Lecture 10: Early Embryonic Development

Question 1

Terratogen

Answer 1

Any agent or factor that can cause congenital abnormalities in an embryo or fetus

Question 2

5 common terratogens

Answer 2

• Genetic factors
• Radiation
• Hormones
• Chemical agents
• Infectious agents

Question 3

Teratogenic influence at predifferentiation stage

Answer 3

Embryo dies

Question 4

Teratogenic influence at organogenesis stage

Answer 4

Structural defects (embryonic period)

Question 5

Teratogenic influence at fetal growth stage

Answer 5

Affects functional maturation

Question 6

Single cell

Answer 6

zygote

Question 7

Compact mass of cells

Answer 7

Morula

Question 8

Fluid filled cyst with cells at periphery

Answer 8

Blastula

Question 9

`Bilaminar disc

Answer 9

early gastrula

Question 10

Trilaminar disc to tube shape

Answer 10

late gastrula

Question 11

Zygote

Answer 11

• Large (160 um)

- Divisions occur in uterine tube, resulting in blastomeres

Question 12

Is there an increase in size during blastogenesis?

Answer 12

No. Compaction occurs as the cell divides.

No increase in overall size o embryo while inside zone of pellucida

Question 13

Trophoblasts will form

Answer 13

part of placental membranes

Question 14

Embryoblasts will form

Answer 14

• the entire embryo
• forms the bilaminar disc of the epiblast and hypoblast
• establishes dorsal and ventral axis

Question 15

Epiblasts give rise to

Answer 15

Ectoderm

Question 16

Hypoblast gives rise to

Answer 16

Endoderm

Question 17

Ectoderm gives rise to

Answer 17

Epithelium
Nervous tissue
Neural crest cells

Question 18

Endoderm

Answer 18

Epithelium of digestive and respiratory systems

Question 19

Mesoderm gives rise to

Answer 19

Connective tissues
Muscle tissues
Cardiovascular system
Urogenital tract
Endothelium
Mesothelium

Question 20

What layers is the epithelium derived

Answer 20

All three (ecto, meso, and endoderm)

Question 21

Gastrulation is a formation of

Answer 21

a three layered embryo

Question 22

Gastrulation begins with

Answer 22

the formation of the primitive streak in the epiblast.

Cranial-caudal axis established

Question 23

How is the primitive streak formed?

Answer 23

• Epiblast cell migrate towards primitive streak and form the ectoderm
• Hypoblast/endoblast cells replaced to form the primary endoderm
• Mesoderm is also formed from cells migrating from the primitive streak

Question 24

Notochord

Answer 24

Cluster of cells derived from the mesoderm, determines axis of embryo and required to signal neural tube formation.
Transient embryonic midline structure in vertebrates

Question 25

6 Mesoderm inductive effects

Answer 25

1. Forms notochord
2. Notochord induces ectoderm to form neural tissue
3. Neural tube and neural crest cells formed
4. Some somites seen
5. Lateral, cranial, caudal body folds create the head, tail, primitive anus and mouth
6. Nervous system defined

Question 26

Where is the presumptive notochord located

Answer 26

in or above the endoderm but of mesodermal origin

Question 27

4 steps of neural tube formation

Answer 27

1. Neural ectoderm thickens
2. Neural folds dip down, producing the neural groove
3. Neural folds contact, neural ectoderm cells rearrange
4. The neural tube is formed

Question 28

Axial mesoderm gives rise to

Answer 28

Notochord

Question 29

Paraxial mesoderm gives rise to

Answer 29

Somites

Question 30

Intermediate mesoderm gives rise to

Answer 30

Genital systems

Urinary system

Question 31

Lateral plate mesoderm gives rise to

Answer 31

Somatic and splanchnic mesoderms

Question 32

Somites

Answer 32

Division of animals body giving rise to muscle, cartilage, tendons, dermis (limbs, vertebrae)

Question 33

Three somites

Answer 33

Dermatome - dermis
Myotome - muscle
Schlerotome -cartilage, tendons, endothelia

Question 34

Cranial part of neural tube

Answer 34

brain

Question 35

Caudal part of neural tube

Answer 35

spinal cord

Question 36

Neural crest cells

Answer 36

Transient, multipotent migratory cell population unique to vertebrates that gives rise to a diverse cell lineage, including melanocytes, craniofacial cartilage, and bone