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YR2: Reproduction, Ageing and Development > Embryology > Flashcards

Embryology Flashcards

1
Q

Recall the 4 cellular processes at work in embryological development

A

Proliferation: of epiblast cells
Differentiation: of epiblast cells to form mesoderm cells
Reorganisation: Mesoderm cells move into space between epiblast + hypoblast. Differentiate further to generate the endoderm, which replaces the hypoblast
Apoptosis: Loss of hypoblast cells due to replacement by endoderm

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2
Q

Recall the 3 stages of renal development in utero

A

Pronephros
Mesonephros
Metanephros

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3
Q

What is significant about the mesonephros pre-kidney structure?

A

Site of mesonephric + paramesonephric ducts development, that eventually differentiate into genital ducts

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4
Q

Describe the arterial supply to the kidneys during embryonic development

A

Has to form, degenerate + reform as kidneys move up abdomen

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5
Q

Where do the gonads originate from embryologically?

A

Intermediate mesoderm within urogenital ridges

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6
Q

What do mesonephric and paramesonephric ducts give rise to?

A 
Mesonephric = Male genital ducts (Wolffian system) 
Paramesonephric = Female genital ducts (Mullerian system)
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7
Q

What influences differentiation of reproductive tracts after week 7 of development?

A

Presence or absence of SRY
+ : Male
- : Female

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8
Q

What do the leydig and sertolli cells produce during male development?

A

Leydig: Testosterone (DHT), under stimulation of maternal hCG. Supports development of Wolffian ducts.
Sertolli: anti-Mullerian hormone (AMH), which causes regression of Mullerian (paramesonephric) ducts.

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9
Q

In male embryos, what are the most common mal-developments a result of?

A

Inability to produce appropriate hormones (testosterone + AMH)
Inability of target tissues to respond to these hormones, normally due to defects in the cognate receptors.

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10
Q

Where does heart development begin?

A

Outside the embryo proper, in a horseshoe pattern

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11
Q

What happens at day 21 of heart development? What events occur after this?

A

2 tubes of horseshoe fuse to produce a single tube which can pump blood unidirectionally
Looping of heart + separation, giving rise to 4 chambered structure
Development of valves

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12
Q

Where is the foramen ovale located?

A

Between atria

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13
Q

What does the foramen ovale bypass in the foetus?

A

Right ventricle + therefore pulmonary circulation

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14
Q

What is the purpose of ductus arteriosus?

A

Connects main artery from right ventricle to aorta, diverting blood that would normally go to lungs to arterial system

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15
Q

What is the Tetralogy of Fallot?

A 
4 structural abnormalities within the heart 
Pulmonary stenosis
RV thickening
Ventricular septal defect
Aorta overides septal defect
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16
Q

How does transposition of the great arteries cause major issues?

A

Aorta is connected to RV + pulmonary artery to LV
Generates 2 separate blood flows; oxygenated blood is cycled through the left via the lungs; de-oxygenated blood through the right to the body.
Closure of foramen oval + ductus arteriosus at birth separates the blood flows
Infant becomes cyanotic
Treatment: prostaglandins to keep ductus arteriosus open, + perhaps opening of a link between the atria.

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17
Q

When does lung production of surfactant begin? What does low levels result in? What can increase and accelerate production if preterm delivery is delayed?

A

Early in 3rd trimester
Low levels causes Respiratory Distress Syndrome
Glucocorticoids can increase + accelerate production

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18
Q

What is a genetic mosaicism?

A

Meiotic non-disjunction causing different cells within the body to have non-identical genetic makeup

19
Q

What is the most likely cause of spina bifida?

A

Folic acid deficiency

20
Q

How does surgery effect spina bifida?

A

Can address anatomical problems to protect neural tissue

Can’t address functional problems; thus nerve damage results

21
Q

When does the malformation occur in spina bifida and what is the problem?

A

~3 weeks

Incomplete fusion of the neural tube

22
Q

What is a cleft palate?

A

Connection between the mouth+ nasal cavity

23
Q

Recall 4 infectious agents that are common teratogens

A

Rubella
Syphilllis
HIV
HSV

24
Q

What is ancephaly?

A

Compromised development of the head + skull

Similar aetiology to spina bifida, though results in a lack of closure of the anterior neuropore.

25
Q

What are the 3 germ layers precursors of?

A 
Endoderm = gut, liver + lungs
Mesoderm= skeleton, muscle, kidney, heart + blood.
Ectoderm = skin + CNS
26
Q

List 3 developmental abnormalities of the kidneys

A
  1. If retained in pelvis, rather than moving to abdomen
  2. Retention of an extra artery may obstruct the ureter + cause enlargement of the renal pelvis.
  3. Form separately, but may fuse to form a horseshoe; the extra tissue makes it impossible to move, so remains in the pelvis.
27
Q

Give an example of male genital Mal-development

A 
Androgen Insensitivity Syndrome 
Mutant androgen receptor
No virilisation of external genitalia 
Internally lack Woolfian ducts 
AMH production is normal so no female structures
28
Q

Give an example of female genital Mal-development

A

Congential Adrenal Hyperplasia
Mutation in CYP450 21-hydroxylase enzyme, limiting cortisol production from fetal adrenals
Lack of cortisol means theres no negative feedback on pituitary ACTH output, causes high ACTH, + over-stimulation of fetal adrenals, which make weak androgens. These cause partial virilisation of genitalia.
Internal systems are female, as there is no SRY
Female ducts develop (no AMH, as no Sertoli cells).

29
Q

When are the terms conceptus, embryo, fetus and infant used?

A

Conceptus: everything resulting from the fertilised egg
Embryo: up to week 8 of development
Fetus: rest of pregnancy
Infant: after delivery.

30
Q

Summarise the key developmental events occurring in the first 2 months of pregnancy, week by week

A

2: Development of bilaminar disc
3: Formation of trilaminar disc (mesoderm), CNS + somites. Blood vessel initiation. Formation of placental villi. (3mm).
4: Closure of neural tube. Heart, Face, arm initiated. Umbilical cord. Elaboration of placental villi. (4mm)
5: Face + limbs continue. (5-8mm)
6: Face, ears, hands, feet, liver, bladder, gut, pancreas. (10-14mm)
7: Face, ears, fingers, toes. (17-22mm)
8: Lungs, liver, kidneys, (28-30mm)

31
Q

Development of which structures continues beyond week 8?

A

Face
Lungs
Urinary + reproductive systems

32
Q

What are the primary processes occurring in the second and third trimester?

A

Growth + Maturation

increased size + remodelling

33
Q

In what pattern do primary structures of the face develop? How long does this pattern persist? How long does it take for this to change?

A

On the side of the head
Persists until at least 5 weeks post-fertilisation
Move over the next 5 weeks to expected position through tissues of the developing face

34
Q

Describe the process of movement of pre-formed structures through the face

A

Repeated formation of clefts + filling in of the clefts leads to sequential loss of tissue from centre of the face + movement of tissues to correct places

35
Q

What does the formation of the face from 2 separated halves result in if the process goes wrong?

A

Clefting in the lip or palate

36
Q

Describe the usual appearance of cleft lip and cleft palate

A

Cleft lip: asymmetric, as only 1 of the 2 clefts does not function correctly
Cleft palate: symmetric as the halves of the palate don’t meet + fuse correctly

37
Q

Why is there usually little or no scarring after cleft correction surgery?

A

Rapid cell turnover in infants

38
Q

What 4 steps occur in heart development?

A

Folding of embryo + heart tube fusion
Heart looping
Septation
Outflow tracts divide

39
Q

What should happen to the ductus arteriosus and foramen oval at birth?

A

They should close, allowing oxygenation within the lungs

40
Q

What is polydactyly? What is Oligodactyly?

A

Polydactyly: > 5 digits per hand/ foot
Oligodactyly: Loss of digits

41
Q

What was Thalidomide marketed as? What did its use from 8 weeks of pregnancy cause?

A

Anti-morning sickness drug
Interfered with blood vessel development in developing limb bud, leading to cell death + inhibition of growth
Particularly effects upper limbs

42
Q

In which conditions is Thalidomide currently used therapeutically?

A

Some cancers + leprosy

43
Q

What is the mechanism of action of Thalidomide?

A

Damages developing blood vessels, thus depriving adjacent cells of nutrients + preventing proper growth + development.

44
Q

What are Teratogens?

A

Factors affecting details of development, though primary structures will be present

YR2: Reproduction, Ageing and Development (9 decks)

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