Development (29)

Gradual modification of anatomical structures and physiological characteristics from fertilization to maturity

Differentiation

Occurs through selective changes in genetic activity

conception/when development begins

Occurs during weeks 0-3

What occurs during pre-embryonic development

evolution of development

rupture of mature follicle and release of egg

zygote goes through cell division

sets stage for formation of vital embryonic structure

embryo transforms from a one-dimensional layer of epithelial cells, a blastula, and reorganizes into a multilayered and multidimensional structure called the gastrula

Occurs during fisrt two months after fertilization

Begins at start of ninth week and contunues at birth

fertilization

what does fertilization produce

gestation

Has three trimesters

Period of embryonic and early fetal development

rudiments of all major organ systems

Stages of first trimester

formation of viable embryo - establishes foundations for all major organ systems

most dangerous period in prenatal life (40% survival)

Identical cells produced by cleavage divisions

stage three days after cleavage

pre-embryo

Hollow ball wiht inner cavity fromed by blastomeres

outer layer of cells seperate outside world from blastoceole - provide nutrients to developing embryo

clustered at end of blastocyst - will later form embryo

occurs 7 days after fertilization

formation of germ layers

3 germ layers

superficial cells that DID NOT migrat into interior of inner cell mass

consists of cells that face the blasteole

consists of poorly organuzed layer of migrating cells between endo and ecto derm

migrating cells leave surface and move between two existing layers

endodermal contributions

mesodermal contributions

ectodermal contributions

membranes that dissapear at birth

types of extraembryonic membranes