Embryonic Body Plan

Front 1

List the tissues that compose the buccopharyngeal and cloacal membranes and identify their locations in the trilaminar embryo.

Back 1

• Buccopharyngeal membrane- composed of ectoderm and endoderm; located at cranial end; the buccopharyngeal membrane represents the future opening of the oral cavity
  

• Cloacal membrane- composed of ectoderm and endoderm; located at the caudal end; the cloacal membrane marks the site of the future distal end of the gastrointestinal (GI) and genitourinary (GU) tracts.
  

Front 2

List the major derivatives of the ectoderm, endoderm and mesoderm, including paraxial, intermediate and lateral plate mesoderm, as outlined in the resources.

Back 2

Front 3

Describe the formation of the notochord and its function in neurulation.

Back 3

• The notochord (derived from mesoderm) is formed by primitive node cells that either followed those of the prechordal plate through the primitive pit, or were deposited in the wake of the receding primitive streak.
  
• The notochord through differentiation signals (inductive signals) causes the differentiation of neural tissue from ectoderm to form a neural plate on the dorsal side of the embryo.
  

Front 4

Describe the process by which the neural tube closes.

Back 4

• Soon after neural plate formation, the lateral edges of the plate elevate (thus forming the neural folds), approach one another in the midline and fuse to form the neural tube. The neural tube subsequently dissociates entirely from the overlying ectoderm.
  

Front 5

Diagram and describe cranial-caudal folding. What drives caudal folding? What does caudal folding bring into the body? Cranial?

Back 5

Front 6

Diagram lateral folding. What drives this folding?

Back 6

Front 7

Predict the consequences of neurluation defects. What congenital abnormalities are associated with failure of neural tube to close?

Back 7

Front 8

Predict the consequences of cranial-caudal or lateral folding defects

Back 8

• Major defects --> embryonic lethal.
  
• Critical in the formation of the structures that facilitate the movement and exchange of amniotic fluid,
  
• Disorders of amniotic fluid (polyhydramnios-too much fluid, and oligohydramnios-too little fluid) may be due to defects in folding.
  

Front 9

Predict the consequences of defects in neural crest cell migration.

Back 9

• Anything that points to peripheral glial cell abnormalities, pigmentation abnormalities (at the cellular level, not something like albinism), abnormalities in adrenal medulla function, problems in the connective tissues of the head and
  

• Hirschsprung Disease: failure of neural crest cells to migrate to the wall of the developing large intestine, resulting in aganlionic megacolon
  
• Treacher Collins syndrome or DiGeorge syndrome; result from malformation of the pharyngeal arches
  

Front 10

Diagram neural crest cell formation.

Back 10

Front 11

Diagram/describe neural tube closure.

Back 11

Front 12

Give an overview of Gastrulation. What the relationship between the amniotic cavity and the chorionic cavity? Though what structure do the mesoderm and endoderm migrate? IN what order?

Back 12

Front 13

What are the four subdivision of the mesoderm and what do they give rise to?

Back 13

Front 14

Diagram/Describe early mesoderm organization. Identify the Buccopharyngeal and Cloacal membranes. What do they give rise to? What germ layer tissue is excluded from those structures?

Back 14

Front 15

Diagram the 4-week-old embryo

Back 15

Front 16

Diagram the axial mesoderm. Identify the pericardial plate and the notochord. What are their respective functions?

Back 16

Front 17

Diagram/ describe the pre-cardiac mesoderm. To ward which structure does it migrate does it migrate?

Back 17

Front 18

Describe the non-axial mesoderm. Describe the structures and from where the originate. From where are germ cells derived?

Back 18

Front 19

Which layer does not go through the primitive streak. What structure/region signals it to develop?

Back 19