Comparative Anatomy Chapter 2

Blastocyst

early stage of embryo described as a “ball of cells”

Cleavage

division of cells from the egg/zygote

Radial cleavage

cells are aligned as they divide

Spiral cleavage

cells are offset from each other

Gastrulation

cells growing inward (invagination); these indented cells become the gut and continue until they reaches the other wall, and then they usually break through and form a second opening

Blastopore

first opening into the indentation of gastrulation

What are the layers that form after gastrulation?

1) Ectoderm

2) Endoderm

3) Mesoderm

4) Coelom

5) Schizocoelom

6) Enterocoelom

Ectoderm

Outer layer

Endoderm

inner layer that forms the lining of the gut

Mesoderm

middle layer between the ectoderm and endoderm

Coelom

Internal body cavity

Schizocoelom

body cavity made from solid mass of mesodermal cells splitting

Enterocoelom

body cavity forming from the outpocketing of the gut that pinches off

What are the parts of the protosomes?

What are the parts of the deuterosomes?

What is a chordate?

What are the characteristics of chordates?

What is a notochord?

A slender rod that forms from the mesoderm that is dorsal to the coelom and ventral of the nerve cord; a hydrostatic organ

Hydrostatic organ

Outer fibrous sheath encloses incompressible fluid that prevents axial compression

What is the structure of notochords?

Composed of a core of cells and fluid encase in a tough fibrous tissue sheath

What is the function of notochords?

Essential for vertebrate development as it signals the formation of the nerve cord.

Pharyngeal slits

Used for filter feeding

Dorsal Hollow Nerve Cord

Endostyle

Glandular groove in the floor of the pharynx used in filter feeding; involved in iodine metabolism

Thyroid gland

Produces thyroid hormones and calcitonin; involved in iodine metabolism

Postanal Tail

Myomeres

Blocks of serially repeated muscles that run the length of the adult body and tail