Overview of the Human Reproductive System

Gonads

Reproductive structures responsible for producing gametes.

Ovary

Produces eggs (ova). Females have two ovaries.

Testis

Site of sperm and male sex hormone production enclosed within the scrotum for temperature regulation.

Somatic cell

Diploid, non-reproductive cells (E.g., muscle cells, skin cells, nerve cells).

Germ cell

Diploid cells of embryonic origin and gives rise to gametes via meiosis (E.g., spermatogonium, oogonium).

Gamete

Haploid sex cells (E.g., egg and sperm).

Viviparity

Birth to live young that receive nutrients directly from the mother's body.

Oviparity

Fertilized eggs get laid then hatch later.

Ovoviviparity

Internally fertilized eggs hatch and give birth to live young who continue to receive nutrients from the yolk of the egg.

Oviduct (Fallopian/Uterine Tube)

Responsible for moving the eggs from the ovary to the uterus; site of fertilization.

Uterus

Muscular chamber in which the embryo develops until birth.

Cervix

Connects the vagina to the uterus.

Vagina

Muscular canal that serves as a birth canal during delivery.

Sertoli cells

Stimulated by FSH and surround and nurture the sperm.

Interstitial cells (Leydig cells)

Secrete male hormones (E.g., testosterone and androgens) in the presence of LH.

Epididymis

Coiled tube attached to each testicle that serves as the site of final sperm maturation and storage.

Vas deferens

Transfers sperm from each epididymis to the urethra.

Seminal vesicles

Excrete fluid into the vas deferens upon ejaculation.

Penis

Transports semen into vagina.

Zygote

Fertilized egg.

Morula

A solid ball of cells resulting from the division of a zygote.

Blastocyst

A hollow ball of cells that implants in the uterus.

Acrosome

Lysosome-like organelle that penetrates the egg.

Pro-nucleus

Haploid (23 chromosomes) nucleus of the sperm or egg.

Mid-piece

Plethora of mitochondria for energy.

Tail

Flagellum that produces motion.

Oogenesis

The process of egg formation in females.

Spermatogenesis

The process of sperm formation in males.

Primary oocytes

Oogonia that have begun meiosis but stopped in prophase I, remaining until puberty.

Primordial follicle

Structure formed when primary oocytes are surrounded by a single layer of granulosa cells.

Primary follicles

Formed from primordial follicles when granulosa cells enlarge and increase in number.

Secondary follicles

Formed when fluid-filled vesicles develop and theca cells arise on the outside of the follicle.

Mature follicles

Formed when vesicles create a single antrum.

Follicular phase

The stage of the menstrual cycle involving the development of the egg and secretion of estrogen from the follicle.

Ovulation

The midcycle release of the egg, triggered by a surge of LH.

Luteal phase

The stage following ovulation characterized by secretion of estrogen and progesterone from the corpus luteum.

Secondary oocyte

The cell that results from the completion of meiosis I just before ovulation.

Meiosis II completion

Occurs only if the secondary oocyte is fertilized by a sperm cell.

Corpus luteum

The structure formed from the remaining follicle after ovulation, secreting hormones if the egg is fertilized.

Corpus albicans

The scar formed when the corpus luteum degenerates if fertilization does not occur.

Female hormonal contraception

A method that involves artificially spiking estrogen and progesterone levels to prevent ovulation and implantation.

GnRH

Gonadotropin-releasing hormone released by the hypothalamus to trigger FSH and LH release.

FSH

Follicle-stimulating hormone that stimulates Sertoli cells to promote sperm development.

LH

Luteinizing hormone that stimulates Leydig cells to release testosterone.

hCG

Human chorionic gonadotropin secreted by the placenta to maintain the corpus luteum after implantation.

Endometrium

The uterine lining that must remain intact for a successful pregnancy.

Testosterone

A hormone released by Leydig cells that is essential for male reproductive development.