1. Fertilization
2. Cleavage
3. Gastrulation
4. Neurulation
5. Organogenesis

A major rearrangement of cells in which the outter blastulla cells move to the inside of the blastulla, and the embryo forms an endodermal gut with three layers:

1. ectoderm 2. mesoderm 3. endoderm

Amphibians/fish

A blastopore forms and the surface moves towards this and the cells turn inward.

The cells are spread along the inside of the outter cellls  then the blastocoel is displaced and the blastopore closes forming a yolk plug.

Blastopore becomes the anus and sets up ant/post axis.

1. Invagination at the the blastopore.

2. Formation of a primative node.

Birds (and placentals)

Cells migrate laterally forming a primative node at the post end which elongates and narrows; this forms a primative streak. A depression forms called the blastopore and the cells involute and move inwards. 

The streak regresses and "zips" closed Ant to Post on the dorsal side.

Formation of 3 germ layers.

Bilateral Symmetry (ant/post,dor/vent).

Formation of notochord from dorsal midline of mesoderm.

Forms from the mesoderm on the dorsal midline.

Helps establish the topography of the embryo along the A/P axis.

Determines the position of the nervous system and is required for the Nervous system differentiation.

Formation of the neural tube from the ectoderm.

1. Along dorsal side and A/P axis
2. Lateral margins of plate fold inward (neural folds)
3. Neural folds meet at midline and fuse.

Formation of organs and tissues that occurs because germ layers are established at gastrulation.

outter layer (blue)

skin/nervous system

middle layer (red)

skeleton, muscle, circulatory, reproductive

inner layer (yellow)

digestive, respiratory.

Formation of tissue from the germ layers.

4 types:

1. epithelial
2. connective
3. muscular
4. nervous

1. epithelial
2. connective
3. muscular
4. nervous

Formed of closely adjoined cells with very little extracellular matrix between them.

2 groups:

covering/lining and glandular

Specialized to secrete a product (gland)

Exocrine vs. Endocrine

Contractile tissue.

3 types: skeletal, cardiac, smooth

2 types:

Nerve Cells and glial cells

• Developmental only.
• Contribute to a variety of adult structures.
• Ectodermal or epidermal placodes.

 A distinct population of cells that separate from neural folds before they fuse.

Migrate along defined routes within the body, when they reach a permanent site, they differentiate into adult structures.

ex: Ganglia of spine and cranial nerves

Schwann cells

Adrenal Medulla (Chromattin cells)

Cartilege and bone of lower jaw

connective tissue of voluntary muscles.

Thickenings of surface ectoderm that sink inward to form specific sensory receptors.

Interact with the neural crest cells but still distinct.

All placodes (except optic->lens) become receptors.

Intrinsic membranes that arise from germ layers and grow around the developed embryo.

-The basic pattern of membranes is the same in all amniotes:

Four membranes

1. yolk sac (end and mes)
2. amnion (ect and mes)
3. allantois (end and mes)
4. chorion (ect and mes)

Formed in the mesoderm in early development and gets paritioned later in development.

Forms by entercoely

Pleuroperitoneal Cavity -> digestive system

Pericardial Cavity ->Heart

Transverse Septum separates these two.

Peritoneal Cavity -> abdomen

Pleural Cavity -> lungs

Pericardial Cavity -> Heart

Transverse septum is modified so the base is muscular (diaphragm forms)