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Foundations Week 8 > Germ Layers II > Flashcards

Germ Layers II Flashcards

1
Q

From what does skeletal muscle arise?

A

from the myotome component of the somites

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2
Q

What are myoblasts?

A

muscle precursor cells

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3
Q

Expression of myogenic determination genes (transcription factors) in myoblasts regulates what?

A

the expression of structural muscle proteins

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4
Q

Myoblasts migrate to the site of muscle formation. Individual myoblasts fuse into _____ (micronucleate cells) and eventually assemble into _____ expressing contractile proteins.

A

Myoblasts migrate to the site of muscle formation. Individual myoblasts fuse into MYOTUBES (micronucleate cells) and eventually assemble into MYOFIBERS expressing contractile proteins.

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5
Q

The great majority of the muscles in the face, including those for mastication and facial expression, originate from what?

A

somitomeres in the head region

  • these are the 7 pairs of cranial-most somitomeres that did not develop into somites
  • note that neural crest cells do not contribute to facial muscles
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6
Q

Limb muscles develop in place from ______ surrounding bones.

A

mesenchyme

*this mesenchyme migrated into the limb bud from the myotome region of the somites

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7
Q

The mesenchyme surrounding bones that develop into limb muscles migrated into the limb bud from where?

A

from the myotome region of the somites

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8
Q

Where is smooth muscle surrounding visceral organs derived from?

A

splanchnic mesoderm layer surrounding the endoderm of the gut

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9
Q

For most blood vessels and lymphatic vessels, smooth muscle comes from where?

A

somatic mesoderm

*it seems that endothelial cells secrete signals that recruit smooth muscle cells to the developing blood vessels

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10
Q

The smooth muscle cells in the iris, sweat glands, and mammary glands arise from where?

A

ectodermal tissue

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11
Q

For the ascending aorta and carotid blood vessels, the surrounding smooth muscle is derived from what?

A

neural crest cells that migrated into the pharyngeal arches

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12
Q

Smooth muscle development also involves a myoblast precursor cell. Smooth muscle cells do not fuse, but remain mononucleate. Unlike skeletal and heart muscle, smooth muscle is not what?

A

striated

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13
Q

Myocardial cells that form heart muscle arise form what?

A

the splanchnic mesoderm in the cardiogenic area

  • Genes involved in heart development begin to be expressed in the cardiogenic region very soon after gastrulation
  • cardiogenic region is at the very top, above, kind of around the oral membrane (opposite end of the streak)
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14
Q

One gene known to regulate development of heart muscle is called what?

A

Nkx2-5

*it is a homeobox gene related to the ‘tinman’ gene in Drosophila
Tinman mutant flies have no heart
Similar genes are involved in normal heart development in all organisms

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15
Q

Nkx2-5, what is it?

A
  • gene known to regulate development of heart muscle
  • it is a homeobox gene related to the ‘tinman’ gene in Drosophila
    Tinman mutant flies have no heart
  • Similar genes are involved in normal heart development in all organisms
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16
Q

Cardiac precursors remain close to the endodermal layer and a signal from the _____ is essential for heart development.

A

endoderm

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17
Q

The heart primordia essentially foom a ‘blood vessel’ on each side of the embryo. What is the eventual fate of these ‘blood vessels’?

A

these will eventually fuse into one heart tube at the ventral midline.

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18
Q

Does fusion of cardiomyocytes occur?

A

No.
Like smooth muscle, no fusion of cardiomyocytes occurs. Normal myogenic determination genes are not involved in heart muscle differentiation.

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19
Q

Expression of myogenic determination genes (transcription factors) in what cells regulates the expression of structural muscle proteins?

A

myoblasts (specifically for skeletal muscle)

20
Q

Most of the bone in the body forms from what?

A

mesoderm

*it is important to remember however, that bones of the face are formed from neural crest cells

21
Q

Bones of the face are formed from what?

A

neural crest cells

*not the mesoderm, unlike most of the other bones of the body

22
Q

The axial skeleton is formed from what?

A

the sclerotome component of the somite

*in the case of the vertebral column, sclerotome cells migrate to surround the notochord and the neural tube; these cells then differentiate to form bone

23
Q

Bones of the limb form from what?

A
  • mesodermal mesenchyme that migrates into the limb buds and then condenses in place to form cartilage
  • the cartilage is later ossified to generate the bones
24
Q

The endothelial cells that are the inner lining of blood vessels, and also the smooth muscle cells that surround the vessels, are both of what origin?

A

mesodermal

25
Q

In the extra-embryonic mesoderm, the first endothelial cells and blood cells are found together in structures called what?

A

blood islands

26
Q

What two things are found in blood islands?

A
  • the first endothelial cells
  • blood cells

*blood islands are found in the extra-embryonic mesoderm

27
Q

Within the embryo itself, endothelial precursor cells (angioblasts) arise throughout all mesodermal tissues, except which?

A

the notochord

28
Q

The angioblasts migrate and proliferate and then assemble into loose structures called what?

A

vascular cords

*these cells will only form normal blood vessel tubes in response to a signal from the endoderm. This process of blood vessel formation from individual angioblasts is called vasculogenesis

29
Q

What is vasculogenesis?

A

the process of blood vessel formation from individual angioblasts

mesodermal cell –> angioblast –> angioblasts aggregate –> ECs Aggregate (cord) –> Nascent Vessel (lumenized)

30
Q

Blood vessels in the extra-embryonic region fuse with vessels within the embryo to make a _____ vascular network.

A

continuous

31
Q

Vasculogenesis is only responsible for making the major blood vessels in the embryo. All subsequent formation of blood vessels, including the provision of a blood supply to previously avascular tissues like the brain, is achieved by branching and extension from the primary vessels. This growth from pre-existing vessels is called what?

A

angiogenesis

32
Q

What is angiogenesis?

A

the growth of new vessels from pre-existing vessels
*this forms all blood vessels besides the primary vessels, it is achieved by branching and extension from the primary vessels

33
Q

At the end of gastrulation, the embryo consists of 3 germ layers, but is essentially flat. As neural tissues start to develop the embryo elongates and forms ridges on its dorsal surface. The are of most rapid growth is the brain. As it enlarges, it pushes forward and expands inside what? What does this expansion cause?

A

the amnion

*this expansion causes the head fold

34
Q

The same movements that pushes forward and expands the inside of the amnion, causing the head fold, pushes the developing heart around from where to where?

A

from the cranial to the oral plate to a position on the chest wall

35
Q

Similar growth (to that of the brain) of the tail produces what? And causes what?

A
  • produces a tail fold

- causes the embryo to arch into the amniotic space

36
Q

What causes the embryo to arch into the amniotic space?

A

the growth of the tail and subsequent production of a tail fold

  • I think this all happens by the end of the first month after fertilization
  • this folding along the body of the embryo becomes more pronounced as development proceeds
37
Q

Together these folding movements (head fold, tail fold, arching of embryo into amniotic space) establish what?

A
  • foregut (ends at the oral membrane, now also called the buccopharyngeal or oropharyngeal membrane)
  • midgut
  • hindgut (ends at the cloacal (anus) membrane)
38
Q

At the same time of the folding movements (head fold, tail fold, arching of embryo into amniotic space, gut formation), lateral growth of the somites causes the embryo to do what? What does this result in?

A

fold ventrally
*these movements enclose most of the endodermal tissue, leaving only a small continuity with the yolk sac, the vitelline duct

*the endoderm becomes surrounded by the splanchnic mesoderm layer to form the gut tube. Mesoderm continuous with the gut, and extending between the dorsal body wall and the gut forms the dorsal mesentery.

39
Q

After folding ventrally and enclosing most of the endodermal tissue leaving just the vitelline duct (a small continuity with the yolk sac), the endoderm becomes surrounded by the splanchnic mesoderm layer to form what?

A

the gut tube

40
Q

Mesoderm continuous with the gut, and extending between the dorsal body wall and the gut forms what?

A

the dorsal mesentery

41
Q

What are three medical problems associated with lateral folding?

A
  • Meckel’s diverticulum
  • Gastroschisis
  • Ectopia Cordis
42
Q

Medical problems associated with lateral folding:

Meckel’s Diverticulum

A

failure of complete regression of the yolk sac results in a very common birth defect (about 2% of the population) called Meckel’s diverticulum, which is an out-pocketing of the ileum at the end of the small intestine

43
Q

Medical problems associated with lateral folding:

Gastroschisis

A
  • a fairly common birth defect (1 in 2000 births)

- visceral organs, usually intestine, lie outside of the body wall

44
Q

Medical problems associated with lateral folding:

Ectopia Cordis

A
  • in very rare cases, folding of the body wall leaves the heart outside of the chest
  • this is usually lethal around birth, bot some individuals have survived beyond 30 years of age
45
Q

In response to signals from the adjacent tissues, the gut tube begins to differentiate into different visceral organs.

In the case of the liver, signals from what are required for initiation of the liver development pathway?

A

signals from the heart

*note that the developing heart and the endodermal tissue that will develop into liver are adjacent in the embryo

Foundations Week 8 (10 decks)

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