Reproduction and Development

Vocabulary terms and definitions covering human reproduction, meiosis, male and female anatomy, gametogenesis, and embryonic development.

Meiosis

Cell division that reduces the chromosome number by half to produce four genetically different haploid sex cells (gametes).

Prophase I

The stage of meiosis where homologous chromosomes pair up and crossing over occurs.

Metaphase I

The stage of meiosis where homologous chromosome pairs line up at the middle of the cell.

Anaphase I

The stage of meiosis where homologous chromosomes separate to opposite poles.

Telophase I

The stage of meiosis where chromosomes reach opposite ends and two haploid nuclei form.

Cytokinesis I

The process where the cell divides into two haploid daughter cells.

Metaphase II

The stage of meiosis where chromosomes line up individually at the centre of the cell.

Anaphase II

The stage of meiosis where sister chromatids separate to opposite poles.

Cytokinesis II

The process where four genetically unique haploid gametes are produced.

Ovaries

Female reproductive organs that produce oocytes (eggs), oestrogen, and progesterone.

Fimbriae

Structures that sweep or direct the ovum into the oviduct.

Oviduct

The tube containing cilia that move the ovum; it is the usual site of fertilisation (first third of the tube).

Uterus

The site of implantation and fetal development.

Cervix

The opening between the uterus and the vagina.

Testes

Male reproductive organs that produce sperm and testosterone.

Scrotum

The structure that holds testes outside the body to maintain a cooler temperature for sperm production.

Epididymis

The site of sperm maturation.

Vas deferens (ductus deferens)

The duct that transports sperm via peristaltic movement.

Prostate gland

Produces citric acid for ATP production in sperm and proteolytic enzymes to break down clotting agents.

Seminal vesicles

Produce fructose for energy, prostaglandins for sperm motility, and clotting agents to coagulate semen.

Bulbourethral (Cowper’s) glands

Produce mucus to lubricate the urethra and alkaline fluid to neutralise urethral acidity.

Spermatogenesis

The biological process of developing male germ cells (spermatogonia) into mature, haploid spermatozoa (sperm).

Sertoli cells

Cells in the seminiferous tubules that nourish developing germ cells.

Oogenesis

The process of formation, development, and maturation of female gametes (ova) within the ovaries.

Primordial follicle

Composed of a primary oocyte and granulosa cells.

Zona pellucia

A layer that develops in the primary follicle under the influence of FSH.

Secondary follicle

A follicle where the oocyte completes meiosis I to become a secondary oocyte and pauses during early meiosis II.

Corpus luteum

A structure that secretes progesterone and a small amount of estrogen; it forms after the secondary oocyte is released.

Menarche

The beginning of the menstrual cycle in females after puberty due to increased GnRH, LH, and FSH secretion.

Menses

A phase lasting approximately $4$ to $5$ days involving the shedding of the superficial layer of the endometrium.

Proliferative Stage

Stage where developing follicles produce oestrogen, causing the endometrium tissue to thicken.

Secretory Stage

Stage where the corpus luteum forms and secretes progesterone to further thicken the endometrium.

Human Chorionic Gonadotropin (HCG)

Hormone produced by trophoblast cells that maintains the corpus luteum so progesterone remains high.

Capacitation

Process in the uterus where enzymes stabilize the acrosomal head and increase tail motility of sperm.

Fast Block

Mechanism to prevent polyspermy where sodium ions enter the oocyte, depolarising the membrane and triggering meiosis II.

Slow Block

Mechanism where calcium ions trigger the cortical reaction, hardening the zona pellucida.

Morula

A solid ball of cells formed from the zygote during cleavage.

Blastocyst

An embryo stage containing an inner cell mass, a trophoblast, and a blastocoele.

Gastrulation

Process occurring on Day $12$ where the primitive streak forms and the three germ layers are established.

Ectoderm

Germ layer that forms the skin and nervous system.

Mesoderm

Germ layer that forms organs, muscle, and bone.

Endoderm

Germ layer that forms the digestive system.

Neurulation

Process on Day $18$ where the ectoderm folds to form the neural tube, developing into the central nervous system.

Organogenesis

The formation of organ systems occurring between weeks $3$ to $8$ until birth.

Parturition

The process of childbirth, occurring around $9$ months, involving a positive feedback loop of oxytocin.