Vertebrate Development

Question 1

What is gastrulation?

Answer 1

Cell migration that leads to the development of germ layers
- Amphioxus (vertebrate common ancestor): develops germ layers by folding the whole embryo

Question 2

Amphioxus - elongation and tissue movement through cell division

Answer 2

• Dividing mesoderm cells accumulate up and around the blastopore -> end up on the dorsal side surrounding the blastopore next to the notochord
• Notochord moves laterally and squishes blastopore in the middle until the blastopore is on the ventral side

Question 3

Tubes and segments form through folding, sealing, and pinching off

Answer 3

Internal folds/pinch-offs make 3 major types of tubes (mesoderm, neural tube, and gut)

Question 4

Describe process of folding/sealing/pinching off

Answer 4

• Endoderm begins curve towards itself and the notochord comes towards that curving (ventrally)
• Mesoderm (on lateral sides and just dorsal to endoderm) begins to fold onto itself to make somites
• Notochord and endoderm then attach and pinch together further all while the neural plate moves ventrally and starts to pinch itself dorsally
• Notochord and endoderm pinch off forming gut (endoderm) and the notochord remains attached to the endoderm dorsally
• The neural plate forms the neural tube dorsal to the notochord
• Somites spread laterally and ventrally

Question 5

Mesoderm segment (somite)

Answer 5

• Formation occurs anterior to posterior
• Neural tube stays open for now

Question 6

Vertebrate development added complexity is?

Answer 6

• Amphibian blastula has yolk-filled endoderm precursor
• Develops germ layers through involution

Question 7

Describe vertebrate development process with that added complexity

Answer 7

• Cells near animal pole migrate faster, resulting in the blastopore moving dorsally
• Mesoderm precursors form near the ventral lip of the blastopore
• Notochord precursor cells travel along the outer surface (ectoderm), dive into the blastopore, and then travel along the inner surface
• Mesoderm travels all over lateral and ventral inner surfaces

Question 8

Vertebrate Neurulation

Answer 8

Produces neural crest cells that migrate all over the body, where they go to initiate the development of body systems and become part of them. Unique to vertebrates.

Question 9

Mesoderm division (parts and what they become)

Answer 9

• Intermediate mesoderm: reproductive and kidney systems
• Paraxial mesoderm: skin/skeletal/skeletal muscle formation
• Somatic lateral plate mesoderm: body cavity linings and limbs or fins
• Splanchnic lateral plate mesoderm: associates with endoderm to become gut, also becomes circulatory system

Question 10

Disk-shaped embryos follow the same steps - gastrulation, folds, and segment

Answer 10

• Reptiles, birds, and mammals start with a disk-shaped embryo
• Primitive streak: groove where cells dive into embryo on dorsal side
• 3 layers stacked on each other after

Question 11

Ectoderm becomes:

Answer 11

• Skin, feathers, scales
• Brain and spinal cord

Question 12

Paraxial mesoderm becomes:

Answer 12

• Skeleton
• Skeletal muscle

Question 13

Intermediate mesoderm becomes:

Answer 13

• Urinary system
• Reproductive system

Question 14

Splanchnic mesoderm becomes:

Answer 14

• Associates with endoderm to become the digestive system
• Heart and circulatory system

Question 15

Endoderm becomes:

Answer 15

• Digestive system
• digestive and respiratory linings

Question 16

Neural crest

Answer 16

• Critical for head and pharynx development
• Travel throughout body in 3 major streams: anterior to posterior: 1) Trigeminal (around eye) 2) Hyoid 3) Branchial