Mesoderm

Question 1

Generates all the ORGANS between the ectodermal wall and the endodermal tissues.

Second group of cells that will enter the primitive streak

Answer 1

Mesoderm

Question 2

For the mesoderm to be specified, it needs the endoderm and vice versa

Question 3

an early stage of embryonic development in triploblastic organisms, like humans, where the bilaminar disc (composed of two layers: epiblast and hypoblast) transforms into a three-layered structure containing ectoderm, mesoderm, and endoderm.

Answer 3

Trilaminar embryo

Question 4

During the process when the brain and spinal cord is being formed, the mesoderm is also undergoing differentiation

Question 5

During the differentiation, the mesoderm (1 layer) will start to be differentiated into segments

Answer 5

Axial mesoderm (notochord)
Paraxial mesoderm (somites)
Intermediate mesoderm
Lateral plate mesoderm

Question 6

Lateral plate mesoderm separates too become…

Answer 6

Somatic
Splanchnic

(in between is the coelom)

Question 7

Mesodermal Regions:

Answer 7

1. Chordamesoderm - give rise to the notochord
2. Paraxial mesoderm
   - Head mesoderm* - give rise to cranial and heart muscle; not segmented
   - SOMITIC - majority of the paraxial mesoderm will become somites; segmented
3. Intermediate mesoderm
4. Lateral plate mesoderm

Question 8

Serves as the primary inducer

Answer 8

Notochord

Question 9

one of the first tissues to gastrulate

Answer 9

Notochord

Question 10

Functions of notochord:

Answer 10

1. Establish AP axis
2. Induce DV (dorsoventral) patterning of NT (neural tube)
3. Induce ventral somitic fates
4. Induce pancreas growth

Question 11

Notochord releases _____, a signaling factor that induces the neural tube to undergo differentiation, to the neural tube floor plate and to the sclerotome

Key morphogen that will help regulate organogenesis

Also critical for the development of motor neurons

Answer 11

Shh

Question 12

gives rise to cranial muscle and contributes to the skull and heart

Answer 12

Embryonic head mesoderm

Question 13

The head mesoderm markers:

Answer 13

Pitx2
Alx4
MyoR
Tbx1

Question 14

Major subdivisions of the mesoderm

Answer 14

1. Paraxial mesoderm (somitic mesoderm)
2. Intermediate mesoderm
3. Lateral plate mesoderm

Question 15

Major lineages of vertebrate mesoderm

Intermediate mesoderm becomes…

Answer 15

Kidney and Gonads

Question 16

Major lineages of vertebrate mesoderm

Chordamesoderm becomes…

Answer 16

Notochord -> Intervertebral disk

Question 17

Major lineages of vertebrate mesoderm

Paraxial mesoderm becomes…

Answer 17

Head and Somite

Somite becomes Sclerotome or Dermomyotome

Sclerotome becomes…
1. Vertebrae and ribs
2. Endotome (endothelial cells, dorsal aorta)
3. Arthrotome (vertebral joints)
4. Syndetome (tendon)

Dermomyotome becomes…
1. Myotome (skeletal muscle)
2. Dermatome (dermis, skeletal muscle)

Question 18

Major lineages of vertebrate mesoderm

Lateral plate mesoderm…

Answer 18

1. Splanchnic
2. Somatic
3. Extraembryonic

Question 19

Major lineages of vertebrate mesoderm

Answer 19

Intermediate mesoderm
Chordamesoderm
Paraxial mesoderm
Lateral plate mesoderm

Question 20

Also called Epimere, Mesomere, and Hypomere

Answer 20

Somite mesoderm
Intermediate mesoderm
Lateral plate and ventral mesoderm

Question 21

Components of the Paraxial (Somite) Mesoderm:

Answer 21

1. Dermatome : dermis of skin
2. Myotome : axial, limb, and body wall musculature
3. Sclerotome : vertebral column and ribs

Question 22

Formation of Somites from mesoderm iis called

Answer 22

somitogenesis

Question 23

Direction of somitogenesis

Answer 23

Cranial to caudal

Question 24

Human first somites (Week 4; Carnegie stage 9)

Question 25

Formation of somites Shape: like a ball, covered by epithelial cells, inside mesenchymal cells Process: 1 pair of somites form during a species-specific time frame Appear in pairs and are identical in size

Question 26

Somite number in humans

Answer 26

42-44

Question 27

Somite number in chicken

Answer 27

50

Question 28

Somite number in mouse

Answer 28

65

Question 29

Somite number in Xenopus

Answer 29

42

Question 30

Somite number in Zebrafish

Answer 30

32

Question 31

Somite number in snakes

Answer 31

500

Question 32

Transcription factors in dermatome

Answer 32

Pax-3; Pax-7

Question 33

Transcription factors in Sclerotome

Answer 33

Pax-1; Pax-9

Question 34

Transcription factors in myotome

Answer 34

FGF8

Question 35

Central region forms muscle, muscle stem cells, dermis, brown fat cells

Answer 35

Dermatome

Question 35

Myotome (muscle) with FGF forms sclerotome and when Shh is expressed, it becomes a cartilage

Question 36

Dorsal region forms tendons (syndetome) Medial region forms blood vessels and meninges Central mesenchymal region forms joints (arthrotome) Forms smooth muscle cells of dorsal aorta

Answer 36

Sclerotome

Question 37

Fate of the Intermediate Mesoderm

Answer 37

Nephric/Excretory System - Pronephros - Mesonephros - Metanephros Genital System - Ducts - Gonads

Question 38

Derivatives of the Lateral Plate Mesoderm

Answer 38

1. Somatic mesoderm: - bones - ligaments - blood vessels - CT of the limbs 2. Splanchnic mesoderm: - heart - visceral layer of BV - smooth muscle - CT of respiratory and Digestive organs

Question 39

Specification and migration of cardiac cells in chick embryo

Answer 39

Cardiogenic mesoderm becomes... 1. Endocardial enthothelial cell -> Cushion cell 2. Atrial myocyte 3. Ventricular myocyte -> Purkinje fiber

Question 40

Mesodermal derivatives mostly exhibit segmentation Humans are segmented animals: vertebrae, ribs, musculature Segmentation is most obvious in mesodermal derivatives Somites : sclerotome, myotome and dermatome