Module 4

Module 4—From Fertilization to Birth

Module Glossary

 

Consult the glossary in the textbook for other definitions that you may need to complete your work.

 

allantois: extra-embryonic membrane that forms the foundation for the umbilical cord, which connects the fetus with the placenta

 

amnion: extra-embryonic membrane that is a closed, fluid-filled sac surrounding the fetus; protects the fetus from impact and temperature change

 

blastocyst: embryonic stage that results when the morula hollows out; the outer layer is the trophoblast and becomes the chorion; the inner cell mass becomes the embryonic disc

 

Caesarean section (C-section): a surgical procedure in which the fetus is removed from the abdomen through an incision; used when vaginal birth is difficult or impossible

 

chorion: outermost layer of the embryo; develops from the trophoblast layer of the blastocyst; will form the fetal blood pool of the placenta

 

cleavage: cell division in which the zygote divides into smaller, identical cells, called blastomeres, without increasing the total size of the cell mass

 

colostrum: a rich, yellow secretion from the mammary glands that occurs for two to three days prior to the first secretion of milk; contains mother’s antibodies to protect the newborn from disease

 

contractions: the rythmic shortening of the muscles of the uterus to expel the fetus

 

differentiation: the turning on and off of genes in a cell; results in specialized cell functions

 

dilation: the opening of the cervix to allow passage of the baby

 

dilation stage: the stretching and opening of the cervix to 10 cm to allow passage of the fetus during expulsion

 

dizygotic twins: twins that form when two eggs are fertilized by two sperms; also known as fraternal twins; may be of different sexes

 

ectoderm: germ layer that forms hair, nervous system, and skin

 

ectopic pregnancy: occurs when fertilization and implantation take place in the oviduct

 

embryo: the organism in the stages of development from the time the zygote begins cleavage until nine weeks of gestation, when the embryo becomes a fetus

 

endoderm: germ layer that forms gut lining, pancreas, and liver

 

expulsion stage: the stage in which the smooth muscle walls of the uterus contract in rhythmic cycles to deliver the fetus from the vagina

 

extra-embryonic membranes: membranes surrounding the embryo, and later the fetus, that support its development in different ways; include the allantois, amnion, chorion, and yolk sac

 

fertilization: the fusing of a sperm nucleus with an egg nucleus to form a zygote; occurs in the oviduct

 

fetal alcohol spectrum disorder: a permanent syndrome of birth defects caused by maternal intake of alcohol during pregnancy; includes disorders of growth, behaviour, and cognitive abilities

 

fetus: the organism in the stages of development from nine weeks until birth

 

folic acid (folate): Vitamin B9; ingestion prior to and during pregnancy prevents neural tube defects, such as spina bifida

 

gastrulation: the folding and differentiation of the embryonic disc into three germ layers, forming the embryonic stage called the gastrula

 

human chorionic gonadotropin (HCG): hormone released from the chorion after implantation; directs corpus luteum to continue making estrogen/progesterone, thereby maintaining the endometrium and preventing menstruation

 

implantation: burrowing of the blastocyst into the wall of the endometrium of the uterus

 

lactation: the production and secretion of milk from the breast; also known as “nursing”

 

mesoderm: germ layer that forms muscle, bone, and muscular organs

 

monozygotic twins: identical twins formed when the embryonic mass produced by the union of one egg and one sperm splits into two separate, identical masses; are of the same sex

 

morphogenesis: the development of body organs and structures; begins with gastrulation

 

morula: embryonic stage of a solid ball of identical cells that results from cleavage of the zygote

 

neurulation: the process of forming the embryo's neural tube, which will develop into the brain and spinal cord

 

parturition: childbirth or labour

 

parturition: the process of labour and delivery, which is divided into dilation, expulsion, and placental stages

 

placenta: embedded in the endometrium; provides a location where nutrients, gases, and wastes can be exchanged between fetal and maternal blood pools

 

placental stage: the stage in which further uterine contractions push the placenta out of body through the vagina; also known as delivery of the afterbirth

 

prenatal: before birth

 

primary germ layers: three layers formed during gastrulation—endoderm, mesoderm, and ectoderm

 

prostaglandins: a group of hormones that contribute to parturition by thinning the cervix and increasing contraction of the uterus

 

sucking reflex: an instinctive sucking action by a newborn that stimulates oxytocin secretion in the mother; results in release of milk from the mammary glands into the milk ducts of the breast

 

teratogen: a substance or other factor that can cause developmental abnormalities during fetal development; e.g., chemicals, viruses, or radiation

 

trimester: one-third of the gestational period

 

There are three trimesters of pregnancy.

 

umbilical cord: tube of blood vessels that connects the fetus to the placenta; for exchange of nutrients, gases, and wastes

 

vernix: a cheesy, oily substance covering the fetus; has antibacterial properties

 

yolk sac: extra-embryonic membrane that produces first blood cells

 

zygote: the one-celled product of egg and sperm fusion; also known as the fertilized egg

 

 

 

Biology 30 Learn EveryWare © 2009 Alberta Education