Female and Male Urogenital System

What are the four functions of the female reproductive system?

1. Produce female gametes (oocytes).

2. Secrete sex hormones, mainly estrogen and progesterone.

3. Receive sperm and provide the site for fertilisation, pregnancy and childbirth.

4. Produce milk to nourish offspring.

What are the organs of the female reproductive system?

• Ovaries

• Uterine (fallopian) tubes

• Uterus

• Cervix

• Vagina

• External genitalia (vulva)

• Mammary glands (accessory reproductive structures)

What structures make up the external genitalia (vulva)?

• Mons pubis: Fatty pad over the pubic symphysis that cushions the pubic bone.

• Labia majora: Outer, hair-bearing skin folds that protect the external genital structures.

• Labia minora: Inner, hairless folds that border and protect the vestibule.

• Clitoris: Erectile organ rich in sensory nerve endings, involved in sexual pleasure.

• Vestibule: Space between the labia minora containing the urethral and vaginal openings.

• Greater vestibular glands: Secrete mucus for lubrication.

• Paraurethral glands: Small glands near the urethral opening that secrete fluid.

What is the perineum?

The diamond-shaped region between the pubic symphysis, coccyx and ischial tuberosities. It is divided into the urogenital triangle anteriorly and the anal triangle posteriorly.

What are the ligamentous connections of the female reproductive organs?

• Broad ligament: Double layer of peritoneum supporting the uterus, uterine tubes and ovaries.

  • Mesovarium: Part of the broad ligament that attaches the ovary to it.

• Round ligament: Extends from the uterus through the inguinal canal to the labia majora; helps maintain uterine position.

• Uterosacral ligaments: Connect the cervix to the sacrum and support the uterus.

• Cardinal ligaments: Connect the cervix and upper vagina to the pelvic walls and support the uterus.

• Ovarian ligament: Connects the ovary to the uterus.

• Suspensory ligament of the ovary: Connects the ovary to the lateral pelvic wall and carries ovarian blood vessels.

Describe the structure and histological features of the vagina.

Muscular tube lined by stratified squamous non-keratinised epithelium. Contains smooth muscle and connective tissue. Lacks glands; lubrication comes from cervical secretions and fluid transudation.

Describe the structure of mammary glands and their role in reproduction.

Mammary glands are modified sweat glands composed of lobes divided into lobules containing milk-producing alveoli. Ducts transport milk to the nipple. Secretory epithelial cells produce milk, while myoepithelial cells contract to eject it. Their role is to nourish offspring through lactation.

What is the common site of fertilisation?

The ampulla of the uterine tube.

Which oogenic cells are present at each stage of meiosis?

• Before meiosis: Oogonia are diploid cells (46 chromosomes) that develop into primary oocytes.

• Meiosis I begins: Primary oocytes enter meiosis I and arrest in prophase I.

• Meiosis I completes: A secondary oocyte and first polar body form. The secondary oocyte has 23 chromosomes, each consisting of two sister chromatids.

• Meiosis II begins: The secondary oocyte enters meiosis II and arrests in metaphase II.

• Meiosis II completes: Following fertilisation, an ovum and second polar body form. The ovum has 23 chromosomes, each consisting of one chromatid.

Describe oogenesis across the female lifespan and how it differs from spermatogenesis.

Oogenesis begins before birth when oogonia divide by mitosis and develop into primary oocytes. These enter meiosis I and arrest in prophase I. From puberty, selected follicles develop during each menstrual cycle. Usually, one primary oocyte completes meiosis I, producing a secondary oocyte and first polar body. The secondary oocyte is ovulated and arrests in metaphase II. Meiosis II completes only if fertilisation occurs.

Unlike spermatogenesis, oogenesis begins before birth, involves prolonged meiotic arrests and produces one functional gamete plus polar bodies. Spermatogenesis begins at puberty and typically produces four functional sperm from each primary spermatocyte.

Describe follicular development during the follicular, ovulation and luteal phases.

• Follicular phase: FSH stimulates follicular growth. Primordial follicles develop into primary, secondary and antral follicles. The dominant follicle matures, and its primary oocyte completes meiosis I.

• Ovulation: The LH surge causes the mature follicle to rupture and release the secondary oocyte, which is arrested in metaphase II and surrounded by the corona radiata.

• Luteal phase: The ruptured follicle becomes the corpus luteum, which secretes progesterone, oestrogen and inhibin.

What happens to the oocyte and follicle after ovulation?

• Oocyte: If fertilised, the secondary oocyte completes meiosis II. If not fertilised, it degenerates.

• Follicle: The ruptured follicle becomes the corpus luteum. If pregnancy does not occur, it degenerates into the corpus albicans, causing ovarian hormone levels to fall. If pregnancy occurs, hCG maintains the corpus luteum during early pregnancy.

What roles do the hypothalamus and pituitary gland play in regulating oogenesis?

The hypothalamus releases gonadotropin-releasing hormone (GnRH), which stimulates the anterior pituitary to release follicle-stimulating hormone (FSH) and luteinising hormone (LH). These hormones regulate follicular development, oocyte maturation, ovulation and ovarian hormone secretion.

Which hormones directly control follicular development, and what are their effects?

• FSH: Stimulates granulosa cell growth, follicular development and estrogen production.

• LH: Stimulates theca cells to produce androgens, triggers ovulation and completion of meiosis I, and promotes corpus luteum formation.

Granulosa cells use aromatase to convert theca-derived androgens into estrogens.

Describe the structure and histological features of the cervix.

Lower, narrow portion of the uterus. The endocervix has mucus-secreting simple columnar epithelium, while the ectocervix has stratified squamous non-keratinised epithelium.

Describe the structure and histological features of the ovaries.

Outer cortex contains follicles at different developmental stages and corpora lutea. Inner medulla contains blood vessels, nerves and connective tissue.

Describe the structure and histological features of the uterine tubes.

Have folded mucosa lined by simple columnar epithelium containing ciliated cells and secretory cells. Smooth muscle helps transport the oocyte towards the uterus.

Three segments: Ampulla, isthmus, and infundibulum

Describe the structure and histological features of the uterus.

Muscular organ with three layers:

• Perimetrium: Outer serosal layer.

• Myometrium: Thick smooth muscle layer responsible for uterine contractions.

• Endometrium: Inner mucosal lining containing glands; changes throughout the menstrual cycle.

Describe the uterine (menstrual) cycle and link it to ovarian hormones.

• Menstrual phase: The functional endometrium is shed because the corpus luteum regresses and progesterone and estrogen levels fall.

• Proliferative phase: Estrogen from developing follicles stimulates endometrial regeneration and thickening.

• Secretory phase: Progesterone from the corpus luteum makes the endometrium glandular, vascular and suitable for implantation.

What are the roles of estrogen, progesterone and inhibin in females?

• Estrogen: Promotes female secondary sexual characteristics, endometrial proliferation and growth of the reproductive organs. Sustained high levels trigger the LH surge through positive feedback.

• Progesterone: Maintains the secretory endometrium, supports early pregnancy and thickens cervical mucus. It also suppresses GnRH, FSH and LH through negative feedback.

• Inhibin: Secreted by granulosa cells and the corpus luteum; selectively inhibits FSH secretion from the anterior pituitary.

Which two hormones affect breast tissue, and what are their roles?

• Estrogen: Stimulates growth of the mammary ducts.

• Progesterone: Stimulates development of the lobules and alveoli in preparation for lactation.

How does the combined oral contraceptive pill work?

The combined pill contains synthetic estrogen and progestogen. These hormones exert negative feedback on the hypothalamus and anterior pituitary, suppressing FSH and LH release. This prevents follicular maturation and the LH surge required for ovulation. Progestogen also thickens cervical mucus, making sperm penetration more difficult, and alters the endometrium, making implantation less favourable.

What are the organs of the male reproductive system?

• Testes

• Epididymides

• Ductus (vas) deferens

• Ejaculatory ducts

• Urethra

• Penis

• Scrotum

• Accessory glands: seminal vesicles, prostate gland and bulbourethral glands.

What structures are found in the spermatic cord?

• Ductus deferens

• Testicular artery

• Pampiniform venous plexus

• Autonomic nerves

• Lymphatic vessels

• Cremasteric artery and artery of the ductus deferens.

The spermatic cord suspends the testis and carries structures between the abdominal/pelvic region and the testis.

Describe the structure and role of the testes in sperm formation.

The testes are paired organs within the scrotum. Each testis contains lobules containing coiled seminiferous tubules, where sperm are produced. Sertoli cells support developing sperm, while Leydig cells in the interstitial tissue secrete testosterone in response to LH.

Describe the duct pathway sperm travel from formation to the outside.

Seminiferous tubules → straight tubules → rete testis → efferent ductules → epididymis → ductus deferens → ejaculatory duct → prostatic urethra → membranous urethra → spongy (penile) urethra → external urethral opening.

Describe the structure and role of the epididymis.

The epididymis is a long, highly coiled duct along the posterior surface of each testis, divided into head, body and tail. It allows sperm to mature, acquire motility, be stored and be transported to the ductus deferens.

Which scrotal structures regulate testicular temperature, and why is this important?

• Dartos muscle: Contracts to wrinkle the scrotal skin, reducing heat loss.

• Cremaster muscle: Raises or lowers the testes to regulate temperature.

• Pampiniform plexus: Cools incoming arterial blood through countercurrent heat exchange.

The testes are maintained approximately 2–3°C below core body temperature because normal sperm production requires a cooler environment.

Name the male accessory glands and describe their locations.

• Seminal vesicles: Paired glands posterior to the urinary bladder and superior to the prostate.

• Prostate gland: Located inferior to the bladder, surrounding the first part of the urethra.

• Bulbourethral glands: Paired glands inferior to the prostate, within the deep perineal region; their ducts open into the spongy urethra.

Describe the composition of semen.

Semen consists of spermatozoa suspended in seminal fluid from the accessory glands.

• Seminal vesicles: Produce fructose for energy, prostaglandins and seminal coagulation proteins; contribute most of the semen volume.

• Prostate: Produces fluid containing citrate, enzymes such as PSA and other substances that support sperm function and semen liquefaction.

• Bulbourethral glands: Secrete mucus that lubricates and helps neutralise residual acidity in the urethra.

• Testes and epididymides: Supply spermatozoa.

Describe the structure of the penis.

The penis contains three columns of erectile tissue:

• Two corpora cavernosa: Main erectile bodies responsible for rigidity.

• One corpus spongiosum: Surrounds the spongy urethra and prevents its compression during erection.

• Glans penis: Expanded distal end of the corpus spongiosum.

What is the process by which sperm become fully functional and motile?

• Epididymal maturation: Sperm develop the capacity for progressive motility and acquire functional changes during passage through the epididymis.

• Capacitation: Occurs after ejaculation within the female reproductive tract. Changes to the sperm membrane, including removal or rearrangement of surface proteins and cholesterol, increase motility and enable the acrosome reaction and fertilisation.

Which spermatogenic cells are present at each stage of meiosis?

• Spermatogonia: Diploid cells (46 chromosomes) that divide by mitosis.

• Primary spermatocytes: Diploid cells that enter meiosis I after DNA replication.

• Secondary spermatocytes: Haploid cells (23 chromosomes, each with two sister chromatids) produced by meiosis I.

• Spermatids: Haploid cells (23 chromosomes, each with one chromatid) produced by meiosis II.

• Spermatozoa: Mature-form sperm cells produced when spermatids undergo spermiogenesis.

One primary spermatocyte normally produces four haploid spermatids.

Describe the structure of the seminiferous tubule

Seminiferous tubules are coiled tubes within the testicular lobules. Their walls contain a germinal epithelium made up of developing sperm cells and Sertoli cells, supported by a basement membrane and surrounding peritubular cells.

What is the blood-testis barrier, and why is it important?

The blood-testis barrier is formed by tight junctions between adjacent Sertoli cells. It separates the seminiferous epithelium into basal and adluminal compartments.

It protects developing haploid germ cells from immune attack, maintains a specialised environment for meiosis and sperm development, and regulates which substances enter the adluminal compartment.

What is the difference between spermatogenesis and spermiogenesis?

• Spermatogenesis: The overall process of producing sperm from spermatogonia, including mitosis, meiosis and differentiation.

• Spermiogenesis: The final stage of spermatogenesis, in which haploid spermatids transform into spermatozoa without further cell division.

Describe the structure of a mature spermatozoon and how each part reflects its function.

• Head: Contains the haploid nucleus carrying paternal genetic information.

• Acrosome: Enzyme-containing cap that helps sperm penetrate the egg's surrounding coverings.

• Neck: Connects the head to the midpiece and contains connecting structures.

• Midpiece: Contains mitochondria that generate ATP for movement.

• Tail (flagellum): Contains a microtubule-based axoneme that produces movement and propels sperm.

• Plasma membrane: Enables interactions with the female reproductive tract and the oocyte.

What roles do the hypothalamus and pituitary gland play in regulating spermatogenesis?

The hypothalamus secretes gonadotropin-releasing hormone (GnRH), stimulating the anterior pituitary to release FSH and LH. FSH acts on Sertoli cells, while LH acts on Leydig cells to stimulate testosterone production. FSH and testosterone work together to support spermatogenesis.

What are the target cells of FSH and LH in males, and how do these hormones affect them?

• FSH targets Sertoli cells: Promotes Sertoli cell function, ABP and inhibin B secretion, and support of developing sperm.

• LH targets Leydig cells: Stimulates testosterone synthesis and secretion.

Testosterone acts locally within the testes and is essential for normal sperm production.

What is the role of androgen-binding protein (ABP), and which cells secrete it?

ABP is secreted by Sertoli cells in response to FSH. It binds testosterone within the seminiferous tubules, maintaining a high local testosterone concentration needed for normal spermatogenesis.

What is the role of inhibin in feedback regulation of spermatogenic activity?

Sertoli cells secrete inhibin B in response to spermatogenic activity and FSH stimulation. Inhibin B acts on the anterior pituitary to selectively suppress FSH secretion through negative feedback, helping regulate sperm production.

What is testosterone chemically, and how does this affect its transport and action?

Testosterone is a steroid hormone derived from cholesterol. It is lipid-soluble, so it travels in the blood mainly bound to sex hormone-binding globulin (SHBG) and albumin, with a small free fraction.

It crosses cell membranes and binds intracellular androgen receptors. The hormone-receptor complex regulates gene transcription and protein synthesis. Testosterone can also be converted into dihydrotestosterone (DHT) or oestradiol in certain tissues.

What are the effects of testosterone on the seminiferous tubules and the whole body?

Within the testes:

• Works with FSH to support spermatogenesis.

• Promotes meiosis and the development of spermatids into spermatozoa.

• Maintains the function of Sertoli cells and the seminiferous epithelium.

Throughout the body:

• Develops and maintains male reproductive organs and accessory glands.

• Supports libido and sexual function.

• Promotes facial and body hair growth and a deeper voice at puberty.

• Increases muscle mass and protein synthesis.

• Supports bone growth, density and maintenance.

• Stimulates red blood cell production.

• Contributes to male-pattern body composition and secondary sexual characteristics.

Describe the roles of Sertoli cells.

• Support and nourish developing sperm.

• Form the blood-testis barrier.

• Secrete androgen-binding protein (ABP).

• Secrete inhibin B to regulate FSH.

• Remove residual cytoplasm by phagocytosis.

• Secrete testicular fluid to assist sperm transport.

• Help regulate spermatogenesis and release sperm into the tubule lumen (spermiation).

Describe the neural and vascular events leading to erection and ejaculation.

Erection: Sexual stimulation activates parasympathetic pathways. Nitric oxide relaxes smooth muscle in penile arteries and erectile tissue, increasing blood flow and trapping blood in the erectile spaces.

Emission: Sympathetic stimulation moves sperm and glandular secretions into the prostatic urethra and closes the bladder neck to prevent retrograde ejaculation.

Ejaculation: Sympathetic pathways and somatic motor activity produce rhythmic contractions of the reproductive ducts, accessory glands and pelvic floor muscles, expelling semen through the urethra.