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BSc Embryology > Practical 1 - Gametogenesis > Flashcards

Practical 1 - Gametogenesis Flashcards

1
Q

What causes a teratoma? What is the most common location

A

Disruption to normal migration of primordial germ cells

Sacrococcygeal teratoma*
Oropharyngeal teratoma

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2
Q

What is a trisomy

A

additional chromosome to homologous pair (n=47)

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3
Q

What is a syndrome

A

Collection of symptoms assc with genetic abnormality

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4
Q

What is Edwards syndrome and what are the symptoms

A

Trisomy 18

  • intellectual disability
  • CHD
  • Low set ears
  • Flexion of fingers and hands
  • Micrognathia
  • Renal abnormalities
  • Syndactyl &MSK malformations
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5
Q

What is the incidence of Edwards? How may make it to term?

A

1/5,000

35% lost by week 10 to term
Most live neonates die < 2 months
5% live beyond one year

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6
Q

What is Patau’s

A

Trisomy 13

  • Intelectual disability
  • Holoprosencephaly
  • CHD
  • Deafness
  • Cleft lip and palate
  • Anopthalmia
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7
Q

What is the incidence of Patau’s? How many survive?

A

1/20,000
90% dies within 1 month post natally
5% survive beyond 1 year

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8
Q

What is Klinefelters

A

47XXY - often due to nondisjunction of XX homologue

1/500

Found only in males, usually picked up on amniocentesis

  • Sterile
  • Testicular atrophy
  • Hyalinazation of seminferous tubules
  • Gynaecomastia
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9
Q

What is a barr body

A

inactive X chromosome in a female somatic cell, rendered inactive in a process called lyonization

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10
Q

What affects the phenotype after chromosome fragmentation

A

size of fragment

  • if fragment lost - deletion
  • if small amount lost - microdeletion

Fragile sites - tendency to break

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11
Q

What is Prader-Willi

A

Deletion of long arm chromosome paternal 15

(NB if maternal chromosome - Angelman’s (genomic imprinting)

  • hypotonia
  • obesity
  • intellectual disability
  • hypogonadism
  • Undescended testis
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12
Q

What is a zygote

A

Single celled embryo

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13
Q

What is morula

A

16 celled embryo

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14
Q

what is a blastocyst

A

Occurs at time of implantation

Outer layer - trophoblast (contains fluid filled sphere)
Inner cell mass - embyroblast cells

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15
Q

Where does fertilisation usually occur?

A

Ampulla of the fallopian tube

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16
Q

How many days post fertilisation does implantation typically occur

A

8/9

Occurs in body of uterus

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17
Q

How do intra-uterine contraceptives work

A

IUD - release progesterone - prevents ovum release

Copper - irritates uterine wall

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18
Q

What is the incidence of ectopic pregnancy and what are the RF

A

2% (1.1% RCOG)

RF:

  • Previous Hx
  • Fallopian tube damage - previous surgery or infection
  • Pregnancy w/ IUD or prog only pill
  • IVF
  • > 35 yrs
  • Smoker
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19
Q

What are the signs and symptoms of ectopic

A

LOWER ABDOMINAL PAIN ECTOPIC UNTIL PROVEN OTHERWISE

Pallor - hypovolaemic shock

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20
Q

What is a lithopaediaon

A

Dead ectopic that becomes calcified

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21
Q

What is endometriosis

A

Ectopic endometrial tissue
6-10%

  • dysmenorrhoea
  • Dypareunia
  • Pain on defaecation or micturition
  • Menorrhagia
  • Subfertility

NB irritation of peritoneum can cause adhesions and peritonitis

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22
Q

What structures can be affected by endometriosis

A 
Ovaries
Fallopian Tubes
Tissues around uterus and ovaries
Brain 
Lung
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23
Q

How do you manage endometriosis

A

Ablation

Progesterone contraception

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24
Q

How does endometriosis increase the risk of subfertility

A

Obstruction of the fallopian tube

May damage sperm or egg

Also increases risk of ectopic, reason unknown

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25
Q

What is the definition of subfertility

A

Failure to conceive after 1 year of trying

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26
Q

What are some male causes of sub fertility

A

CF
Aplastic vas deferens
Impotence
Decreased sperm count

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27
Q

What are some female causes of sub fertility

A

Fibroids
Abnormal shaped uterus
PCOS

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28
Q

Describe the development of the heart

A

Progenitor heart cells - derived from cranial end of primitive streak

Invaginate through primitive streak

Progenitor heart cells cluster on lateral plate mesoderm–> primary heart field (day 16-18)

PHF gives rise to atria, left ventricle, most of right ventricle

Primary heart fields are bilateral and will merge to form one cardiogenic tube

Secondary heart field appears (day 20-21) - gives rise to remainder of right ventricle and the outflow tract

(specifying laterality essential to ensure aorta arise from LV)

Cells are induced to form myoblasts and blood islands

Blood islands unite to form a tube surrounded by myoblasts (cardiogenic region)

Central part of tube expands - becomes bentricles and outflow tract

Heart tube formed in three layers (endo, myo, epicardium)

Heart tube elongates as cells added cranially from teh SHF - outflow tract elongation

Cardiac looping day 23-28

Major septa develop day 27-37 - formed by outgrowth of endocardial cushions

(interatrial, interventricular, AV valves and aortic and pulmonary channels)

Septum primum and then septum secundum separate atria
-f ovale normal foetal defect in this septum

During 5th work, common truncus divided by spiral septum, creating separate outflow tracts

NCC contribute lengthening of outflow tract and endocardial cushion formation

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29
Q

What is the difference between cyanotic and acyanotic CHD

A

Cyanotic
-R –> L shunt

Acyanotic
- L —> R

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30
Q

What is the function of the foramen ovale

A

Bypass the pulmonary circulation

If it remains patent –> Pulmonary HTN

31
Q

What is an association of situs inversus

A

CHD

Primary ciliary dyskinesia

32
Q

Why are SSRIs associated with laterality abnormalities

A

serotonin establishes left sidedness

33
Q

What are some RF for CHD

A 
Syndromes e.g. Edwards
Genetic
Rubella
Thalidomide
Accutane
Alcohol
34
Q

What is the incidence of ASD

A
  1. 4/10,000

2: 1 Female:Male

35
Q

What is the incidence of VSD

A

12/10,000

80% occur in the muscular septum

36
Q

What is the difference between muscular and membranous defects?

A

Membranous VSDs

  • More serious defects
  • Associated w/ abnormalities partitioning conotruncal regions e.g. teratology
37
Q

What is Eisenmenger’s

A

Most commonly due to septal defect

Pulmonary resistance becomes so great that the shunt changes direction to R –> L i.e. right hypertrophy secondary to LR shunt

38
Q

What is common truncus arteriosus

A

Conotruncal ridges fail to form
Defective interventricular septum

Pulmonary hypertension and bilateral ventricular hypertrophy

Associated with DiGeorge syndrome

39
Q

Why might an infant with common truncus have craniofacial malformation

A

NCCs migrate to truncus

Defective NCC form outer of pharyngeal arches

40
Q

What is transposition of the great vessels

A

Conotruncal septum fails to form spirally, runs straight down

Right sided aorta
Left sided pulmonary artery

41
Q

What are the abnormalities associated w/ tetralogy of fallot

A

VSD
Pulmonary valve stenosis
LV hypertrophy
Overriding aorta

42
Q

What are the symptoms of tetralogy

A 
Cyanosis
Dyspnoea
Syncope
Clubbing
Poor weight gain
Prolonged crying
43
Q

What is coarctation

A 
Narrowing of the descending aorta
Infants:
Pallor
Dyspnoea
Difficulty feeding

Left untreated may progress to fatal heart failure

44
Q

When does gastrulation take place, what are the crucial events?

A

Formation of trilaminar disc in 3rd week

1) Invagination
- of primitive streak - cephalic end = primitve node
- epiblast invaginates
- cells migrate toward primitive streak
- movement controlled by FGF8

2) epiblast cells move through streak
- displace hypoblast, creating embryonic embyroderm and mesoderm
- cells remaining in epiblast –> ectoderm

Epiblast cells migrate to pass on each side of the pre-chordal plate - plate forms between tip of notochord and oropharyngeal mmbr

45
Q

What is caudal dysgenesis, what are its symptoms, what are its associations

A

Insufficient mesoderm is formed in caudalmost region of embryo

This mesoderm contributes to formation of the lower limbs, urogenital system, lumbosacral vertebrae

Hypoplasia and fusion of lower limbs 
Vertebral abnormalities
Renal agenesis
Imperforate anus
Anomalies of the genital organs

maternal diabetes

46
Q

What is the vitelline duct

A

Communication between the midgut and the yolk sac

47
Q

Define the formation of the gut tube

A

Lateral body walls will close to form the body wall, with only a communication to the yolk sac via the vitelline duct

48
Q

What is the oropharyngeal membrane

A

ectodermal-endodermal membrane

Separates stomadeum (primitive oral cavity - ectoderm derived) from pharynx (endoderm derived)

Ruptures in the fourth week

49
Q

What is the cloaca membrane

A

The hindgut temporarily terminates at ecto-endo mmbr

Separate upper anal canal from lower part (proctodeum)

Mmbr breaks in the 7th week

50
Q

When are major organ systems formed

A

3rd to 8th week

  • a critical period for normal development
  • time when most gross structural defects are induced
  • 3rd and 4th week particularly vulnerable

Stem cell populations are establishing the organ primordia, interactions sensitive to insult

51
Q

When does the gut tube begin to form

A

3rd and 4th week

-same time as neurulation

52
Q

What connects neural tube and gut tube

A

Mesoderm

  • lateral plate components also splits into visceral and parietal layers
  • visceral later rolls up and is intimately associated with gut tube
53
Q

What is the paraxial mesoderm

A

Forms at the end of the third week from intraembyronic mesoderm

Forms somitomeres and somites

54
Q

How is the diaphragm formed

A

Communication of pleural space and abdo via pericardia-peritoneal canal

Pleuroperitoneal folds appear beginning fifth week

Fuse with septum transversum and oesophagus mesentry (7th week)

55
Q

How common are diaphragmatic hernias and what are the complications

A

1/2000

Due to failure of pleuroperitoneal mmbr to close the pericardioperitoneal canals

Peritoneal and pleural cavities are continous along the posterior body wall

Abdo viscera enter pleural cavity (85-90% left sided)

Push heart anteriorly and compress the lungs

Lungs may become hypoplastic
-high mortality (75%)

56
Q

Where is a conceptus supposed to implant

A

anterior or posterior wall of uterine cavity

57
Q

How does the mirena coil work

A

Thickens cervical mucus, preventing sperm entry

58
Q

How does the copper coil work

A

Inhibits attachment of fertilised egg

Helps prevent passage of sperm

59
Q

How do you investigate and manage a suspected ectopic

A

Urine pregnancy test
Transvaginal USS

Mx

  • methotrexate
  • Surgery - salpingectomy, saplingotomy
60
Q

Why does endometriosis increase risk of subfertility and ectopic

A

Inflammation at site of ectopic endometrial tissue

Adhesions

61
Q

What are some male causes of subfertility

A 
CF
Lack of vas deferens 
Impotence
Decreased sperm count
Varicocoele
ED
Anabolic
62
Q

What are some female causes of subfertility

A 
Fibroids
Abnormal shaped uterus
PCOS
Endometriosis
Ageing
63
Q

Why does the foramen ovale close

A

Lungs inflate
Pulmonary resistance decreases
LA pressure increases
foramen ovale valve pressed against septum secundum
Foramen ovale obliterates –> Fossa ovalis

64
Q

What symptoms may a ASD cause

A

Right side hypertrophy
Atrial fibrillation in older patient
Eisenmenger’s
Valve regurgitation

65
Q

What is the result of a VSD

A

Dependent on size
Pulmonary ciculation can be 1.2 -1.7 x aorta due to LR shunt
Right sided hypertrophy –> heart failure
Pulmonary HTN –> Eisenmenger’s

66
Q

What are the symptoms of tetralogy and its incidence

A 
9.6/10,000
Cyanosis
SOB
FTT
Syncope
CLubbing 
Fatigue
Heart murmur

Tet spells
-sudden cyanosis after crying, feeding, agitation

67
Q

What complication may you get in coarctation

A

Dilated internal thoracic arteries

68
Q

What is the incidence of coarctation

A

3.2/10,000

69
Q

What is the distinction in coarctation

A

Preductal - PDA

Postductal - Obliteration of DA

70
Q

what are the signs of post ductal coarctation

A

Right arm HTN

Decreased BP lower limbs

71
Q

What is arhinencephaly

A

Failure of olfactory tract to form

Midline fused lateral ventricle

72
Q

What are the key signalling factors for heart development

A

Signals from endoderm induces cells in primary heart field to form myoblasts

BMP2/4 upregulated

Endoderm blocks WNT protein synthesis (WNT proteins inhibit heart development)

Expression of BMP and inhibition of WNT allows expression of NKX2.5
(master gene for heart development)

73
Q

What are the key molecules in establishing laterality

A

5HT
PITX2 expressed on left

(retinoic acid specifies caudal structures)

74
Q

Situs invertus totalis incidence?

A

1/10,000

BSc Embryology (7 decks)

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