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Embryology RCM > Embryonic Period > Flashcards

Embryonic Period Flashcards

1
Q

Embronic Period

A
  • critical period of rapid growth
  • primordia of all the organs and organ systems appear from the 3 germ layers: organogenesis
  • sensitive to substances that induce congenital malformations: teratogens
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2
Q

Duration of period

A

3rd-8th week

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3
Q

Where does the fusion of the neural fold begin?

A

Cervical region (5th somite) and proceeds cranially and caudally.

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4
Q

Grastrulation

A

occurs during the 3rd week and includes neurulation

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5
Q

Neurulation

A

neural plate and beginning of neural tube formation

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6
Q

Where does folding occur?

A

cranial and caudal ends (head and tail fold) and sides (lateral folds)

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7
Q

What embryonic layers form the oropharyngeal and cloacal membrane?

A

ectoderm and endoderm

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8
Q

What region is the organizer of the body axes?

A

Node in the dorsal region

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9
Q

Nodal function

A

initiates and maintains primitive streak.. a TGFB famili

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10
Q

ACE

A

Anterior visceral endoderm: establishes cranial end before gastrulation

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11
Q

Important TFs for head formation

A

secreted by ACE: OTX2, Lim1, HESX1 and cerberus… inhivit nodal activity in cranial end of embryo

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12
Q

BMP4

A

Once streak is formed, BMP4 and FGF ventralize the mesoderm to contribute to kidneys, blood, and body wall of mesoderm

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13
Q

Goosecoid: what it activates and effects

A

activates chordin, nogging, and follistatin to inhibit BMP expression on the dorsal mesoderm in the cranial region… contributes to regulation of head formation

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14
Q

Brachyury: regulation and location of expression

A

gene that regulates dorsal mesoderm in middle and caudal regions. Expressed in the node, notochordal precursol cells and notochord

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15
Q

Where to the TFs of brachyury bind?

A

bind to a T box in the DNA

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16
Q

What disease is caused by the absence of Brachyury?

A

sirenomelia or caudal dusgenesis

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17
Q

What genes regulate the cranio-caudal axis?

A

Homeobox genes

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18
Q

Grastrulation associated defects?

A

conjoined twins by over-expression of goosecoid or sirenomelia by absence of Brachyury

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19
Q

What disease is cause d be the over-expression of Goosecoid?

A

conjoined twins

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20
Q

What genes regulate the formation of the left side?

A

Brachyury in the notochord is essential for expression of Nodal, Lefty-1, and Lefty-2

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21
Q

What genes regulate the formation of the right side?

A

SHH (sonic hedgehog) by repressing expression of left side genes and snail (TF essential to establish the right side)

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22
Q

Surface ectoderm derivatives?

A

-Epidermis and its derivatives: nails, hair, lens, epithilium of sweat glands, sebaceous glands, and mammary glans. -Sensory placodes (auditory and nasal placodes) - Terminal portion of the anal canal, oral cavity and its derivatives: parotid glands, adenohypophysis, and enamel of teeth. -Neural Tube -Neural Crest

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23
Q

What are derivatives of the neural tube?

A

-nervous tissue of the brain (including macroglia) -Spinal cord -Pineal Gland -Retina and optic nerve -posterior part of pituitary gland

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24
Q

What are derivatives of the neural crest?

A

-PNS (including ganglia and schwann cells) - Melanocytes -Dental papilla -Meninges - Mesenchyme and visceral skeleton of head and neck - Chromaffin cells of the adrenal medulla - Parafollicular cells of thyroid gland

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25
Q

The mesodermal germ layer gives rives rise to what three layers?

A

Paraxial Mesoderm, Intermediate mesorderm, amd lateral plate mesoderm

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26
Q

Paraxial mesoderm gives rise to… when and where

A

somites by the end of the 3rd week.. first appear in the cephalic (occipital) region, then cephalocaudally -3 pairs of somites/day until 42-44 appear in the 5th week.

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27
Q

What do somites give rise to?

A

the axial skeleton: 1st occipital and last five to seven cocygeal somites later disappear

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28
Q

Sclerotome

A

segmented somites that give rise to tendon cartiladge of bone component and vertebral column

29
Q

Myotome

A

segmented somite; limb precursors and muscles of the back

30
Q

Dermatome

A

segmented somites; dermis and subcutaneous tissue of the skin

31
Q

Intermediate mesoderm give rise to… when

A

Urinary system and gonads…day 21

32
Q

Lateral plate mesoderm can be divided into

A

Parietal mesoderm layer and visceral mesoderm layer

33
Q

Parietal mesoderm + ectoderm:

A

somatopleure

34
Q

Visceral mesoderm + endoderm:

A

splanchopeure

35
Q

Parietal mesoderm gives rise to…

A

a serious of membranes lining the: - thoracic cavity (parietal pleura) -covering of the heart (pericardium) - peritoneal cavity (peritoneum)

36
Q

Visceral layer gives rise to…

A

a serious of membranes lining the: -organs of the abdominal cavity

37
Q

What are other derivatives of the lateral plate mesoderm?

A

-primordial heart -blood and lymphatic cells -spleen -adrenal cortex -connective tissue and muscle of viscera

38
Q

Vasculogenesis

A

vessels arrive from blood islands (mesoderm of yolk sac and lateral plate mesoderm)

39
Q

Angiogenesis

A

new vessels sprout from existing one

40
Q

What gives rise to the cardiogenic area?

A

Heart primorium

41
Q

What molecule regulates blood vessel formation? function in each pathway

A

VEGF: blood vessel formation PDGF and TGFB: maturation and modeling of blood vessels

42
Q

VEGF and vasculogenesis

A

-FGF stimulates VEGF secretion -Hemagioblasts are formed: blood cell and blood vessels precursors -tube formation with angioblasts (blood vessel precursors) endothelial cells) and hematopoietic stem cells (blood cells precursors

43
Q

VEGF and angiogenesis

A

VEGF stimulates proliferation of endothelial cells at point where new vessels will sprout

44
Q

what can arise from abnormal vessel growth?

A

capillary hemangiomas: - most common tumor of infancy -associated with craniofacial structures -might be associated with high levels of IGF-1 -most disappear or treated with laser and steroid

45
Q

What organs do hematopoietic stem cells colonize? where do they arise and when do they colonize?

A

they arise from mesoderm surroiunding the aorta colonize the: -liver 9wks -spleen and thymus: 12wks - bone marrow 28wks

46
Q

Primordial cardiovascuular system at the end of the 3rd wk

A

the heart tubes have fused to form a tubular heart that is joind to veseels in the embryo, yolk sac,connecting stalk, and chorion -Precardial coelom -Endocardial heart tube

47
Q

Endodermal derivatives

A

GI tract epithilium, liver, pancreas, urinary bladder, and urachus, allantois, cloaca, hindgut, gallbladder, pharyngeal pouches, and lung bud

48
Q

What presents in a 7-somite embryo?

A

embryonic disk bulges into the amniotic cavity, heand and tail folds, and precardial cavity exists

49
Q

When and where does the bucopharyngeal membrane rupture?

A

4th wk: leaves open connection between the amniotic cavity and the primitive gut… in foregut

50
Q

When and where does the cloacal membrane rupture?

A

7th wk: opening for the anus… in the hindgut

51
Q

How do the midgut and yolk sac communicate temporarily? Which one is obliterated after and when?

A

vitelline duct, the vitelline duct is obliterated… by 2mo. the yolk sac is redundat and it shrivels away

52
Q

When do the invagination of the primitive streak stop?

A

4th wk, then it shrivels and disappears

53
Q

What structures are present in the 4th week?

A

Neural tube, otic pit (primordium of ear), lens placode (primordium of lens), uppder limb bud, heart prominence, forebrain prominence, and caudal eminence

54
Q

What structures are present in the 5th week?

A

Cervical sinus, and mesonephric ridge (future site of mesonephric kidneys)… minor body changes, growth of head (towards the hear prominence), cervical sinus is visible

55
Q

What structures are present in the 6th week?

A

Digital rays of hand plate and auricular hillocks forming auricle of external ear

56
Q

What structures are present in the 7th week?

A

notches between digital rays -reduction of communication between the yolk sac and primordial gut -umbilical herniation where intestines enter the extraembryonic coelom

57
Q

What structures are present in the 8th week?

A

-tail-like caudal eminecence is present at the beginning but then disappears -scalp vascular plecus (band around head) -digist completely separated -purseposeful limb movement: ossification occurs in the femur -distinct human characteristics but still disproportion between head and trunk sexless appearance

58
Q

How can the embryonic age be estimated?

A

-Greatest length (GL): 3rd and 4th wks, embryos are straight -Crown-Rump-Length (CRL): older embryos, curved embryos -Crown-Heel-Length (CHL): 8th week embryos

59
Q

Carnegie Stage

A

criteria for estimating development stages in human embryos

60
Q

What is used to determine stage of pregnancy?

A

chorionic cavity (gestational sac)

61
Q

CRL 25mm

A

7-8 wks has chrion, amnion and yolk sack

62
Q

CRL 4.8mm

A

4.5 wk embryo: chorion cavity and yolk sack

63
Q

9wk fetus

A

amniotic fluid, placenta, and uterin wall can be seen in ultrasound

64
Q

Neurulation steps and when

A

Neural fold appears, neural crests go up beacuse of it, neural fold aproach each other and fuse forming the neural tube (22 days)

65
Q

Where does the neural fold fusion begin?

A

in the cervical region (5th somite) and proceeds cranially and caudally

66
Q

Why does folding of the embryo occur and where?

A

it occurs from rapid growth at the site of the future brain and spinal cord

Folding occurs at:

  • cranial and caudal ends
  • sides (lateral folds)
  • constriction at the embryo-yolk sac junction
67
Q

How ar cranial and caudal regions produced?

A

folding of the ends of the embryo ventrally produces head and tail folds

68
Q
A

Embryology RCM (5 decks)

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