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RDA > Abnormalities of human development/embryology > Flashcards

Abnormalities of human development/embryology Flashcards

1
Q

What are causes of mal-development?

A

Genetic
Environmental
Multi-factorial

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2
Q

What is chimersim?

A

Two genetically diffrent cells that join to make an organism.

FUSED MULTIPLE ZYGOTES.

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3
Q

What is mosaicism?

A

Differences between cells within one individual.

Patches will be identical and patches will be different chromosomal make up.

examples - differently coloured eyes, calico cats.

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4
Q

Why can eye colour show mosaicism?

A

On human chromosome 15

Brown most common colour - other colours found in caucasians.

It will usually form before day 22.

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5
Q

What are different chromosomal problems?

A

too many- kleinfelters - an extra x gene (decrease fertility. One x will be inactivated and it will not inactivate the others)

  • –>Autosomal (down’s syndrome, edwards and pataus)
  • —> Can be mosaic or partial which has less serve side effects

too few - Turner’s syndrome (X0, female, short stature, infertile)

translocations - can have genetic material swapped.

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6
Q

What is ACHONDROPLASIA?

A

Gain of function mutation in FGFR3

  • Achondroplasia means “lack of cartilage”
  • Defect is in conversion of cartilage to bone
  • There is a lack of bone growth
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7
Q

What is a birth defect?

A

congenital malformation = congenital abnormality

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8
Q

What does teratology?

A

like a dysmorphology.

A teratogen = any agent that can distrub the development of any embryo or fetus.

CAN BE: infectious agents, physical agents, chemical agents

Major impacts early in pregnancy but they are very tissue specific.

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9
Q

What are the key features and mal-developments that can occur in the main systems?

A

Extra digit - polydactyly (person had six digital rays (starting point))
Spina bifida - not just lower back
cleft lip and palate
Thalidomide - loss of limbs

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10
Q

How do limbs development?

A

4-8 weeks post fertilisation

Starts off with the flat hand plate and then digital rays form. Will then differentiate to give the fingers and the thumb.

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11
Q

what are the 4 simple process which underlie all embryology?

A

Proliferation

Movement (chemotaxsis)

Differentiation

Loss (apoptosis)

In a mature cell this happens one at a time but in an embryonic one this can be 3 at a time.

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12
Q

How are the processes regulated?

A

Autocrine

paracrine

change in receptors (up regulation or down regulation)

spatial

temporal

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13
Q

what happens during pre-implantation development?

A

there is cleavage forming the 2,4,8 cell conceptus

Day 0-6

cleavage –> morula –> blastocyst

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14
Q

what happens on morula (day 4)?

A

there is compaction and differentiation.

inner cells differ from those on the outside

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15
Q

when does a blastocyst form?

A

5-6 days.

Morula –> balstocyst

It has an outer trophectoderm layer (forms the placenta) and an inner cell mass (form the embryo)

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16
Q

where does fertilisation occur?

A

in the ampulla of the uterine tube.

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17
Q

what happens at implantation?

A

Day 6-10

hatching of the blastocyst to remove the zona pellucida

blastocyst begins to implant into the uterine lining

the inner cell mass becomes a bi-layer –> epiblast and hypoblast

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18
Q

where are areas that can cause the mother harm if they implant here?

A

fallopian tube

ovary

intraperotineal space

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19
Q

what happens in gastrulation?

A

day 14-18

formation of trilaminar disc from the bilayer (mesoderm, endoderm, ectoderm)

proliferation of the epiblast

differentiation of the mesoderm cells

moves into the space between the epiblast and the hypoblast

mesoderm cells then replace the hypoblast cells

hypoblast cells will undergo apoptosis

mesoderm differentiate into endoderm

the epiblast differentiates into the ectoderm

20
Q

what is neurulation?

A

the diffrentiation of the ectoderm to form the CNS.

Happens up to 4 weeks and is controlled by the notochord.

formation of the neural plate and development of the neural folds which leads to an increase in size.

21
Q

what does spina bifida arise from and how is it avoided/treated?

A

a failure of neuralation.

give folic acid to the mother

22
Q

what happens after neuralation?

A

outside the embryo proper - cardiac and vascular progenitors in the primary heart field at the cranial end of the embryo

ectoderm at the caudal end of the embryo

folding of the embryo

23
Q

describe the kidney development:

A

three phases:

starts at the urogenital ridge and is complete by 8 weeks

Pronephros - immature form of the kidney –> degenerates and is removed

Mesonephros - intermediate phase –> degenerates + removed

metanephros - final form(ureters, calcyce, renal pelcis+ collecting ducts there is fusion of the collecting ducts and nehphrons (from uretic ridge at 5 weeks )

kidney migrates as the embryo increases in length.

24
Q

Describe gonadal development:

A

arises from intermediate mesoderm with the urogenital ridges of the embryo

genital ducts arise from paired mesonephric/Woffian (give rise to males) and paramesonephric/mullerian ducts (give rise to females).

IT IS DEPENDANT ON THE PRESENCE OR ABSENCES OF SRY. SRY + = mesonephric pathway at 3 weeks.

SRY- = paramesonpehric at 8/9 weeks

they show no differentiation till about 7 weeks.

25
Q

what is essential for the development of the male reproductive system?

A

At 7 weeks development will begin just before the peak of hcG as this is needed to produce LH for tetosterone –> leads to development of epididymis, vas deferns, seminal vesicle + ejaculatory duct.

DHT is needed to form the prostate gland , penis and scrotum.

steroli cells produce anti-mullerian hormone which causes regression of the paramesonephric ducts (as these give rise to female reproductive tracts)

26
Q

what are errors in the male reproductive system called and caused by?

A

inability to produce AMH or testosterone

OR

inability of the target organs to react to the hormones

e.g. androgen insensitivity syndrome - leads to virilised genitalia. These males lack a mesonephric duct.

absence of AMH - will have both male and female sex organs as there is no regression of the paramesonephric tract.

undescended testes - very common and will often occur in the first year of life.

hypospadies - this is when there is incomplete fusion of the urtheral fold and so this can occur anywhere along the urtheral groove.

CAH

27
Q

what is congenital adrenal hyperplasia?

A

mutation in 21 beta hydroxylase which leads to an increase in ACTH –> stimulates the adrenals to form sex steroids.

This forms a weak androgen and the women do not have very clear genitalia.

They have no AMH but do have paramesonephric ducts.

28
Q

what are the key events in cardiac development?

A

folding of the embryo

heart tube fusion

heart looping

septation

the heart will form at the head of the embryo in the cardiogenic area. this will form a horseshoe shape from which two tubes will form. after this there will be fusion of these two tubes which leads to a single tube which allows unidrectional blood flow.

there is then folding (due to the pressure from the atria forming the s shape of the heart) and septation which forms the 4 chambers of the heart.

29
Q

what is the purpose of the foramen ovale?

A

allows blood through the heart that is oxygenated to flow between the two atrias.

from this the blood will flow into the left ventricle and around the body.

30
Q

what is the purpose of the ductus arteriosus?

A

this connects the aorta to the artery leaving the right ventricle allowing blood that would usually go from the lungs into the rest of the arterial system.

ductus arteriosus and the foramen ovale should close after birth.

31
Q

what causes ancephaly?

A

this is closure of the anterior neuropore. It is thought to be linked to a lack of folic acid.

32
Q

why do clefts occur and how does the face develop?

A

unkown causes but the repeated formation and filling of the clefts leads to loss of tissue from the centre of the face.

usually asymmetrical in cleft lip but symmetrical in cleft palate as two halves do not meet and fuse properly.

FACE DEVELOPS AS TWO HALVES from either side of the head a five weeks. structures will then move from the side to the appropriate positions.

33
Q

what is respiratory distress syndrome?

A

this is resp failure due to a lack of surfactant that is usually formed in the third trimester.

surfactant is needed to reduce surface tension in the alveloi.

this is seen in premature infants –> can be treated with an injection of glucocorticoids in the mother as this increases the production in the infant.

34
Q

what are the five stages in lung development?

A

embryonic

pseudoglandular

canilcular

saccular

alveolar.

35
Q

what are possible heart defects?

A

hypoplasia- under development

obstruction defects - pulmonary stenosis (the heart must work harder to pump the blood to the lungs)

septal defects - ventricular septal defects (oxygenated and deoxygenated blood mix between the ventricles)

cyanotic defects

36
Q

Describe limb development?

A

proliferation

apoptosis

differentiation

limb bud–> hand/foot plates –> digits

37
Q

why did thalidomide cause limb maldevelopments?

A

it is a teratogen and so damages developing blood vessels during limb development at around 8 weeks.

38
Q

what are different teratogens?

A

TERATOGENS = ANYTHING THAT CAN EFFECT THE EMBRYO DEVELOPMENT IN UTERO. usually most detrimental during organogenesis (the 1st trimester)

Drugs/ chemical:
alcohol
phenytoin 
tetracycline
excess hormones

infectious:
rubella
cmv
varicella

physical agents:
ionising radiation

39
Q

what is polydactly?

A

extra digits

webbing can occur

limbs form from the lateral plate

40
Q

what are possible defects in the formation of the kidneys?

A

pelvic kidneys - when the kidneys fail to descend to their position in the abdomen - will be unnoticed until there are complications.

horseshoe kidneys - when the kidneys fuse below the inferior mesenteric artery. this will lead to increased obstruction + infection of the ureters.

retention of an extra artery - this will lead to obstruction and enlargement of the renal pelvis.

41
Q

how do the male gonad descend?

A

develop in the lumbar region and are attached to the anterior by the gubernaculum.

the gubernaculum will contract and pull the testses through the pelvic inlet and inguinal canal into the scrotum.

42
Q

how does the female reproductive tract form?

A

the absence of testosterone means that there is regression of the mesonpehric ducts.

the absence of AMH means the paramesonephric ducts form to give rise to the uterus, Fallopian tubes and the upper 1/3 of the vagina.

the bottom of the paramesonephric ducts will fuse to give the uterus and the un-fused top will give rise to the fallopian tubes.

the urogenital sinus gives rise to the bulbourtheral gland and the lower 2/3rds of the vagina.

43
Q

describe foetal circulation?

A

there is blood flow from the placenta to the embryo via the umbilical cord.

the blood is diverted to the IVC by the ductus venosus.

the blood will move into the right atrium –> into the left atrium via the foramen ovale.

some of the blood will go to the right ventricle and this is then pumped out via the pulmonary artery. this the ductus arteriosus which allows blood to flow into the aorta and around the body.

this circulation allows the bypassing of the lungs in the embryo.

44
Q

what is great artery transposition?

A

this is when the aorta is connected to the right side of the heart and the pulmonary artery to the left.

this has no issues before delivery as the foramen ovales allows the mixing of blood.

however after birth these holes close and the foetus has deoxygneated blood being pumped around the body –> this will cause cyanosis (baby will turn blue)

this is treated with prostaglandins which keeps the holes open until the arteries can be switched around in surgery

45
Q

what does ectoderm form?

A

CNS and skin

46
Q

what does mesoderm form?

A

heart, kidney, skeletal muscles, blood + muscle

47
Q

what does endoderm form?

A

liver, lungs and GI tract.

RDA (7 decks)

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