Bits Flashcards
What day does implantation occur
Day 8
- blastocyst partially embedded in endometrial stroma
- in this area - trophoblast has differentiated into cyto and syncitiotrophoblast
Day 9
- Deeply embedded
Day 11/12
-completely embedded
How do the cytotrophoblast cells invade the spiral arteries
Syncytiotrophoblast penetrates stroma and erodes endothelial lining of maternal capillaries
Capillaries are congested and dilated = sinusoids
Syncitial lacunae become continous with sinusoids
Maternal blood flows through trophoblastic system, establishing uteroplacental circulation
What is the most common implantation site for an ectopic
95% - fallopian tube - 80% in the ampulla
What is the incidence of syndactyly
1/2000
What is the incidence of cleft palate
1/700 - 1/1000
What is the incidence of Down’s at 25,35,40
1/2000
1/300
1/100
What is the survival rate of Turners
98% spontaneously aborted
Only monosomy compatible with lige
What are the features of Turner’s syndrome
Gonadal dysgenesis Short stature Webbed neck Lymphoedema of the extremities Skeletal deformities Broad chest, widely spaced nipples
What is the most frequent cause of turner’s
non-disjunction in male gamete
In remainder:
- structural abnormalities of X
- mitotic nondysjunction –> mosaicism
What is triple X syndrome
47XXX
Often go undiagnosed (mild physical features)
Speech problems and self esteem
What are the causes of structural abnoramlities
Usually, result from chromosome breakage
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Environmental factors
- viruses
-radiation
-drugs
evidence inconclusive
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What is a deletion and an example of a syndrome
broken piece of chromosome lost
Cri du chat
- short arm chromosome 5
- cat-like cry
- microcephaly
- intellectual disability
- CHD
How many genes do microdeletions affect? What are the sites called?
Only a few contiguous genes
Contiguous gene complexes
-usually identified by FISH
What does q and p mean in the context of chromosome
q - long arm
p - short arm
What syndromes result from a microdeletion on 15q
Prader-Willi
Angelman’s
- intellectual disability
- cannot speak
- poor motor development
- prone to unprovoked and prolonged periods of laughter
What are regions of chromosomes that are liable to break called?
Fragile sites
What is fragile X syndrome
intellectual disability
large ears
prominent jaw
large testes
X linked - male preponderance
How does FiSH work
Fluorescent probes hybridised to chromosomes or genetic loci using cells on a slide, and the results are visualised with a fluorescence microscope
What do the oocytes form from
PGC –> oogonia–>primary oocyte (after M1) –>
Many primary oocytes degenerate and become atretic
- primary oocyte and surrounding epithelial cells (primordial follicle)
What is the dictyate state
arrest between prophase 1 and metaphase 1 also P1&M1
induced by oocyte maturation inhibitor (secreted by follicular cells)
What specifies fate of NCC
BMP concentrations
- high levels - epidermis
- intermediate -
- low levels - neural ectoderm
What is the incidence of NTD
US - 1/1000
50-70% can be prevented with 400 mics folic acid daily
what does the intermediate mesoderm form
urogenital structures
What does the lateral plate form
Parietal
-somatic muscles - lateral body wall folds
(dermis, bones & connective tissue of limbs, sternum)
Visceral
-splanchnic
wall of gut tube
NB scelerotome and muscle precursors that migrate into parietal layer form costal cartilages, limb muscles, most of body wall muscles
What is the role of the yolk sac
Unclear
- nutritive organ prior to the establishment of circulation
- contributes some of the first blood cells
What is ectopia cordis
Lateral body wall folds fail to fuse
-heart lies outside the thoracic cavity
-
What is the prevalence of IUGR and what are some complications
1/10
Neurological problems Congenital malformations Meconium aspiration Hypoglycaemia Hypocalcaemia RDS
What are some risk factors for IUGR
Black ethnicity
Infection
-Toxoplasmosis, syphilis, rubella, cytomegalovirus
Poor maternal health and nutrition
Low socioeconomic status
Cigarettes, alcohol, drugs
What percentage of twins are born preterm
60%
How common is TTTS
15% monozygotic
Foetal death of both twins in 50-70%
Mutation to which gene can cause syndactyly and polydactyly
HOXD12
Describe the formation of the interatrial septum
End of fourth week
- sickle shaped crest grows from roof of common atrium
- extend towards endocardial cushions
- opening between cushions and crest - ostium primum
Further growth of cushions
- ostium primum closed - septum primum left
- before closure - cell death - perforations - ostium secundum
Lumen of right atrium expands
- new cresecnt fold appear - septum secundum
- complete partition of atrial cavity
- valve
What is the incidence of transposition
4.8/10,000
Why do the umbilical arteries close
Smooth muscle contraction
-probably due to thermal and mechanical stimuli and altred oxygen tension
When does the lung bud first develop
week 4
-increases in RA causes upregulation of TBX4
-endodermal origin - parechyma, epthithelial
-mesodermal origin - structural mesenchyme
-initially, lung bud and foregut in open communication
x tracheooesphageal ridges separate
What is the incidence of tracheoesphageal fistula
1/3,000
90% result in blind pouch with lower segment that is continous with the trachea
What molecule specifies the liver
HOX
What molecule specifies the midgut
CDXC
What molecule specifies the hindgut
CDXA
What molecule specifies the foregut
SOX2
What molecule specifies the duodenum
PDX1
Why does oesophageal atresia causes polyhydramnios
Lack of swallowing of amniotic fluid
What do testosterone and dihydrotestosterone do
Testosterone - virilisation of mesonephric ducts
Dihydrotestosterone - modulates differentiation of male external genitalia
Name some uterine abnormalities
Uterine didelphys
-double uterus
Uterus bicornis
What gene is responsible for treacher collins
TCOF1
-transcribes treacle - involved in NCC differentiation
What gene mutation can cause NTD
Shh - establishes ventral midline
What is the incidence of anencephaly
1/5000
What is the master gene for heart development
NKX 2.5
What is the master gene for left sidedness
PITX2
What genes are thought to cause looping
NKX2.5 upregulates HAND1 and HAND2 which are expressed and later restricted to R and L
List some cyanotic heart defects
Tetralogy (progressive cyanosis)
Hypoplastic left heart syndrome
(survival only if PDA or PFO)
Total anomalous pulmonary venous return
(all four pulmonary veins connect to SVC)
Transposition
(Develops over first few hours)
Common truncus
List some acyanotic heart defects
PDA
VSD
ASD
What structures do the NCC form
Viscerocranium Cartilage Bone Dentin Tendon Dermis Pia Arachnoid Sensory neurones Glandular connective tissue
Name the mesenchymal prominences
Mandibular
Maxillary
Frontonasal
Nasal
What causes anterior clefting (palate)
Deficiency in mesenchyme in maxillary prominences and median palatal process
What causes posterior clefting (palate)
Defective growth of lateral palatal processes
What causes cleft lip
failure of maxillary prominence to fuse with the merged medial nasal prominences
What are the steps of sperm maturation
Condensation of the nucleus
Formation of the acrosome
Formation of the neck, middle, tail
Shedding of the cytoplasm
What happens in capacitation
- Occurs in fallopian tube
- Interaction between sperm and the tube
- allows sperm to penetrate corona radiata
- plasma protein removed from mmbr overlying acrosome
What happens in the acrosome reaction
capacitated sperm bind to the zona pellucida
Proteins induce the acrosome reaction
Enzyme release to penetrate zona
What happens upon the sperm reaching the egg
Penetration of corona radiata
Penetration of zona pellucida
Fusion of cell mmbr
-oocyte immediately completes M2
Diploid number
Initiation of clevage
How can ovulation be induced
Clomiphene citrate
- oestrogen antagonist
- suppresses normal negative feedback
GnRH
FSH or LH
What are some indications for IVF
Tubal disease
Endometriosis
Unexplained infertility
Mild male infertility
What is the overall incidence of downs
1/750
What is a symptoms of downs
Flat nasal bridge Macroglossia Epicanthal fold Flat occiput Large nuchal thickening Broad hands, short fingers Sandal gap Single palmar crease CHD (50%) Bowel problems
What proportion of situs inversus have complication
20% PCD
What is the difference between dextrocardia and situs inversus
Dextrocardia
-just heart
Situs inversus
-transposition of all abdominal viscera
What is the detection rate for Down’s in the combined test
80%
Increased hCG, decreased PAPP-A
Which is the most accurate way at estimating gestational age
*Crown-rump length
Bi-parietal diameter
Femoral length
Menstrual age
What is the incidence of FAS
0.2-1.5/1,000
Epicanthal fold Short palpebral fissue Thin upper lip Smooth philtrum Growth restriction Intellectual disability Behavioural problems Heart defects CNS defects
