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Case 7 > Gastrulation > Flashcards

Gastrulation Flashcards

1
Q

What happens in gastrulation?

A

Bilayered blastula of epiblast + hypoblast converted into embryo with 3 layers:

  1. Ectoderm: outside (surrounding embryo)
  2. Mesoderm: middle
  3. Endoderm: inside (hypoblast)
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2
Q

What is the purpose of gastrulation?

A
  1. Formation and placement of primary germ layers - brings separated cell types into contact (hypoblast + epiblast) -> allowing inductive signals to affect later cell differentiation
  2. Creates body axes
  3. Creates rudimentary gut with mouth/anus
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3
Q

What is differentiation?

A
  • Process by which cells become structurally + functionally specialised
  • Structural/functional specificity depends on proteins cell synthesises
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4
Q

What is the first sign of gastrulation?

A

Formation of primitive streak

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5
Q

What is gastrulation facilitated by?

A
  • Cellular migration/movement
  • Cell-cell recognition
  • Cell signalling
  • Selective adhesion
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6
Q

Describe how the mesoderm is formed

A
  • Invagination + lateral migration of epiblast cells forms mesoderm
  • Epiblasts detach form neighbours + migrate down + laterally
  • Starts where node forms, happens down axis over time
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7
Q

What is the notochord?

A

Solid form of cells which differentiates into rod like structure -> important in development, becomes by product

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8
Q

What are the derivatives of the ectoderm?

A
  • CNS, retina, pineal body, P+A pituitary gland, cranial sensory ganglia + nerves
  • Epidermis, hair, nails + cutaneous + mammary glands, enamel of teeth, inner ear, lens
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9
Q

What are the derivatives of the mesoderm?

A
  • Cranium, CT, dentine, muscles of head, dermis of skin, urogenital system + muscle of viscera
  • Serous membranes of pleura, pericardium + peritoneum, primordial heart + lymphatic cells, adrenal cortex
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10
Q

What are the derivatives of the endoderm?

A
  • Epithelial parts of trachea, bronchi, lungs
  • Epithelium of GIT, liver, pancreas, urinary bladder
  • Epithelial parts of pharynx, tympanic cavity, tonsils + PT glands
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11
Q

What is neurulation?

A

Period of development starting with formation of neural plate + ending with closure neural tube = future brain + spinal cord

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12
Q

What does the developmental date of the embryo depends on?

A

Inductive interaction of newly associated groups of cells.

Primary inductive event = notochord on overlying ectoderm resulting in start of neurulation

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13
Q

What are the components of neural induction?

A
  • inductive signal
  • ability of ectoderm to be competent to respond to inductive signal
  • regional specification
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14
Q

What is the function of Wnt family?

A

Induces ectodermally + mesodermally derived tissues/organs

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15
Q

What is the function of the Sonic hedgehog protein (Shh)?

A

Initially expressed in notochord, induces neural patterning + patterning somites

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16
Q

What is the function of TGF-B family of proteins?

A

Includes BMPs

Regulate cell differentiation

17
Q

What does primary neurulation divide the ectoderm into?

A
  1. Externally positioned epidermis of skin
  2. Neural crest test (NCC) form in region connecting neural tube with epidermis
  3. Internally positioned neural tube
18
Q

What does the neural tube have to facilitate closure?

A
  • Hinges to facilitate closure

- Cell adhesion molecules

19
Q

Describe the closure of neural tube

A
  • delayed in humans
  • neural plate forms in anterior + starts to develop behind primitive nodes as it migrates caudally (during gastrulation)
  • closure begins in neck + proceeds to posterior
20
Q

What is Spina bifida?

A
  • Common birth defect in humans
  • Defect in closure of neural tube + malformations of brain + spinal cord
  • Several forms, vary in severity
21
Q

What is Spina bifida occult?

A
  • mildest form
  • caused by failure of vertebrae to fuse dorsally (neurulation gone wrong)
  • no pain or neurological disorder
  • very common
  • only sign of presence may be dimple or tuft of hair
22
Q

What is Anencephaly?

A

Failure of neural tube closing = baby born without forebrain + cerebrum

23
Q

What are the domains of the neural crest?

A
  • Cranial neural crest - cartilage, bone, cranial neutrons, glia + CT of face, bones of middle ear, tooth primordial
  • Trunk neural crest - dorsal root ganglia, sensory neurons, sympathetic ganglia, melanocytes, all pigment cells
  • Vagal + sacral neural crest - PS nerves of gut
  • Cardiac neural crest - melanocytes, neurons, division between aorta + pulmonary artery
24
Q

What is somatogenesis?

A
  • Formation of whorls of concentric mesodermal cells
  • Marks position of future somites in unsegmented mesoderm
  • Gives rise to successive pairs of somites identical in appearance which differentiate into same cell types
25
Q

What are somites?

A
  • Paired blocks of mesoderm arranged on either side of neural tube at all levels
  • Transient structures
  • Critical for segmental organisation of axial skeleton
26
Q

What do somites form?

A
  1. Cartilage (then bone) of axial skeleton
  2. Muscles of rib cage, limbs + back
  3. Cells that contribute to CT of dermis
27
Q

What determines the fate of somites?

A

Specific regions:

  1. Sclerotome
  2. Myotome
  3. Dermatome

Case 7 (8 decks)

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