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Embryology > Gastrulation > Flashcards

Gastrulation Flashcards

1
Q

Gastrulation

A

Week 3
- trilaminar disc
1.) Ectoderm
2.) Mesoderm
3.) Endoderm

-multipotent

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1
Q

Movement of cells for gastrulation

A

1.) Preview of main events
2.) Steps at epiblast; cell replication and cell movement
3.) Primitive streak
4.) Cells diving to form Endoderm
5.) Celling diving to form Mesoderm
6.) Mouth and anus
7.) Notochord development and SHH
8.) First Mesoderm’s (3 types)

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2
Q

week 2 development

A

within the endometrium
- amniotic cavity and chorionic cavity
- extraembryonic membranes

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3
Q

Bilaminer disc

A

epiblast
hypoblast

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4
Q

Epiblast

A

ectoderm

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5
Q

Hypoblast

A

endoderm

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6
Q

Mesoderm

A

develops between due to invagination and the primitive streak

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7
Q

The upper epiblast layer and upper hypoblast layer migrate upward toward ventral pole creating 2 cavities

A

1.) Amniotic cavity
2.) Umbilical vesicle

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8
Q

Amniotic cavity

A

houses embryo

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9
Q

Umbilical vesicle

A

becomes umbilical (or yolk if not human)

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10
Q

Trophoblast

A

develops into Chorion and Placenta

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11
Q

Following cytotrophoblast

A
  • cells move out, enzyme digestion, cells break open, fuse together and this forms “syncytium”

~These pools will eventually meet up with endometrial mother blood vessels and the cytotrophoblast cells will move into the pools and form chorionic villi and thus the PLACENTA

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12
Q

syncytium

A
  • collection of cytoplasm with lots of nucleus
  • this is synctiotrophoblast
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13
Q

What are cells with well defined margins and nuclei called?

A

Cytotrophoblast

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14
Q

Chorionic villi

A

“Two deliveries”

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15
Q

Placenta (CV) arteries

A

carry deoxygenated blood while the veins carry oxygenated blood (it is opposite of what red and blue color suggest!)

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16
Q

Chorionic villi arteries

A

carry poorly oxygenated fetal blood and waste products from the fetus

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17
Q

Chorionic villi veins

A

carries oxygenated blood and nutrients to the fetus

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18
Q

The placental membrane, composed of extra fetal tissues, separates the maternal blood in the intervillous space from the fetal blood in the capillaries in the villi

A
  • note that the placental membrane becomes very thin at full term
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19
Q

Hofbauer cells are thought to be what?

A

Phagocytic

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20
Q

The intervillous space of the placenta

A
  • maternal blood bathes the villous trees, which are covered by syncytiotrophoblasts (SYN) that are underlaid by a population of progenitor cells called Cytotrophoblasts (CTB)
  • the syncytial knots are formed on these villi, and trophoblast-derived material is transferred into the maternal circulation
  • EVT indicates extravillous trophoblasts
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21
Q

Fetal-maternal interface and immune cells at term pregnancy

A
  • the placenta serves to ensure exchange of nutrients and gases between the maternal and fetal blood circulation
  • the fetal part of the fetal-maternal interface consists of chorionic villi that extend from the chorionic plate into the intervillous space and bathe in maternal intervillous blood
  • on the maternal side, the decidua parietals and decidua basalis are in direct contact with fetal membranes (amniochorion) and the invading fetal extravillous trophoblasts, respectively
    -the intervillous blood enters the intervillous space through spiral arteries and leads this compartment through uterine veins
  • maternal immune cells in the intervillous blood are in direct contact with the fetal syncytiotrophoblast and decimal immune cells can interact with extravillous trophoblasts, decimal stromal cells, Hofbauer cells, mucosal associated invariant T cells, macrophages, uterine natural killer cells
  • the pink cells in the intervillous space depict erythrocytes
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22
Q

Normal placental development

A

1.) Extravillous cytotrophoblasts proliferate in anchoring columns to successfully invade through the decidua

2.) And transform the distal spiral arteries

3.) These changes mediate high volume flow at low pressure into the intervillous space

4.) The placental villi are covered by the villous trophoblast compartment, compromising cytotrophoblasts that proliferate to generate the outer syncytiotrophoblast in direct contact with maternal blood

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23
Q

Uteroplacental vascular insufficiency

A

1.) Extravillous cytotrophoblasts are less successful in invading the maternal decidua and may be removed by the maternal immune system

2.) Consequently, the distal spiral arteries are narrower and diseased

3.) Accompanied by atherosis or local fibrin deposition

4.) And reduced endo-vascular invasion

5.) Hypoxia or hypoxia-deoxygenation injury

6.) Has direct effects on the villous trophoblast compartment, reducing syncytial function

7.) That may trigger the formation of syncytial knots

8.) These accumulate but may fragment and shed into maternal blood

9.) Whereas areas deficient in syncytial fusion may exhibit focal necrosis

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24
Q

Purpose of gastrulation: Bilaminar disc is converted to _________

A

trilaminar disc

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25
Q

Gastrulation is the process of_____ _____ formation

A

germ layer

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26
Q

3 germ layers formed during gastrulation

A

1.) Ectoderm (external)
2.) Mesoderm (middle)
3.) Endoderm (inner)

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27
Q

The pattern of gastrulation is similar in mammals and __________

A

avian species (birds)

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28
Q

During gastrulation, a ______ is formed

A

body axis

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29
Q

After gastrulation, the embryo is now called a ________

A

gastrula

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30
Q

Animals that have only 2 initial cell layers

A

diploblastic
1.) ectoderm
2.) endoderm

  • simple body plan
  • few cell types
  • sponges, jellyfish, corals, sea anemones
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31
Q

Animals have 3 initial cell layers

A

triploblastic
1.) ectoderm
2.) mesoderm
3.) endoderm

  • complex body plan
  • more cell types
  • humans, annelids, arthropods, Mollusca, echinoderms, chordates
32
Q

Ectoderm (outside skin)

A
  • epidermis:
  • sweat glands
  • hair follicles
  • mouth and anus linings
  • nervous and sense organs
  • jaws and teeth (and enamel)
  • pituitary gland, adrenal medulla
  • germ cells (sperm, egg)
33
Q

Mesoderm (connective tissue)

A
  • skeletal system
  • muscle (3 types)
  • circulatory (blood and vessels)
  • Connective Tissue (CT)
  • lymphatic
  • excretory
  • reproductive (not germ cells) but gonads
  • skin dermis (CT)
  • adrenal cortex
34
Q

Endoderm (lines tubes)

A
  • epithelial linings:
  • GI
  • Respiratory
  • Excretory
  • Reproductive
  • Ducts
  • liver and pancreas
  • thymus, thyroid, parathyroid
35
Q

Ectoderm

A

body surface

36
Q

Mesoderm

A

stuff inside and between

37
Q

Endoderm

A

lines GI

38
Q

Formation (slide 21) of the three primary germ layers occurs during the first ______ weeks of development

A

2
- the embryo at this stage is only a few millimeters in length

39
Q

Preview of main events in movement of cells for gastrulation

A
  • Caudal groove
  • Primitive streak
  • movement of cells and pseudopodia
  • trilaminar disc (3 germ layers)
  • Notochord development
  • 3 types of mesoderm development
40
Q

Primitive streak

A
  • primitive groove (narrow depression)
  • primitive pit (dimple)
  • primitive node (small mound of tissue)
41
Q
  1. Steps at epiblast: cell replication and cell movement (day 14)
A
  • 1st caudal groove, starts at tail (caudal) and moves toward head (cranial)
  • this creates the cranial caudal axis!
  • either side of the groove begins BILATERAL symmetry
  • Medial and Lateral are also arranged
  • groove forms on the back (dorsal)
42
Q
  1. Primitive streak steps (Day 14)
A
  • 2nd groove elongates and cells MOVE (guitar pic)
  • primitive groove (narrow depression)
  • primitive pit (dimple)
  • primitive node (small mound of tissue)
43
Q
  1. Cells diving to form Endoderm
A
  • 3rd cells of Epiblast
    ~ migrate to primitive groove, bottom of groove and DIVE IN
44
Q

These epiblast cells that get through groove form __________ and differentiate into new cells

A

NEW CELL LAYERS

45
Q

Deep Dive

A

and form deeper embryonic ENDODERM LAYER (Gut)

**REPLACING ventral hypoblast layer

46
Q
  1. Cells Diving to form Mesoderm
A

Shallow dive

47
Q

Shallow Dive

A

Embryonic MESODERM LAYER

48
Q

MESODERM layer

A

1.) Parietal mesoderm (outside)
2.) Visceral mesoderm (organ)

49
Q

Cells that do NOT dive

A

ECTODERM

50
Q

NOW a ____ (after Mesoderm)

A

Trilaminar Disc

51
Q

Tissues of Trilaminar disc (Day 14)

A

1.) Embryonic endoderm
2.) Embryonic mesoderm
3.) Embryonic ectoderm

52
Q

Embryonic endoderm REPLACES_______

A

Trophoblast

53
Q

Trilaminar disc: All these cells are NOW______

A

Multipotent

54
Q
  1. Mouth and Anus Steps (Day 15)
A
  • cranial end
  • caudal end
55
Q

Cranial end

A

Ectoderm pushes down to fuse with endoderm
- this becomes the oropharyngeal membrane (and disintegrates)
- at week 4, becomes the MOUTH

56
Q

Caudal end

A

Ectoderm pushes down to fuse with endoderm
- this becomes the cloacal membrane (and disintegrates)
- at week 7, becomes the ANUS and GENITOURINARY tracts

57
Q

Cranial bilaminar region–> oropharyngeal membrane–> mouth

A

True

58
Q

Caudal bilaminar region–> cloacal membrane–> anus and genitourinary tracts

A

True

59
Q
  1. Notochord development (Day 17)
A

Mesoderm forms into a solid shaft or tube
- This becomes Notochord
- This later becomes “nucleus pulposus” of vertebral column

60
Q

Function of Notochord

A
  • influences how embryo folds early on
  • secretes SHH diffuses out through the disc
61
Q

SHH

A

Sonic Hedge Hog

62
Q

What does SHH do?

A

Tells cells how to differentiate and where to go

63
Q

Notochord

A
  • transient (future nucleus pulposus)
  • influences embryo folding
  • secretes SHH protein (cell awareness in space)
64
Q
  1. First Mesoderm’s –> three types (Day 20)
A

1.) Paraxial mesoderm
2.) Intermediate mesoderm
3.) Lateral mesoderm

65
Q

Day 20- Neurulation

A
  • Notochord stimulates this
  • stimulates ectoderm cells to thicken and form the neural plate
  • neural plate dips down and forms groove
  • the sides of the groove are called neural folds
  • the neural folds rise up and meet each other and fuse forming the neural tube
  • neural tube will become brain and spinal cord
  • this sits between the ectoderm and mesoderm
66
Q

Secondary villi

A

villous capillary system –> link to blood and oxygen from mom

  • a more dense network of chorionic vessels are established with the endometrium anchoring the embryo to the uterus
67
Q

Human development: Week 3

A

1.) Primitive streak
2.) Germ layers
3.) Notochord, SHH, and Neurulation
4.) Villous capillary system

68
Q

Gastrulation Quick Review

A
  • upon arrival in the region of the streak, cells become flask-shaped, detach from the epiblast, and slip beneath it
  • this inward movement is known as INVAGINATION
  • once the cells have invaginated, some displace the hypoblast, creating the endoderm, and others come to lie between the epiblast and newly created endoderm to form mesoderm
  • cells remaining in the epiblast then form ectoderm
  • the EPIBLAST, through the process of gastrulation, is the source of ALL of the germ layers, and cells in these layers will give rise to ALL of the tissues and organs in the EMBRYO
69
Q

Gastrulation

A

process of germ layer formation

70
Q

three germ layers formed during gastrulation

A

1.) ectoderm
2.) mesoderm
3.) endoderm

71
Q

Body axis is formed during______

A

Gastrulation

72
Q

In mammals, the hypoblast and epiblast are divided from what?

A

Inner Cell Mass (ICM)

73
Q

What acts as the initiation site for gastrulation?

A

Primitive streak

74
Q

Cells of the epiblast migrate to the primitive streak and move into the space between the ________ and _________

A

epiblast; hypoblast

75
Q

A proportion of these cells displace the hypoblast , forming endoderm, the _________

A

inner germ layer

76
Q

The _______ will form the primitive gut

A

endoderm

77
Q

Mesoderm, the middle germ layer, develops from migrating epiblastic cells which lie between the ______ and the _______

A

epiblast; primordial endoderm

78
Q

The remainder of the cells of the epiblast differentiate into what?

A

Ectoderm

Embryology (13 decks)

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