Development of the Skeletal System (embryology) Flashcards

1
Q

The caudal and rostral sections of the vertebral column fuse and become what?

A

vertebrae

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2
Q

What do spinal nerves grow between

A

vertebrae

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3
Q

What do growing spinal nerves innervate?

A

myotome

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4
Q

How many somites are there, and how many fuse to make cervical vertebrae?

A

8 original somites; 7 of them fuse.

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5
Q

Cervical spinal nerves exit ____ vertebrae of the same number. Others spinal nerves exit ____ vertebrae.

A

above; below

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6
Q

What do sclerotomes form around the developing spinal cord?

A

neural arches and the vertebral body.

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7
Q

As development progresses, the notchord regresses until it is only found where?

A

in the intervertebral discs.

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8
Q

What is congential scolosis?

A

abornmal lateral curvature of the spine caused by disruption of normal vertebral development.

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9
Q

Hemivertebrae (scolosis) results from what?

A

Failure of the vertebrae to fully form. Some vertebrae are smaller than others.

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10
Q

Block vertebrae/unsegmented bar (scolosis) results from what?

A

Failure of the vertebrae to fully segment. Some of the vertebrae are fused together.

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11
Q

Unsegmented bar with hemivertebrae (scolosis) results from what?

A

failure of formation AND segmentation; some vertebrae are fused and smaller than others.

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12
Q

Ribs arise from what zones?

A

zones of condensed mesenchyme lateral to the vertebra.

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13
Q

What region do ribs usually grow?

A

thoracic region; they can also grow in the cervical and lumbar regions.

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14
Q

What does the sterum develop from?

A

sternal bars in the ventral body wall; the sternal bars on the left and right side of the rib cage come to the midline and fuse together.

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15
Q

What does the sternum form?

A

manubrium body and xiphoid process.

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16
Q

what is pectus carinatum?

A

the overgrowth of cartilage causing th sternum to protrude.It is caused by the overgrowth of costal cartilage.

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17
Q

What is sternal formaen?

A

ossification in the sternum that looks like a bullet hole.

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18
Q

The positioning of the limbs is regulated by the expression of what genes?

A

hox genes

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19
Q

Limb outgrowth is initiated by what genes?

A

TBX5 (forelimb) and TBX4 (hindlimb)

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20
Q

What is meromelia? What amelia?

A

Partial (meromelia) or total absence (amelia) of the limbs.

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21
Q

What is phocomelia?

A

When the feet and hands arise close to the trunk

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22
Q

In mesomelia, which section of the arm is greatly shortened?

A

the forearm

23
Q

What is radial club hand?

A

Abnormality in the position of the hand and forearm. Some muscular and neural structures may not be present.

24
Q

What is the apical ectoderm ridge?

A

A region of the ectoderm that forms a ridge when limb outgrowth is inititaed by BMPs.

25
Q

Once the AER has formed, what other two regions form and assists in limb differentiaton?

A

the apical ectodermal ridge and the zone of polarizing activity.

26
Q

What occurs at the zone of polarizing activity?

A

the region tells the body where to put things, like fingers.

27
Q

What occurs at the progress zone?

A

mitosis and limb lengthening.

28
Q

What occurs at the AER?

A

limb bud organization and maintenance of the dorsal/ventral axes.

29
Q

After AER is established, what does it express?

A

FGF4 and FGF8; both maintain the progress zone. FGF4 and 8 allow for the mitosis and growth of cells in the region (and hence distal growth of the limb).

30
Q

The expression of what two genes at the zone of polarizing activity direct organization of the limb bud and patterning of digits?

A

Shh and Retinoic aid.

31
Q

If Shh and retinoic acid are misexpressed in the zone of polarizing activity, what can occur?

A

a mirror image duplication of limb structures results.

32
Q

Removal or addition of the AER to a developing limb results in what?

A

the absence of limbs or the duplication of a limb OR polydactyly.

33
Q

Polydactyly usually results in the growth of a finger or toe on what side?

A

lateral (not by the thumb or big toe).

34
Q

What does the zone of cell division contain?

A

a region of actively dividing cells.

35
Q

What does the zone of differentation contain?

A

a region of cell specialization.

36
Q

The cells closest to the AER become what structures?

A

distal structures; this is caused by the secretion of FGFs.

37
Q

Cells far from the AER become what structures?

A

proximal structures.

38
Q

What does thalidomide do?

A

Disrupts signaling from the AER to the progress zone; this causes limbs to be shortened or nonexistent.

39
Q

The ___ of cells removes the webbing between fingers and toes.

A

apoptosis

40
Q

What is syndactyly?

A

webbed fingers or toes due to failure of apoptosis.

41
Q

What is brachydactyly?

A

The development of short digits; it often results in short stature.

42
Q

What is cleft hand or foot?

A

lobster claw; it often results in the absence of one or more central digits.

43
Q

As the limb develops, how does it rotate?

A

90 degrees laterally, then 90 degrees medially.

44
Q

Many congential limb abnormalities are the result of what?

A

a combination of genetics and the environment.

45
Q

What is sirenomelia?

A

mermaid syndrome.

46
Q

What is achondroplasia?

A

dwarfism; it results form abnormalities at the epiphyseal plate and zones of proliferation. Bones do not grow correctly.

47
Q

What is brittle bone disease?

A

Fragile bones. It also inclues blue sclera in the eye

48
Q

What is talipes equinovarus (club foot)?

A

abnormal position of the foot caused by a lack of space in the uterus, whether by multiple fetuses or by a lack of amniotic fluid.

49
Q

How is club foot treated?

A

braces and sometimes surgery.

50
Q

A 13 year old male patient presents a depressed sternum. You determine that he has pectus carinatum. What has caused his condition?

A

overgrowth of cartilage in the costal region.

51
Q

You encounter a patient who exhibits photocmelia. What is her condition and what is it caused by?

A

She has limbs close to the trunk; it is caused by an abnormality in the zone of polarizing activity.

52
Q

In an embryology laboratory, you decide to study limb growth. You add an extra AER to a growing limb bud of a chick embryo. What will occur in the developing chick?

A

The chick will grow an additional limb.

53
Q

You encounter a patient who has a very short limb caused by thalidomide. How has thalidomide caused shortening of the limb?

A

Signaling between the AER and progress zone has been disrupted, and the progress zone stops mitotically dividing (and hence, growing more limb).