Body plan, neurulation, coelomic cavities

Question 1

What does the ectoderm become?

Answer 1

• Neuroectoderm
• Surface ectoderm

Question 2

What does the mesoderm become?

Answer 2

Transforms into paraxial, intermediate, and lateral plate mesoderm

Question 3

What does the endoderm become?

Answer 3

Gut tube and respiratory tract

Question 4

Formation of the primitive streak to neurulation (Changes in the ectoderm)

Answer 4

1. Ectoderm proliferates to form the neural plate/neuroectoderm
2. Neural plate to neural groove
3. Neural groove to neural tube which gives rise to the brain and spinal cord. Peripheral nervous system from neural tubes and neural creast cells (migrated neuroectoderm cells)
4. Induction leads to thickening of the surface ectoderm cells to form placodes, which give rise to nasal chambers, lens of the eye, inner ear, cranial nerves

Question 5

Neurulation

Answer 5

Folding of the neural plate into a neural tube

An example of the roles of gene regulatory networks in development

The dorsal-ventral patterning of neural tube requires two primary signalling senses:

1. Surface ectodermal cells- secrete bone morphogenetic protein (BMP-4 and BMP-7) so some ectodermal cells become roof plate of tube
2. Notochord- sonic hedgehog (Shh) signaling from notochord produces floor plate of tube

Question 6

Neurula

Answer 6

Embryo at the neurulation stage

Question 7

Changes in mesoderm

Answer 7

Type is based on its location
Three types:

1. paraxial mesoderm
2. intermediate mesoderm
3. lateral mesoderm

Question 8

Paraxial mesoderm

Answer 8

• Gives rise to aggregation of cells called somitomeres near the neural plate, and somites in the caudal region
• Somitomeres give rise to structures in the head region and somites form the axial skeleton

Question 9

Intermediate mesoderm

Answer 9

Form the reproductive and urinary systems

Question 10

Lateral mesoderm

Answer 10

• Forms the somatopleure and splanchnopleure which eventually line the space in between that later turn into the body cavities
• From the mesodermal lining, a simple squamous epithelium develops, and it is called the mesothelium.
• Mesotheloum forms the serous membranes that line the body cavities (pleura, peritonium, pericardium)

Question 11

Somitomeres and somites

Answer 11

Somitomeres give rise to structures in the head region and somites form the axial skeleton

Question 12

Somites

Answer 12

Give rise to the axial skeleton

Question 13

Somatic mesoderm

Answer 13

The mesoderm near the ectoderm

Question 14

Splanchnic mesoderm

Answer 14

The mesoderm near the endoderm

Question 15

Somatopleure

Answer 15

Ectoderm and somatic mesoderm combined

Question 16

Splanchnopleure

Answer 16

Endoderm and splanchnic mesoderm combined

Question 17

What is the origin of connective tissue?

Answer 17

Mesodermal

Question 18

Changes in Endoderm

Answer 18

Gives rise to the epithelium of the gut and respiratory tract and their glands, urinary bladder, middle ear, and auditory tube, liver, pancreas, thyroid and parathyroid glands

Question 19

Organogenesis

Answer 19

Formation of organs

Question 20

Steps of coelomic cavities formation

Answer 20

1. Clefts form within the right and left lateral mesoderm
2. Clefts coalesce, forming a cavity that splits the lateral mesoderm into an outer layer of somatic mesoderm and inner layer of splanchnic mesoderm
3. Cavity between these two layers forms the coelomic cavities
4. Lateral folding of the embryonic coelomic cavities give rise to pericardial, pleural, and peritoneal cavities

Question 21

Pleural and pericardial cavity formation

Answer 21

1. First formed as a pleuro-pericardial cavity that covers the embryonic/developing lungs and heart
2. Further development and folding of the mesoderm leads to formation of pleural and pericardial cavities

**Pleural cavities are separated by mediastinum

**Both kept within the thoracic cavity

Question 22

Mediastinum

Answer 22

Mesenchymal tissue that forms a septum separating the pleural cavities

Question 23

Function of pleura

Answer 23

Protection of lungs

Question 24

Function of pericardium

Answer 24

Protection of heart

Question 25

Diaphragm function

Answer 25

• Structural partition of the thoracic and abdominal cavities
• Allows structures such as blood vessels and nerves to pass through the 3 different sites

Question 26

Parts that play a role in the formation of the diaphragm

Answer 26

• Septum transversum (aggregation of mesoderm)- mesoderm becomes the muscular structure of diaphragm
• Pleuroperitoneal folds
• Mesothelial folds

Question 27

Peritoneal cavity

Answer 27

The mesothelium lining of the abdominal cavity

Question 28

Intra-peritoneal

Answer 28

Organs enclosed by a fold of the peritoneum

Question 29

Retro-peritoneal

Answer 29

Organs partly covered by the peritoneum

Question 30

Omentum

Answer 30

Fold of the peritoneum that attaches an organ to the stomach