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Anatomical sciences > Embryology and congenital malformations > Flashcards

Embryology and congenital malformations Flashcards

1
Q

why study human embryology ?

A

history of prenatal origin understand brith defects and cogenital abnormalities
understand adult anatomy
obstetrics and paediatrics specialities
understand adult illness or diseased with developmental origin
reproductive technologies
advise patients - issues with reproduction, birth defects, parental development, in vitro fertilisation, stem cells and cloning

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2
Q

trimesters

A

1st, 2nd, 3rd
3 month periods in 9 months

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3
Q

Pre-embryonic period

A

Fertilisation of the egg of the 3rd development with implantation of the conceptus

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4
Q

embryonic period

A

period of organogenesis
from the beginning of 4th week to end of 8th week of development - where the germ layers (Ectoderm, Mesoderm and Endoderm) are formed and they give rise to specific tissues and organs

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5
Q

end of embryonic period

A

main organ system have been established
(embryonic period = can include the pre-embryonic - first 8 weeks following ovulation and fertilisation resulting in pregancy)

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6
Q

period of the foetus/ feral period

A

3rd month to birth - period of maturation of embryonic organ systems and tissues

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7
Q

gametogenesis

A

The process of the production of male and female gametes or sex cells (sperm and oocyte or egg) from the primordial germ cells (PGCs) via meiotic cell division in the gonads (testes and ovaries)

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8
Q

spermatogenesis stems

A

Primordial germ cell in embryo
spermatogonial stem cell
spermatogonium
primary spermatocyte
(meiosis 1)
secondary spermatocyte
(meiosis II)
early spermatid
(cell differentiation)
sperm

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9
Q

Sertoli cells

A

provide nutrients

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10
Q

oogenesis steps

A

primordial germ cell
oogonium
primary oocyte (present at birth - arrested in prophase of meiosis I)
(complete meiosis I and onset of meiosis II)
secondary oocyte (arrested at metaphase of meiosis II)
(ovulation / sperm entry)
(complete meiosis II)
fertilised egg

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11
Q

primordial germ cells

A

specialised stem cells - give rise to germ line and are formed a generation earlier when the parents were embryos - handed over reproductive ability by parents before you were born

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12
Q

principles of gametogenesis for development of human body structure

A
  • gametogenesis reduced the chromosomal number of the gametes from a diploid (46) to haploid (23)
  • gametogenesis results to an enhanced genetic variability in the gametes through a random recombination of genetic material on homologous maternal and paternal chromosomes
  • spermatogenesis does not start in the male until puberty and occurs in seminiferous tubules of the testes
  • oogenesis starts from feel life in the female - occurs in the ovary and completed at puberty
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13
Q

errors in gametogenesis

A

chromosomal abnormalities could result in birth defects or spontaneous abortions

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14
Q

errors in spermatogenesis

A

lead to number of spermatozoa morphological abnormalities that could affect male fertility = sperm count clinical investigation

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15
Q

fertilisation

A

male and female gametes fuse = form a zygote

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16
Q

where does fertilisation occur

A

ampullarf region of uterine tube (oviduct)

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17
Q

capacitation

A

sperm conditioning process within the female reproductive tract (uterine tube) in prep for fertilisation for fertilisation of the ovum
only capacitated sperm can pass through cells and undergo acrosome reaction

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18
Q

acrosome reaction is induced by what

A

zona proteins
after binding of the acrosomal region of the sperm with the zone pellucida of the oocyte
leads to release of enzymes needed to penetrate the zone pellucida

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19
Q

when do cortical and zone reactions happen

A

after release of acrosome enzymes (across)

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20
Q

what is the cortical reaction

A

sperm can penetrate the zone pellucida
sperms contact with plasma membrane of the oocyte leads to release of lysosomal enzymes form cortical granules in the plasma membrane = become impenetrable to other permatozoe

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21
Q

what is the zona reaction

A

changed in permeability of the zona pellucida
the enzymes alter the properties including structure and composition of the zona pellucida to prevent polyspermy

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22
Q

what is the purpose of cortical and zona reactions

A

to ensure only one sperm penetrates the egg

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23
Q

what could male infertility be due to

A

could result from the quality and quantity of spermatozoa ejaculated

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24
Q

when does cleavage occur

A

1 week after fertilisation

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25
Q

what is cell cleavage

A

rapid mitotic divisions of the large zygote to produce an increase in numbers of smaller daughter cells - blastomeres

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26
Q

does cleavage result in cell growth

A

no there is no increase in protoplasmic mass
egg remains 1 - more divisions so proportions become smaller

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27
Q

what increases after cleavage

A

the nucleocytoplasmic ratio increases after cleavage - as cytoplasm is partitioned - smaller cells

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28
Q

what does cleaver transform the zygote into

A

multicellular embryo = morula from single large cell (zygote)
A solid ball of cells
12-16 cells
in about 3 days after fertilisation

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29
Q

Parthenogenesis

A

process where an unfertilised egg develops to a new individual

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30
Q

Parthenogenesis

A

process where an unfertilised egg develops to a new individual

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31
Q

Morula

A

A solid ball (mulberry) of 12-16 cells (blastomeres) following cleavage

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32
Q

Compaction

A

a process of cells (blastomeres) reorganisation and segregation into inner cell mass (embryo blast) and outer cell mass (trophoblast) following cleavage

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33
Q

what does compaction lead to

A

The establishment of inside-outside polarity and increased maximised cell-to-cell contact

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34
Q

Blastocyst stage

A

Stage when the morula developed a fluid filled cavity (Blastocoel) with a compact inner cell mass at one side (embryonic pole) enclosed by a thin, single layered epithelium of trophoblast

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35
Q

when does blastocyst happen

A

2nd week following fertilisation

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36
Q

what is an embryonic germ disc

A

Cluster of embryonic cells (inner cell mass - embryoblast) at the embryonic pole of the blastocyst that give rise to tissues of the embryo proper and constitutes the germ disc formed within the 2nd week

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37
Q

what is embryonic germ disc used for

A

placenta and other fatal membrane formations
after segregation of blastomeres
outer cell mass forms the trophoblast

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38
Q

what are the bilaminar embryonic germ disc layers

A

embryo blast (germ disc) differentiated into 2 layers
outer layer = epiblast
inner layer = hypoblast (primitive endoderm)

39
Q

role of bilaminar embryonic germ disc

A

· Defines the primitive dorsal-ventral axis of the embryo
· Epiblast = Dorsal
Hypoblast = Ventral

40
Q

stem cell

A

undifferentiated cell that has the ability to form specilised cell types
embryonic or adult stem cell

41
Q

pluripotent cell

A

has ability to form all mature cell types in the body except placental and extra embryonic cells
it can’t form a whole organism

42
Q

multipotent cell

A

has the ability to form more than one closely related mature cell types in the body but not as varied as pluripotent cells

43
Q

examples of multipotent cells

A

cord blood/bone marrow stem cells form erythrocyte, leucocyte, platelets

44
Q

totipotent cell

A

Have the ability to form all differentiated cell types in the body including the placental and extra embryonic membrane cells
it could form a whole organism
e.g zygotę and first few generations of blastomeres

45
Q

3 key events in human embryology

A
  • Gametogenesis
  • fertilisation
    -cleavage
46
Q

what is the primitive streak

A

a transient thickened longitudinal midline structure at the caudal end of the epiblast of the bilaminar embryonic germ disc

47
Q

when does primitive streak form

A

day 15 of developing human embryo

48
Q

what is a primitive groove

A

a narrow tough like depression with slightly bulging regions on either side on the primitive streak

49
Q

what is the primitive node

A

Cephalic (cranial) end is slightly elevated expanded area
surrounds a small circular depression called primitive pit that is continuous caudally with primitive groove

50
Q

what happens in gastrulation

A

Process of epiblastic cell movement (ingression or invagination) through primitive streak
leading to transformation of blaminar germ disc into trilaminar germ disc

51
Q

what layers are in a trilaminar germ disk

A

ectoderm
mesoderm
endoderm

52
Q

what cells form what layers in gastrulation and when

A

formation of the primitive streak (15th day)
- epiblastic cell ingress or invaginate to form the mesoderm and endoderm
- remaining epiblastic cells become the ectoderm

53
Q

goals of gastrulation

A
  • form the primitive streak
  • establish all major body axes in 4th week of development
  • cranio caudal axis
  • mediolateral axis
  • dorsoventral axis
  • left right axis
  • formation of embryonic body plan
54
Q

how are malformations such as caudal dysplasia,, caudal regression syndrome, sacral anagenesis and sireomlia caused

A

errors in gastrulation

55
Q

dextrocardia

A

when heart is on right side of body not left

56
Q

laterality and heart defects

A

disruption of the laterality pathway in specifying left and right sidedness in the progenitor heart cells causes many different types of heart defects:
- ventricular septal defects
- atrial septal defects
- double outlet right ventricle

57
Q

ectodermal germ layer

A

outside
organs and structures
enamel of teeth
oral and anal canal
sensory epithelium of ear, nose, eye

58
Q

what germ layer forms the neural tube

A

Induced to form the Neuroectoderm = formation of the neural tube (via nerulation)
Rise of neural crest cells and pituitary gland

59
Q

mesoderm is made up of what 3 parts

A

paraxial mesoderm
intermediate mesoderm
lateral plate mesoderm

60
Q

what are somitomeres

A

in paraxial mesoderm
segmental blocks (called neuromeres in head in association with neural plates)

61
Q

what is the mesenchyme

A

connective tissue in head

62
Q

what are somites

A

mature somitomeres
neck (occipital) region downwards = the somitomeres form segmented pair of blocks of mesoderm on either side of the developing neural tube

63
Q

when and where does the first pair of somites arise

A

ccipital region of the embryo at 20th day of development

64
Q

how many somites arise per day

A

New somites appear craniocaudally at the rate of about 3 pairs per day

65
Q

how many somites at the end tf the 5th week and where

A

At end of the 5th week - 42 to 44 pairs of somites formed
4 occipital, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 8-10 coccygeal pairs of somites

66
Q

how can you tell the age of an embryo

A

counting somites numbers during a period of development because somites are formed with specific periodicity
(1st pair = day 20, add 3 pairs extra each day)= somite age of the embryo

67
Q

intermediate mesoderm contributes to what structures

A

Contribute in the formation of the structures of the urogential system = primordial germ cells, gametes and gonads

68
Q

lateral plate mesoderm is divides what into 2 layers

A

parietal (somatic)
visceral (splanchnic)

69
Q

what does the parietal layer line

A

intraembryonic cavity walls

70
Q

mesoderm from parietal layer and ectoderm together form

A

-The lateral body wall
-The dermis of the skin in the body wall and limbs, bones and connective tissue of the limbs and sternum
-The costal cartilage, limb muscles and most of the body wall muscles
-The mesothelial or serous membranes (parietal layer) that line -The peritoneal, pleural and pericardial cavities and secrete serous fluid

71
Q

Mesoderm of the visceral layer and endoderm together form

A
  • wall of the gut tube
  • serous membrane (visceral layer) that surrounds organs
  • blood cells and blood vessels
72
Q

Endodermal Germ layer

A

inner layer
epithelial lining of respiratory tract, urinary bladder, urethra and auditory tube
pharynx

73
Q

walls of gut derived from

A

mesoderm

74
Q

how does gastrulation begin

A

formation of morphogenetic centre = primitive streak - day 15

75
Q

what does gastrulation involve

A

movement and migration of epiblastic cells
ingress (invaginate) through primitive streak
form mesodermal germ layers between epiblast and hypoblast

76
Q

what does formation of mesodermal germ cell layer lead to

A

transformation of the hypoblast into a endodermal germ cell layer and epiblast = ectodermal germ cell layer

77
Q

what does hypoblast become

A

endodermal germ cell layer

78
Q

what does epiblast become

A

ectodermal germ cell layer

79
Q

what is the result of forming primitive streak and completion of gastrulation

A

establishes major body axes
- cranio caudal
- medio lateral
- dorso ventral
- right to left axes

80
Q

what is morphogenesis

A
  • shaping processes in an embryo
81
Q

how is morphogenesis controlled

A
  • controlled by cell behaviours
  • result in differential tissue growth
    -Cell behaviours = cell shape, size, position, number and adhesivity
82
Q

what causes dsymorphogenesis

A

Interference with differential tissue growth in an embryo = occasioned by genetic mutation, tetrogen exposure or a combination

83
Q

defamation vs malformation

A

deformation - secondary morphologic defects that are imposed upon an organ or body part due to mechanical forces over a period of time (indirect effect)
malformation = environmental or genetic factors

84
Q

club foot caused by

A

Clubfeet due to compression in the amniotic cavity as a result of insufficient fluid (Oligohydramnios)

85
Q

disruptions vs defects

A

Disruptions = morphological alterations of already formed structures due to destructive processes
Defects produced by amniotic bands

86
Q

Cleft lip

A

something external impacting on normal development = kills and eats up tissue in amniotic band = sawing through upper lip

87
Q

malformation syndrome

A

When dysmorphogenesis occurs as a patten of well characterised multiple primary malformations appearing together in a predictable fashion in one or more tissues due to a specific underlying single or common case = Syndrome

88
Q

Down syndrome

A

extra chromosome
reduced muscle tone - hypotonia
upwards/ down start to eye
enlarged tongue
hyper flexibility

89
Q

foetal alcohol syndrome

A

mother drinking alcohol
short palpebral tissue lengths
thin upper lip
brain damage

90
Q

teratogen

A

any factor or agent that causes birth defect or congenital malformation or congenital anomaly

91
Q

what factors determine the capacity of an agent (teratogen) to produce a birth defect

A
  • genotype of conceptus and maternal genome
  • development stage at time of teratogen
  • dose and duration of exposure to teratogen
92
Q

morphogenesis can be

A

normal development - normogenesis
abnormal development = dysorphogenesis

93
Q

morphogenesis can be

A

normal development - normogenesis
abnormal development = dysorphogenesis

94
Q

tetrogens can

A

inhibit biochemical or molecular process or pathway or alter cellular behaviours

Anatomical sciences (12 decks)

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