Anatomy & Physiology Study Notes: The Reproductive System

The Reproductive System

Overview

The reproductive system is responsible for producing, storing, nourishing, and transporting reproductive cells (gametes) in both males and females. It also supports the development of offspring. This system includes primary sex organs, accessory structures, and external genitalia.

• Female Reproductive System: Ovaries, uterine tubes, uterus, vagina, perineum, and external genitalia

• Male Reproductive System: Testes, epididymis, ductus deferens, accessory glands, penis, scrotum, and perineum

• Development of Sex Organs: Embryological differentiation and descent

Female Reproductive System

Internal Genital Organs

The internal genital organs of the female reproductive system are essential for gamete production, fertilization, and supporting embryonic development.

• Ovaries: Produce ova (egg cells) and reproductive hormones

• Uterine Tubes (Fallopian Tubes): Site of fertilization; transport oocyte

• Uterus: Site for embryo development

• Vagina: Birth canal and organ for sexual intercourse

External Genitalia

• Mons pubis: Fatty area over pubic symphysis, covered by pubic hair after puberty

• Labia majora: Homologous to male scrotum; encloses labia minora

• Labia minora: Encloses vestibule; contains external urethral and vaginal orifices

• Clitoris: Erectile tissue homologous to penis

Menstrual Cycle

The menstrual cycle is a monthly process affecting female reproductive organs, involving hormonal regulation of ovarian and uterine cycles.

The Ovaries

Gross Anatomy

• Small, almond-shaped organs that produce ova and hormones

• Ligaments and Mesenteries:

  • Ovarian ligament: Anchors ovary to uterus

  • Suspensory ligament: Contains ovarian arteries

  • Broad ligament: Includes mesovarium, mesosalpinx, mesometrium

Microscopic Anatomy

• Tunica albuginea: Fibrous capsule covered by germinal epithelium (simple cuboidal)

• Ovarian cortex: Houses developing oocytes in follicles

• Follicles: Multicellular sacs containing oocytes

• Ovarian medulla: Loose connective tissue with blood vessels, lymphatics, and nerves

The Uterine Tubes

Structure and Function

• Also called oviducts or fallopian tubes

• Transport oocyte from ovary to uterus

• Common site of fertilization

• Infundibulum: Trumpet-shaped distal end surrounded by motile fimbriae

Microscopic Anatomy

• Mucosa:

  • Ciliated simple columnar epithelium – cilia propel oocyte

  • Non-ciliated simple columnar epithelium – secretes nutrients for oocyte

• Muscularis: Two layers of smooth muscle generate peristaltic waves to move oocyte

The Uterus

Gross Anatomy

• Located anterior to rectum, posterior to bladder

• Fundus: Rounded superior portion

• Cervix: "Neck" of uterus; cervical canal opens into vagina; external os is the opening

Supporting Structures

• Broad ligament: Anchors uterus to lateral pelvic walls

• Lateral cervical (cardinal) ligaments: Horizontal from cervix and vagina

• Round ligaments: Bind uterus to anterior body wall

• Chiefly supported by pelvic floor

Uterine Wall

• Perimetrium: Serous layer (peritoneum)

• Myometrium: Interlacing bundles of smooth muscle; contracts during childbirth

• Endometrium: Mucosal lining; includes functional and basal layers; functional layer is shed during menstruation

Blood Supply

• Uterine arteries: Send arcuate branches to uterine wall

• Radial arteries: Branch into straight arteries (basal layer) and spiral arteries (functional layer)

• Spiral arteries undergo degeneration and regeneration each menstrual cycle

The Vagina

Structure

• Adventitia: Fibrous connective tissue

• Muscularis: Smooth muscle

• Mucosa: Transverse folds; lamina propria with elastic fibers; lined by stratified squamous epithelium

Female Perineum & External Genitalia

Perineum

• Diamond-shaped area bounded by:

  • Anterior: pubic arch

  • Posterior: coccyx

  • Lateral: ischial tuberosities

  • Superior: pelvic diaphragm

• Divided into urogenital (UG) triangle and anal triangle

External Genitalia

• Also called vulva or pudendum

• Mons pubis: Overlies pubic symphysis

• Labia majora: Homologue of male scrotum

• Labia minora: Encloses vestibule; contains external urethral and vaginal orifices

• Prepuce: Hood of clitoris

Clitoris

• Erectile tissue homologous to penis

• Consists of glans, body, and corpora cavernosa

• Crura (crus) are erectile structures

Oogenesis

Process

• Oogenesis: Generation of eggs (oocytes)

• Fetal stage: oogonia give rise to lifelong supply of oocytes

• At birth: primary oocytes and primordial follicles present

• Before puberty: developing follicles undergo atresia (degeneration)

• Menstrual cycle includes ovarian and uterine cycles

Menstrual, Ovarian, and Uterine Cycles

• Menstrual cycle: Hormonal cycling in ovaries and uterus

• Ovarian cycle: Follicular phase (follicle development) and luteal phase (corpus luteum formation)

• Uterine cycle: Prepares uterine wall for implantation; includes menstrual, proliferative, and secretory phases

The Ovarian Cycle

Follicular Phase

• FSH signals primordial follicles to develop into primary follicles

• Primary follicles contain primary oocytes (halted at Meiosis I)

• Secondary follicles: follicular cells become granulosa cells

• Zona pellucida: Glycoprotein coat around oocyte

• Follicular theca: Outer connective tissue layer, secretes androgens (stimulated by LH)

• Granulosa cells convert androgens to estrogens (stimulated by FSH)

• Estrogens stimulate growth of female sex organs

Antrum Formation and Maturation

• Antrum: cavity within follicle filled with fluid

• Meiosis I completes; Meiosis II begins, then halts—oocyte is now a secondary oocyte

• Vesicular (antral) follicle contains secondary oocyte and antrum

• Graafian (mature) follicle: antrum expands, corona radiata forms

Ovulation

• Occurs about halfway through ovarian cycle (day 14)

• Sudden increase in LH triggers ovulation

• One mature oocyte exits ovary, enters peritoneal cavity, swept into uterine tube by fimbriae

Luteal Phase

• After ovulation, remaining follicle becomes corpus luteum (temporary endocrine structure)

• Corpus luteum secretes progesterone to prepare uterus for implantation

• If no implantation, corpus luteum degenerates into corpus albicans (scar tissue)

The Uterine Cycle

Phases of the Endometrium

• Menstrual phase (days 1–5): Functional layer is shed

• Proliferative phase (days 6–14): Functional layer rebuilds

• Secretory phase (days 15–28): Endometrium prepares for implantation

The Mammary Glands

Structure and Function

• Modified sweat glands present in both sexes, functional in females

• Glandular structure undeveloped in nonpregnant women

• Milk production begins at or after childbirth

• Consist of lobes, lobules, lactiferous ducts, and lactiferous sinuses

Male Reproductive System

Main Structures

• Testes: Located within scrotum

• Epididymis: Comma-shaped structure on posterior testis

• Ductus deferens: Located within spermatic cord

• Urethra: Passage for urine and semen

• Glands: Seminal glands, prostate, bulbo-urethral glands

Male Perineum

Boundaries and Contents

• Diamond-shaped area between:

  • Pubic symphysis (anterior)

  • Coccyx (posterior)

  • Ischial tuberosities (lateral)

• Contains scrotum, root of penis, and anus

The Scrotum

Structure and Function

• Skin and superficial fascia surrounding testes

• Maintains temperature 3°C cooler than body temperature for optimal sperm production

• Dartos muscle: Smooth muscle responsible for wrinkling scrotal skin to reduce heat loss

• Cremaster muscle: Skeletal muscle bands that elevate testes

The Testes

Gross Anatomy

• Enclosed in serous sac (tunica vaginalis)

• Tunica albuginea: White, fibrous capsule dividing testis into 250–300 lobules

• Lobules contain 1–4 coiled seminiferous tubules

Microscopic Anatomy

• Seminiferous tubules: Separated by areolar connective tissue

• Spermatogenic cells: Sperm-forming cells

• Columnar sustentocytes (Sertoli cells): Support cells

Spermatogenesis

Process

• Spermatogenic cells: Produce sperm; 400 million sperm formed per day

• Spermatogonia: Stem cells

• Cells differentiate and move toward lumen:

  • Primary spermatocytes

  • Secondary spermatocytes

  • Spermatids

  • Sperm (head, midpiece, tail)

Regulation and Support

• Controlled by:

  • Follicle-stimulating hormone (FSH)

  • Testosterone (from interstitial cells, regulated by LH)

• Sustentocytes:

  • Surround and nourish spermatogenic cells

  • Move cells toward lumen

  • Bound by tight junctions (blood-testis barrier)

  • Secrete androgen-binding protein to concentrate testosterone

The Epididymis

Structure and Function

• Comma-shaped structure on posterior testis

• Rete testis: Network of tubules connecting seminiferous tubules to epididymis

• Consists of head, body, and tail

• Duct of epididymis (~6 m long uncoiled)

• 20-day maturation journey for sperm; gain ability to swim and fertilize egg

Microscopic Anatomy

• Dominated by pseudostratified columnar epithelium

• Bears tufts of stereocilia (immotile, long microvilli for reabsorption and secretion)

• "Docking stations" for maturing sperm

The Ductus (Vas) Deferens

Structure and Function

• Stores and transports sperm

• Inner mucosa: pseudostratified columnar epithelium

• Thick muscularis: inner and outer longitudinal layers separated by middle circular layer

• Adventitia: connective tissue

The Spermatic Cord

Contents

• Tube of fascia that includes:

  • Ductus deferens

  • Testicular artery

  • Pampiniform plexus

  • Nerves

  • Cremaster muscle

• Superior portion runs through inguinal canal; inferior portion in scrotum

Key Terms Table

Term	Definition
Oogenesis	Process of egg cell (oocyte) formation in females
Spermatogenesis	Process of sperm cell formation in males
Follicle	Multicellular sac in ovary housing oocyte
Corpus luteum	Temporary endocrine structure formed after ovulation
Fimbriae	Finger-like projections at end of uterine tube, help sweep oocyte
Seminiferous tubule	Site of sperm production in testis
Sustentocyte (Sertoli cell)	Support cell in seminiferous tubule, nourishes sperm cells
Menstrual cycle	Monthly cycle of changes in female reproductive organs

Important Hormones and Their Functions

Hormone	Source	Main Function
FSH (Follicle-Stimulating Hormone)	Pituitary gland	Stimulates follicle development in ovaries and spermatogenesis in testes
LH (Luteinizing Hormone)	Pituitary gland	Triggers ovulation and corpus luteum formation; stimulates testosterone production in males
Estrogen	Ovarian follicles	Promotes growth of female sex organs and endometrial lining
Progesterone	Corpus luteum	Prepares uterus for implantation
Testosterone	Testicular interstitial cells	Promotes development of male sex organs and spermatogenesis

Summary of Gametogenesis

Process	Location	Cell Types	Key Hormones
Oogenesis	Ovarian cortex	Oogonia, primary oocyte, secondary oocyte	FSH, LH, Estrogen, Progesterone
Spermatogenesis	Seminiferous tubules	Spermatogonia, primary spermatocyte, secondary spermatocyte, spermatid, sperm	FSH, LH, Testosterone

Additional info:

• All anatomical terms and processes described are foundational for understanding human reproduction and development.

• Tables above summarize key terms, hormones, and gametogenesis for rapid review.