49-55 Reproductive System

Male Reproductive System. Testis. Embryonic Development. Macroscopic, Microscopic, Ultramicroscopic and Functional Characteristics.

Male Reproductive System

• Consists of primary sex organs (testes) and accessory structures (epididymis, vas deferens, seminal vesicles, prostate gland, bulbourethral glands, penis).

• Functions:

  • Spermatogenesis: Production of spermatozoa in testes.

  • Hormone secretion: Mainly testosterone from Leydig cells.

  • Sperm maturation, storage, and transport via the epididymis and vas deferens.

  • Ejaculation through the urethra during sexual activity.

Embryonic Development

• Originates from the genital ridge in the posterior abdominal wall (mesodermal origin).

• SRY gene on Y chromosome induces differentiation into testis.

• Leydig cells begin producing testosterone ~8th week.

• Sertoli cells produce Anti-Müllerian Hormone (AMH), causing regression of paramesonephric (Müllerian) ducts.

• Testes descend into the scrotum via the inguinal canal, guided by the gubernaculum.

Macroscopic Characteristics

• Paired, oval organs (~4–5 cm long, 2.5 cm wide, 3 cm thick).

• Surrounded by:

  • Tunica vaginalis (outer serous layer).

  • Tunica albuginea (fibrous capsule forming septa that divide testis into ~250 lobules).

• Each lobule contains 1–4 seminiferous tubules.

Microscopic Characteristics

• Seminiferous tubules: Site of spermatogenesis.

• Lined with:

  • Spermatogenic cells: In stages from spermatogonia to spermatids.

  • Sertoli cells: Support, protect, and nourish germ cells.

• Interstitial tissue: Contains Leydig cells: Produce testosterone in response to LH.

Ultramicroscopic Characteristics

• Sertoli cells:

  • Large, irregular nuclei with prominent nucleoli.

  • Tight junctions form the blood-testis barrier.

• Leydig cells: Abundant smooth ER, lipid droplets, mitochondria with tubular cristae for steroid synthesis.

• Developing spermatozoa show distinct acrosomes, flagella, and nuclear condensation.

Functional Characteristics

• Spermatogenesis: Regulated by FSH and testosterone; occurs from basal to luminal side.

• Endocrine function: Leydig cells secrete testosterone for secondary sex characteristics and sperm production.

Male Reproductive System. Epididymis. Embryonic Development. Macroscopic, Microscopic, Ultramicroscopic and Functional Characteristics.

Embryonic Development

• Arises from the mesonephric (Wolffian) duct.

• Develops into a long, coiled duct adjacent to the testis.

• Connects rete testis to vas deferens through efferent ductules.

Macroscopic Characteristics

• Comma-shaped organ lying on the posterolateral testis.

• Divided into:

  • Head (caput): Receives sperm from efferent ductules.

  • Body (corpus): Curved central portion.

  • Tail (cauda): Continuous with vas deferens; stores mature sperm.

Microscopic Characteristics

• Lined with pseudostratified columnar epithelium with stereocilia (long microvilli).

• Surrounded by layers of smooth muscle that increase in thickness from head to tail.

• Sperm mature as they travel through the duct.

Ultramicroscopic Characteristics

• Principal cells:

  • Have stereocilia (for absorption/secretion).

  • Prominent Golgi and endoplasmic reticulum for protein modification.

• Basal cells: Provide support and regeneration.

• Sperm undergo surface membrane changes to gain motility and fertilizing capacity.

Functional Characteristics

• Sperm maturation:

  • Gain motility, ability to recognize and fertilize the egg.

• Sperm storage: Tail acts as reservoir before ejaculation.

• Absorption of testicular fluid and phagocytosis of defective sperm.

Male Reproductive System. Testis and Epididymis. Blood-Testicular Barrier. Blood and Nerve Supply.

Blood-Testis Barrier

• Formed by tight junctions between Sertoli cells.

• Divides seminiferous tubule into:

  • Basal compartment: Early spermatogonia.

  • Adluminal compartment: Later stages (primary spermatocytes onward).

• Protects germ cells from immune surveillance and toxins.

Blood and Nerve Supply of Testis

• Arterial: Testicular artery (from abdominal aorta).

• Venous: Pampiniform plexus → testicular vein → renal or IVC.

• Nerve: Autonomic (sympathetic from T10–T11); regulates blood flow and hormonal release.

Blood and Nerve Supply of Epididymis

• Arterial: Branches from testicular, deferential, and cremasteric arteries.

• Venous: Drains into pampiniform plexus.

• Nerve: Autonomic innervation regulates smooth muscle for sperm transport.

Male Reproductive System. Ductus Deferens. Macroscopic, Microscopic, Ultramicroscopic and Functional Characteristics. Blood and Nerve Supply.

Macroscopic Characteristics

• A thick-walled, muscular tube (~45 cm long).

• Extends from epididymis tail to ejaculatory duct.

• Runs through the spermatic cord, over the bladder, and merges with the seminal vesicle duct.

Microscopic Characteristics

• Lined with pseudostratified columnar epithelium with stereocilia.

• Surrounded by three muscular layers (inner longitudinal, middle circular, outer longitudinal).

Ultramicroscopic Characteristics

• Epithelial cells have:

  • Basal nuclei.

  • Numerous mitochondria.

  • Prominent stereocilia for absorption and secretion.

Functional Characteristics

• Conveys sperm from epididymis to ejaculatory duct during ejaculation via strong peristaltic contractions.

• Also absorbs fluid and secretes nutrients.

Blood and Nerve Supply

• Arterial: Deferential artery (from inferior vesical artery).

• Venous: Accompanies artery, drains into pelvic venous plexus.

• Nerve: Sympathetic fibers (T12–L2); regulate contraction during ejaculation.

Male Reproductive System. Seminal Vesicles. Macroscopic, Microscopic, Ultramicroscopic and Functional Characteristics. Blood and Nerve Supply.

Macroscopic Characteristics

• Paired, coiled tubular glands (~5 cm long; uncoiled up to 15 cm).

• Located posterior to bladder, lateral to vas deferens.

• Join vas deferens to form ejaculatory ducts.

Microscopic Characteristics

• Lined by pseudostratified columnar epithelium.

• Wall has a highly folded mucosa, surrounded by smooth muscle.

Ultramicroscopic Characteristics

• Secretory cells with:

  • Large Golgi complexes.

  • Rough ER.

  • Secretory granules containing fructose, prostaglandins, and coagulating proteins.

Functional Characteristics

• Secrete ~60–70% of seminal fluid volume.

• Fluid contains fructose (energy for sperm), prostaglandins (stimulate uterine contractions), and clotting proteins (help semen coagulate after ejaculation).

Blood and Nerve Supply

• Arterial: Inferior vesical and middle rectal arteries.

• Venous: Vesical and prostatic venous plexuses.

• Nerve: Autonomic (sympathetic for secretion and contraction).

Male Reproductive System. Prostate Gland. Macroscopic, Microscopic, Ultramicroscopic and Functional Characteristics. Blood and Nerve Supply.

Macroscopic Characteristics

• Single, walnut-sized gland (~4 x 3 x 2 cm).

• Surrounds prostatic urethra.

• Composed of central, peripheral, transitional, and anterior fibromuscular zones.

Microscopic Characteristics

• Glandular tissue in lobules, lined by simple to pseudostratified columnar epithelium.

• Contains corpora amylacea (calcified glycoprotein concretions, increase with age).

• Dense fibromuscular stroma.

Ultramicroscopic Characteristics

• Secretory cells rich in:

  • Secretory granules.

  • Lysosomes.

  • Lipofuscin (aging pigment).

• Secretes enzymes (e.g., PSA – prostate-specific antigen).

Functional Characteristics

• Produces ~25–30% of seminal fluid.

• Secretion includes:

  • Citrate, zinc, proteolytic enzymes (liquefy semen).

  • PSA helps sperm motility and breaks down semen clot.

• Contracts during ejaculation to expel fluid into urethra.

Blood and Nerve Supply

• Arterial: Inferior vesical, middle rectal, and internal pudendal arteries.

• Venous: Prostatic venous plexus → internal iliac vein.

• Nerve: Inferior hypogastric plexus (both sympathetic and parasympathetic).

Male Reproductive System. Bulbourethral Glands. Macroscopic, Microscopic, Ultramicroscopic and Functional Characteristics. Blood and Nerve Supply.

Cowper’s Glands

Macroscopic Characteristics

• Small, pea-sized paired glands (~0.5 cm).

• Located in deep perineal pouch, posterolateral to membranous urethra.

• Ducts open into spongy (penile) urethra.

Microscopic Characteristics

• Tubuloalveolar glands lined by simple columnar epithelium.

• Surrounded by smooth muscle and fibrous capsule.

Ultramicroscopic Characteristics

• Cells contain:

  • Large mucous granules.

  • Abundant Golgi and ER for glycoprotein secretion.

Functional Characteristics

• Secrete pre-ejaculate (mucus):

  • Lubricates urethra.

  • Neutralizes residual acidity.

• Prepares urethra for passage of sperm.

Blood and Nerve Supply

• Arterial: Branches from internal pudendal artery.

• Venous: Drains into perineal venous plexus.

• Nerve: Pudendal nerve and autonomic fibers (for secretion).

Male Reproductive System. Penis. Macroscopic, Microscopic, Ultramicroscopic and Functional Characteristics. Blood and Nerve Supply.

Macroscopic Characteristics

• External genital organ used for copulation and urination.

• Composed of:

  • Root: Fixed part, attached to perineal structures.

  • Body (shaft): Free portion, contains erectile tissue.

  • Glans penis: Expanded distal end, covered by prepuce (foreskin).

• Contains three erectile bodies:

  • 2 corpora cavernosa (dorsally placed).

  • 1 corpus spongiosum (ventrally placed; surrounds urethra and forms glans).

Microscopic Characteristics

• Corpora cavernosa: Surrounded by tunica albuginea; contain vascular sinuses (cavernous spaces) lined by endothelium.

• Corpus spongiosum: Similar structure but thinner tunica; prevents urethral compression.

• Skin: Thin, loose, hairless; contains sebaceous glands.

• Glans: Covered by mucosa-like stratified squamous epithelium.

Ultramicroscopic Characteristics

• Endothelial cells lining sinusoids are fenestrated and regulate blood inflow.

• Smooth muscle cells in trabeculae and helicine arteries mediate erection via nitric oxide-induced relaxation.

• Nerve endings: Especially dense in glans for tactile sensation.

Functional Characteristics

• Erection: Parasympathetic-mediated dilation of penile arteries; corpora fill with blood, causing rigidity.

• Ejaculation: Sympathetic-mediated contraction of ducts and glands.

• Urination: Conducts urine from bladder via urethra.

Blood and Nerve Supply

• Arterial: Branches of internal pudendal artery:

  • Deep artery (corpora cavernosa),

  • Dorsal artery (glans and skin),

  • Bulbourethral artery (corpus spongiosum).

• Venous: Deep dorsal vein → prostatic venous plexus.

• Nerve:

  • Sensory: Dorsal nerve of penis (from pudendal nerve, S2–S4).

  • Autonomic:

    • Parasympathetic (pelvic splanchnics, S2–S4): for erection.

    • Sympathetic (hypogastric plexus): for ejaculation.

Male Reproductive System. Male Urethra. Macroscopic, Microscopic, Ultramicroscopic and Functional Characteristics. Blood and Nerve Supply.

Macroscopic Characteristics

• ~18–20 cm long; shared by urinary and reproductive systems.

• Divided into four parts:

  1. Preprostatic (intramural): ~1 cm, within bladder neck.

  2. Prostatic urethra: ~3–4 cm, passes through prostate.

  3. Membranous urethra: ~1 cm, in deep perineal pouch; shortest and narrowest.

  4. Spongy (penile) urethra: ~15 cm, within corpus spongiosum.

Microscopic Characteristics

• Epithelium varies:

  • Transitional in preprostatic and prostatic parts.

  • Pseudostratified/columnar in membranous and proximal spongy parts.

  • Stratified squamous in distal spongy urethra and external meatus.

• Surrounded by connective tissue and smooth muscle, especially in membranous and spongy segments.

Ultramicroscopic Characteristics

• Epithelial cells vary with region:

  • Columnar cells contain secretory vesicles.

  • Basal cells for regeneration.

• Rich innervation in glans/meatus area for sensory response.

Functional Characteristics

• Urinary function: Conducts urine from bladder to exterior.

• Reproductive function: Transports semen during ejaculation.

• Mucous glands (e.g., Littre’s glands) secrete mucus to protect urethral lining and aid sperm passage.

Blood and Nerve Supply

• Arterial:

  • Preprostatic/prostatic: Inferior vesical artery.

  • Membranous: Bulbourethral and middle rectal arteries.

  • Spongy: Dorsal and deep arteries of the penis.

• Venous: Drains into prostatic and internal pudendal venous plexuses.

• Nerve:

  • Sympathetic and parasympathetic fibers (via prostatic and pudendal plexuses).

  • Somatic sensory from pudendal nerve (S2–S4), especially for external sphincter and penile urethra.

Female Reproductive System. Ovary. Embryonic Development. Macroscopic, Microscopic, Ultramicroscopic and Functional Characteristics. Blood and Nerve Supply.

Embryonic Development

• Develops from the genital ridge (intermediate mesoderm) during 5th–6th week of embryogenesis.

• Primordial germ cells migrate from the yolk sac to the gonadal ridge.

• By week 20 of gestation, all primary oocytes are formed; they remain arrested in prophase I of meiosis until puberty.

• Müllerian ducts form the rest of the female reproductive tract.

Macroscopic Characteristics

• Paired, almond-shaped organs (~3 cm x 1.5 cm x 1 cm).

• Located in the ovarian fossa on each lateral pelvic wall.

• Covered by a thin germinal epithelium (simple cuboidal cells).

• Shows a clear division into:

  • Cortex: houses follicles in various stages.

  • Medulla: contains blood vessels, lymphatics, and nerves.

Microscopic Characteristics

• Surface epithelium: simple cuboidal to squamous cells (mesothelium).

• Tunica albuginea: dense connective tissue beneath the epithelium.

• Cortex: contains ovarian follicles (primordial to Graafian), corpus luteum, and corpus albicans.

• Medulla: loose connective tissue, rich in blood vessels and nerves.

Ultramicroscopic Characteristics

• Follicular cells: granulosa cells with abundant smooth and rough ER, active steroidogenesis.

• Theca cells: lipid droplets, mitochondria with tubular cristae for hormone synthesis.

• Oocyte: large nucleus (germinal vesicle), cortical granules, zona pellucida.

Functional Characteristics

• Exocrine function: production and release of ova (oogenesis and ovulation).

• Endocrine function: secretion of hormones (estrogen, progesterone, inhibin).

• Folliculogenesis and corpus luteum formation are cyclic and hormone-regulated.

• Supports menstrual cycle, pregnancy, and secondary sexual characteristics.

Blood Supply

• Ovarian artery (from abdominal aorta) – main supply.

• Uterine artery (from internal iliac artery) – collateral supply.

• Venous drainage via Ovarian vein: right drains to IVC, left to left renal vein.

Female Reproductive System. Uterine Tubes (Oviducts). Embryonic Development. Macroscopic, Microscopic, Ultramicroscopic and Functional Characteristics. Blood and Nerve Supply.

Embryonic Development

• Derived from the cranial portion of the paramesonephric (Müllerian) ducts.

• Form during weeks 6–7 of embryogenesis.

• The unfused cranial ends of the Müllerian ducts remain open to the coelomic cavity, forming the uterine tubes.

• Differentiation influenced by the absence of anti-Müllerian hormone (AMH) in genetic females (XX).

Macroscopic Characteristics

• Paired muscular tubes ~10–12 cm long, extending from ovaries to uterine horns.

• Divided into four anatomical parts:

  1. Infundibulum: funnel-shaped, with fimbriae that sweep the ovum from the ovary.

  2. Ampulla: longest, widest segment where fertilization usually occurs.

  3. Isthmus: narrow, medial third.

  4. Intramural (interstitial): passes through the uterine wall to open into the uterine cavity.

Microscopic Characteristics

• Mucosa: highly folded, lined by simple columnar epithelium:

  • Ciliated cells: move the ovum toward the uterus.

  • Peg (secretory) cells: produce nutrients for the gamete and zygote.

• Muscularis: inner circular and outer longitudinal smooth muscle layers; peristalsis helps ovum movement.

• Serosa: outer layer, derived from visceral peritoneum.

Ultramicroscopic Characteristics

• Ciliated cells: contain abundant mitochondria, basal bodies, and motile cilia with a 9+2 microtubule arrangement.

• Peg cells: rich in rough ER, Golgi, and secretory vesicles; contribute to tubal fluid.

• Tight junctions and microvilli increase surface area and fluid exchange efficiency

Functional Characteristics

• Transports ovum from ovary to uterus via ciliary action and peristalsis.

• Site of fertilization (typically in ampulla).

• Provides a nourishing environment for gametes and early zygote.

• Prevents ectopic implantation through selective motility and secretions.

Blood Supply

• Arterial supply:

  • Tubal branches of the ovarian artery (from abdominal aorta).

  • Tubal branches of the uterine artery (from internal iliac artery).

• Rich anastomosis between the two sources.

• Venous drainage parallels arteries via ovarian and uterine veins.

Nerve Supply

• Autonomic innervation from ovarian and uterine plexuses.

  • Sympathetic fibers: T10–L2 segments (vasomotor control, pain).

  • Parasympathetic fibers: from pelvic splanchnic nerves (S2–S4).

• Sensory innervation transmits visceral pain, often referred to lower abdomen or groin.

Female Reproductive System. Uterus. Macroscopic, Microscopic, Ultramicroscopic and Functional Characteristics of the Wall. Blood and Nerve Supply.

Macroscopic Characteristics

• Pear-shaped, hollow muscular organ, ~7.5 cm long, 5 cm wide.

• Located in the pelvic cavity between bladder and rectum.

• Divided into:

  • Fundus: dome-shaped top.

  • Body: main portion; site of implantation.

  • Isthmus: narrow area before cervix.

  • Cervix: opens into vagina.

• Has three layers: endometrium, myometrium, and perimetrium.

Microscopic Characteristics of Uterine Wall

• Endometrium: inner mucosal layer

  • Lined by simple columnar epithelium (ciliated and secretory cells).

  • Contains uterine glands, stroma, and spiral arteries.

• Myometrium: thick muscular layer

  • Bundles of smooth muscle interlaced with blood vessels.

  • Contracts during menstruation and labor.

• Perimetrium: outer serosal layer

  • Consists of mesothelium and thin connective tissue.

Ultramicroscopic Characteristics

• Endometrial epithelial cells: have microvilli and cilia; secretory cells rich in ER and Golgi.

• Stromal cells: fibroblast-like, undergo decidualization in pregnancy.

• Myometrial cells: rich in actin and myosin filaments; connected by gap junctions to coordinate contractions.

Functional Characteristics

• Site for implantation, fetal development, and labor.

• Cyclical changes in endometrium regulated by ovarian hormones (estrogen and progesterone).

• Contracts to expel contents during menstruation, parturition, and involution.

Blood Supply

• Arterial supply:

  • Uterine artery (from internal iliac artery) – main source.

  • Anastomoses with ovarian artery branches.

  • Radial arteries → spiral arteries supply endometrium.

• Venous drainage:

  • Via uterine veins into internal iliac vein.

Nerve Supply

• Sympathetic: from hypogastric plexus – controls vasoconstriction and contraction.

• Parasympathetic: via pelvic splanchnic nerves (S2–S4) – modulates relaxation.

• Sensory innervation: to T10–L1 (body), S2–S4 (cervix) – pain during menstruation/labor.

Female Reproductive System. Ovario-Menstrual Cycle. Microscopic and Functional Characteristics of the Four Phases.

Ovario-Menstrual Cycle (28-Day Cycle)

1. Menstrual Phase (Days 1–4)

• Microscopic:

  • Shedding of functional layer of endometrium due to progesterone withdrawal.

  • Spiral arteries constrict → ischemia → tissue necrosis and bleeding.

• Functional:

  • Menstrual bleeding occurs.

  • Loss of endometrial glands and surface epithelium.

2. Proliferative (Follicular) Phase (Days 5–14)

• Microscopic:

  • Under estrogen influence (from growing follicles).

  • Endometrium regenerates: glands are straight, stroma cellular, arteries elongate.

• Functional:

  • Prepares endometrium for potential implantation.

  • Cervical mucus becomes thinner to favor sperm passage.

3. Secretory (Luteal) Phase (Days 15–28)

• Microscopic:

  • Under progesterone from corpus luteum.

  • Glands become coiled and secrete glycogen-rich fluid.

  • Spiral arteries further develop.

• Functional:

  • Optimal implantation window (~Day 20–24).

  • Cervical mucus thickens to prevent pathogen/sperm entry.

4. Ischemic Phase (Late Day 27–28, if no implantation)

• Microscopic:

  • Progesterone drops → spiral arteries constrict → ischemia.

  • Endometrial cells die → start of menstrual shedding.

• Functional:

  • Transition to menstruation if fertilization doesn't occur.

Female Reproductive System. Vagina. Macroscopic, Microscopic, Ultramicroscopic and Functional Characteristics. Blood and Nerve Supply

Macroscopic Characteristics

• Muscular, fibromuscular canal (~7–10 cm in length).

• Extends from vulva to cervix.

• Posterior to urethra and bladder, anterior to rectum.

Microscopic Characteristics

• Mucosa: non-keratinized stratified squamous epithelium; rich in glycogen.

• Lamina propria: elastic fibers, lymphocytes.

• Muscular layer: inner circular and outer longitudinal smooth muscle.

• Adventitia: connective tissue with blood vessels, lymphatics, and nerves.

Ultramicroscopic Characteristics

• Tight junctions and desmosomes between epithelial cells.

• Glycogen metabolized by Lactobacillus → lactic acid → acidic pH (~3.8–4.5).

• Numerous mitochondria in epithelial cells for energy production.

Functional Characteristics

• Passage for menstrual flow, childbirth, and intercourse.

• Self-cleaning due to acidic environment and discharge.

• Expands significantly during intercourse and delivery.

Blood Supply

• Arterial: Vaginal artery (from internal iliac), uterine artery branches.

• Venous: Vaginal venous plexus → internal iliac vein.

Nerve Supply

• Pudendal nerve (somatic).

• Uterovaginal plexus (autonomic).

Female Reproductive System. External Genital Organs. Macroscopic, Microscopic, Ultramicroscopic and Functional Characteristics. Blood and Nerve Supply

Vulva

Components

• Mons pubis, labia majora, labia minora, clitoris, vestibule, Bartholin’s glands.

Macroscopic Characteristics

• Labia majora: fatty folds, hair-bearing.

• Labia minora: hairless, vascularized.

• Clitoris: erectile tissue (analogous to penis).

• Vestibule: area containing vaginal and urethral openings.

Microscopic Characteristics

• Labia majora: keratinized stratified squamous epithelium, sebaceous and sweat glands.

• Labia minora: non-keratinized epithelium internally, keratinized externally.

• Clitoris: cavernous erectile tissue, rich in nerve endings.

Ultramicroscopic Characteristics

• Rich innervation (especially in clitoris) with Meissner’s and Pacinian corpuscles.

• Vascular sinuses in erectile tissues.

Functional Characteristics

• Protection of internal genitalia.

• Sexual arousal (especially clitoris).

• Lubrication (via Bartholin’s glands).

Blood Supply

• Arterial: External and internal pudendal arteries.

• Venous: Pudendal veins → internal iliac vein.

Nerve Supply

• Somatic: Pudendal nerve (S2–S4) – sensory and motor.

• Autonomic: Ilioinguinal and genitofemoral nerves (partial sensory).