Chapter 3 Flashcards
Pre-Natal Period
Conception to Birth ~38 weeks
Embryonic period
1st 8 Weeks of development
Organs form from 3 Germ layers
Basic body plan emerges
Fetal period
Last 30 weeks of development
Organs grow in size and complexity
Conception
Sperm meets oocyte in lateral third of uterine tube and fuse to become zygote
Gastrulation
Cells migrate toward the primitive streak and form 3 germ layers: Endoderm, mesoderm, and ectoderm
Neurulation
Ectoderm starts forming brain and spinal cord while mesoderm starts differentiating
Folding
Embryo undergoes two folds: lateral and head-tail folds to establish body plan
Trophoblast
Outer wall of blastocyst; Becomes placenta
Hypoblast
Lower layer of bilaminar disc; Becomes yolk sac and later primitive gut and digestive tube
Ectoderm
Top layer from epiblast
Goes on to become brain and spinal cord, sensory neurons, melanocytes, and epidermis
Endoderm
Bottom layer of epiblast; Displaces hypoblast
Goes on to become inner epithelial lining and glands and secretory cells
Notochord
Mesoderm directly under the primitive node; defines body axis on sagittal plane
Dictates growth of vertebral column and found in intervertebral discs
Somite
Derived from paraxial mesoderm; body’s first evidence of segmentation
Goes on to become vertebrae, ribs, dorsal dermis, and trunk and limb muscles
Intermediate mesoderm
Mesoderm lateral to the somites that are influenced by their segementation
Go on to become kidneys and gonads
Lateral plate
Most lateral mesoderm; remains unsegmented
Becomes cavity lining around coelom
Forms ventral dermis, connective tissue, serosa, and heart and blood vessels
