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Any of the 22 pairs of chromosomes other than the sex chromosomes.


Cells and membranes resulting from fertilization of the ovum at any stage of prenatal development.

corpus luteum

Graafian follicle cells remaining after ovulation that produce estrogen and progesterone.


The number of chromosomes (46 in humans) normally present in body cells other than gametes that represents 1 copy of every chromosome from each parent.


Expulsion of semen from the penis.


The developing baby from the beginning of the third week through the eighth week after conception.


Lining of the uterus.

fertilization age

Prenatal age of the developing baby, calculated from the date of conception (Also called postconceptional age).


The developing baby from 9 weeks after conception until birth; used in everyday practice to describe a developing baby during pregnancy, regardless of gestational age.


Reproductive cell; in the female an ovum and in the male a spermatozoon.

gestational age

Prenatal age of the developing baby (measured in weeks) calculated from the first day of the woman's last menstrual period; approximately 2 weeks longer than the fertilization age (Also called menstrual age).

graafian follicle

A small sac within the ovary that contains the maturing ovum.


Normal number of chromosomes in male or female gamete; refers to 1 copy of a chromosome from each pair (23 in humans, or half the diploid number).


Reduction cell division in gametes that halves the number of chromosomes in each cell.


Cell division in body cells other than the gametes.


Implantation of the fertilized ovum (zygote) in the uterine endometrium.


Formation of gametes (ova) in the female.


Release of the mature ovum from the ovary.


Fetal structure that provides nourishment and removes wastes from the developing baby and secretes hormones necessary for the continuation of pregnancy.

sex chromosome

The X or Y chromosome. Females have two X chromosomes; males have one X and one Y chromosome.

somatic cells

Body cells other than the gametes, or germ cells.


Formation of male gametes (sperm) in the testes.


An agent that can cause defects in a developing baby during pregnancy.


The developing baby from conception through the first week of prenatal life.

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