Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MD2002 > Development of the Limbs > Flashcards

Development of the Limbs Flashcards

1
Q

With reference to a limb, what is meant by pentadactyl?

A

5 digits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

When do primary ossification and secondary ossification occur?

A

Primary takes place pre-birth (i.e. @ embryonic stage)

Secondary ossification centres arise @ birth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

List the stages of endochondrial ossification from mesenchyme to mature bone.

A

Mesenchyme –condensation–> cartilage surrounded by mesenchyme —> primary ossification centre (@ 12 weeks), proliferating chondroblasts, osteoblasts & angiogenesis —> secondary ossification centres and growth plates develop

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How can radiologists determine the skeletal age of a patient?

A

Examining epiphyseal plate development

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is meant by intramembranous ossification?

A

The formation of bone in fibrous connective tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is fibrous connective tissue formed from?

A

Condensed mesenchyme cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

When does intramembranous ossification occur?

A

During the formation of flat bones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

The limbs undergo rotation during embryonic development. After how long does this happen and to what degree, in which direction do the limbs rotate?

A

Week 7
FORElimbs rotate 90 degrees LATERALLY
HIND limbs rotate 90 degrees MEDIALLY

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does this rotation result in with regard to muscle compartments in the limbs?

A

Flexor compartment anterior in upper limb and posterior in lower limb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

When do upper limb buds appear?

A

Day 24

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

When do lower limb buds appear?

A

Day 28

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Between which somites do upper limb buds appear?

A

C5 - T1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Between which somites do lower limb buds appear?

A

L1 - S2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How long is it before all major compartments of the limbs are present?

A

By week 8

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the function of HOX genes?

A

To control limb development

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Where are HOX genes expressed?

A

Along the long axis of the embryo - from head to tail; each number HOX gene follows the body plan, i.e. 1 is most superior, 13 is most inferior

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which class of proteins do HOX genes belong to?

A

Transcription factors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the function of transcription factors?

A

Bind to DNA and regulate the transcription of other genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

During embryonic development, what two things do HOX genes determine?

A

Body axis

Position of the limbs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Which three axes is limb growth regulated along?

A

Proximo-distal axis
Antero-posterior axis
Dorso-ventral axis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is another name for the antero-posterior axis?

A

Cranio-caudal axis

22
Q

Standard meanings of anterior & posterior and dorsal & ventral are very similar. How does this vary in embryology?

A 
Anterior = lateral
Posterior = medial
Ventral = anterior
Dorsal = posterior
23
Q

What is proximo-distal development controlled by?

A

APICAL ECTODERMAL RIDGE (AER)

24
Q

Where is the core of mesenchyme derived from?

A

Lateral plate mesoderm

25
Q

Where is the AER located and what forms it?

A

Ectoderm thickened at the apex of developing limb —> AER

26
Q

The AER induces the underlying tissue to remain as a population of undifferentiated, rapidly proliferating cells. What is this area known as?

A

The PROGRESS ZONE

27
Q

How does cell differentiation come about if AER disallows it then?

A

As the AER progresses, it leaves cells behind; the further the AER travels away from these cells, the less of an influence it has over them , leaving them free to differentiate into cartilage and muscle

28
Q

What controls the position of the limb on the long axis of the body?

A

HOX-8

29
Q

What initiates growth of the fore-limbs

A

TBX5 & FGF-10

30
Q

How is the progress zone maintained and development of the proximo-distal axis furthered?

A

FGF4 & FGF8

31
Q

What are FGF4 & FGF8 examples of?

A

Growth factors

32
Q

What controls the anterior-posterior/cranio-caudal axis?

A

ZONE OF POLARISING ACTIVITY (ZPA)

33
Q

Where is the ZPA located?

A

Near the posterior border of the limb

34
Q

With respect to the hand, what does the ZPA ensure?

A

That the thumb goes on the anterior (cranial) side of the limb bud

35
Q

What initiates growth of the hind limbs?

A

TBX4

36
Q

What protein specifically does the ZPA express?

A

Sonic hedgehog protein

37
Q

In which direction does the ZPA move?

A

Distally, with the AER

38
Q

If another ZPA were to be added to the limb bud, what would be the effect on the limb?

A

Mirror image duplicates of the digits would arise

39
Q

The doors-ventral axis determination involves EN1, LMX1, BMPs,& WNT7. Describe the sequence of events that occur resulting in certain cells being specified as being dorsal.

A

BMPs in ventral ectoderm induce/activate EN1
EN1 represses WNT7, restricting its expression to dorsal limb ectoderm
WNT7 induces/activates LMX1 which specifies cells to be dorsal

40
Q

How is it that the upper and lower limbs are developed differently and patterns for proximal, middle and distal sections of limbs are defined?

A

Variations in the combinations of HOX genes ensure these differences

41
Q

How is it that humans don’t have webbed hands or webbed feet?

A

Programmed cell death is brought about between digits

42
Q

Define amelia.

A

Complete absence of the limbs

43
Q

Define meromelia.

A

Partial absence of the limbs

44
Q

Define phocomelia.

A

Absence of long bones

45
Q

Define micromelia.

A

Segments are abnormally short

46
Q

Briefly summarise the Thalidomide tragedy.

A

Between 1957 & 1962, thalidomide was prescribed as a sleeping pill - increase in limb abnormalities was reported in newborns

47
Q

Which element of limb development did thalidomide target?

A

The Progress Zone

48
Q

What is Holt Oram Syndrome?

A

TBX5 mutation —> failure of upper limb bud development

Also associated with heart defects

49
Q

Define brachydactyly.

A

Short digits

50
Q

Define syndactyly.

A

Fused digits - failure of apoptosis

51
Q

Define polydactyly.

A

Extra digits

MD2002 (27 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions