A Reproductive Lexicon


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The ectocervix is the lower, vaginal portion of the cervix consisting of stratified squamous epithelium.

The ectoderm is the outermost layer of cells of a eukaryote or the outermost layer of cells in the developing embryo once it has reached the gastrula stage. This cell layer ultimately gives rise to nervous tissue, skin, mammary glands, pituitary gland, and enamel of the teeth.

An ectopic pregnancy is a pregnancy that results when an egg implants itself anywhere outside of the uterus, such as the fallopian tube or abdominal cavity. These pregnancies can be dangerous to the health of the mother and are rarely viable.

An effector is a protein, often an enzyme, within a hormonally stimulated cell that helps produce the end result of the hormonal stimulation. Known effectors include transcription factors involved with altering cellular gene transcription, enzymes controlling the storage and retrieval of intracellular glucose, enzymes that produce steroid hormones, and intracellular structural proteins that control cellular shape and movement. These molecules often use intracellular energy stores and result in the amplification of hormonal signals, so that binding of a few hormone molecules can make cells do things that would otherwise be impossible, if they only depended on the energy from binding the hormone molecules, themselves.


An egg, also known as an ovum, is the female reproductive cell or gamete. Eggs are arrested at metaphase of meiosis II, and following ovulation, they can be fertilized in the presence of sperm. In addition to containing DNA, the egg contains critical stores of maternal mRNAs and protein that will support fertilization and subsequent embryo development.

Egg activation refers to a series of events that occur in the egg after it is fertilized by a sperm. These events include completion of meiosis, initiating the block to polyspermy, and translation of specific mRNAs from the egg that are necessary for embryonic development prior to the maternal to zygotic transition. In all animal species studied to date, a rise in calcium levels within the egg triggers all events of egg activation.

Egg banking is an assisted reproductive technology procedure in which multiple eggs are retrieved from a woman following hormonal hyperstimulation. Although similar to embryo banking, the eggs are not fertilized prior to cryopreservation. Thus, this is a good option for women who do not have a male partner and who do not want to use donor sperm. Although this relatively new technology is successful, it is still considered experimental. The process of egg banking can take up to one month to complete.

Egg donation is the process in which a woman (egg donor) volunteers to donate an egg/oocyte or several oocytes to another woman in the hopes of helping her become pregnant through the process of in vitro fertilization (IVF). Egg donation can be part of the process of third–party reproduction. Known egg donation is reserved for those individuals or couples who select a family member or friend to be their egg donor. Anonymous egg donation is when the donor is unknown to the patient or intended couple. Many times, egg donation is anonymous. An egg donor is typically given a thorough medical exam before being treated with hormones to induce hyperovulation. Following hormonal treatment, approximately 10-15 eggs are harvested to be screened for future IVF.

Egg freezing (or oocyte cryopreservation) is the freezing of eggs (oocytes) to preserve the fertility of female cancer patients before they undergo chemotherapy or radiotherapy. Egg freezing may be an alternative to embryo freezing in order to avoid the immediate need for a fertilizing sperm in cases where a male partner or sperm donation are not available or acceptable to the patient. The typical egg freezing procedure includes the use of injectable hormones to stimulate the ovaries to promote the growth of multiple mature eggs, a surgical procedure to collect oocytes from the ovary, rapid freezing of mature oocytes, and storage of cryopreserved oocytes for a period of time (e.g. years). In the future, these oocytes can be thawed and used for in vitro fertilization by sperm to create embryos, which can then be transferred into the uterus to achieve pregnancy. Egg freezing is now considered to be an established technology by the American Society of Reproductive Medicine due to significant improvements in pregnancy rates.

Ejaculation is the release of semen from the urethral opening of the penis and is usually accompanied by orgasm.

The ejaculatory ducts are paired structures in the male reproductive system formed by the union of the vas deferens with the duct of the seminal vesicle.

Embedding refers to the placement of fixed tissue into a matrix (such as paraffin wax) that provides support for further manipulation of the tissue during processes like sectioning.

An embryo is an organism in its early stages of development. In humans, this stage extends from the time an egg undergoes fertilization to eight weeks after fertilization. Beyond that point, the organism is then referred to as a fetus.

Embryo banking is an ART procedure in which embryos are created through in vitro fertilization. These embryos are then cryopreserved and stored for future reproductive use. The process of embryo banking can take up to one month to complete.

Embryo donation utilizes unused embryos or embryos specifically created via donor eggs and donor sperm. The donated embryo is placed into the uterus of the future mother or the surrogate mother.

The process by which an early embryo develops. During this time an embryo undergrows rapid cell division and growth.  

The embryonic disk is the flat, disk-shaped conceptus that forms prior to gastrulation in some vertebrates.

Embryonic stem cells are undifferentiated cells taken from the inner cell mass of an embryo. These cells have the ability to give rise to all three of the primary germ cell layers, the ectoderm, endoderm, and mesoderm. Because of this quality, these cells are useful in laboratory work. The stem cells are taken from both unused embryos in IVF and from cloned embryos created using donor eggs.

Emergency contraception is a form of birth control that may be used for up to five days after sexual intercourse has taken place. Emergency contraception is often used when no contraceptive methods were used, when the one or more birth control methods used may have failed, or when a woman was made to have sex against her will. The options for emergency contraception are emergency contraceptive pills and the Copper-T Intrauterine Device. These methods are not as effective as primary birth control methods used before or during sex.

The endocervix is the inner, mucosal layer of the cervix.

An endocrinologist is a physician who focuses on the treatment of diseases and conditions associated with the body’s glands and balance of hormones.

Endocrinology is the study of the body’s endocrine glands and their secretions (known as hormones).

The endoderm is the innermost layer of cells of a eukaryote or the innermost layer of cells in the developing embryo once it has reached the gastrula stage. This cell layer ultimately gives rise to the inner (epithelial) linings of the gut and associated glands, liver, respiratory tract, urinary bladder, ear passages, and the functional portions of the thyroid, parathyroid, pancreas, and thymus.

Endometriosis is a condition in which cells of the uterine lining, or endometrium, grow outside of the intrauterine environment, often on or around surrounding structures. This results in potential pain, bleeding, and scarring of internal reproductive structures, and, in some cases, infertility.

The endometrium is the highly dynamic uterine tissue lining the uterine cavity. Its cellular and molecular composition changes daily throughout the menstrual cycle in fertile women, and the outer functional layer is shed at each menstruation. The endometrium provides the "soil" into which an embryo implants to establish a pregnancy. 

Enzyme-Linked Immunosorbent Assay, or ELISA, is a method used to measure reproductive hormones (eg. proteins or steroids) in blood samples. The technique uses antibodies that are linked to an enzyme. The antibodies specifically bind to the hormone in the blood sample. At the end of the reaction, a chemical is added and the enzyme causes a change in color (from clear to blue). The amount of hormone in the sample is directly proportional to the change in color.

The epiblast is a tissue type of the upper side of the embryonic disk, which arises from the inner cell mass during the late blastula and early trophoblast stages of embryonic growth. These cells give rise to the tissues of the embryo proper.

The epididymis is a long, tightly coiled tube connected to the testis. Its function is to bring non-motile sperm incapable of fertilization to functional maturity before moving into the vas deferens.

Episiotomy is a small surgical incision along the midline of the perineum, the tissue between the vagina and anus, to enlarge the vaginal opening and facilitate vaginal delivery. It can be performed under local or epidural anesthesia, and it is sutured immediately after the delivery.

Erectile dysfunction (or impotence) is the inability to achieve or maintain a firm erection for sex. There are many potential causes of erectile dysfunction, including other underlying health issues or behaviors. For example, chronic alcohol consumption is a risk factor for erectile dysfunction. Alcohol is a central nervous depressant, so it is theorized that this in addition to other physiological changes that occur when consuming alcohol contribute to erectile dysfunction.

Estrogen is a steroid hormone that is produced primarily in the female ovaries and, in small amounts, in the adrenal cortex, male testes, and placenta. Estrogen helps regulate and guide female sexual development and reproductive system functions, such as the estrous and menstruation cycles.

Estrone, also known as oestrone, is an estrogen hormone secreted by the ovary. It is a known carcinogen for women and is the least abundant of the three estrogens in the body.

The estrous cycle, which has been studied extensively in rodents, refers to the cyclic alterations that occur in the female reproductive tract and in sexual receptivity. The estrous cycle is often likened to the menstrual cycle in humans. It is composed of four distinct stages – proestrus, estrus, metestrus, and diestrus – that are each characterized by distinct physiology as well as animal morphology and behavior. Proestrus is the portion of the cycle when eggs reach full maturity within the follicles. External examination of the female genitalia reveals a swollen vulva and open vagina. Estrus is the stage of the cycle when ovulation occurs. The vagina remains open, and, at this stage, females are maximally receptive to males. Metestrus is the stage when the mature egg moves through the fallopian tube, and the vagina is closed. If successful copulation and fertilization occur, pregnancy will occur. If pregnancy does not occur, diestrus will ensue. Diestrus is the final stage of the estrous cycle in which unfertilized eggs are eliminated, and the vagina remains closed. During this stage, a new cohort of follicles begins rapid growth to prepare for ovulation in the next cycle.

Eumenorrhea refers to normal menstruation.

ex situ refers to any procedure where the cells of interest are examined outside of their native environment.

ex vivo refers to occurrences outside of a living organism. An ex vivo experiment is one that is completed outside of a living organism, where cells are directly isolated from the living organism.

An extra-amniotic pregnancy occurs when the amniotic sac ruptures, and the baby develops in the extra-embryonic coelom.