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A Caesarian section (C-section) is a surgical procedure performed as an alternative to natural (vaginal) delivery in which cuts are made into both the abdomen and uterus in order to deliver a baby (or babies). C-sections are usually performed when vaginal delivery might pose threats to the health of the mother or baby, but they might also be performed at the request of the mother for other reasons and can be scheduled ahead of time.

Cancer is any type of malignant growth or tumor caused by abnormal and uncontrolled cell division.

Capacitation is a biochemical maturation process that mammalian sperm must go through in the female reproductive tract after they are ejaculated from the male and before they are able to fertilize an oocyte.

Caspases are a class of cysteine proteases, or a type of enzyme, that break up or cleave other proteins. Caspases are involved in the initiation and execution of apoptosis (programmed cell death). The caspases transmit intracellular signals through a "caspase cascade" where one caspase cleaves a second caspase, and this cleavage activates the second caspase. Once activated, the second caspase could then cleave other caspases (thereby activating them) or other downstream ligands.

Castration refers to the removal or loss of function of the gonads (testes or ovaries) by various means, rendering the individual sterile (unable to reproduce).

The cervix is a small, tube-like structure located at the bottom of the uterus and extending into the vagina. When a woman is in labor, the cervix dilates to allow for the passage of the baby through the birth canal. Cells from the cervix are sampled during a Pap smear to test for signs of cancer.

Chemotherapy is the use of drugs, either administered orally or intravenously, to kill cancer cells. Many drugs used in standard chemotherapy regimens are cytotoxic and act to kill cells that divide rapidly. Unfortunately, for this reason, rapidly dividing healthy cells will be killed along with the unwanted cancer cells.

The chorion is a transient, multi-layered, extra-embryonic membrane that matures to form part of the placenta and the connection to the umbilical cord.

A chromatid is one half of a replicated chromosome. Two chromatids are joined by a centromere until they separate during cell division.

Chromatin is the complex of DNA, RNA, and proteins that compact chromosomes into a smaller volume, so that they fit inside the nucleus of a cell. The array of proteins in chromatin can also change the activity of genes.

A chromosome is a compact chromatin structure made up of DNA and an assortment of proteins. DNA is packaged into chromosomes early in meiosis or mitosis in preparation for cell division.

Cilia are small, hair-like projections that line the fallopian tubes. They wave back and forth to help guide the egg from the ovaries to the uterus. If the cilia have been previously damaged by infection, they may not move the egg to the uterus as efficiently. This can lead to the development of an ectopic pregnancy.

Cilia beating occurs in the fallopian tube (or oviduct), where the cilia beat (wave) back and forth to move along the ovum or embryo. They also facilitate fertilization by moving the sperm toward the egg.

Circumcision refers to the surgical procedure where the foreskin (prepuce) covering the head of the penis is removed. This procedure is usually performed on infants or young children in religious ceremonies. In parts of Africa and in other high-risk populations, the procedure is recommended to prevent the contraction of the HIV/AIDS virus.

Cleavage, with regard to the embryo, is a term that refers to the first few mitotic divisions of the pre-implantation embryo. These cell divisions, which begin shortly after fertilization, transform a single cell zygote into a multicellular embryo. Up until the blastocyst stage, the cell divisions serve to increase the embryo’s cell number but do not increase the embryo’s actual size.

The clitoral hood is a flap of skin that covers and protects the female clitoris, functioning like the foreskin in males.

The clitoris is the female erectile organ located at the top of the vulva, directly above the urethra, and it is the homologue of the male penis. It contains many nerve endings and is considered to be the primary source of sexual pleasure in the female.

A clutch refers to all of the eggs that are produced at a single time. In rodents, a clutch of eggs surrounded by cumulus cells can be found in the oviduct following ovulation.


Cohesin is a protein complex that holds sister chromatids together, thereby regulating their separation in anaphase of both mitosis and meiosis.

Colostrum, also known as “first milk”, is the first form of lacteal secretion produced by the mammary glands before the production of milk. Colostrum, in humans, is produced in the late stages of pregnancy and contains antibodies to protect the newborn from disease. Colostrum is very rich in nutrients, such as proteins, antibodies, growth factors, and vitamin A, but contains lower amounts of carbohydrates, lipids, and potassium compared to normal milk. The antibodies in colostrum provide passive immunity, while growth factors stimulate further development of the gut.

The moment that a sperm fertilizes an egg (in humans) to produce a zygote, which eventually develops into an embryo.

A conception device is a medical device used in assisted reproductive technology in order to help achieve pregnancy by means other than intercourse.

A technique to delete a specific gene in a specific tissue to understand the role of the individual gene. In contrast to traditional gene knockout that deletes genes in the whole body, this is induced by a Cre-LoxP recombination system that can eliminate tissue-specific genes at specific times.

Contraception refers to any preventative measure taken to avoid a pregnancy from occurring. In males, the options include condoms, rhythm method, withdrawal, vasectomy, and abstinence. In females, the options include condoms, rhythm method, abstinence, barrier methods, hormonal methods, implantable devices, sterilization surgery, and emergency contraception.

A contraceptive is a drug, chemical, or physical barrier/device that aids in pregnancy prevention.

The corpus albicans (Latin for "white body") is an ovarian scar composed of connective tissue that forms after the corpus luteum degenerates, a process called luteolysis. The corpus albicans is primarily made of collagen and persists on the ovary for a few months.

The corpus luteum (Latin for "yellow body") is a hormone-secreting gland that forms after a mature egg is released from an ovarian follicle. It is composed of granulosa- and theca-lutein cells and primarily secretes the steroid hormone, progesterone. If the egg is not fertilized, the corpus luteum will degenerate and form the corpus albicans.

Corticosteroids are any of the steroid hormones produced in the adrenal cortex.

Corticotropes are specialized cells of the anterior pituitary gland that produce and secrete the hormone corticotropin (ACTH).

A site-specific recombinase technology that is targeted to a specific time and cell type of gene deletions and insertions. The Cre-Lox system is performed by Cre recombinase that recombines the LoxP sites derived from bacteriophage P1. It has been a very useful tool to understand the role of tissue-specific genes and mutant genes that are lethal, if expressed globally.  

Cross-linking is the process of linking two molecules with the use of chemical reactions; cross-links may be covalent bonds, electrostatic bonds, or hydrogen bonds.

The process of crossing over that occurs during prophase I of meiosis refers to the exchange of genetic material between homologous chromosomes. The homologous chromosomes attach to one another and exchange small pieces of DNA, effectively increasing genetic variation.

Cryopreservation refers to the process of storing cells, tissues, or organs at very low temperatures, so they can remain viable and functional again when thawed. Cryopreservation is often used to preserve embryos created by in vitro fertilization, so they can be implanted into a woman’s uterus at a later date.

A cryostat is a cold temperature chamber containing a microtome, or slicer, used to prepare thin sections from frozen tissues. The tissues are often maintained at -20 degrees Celsius.

Cumulus cells are one of two functionally divided classes of granulosa cells in the antral follicle. They surround the oocyte to form the cumulus-oocyte complex and are released with the egg during ovulation. In order for fertilization to occur, the sperm must penetrate through the layer of cumulus cells. An abundance of cumulus cells is necessary for the development of a healthy embryo, as they provide the necessary nutrients and energy for oocyte maturation.

The cumulus-oocyte complex is ovulated during the ovulatory phase of the menstrual cycle and is just what it seems: an oocyte surrounded by specialized granulosa cells, called cumulus cells. The cumulus cells surrounding the oocyte ensure healthy oocyte and embryo development.

Ovarian cysts are fluid-filled sacs formed in the ovaries. There are a few different types, but the most common are follicular or luteal cysts, which are formed during ovulation when the egg is not properly released from the follicle and remains in the ovary, or when the corpus luteum does not break down and dissolve after release of the oocyte. These cysts often disappear in a matter of months, but more serious cysts may cause abdominal pain and bleeding.

Cytokinesis is the division of the cytoplasm in a single cell for the purpose of forming two new daughter cells during mitosis and meiosis.