Anatomy & Physiology Study Notes: The Reproductive System (Chapter 25)

Reproductive System

Female Reproductive System

Form and Structure

The female reproductive system consists of organs and structures responsible for producing gametes, supporting fertilization, and nurturing the developing embryo. Key components include the ovaries, uterine tubes, uterus, vagina, and external genitalia.

• Ovaries: Primary female gonads that produce gametes (ova). Small, almond-shaped organs held in place by ligaments and mesenteries (broad ligament, suspensory ligament, ovarian ligament).

• Ovarian Arteries: Provide arterial blood supply to the ovaries.

• Innervation: Ovaries are innervated by both divisions of the autonomic nervous system.

• Internal Structure:

  • Tunica albuginea: Fibrous capsule of the ovary.

  • Cortex: Contains ovarian follicles covered in simple cuboidal epithelium.

  • Medulla: Contains blood vessels, lymph vessels, and nerves.

• Uterine Tubes (Fallopian Tubes): Transport ova from the ovary to the uterus. Regions include:

  • Infundibulum: Funnel-shaped distal end with fimbriae.

  • Ampulla: Expanded middle region, usual site of fertilization.

  • Isthmus: Medial portion adjacent to the uterus.

• Uterus: Muscular organ for embryo implantation and fetal development. Parts include:

  • Fundus: Superior portion.

  • Body: Main portion.

  • Cervix: Inferior neck-like portion.

• Cervical Canal: Communicates with the vagina. Includes:

  • Internal os: Opening to uterine cavity.

  • External os: Inferior opening to cervix.

• Support Structures:

  • Mesometrium: Anchors uterus to lateral pelvic walls.

  • Transverse cervical (cardinal) ligaments: Attach from cervix and vagina.

  • Round ligaments: Bind uterus to anterior body wall.

• Uterine Wall: Composed of three layers:

  • Perimetrium: Serous layer (peritoneum).

  • Myometrium: Interlacing bundles of smooth muscle, contracts during childbirth.

  • Endometrium: Mucosal lining, site of embryo implantation. Has functional and basal layers.

• Vagina: Muscular tube with three layers:

  • Adventitia: Fibrous connective tissue.

  • Muscularis: Smooth muscle.

  • Mucosa: Stratified squamous epithelium, transverse folds (rugae).

  • Hymen: Incomplete diaphragm at vaginal orifice.

• External Genitalia:

  • Labia majora: Encloses labia minora.

  • Vestibule: Enclosed by labia minora, contains openings to urethra and vagina.

  • Clitoris: Erectile tissue, homologous to the penis.

• Female Perineum: Diamond-shaped area bordered by pubic arch, coccyx, and ischial tuberosities.

Function

• Oogenesis: Production of ova (egg cells).

  • Takes many years to complete; primary follicles are arrested in meiosis I until puberty.

  • Each cycle, one ovum and three polar bodies are produced.

  • Oogenesis is regulated by hormonal fluctuations.

• Ovarian Cycle: Monthly maturation of ovarian follicles and ovulation.

  • Follicular Phase: Primordial follicles mature into primary and secondary follicles.

  • Ovulation: Release of mature ovum from ovary (usually day 14 of cycle).

  • Luteal Phase: Remaining follicle becomes corpus luteum, secreting progesterone to prepare uterus for implantation.

• Uterine Cycle: Prepares uterine wall for implantation of embryo.

Male Reproductive System

Form and Structure

The male reproductive system is responsible for producing, storing, and delivering sperm. Major structures include the testes, epididymis, ductus deferens, urethra, and accessory glands.

• Testes: Located within the scrotum, produce sperm and testosterone.

  • Cremaster muscle: Bands of skeletal muscle that elevate the testes.

  • Dartos muscle: Smooth muscle responsible for wrinkling scrotal skin.

  • Tunica vaginalis: Serous sac surrounding the testes.

  • Tunica albuginea: Fibrous capsule of the testes.

• Scrotum: Skin and superficial fascia, maintains testes at a temperature 3°C cooler than body temperature.

• Nerves and Vessels: Testicular arteries and veins, pampiniform plexus (cools arterial blood).

• Microscopic Anatomy:

  • Seminiferous tubules: Sperm-forming tissue, separated by areolar connective tissue.

  • Epithelium contains:

    • Spermatogenic cells: Form sperm; about 400 million sperm/day.

    • Sertoli (sustentacular) cells: Support and nourish developing sperm.

    • Interstitial (Leydig) cells: Secrete testosterone.

• Epididymis: Coiled tube (6 m long) for sperm storage and maturation.

• Ductus deferens: Transports sperm from epididymis to urethra.

• Urethra: Carries sperm to outside; three regions (prostatic, membranous, spongy).

• Accessory Glands:

  • Seminal glands: Secrete 60% of semen volume; contain substances to enhance sperm motility.

  • Prostate: Encircles prostatic urethra; secretes about one-third of semen volume.

  • Bulbo-urethral glands: Inferior to prostate; produce mucus to neutralize traces of acidic urine.

• External Genitalia:

  • Glans penis: Distal expanded end.

  • Prepuce: Foreskin, removed during circumcision.

  • Corpora cavernosa: Paired erectile bodies.

  • Corpus spongiosum: Surrounds spongy urethra.

Function

• Spermatogenesis: Formation of spermatozoa in seminiferous tubules.

  • Stage 1: Spermatogonia divide to form primary spermatocytes.

  • Stage 2: Meiosis I and II produce secondary spermatocytes and spermatids.

  • Stage 3: Spermiogenesis—spermatids differentiate into sperm.

  • Each spermatid sheds excess cytoplasm and forms a tail.

  • Sperm consist of head, midpiece, and tail.

• Additional Players:

  • Sertoli (sustentacular) cells: Form blood-testis barrier, protect developing sperm from immune system.

  • Hormonal Regulation:

    • Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH) regulate spermatogenesis and testosterone secretion.

    • Androgen binding protein: Concentrates testosterone near spermatogenic cells.

    • Inhibin: Inhibits FSH.

Key Terms and Definitions

• Oogenesis: The process of ovum (egg cell) formation in females.

• Spermatogenesis: The process of sperm cell formation in males.

• Corpus luteum: Structure formed from the follicle after ovulation, secretes progesterone.

• Seminiferous tubules: Tubules within the testes where sperm are produced.

• Endometrium: Inner lining of the uterus, site of embryo implantation.

• Testosterone: Main male sex hormone, produced by Leydig cells.

Relevant Equations

• Hormonal Regulation of Spermatogenesis: $ext{FSH} + ext{Testosterone} ightarrow ext{Spermatogenesis}$

• Temperature Regulation in Scrotum: $ext{Testicular Temperature} = ext{Body Temperature} - 3^ ext{o}C$

Comparative Table: Female vs. Male Reproductive Structures

Structure	Female	Male
Gonads	Ovaries	Testes
Gametes	Ova (eggs)	Sperm
Primary Duct	Uterine tubes	Ductus deferens
External Genitalia	Labia, clitoris	Penis, scrotum
Hormones	Estrogen, progesterone	Testosterone

Additional info: Some details, such as the specific days of the ovarian cycle and the hormonal regulation, have been expanded for clarity and completeness.