Chapter 22 - Growth, development, and aging Flashcards
prenatal period vs postnatal period
The prenatal period begins at conception and ends at birth; the postnatal period begins at birth and continues until death.
conception
also called fertilization
It is the moment the female ovum and the male sperm cells unite to form a zygote; it is the beginning of the life of an organism.
embryology
the branch of biology and medicine concerned with the study of embryos and their development
morula
an early-stage embryo consisting of 16 cells (called blastomeres) in a solid ball contained within the zona pellucida
zona pellucida
a glycoprotein layer surrounding the plasma membrane of mammalian oocytes
blastomere
a type of cell produced by cleavage (cell division) of the zygote after fertilization and is an essential part of blastula formation
blastulation vs. blastula
Blastulation is the stage in early animal embryonic development that produces the blastula. The blastula (from Greek βλαστός (blastos meaning sprout) is a hollow sphere of cells (blastomeres) surrounding an inner fluid-filled cavity (the blastocoel).
Embryonic development begins with a sperm fertilizing an egg cell to become a zygote, which undergoes many cleavages to develop into a ball of cells called a morula. Only when the blastocoel is formed does the early embryo become a blastula. The blastula grows to become a blastocyst.
blastocyst
A blastula that has developed to the point where differentiation begins in its cells. The blastomeres in the blastula’s outer cell layer are replaced by a trophoblast.
As the blastocyst develops, it forms a structure with two cavities, the yolk sac and amniotic cavity.
trophoblast
A thin layer of cells that helps a developing embryo attach to the wall of the uterus, protects the embryo, and forms a part of the placenta.
pluripotent
(of an immature or stem cell) capable of giving rise to several different cell types
laparoscope
a fiber-optic instrument inserted through the abdominal wall to view the organs in the abdomen or permit small-scale surgery
yolk sac
In humans, a sac involved with the production of blood cells in the developing embryo.
The yolk sac is most important in animals, such as birds, that depend heavily on yolk as the sole source of nutrients for the developing embryo. In these animals, the yolk sac digests the yolk and provides the resulting nutrients to the embryo.
Because uterine fluids provide nutrients to the developing human embryo until the placenta develops, the function of the yolk sac is not a nutritive one. Instead, it has other functions—including production of blood cells.
amniotic cavity
The amniotic cavity is the closed sac between the embryo and the amnion, containing the amniotic fluid.
amnion
A membrane that closely covers the human and various other embryos when they are first formed. It fills with amniotic fluid, which causes the amnion to expand and become the amniotic sac that provides a protective environment for the developing embryo.
chorion
The outermost fetal membrane around the embryo in mammals, birds and reptiles. It develops from an outer fold on the surface of the yolk sac, which lies outside the zona pellucida (in mammals).
in vitro fertilization
The Latin term in vitro means, literally, “within a glass.” In the case of in vitro fertilization, it refers to the glass laboratory dish where an ovum and sperm are mixed and where fertilization occurs.
In the classic technique, the ovum is obtained from the woman by first inserting a fiber-optic viewing instrument called a laparoscope through a very small incision in her abdomen. After it is in the abdominal cavity, the device allows the physician to view the ovary, puncture it, and “suck up” an ovum from a mature follicle. Over the years refinements to this technique have been made, and less invasive procedures are currently being used.
After fertilization in a laboratory dish and about 2.5 days’ growth in a temperature-controlled environment, the developing zygote (which by then has reached the 8- or 16-cell stage) is placed by the physician into the mother’s uterus. If implantation is successful, growth will continue and the subsequent pregnancy will progress. In the most successful fertility clinics in the United States, a normal term birth will occur in about 30% of in vitro fertilization attempts.
gastrulation
Gastrulation is the stage in the early embryonic development of most animals, during which the blastula (a single-layered hollow sphere of cells) is reorganized into a multilayered structure known as the gastrula.
Before gastrulation, the embryo is a continuous epithelial sheet of cells; by the end of gastrulation, the embryo has begun differentiation to establish distinct cell lineages, set up the basic axes of the body (e.g. dorsal-ventral, anterior-posterior), and internalized one or more cell types including the beginnings of the gastrointestinal tract.
germ layer
a primary layer of cells that forms during embryonic development
gastrula
An embryo at the stage following the blastula. It has a hollow cup-shaped structure having three layers of cells.
The gastrula is trilaminar (“three-layered”). These three germ layers are known as the ectoderm (outer layer), mesoderm (middle layer), and endoderm (inner layer).
Bilateria
also called bilaterians
They are animals with bilateral symmetry as an embryo, i.e. having a left and a right side that are mirror images of each other.
Humans, cats, monkeys, frogs, and sharks are just some examples.
choriocarcinoma
A malignant, fast-growing tumor that develops from trophoblastic cells (cells that help an embryo attach to the uterus and help form the placenta). Almost all choriocarcinomas form in the uterus after fertilization of an egg by a sperm.
chorionic villi
singular: chorionic villus
Chorionic villi are villi that sprout from the chorion to provide maximal contact area with maternal blood.
They are an essential element in pregnancy.
Branches of the umbilical arteries carry embryonic blood to the villi. After circulating through the capillaries of the villi, blood returns to the embryo through the umbilical vein.
Thus, villi are part of the border between maternal and fetal blood during pregnancy.
lacuna
(1) a blank space or a missing part: GAP
(2) a small cavity, pit, or discontinuity in an anatomical structure
villi
singular: villus
(biology) A small projection from a membrane, particularly those found in the mucous membranes of the intestines.
(botany) One of the fine soft hairs on fruits, flowers, and other parts of plants.