87 terms

reproductive and development

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allantois
In animals, a membrane that develops from the yolk sac and helps dispose of the embryo's nitrogenous wastes. The allantois forms part of the umbilical cord in mammals.
amnion
In vertebrate animals, the membrane that encloses the fluid-filled amniotic sac containing the embryo.
asexual reproduction
The creation of genetically identical offspring by a single parent, without the participation of gametes (sperm and egg).
birth control pill
A chemical contraceptive that inhibits ovulation, retards follicular development, or alters a woman's cervical mucus to prevent sperm from entering the uterus.
blastocyst
A mammalian embryo made up of a hollow ball of cells that results from cleavage and that implants in the mother's endometrium.
budding
A means of asexual reproduction in which a new individual splits off after developing from an outgrowth of a parent.
cervix
The narrow neck at the bottom of the uterus, which opens into the vagina.
chlamydia
A common sexually transmitted disease caused by a bacterial infection. Its primary symptoms are genital discharge and burning during urination. It is easily treatable with antibiotics.
chorion
In animals, the outermost membrane, which in mammals becomes part of the placenta.
chorionic villus
(plural, villi) An outgrowth of the chorion, containing embryonic blood vessels. As part of the placenta, chorionic villi absorb nutrients and oxygen from the mother's bloodstream and pass wastes into the mother's bloodstream.
cleavage
(1) Cytokinesis in animal cells and in some protists, characterized by pinching in of the plasma membrane. (2) In animal development, the succession of rapid cell divisions without cell growth, converting the animal zygote to a ball of cells.
clitoris
An organ in the female that engorges with blood and becomes erect during sexual arousal.
condom
A flexible sheath, usually made of thin rubber or latex, designed to cover the penis during sexual intercourse for contraceptive purposes or as a means of preventing sexually transmitted diseases.
Contraception
The deliberate prevention of pregnancy.
corpus luteum
A small body of endocrine tissue that develops from an ovarian follicle after ovulation. The corpus luteum secretes progesterone and estrogen during pregnancy.
diaphragm
(1) The sheet of muscle separating the chest cavity from the abdominal cavity in mammals. Its contraction expands the chest cavity, and its relaxation reduces it. (2) A dome-shaped rubber cap that covers a woman's cervix, serving as a barrier method of contraception.
ectoderm
The outer layer of three embryonic cell layers in a gastrula. The ectoderm forms the skin of the gastrula and gives rise to the epidermis and nervous system in the adult.
egg
A female gamete.
ejaculation
The expulsion of sperm-containing fluid (semen) from the penis.
embryo
A developing stage of a multicellular organism. In humans, the stage in the development of offspring from the first division of the zygote until body structures begin to appear, about the 9th week of pregnancy.
endoderm
The innermost of three embryonic cell layers in a gastrula. The endoderm forms the developing digestive tube in the gastrula and gives rise to the innermost linings of the digestive tract and other hollow organs in the adult.
endometrium
The inner lining of the uterus in mammals, richly supplied with blood vessels that provide the maternal part of the placenta and nourish the developing embryo.
fertilization
The union of a haploid sperm cell with a haploid egg cell, producing a zygote.
fetus
A developing human from the 9th week of pregnancy until birth. The fetus has all the major structures of an adult.
fission
A means of asexual reproduction whereby a parent separates into two or more genetically identical individuals of about equal size.
follicle
A cluster of cells surrounding, protecting, and nourishing a developing egg cell in the ovary. The follicle also secretes estrogen.
Gamete
A sex cell; a haploid egg or sperm. The union of two gametes of opposite sex (fertilization) produces a zygote.
gametogenesis
The creation of gametes within the gonads.
gastrula
The embryonic stage resulting from gastrulation in animal development. Most animals have a gastrula made up of three layers of cells: ectoderm, endoderm, and mesoderm.
gastrulation
The phase of embryonic development that transforms the blastula (blastocyst in mammals) into a gastrula. Gastrulation adds more cells to the embryo and sorts the cells into distinct cell layers.
genital herpes
A common sexually transmitted disease caused by a virus. The primary symptom is sores on the genitalia. While outbreaks can be controlled with medication, genital herpes is incurable.
gestation
Pregnancy; the state of carrying developing young within the female reproductive tract.
hermaphrodite
An individual that has both female and male reproductive systems, producing both sperm and eggs.
hymen
A thin membrane that partly covers the vaginal opening in the human female and is ruptured by sexual intercourse or other vigorous activity.
impotence
The inability to maintain an erection; also called erectile dysfunction.
In vitro fertilization (IVF)
Uniting sperm and egg in a laboratory container, followed by the placement of a resulting early embryo in the mother's uterus.
induction
During embryonic development, the influence of one group of cells on an adjacent group of cells.
infertility
The inability to conceive after one year of regular, unprotected sexual intercourse.
inner cell mass
A cluster of cells in a mammalian blastocyst that protrudes into one end of the cavity and subsequently develops into the embryo proper and some of the extra embryonic membranes.
labia majora
A pair of outer thickened folds of skin that protect the female genital region.
labor
A series of strong, rhythmic contractions of the uterus that expel a baby out of the uterus and vagina during childbirth.
menstrual cycle
The hormonally synchronized cyclic buildup and breakdown of the endometrium in some primates, including humans.
Menstruation
Uterine bleeding resulting from the breakdown of the endometrium during a menstrual cycle.
mesoderm
The middle layer of the three embryonic cell layers in a gastrula. The mesoderm gives rise to muscles, bones, the dermis of the skin, and most other organs in the adult.
morning-after pill (MAP)
A birth control pill taken within three days of unprotected intercourse to prevent fertilization or implantation.
natural family planning
A form of contraception that relies on refraining from sexual intercourse when conception is most likely to occur; also called the rhythm method.
oogenesis
The formation of egg cells within the ovaries.
ovarian cycle
Hormonally synchronized cyclic events in the mammalian ovary, culminating in ovulation.
ovary
(1) In animals, the female gonad, which produces egg cells and reproductive hormones. (2) In flowering plants, the base of a carpel in which the egg-containing ovules develop.
oviduct
The tube that conveys egg cells away from an ovary; also called a fallopian tube.
ovulation
The release of an egg cell from an ovarian follicle.
penis
The structure in male mammals that functions in sexual intercourse.
placenta
In most mammals, the organ that provides nutrients and oxygen to the embryo and helps dispose of its metabolic wastes. The placenta is formed of the embryo's chorion and the mother's endometrial blood vessels.
polar body
The smaller of two daughter cells produced during meiosis of oogenesis.
prepuce
A fold of skin covering the head of the clitoris or penis.
primary oocyte
A diploid cell, in prophase I of meiosis, that can be hormonally triggered to develop into an ovum.
primary spermatocyte
A diploid cell in the testis that undergoes meiosis I.
programmed cell death
The timely death (and disposal of the remains) of certain cells, triggered by certain genes; an essential process in normal development.
prostate gland
A gland in human males that secretes an acid-neutralizing component of semen.
reproduction
The creation of new individuals from existing ones.
reproductive cycle
In females, a recurring series of events that produces gametes, makes them available for fertilization, and prepares the body for pregnancy.
rhythm method
A form of contraception that relies on refraining from sexual intercourse when conception is most likely to occur; also called natural family planning.
scrotum
A pouch of skin outside the abdomen that houses a testis. The scrotum functions in cooling the sperm, thereby keeping them viable.
secondary oocyte
A haploid cell that results from meiosis I in oogenesis and that will become an ovum after meiosis II.
secondary spermatocyte
A haploid cell that results from meiosis I in spermatogenesis and that will become a sperm cell after meiosis II.
semen
The sperm-containing fluid that is ejaculated by the male during orgasm.
seminal vesical
A gland in males that secretes a fluid component of semen that lubricates and nourishes sperm.
seminiferous tubule
A coiled sperm-producing tube in a testis.
Sexual reproduction
The creation of genetically distinct offspring by the fusion of two haploid sex cells (gametes: sperm and egg), forming a diploid zygote.
sexually transmitted disease (STD)
A contagious disease spread by sexual contact.
sperm
A male gamete.
spermatogenesis
The formation of sperm cells.
Spermicide
A sperm-killing chemical, in the form of a cream, jelly, or foam, that works with a barrier device as a method of contraception.
stem cell
A relatively unspecialized cell that can give rise to one or more types of specialized cells. See embryonic stem cell (ES cell); adult stem cell.
testis
(plural, testes) The male gonad in an animal. The testis produces sperm and, in many species, reproductive hormones.
trimester
In human development, one of three 3-month-long periods of pregnancy.
trophoblast
In mammalian development, the outer portion of a blastocyst. Cells of the trophoblast secrete enzymes that enable the blastocyst to implant in the endometrium of the mother's uterus.
tubal ligation
A means of sterilization in which a woman's two oviducts (fallopian tubes) are tied closed to prevent eggs from reaching the uterus. A segment of each oviduct is removed.
umbilical cord
A structure containing arteries and veins that connects a developing embryo to the placenta of the mother.
urethra
A duct that conveys urine from the urinary bladder to the outside. In the male, the urethra also conveys semen out of the body during ejaculation.
uterus
In the reproductive system of a mammalian female, the organ where the development of young occurs; the womb.
vagina
Part of the female reproductive system between the uterus and the outside opening; the birth canal in mammals. The vagina accommodates the male's penis and receives sperm during copulation.
vas deferen
(plural, vasa deferentia) Part of the male reproductive system that conveys sperm away from the testis; the sperm duct; in humans, the tube that conveys sperm between the epididymis and the common duct that leads to the urethra.
vasectomy
Surgical removal of a section of the two sperm ducts (vasa deferentia) to prevent sperm from reaching the urethra; a means of sterilization in the male.
vulva
The outer features of the female reproductive anatomy.
yolk sac
A membrane that develops from endoderm and produces the embryo's first blood cells and germ cells and gives rise to the allantois.
zygote
The fertilized egg, which is diploid, that results from the union of haploid gametes (sperm and egg) during fertilization.