Reproductive System

REPRODUCTIVE SYSTEM

OVERVIEW PRIMARY SEX ORGANS

• Definition: Organs that produce gametes (sperm and eggs).
    - Female: Ovary
    - Male: Testes
• Functions:
    - Male reproductive system’s primary responsibility is to produce sperm cells and deliver them to the female reproductive system.
    - Female reproductive system is responsible for producing the oocyte and sustaining and maintaining a viable embryo.

SECONDARY SEX ORGANS

• Definition: Necessary for reproduction but not for the production of gametes.
    - Female: Vagina, uterus, and uterine tubes.
    - Male: Penis, ducts, and glands.

SECONDARY SEX CHARACTERISTICS

• Definition: Not essential for reproduction; serve to attract the opposite sex.
    - Examples include breasts, pubic hair, and muscle mass.
• Development: Arises during puberty due to increased secretion of sex hormones.

REPRODUCTIVE SYSTEMS AND GENETICS

• Terms:
    - Genotype: Chromosomal makeup; XX = female, XY = male.
    - Phenotype: Appearance of physical and sexual characteristics.
• Gonadal Differentiation:
    - Begins developing at the 5-6th week of embryogenesis.
    - At the 7th week, bipotential gonads develop:
      - a. Testes differentiate under the influence of the Y chromosome.
      - b. Ovaries differentiate in the absence of the Y chromosome (XX).

DUCT SYSTEM DIFFERENTIATION - MALE

• Duct Type: Male = Wolffian duct.
    - Functions:
      - Androgen stimulates the Wolffian duct into:
        1. Epididymis
        2. Vas deferens
        3. Seminal vesicles
• Genetic Influence:
    - The Y chromosome synthesizes TDF (testes determining factor) leading to testes formation and MIF (Mullerian inhibiting factor) which suppresses the development of female structures.
      - The testes also secrete DHT (dihydrotestosterone) promoting masculinization of external genitalia.
    - In the presence of MIF, the Mullerian duct regresses.

DUCT SYSTEM DIFFERENTIATION - FEMALE

• Duct Type: Female = Mullerian duct.
    - There is an intrinsic tendency to feminize in the absence of the Y chromosome, testes, or MIF.
    - The Mullerian duct differentiates into:
      - Uterus
      - Fallopian tubes
      - Upper ½ of the vagina
• In the absence of testosterone, the Wolffian duct regresses.
• Normal Development Factors:
    - Four factors must be present for normal development:
      1. Elongation
      2. Fusion
      3. Canalization
      4. Septum absorption
• Consequences of Failure:
    - May result in amenorrhea, repeated spontaneous abortion, or failure for implantation.

EXTERNAL GENITALIA

• Development Dependency: Male and female genitalia development is dependent on hormones. Hypo- or hypersecretion of sex hormones can result in immature or over-mature sexual characteristics.
• At approximately the 8th week, the bipotential state forms:
    - Urogenital sinus
    - Two labioscrotal folds
    - Genital tubercle.

HORMONAL INFLUENCE - MALE

• Hormones: Male = testosterone converted to DHT.
    - Genital tubercle develops into the penis; labioscrotal folds → scrotum; urogenital sinus → urethra.
    - Genotype: If there’s a decrease in androgen (either insufficient synthesis or non-responsive receptors), the male may have an XY genotype but exhibit a female phenotype.
    - Summary:
      - Need testosterone for Wolffian duct differentiation and maturation.
      - Need DHT for external genitalia development.

HORMONAL INFLUENCE - FEMALE

• Hormones: Female = Estradiol.
    - In the absence of testosterone, receptor defect or presence of ovaries leads to:
      - Genital tubercle → clitoris.
      - Labioscrotal folds → labia majora.
      - Urogenital sinus → labia minora, urethra, and lower ½ of the vagina.
• Increased Androgen: An increase in androgen in a developing female can lead to male external genitalia.

FEMALE REPRODUCTIVE SYSTEM ANATOMY

EXTERNAL GENITALIA

• Internal Genitalia: Ovaries, uterine tubes, uterus, and vagina.
• External Genitalia (Vulva): Includes mons pubis, labia, clitoris, and vestibular structures.
    - Mons Pubis: Fatty rounded area overlying the pubic symphysis.
    - Labia Majora: Long skin folds enclosing labia minora.
    - Labia Minora: Smaller folds of skin enclosing the vestibule containing the external urethral and vaginal orifices.

EXTERNAL GENITALIA (continued)

• Greater Vestibular Glands: Lateral to the vaginal opening, release mucus for lubrication during intercourse.
• Clitoris: Anterior to the vestibule, composed of erectile tissue, covered by prepuce.
• Female Perineum: Diamond-shaped area bounded by the ischial tuberosities, coccyx, and pubic arch, containing the anus and vulva.

INTERNAL GENITALIA - OVARIES

• Location: Flank the uterus on each side, held in place by several ligaments:
    - Ovarian ligament: Anchors the ovary medially to the uterus.
    - Suspensory ligament: Anchors laterally to the pelvic wall.
    - Mesovarium: Anchors the ovary to the uterus and abdominal wall, part of the broad ligament.
• Broad Ligament: A fold of peritoneum that supports the uterus, uterine tubes, vagina, and ovaries.

INTERNAL GENITALIA - OVARIES (continued)

• Blood Supply: Primarily served by ovarian arteries and veins.
• Tunica Albuginea: Fibrous capsule surrounding each ovary, covered by germinal epithelium (simple cuboidal).
• Gonadal Structure:     - Ovarian Cortex: Contains ovarian follicles housing developing gametes.
    - Ovarian Medulla: Contains blood vessels and nerves.

INTERNAL GENITALIA - OVARIAN FOLLICLES

• Structure: Each follicle comprises a developing egg (oocyte) surrounded by supportive cells.
• Supporting Cells:
    - Follicle cells: Single layer surrounding an oocyte.
    - Granulosa cells: Multiple layers surrounding an oocyte.
• Stages of Follicular Development:
    1. Primordial follicle: Single layer of squamous follicle cells.
    2. Primary follicle: One or more layers of cuboidal follicle cells.
    3. Secondary follicle: Similar to primary but with fluid-filled spaces.
    4. Graafian follicle: Contains a dominant fluid-filled cavity called antrum; will be ovulated.
• Post-Ovulation: Remaining granulosa cells transform into corpus luteum (endocrine structure).

INTERNAL GENITALIA - UTERINE TUBES/OVIDUCT/FALLOPIAN TUBES

• Function: Receive the ovulated oocyte and transport it to the uterus.
    - Length: Approximately 4 inches long.
    - Structure: 5 regions:
      - Fimbriae: Ciliated extensions draping over the ovary.
      - Infundibulum: Funnel-shaped structure from which fimbriae extend.
      - Ampulla: Curved portion around the ovary.
      - Isthmus: Constricted region joining the uterus.
      - Intramural: Located within the walls of the uterus.
• Mechanism: The cilia on fimbriae create a current drawing the ovum into the infundibulum.
• Composition: Contains smooth muscle and ciliated epithelium aiding transfer of oocyte to the uterus.

INTERNAL GENITALIA - UTERUS

• Definition: Hollow, thick-walled organ; receives, retains, and nourishes fertilized ovum.
• Location: Anterior to the rectum, posterior-superior to the bladder; continuous with the vagina.
• Positioning: Typically anteverted in most women, may become retroverted in older age.
• Regions of Uterus:
    - Body: Major midportion.
    - Fundus: Rounded portion superior to uterine tubes.
    - Cervix: Neck projecting into the vagina.
• Cervical Canal: Communicates with the uterine cavity (internal os) and vaginal cavity (external os).
• Cervical Mucosa: Contains mucus-secreting glands essential for timing of fertilization and preventing bacterial access.
• Support: Laterally supported by the broad ligament and other ligaments; pelvic floor muscles also aid in support.

INTERNAL GENITALIA - UTERUS (continued)

• Wall Composition: 3 layers:
    1. Perimetrium: Outermost layer (serous layer); visceral peritoneum.
    2. Myometrium: Middle layer consisting of smooth muscle (thickest layer).
    3. Endometrium: Inner layer of simple columnar epithelium supported by a thick lamina propria.
• Endometrial Layers:
    1. Stratum Functionalis: Superficial layer that undergoes cyclic changes and is shed during menstruation, contains most uterine glands.
    2. Stratum Basalis: Thinner deeper layer unresponsive to ovarian hormones; forms new stratum functionalis post-menstruation; contains stem cells.

INTERNAL GENITALIA - VAGINA

• Definition: Thin-walled tube lying between the bladder and rectum extending from the cervix to the exterior.
• Functions: Receives penis and semen during intercourse, provides delivery route for an infant and menstrual flow.
• Wall Structuring: Consists of mucosa, muscularis, and adventitia.
• Mucosa: Lined by stratified squamous non-keratinized epithelium, contains rugae, no glands; lubrication is via cervical mucous glands.
• External Vaginal Orifice: Opening of the vagina; opening between vaginal canal and cervical canal is the external os.
• Hymen: May partially cover external vaginal orifice in virgins; a partition.
• Vaginal Fornix: Recess around the cervix neck; includes lateral, posterior, and anterior portions.
• Accessory Glands: Open into the vestibule, aiding in maintaining vaginal moisture during intercourse.

FUNCTIONS OF THE FEMALE REPRODUCTIVE STRUCTURES

• Ovary: Produces oocytes and female sex hormones (estrogens, progesterone, inhibin).
• Uterine Tube: Moves oocyte or fertilized ovum toward the uterus; site of fertilization and early development stages.
• Vagina: Receives sperm during intercourse; passageway for menstrual flow and infant delivery.
    - Labia Majora and Labia Minora: Enclose and protect external reproductive structures.
    - Clitoris: Contains erectile tissue, innervated with sensory nerve endings.
    - Greater Vestibular Gland: Offers lubrication for the vaginal opening.

MALE REPRODUCTIVE SYSTEM ANATOMY

EXTERNAL GENITALIA - MALE

• Scrotum: Sac of skin and fascia, hangs outside the abdominopelvic cavity at the root of the penis, maintaining optimal temperature for sperm production.
• Testes: Paired male gonads suspended within the scrotum, providing a temperature 3°C lower than the body temperature for enhanced sperm production.
    - Cremaster Muscle: Elevates or lowers the testes based on temperature changes, maintaining optimal conditions for sperm production.

EXTERNAL GENITALIA (continued)

• Penis: Functions to deliver sperm into the female reproductive tract; consists of rooted base and free shaft ending in the glans penis.
    - Prepuce or Foreskin: Loose skin cuff around the glans penis, typically removed during circumcision.
    - Internal Structure: Contains urethra and three cylindrical erectile bodies.
      - Corpus Spongiosum: Midventral erectile body surrounding the urethra, expands to form glans penis.
      - Corpora Cavernosa: Two dorsal erectile bodies.

INTERNAL ANATOMY - TESTES

• Structure: Egg-shaped, surrounded by tunics:
    - Tunica Vaginalis: Derived from the parietal peritoneum.
    - Tunica Albuginea: Fibrous capsule encasing the testis, extending into lobules.
• Function:
    - Sperm Production: Each lobule contains 1-4 coiled seminiferous tubules (site of sperm synthesis).
    - Endocrine Function: Produces testosterone via interstitial Leydig cells.

INTERNAL ANATOMY - TESTES (continued)

• Sustentacular Cells (Sertoli Cells):
    - Maintain blood-testis barrier, support mitosis, meiosis, and spermiogenesis.
    - Secrete inhibin, androgen-binding protein, and Müllerian-inhibiting factor.
• Blood Supply: Testicular arteries provide oxygen-rich blood; surrounded by the pampiniform plexus for temperature regulation.
• Spermatic Cord: Connective tissue sheath for nerves and vessels to and from the testes.

INTERNAL ANATOMY - EPIDIDYMIDES

• Location: On top, side, and rear of each testis.
• Sperm Maturation: Sperm enter and remain within the epididymis for approximately 3 weeks to mature and acquire motility.
• Ejaculation Mechanism: Smooth muscle contractions during ejaculation propel sperm into the ductus deferens.

INTERNAL ANATOMY – DUCTUS DEFERENS AND EJACULATORY DUCTS

• Ductus Deferens: Runs upward from each epididymis as part of the spermatic cord, enters the pelvic cavity via the inguinal canal, and unites with the seminal vesicle duct, forming the ejaculatory ducts.
• Function during Ejaculation: Smooth muscle peristalsis pushes sperm through ductus deferens into the ejaculatory duct.
• Vasectomy: Surgical procedure involving cutting and tying each ductus deferens.

INTERNAL ANATOMY – URETHRA

• Function: Conveys urine and semen; divided into:
    - Prostatic Urethra: Within the prostate gland.
    - Membranous Urethra: Within the urogenital diaphragm.
    - Penile or Spongy Urethra: Within the corpus spongiosum; opens to the exterior at the external urethral orifice.

FUNCTIONS OF MALE REPRODUCTIVE STRUCTURES

• Testis: Produces sperm cells, testosterone, and inhibin.
• Duct System:
    - Epididymis stores and matures sperm; ductus deferens transports sperm to the ejaculatory duct; urethra expels semen from the body.
• Glands:
    - Seminal vesicle, prostate gland, and bulbourethral gland secrete fluid that aids sperm vitality and motility.
• Externally: Scrotum protects and regulates temperature of testes; the penis delivers sperm into the female reproductive tract.

ACCESSORY ORGANS

1. Seminal Vesicles: Paired glands contributing 60% of semen volume, secreting viscous alkaline fluid containing fructose, prostaglandins, and a coagulating enzyme.
2. Prostate Gland: Secretes fluid contributing 30% of semen volume, containing citrate and prostate-specific antigen (PSA), enters the prostatic urethra during ejaculation.
3. Bulbourethral Glands (Cowper’s glands): Located inferior to the prostate, produces alkaline mucus pre-ejaculation to neutralize traces of acidic urine.

MALE REPRODUCTIVE PHYSIOLOGY

FUNCTIONS OF MALE REPRODUCTIVE SYSTEM

• Gametogenesis: Produces male gametes (sperm).
• Hormonal Synthesis: Produces androgens (male sex hormones like testosterone).
• Delivery: Facilitates delivery of sperm into the female reproductive tract.

OVERVIEW OF MITOSIS AND MEIOSIS

• Diploid Cells: All body cells except sex cells have 2 copies of each chromosome (46 in total).
• Haploid Cells: Sperm and eggs have only one copy of each chromosome (23 single chromosomes).
• Fertilization: Combines sperm and egg to form a diploid zygote.
• Mitosis: Process of diploid cells creating more diploid cells.
• Meiosis: Diploid germ cells converting into haploid sperm and eggs.

MEIOSIS

• Phases:
    - Meiosis I: Homologous chromosomes pair up and separate.
    - Meiosis II: Sister chromatids separate, resulting in four genetically unique haploid daughter cells.
• Process Overview:
    - During meiosis, tetrad formation and crossing over occurs during prophase I.
    - Independent assortment occurs during metaphase I.
    - Cytokinesis results in haploid cells.

SPERMATOGENESIS

• Definition: Sperm formation within seminiferous tubules through meiosis and spermiogenesis.
• Phases:
    - Meiosis: 1 diploid cell produces 4 haploid spermatids.
    - Spermiogenesis: Transformation of spermatids into mature spermatozoa.
• Types of spermatogonia:
    - Type A: Remain as stem cells.
    - Type B: Undergo meiosis to form sperm.

SPERM STRUCTURE

• Regions:
    - Head: Contains nucleus and acrosome with digestive enzymes.
    - Midpiece: Contains mitochondria for ATP production.
    - Flagellum: Long tail aiding in motility.

SEMEN (SEMINAL FLUID)

• Definition: Fluid expelled during orgasm; transport medium for sperm, comprises secretions from epididymis, seminal vesicle, prostate, and bulbourethral gland (10% sperm, 60% seminal fluid, 30% prostatic fluid).

ERECTILE PHYSIOLOGY

• Mechanism: Increases in parasympathetic signals lead to nitric oxide production, resulting in:
    - Dilation of penile arterioles (increased blood flow).
    - Compression of veins draining the penis (yielding an erection).
    - Allows the penis to penetrate the female reproductive tract.

EJACULATORY PHYSIOLOGY

• Ejaculation Mechanism:
    - Increased sympathetic nerve activity leads to:
      - Contraction of reproductive ducts and glands.
      - Contraction of internal urethral sphincter (preventing urinary reflux).
      - Semen expulsion through the urethra, characterized by muscular, cardiovascular response (e.g. increased HR, BP).

MALE SEXUAL RESPONSE - ERECTION

• Involves engorgement of erectile tissues due to increased blood flow during sexual arousal.

MALE SEXUAL RESPONSE - EJACULATION

• Involves emission of semen under sympathetic control, characterized by muscular contractions, followed by relaxation and refractory period.

HORMONAL CONTROL OF MALE REPRODUCTIVE FUNCTION – THE BRAIN-TESTICULAR AXIS

• Regulation of Spermatogenesis:
    - Hypothalamus releases GnRH, stimulating anterior pituitary to release FSH and LH.
    - LH stimulates testosterone release; FSH promotes secretion of androgen-binding protein for spermatogenesis.
    - Feedback mechanisms inhibit GnRH, FSH, and LH when testosterone levels are high.

TESTOSTERONE

• Functions: Responsible for male sexual characteristics and development of non-reproductive organs.
• Secondary Sexual Characteristics Include:
    1. Increased body hair in specific areas.
    2. Deepening voice due to laryngeal hypertrophy.
    3. Increased skin thickness and muscle mass.
    4. Increases in metabolic rate and bone growth.

MAJOR REPRODUCTIVE HORMONES IN MALES AND FEMALES

• In Males:
    - GnRH, FSH, LH: Regulate testosterone production and spermatogenesis.
    - Testosterone: Development of male reproductive structures and secondary characteristics.
• In Females:
    - GnRH, FSH, LH: Regulate estrogen and progesterone production and female reproductive processes.