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ANAT1003 > Formation Of The Body Plan > Flashcards

Formation Of The Body Plan Flashcards

1
Q

What does the ICM of the blastocyst consist of?

A

Hypoblast layer, epiblast, amniotic membrane

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2
Q

What does the amnion (cavity) separate?

A

The amniotic membrane and the epiblast

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3
Q

What does the hypoblast form?

A

Heuser’s membrane

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4
Q

What epithelium is the epiblast?

A

Simple cuboidal epithelium

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5
Q

What does the ectoderm form?

A

Epidermis
nervous system
cartilage/bone in the head

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6
Q

What does mesoderm form?

A 
Cartilage/bone
Connective tissue
Muscle
Kidney
Blood 
Vasculature
Heart
Gonads
Somatic cells
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7
Q

What does the endoderm form?

A 
Digestive tract epithelium
Lungs
Liver
Gall bladder
Pancreas
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8
Q

What does gastrulation mean?

A

Gut formation (but also formation of the mesoderm in most animals)

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9
Q

What does gastrulation involve?

A

A coordinated series of cell movements that place the endoderm and mesoderm inside the embryo, where they give rise to internal organs

Defects in this process - severe consequences -> miscarriage

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10
Q

What causes the formation of a second embryo?

A

Grafting the node to a new location in the epiblast causes the formation of a secondary embryo, in which the graft forms the notochord and parts of the neural tube and mesoderm.

Node is an organiser in birds and mammals equivalent to the Spemann organiser of amphibian gastrulae

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11
Q

What is an organiser?

A

A region of the embryo responsible for specifying cell fares (eg the node) , affecting the whole embryo or part of the embryo

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12
Q

What does a signalling centre do? (Organiser)

A

Secretes diffusible signalling molecules that may act as morphogens (establishing different fates in a concentration dependent manner)

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13
Q

What do the gastrula organiser cells do?

A

Secrete proteins (Chordin and Noggin) that act across the embryo in all three germ layers to establish different cell fates

-> induce the neural plate in the ectoderm + act as morphogens to divide the mesoderm into different territories

(Same proteins secreted by mammalian node)

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14
Q

What do cells migrating through the node form?

A

Prechordal mesoderm and notochord

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15
Q

What do cells migrating through the primitive streak form?

A

Paraxial mesoderm
Intermediate mesoderm
Lateral plate mesoderm

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16
Q

How are mesoderm tissues established?

A

In response to a gradient of Bone Morphogenetic Protein (BMP) which is lowest in the dorsal midline

Gradient is established by BMP inhibitors (Chordin and Noggin) secreted by the notochord

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17
Q

What is neurulation?

A

The formation of the neural tube from the dorsal ectoderm, involving a coordinated series of cell movements and cell shape changes that place the developing NS inside the embryo where it forms neurones, glia, CNS, PNS

  • usually contiguous with gastrulation
18
Q

What do defects in the process of neurulation give rise to?

A

Neural tube defects such as anencephaly and spina bifida

19
Q

What is the neural plate?

A

The precursor of the nervous system

20
Q

What is the first visible sign that the neural plate is forming?

A

Neural plate cells elongate to form pseudostratified columnar epithelial cells while cells of the epidermis remain cuboidal

21
Q

What is regression?

A

As the embryo expands through cell proliferation, the primitive streak becomes restricted to the posterior margin of the epiblast

Cells migrate through the primitive streak to form different cell types

22
Q

What secretes signals that induce the neural plate in the overlying ectoderm

A

The node, notochord and prechordal mesoderm secrete signals (FGF) that induce the neural plate in the overlying ectoderm

23
Q

What is BMP4?

A

An epidermalising signal (cells no longer become epidermis if BMP signalling is inhibited)

24
Q

What do Chordin and Noggin inhibit?

A

BMP4

25
Q

What signals induce the neural plate?

A

FGF signals

26
Q

When does neural tube formation occur?

A

During fourth week of human development

27
Q

How does the neural tube form? (neurulation)

A
  • Neural plate folds along midline causing lateral edges to rise
  • folds form (hinge points) where cells constrict their apical surfaces
  • lateral edges of neural plate move towards each other + fuse to form to neural tube
28
Q

What is neural tube defect anencephaly?

A

Cephalic portion of neural plate fails to close, brain is undeveloped/ parts are missing

  • stillborn/ miscarried early in pregnancy
29
Q

What is neural tube defect spina bifida?

A

Spinal cord and meninges protrude from a spinal opening - incomplete closing of membranes around spinal cord

-> nerve damage permanent, paralysis, bowel and bladder problems

30
Q

What can one do to reduce neural tube defects (NTD) by 70%?

A

Add folic acid to diet of women a month before conception and through first trimester

31
Q

What is the neural crest?

A

A population of pluripotent cells formed by cells at the margin of the neural plate and epidermis that break away from ectoderm and migrate to different locations in the embryo as the neural plate folds to form to neural tube

-> form different cell types as determined by interactions with cells in their new location

32
Q

What are the subdivisions of the neural tube?

A

Forebrain: telencephalon, diencephalon

Midbrain: mesencephalon

Hindbrain: rhombencephalon

Spinal cord

33
Q

What is the hindbrain separated into?

A

Seven transient segments known as rhombomeres (r1-7)

34
Q

What does the telencephalon contain? (Part of forebrain)

A

Cerebral cortex
Hippocampus
Basal ganglia
Olfactory bulb

35
Q

What does the diencephalon contain? (Part of forebrain)

A

Thalamus
Subthalamus
Hypothalamus
Epithalamus

36
Q

What does the mesencephalon contain? (Midbrain)

A

Tectum
Tegmentum
Ventricular mesocoelia
Cerebral peduncles

37
Q

What does the rhombencephelon contain? (Hindbrain)

A

Medulla, pons, cerebellum

38
Q

What is organogenesis?

A

The period during a 4 week period after the formation of the body plan where most of the organs are formed

39
Q

What is the last organ to become functional and when?

A

The lungs become functional at birth

40
Q

What can fetal growth be affected by?

A

Maternal age
Disease
Diet
Drugs (alcohol, nicotine etc)

ANAT1003 (6 decks)

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