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1
Q

What day does implantation occur

A

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

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2
Q

How do the cytotrophoblast cells invade the spiral arteries

A

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

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3
Q

What is the most common implantation site for an ectopic

A

95% - fallopian tube - 80% in the ampulla

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4
Q

What is the incidence of syndactyly

A

1/2000

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5
Q

What is the incidence of cleft palate

A

1/700 - 1/1000

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6
Q

What is the incidence of Down’s at 25,35,40

A

1/2000

1/300

1/100

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7
Q

What is the survival rate of Turners

A

98% spontaneously aborted

Only monosomy compatible with lige

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8
Q

What are the features of Turner’s syndrome

A 
Gonadal dysgenesis
Short stature
Webbed neck
Lymphoedema of the extremities
Skeletal deformities
Broad chest, widely spaced nipples
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9
Q

What is the most frequent cause of turner’s

A

non-disjunction in male gamete

In remainder:

  • structural abnormalities of X
  • mitotic nondysjunction –> mosaicism
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10
Q

What is triple X syndrome

A

47XXX

Often go undiagnosed (mild physical features)
Speech problems and self esteem

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11
Q

What are the causes of structural abnoramlities

A

Usually, result from chromosome breakage

```
Environmental factors
- viruses
-radiation
-drugs
evidence inconclusive
~~~

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12
Q

What is a deletion and an example of a syndrome

A

broken piece of chromosome lost

Cri du chat

  • short arm chromosome 5
  • cat-like cry
  • microcephaly
  • intellectual disability
  • CHD
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13
Q

How many genes do microdeletions affect? What are the sites called?

A

Only a few contiguous genes

Contiguous gene complexes
-usually identified by FISH

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14
Q

What does q and p mean in the context of chromosome

A

q - long arm

p - short arm

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15
Q

What syndromes result from a microdeletion on 15q

A

Prader-Willi

Angelman’s

  • intellectual disability
  • cannot speak
  • poor motor development
  • prone to unprovoked and prolonged periods of laughter
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16
Q

What are regions of chromosomes that are liable to break called?

A

Fragile sites

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17
Q

What is fragile X syndrome

A

intellectual disability
large ears
prominent jaw
large testes

X linked - male preponderance

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18
Q

How does FiSH work

A

Fluorescent probes hybridised to chromosomes or genetic loci using cells on a slide, and the results are visualised with a fluorescence microscope

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19
Q

What do the oocytes form from

A

PGC –> oogonia–>primary oocyte (after M1) –>

Many primary oocytes degenerate and become atretic
- primary oocyte and surrounding epithelial cells (primordial follicle)

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20
Q

What is the dictyate state

A

arrest between prophase 1 and metaphase 1 also P1&M1

induced by oocyte maturation inhibitor (secreted by follicular cells)

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21
Q

What specifies fate of NCC

A

BMP concentrations

  • high levels - epidermis
  • intermediate -
  • low levels - neural ectoderm
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22
Q

What is the incidence of NTD

A

US - 1/1000

50-70% can be prevented with 400 mics folic acid daily

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23
Q

what does the intermediate mesoderm form

A

urogenital structures

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24
Q

What does the lateral plate form

A

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

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25
What is the role of the yolk sac
Unclear - nutritive organ prior to the establishment of circulation - contributes some of the first blood cells
26
What is ectopia cordis
Lateral body wall folds fail to fuse -heart lies outside the thoracic cavity -
27
What is the prevalence of IUGR and what are some complications
1/10 ``` Neurological problems Congenital malformations Meconium aspiration Hypoglycaemia Hypocalcaemia RDS ```
28
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
29
What percentage of twins are born preterm
60%
30
How common is TTTS
15% monozygotic Foetal death of both twins in 50-70%
31
Mutation to which gene can cause syndactyly and polydactyly
HOXD12
32
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
33
What is the incidence of transposition
4.8/10,000
34
Why do the umbilical arteries close
Smooth muscle contraction | -probably due to thermal and mechanical stimuli and altred oxygen tension
35
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
36
What is the incidence of tracheoesphageal fistula
1/3,000 90% result in blind pouch with lower segment that is continous with the trachea
37
What molecule specifies the liver
HOX
38
What molecule specifies the midgut
CDXC
39
What molecule specifies the hindgut
CDXA
40
What molecule specifies the foregut
SOX2
41
What molecule specifies the duodenum
PDX1
42
Why does oesophageal atresia causes polyhydramnios
Lack of swallowing of amniotic fluid
43
What do testosterone and dihydrotestosterone do
Testosterone - virilisation of mesonephric ducts Dihydrotestosterone - modulates differentiation of male external genitalia
44
Name some uterine abnormalities
Uterine didelphys -double uterus Uterus bicornis
45
What gene is responsible for treacher collins
TCOF1 | -transcribes treacle - involved in NCC differentiation
46
What gene mutation can cause NTD
Shh - establishes ventral midline
47
What is the incidence of anencephaly
1/5000
48
What is the master gene for heart development
NKX 2.5
49
What is the master gene for left sidedness
PITX2
50
What genes are thought to cause looping
NKX2.5 upregulates HAND1 and HAND2 which are expressed and later restricted to R and L
51
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
52
List some acyanotic heart defects
PDA VSD ASD
53
What structures do the NCC form
``` Viscerocranium Cartilage Bone Dentin Tendon Dermis Pia Arachnoid Sensory neurones Glandular connective tissue ```
54
Name the mesenchymal prominences
Mandibular Maxillary Frontonasal Nasal
55
What causes anterior clefting (palate)
Deficiency in mesenchyme in maxillary prominences and median palatal process
56
What causes posterior clefting (palate)
Defective growth of lateral palatal processes
57
What causes cleft lip
failure of maxillary prominence to fuse with the merged medial nasal prominences
58
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
59
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
60
What happens in the acrosome reaction
capacitated sperm bind to the zona pellucida Proteins induce the acrosome reaction Enzyme release to penetrate zona
61
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
62
How can ovulation be induced
Clomiphene citrate - oestrogen antagonist - suppresses normal negative feedback GnRH FSH or LH
63
What are some indications for IVF
Tubal disease Endometriosis Unexplained infertility Mild male infertility
64
What is the overall incidence of downs
1/750
65
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 ```
66
What proportion of situs inversus have complication
20% PCD
67
What is the difference between dextrocardia and situs inversus
Dextrocardia -just heart Situs inversus -transposition of all abdominal viscera
68
What is the detection rate for Down's in the combined test
80% | Increased hCG, decreased PAPP-A
69
Which is the most accurate way at estimating gestational age
*Crown-rump length Bi-parietal diameter Femoral length Menstrual age
70
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 ```

BSc Embryology (7 decks)

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