The Reproductive System


  • Ovaries: make female gametes (ova) and secrete female sex hormones (oestrogen and progesterone). Medulla with blood vessels, cortex and follicles. Each follicle consists of an immature egg called an oocyte. Cells around the oocyte are called follicle or granulosa (squamous or cuboidal), or theca cells (connective tissue).
  •  Accessory organs: uterine tubes, uterus and vagina.
  • Internal genitalia: ovaries, and internal ducts.
  • External genitalia: labia (major and minor), vulva, clitoris, mons pubis.
  • Oogenesis: sequence of events that produces ova. Each cell has 2 sets of chromosomes (1 maternal, 1 paternal) and is said to be diploid.
  • Stages of egg development: 1. Primordial follicle (1 layer of squamous-like follicle cells surrounding the oocyte), 2. Primary follicle (two or more layers of cuboidal granulosa cells enclose the oocyte, theca also builds), 3. Secondary follicle (has fluid-filled space between granulosa cells that coalesces to form a central antrum), 4. Tertiary follicle (most mature follicle which bulges from surface of ovary), 5. Ovulation (ejection of oocyte from follicle), corpus luteum (ruptured follicle after ovulation, endocrine function continues).
  • Meiosis in females: starts prenatally, maximum amount of follicles at 7 months, suspended til puberty, first meiosis concluded at ovulation, second meiosis only occurs at fertilisation.
  • Uterus: thick walled organ in the pelvis, anterior to the rectum and posterosuperior to the bladder. Body is a major portion of the uterus. Fundus is the rounded region superior to the entrance of the fallopian tubes. Isthmus is the narrowed region between the body and cervix.
  • Uterine wall: composed of 3 layers: permetrium (outermost serous layer), myometrium (middle layer, interlacing layers of smooth muscle), endometrium (mucosal lining of uterine cavity).
  • Cervix: narrow neck projecting into vagina.
  • Cervical glands: secrete mucus that covers the external orifice and blocks cervix during midcycle.
  • Endometrium: has numerous uterine glands that change in length as endometrial thickness changes. Stratum functionalis: undergoes cyclic changes in response to ovarian hormones, and is shed during menstruation. Stratum basalis: forms new functionalis after menstruation ends, does not respond to ovarian hormones.
  • Vagina: elastic, thin-walled muscular tube lying between the bladder and the rectum, and extends from the cervix to the exterior of the body. Provides a passage way for birth, menstrual flow and is the organ of copulation.
  • Vulva: mons pubis, vestibule (labia major and minora), urethra, vagina, clitoris, glands (Bartholin, skene).
  • Clitoris: erectile, crura, prepuse. Bulb of the vestibule. Small and sensitive, located at top of the vulva just above the urethra and vaginal opening. Provides pleasure to women.  
  • Ovarian cycle: series of events associated w the maturation of an egg correlated to 28 day menstrual cycle. Follicular phase (days 1-14)  is the period of follicle growth. Luteal phase (days 14-28) is the period of corpus luteum activity. Ovulation occurs midcycle (day 14).
  • Ovulation: occurs when ovary wall ruptures and expels the secondary oocyte. Mittelschumerz is a twinge of pain sometimes felt at ovulation. 1-2% of ovulations release more than one secondary oocyte which, if fertilized, results in twins.
  • Luteal phase: after ovulation the ruptured follicle collapses, granulosa cells enlarge, and along w internal thecal cells, form the corpus luteum (which secretes progesterone estrogen and inhibin). If pregnancy does not occur, the corpus luteum degenerates in 10 days, leaving a scar. If pregnancy does occur, the corpus luteum produces hormones until the placenta takes over that role.
  • Menstrual cycle: series of changes that the uterine endometrium goes through each month in response to ovarian hormones in the blood. Days 1-5, menstrual phase: uterus sheds all but deepest part of endometrium. Days 6-14, proliferative phase: endometrium rebuilds. Days 15-28, secretory phase: endometrium prepares for implantation of embryo.
  • Cervical cycle: at the time of ovulation the pH of the cervix rises (becoming more alkaline), and cervical mucous becomes runny. Significance of this relates to fertilisation.
  • Menopause: ovulation and menses cease entirely. Without sufficient oestrogen, reproductive organs and breasts atrophy. Irritability to depression result, skin blood vessels undergo intense vasodilation (hot flushes), gradual thinning of skin and bone loss.


  • Gonads/testes: produce sperm and lie within the scrotum. Sperm is delivered to exterior through a system of ducts including epididymis, ductus deferens, ejaculatory duct and the urethra.
  • Accessory sex glands: empty their secretions into the ducts during ejaculation, and include seminal vesicles, prostate gland and bulbourethral glands.
  • Spermatogenesis: the sequence of events that produce sperm.
  • Gametes: have 23 chromosomes, whereas humans have 23 pairs of chromosomes. Sperm have 3 major regions: 1. Head (contains DNA and contains hydrolytic enzymes that allow the sperm to penetrate and enter the egg), 2. Midpiece (contains mitochondria spiralled around tail filaments), 3. Tail (typical flagellum produced by a centriole).
  • Gamete formation: by meiosis, where the number of chromosomes are halved.
  • Spermatagonia: the stem cells
  • Spermatocyte line: primary and secondary in 2 stages of meiosis
  • Sustentacular (sertoli cells): extend from basal lamina to lumen of the tubule that surrounds developing cells. They support spermatogenesis, providing nutrients to developing sperm. Bound together w tight junctions forming unbroken layer w the seminiferous tubule, dividing it into 2 compartments: basal (contains spermatogonia and primary spermatocytes) and adluminal (meiotically active cells and tubule lumen). The tight junctions form blood-testis barrier, preventing sperm antigens from escaping into the blood. These are absent in males before puberty.
  • Epididymis: head joins efferent ductules and caps the superior aspect of testis. Duct of epididymis has stereocilia that absorb testicular fluid and pass nutrients to sperm. Sperm becomes motile here. The epididymis contracts during ejaculation, where sperm expels thru ductus deferens.
  • Scrotum: sac of skin and superficial facia that hangs outside the abdominopelvic cavity at the root of the penis. Contains testicles separated by a midline septum. It is outside the body to keep them lower than core body temperature.
  • Seminal vesicles: lie on the posterior wall of the bladder and secrete 60% the volume of semen.
  • Semen: viscous alkaline fluid containing fructose, ascorbic acid, coagulating enzyme and prostaglandins. Is a mixture of sperm and accessory gland secretions. Around 2-6ml. provides transport medium and nutrients. Coagulant. Prostaglandins in semen decrease viscosity of mucus in the cervix, stimulate reverse peristalsis in uterus and facilitates the movement of sperm through female reproductive tract. Sperm and seminal fluid mix in the ejaculatory duct and enter prostatic urethra during ejaculation.
  • Prostate gland: milky, slightly acid fluid containing citrate, enzymes and prostate-specific antigen. Accounts for 30% of semen volume. Plays a role in the activation of sperm. Enlarges with age.
  • Bulbourethral glands: duct of each gland travels alongside the spongy urethra. Produces a thick alkaline mucus which helps neutralise the urinary acid. Lubricates the tip of the penis. 5% of semen volume.
  • Urethra: conveys both urine and semen. Consists of 3 regions; prostatic (surrounded by prostate), membranous (lies in the urogenital diaphragm) and penile (runs through penis and opens to outside of external urethral orifice).
  • The penis: designed to deliver sperm into female reproductive tract.
  • Internal penis: urethra and 3 cylindrical bodies of erectile tissue (corpus spongiosum which surrounds the urethra and expands to form the glans and bulb of penis, corpora cavernosa which is bound by fibrous tunica albuginea, crura which is the proximal end of penis surrounded by ischiocavernosus muscle and anchors the penis to the pubic arch.
  • Erectile tissue: spongy network of connective tissue and smooth muscle riddled w vascular spaces.
  • Ejaculation: sympathetic nerves cause reproductive ducts and accessory organs to contract and empty their contents, the bladder sphincter muscle to constrict, preventing the expulsion of urine, bulbospngiosus muscles to undergo a rapid series of contractions, propulsion of semen from the urethra.
  •  Hormone regulation: feedback inhibition on hypothalamus and pituitary gland results from rising levels of testosterone and increased inhibin.
  • Male secondary sex characteristics: male hormones make their appearance at puberty and induce changes in non-reproductive organs including pubic, axillary and facial hair; enhanced growth of chest and deepening of voice; skin thickens and becomes oily; bones grow and increase in density; skeletal muscles increase in size and mass.

These are my study notes from my nursing bachelor at university and the information here is not my own. 

Ovary - Corpus Luteum

Histology image shows the ovary in overview, the cortex and medulla of the ovary can be clearly seen.

Corpus luteum (yellow body) theca lutein cells and granulosa lutein cells. These cells work together in the production of ovarian hormones that support the initial pregnancy.

Corpus albicans (white body) lack of implantation and associated hCG will lead to this structure not producing hormones.

Atretic follicles are the degenerating follicles from various developmental stages that did not form the ovulating follicle and do not form the corpus luteum.