length unchanged (9–11)
Tanner III
testicular volume between 6 and 12 ml; scrotum enlarges further; penis begins to lengthen (11–12.5)
Tanner IV
testicular volume between 12 and 20 ml; scrotum enlarges further and darkens; penis increases in length (12.5–14)
Tanner V
testicular volume greater than 20 ml; adult scrotum and penis (14+)
Same pubic hair scale applies
When are the two phases of the menstrual cycle?
Follicular phase from start of menstruation to ovulation Days 1-14 in a 28 day cycle
Luteal phase from ovulation to start of menstruation
Final 14 days of the cycle
What are follicles?
Ovaries have a finite number of cells - oocytes
Granulosa cells surround the oocytes forming follicles.
What are the four key stages of the development of follicles?
Primordial follicles
Primary follicles
Secondary follicles
Antral follicles - Graafian follicles
When does primordial follicle maturation occur?
Occurs independent of the menstrual cycle
Mature into primary and secondary follicles
What occurs during the follicular phase?
FSH stimulates further development of secondary follicle
Secondary follicles have FSH receptors
Follicles grow and granulosa cells surrounding them release oestradiol
Oestradiol has negative feedback on pituitary
Amount of FSH and LH reduces
Rise in oestrogen allows cervical mucus to be permeable for sperm to penetrate cervix at ovulation
One follicle becomes dominant
LH spikes just before ovulation
Causes dominant follicle to release ovum (unfertilised egg) approx 14 days before end of cycle
What occurs during the luteal phase?
Follicle that released the ovum collapses
Becomes the corpus luteum
Corpus luteum secretes progesterone maintaining endometrial lining
Progesterone causes cervical mucus to become thick and no longer penetrable
Corpus luteum also secretes small amount of oestrogen
If fertilisation - syncytiotrophoblast secretes HCG
HCG maintains corpus luteums
No fertilisation - no HCG, corpus luteum degenerates
Fall in oestrogen and progesterone causes endometrium to break down - menstruation
Stromal cells of endometrium release prostaglandins
Negative feedback from oestrogen and progesterone on hypothalamus and pituitary ceases, LH and FSH rise.
What are the levels of hormones during the cycle?
FSH maintains constant level, but peaks at Day 14
LH massive spike at Day 14
Oestrogen rises over the follicular phase then dramatically falls after Day 14
Progesterone rises during the luteal phase
Describe the journey of the zygote from fertilisation until a urinary pregnancy test becomes
positive.
23 chromosomes from the egg and 23 chromosomes from the sperm combine to form a fertilised egg called a zygote.
This then divides rapidly to form a morula. This mass of cells travels along the Fallopian tube towards the uterus.
Whilst travelling, a fluid filled cavity gathers within the group of cells and becomes a blastocyst, contains the embryoblast.
Alongside embryo blast is fluid filled cavity called blastocele. Surrounding this is the trophoblast.
Blastocyst arrives at the uterus 8-10 days after ovulation, and reaches endometrium.
Outer layer of the trophoblast known as the sycytiotrophoblast extends into the storm and mixes with the endometrium.
The cells of the storm convert into the decidua and provides nutrients to the trophoblast. The syncytiotrophoblast starts producing hCG which causes a positive pregnancy test.
What is the placenta formed from?
Trophoblast
What happens to the placenta at day 6 of gestation?
Trophoblast interact with endometrial decidual epithelia –> invasion into maternal uterine cells
Invasion is interstitial and on the anterior and posterior walls of the body of the uterus
What happens to the placenta at day 8 of gestation?
Differentiation into syncitiotrophoblast and cytotrophoblast
Syncitiotrophoblast send out projections to erode maternal tissue and produce HCG
What happens to the placenta at day 9 gestation?
Lacunae form within syncitiotrophoblast and maternal blood enter from spiral arteries
Cytotophoblast begin to form villi
What are the types of villi in the placenta?
Primary - projections of trophoblast
Secondary - invasion of a mesenchyme core
Tertiary - invasion of fetal vessels
What happens to the maternal circulation in the formation of the placenta?
Spiral arteries remodel forming low resistance, high flow circulation
Cytotrophoblast invade the spiral arteries and replace maternal endothelium - 1 less barrier
What are the key blood vessels in the fetus?
Umbilical vein - carry oxygenated blood
Umbilical artery - carry deoxygenated blood
How do nutrients exchange at the placenta?
Maternal O2 and nutrients exchange at terminal villi into intervillous space
What surrounds the fetal surface?
Chorionic membrane:
- amnion
- umbilical vessels
What is the decidua?
Name given to the endometrium which is modified by progesterone in preparation for pregnancy
What forms the placental barrier in the first trimester?
Syncitiotrophoblast resting on cytotrophoblast
Relatively thick
What is the placental barrier like in the third trimester?
Thin - cytotrophoblast lost
Huge SA
What happens to the placenta around month 4-5?
Decidua form septal which project into intervillous lacunae
Has core maternal tissue and covered by syncitial cells
Septa divide placenta into cotyledons
What is the function of HCG and what secretes it?
Maintain corpus luteum until placenta can secrete the pregnancy hormones
Secreted by syncitiotrophoblast
What causes most maternal adaptations in pregnancy?
Progesterone
Oestrogen has some effect
What changes are seen in pregnancy?
GI
Haematological
MSK Renal Biochemical Respiratory Nutrient CVS
What GI changes are seen in pregnancy?
Visceral displacement - appendicitis present as RUQ pain
SM relaxation - heartburn + gall stones
Reduced GI motility - constipation
What haematological changes are seen in pregnancy?
Plasma volume increase - dilution anaemia
Raised fibrinogen and clotting factors and decreased fibrinolysis - Pro-thrombotic state
Immunosuppression - risk of infection
What MSK changes are seen in pregnancy?
Ligament laxity - Pubic symphysis dysfunction
Back pain
What renal changes are seen in pregnancy?
Renal plasma flow and GFR increase - increased creatinine and clearance
SM relax - stasis = UTI
Large uterus - Risk of obstruction
Bicarb excretion (compensate for hyperventilation) - low bicarb reserve so acidosis risk
What biochemical changes are seen in pregnancy?
Calcium req. increase - Increased renal excretion (stones) and more GI absorption
TBG increase - free T3/4 = same but overall T3/4 increase for fetal neural development
What respiratory changes occur in pregnancy?
Diaphragm displaced up - AP and transverse diameter increase to compensate
Increased CO2 from fetus and increased respiratory drive - hyperventilation
What nutrient changes are seen in pregnancy?
Raised lactogen, prolactin and cortisol - increased insulin resistance so maternal FA and glucose saved for fetus
Lipolysis to increase FA as metabolic substrate - risk of ketoacidosis
What CVS changes occur in pregnancy?
Increased blood volume
Increased CO, SV. HR
Peripheral resistance and BP drop in 1st and 2nd trimester
IVC compressed if flat on back
How is dyspepsia due to pregnancy managed?
Sleep propped up
Small frequent meals
Decrease spice, fruit, caffeine
Most antacids can be used
How is constipation due to pregnancy managed?
Increase fluid intake
High fibre food
Plenty of exercise
Laxatives
How is fatigue and insomnia due to pregnancy managed?
Rest and reassure
Avoid sleeping tablets
Peak in first trimester
Explain what must be considered when a pregnant lady has pruritus
Look for rash
Exclude obstetric cholestasis - check LFT’s
Common in last 12 weeks
How is back pain due to pregnancy managed?
Light exercise
Simple analgesia
Physio referral
What happens in pubic symphysis dysfunction?
Pain in suprapubic and lower back area which radiates to thigh and perineum
How is pubic symphysis dysfunction managed?
Education
Physiotherapy
Belts
Crutches
Why do pregnant women get carpel tunnel syndrome and how is it managed?
Fluid retention compresses nerve
Wrist splints and steroid injections
What changes are seen in blood results in pregnancy?
Raised - WCC, ALP, TSH (in 3rd trimester)
Lowered - Hb, Na+, K+, Urea, Creatinine, Ca2+, Albumin, Bilirubin, TSH (1st trimester)
When is the uterus usually palpable in the abdomen?
12 weeks
What could cause a large for date uterus?
Molar pregnancy
Multiple pregnancy
Polyhydramnios
Fibroids and Cysts
When does the uterus normally reach the umbilicus?
20 weeks
How long does labour usually last?
8 hours in first pregnancy
5 hours in subsequent pregnancies
What happens to the myometrium in labour?
Pacemaker smooth muscle cells generate AP’s which spread across specialised gap junction –> co-ordinated contractions
What movements does the baby do when being delivered?
Head flex
Head internally rotate
Head delivered
Head extend
Head externally rotate
Shoulders rotate and deliver
What happens to the breasts during pregnancy?
Alveolar cells differentiate to be able to produce milk from mid gestation
Areolar enlarge and darken
Montgomery tubercles produce sebum and pheromones
What is the purpose of sebum and pheromones?
Sebum - prevent cracking
Pheromones - Baby locate nipple
Why is there little milk secretion in pregnancy?
High progesterone:oestrogen ratio
What is the composition of breast milk?
Water - 88.1%
Fat - 3.8%
Protein - 0.9%
Lactose - 7%
Other - 0.2%
What is colostrum?
First secretion from mammary glands
Low in water, fat and sugar
High in protein, IgA,M,G and white cells
How much colostrum is produced?
40ml/day for first 3 days
What are the benefits to breastfeeding?
Baby gets less infections
Bonding - oxytocin
Reduced risk ovarian and breast cancer
Further contract uterus
Weight loss
How does milk production start post delivery?
Delivery of placenta remove large amount of progesterone
Alveoli respond to Prolactin and produce milk within 24-48hrs
How is prolactin stimulated?
Suckling
Mechanical stimulation of receptors in nipple inhibit dopamine secretion in hypothalamus. Dopamine inhibit prolactin. Suckling also increase vasoactive intestinal protein which promotes prolactin.
Why is some milk made in the first 24-48 hours?
Prolactin produced by decimal cells which aren’t inhibited by dopamine
How is milk production regulated?
Suckling at one feed promote prolactin release which produces milk ready for next feed - it is a demand based production
Describe the milk let down reflex
Oxytocin released from posterior pituitary in response to suckling
Myoepithelial cells stimulated and contract squeezing milk out of breast (Milk is ejected not sucked out)
What can stimulate/inhibit oxytocin release?
Stimulate - Cry, sight of infant, fondling, anticipation
Inhibited - Pain, embarrassment, alcohol
How does milk production stop?
If suckling stop, milk production gradually ceases
This can be due to:
Turgor induced damage to secretory cells
Low prolactin levels
What drugs should be avoided while breastfeeding?
Antibiotics - cipro, tetracycline, chloramphenicol, sulphonamides
Lithium and Benzo’s
Aspirin Carbimazole Methotrexate Sulfonylureas Cytotoxics Amiodarone Clozapine
