Organogenesis

Question 1

Mesenchymal cells: ____1.____ (skeletal elements + other ____2.____ ) and ____3.____ ( ____4.____ + muscle + ____5.____ )

Answer 1

1. lateral plate mesoderm
2. connective tissues
3. somites
4. cartilage
5. partial vasculature

Question 2

In chick embryos, the first signs of limb development are around the ____1.____ day after ____2.____

Answer 2

1. third

2. the egg is laid

Question 3

The ____1.____ will form the mesodermal parts of the ____2.____

Answer 3

1. intermediate mesoderm

2. kidneys

Question 4

The ____1.____ will give rise to the ____2.____

Answer 4

1. anterior splanchnic mesoderm

2. heart

Question 5

The ____1.____ part of the lateral mesoderm will develop into the ____2.____ and ____3.____

Answer 5

1. ventral-most
2. vascular system
3. blood

Question 6

The dermomyotome gives rise to the ____1.____ (muscle)

Answer 6

1. myotome

Question 7

The ____1.____ migrates to form the cartilage of the vertebrae

Answer 7

1. sclerotome

Question 8

The somite is patterned by signals secreted by ____1.____

Answer 8

1. adjacent tissues

Question 9

The limb has three developmental axes: (what are they?)

Answer 9

1. proximo-distal axis
2. antero-posterior axis
3. dorso-ventral axis

Question 10

Thickening in the ectoderm: ____1.____ or ____2.____ …runs along the boundary between ____3.____ and ____4.____ ectoderm

Answer 10

1. apical ectoderm ridge
2. apical ridge
3. dorsal
4. ventral

Question 11

The ____1.____ part of the limb bud is the first to differentiate, and the differentiation proceeds ____2.____ as the limb bud grows out

Answer 11

1. proximal

2. distally

Question 12

The first sign of cartilage differentiation: increased local packing of the mesenchyme cells ( ____1.____ )

Answer 12

1. condensation

Question 13

T or F : during the growth phase, cartilage is replaced by bone

Answer 13

TRUE

Question 14

During the growth phase, ____1.____ is replaced by ____2.____

Answer 14

1. cartilage

2. bone

Question 15

Genes expressed in the lateral plate mesoderm (Hox, Pitx1, Tbx4, Tbx5…..) are involved in specifying the ____1.____ and ____2.____

Answer 15

1. position

2. type of limb

Question 16

T or F : transplantation experiments in chick embryos have shown that the lateral plate mesoderm becomes determined to form limbs in their positions, long before limb buds are visible

Answer 16

TRUE

Question 17

___1.___ is important (Tbx4 and Tbx5 control local production of ___2.___ that initiate limb development)

Answer 17

1. FGF

2. FGFs

Question 18

The apical ectodermal ridge is required for limb outgrowth and the formation of structures along the ____1.____ axis of the limb ….. and the key signal is provided by ___2.___

Answer 18

1. proximo-distal

2. FGFs

Question 19

T or F : FGF8 alone is not sufficient for normal limb development

Answer 19

FALSE (it is sufficient)

Question 20

Outgrowth of the limb bud involves ____1.____

Answer 20

1. oriented cell behavior

Question 21

When a well-defined apical ridge is present, the limb bud’s length along the proximo-distal axis (increases/decreases) about ____1.____ , while the dimensions of its ____2.____ and ____3.____ axes are almost unchanged

Answer 21

increases

1. three-fold
2. antero-posterior
3. dorso-ventral

Question 22

Cell proliferation is higher ____1.____ and near the ____2.____ . . . . but the bud growth has more to do with cell polarization and oriented cell movements, and cell division in the direction of the ____3.____

Answer 22

1. distally
2. ectoderm
3. apical ridge

Question 23

T or F : patterning of the limb bud involves positional information and how it is being specified is still a matter of debate

Answer 23

TRUE

Question 24

The developing chick limb bud behaves as if its future development is determined by the positions of its cells with respect to the main limb axes (the ____1.____ and the ____2.____ )

Answer 24

1. polarizing region

2. apical ectodermal ridge

Question 25

The ____1.____ or ____2.____ of a vertebrate limb bud has organizing properties almost as striking as those of the ____3.____ in amphibians

Answer 25

1. polarizing region 2. the zone of polarizing activity 3. Spemann organizer

Question 26

ZPA can specify positional information along the ____1.____ axis

Answer 26

1. antero-posterior

Question 27

____1.____ : any substance active in pattern formation whose spatial concentration varies and to which cells respond differently at different threshold concentrations

Answer 27

1. morphogen

Question 28

____1.____ is the ZPA morphogen

Answer 28

1. Sonic hedgehog (Shh)

Question 29

T or F : how digit identity is encoded was recently discovered

Answer 29

FALSE (it is not yet known)

Question 30

The dorso-ventral axis of the limb is controlled by the ____1.____ (in experiments, the proximal regions of the limbs that develop have ____2.____ polarity corresponding to that of the ____3.____ , whereas the distal regions have a reversed dorso-ventral axis, with the pattern of muscles and tendons reversed and corresponding to the ____4.____ polarity of the ____5.____ )

Answer 30

1. ectoderm 2. dorso-ventral 3. mesoderm 4. dorso-ventral 5. ectoderm

Question 31

Development of the limb is integrated by interactions between ____1.____ (by ____2.____ )

Answer 31

1. signaling centers | 2. feedback control

Question 32

T or F : different interpretations of the same positional signals give different limbs

Answer 32

TRUE

Question 33

Signals are interpreted according to the ____1.____ of the responding cells (if tissue that would normally give rise to the thigh is grafted from ____2.____ part of an early chick leg bud to the tip of an early wing bud, it develops into toes with claws)

Answer 33

1. origin | 2. proximal

Question 34

These results suggest that the limb bud might be able to generate a basic ____1.____ consisting of equivalent cartilaginous elements

Answer 34

1. prepattern

Question 35

A ____1.____ is a basic organization that is generated autonomously in the embryo and can be identified in advance of the latter development of a similar pattern of structures

Answer 35

1. prepattern

Question 36

T or F: The pattern that eventually develops does have to follow the prepattern exactly

Answer 36

FALSE (does not have to follow the prepattern exactly but may be a modified form of it)

Question 37

Limb muscle is patterned by the ____1.____

Answer 37

1. connective tissue

Question 38

T or F : the initial development of cartilage, muscles, and tendons is autonomous

Answer 38

TRUE