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B4 Anatomy > Basics Of Embryology 2 > Flashcards

Basics Of Embryology 2 Flashcards

1
Q

What is gastrulation and when does it occur?

A

Around 16 days, this is when structures start to appear in the embryo

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2
Q

The cranial end of the primitive streak is expanded as the ______________ and it contains a circular depression called the ________________, which is continuous down the midline of the primitive streak with a trough-like depression called the _______________.

A

Primitive node

Primitive pit

Primitive groove

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3
Q

The primitive pit and groove represent what?

A

Areas where cells are leaving the primitive streak and moving into the interior of the embryonic disc

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4
Q

During gastrulation, the hypoblast cells become the…

A

Definitive endoderm

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5
Q

The area between the endoderm and the epiblast contains cells that coalesce to form the…

A

Intraembryonic mesoderm

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6
Q

After gastrulation is complete, the epiblast is called the:

A

Ectoderm

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7
Q

Just before the neural tube forms, a mesoderm migration begins to form in 3 areas:

A

Mouth - prechordal plate

Heart - cardiogenic mesoderm

Amnion, yolk sac, allantois (future placenta) - extraembryonic mesoderm

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8
Q

Order of migration cranial to caudal, mid-gastrulation

A
  1. Notochord
  2. Head mesoderm
  3. Somites
  4. Intermediate mesoderm
  5. Lateral plate mesoderm
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9
Q

The future vertebrae forms from the…

A

Notochord

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10
Q

How does the notochord form?

A

It is derived from the primitive node and ends up in the mesodermal layer. Therefore its considered a mesodermal derivitive.

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11
Q

The unsegmented region of the mesoderm becomes the:

A

Head mesoderm.

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12
Q

The head mesoderm gives rise to the

A

Face, jaw, and throat.

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13
Q

What is the mesenchyme?

A

A loosely organized, mainly mesodermal embryonic tissue that develops into connective and skeletal tissue, including blood and lymph.

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14
Q

The bands of cell found in the mesoderm soon segment into these blocklike condensations

A

Somites

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15
Q

When do the first pair of somites first form?

A

Day 20 or so. The remainder form at a rate of about 3 or 4 per day.

By about day 30, around 42 to 44 pairs of somites form.

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16
Q

What is the final count of somites, and why?

A

About 37. Because the caudalmost somites disappear, due to the fact humans dont have tails…idiot

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17
Q

Somites give rise to….

A

Most of the axial skeleton.

Vertebral column, part of occipital bone

Musculature of the neck, body wall, and limbs

Dermis of the neck

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18
Q

Intermediate mesoderm

A

Connects the paraxial mesoderm (somites) with the lateral plate mesoderm.

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19
Q

What does the intermediate mesoderm differentiate into?

A

Urogenital structures. It also helps to develop the excretory units of the urinary system and the gonads.

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20
Q

Lateral plate mesoderm splits into….

A

Parietal/somatic
-forms the body wall folds

visceral/splanchnic
-forms the walls of the gut tube

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21
Q

What are the four main events of neurulation?

A

Formation of the neural plate

Shaping of the neural plate

Bending of the neural plate

Closure of the neural groove

22
Q

During gastrulation, what is the major inductive event that occurs in the embryo?

A

Neural induction

23
Q

What happens during neural induction?

A

The primitive node induces the overlying ectoderm to thicken as the neural plate.

24
Q

The is the earliest rudiment of the central nervous system?

A

Neural plate

25
Q

Around what day does the primitive streak disappear? And what is appearing in its place?

A

Day 25

Neural plate, and the first expansions of the brain

26
Q

As the neural plate flattens along its length, the ________ disappears

A

Primitive streak

27
Q

During subsequent development, the neural plate will fold up into a what?

A

Neural tube

28
Q

During the formation of the neural tube, what arises from the lateral edges of the neural plate?

A

Neural crest cells

29
Q

Neural plate, crest, and tube are all part of…

A

Ectoderm

30
Q

The development of the ________ ______, _________ ____________, and __________ __________, all happen simultaneously and in synchrony.

A

Neural tube, mesoderm migrations, and notochord formation

31
Q

What is the “Tube-Within-a-Tube Body Plan”

A

The result of body folding during embryonic development.

Consists of an embryo body design composed of two main tubes: an outer ectodermal tube forming the skin and an inner endodermal tube forming the gut.

The space between the two tubes is filled mainly with mesoderm, the lateral plate mesodermal part of which splits to form the body cavity (coelem).

The neural tube, derived from the outer ectodermal tube, becomes internalized during the process of neurulation

32
Q

The blastocyst contains which 2 parts?

A

The inner mass cells and the trophoblast

33
Q

Cells in the ICM differentiate into…?

A
  1. Epiblast which gives rise to the embryo proper (dorsal - back)
  2. Hypoblast which gives rise to the primary (extraembryonic) endoderm that forms the yolk sac (ventral - belly)
34
Q

What is the primitive streak?

A

The first marker of the craniocaudal axis.

It occurs on the dorsal side of the epiblast and near the caudal end of the epiblast. The cranial end of the streak proliferates to become the primitive node and results from proliferation and migration of cells.

35
Q

How do we turn the 2 layer disc into a 3 layer disc?

A

Through gastrulation.

There is a depression in the primitive streak called the primitive groove, and it is the site along which the cells migrate through the epiblast.

The first cells to migrate through the epiblast form the endoderm.

Later cells form the mesoderm, and non ingressing cells form the ectoderm.

2 populations of cells that migrate through the streak generate the 3 layer disc from 2 layer disc.

36
Q

What is gastrulation?

A

Process by which the 3 germ layers are formed through cell migration

37
Q

What are the 3 ways in which cells can migrate through the epiblast and why is that important?

A
  1. Through the node
  2. Near the node
  3. Away from the node

This is important because they create different cell fates

38
Q

How is the neural tube formed?

A

Dorsal ectoderm becomes the neural plate. Lateral edges become elevated to form neural folds and midregion becomes depressed and form the neural groove. Neural fold moves toward each other and fuse to become the neural tube. Neural tube then detached from the overlying ectoderm.

39
Q

What does the nonneural ectoderm become?

A

The skin

40
Q

What does the neural ectoderm become?

A

The brain and spinal cord

41
Q

What germ layer does the notochord derive from?

A

Mesoderm

42
Q

What is neurulation?

A

Formation of the neural tube

43
Q

How do cells fuse during neurulation?

A

Cells in the middle of the neural folds fuse first and zippers both anteriorly and posteriorly at the same time

44
Q

What are cranial and caudal neuropores?

A

Transient openings at either end of the neural tube after zippering of the neural folds occur

45
Q

How do birth defects or neural tube defects occur?

A

When the neuropores do not close correctly

46
Q

How can women avoid neural tube defects?

A

Consume more folic acid

47
Q

What are the functions of the notochord?

A

Transient structure that defines the body axis

Provides rigidity to the embryo

Functions as a signaling center to, at least, induce neural fates such as which neural cells become dorsal or ventral

Precursor for the axial skeleton

48
Q

Which germ layer forms the neural crest?

A

Ectoderm

49
Q

What are neural crest cells?

A

Migratory cells that are ectoderm-derived and migrate throughout the body to give rise to a diverse number of cell fates

50
Q

What are the 4 regions of the mesoderm?

A

Axial (gives rise to the notochord)

Paraxial (gives rise to somites, adjacent to the neural tube)

Intermediate (kidney/gonads)

Lateral plate (lining of the organ cavities)

51
Q

What are the derivatives of endoderm?

A

Gives rise to the GI tract, epithelial lining of lung buds and trachea, liver, gall bladder, and pancreas

B4 Anatomy (10 decks)

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