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Chapter 18 - Development throughout Life
Terms in this set (41)
The union between an egg (technically a secondary oocyte) and a sperm. It takes about 24 hours from start to finish and usually occurs in a widened portion of the oviduct, not far from the ovary.
The period during prenatal development that extends from fertilization through the second week. Cleavage and implantation follow fertilization.
The developing human from fertilization through the second week of gestation (the pre-embryonic period).
The period of prenatal development that extends from week 3 through week 8 of gestation. It is the period when tissues and organs form.
The developing human from week 3 through week 8 of gestation (the embryonic period).
The period of prenatal development that extends from week 9 of gestation until birth. It is when rapid growth occurs.
The developing human from week 9 of gestation until birth (the fetal period).
The diploid cell resulting from the joining of an egg nucleus and a sperm nucleus. The first cell of a new individual.
A rapid series of moronic cell divisions in which the zygote first divides into two cells, and then four cells, and then eight cells, and so on. It usually begins about one day after fertilization as the zygote moves along the oviduct toward the uterus.
The stage of development consisting of a hollow ball of cells. It contains the inner cell mass, a group of cells that will become the embryo, and the trophoblast, a thin layer of cells that will give rise to part of the placenta.
Inner Cell Mass
A group of cells within the blastocyst that will become the embryo proper and some extraembryonic membranes.
A group of cells within the blastocyst that gives rise to the chorion, the extraembryonic membrane that will become part of the placenta.
The organ that delivers oxygen and nutrients to the embryo and later fetus and carries carbon dioxide and wastes away from each. It is also called the afterbirth.
The process by which a blastocyst (pre-embryo) becomes embedded in the lining of the uterus. It normally occurs high up on the back wall of the uterus.
Human Chorionic Gonadotropin (HCG)
A hormone produced by the cells of the early embryo (blastocyst) and the placenta that maintains the corpus luteum for approximately the first 3 months of pregnancy. It enters the bloodstream of the mother and is excreted in her urine. It forms the basis for many pregnancy tests.
The inability to conceive (become pregnant) or to cause conception (in the case of males.
Membranes that lie outside the embryo, where they protect and nourish the embryo and later the fetus. They include the amnion, yolk sac, chorion, and allantois.
The extraembryonic membrane that enclose the embryo in a fluid-filled space called the amniotic cavity. Amiotic fluid forms a protective cushion around the embryo that later can be examined as part of prenatal testing in a procedure known as amniocentesis.
The extraembryonic membrane that is the primary source of nourishment for embryos in many species of vertebrates. In humans, however, it does not provide nourishment (human embryos and fetuses receive nutrients from the placenta). In humans, it is a site of blood cell formation and contains cells, alled primordial germ cells, that migrate to the gonads, where they differentiate into immature cells that will eventually become sperm or oocytes.
The extraembryonic membrane whose blood vessels become part of the umbilical cord, the ropelike connection between the embryo and the placenta.
The ropelike connection between the embryo (and later the fetus) and the placenta. It consists of blood vessels (two umbilical arteries and one umbilical vein) and supporting connective tissue.
The extraembryonic membrane that becomes that embryo's major contribution to the placenta.
Fingerlike projections of the chorion of the embryo that grow into the uterine lining of the mother during formation of the placenta and become part of the placenta.
A procedure by which the baby and placenta are removed from the uterus through an incision in the abdominal wall and uterus.
The process by which cells become specialized with respect to structure and function.
The development of body form that begins during the third week after fertilization.
Primary Germ Layers
The layers produced by gastrulation from which all tissues and organs form. They are ectoderm, mesoderm, and endoderm.
Cell movements that establish the primary germ layers of the embryo. The embryo during this period is called a gastrula.
The primary germ layer that forms the nervous system, epidermis, and epidermal derivatives such as hair, nails, and mammary glands.
The primary germ layer that forms some organs and glands (for example, the pancreas, liver, thyroid gland, and parathyroid glands) and the epithelial lining of the urinary, respiratory, and gastrointestinal tracts.
The primary germ layer that gives rise to muscle, bone, connective tissue, and organs such as the heart, kidneys, ovaries, and testes.
The flexible rod of tissue that develops during gastrulation and signals where the vertebral column will form. It defines the axis of the embryo and gives the embryo some rigidity. During development, vertebrae form around it. It eventually degenerates, existing only as the pulpy, elastic material in the center of the intervertebral discs.
The embryonic structure that gives rise to the brain and spinal cord.
A series of events during embryonic development when the central nervous system (brain and spinal cord) forms from the ectoderm. During this period, the embryo is called a neurula.
Blocks formed from mesoderm cells of the developing embryo that eventually form skeletal muscles of the neck and trunk, connective tissues, and vertebrae.
The change in the relative rates of growth of carious parts of the body. Such growth helps shape developing humans and other organisms.
Birth, which usually occurs about 38 weeks after fertilization.
The process by which the fetus is expelled from the uterus and moved through the vagina and into the outside world. During this process, uterine contractions occur at regular intervals, are often painful, and intensify with walking. It is usually divided into the dilation stage, expulsion stage, and placental stage.
Developmental defects present at birth. They involve structure, function, behavior, or metabolism and may or may not be hereditary.
The production and ejection of milk from the mammary glands. The hormone prolactin from the anterior pituitary gland promotes milk production, and the hormone oxytocin released from the posterior pituitary gland makes milk available to the suckling infant by stimulating milk ejection, or let-down.
The normal and progressive alteration in the structure and function of the body. It is possibly caused by decline in critical body systems, disruption of cell processes by free radicals, slowing or cessation of cell division, and decline in the ability to repair damaged DNA.
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