Block 11 - Reproduction and the growing child (pre-birth) Flashcards
3 things that sperm acquire during capacitation
Whiplash tail
Changes to the acrosome
Enzyme release
How do sperm travel the 20cm to the site of fertilisation?
Own motility
Uterine/oviduct contractions
Explain how sperm bind with the egg
Sperm release hyaluronidase to digest through the cumulus and acrosin enzymes to digest through the zone pellucida
Sperm interacts with glycoproteins ZP2/3 on the zona pellucida –> engulfed
Explain what resumes meiosis in the egg
Sperm bind –> phospholipase zeta which increases Ca causing a breakdown of maturation promoting factor, resumption of meiosis and extrusion of the 2nd polar body
Explain how only one sperm binds
Egg releases corticol granules that migrate to the edge during maturation and release components between it and the zona pellucida
Causes a conformational change in the ZP2/3 glycoproteins so no more sperm can enter
Define:
Polyspermic
Digynic
Parthenogenetic
Polyspermic: 2 sperm –> 3 pronuclei
Digynic: egg doesn’t complete meiosis –> 3 pronuclei
Parthenogenetic: no fertilisation but Ca triggered so the egg completes meiosis
What 2 things make up the zygote?
A male and a female POLAR BODY
What day is a blastocyst made?
5 days q
How and when is the zygotic genome activated?
What problems can arise?
4 cell stage
Methylation wipes and genome re-methylated to express its own genome
Problems here effect every cell in the body
Define the morula stage
The final stage before the cavity begins to grow
What hormone is stopping menstruation dependent upon?
Blastocyst produces a compound which acts on the uterine epithelium
- Signals the ovary to continue producing progesterone
- Release of hCG which signals the ovary to maintain the corpus luteum
What synthesises hCG and progesterone?
Syncytial trophoblast
What happens to the placenta if twins split at the:
- 2/4 cell stage
- Inner mass cell stage
Which one leads to nutrient stealing?
2/4 cell stage: 2 independent blastocysts with own placental membrane
Inner mass cell stage: share an outer placental sack but own inner sack (NUTRIENT STEALING)
How much does 1 round of IVF cost
£5,000
What percentage of couples under 35 become pregnant after 1 year of regular unprotected sex?
What percentage after 2 years?
80%
90%
What is the role of a GnRH agonist and antagonist?
What is the role of a FSH agonist?
GnRH: To decrease FSH and LH
FSH: To increase the number of follicles recruited when needed
5 main causes of infertility
- Male infertility (no sperm or ejaculatory failure)
- Unexplained
- Ovulatory disorder
- Tubal disease
- Endometriosis
What is the pre-implantation embryo vulnerable to?
Nutritional, biochemical, physical and metabolic changes
May lead to things such as insulin resistance or metabolic disorders
Who regulates fertility treatment?
HFEA
Who might frozen embryos benefit the most?
Older women
Trimester 1
4 foetal changes
2 maternal changes
Foetus: Fertilisation, Implantation, Placenta, Initial development
Mother: Increased weight, nausea
Trimester 2
4 foetal changes
5 maternal changes
Foetus: Nervous system, spine, proportions change, hair
Mother: heart and breast remodel, uterus rises, hypovolemia, placenta growth
Trimester 3
5 foetal changes
4 maternal changes
Foetus: Growth, lung development, brain growth, fat deposition, blood cells
Mother: Braxton hicks, tired, lactation, restricted breathing
What happens to the maternal heart rate, blood pressure and blood volume during pregnancy?
Heart rate and blood volume increase
Blood pressure stays the same
What happens to the foetal heart rate and size during pregnancy?
Heart rate increases during the 1st trimester to 180
It then decreases the 140 and remains constant
Slow increase in size from trimester 1-2
Large increase in size in trimester 3
How and when does the embryo implant into the uterine wall?
In week 4 the egg hatches from the zona pellucida
Trophoblast cells form villi which interdigitate with the uterine epithelium villi and destroy the primary decidua in the uterine wall
Where does the embryo develop in relation to the uterine wall?
Development occurs in the uterine wall and pushes into the uterine lumen
Explain how the foetus forms a blood supply with the mother
Pluriblast surrounded by cytotrophoblast cells which are then surrounded by syncytial trophoblast cells which invade into the utrine epithelium
Syncytial trophoblast cells contain trophoblastic lacunae. Invading maternal vessels anastamose with the lacunae allowing blood transfer
What is the term used for the type of support given to the foetus by the lacunae?
Histotrophic support
When does the female reproductive cycle switch from cyclical to pregnant?
Week 3-4
6 effects of an increase in oestrogen and progesterone on the mother
Supression of menses Tender and enlarged breasts Nausea and vomiting Increased urinary frequency Fatigue Constipation
Explain how the ectoderm, mesoderm and endoderm form
- Trophoblast surrounds the embryo and pluriblast in the middle
- Pluirblast splits into the Epiblast and Hypoblast
- Epiblast produces the ectoderm and mesoderm
Hypoblast produced the endoderm and grows around the internal cavity inside the trophoblast
What are the three parts of the placenta and what germ layers are they made from?
Amnion: Ectoderm and mesoderm
Chorion: Trophoblast and mesoderm
Yolk sack: Endoderm and mesoderm
Give two ways which the spiral arteries are remodelled
Why?
Increased volume and decreased pressure
Increased blood pressure in the spiral arteries is damaging
Why does histotrophic support seize?
What happens to overcome this?
What prevents mixing?
Lacunae cannot support the embryo for long
Syncytial trophoblast grow along spiral arteries
Villi form from the lacunae to the maternal blood allowing pooling
Trophoblasts form a barrier to prevent mixing
Define foetal lobule
A villi terminating in a spiral artery lacunae
Where do the villi conentrate on the uterine wall?
Chorionic plate of the placenta
How heavy is the placenta?
What is its diameter?
1/6 of the baby’s weight
20cm diameter
How does the pCO2 of foetal and maternal blood compare?
Why?
PCO2 of foetal blood is higher than maternal blood
Allows the release of CO2
What is the role of hCG in the pregnancy? (3)
Maintains the corpus luteum
Stimulates the thyroid
Promotes mammary growth
What is the role of oestrogen in the pregnancy? (4)
Relaxes pelvic ligaments
Increases elasticity of the symphysis pubis
Braxton-Hicks
Differentiation and proliferation of breast ductal system
What is the role of progesterone in the pregnancy? (4)
Increases oviduct and uterine secretions
Decreases uterine contractions
Prepares the endometrium for pregnancy
Growth of the ductal system in the breast
What is the name of the other hormone which is important in pregnancy?
Somatomammotropin
Why do levels of HcG decrease?
The placenta produces the hormones, not the foetus
How do oestrogen and progesterone cause the blood volume to increase? (6)
Vasodilation Decreased peripheral resistance Increased NO Increased aldosterone Increased thirst centre Angiogenesis
What can increased blood volume cause?
Oedema
2 things which increase the risk o UTIs
Urinary stasis
Increased glucose and amino acids in the urine
Why do you breathe deeper and increase your tidal volume
Sensitivity to chemoreceptors reduced
Increased CO2 in the blood
What is HPL
What is its role
Human placental lactogen
Mimics prolactin and GH to enlarge the breasts
What is the average weight gain during pregnancy?
When does most of the weight gain occur?
24lb (11kg)
First trimester (2-4 a week)
Then 1lb a week
5 aims of antinatal care
Monitor pregnancy progress and optimise health Partnership between mother and midwife Promotes choices and public health Recognise problems Prepare for birth and parenthood
MBRRACE-UK
Mother and Babies Reducing Risk through Audits and Confidential Enquiries
National maternity review (4)
Personalised and continuity of care (reduced case load, on call constantly)
Safer care
MDT
Mental health
When do the antenatal visits take place?
1: 8 weeks
2: 16 and (25) weeks
3: (31), 34, 36, 38, (40), 41
6 things that the blood test looks for
ABO blood group Rhesus factor Antibodies FBC Viruses e.g. Syphilis, Hep B, HIV Haemaglobinopathies
5 other parts of the physical examination other than the abdominal examination
Weight Blood pressure Urinalysis Oedema Varicosities
Define a cephalic presentation
Spine-spine
When does the baby engage?
36 weeks
Define multiparous
More than 4 children
Define gravida para
Gravida 3 Para 1+1
Third pregnancy, lost one child and has one child
8 risk factors for loss of a baby
Disease Proteinuria (pre-eclampsia) Large increase in blood pressure Significant oedema Uterus too large or small (diabetes) Bleeding (placenta detached) Infection Social/psychological problems
6 forces of retention (labour)
- Progesterone and Adrenaline (maintains)
- Cervix (hard)
- Hypovolemia (reduces hormone release)
- Relaxin
- Corticotrophin releasing hormone (inhibits prostaglandins)
7 forces of release (labour)
- Oestrogen
- Oxytocin and Vasopressin (pituitary –> uterine contraction)
- Cortisol (blocks progesterone)
- Prostaglandin (dilates and softens cervix)
- Uterine distention (uterus reaches max strength)
- Corticotrophin releasing hormone (inhibits prostaglandins)
What are the 4 stages of labour?
What are the 3 components?
Latent - 1st - 2nd - 3rd
Passage - Power - Passenger
What are the two positions of the baby’s head?
Occipital posterior (baby looks UP) Occipital anterior (baby looks DOWN)
What nerve supplies the pelvic floor
Pudendal nerve
How does the baby’s head rotate in the pelvis
Pelvic inlet is wider in transverse so baby engages in transverse
Pelvic outlet is wider in AP so head rotates round to AP