Biology 30 - Chapter 15

Fertilization

in humans, the joining of male and female gametes (sperm and egg) to form a single cell that contains 23 chromosomes from each parent, for a total of 46 chromosomes

Zygote

cell formed by the union of two gametes; the product of fertilization; has 23 pairs of chromosomes for a total of 46 chromosomes (diploid)

Cleavage

the process of cell division without cell growth; after fertilization, the zygote undergoes repeated cleavage without increasing in overall size

Blastocyst

mammalian embryo at the stage in which it is implanted in the wall of the uterus and consists of a nearly hollow ball of cells; is made up of two groups of cells

inner cell mass

the inner cells of the blastocyst; will develop into the embryo; also known as embryoblast

Implantation

the process of attachment of the embryo to the endometrium; occurs within the first week after fertilization in humans

human chorionic gonadotropin (hCG)

hormone secreted by the trophoblast at the time of implantation of the embryo; prevents degeneration of the corpus luteum

Gastrulation

the formation of the three primary germ layers in embryogenesis

primary germ layers

first layers of cells formed during animal embryogenesis, mainly in the vertebrates; consist of ectoderm (outer layer), mesoderm (middle layer), and endoderm (inner layer)

Morphogenesis

the series of events that form distinct structures of a developing organism; gastrulation marks the beginning of the process

Differentiation

cellular process that enables a cell to develop a particular shape and to perform specific functions that are different from the functions of other cells

Neurulation

in embryogenesis, process of forming the neural tube, which develops into the brain and spinal cord

extra-embryonic membranes

any in an intricate system of membranes external to the embryo; responsible for the protection, nutrition, respiration, and excretion of the embryo and fetus

Allantois

extra-embryonic membrane that forms the foundation for the umbilical cord

Amnion

extra-embryonic membrane that forms a transparent sac that encloses and protects the embryo and fetus

Chorion

in humans, membrane developed from the trophoblast layer of the blastocyst; develops into the fetal part of the placenta; is the outermost of the extra-embryonic membranes which encloses all the other membranes, as well as the embryo

yolk sac

one of the extra-embryonic membranes suspended from the abdominal area of the embryo; in humans, serves no nutritive function, but contributes to the formation of the digestive tract and produces the first blood cells and the future egg (ova) or sperm cells

Placenta

in most pregnant mammals, a disk-shaped organ within the uterus that is rich in blood vessels; attaches the embryo or fetus to the uterine wall and facilitates metabolic exchange

umbilical cord

flexible, often spirally twisted, tube that connects the abdomen of a fetus to the mother’s placenta in the uterus, and through which nutrients are delivered and waste is expelled

Teratogen

any agent that causes a structural abnormality of the developing fetus due to exposure during pregnancy; e.g., smoking

fetal alcohol spectrum disorder (FASD)

term used to describe all the disorders related to alcohol consumption during pregnancy; includes the more commonly known clinical disorder called fetal alcohol syndrome (FAS)

Parturition

the act or process of giving birth to young

Lactation

the secretion and formation of breast milk by the mammary glands

reproductive technology

any technology that enhances or reduces reproductive potential

in vitro fertilization (IVF)

technique in which egg cells are fertilized outside the female’s body

Sterile

condition in which a man or a woman is unable to have children

Infertile

condition in which a man or a woman has been trying to conceive children for a year or more unsuccessfully

artificial insemination

process by which sperm is collected, concentrated, and placed in the female’s vagina

surrogate mother

woman who becomes impregnated and carries a baby for another; baby may be conceived through artificial insemination or in vitro fertilization

Superovulation

production of multiple eggs as a result of hormone treatment

Abstinence

avoidance of sexual intercourse

tubal ligation

a surgical sterilization procedure in women that involves cutting the oviducts and tying off the cut ends to ensure that the ovum does not encounter sperm or reach the uterus

Vasectomy

a sterilization procedure in men; involves cutting and tying the ductus deferens

contraceptive technology

any technology that reduces reproductive potential