psyc 221 chapter 3

zona pellucida

The thin envolope that surrounds the zygote and later the morula

germinal period

The peroid that begins at conception and lasts unitll the developing organiam becomes attached to the wall fo the uterus about 8 to 10 weeks

Embryonic period

The peroid that extends from the time that the organiism becomes attached to the uterus untill the end of the major organs have taken primitive shape.

fetal period

This period begins the ninth week after conception, with the first signs of the hardening of the bones, and continues until birth.

cleavage

The series of mitotic cell divisions that transforms the zygote into the blastocyst.

heterochrony

Variability in the rates of development of diffrent parts of the organism

Heterogeneity

Varirability in the levels of develpment of diffrent parts of the organism at a given time

morula

The cluster of cells inside the zona pellucida

stem cells

The calls of the morula, every one of which has the potential to grow into an embryo and a normal healthy baby

blastocyst

The hollow sphere of cells that results from the diffrentiation of the moula into the trophoblast and the inner cell mass

inner cell mass

The collection of cells inside the blastocyst that eventually becomes the embro

trophoblast

The outer layer of the colls of the blastocyst that develop into the membranes that protect and support the developing organism

epigenesis

The process by which a new form emerges through the inertcations of the preceding form and its current enviroment

implantation

The process by which the blastocyst becomes attached to the uterus

amnion

a thin, though trasparent membrane that holds the amniotic fliud

chorion

One of the membranes that develops out of the trophoblast. It forms the fetal component of the placenta

chorion

One of the membranes that develops out of the trophoblast. It forms the fetal component of the placenta

placenta

An organ made up of tissue from both the mother nad the fetus that serves as a barrier and filter between their bloodstreams

umbilical cord

A soft tube containing blood vessels that connects the developing organism to the placenta

ecdoderm

Cells of the inner cell mass that develop into the digestive system and the lungs

ectoderm

cells of the inner cell mass that develop into the outer surface of the skin, the nails, parts of the teeth the lens of the eye, the inner ear, and the central nervous system

mesoderm

the cells of inner cell mass that given rise to the muscles, the bones the circulatory system and the inner layers of the skin.

cephalocaudal pattern

The pattern of development that procedes from the head down

proximodistal pattern

the pattern of development the procedes from the middle of the organism out the periphery

low birth weight

The term used to describe babies weighing 2500 grams or less at birth whether or not they are premature

teratogens

Enviromental agents that cause deviation from noraml development and can lead to abnomalities or death

apgar scale

a quick simple test to diagnose the physical state of the newborn infants

Brazelton Neonatle Assesment scale

A scale use to assess the newborn's neurological condition

gestational age

the time that has passed between conception and birth. the normal age is 37 and 43 weeks

preterm

babies born before the 37 week pregnency

fetal growth retardation

newbrons who are especially small for their gestaitonal age