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Missed Lectures > abnormalities of human development > Flashcards

abnormalities of human development Flashcards

1
Q

What causes mal-development

A

30% genetic
Environmental – 15%
Multifactorial – 55%

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2
Q

How are identical twins formed

A

Identical twins / triplets: one conceptus forms 2 / 3 inner cells masses to form 2 / 3 genetically identical individuals

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3
Q

How is a chimera formed

A

Chimerism: 2 genetically distinct conceptuses combine to form one individual

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4
Q

What is mosaicisim

A

Mosaicism (non disjunction) – differences between cells within one individual

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5
Q

Give an example of mosaicism

A

Type of Down’s syndrome or heterochromia

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6
Q

Which chomoasome is eye colour on?

A

15

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7
Q

When does differentiation of eye colour occur

A

day 22 pf

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8
Q

What does mutation in the KITr gene cause

A

Piebaldism

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9
Q

What is the manifestation of Holt-Oram syndrome

A

Heart defects and triphalengeal thumb

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10
Q

What causes achondroaplasia

A

Chr 3 gain in FGFR3 function

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11
Q

After how many weeks is the conceptus a foetus

A

8

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12
Q

when does pre-implantation take place

A

over 6 days

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13
Q

what is a morula

A

ball of undifferentiated cells

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14
Q

whats a blastocyst

A

structure that has an outer layer of trophectoderm, an inner cell mass, and a fluid-filled cavity.

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15
Q

when does implantation occur

A

10 days post fertilisation

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16
Q

what does the inner cell mass become

A

bilayer disk, composed of hypoblast and epiblast cells

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17
Q

what is gastrulation

A

converts the bilayer of hypoblast and epiblast cells into a trilaminar embryo, containing the three layers of Germ Cells (Ectoderm, Mesoderm and Endoderm), occurring during days 14-18 postfertilisation.

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18
Q

what does the ectoderm give rise to

A

skin and the central nervous system

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19
Q

What does the mesoderm give rise to

A

muscles, blood, skeleton, heart and kidney

20
Q

What does the endoderm give rise to

A

gut, lungs and liver

21
Q

when have precursors for all internal tissues been laid down

A

week 4

22
Q

what develops in weeks 5-8

A

mostly the elaboration of the tissues generated during the early weeks

23
Q

How does thalidomide cause birth defects

A

affects growth of blood vessels, depriving cells of nutrients, and ability to grow. 8 weeks = arm deformation

24
Q

name the stages of kidney development

A

Pronephros is the most immature form of kidney
Mesonephros, an intermediate phase
Metanephros is most developed and persists as the definitive adult kidney.

25
Q

When do gonads show sign of differentiation

A

7 weeks

26
Q

What gives rise to male genital ducts

A

mesonephric ducts

27
Q

What gives rise to female genital ducts

A

paramesonephric ducts

28
Q

Describe relationship of developing kidney with ureters and arteries

A

ureters change length, and grow with kidney, arteries break down and re-form during this process.

29
Q

Name some kidney mal-developments

A

Pelvic kidney, horseshoe kidney, enlarged renal pelvis

30
Q

when are meso and paramesonephric pathways developed

A

week 5

31
Q

where does gonadal precursor develop

A

mesonephric mesoderm

32
Q

What is the role of the primordial germ cell in gondal development

A

give rise to the gametes within the gonads

33
Q

What is the pathway of the primordial germ cell

A

hey originate in the epiblast, but then migrate to the caudal part of the yolk sac (Figure 5.4.5A). Once the main caudal structures of the embryo proper have developed, the PGC migrate through the hind-gut and dorsal mesentery to the mesonephros and thence to the developing gonads.

34
Q

What is a key regulator of male devlopment

A

testosterone from lyedig cells under regulation of maternal Hcg

35
Q

What causes regression of paramesonephric ducts in males

A

sertoli cells produce anti-Mullerian hormone,

36
Q

What is a common cause of male mal-development

A

inability to produce the appropriate hormones (testosterone and anti-Mullerian hormone (AMH) or (b) the inability of target tissues to respond to these hormones, normally the result of defects in the cognate receptors

37
Q

What is Androgen Insensitvity syndrome

A

mutant androgen receptor. There is no or limited virilisation of external genitalia (which show relatively normal female structures). No mesonephric ducts, non descended testis, but no Mullerian duct because sertoli and AMH is normal.

38
Q

What is CAH

A

21-hydroxylase enzyme (CYP 21A2), so cortisol production from the fetal adrenal is very limited as this enzyme is key in cortisol synthesis.
High ACTH leads to androgen production, virilisation of female

39
Q

Describe heart development

A

cardiogenic cells develop in a U (or horseshoe) pattern outside the embryo proper. These form a pair of heart tubes, which fuse to form a single heart tube by ~21 days post-fertilisation. This tube is already able to pump blood unidirectionally.

Looping of the heart and septation give rise to the 4-chambered structure of the normal human heart. During this process the vascular connections are maintained, so that the major veins are connected to the atria, and major arteries to the ventricles. Valves develop, to ensure that blood flows unidirectionally within the heart.

40
Q

Describe foetal heart differences

A

formamen ovale and ductus arteriousus

41
Q

Describe implications of the RV Aorta, LV PA issue

A

The aorta is connected to the right ventricle, and the pulmonary artery to the left ventricle. This generates two separate blood flows; oxygenated blood is cycled through the left side of the heart via the lungs; de-oxygenated blood through the right side of the heart to the rest of the body. Before birth, this does not matter, as the foreman ovale and ductus arteriosus allow mixing of the blood flows sufficiently to sustain fetal growth and development. The closure of these connections after delivery separates the blood flows, so the infant becomes cyanotic (‘blue baby syndrome’). Immediate treatment may involve administering prostaglandins to keep the ductus arteriosus open, and perhaps opening of a link between the atria. Definitive treatment would usually involve the switching of the two arteries, to restore the normal blood flows.

42
Q

How is spina bifida prevented

A

3 months pre-conception folate

43
Q

Describe the process of lung developmetn

A 
embryonic 3-8 weeks
pseudoglandular 5-18 week
cannalicular 16-20 weeks
saccular 24-36 weeks
alveolar 36->
44
Q

When is surfactant produced

A

3rd trimester

45
Q

what is an issue with pre-term babies

A

(Respiratory Distress Syndrome, RDS)

Missed Lectures (5 decks)

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