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BSc Embryology > Practical 2 - Foetal Malformations > Flashcards

Practical 2 - Foetal Malformations Flashcards

1
Q

What are the 3 primary brain vesicles

A

Prosencephalon
Mesencephalon
Rhombencephalon

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2
Q

What does the prosencephalon become

A

Telencephalon - cerebral hemispheres

Diencephalon - optic cup, stalk, pituitary, thalamus, hypothalamus, hypothalamus, epiphysis

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3
Q

What does the mesencephalon

A

Midbrain

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4
Q

What does the rhombencephalon

A

Metencephalon - cerebellum and pons

Myelencephalon - medulla

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5
Q

When do the cerebral hemisphere begin to develop

A

Beginning of 5th week

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6
Q

What are NCCs. What do they give rise to

A

Ectodermal origin
- give rise to sensory ganglia
(Sympathetic neuroblasts, Schwann cells, pigment cells, meninges, mesenchyme of pharyngeal arches)

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7
Q

Why do anencephalic foetuses get polyhydramnios

A

Lack swallowing reflex

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8
Q

What is exencephaly

A

Failure of cephalic part of neural tube to close
Vault doesn’t close
Brain expands
Tissue degenerates —> anencephaly

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9
Q

How are NTDs preventable

A

400 micro grams folic acid per day

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10
Q

What is the detection rate of anencephaly

A

90% on foetal anomaly screen

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11
Q

Why does hydrocephalus occur

A

Aqueducts stenosis 1/5,000

  • obstruction of aqueduct of Sylvius
  • prevents CSF of lateral and 3rd ventricle passing into 4th ventricle
  • pressure on brain and cranium —> expansion
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12
Q

What is a meningocoele

A

Germination of meninges outside vertebral column

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13
Q

What is the incidence of hydrocephalus in myelomemingocoele

A

80-90%

- often related to Arnold chiari malformation —> herniation of cerebellum through f magnum

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14
Q

What are the RF of NTD

A

Hyperthermia
Folic acid deficiency
Valproic acid
Hypervitaminosis A

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15
Q

What is the marker for NTD detected in maternal serum and amniotic fluid

A

Alpha foetoprotein

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16
Q

When does the limb bud appear

A

4/5th week

v sensitive time for limb development

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17
Q

What is the limb bud composed of

A

Core - from lateral plate mesoderm

Ectoderm - tip of limb bud

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18
Q

What is the AER

A

Apical ectodermal ridge
- tip of limb, ectoderm induced to thicken

  • induces underlying mesenchyme to remain as a proliferating population of undifferentiated cells (progress zone)
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19
Q

What group of factors control proximidistal patterning

A

Fibroblastic growth factors

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20
Q

How are the digits formed for handplate

A

Circular construction separates hand and feet from proximal segments

Apoptosis in AER separates into digits

Continued outgrowth under influence of ectoderm

Apoptosis of intervening tissshe

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21
Q

What genes are essential for craniocaudal patterning

A

HOX genes

Disruption

  • hand foot genital syndrome
  • fusion of carpal bones, small short digits
  • bicorute uterus
  • hypospadias
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22
Q

What group of proteins is crucial for dorsoventral patterning

A

BMP

- induce expression of EN1 - inhibits WNTTa

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23
Q

What is the incidence of limb defects

A

6/100,000

  • 3.4 - upper limb
  • 1.1 0 lower limb
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24
Q

What is phocomelia

A

Deformity or absence of long bones, intestinal atresia, cardiac abnomralities
-thalidomide

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25
Q

What is amelia

A

Absence of one or more of the extremities

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26
Q

What is polydactyl

A

Presence of extra fingers or toes

  • extra digits frequently lack proper muscle connections
  • Usually biltaeral

(Absence of a digit (ectrodactyly) occurs unilaterally

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27
Q

What is cleft foot

A

Abnormal cleft between the second and fourth metacarpal bones and soft tissues

Third metacarpal and phalangeal bones are almost always absent
Thumb and index finger may be fused

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28
Q

What is syndactyl

A

Two or more fingers or toes are fused

-mesenchyme between prospective digits do not undergo the normal apoptosis to make discrete digits

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29
Q

What are the environmental factors that cause limb defects

A 
Radiation*
Infection
Thalidomide
Pesticide and insecticide exposure 
Maternal smoking
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30
Q

What intra-uterine factors affect limb development

A

Amniotic bands - adhesions between amnion and affected structures in the foetus

  • cause ring constriction
  • Amputations of limb or digits
  • origin unclear
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31
Q

What is chondrodystrophy

A

Skeletal dysplasia caused by abnormal cartilage development

- may be caused by a number of genetic mutations that can be inherited

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32
Q

What is achondroplasia

A

1/20,000

Long bones - shortening of proximal limbs
Megalocephaly
Small midface
Short fingers

Autosomal dominant
90% sporadic
FGF 3 receptor mutation

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33
Q

How does the stomach end up a left sided organ

A

Start parallel to cranial-caudal axis
Rotates 90 degrees clockwise around longitudinal axis
- left -> anterior, right -> posteriro

Further growth -> rotation AP axis –> pylorus moves right

34
Q

What is pyloric stenosis

A 
1/1000
Signs occur between 3-5 weeks 
Projectile vomit
Unaffected appetite
Signs of dehydrations 
Fewer full nappies 
FTT

Genetic component
Boys>Girls

35
Q

What is physiological herniation

A

Rapid elongation of the gut and its mesentry form the primary intenstinal loop

6th week - the intestinal loops become too big for the abdo cavity

Enter extraembryonic cavity in umbilical cord

10th week intestinal loops begin to return

36
Q

What is an omphalocoele, why does it occur

A

Herniation of abdo viscera through enlarged umbilical ring (viscera covered by amnion)

Failure of bowel to return to body cavity during physiological herniation

37
Q

What is the incidence of ompalocoele and how is detected

A

1/4,000

USS
Also combined test 20 weeks (AFP)

38
Q

What is the prognosis of ompahlocoele

A 
High mortality (25%)
Severe malformations
-cardiac (50%)
-NTD (40%)
-Chromosomal abnormalities (15%)
39
Q

What is gastroschisis

A

Protrusion of abdo contents through body wall directly into amniotic cavity

Lateral to umbilicus

Abnormal closure of body wall around connecting stalk

Viscera not covered by peritoneum or amnion
-bowel may be damaged due to exposure to amniotic fluid

40
Q

What is the incidence of gastroschisis and what is the prognosis

A

1/2000

Frequency is increasing, especially among young women

Not associated with chromosome abnormalities or other severe defects

41
Q

What is the detection rate of gastroschisis on foetal anomaly screening and what is a potential complication

A

90%

Survival rate excellent

(Volvulus resulting in compromised blood supply may cause large areas of necrosis and lead to death)

42
Q

What are the three kidney systems and when do they develop

A

Pronephros

  • rudimentary-non-functional
  • disappeared by 4th week

Mesonephros

  • develops 4th week
  • may function for a time

Metanephros

  • Forms definitive kidney
  • starts to develop 5th week
43
Q

What does the ureteric bud give rise to

A

Nephrons
-outgrowth of mesonephric duct close to entrance to cloaca

  • bud penetrates metanephric tissue, which is moulded over its distal end
  • bud dilates -> primitve renal pelvis and splits into cranial and caudal portions (major and minor calyces)

Nephrons
Collecting ducts
Renal pelvis
Major and minor calyces

44
Q

What is polycystic kidney disease

A

Numerous cysts form in collecting ducts

Dominant and recessive variants

Both linked to mutations in genes encoding cilia proteins

45
Q

What is the complication of polycystic kidney disease

A

Renal failure
-recessive (1/5000) - infancy

-dominant - later

46
Q

What is horshoe kidney

A

1/600

Kidneys pushed so close together during ascent through arterial fork, fuse

inferior mesenteric artery prevents ascent - lower level

47
Q

Why do double ureters occur

A

early splitting of ureteric bud

Partial or complete splitting

May each have its own renal pelvis and metanephric tissue
-more commonly share lobules

48
Q

Why are accessory renal arteries common

A

derive from persistence of embryonic vessels formed during ascent of kidney

usually arise form aorta and enter pole of kidney

49
Q

What gene and protein determines sex

A

Sex determining region on Y (SRY) gene

Transcribes testis-determining-factor

In its presence, male development occurs

50
Q

When do the gonads differentiate as male or female

A

7th week

51
Q

Describe the development of the gonads

A

First appear
- genital ridges = epithelium w/ underlying mesenchyme

Primordial germ cells migrate 5th week

Invade genital ridges 6th week

Ridges proliferate –> primitive sex cords

Indifferent gonads

52
Q

What happens if Primitive germ cells don’t reach genital ridges

A

Gonads don’t develop

53
Q

What are the two genital ducts

A

Mesonephric (Wolffian)

Paramesonephric (Mullerian)

54
Q

In males, what dictates genital duct development

A

SRY & SOX9 –> antimullerian hormone

SRY upregulates -steroidogenesis factor (SF1)
-stimulates sertoli and leydig cell

SF1 & SOX9 increase AMH concentration

Regression of mullerian duct

Leydig cells produce testosterone

Converted to dihydrotestosterone in target tissues

Virilisation of wolffian duct

55
Q

What structures does the mesonephric ducts forms

A

Not cranial epididymis

Main genital ducts
epidymis –> seminal vesicles

56
Q

What is hypospadias

A

Incomplete urethral fold fusion

  • abnormal openings of the uerethra, usually inferior aspect
  • usually near flans, along shaft or near base of penis

Rarely, urethral meatus along scrotal raphe

If fusion fails entirely, wide sagittal slit along length of penis and scrotum - scrotum resembles labia majora

57
Q

What is the incidence of hypospadias

A

3-5/1000

Incidence has doubled over 15-20 years

58
Q

What is epispadias

A

1/30,000

Urethral meatus found on dorsum of penis

Often associated with exstrophy of the bladder and abnormal closure of ventral body wall

59
Q

How does an indirect hernia form

A

Abdominal contents herniate throught the inguinal canal into the scrotum

60
Q

Briefly describe gut tube formation

A

A portion of endoderm lined yolk sac cavity is incorporated into embyro –> primtive gut

Yolk sac and allantois remain extra-embryonic

61
Q

How is the gut tube patterned

A

Retinoic acid concentration gradient

  • pharynx - low
  • colon - high

Stomach: SOX2
Duodenum: PFX1
Hindgut: CDXA

62
Q

What are the major arteries that supply the gut

A

Celiac
Superior mesenteric
Inferior mesenteric

63
Q

What is a tracheoesophageal fistula and what is its incidence

A

1/2000-1/4000

Fistula between oesphagus and trachea
- can be a one just drain into trachea
OR
-Can drain into trachea, then drain out of trachea more distally

64
Q

How would a tracheosophageal fistula present

A 
•	Symptoms:
o	Frothy, white bubbles in the mouth 
o	Coughing or choking when feeding
o	Vomiting
o	Blue colour of skin, especially when feeding
o	SOB 
•	Complications
o	Aspiration
o	Pneumonia
o	Asphyxiation
65
Q

What are the RF for tracheosphageal fistula

A

exogenous sex hormones
Alcohol
Working in argiculture
VACTERL

66
Q

In females, what factors promote development of paramesonephric ducts and inhibit development of the mesonephric ducts

A

• WNT4 is the ovary-determining gene –> This gene upregulates DAX1 –> Inhibits the function of SOX9 (which upregulates Anti-mullerian hormone)

67
Q

In normal development, the paramesonephric ducts in the female give rise to what structures? What hormone is important here?

A
  • Uterine tubes, uterus, cervix and upper vagina.

* Oestrogens.

68
Q

What is spetate uterus

A

does what is says on the tin

69
Q

What is treacher-collins, what are the symptoms, what is the incidence

A

First arch abnormalities

1/40,000-1/70,000

Symptoms

  • Zygmatic hypoplasia
  • Mandibular hypoplasia
  • Downslanting palpebral fissures
  • lower eyelid colobomas
  • external ear malformation
  • Autosomal dominanet
70
Q

What is DiGeorge syndrome

A

1/4000

Microdeletion chromosome 11

Absent thymus and parathyroids

Immune defiency
Cardiac anomalies
Mild facial dysmorphology
-shortened philtrum
-low set ears
-nasal clefts

learning disabilities

71
Q

What is the anatomical marker for clefting

A

Incisive foramen

anterior - cleft tip, cleft jaw, cleft between primary and secondary palates

Posterior

  • cleft secondary palate
  • cleft uvular
  • defective growth of lateral palatal processes
72
Q

What is cleft lip

A

unilateral
-maxillary prominence fails to fuse with merged medial nasal prominences

Bilateral
- failure of both maxillary prominences to fuse with merged medial nasal prominences

73
Q

What is the incidence of cleft lip

A

1/700 - 1/1000

Male>Female

Aetiology

  • syndromic
  • genetic
  • non syndromic (70% CLP, 50% CPO)
  • Teratogen - benzos, rubella
74
Q

How does the palate form

A

intermaxillary segment fuse with palatine process
-primary palate

Fusion of palatine processes

  • secondary palate
  • palatine raphe
75
Q

Why does the palate fail to form

A

Failure of normal growth of palatal shelves

Failure of fusion of palatal shelves

Obstruction of palate fusion by tongue

Failure of shelve to rise above the tongue

76
Q

What are some complications of cleft lip and palate

A 
Difficulty feeding
Aspiration pneumonia
Speech and Hearing 
Dental problems
Cosmesis
77
Q

What is the paper on cleft palate

A

Johannsson and Ringsberg

  • cleft palate can be emotionally traumatic to parents
  • one of most common congenital malformations
  • otitis media common complciation
  • more severe clefting has more severe social implications
78
Q

Briefly describe the formation of the face

A

Facial prominences appear at the end of week 4 around the stomodeum

  • frontonasal prominence
  • maxillary prominence
  • mandibular prominence

Nasal placode invaginate in 5th week to form nasal pits and nasal prominences (medial and lateral)

Maxillary prominences grow larger and medially

Pushes nasal prominences towards midline, medial prominences fuse

Maxillary prominences fuse with medial nasal prominence

79
Q

What does the intermaxillary segment form

A

formed from fusion of two medial nasal prominences

3 parts

  • Labial - philtrum
  • Upper jaw - four incisors
  • Palatal - froms primary palate
80
Q

How does the nasolactimal groove and duct form

A

Maxillary prominence separated from lateral nasal prominence by nasolacrimal groove

Endoderm in the floor thickens to form a cord , detaches and canalises

BSc Embryology (7 decks)

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