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Body logistics > L11- Early embryology 2 > Flashcards

L11- Early embryology 2 Flashcards

1
Q

outline the broad stage of early embryology

A
  1. fertilisation and implantation
  2. gastrulation
  3. neurulation
  4. segmentation- somites
  5. folding
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2
Q

a zygote

A

single cell formed when egg and sperm cell fuse- fusion is known as fertilisation

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3
Q

cleavage- first cell division- occurs

A

within 24-30h after fertilisation

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4
Q

by late cleavage what is formed

A

morula (32 cells)

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5
Q

when does blastulation occur

A

day 4

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6
Q

blastulation

A

2 types of cell are produced

  • outer cell- trophoblast cells
  • inner cell mass
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7
Q

compaction

A

first cavity forms within blastocyst- blastocoel- pushes inner cell mass to one side

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8
Q

after blastulation

A

blastocyst hatches from zona pellucida

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9
Q

inner cell mass differentiates into

A

epiblast- aminiotic cavity

hypoblast- primitive yolk sac

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10
Q

implantation occurs

A

on day 6-7

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11
Q

summary of zygote to embryoblast

A
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12
Q

gastrulation starts on

A

day 16 (week 3)

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13
Q

during gastrulation what occurs

A

production of germ layers

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14
Q

name the germ layers

A

ectoderm

mesoderm

endoderm

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15
Q

ectoderm

A

epidermis, hair, nails, brain, spinal cord, peripheral NS

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16
Q

mesoderm

A

muscle, bone, connective tissue, notochord, kidney, gonads, circulatory system

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17
Q

endoderm

A

epithelial lining of the digestive tract

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18
Q

first step of gastrulation

A

formation of primitive streak

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19
Q

primitive streak determines the

A

midline of the body

  • should have mobile cilia which mean the body structures are on the right side of the body
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20
Q

prior to gastrulation the embryonic disk is

A

bilaterally symmetrical

  • but int he body clear differenc ebetween left and right side
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21
Q

situs invetus

A
  • Complete mirror image viscera
  • Commonly exults in immobile cilia
    • Infertile
  • No associated morbidity
  • Problems arise if there is both normal and mirror image disposition
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22
Q

immotile cilia during gastrulation mean

A

waft organs into the right direction

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23
Q

during gastrulation the hyboblast is replaced and the epiblast differentitated into the trilaminar disk

A

ectoderm

mesoderm

endoderm

24
Q

directly beneath the primitive the streak in the mesoderm what is formed

A

the notochord

25
Q

when does the notochord form

A

week 4

26
Q

the notochrod

A

notorchord helps define major axis of the body and are important in neurulation (triggers it)

27
Q
A
28
Q

neurulation occurs

A

in two stages

29
Q

stage 1

A

formation of neural tube

30
Q

second stage of neurulation

A

Notochord also causes the mesoderm to subdivide and differentiate

31
Q

in the first stage the notochord causes the ectoderm above to

A

thicken

32
Q

neural tube formation

A
  1. Triggered by signals from the notochord
  2. Just above the notochord the ectoderm thickens (neural plate) and forms a fold producing a neural groove
  3. On either side of the neural groove folds will form
  4. Neural folds come together until the two-fold touch each other
  5. Neural tube found in the mesoderm dissociates from the rest of the ectoderm and the rest of the ectoderm will seal itself back together
33
Q
A
34
Q

neural tube will become the

A

brain stem

35
Q

second stage of neureulation

A

Notochord also causes the mesoderm to subdivide and differentiate

36
Q

notochord comes from the

A

axial meosderm

37
Q

somites will come from the

A

paraxial mesoderm

38
Q

somites differentiate into

A

muscle, cartilage, bone, and dermis

myotomes and dermatomes

39
Q

intermediate mesoderm si the

A

original of urogenital sysrtem- kidney, gonads, adrenal glands

40
Q

lateral plate mesoderm

A

heart, blood vessels, muscle in our organs

41
Q

after neurulation

A

segmentation and organisation of the mesoderm–> giving rise to somites

42
Q

somites

A

organisation of oparaxial mesoderm into segements

43
Q

how many somite pairs

A

31

44
Q

first pair of somites appear

A

on day 20 in the occipital region

45
Q

somites give rise to

A

repeating structures such as…

  • vertebrae
  • ribs
  • intercostal muscle
  • spinal cord segments
46
Q

somites guide

A

innervation by myotomes

47
Q

somite derivative

A

dermatome

myotome

sclerotome

48
Q

dermatome

A

skin section

  • dermis
49
Q

myotome

  • muscles
A
50
Q

sclerotome

A

hard tissue section

  • bone
51
Q

31 somites and 31

A

spinal nerves

52
Q

why is embryonic folding important

A

before embryonic folding, the mouth is at the same level as the heart

53
Q

aim of folding

A

to present only ectoderm to the otuside world

54
Q

what folding achieves

A

Draws together the margins of the disk

  • Creating a ventral body wall
  • Pilling amniotic membranes around the disc
    • Embryo becomes suspended within the amniotic sac
    • Pulling connecting stalk enthralling
  • Also creates the primordium of the gut, put the heart and the primordium of the diaphragm in the right place and creates a new cavity within he embryo (GI tract)
55
Q

explain folding brefiled

A

the cranial (head) and caudal (back) fold in towards eachother

  • the endoderm (GI tract) folds into the middle, with the ectoderm covering around it
  • when the tract is formed, the defintitve yolk sac will be coming out from it
  • this yolk sac will be pinched off
56
Q

diagram of folding con..

A
57
Q

by the end of the 4th week

A
  • Nervous system has started to form
  • Segments have appeared
    • Assigning tasks to specific cells
  • Embryo has folded, putting everything in right place

Body logistics (39 decks)

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