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BSc Embryology > Bits > Flashcards

Bits Flashcards

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
Q

What is the role of the yolk sac

A

Unclear

  • nutritive organ prior to the establishment of circulation
  • contributes some of the first blood cells
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26
Q

What is ectopia cordis

A

Lateral body wall folds fail to fuse
-heart lies outside the thoracic cavity
-

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27
Q

What is the prevalence of IUGR and what are some complications

A

1/10

Neurological problems
Congenital malformations
Meconium aspiration
Hypoglycaemia
Hypocalcaemia
RDS
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28
Q

What are some risk factors for IUGR

A

Black ethnicity

Infection
-Toxoplasmosis, syphilis, rubella, cytomegalovirus

Poor maternal health and nutrition

Low socioeconomic status

Cigarettes, alcohol, drugs

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29
Q

What percentage of twins are born preterm

A

60%

30
Q

How common is TTTS

A

15% monozygotic

Foetal death of both twins in 50-70%

31
Q

Mutation to which gene can cause syndactyly and polydactyly

A

HOXD12

32
Q

Describe the formation of the interatrial septum

A

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
Q

What is the incidence of transposition

A

4.8/10,000

34
Q

Why do the umbilical arteries close

A

Smooth muscle contraction

-probably due to thermal and mechanical stimuli and altred oxygen tension

35
Q

When does the lung bud first develop

A

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
Q

What is the incidence of tracheoesphageal fistula

A

1/3,000

90% result in blind pouch with lower segment that is continous with the trachea

37
Q

What molecule specifies the liver

A

HOX

38
Q

What molecule specifies the midgut

A

CDXC

39
Q

What molecule specifies the hindgut

A

CDXA

40
Q

What molecule specifies the foregut

A

SOX2

41
Q

What molecule specifies the duodenum

A

PDX1

42
Q

Why does oesophageal atresia causes polyhydramnios

A

Lack of swallowing of amniotic fluid

43
Q

What do testosterone and dihydrotestosterone do

A

Testosterone - virilisation of mesonephric ducts

Dihydrotestosterone - modulates differentiation of male external genitalia

44
Q

Name some uterine abnormalities

A

Uterine didelphys
-double uterus

Uterus bicornis

45
Q

What gene is responsible for treacher collins

A

TCOF1

-transcribes treacle - involved in NCC differentiation

46
Q

What gene mutation can cause NTD

A

Shh - establishes ventral midline

47
Q

What is the incidence of anencephaly

A

1/5000

48
Q

What is the master gene for heart development

A

NKX 2.5

49
Q

What is the master gene for left sidedness

A

PITX2

50
Q

What genes are thought to cause looping

A

NKX2.5 upregulates HAND1 and HAND2 which are expressed and later restricted to R and L

51
Q

List some cyanotic heart defects

A

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
Q

List some acyanotic heart defects

A

PDA
VSD
ASD

53
Q

What structures do the NCC form

A 
Viscerocranium 
Cartilage
Bone
Dentin
Tendon
Dermis
Pia
Arachnoid
Sensory neurones
Glandular connective tissue
54
Q

Name the mesenchymal prominences

A

Mandibular
Maxillary
Frontonasal
Nasal

55
Q

What causes anterior clefting (palate)

A

Deficiency in mesenchyme in maxillary prominences and median palatal process

56
Q

What causes posterior clefting (palate)

A

Defective growth of lateral palatal processes

57
Q

What causes cleft lip

A

failure of maxillary prominence to fuse with the merged medial nasal prominences

58
Q

What are the steps of sperm maturation

A

Condensation of the nucleus

Formation of the acrosome

Formation of the neck, middle, tail

Shedding of the cytoplasm

59
Q

What happens in capacitation

A
  • Occurs in fallopian tube
  • Interaction between sperm and the tube
  • allows sperm to penetrate corona radiata
  • plasma protein removed from mmbr overlying acrosome
60
Q

What happens in the acrosome reaction

A

capacitated sperm bind to the zona pellucida

Proteins induce the acrosome reaction

Enzyme release to penetrate zona

61
Q

What happens upon the sperm reaching the egg

A

Penetration of corona radiata

Penetration of zona pellucida

Fusion of cell mmbr
-oocyte immediately completes M2

Diploid number

Initiation of clevage

62
Q

How can ovulation be induced

A

Clomiphene citrate

  • oestrogen antagonist
  • suppresses normal negative feedback

GnRH

FSH or LH

63
Q

What are some indications for IVF

A

Tubal disease
Endometriosis
Unexplained infertility
Mild male infertility

64
Q

What is the overall incidence of downs

A

1/750

65
Q

What is a symptoms of downs

A 
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
Q

What proportion of situs inversus have complication

A

20% PCD

67
Q

What is the difference between dextrocardia and situs inversus

A

Dextrocardia
-just heart

Situs inversus
-transposition of all abdominal viscera

68
Q

What is the detection rate for Down’s in the combined test

A

80%

Increased hCG, decreased PAPP-A

69
Q

Which is the most accurate way at estimating gestational age

A

*Crown-rump length

Bi-parietal diameter
Femoral length

Menstrual age

70
Q

What is the incidence of FAS

A

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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