Reproductive System - Male and Female

Male Reproductive System

• Organs:

  • Testicles (gonads): Produce sperm cells and testosterone.

  • Ducts: Transport sperm cells (Epididymis, Vas deferens, Ejaculatory duct, Urethra)

  • Accessory sex glands: Produce fluid for sperm cells (Prostate, Seminal vesicles, Bulbourethral glands)

  • Supporting structures: Protect the testes and assist in semen deposition (Penis, Scrotum).

Scrotum and Spermatic Cord

• Scrotum:

  • Sac of loose skin holding the testes.

  • Muscle layers:

    • Dartos muscle (outer): Smooth muscle, wrinkles the scrotum.

    • Cremaster muscle (inner): Skeletal muscle, pulls testes towards the trunk.

  • Functions:

    • Holds and protects the testes.

    • Keeps testes cooler than core body temperature.

• Spermatic cord:

  • Structure between the scrotum and pelvic cavity, passing through the inguinal canal.

  • Consists of: testicular artery, testicular veins (Pampiniform plexus), nerves, vas deferens, lymphatics, and cremaster muscle.

Testes

• Testes: Paired oval glands contained in the scrotum.

• Outer Layers:

  • Tunica albuginea: Innermost layer, creates partitions (septum) dividing the testis into lobules.

  • Tunica vaginalis (parietal and visceral layers):

• Internal Structure:

  • Seminiferous tubules: Sperm cell production.

  • Straight tubules

  • Rete testes

  • Efferent ducts

Seminiferous Tubules

• Cells within Seminiferous Tubules:

  • Spermatogenic Cells: Divide and differentiate to become sperm cells.

  • Nurse (Sertoli or Sustentacular) Cells:

    • Protect spermatogenic cells.

    • Form the blood-testis barrier via tight junctions.

• Cells between Seminiferous Tubules:

  • Interstitial Endocrine (Leydig) Cells: Produce testosterone (most prevalent androgen).

Other Ducts

• Epididymis:

  • Sperm maturation and storage.

  • Carries sperm from testis to vas deferens.

• Vas (Ductus) Deferens:

  • Stores sperm.

  • During sexual arousal, carries sperm from epididymis to ejaculatory duct.

• Ejaculatory Duct:

  • Carries sperm from vas deferens and seminal fluid from the seminal gland into the urethra.

• Urethra:

  • Three segments: prostatic, membranous, and spongy urethra.

  • Expels semen (sperm cells, seminal fluid, and prostatic fluid) and urine from the body.

Male Reproductive System Glands

• Seminal Vesicles (glands) (2):

  • Release an alkaline fluid containing fructose (for sperm nourishment) and coagulating proteins.

  • Contribute about 60% of the fluid volume of semen.

• Prostate:

  • Releases PSA (prostate-specific antigen), a proteolytic enzyme.

  • Fluid is slightly acidic.

• Bulbourethral Glands:

  • Release mucus for lubrication.

Semen

• Mixture of sperm cells and seminal fluid.

• Volume per ejaculation: 2.5 - 5 ml (50-150 million sperm/ml).

• Coagulates within 5 minutes and re-liquefies within 10-20 minutes.

• Sperm cells undergo capacitation in the vagina and uterus (allows for egg fertilization).

• Infertility is considered if there are less than 20 million sperm cells per ml of ejaculate.

Sperm

• Production: 300 million sperm cells/day.

• Parts: Head and tail.

• Head: contains DNA and the acrosome (a cap with powerful enzymes needed to fertilize the egg).

Penis

• Consists of erectile masses:

  • 2 corpora cavernosa.

  • 1 corpus spongiosum (contains the spongy urethra).

• Glans penis: Acorn-like distal end; covered by prepuce (foreskin) in uncircumcised men.

• Attachment to the body:

  • Bulb of the penis (corpus spongiosum extension).

  • Crura of the penis (corpora cavernosa extension).

Erection and Ejaculation

• Erection: Mechanoreceptors, erotic stimuli, hypothalamus, parasympathetic nervous system, penile arterioles dilate, penile veins are compressed

• Ejaculation

Hormonal Control of Testes

• Hypothalamus releases GnRH, which stimulates the anterior pituitary.

• Anterior pituitary releases LH and FSH.

• LH stimulates Interstitial endocrine cells to produce testosterone.

• FSH stimulates nurse cells to produce ABP, also stimulates spermatogenesis, along with testosterone.

• Inhibin decreases release of FSH.

• Testosterone decreases release of GnRH and LH.

• Functions of Testosterone

  • Male pattern of development before birth.

  • Enlargement of male sex organs and expression of male secondary sex characteristics starting at puberty.

  • Anabolism (protein synthesis).

Female Reproductive Organs

• Internal Organs: Ovaries, Uterine (Fallopian) tubes, Uterus, Vagina.

• External Genitals: Vulva (or pudendum).

• Mammary glands.

Ovaries

• Ovaries: Almond-shaped organs, homologous to the testes.

• Held in place by ligaments: ovarian ligament, mesovarium, and suspensory ligament.

• Functions:

  • Produce and release secondary oocytes within follicles.

  • Produce hormones: Estrogen, Progesterone, Inhibin, and Relaxin.

Ovary Regions

• Ovarian cortex: Holds eggs inside of follicles.

• Ovarian medulla.

• Follicles/eggs are in different stages of development.

Uterine (Fallopian) Tubes

• Between the uterus and the ovaries.

• Parts:

  • Isthmus: Narrow part.

  • Ampulla: Wide part; fertilization usually takes place here.

  • Infundibulum: Funnel-shaped with fimbriae (finger-like structures) connected to the ovary, which help the oocyte enter the tube.

Uterine Tube Histology

• Mucosa: Ciliated simple columnar epithelium and peg cells/lamina propria.

• Muscularis.

• Serosa.

Uterus

• Connects the vagina to the uterine tubes, shaped like an upside-down pear.

• Regions:

  • Fundus: Superior, dome-shaped portion.

  • Body: Central portion.

  • Isthmus: Constriction between the body and cervix.

  • Cervix: Inferior portion, opens into the vagina.

• Internal Divisions:

  • Uterine cavity.

  • Cervical canal.

Histology of Uterus Layers

• Perimetrium: Outermost layer.

• Myometrium: Middle layer, smooth muscle in three layers.

• Endometrium: Inner layer with two sublayers:

  • Basal layer: Always present, rebuilds the endometrial lining.

  • Functional layer: Sloughs off during menstruation.

Functions of the Uterus

• Source of menstrual flow.

• Passageway for sperm.

• Site of implantation of fertilized egg.

• Development of fetus during pregnancy.

• Labor.

• Cervix produces cervical mucus, which is thin around ovulation.

Vagina

• Fibromuscular canal that opens to the exterior, partially covered by the hymen.

• Attached to the cervix.

• Fornix: Space at the superior end of the vagina around the cervix.

• Functions:

  • Receptacle for penis.

  • Outlet for menstrual flow.

  • Passageway for childbirth.

Vulva

• Mons pubis: Anterior to pubic symphysis, adipose tissue covered with skin and coarse hair.

• Labia majora: Longitudinal folds of skin, covered with hair, homologous to the scrotum.

• Labia minora: Skin folds medial to majora, lack hairs.

• Clitoris: Homologous to the penis, erectile tissue at the anterior junction of labia minora.

• Vestibule: Space between labia minora, containing urethral and vaginal openings, and openings of glands (paraurethral and greater vestibular glands).

• Bulb of the vestibule: Longitudinal erectile tissue masses deep to the labia on either side of the vaginal orifice.

Breast

• Hemispheric projection anterior to the pectoralis major and serratus anterior muscles.

• Parts:

  • Nipple: Pigmented projection with openings for lactiferous ducts.

  • Areola: Circular pigmented area around the nipple, containing modified sebaceous glands.

  • Mammary gland: Modified sweat gland.

• Supported by suspensory ligaments of the breast

Mammary Glands Function

• Milk production: In response to prolactin.

• Milk ejection: In response to oxytocin. Myoepithelial cells around alveoli contract, causing milk ejection.

Female Cycle

• Ovarian cycle.

• Uterine cycle.

Ovarian Cycle

• Follicular phase: Days 0-13, ovarian follicles mature (primordial to mature) under FSH influence from the anterior pituitary gland.

• Ovulation: Day 14, release of secondary oocyte from a mature follicle under LH influence from the anterior pituitary gland.

• Luteal phase: Days 15-28, corpus luteum is formed under LH influence from the anterior pituitary gland.

Hormonal Control of the Ovaries

• The hypothalamus releases GnRH, which stimulates the anterior pituitary.

• Anterior pituitary releases FSH and LH.

• FSH promotes Follicular development (primordial follicles to mature follicles).

• LH promotes ovulation (egg release).

• Ovaries, Follicles make Estrogen.

Uterine Cycle

• Menstrual phase: Days 1-5, caused by a significant decrease in estrogen and progesterone production.

• Proliferative phase: Days 6-14, endometrium doubles in thickness under the influence of estrogen from the ovaries.

• Secretory phase: Days 15-28, endometrium blood supply and nutrient content increase significantly under the influence of progesterone from the ovaries.

Hormone concentration Change and affect on the Ovaries and growing follicles:

• GnRH stimulates release of FSH and LH

• FSH stimulates further development of ovarian follicles and their secretion of estrogens and inhibin

• LH stimulates Ovulation. Growing follicle -> Corpus Luteum -> Secretion of progesterone, estrogens, relaxin and inhibin by corpus luteum

• Estrogens. * Promote development and maintenance of female reproductive structures, feminine secondary sex characteristics, and breasts * Increase protein anabolism * Lower blood cholesterol Moderate levels inhibit release of GnRH, FSH, and LH

• Progesterone *Works with estrogens to prepare endometrium for implantation * Prepares mammary glands to secrete milk * Inhibits release of GnRH and LH

• Relaxin * Inhibits contractions of uterine smooth muscle, During labor, increases flexibility of pubic symphysis and dilates uterine cervix

• Inhibin *Inhibits release of FSH and, to a lesser extent, LH

Reproductive Cell Division

• Sperm and egg are made through meiosis.

• For Meiosis, DNA replication occurs once, and the cells divide twice (Meiosis I and Meiosis II).

• The end result of meiosis is 4 cells with 23 chromosomes each.

Spermatogenesis

• Making of sperm cells, takes 65 to 75 days to complete.

Oogenesis

• Oogonium divides through mitosis to become Primary oocyte.

• Primary oocyte goes through meiosis I and becomes Secondary oocyte.

• Secondary oocyte goes through meiosis II and becomes an Ovum.

Birth Control Method Failure Rates

• Complete abstinence: 0%

• Surgical sterilization: 0%

• Hormonal methods: 0.1- 2%

• Emergency contraception: 25%

• Intrauterine devices: 0.6-0.8%

• Spermicides (alone): 15%

• Barrier methods: 2-15%

• Periodic abstinence: 2-6%

• No method: 85%