Block 11 Flashcards
What percentage of sperm makes it to the cervix?
1%
Where does fertilisation occur most frequently?
Ampullary region of uterine tube
What steps must occur before the oocyte can be fertilised?
Capacitation
Acrosome reaction
What is Capacitation?
Lasts 7 hours
Destabilising of sperm head by removal of cholesterol
Acrosomal membrane removed
Sperm plasma membrane hyper polarisation
Influx of HCO3, increased Camp, influx Ca and decrease pH
Hyperactive motility
What are the 3 phases of fertilisation?
Penetration of corona radiata
Penetration of zona pellucida
Fusion of oocyte and sperm cell membrane
During one ejaculation, how many sperm are released?
300 000 000
What is the function of ZP3 in fertilisation?
Causes the release of acrosomal enzymes like acrosin
Allows the sperm to penetrate the zona pellucida
Allows contact with oocyte membrane
What is the Acrosome reaction?
When the sperm contacts the oocyte membrane the permeability of the zona pellucida changes
Lysosomal enzymes are released from cortical granules that line the plasma membrane of oocyte
Zona reaction
Prevents sperm penetration and Inactivates receptors on surface
What is the second polar body?
It is one of the daughter cells produces when the oocyte finishes its 2nd meitotic division, it receives hardly any cytoplasm
What is the morula and when does it form?
3 days
16 cells in the same space as the initial zygote
What is a blastocyst?
It is the next stage after the morula and it forms a cavity to allow for nutrition to get to all cells - blastocyst cavity.
inner cell mass and outer cell mass
What is the bilaminar disc?
It is the stage after the blastocyst. It is when the inner cell mass subdivide into the epiblast and the hypoblast.
The cells continue to divide and as a result the epiblast cells need a cavity for nutrition (amniotic cavity). Initial cavity = primitive yolk sac
When does gastrulation occur? What is it?
day 12
Primitive node, primitive pit and primitive streak form in epiblast.
Cells in the primitive streak multiply and fold under the epiblast to form new layers.
What happens during week 1 of embryogenesis?
Division of cells to form a blastocyst cavity. Formation of hypoblast, epiblast and trophoblast
What happens during week 2 of embryogenesis?
Implantation and development of the primary yolk sac
Formation of the primitive streak and node
What happens during week 3 of embryogenesis?
Head and tail folding Neuralation Fore-mid-hind gut Germ cells in allantois wall Primitive vascular system - heart tube
What happens during week 4 of embryogenesis?
Pharyngeal arches trachea and lung buds thyroid and liver urorectal septum mesonephrus, mesonephric duct and uteric bud indifferent gonads septum primum forms forelimb bud
What happens during week 5 of embryogenesis?
Optic cup and vesicle primary bronchi pharygeal pouches pancreas mullerian ducts septation of ventricles spleen
What happens during week 6 of embryogenesis?
upper lip and palate anterior lobe of pituitary rotation of stomach major calyces testis differentiating external genitalia indifferent forelimb digit rays hindlimb bud
What happens during week 7 of embryogenesis?
posterior lobe of pituitary membranous labyrinth brochi division midgut loop rotating metanephric nephrons and minor calyces septum secondum cartilaginous part of skull
When does an embyro become a foetus?
8 weeks
What happens during week 8 of embryogenesis?
digits on hand
external ear
membranous part of skull
What components of the female reproductive system aid fertilsation?
Fluid current in tube from epithelial secretion
cilia beating towards uterus
weak contractions of fallopian tube
When does implantation occur?
1-3 days after fertilisation
Before implantation, where does the embryo get its nutrition?
uterine milk secreted from the endometrium
What hormones are secreted by the placenta?
human chorionic gonadatropin
oestrogens
progesterone
homan chorionic somatrotropin
Human chorionic gonadatropin - where is it secreted from?
synctial trophoblasts
Human chorionic gonadatropin - function?
Prevents menstruation and causes the persistence of the corpus luteum
Increases to a peak at 10-12 weeks then decreases, can be measured in blood 8-9 days after ovulation
Causes corpus luteum to secrete more sex hormones and causes decidual cells to swell.
It also causes males to secrete testosterone and differentiate
Oestrogen - where is it secreted from and what are its functions?
Placenta
Causes enlargement of uterus, breasts, breast ducts, external genitalia and relaxation of pelvic ligaments
Progesterone - where is it secreted from and what are its functions?
Placenta - concentration increases over time
Causes decidual cells to develop and nurish early embryo, decreases contractility of uterus (preventing spontaneous abortion), increases secretions of fallopian tubes for nutrition, helps oestrogen prepare breasts for lactation
Human Chroionic somatomammotropin - where is it secreted from and what are its functions?
Placenta after 5th week
Decreases insulin sensitivity, decreases use of glucose by the mother to provide more for the baby. Promotes the release of free fatty acids, can promote growth
Changes in mother during pregnancy?
Increased uterine blood flow Increased cardiac output increased blood volume increased BMR weight gain increased urine production increased GFR Increased blood pressure
What is the normal weight gain during pregnancy?
24 pounds - most in the last trimester
7lb foetus 4lb amniotic fluid 2lb uterus 2lb breast 9lb other
What are the 3 antibody preparations used in pregnancy testing?
Reaction zone - monoclonal anti-HCG Ab-enzyme conjugate
Test zone - immobilised polyclonal anti-HCG antibodies +dye
Control zone - immobilised goat anti-mouse antibodies +dye
What are the foods to avoid during pregnancy?
Vitamin A - liver Pate (listeria) Soft cheese Unpasteurised milk Raw egg (salmonella) Rare meat (toxoplasmosis) tuna (mercury) raw shellfish caffeine
How many antenatal appointments for a nulliparous woman?
10
How many antenatal appointments for parous woman?
7
When are the antenatal appointments and what happens at each?
12 weeks - lifestyle advice, screening
16 weeks - review test and offer iron if anaemic
19 weeks - testing for foetal structural abnormalities
25 weeks NP - routine checks
28 weeks - routine checks, antiD prophylaxis for rhesus negative. pertussis vaccination
31 weeks NP - routine checks and review of screening
36 weeks - routine checks, checking of foetal position with external cephalic version offered if breech
38 weeks - routine checks
40 weeks - routine
41 weeks - membrane sweep and or labour induction
What are the normal routine checks carried out during an antenatal appointment?
BP check
Proteinuria screening
Symphysis fundal height + plotting
What diseases are screened for in pregnancy?
anaemia HIV hep B rubella syphilis sickle cell thalassaemia Downs
What are the dangers of alcohol in pregnancy?
Damages brain and affects childs behaviour Slow growth, development delay mental retardation foetal alcohol syndrome miscarriage risk
What are the signs of foetal alcohol syndrome?
facial deformities
slow and retarded development
brain and neurological problems
What are the dangers of smoking in pregnancy?
Still birth Premature delivery Low birth weight Stunted growth and development Under developed lungs Sudden infant death syndrome Learning disorders
What is ovulation induction and what are the risks?
Medications are used to stimulate the follicles in the ovaries to produce more than one egg per cycle
Clomiphene citrate
SERM
gonadotropins
Increase the chance of multiple births and of developing ovarian cysts
Ovarian hyperstimulation syndrome
What are the stages of IVF?
- Down Regulation - Switching off normal female hormone production
- Stimulation of follicle production
- Egg maturation
- Preparing womb to receive embryos
- Egg collection - oocyte capture
- Embryo transfer
What is used for down regulation in IVF?
Gonadotropin-releasing hormone analogues
Buserelin
Goserelin
What is used for egg maturation in IVF?
Pregnyl - works like hCG
Prepares them for collection
Given 36 hours before
What is used for preparing the womb in IVF?
Utrogestran - works like progesterone to keep lining thick
What are the rules for embryo transfer in under 37s?
1st cycle - 1 embryo
2nd cycle - 1 embryo unless not top quality
3rd - 2 embryo maximum
What are the rules for embryo transfer between 37-39?
1st and 2nd cycle - one unless not top quality
3rd - 2 embryos maximum
What are the rules for embryo transfer between 40-42?
Double egg transfer
What are the criteria for IVF referral?
Women under 40 who have not conceived after 2 years of regular unprotected intercourse
OR - 12 cycles of artificial insemination
= 3 IVF cycles
If 40-42 years = 1 IVF cycle
What are the limitations of ART?
High cost of treatment Age of female partner Religious complications Access is limited Side effects of drugs Increased ectopic pregnancy
What are the success rates of artificial reproduction techniques?
41 = 12%
Describe the blood supply to the placenta
2 umbilical arteries (from the internal iliac arteries)
drained by 1 umbilical vein
Describe the flow of blood through the placenta
- Placental villus required for maternal exchange
- Umbilical arteries enter placenta
- Divide into many branches
- Small arteries branch into placental villi
- Foetal capillaries bring in foetal blood from umbilical arteries
- Blood leaves through sinusoidal capillaries to venous
- Mother forms a reservoir so blood envelopes placental villus
What are the 2 layers of the placental villus?
Syncytiotrophoblast (outermost)
Cytotrophoblast
What is the syncytiotrophoblast?
Outermost layer of placental villus
Exchange via passive diffusion, facilitated diffusion and active transport and occurs through fully differentiated epithelial cels
What is the cytotrophoblast?
Less differentiated but can become syncytiotrophoblasts if required.
As syncytiotrophoblast cells die they form synctial knots which eventually break off into mothers blood
Outline placenta formation
- Blastocyst escapes from zona pellucida
- Trophoblast adheres to endometrium
- Endometrium undergoes decidualisation
- Decidual reaction as blastocyst implants
- Trophoblast cells release proteases to invade endometrium
- Trophoblasts differentiate into cytotrophoblasts surrounded by syncytiotrophoblasts
What happens in the decidual reaction?
Dilation of blood vessels
Increased capillary permeability
Oedema
Increased proliferation of glandular and epithelial cells
Define pre-eclampsia
Systemic syndrome characterised by widespread maternal endothelial dysfunction presenting clinically with oedema, hypertension and proteinuria
When does pre-eclampsia occur?
3-5% of pregnancies
Last trimester
More common in first pregnancy
What is HELLP syndrome/
Haemolysis
Elevated liver enzymes
Low platelets
Define congenital defect
Any abnormality, structural or functional, identified at any age, which began before birth or the cause of which was present before birth
What is the incidence of congential physical defects?
2-3% of live born infants
Leading cause of peri-natal death (20-25%)
What are common single primary defects?
DDH Talipes Cleft lip/palate Cardiac septal defects Neural tube defects
How can single primary defects be categorised?
Malformation
Disruption
Deformation
Sequence
What is a malformation?
Abnormal initial formation of embryo
Result of genetic and or environmental factors during organogenesis
e.g. neural tube defect
Describe the position of the breast
Sternal edge to midaxillary line
2nd to 6th rib
What is a disruption?
A destructive process which alters normal structures after their formation
Amniotic bands - limb amputations
Cardiovascular events - e.g. Poland anomaly
How is the breast of the skin attached to the dermis?
Suspensory ligaments of Cooper
What is the clinical importance of ligaments of cooper in breast cancer?
With cancer and fibrosis it causes a dimpling of the overlying skin
Pitting of the oedematous skin (lymphatic)
What is a deformation?
Moulding of a body part that has differentiated normally by mechanical forces usually over a long period of time
e.g. DDH, talipes
What is talipes?
1/ 1000
Club foot
Foot turned inwards and upwards
Short Achilles tendon - fixed flexion
What is DDH?
Development dysplasia of the hip 1-3% Screened Females and breech birth are risk factors Swaddling
What is a sequence?
Pattern of multiple anomalies that occurs early and produces a cascade of 2y and 3y error in morphogenesis
Pierre Robin Sequence
Define teratogen
An environmental agent that causes abnormalities of form or function in an exposed embryo or foetus
Sufficient amounts
Appropriate time
Susceptible individual
Give examples of teratogens
CMV Herpes Toxoplasmosis Alcohol Thalidomide Drugs Ionising radiation
What prevention and screening is available in pregnancy to reduce birth defects?
Oral folate supplementation Rubella vaccination Avoidance of risk factors Genetic counselling Donor gametes Antenatal screening (ultrasound)
