The reproductive system
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The Reproductive System. Functions of the Reproductive System. Survival of the species NOT survival of the individual Unique aspects of reproduction: Not fully functional until after puberty All other body systems are functional at birth Functional stem cells act to produce gametes

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The Reproductive System

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The Reproductive System

Functions of the Reproductive System

  • Survival of the species

    • NOT survival of the individual

  • Unique aspects of reproduction:

    • Not fully functional until after puberty

      • All other body systems are functional at birth

    • Functional stem cells act to produce gametes

      • Spermatozoa in males

      • Ova/oocytes in females

      • Both are haploid (half the number of chromosomes as a normal cell)

Chromosome Number & Meiosis

  • Every other cell (other than the gametes in the reproductives, RBC’s and platelets) has 23 pairs of chromosomes (total of 46)

    • Cells normally divide by mitosis

      • Duplicate the DNA (create a total of 46 X 2 chromosomes), and then equally divide between 2 cells

      • Remember that this is usually carried out by a stem cell…not every cell in your body can divide or undergo mitosis


    • Instead of equally dividing 46 chromosomes, gamete cells divide to produce “haploid” offspring

      • 26 chromosomes TOTAL

Karyotype = this picture

Chromosomes isolated during metaphase

Note: each one of these has an exact copy that is on the other side of the cell, but THIS picture shows the “homologous pairs”

Each chromosome you see in the karyotype is only at HALF of this chromatid


Meiosis actually occurs in 2 stages: meiosis I and Meiosis II.

Meiosis I is essentially mitosis (the two daughter cells have 26 PAIRS of chromosomes) since the division involved DNA replication prior to division.

Meiosis II is the classic “meiosis” since the daughter cells further divide their DNA without replicating it.

Chromosome Number & Meiosis

  • The meiosis process is carried out at different times in either the male or female:

    • Males undergo meiosis constantly following puberty

      • Spermatozoa are constantly being produced/renewed

    • Females do not complete meiosis until fertilization

      • Actually, the ova stops at Metaphase II (in the process of dividing up the 26 pairs into 26 INDIVIDUAL chromosomes)

Homologous Sex Organs

  • During embryonic development, the male & female sex organs are initially the SAME

    • Easy way to think about this concept:

      • Males = sex organ progenitors descend out of the pelvic cavity

      • Female = sex organ progenitors remain within the pelvic cavity

Descension of the sex organs

External homologous structures

Male Reproductive Organs

  • Primary sex organs:

    • Testes (testicles)

      • Produce the “gametes” or spermatozoa

      • Also produce androgen/sex hormones involved in secondary sex organ development

        • Physique, body hair, voice pitch etc.

  • Secondary sex organs:

    • Sperm transport ducts: epididymides, ductus/vas deferentia, ejaculatory ducts, & urethra

    • Accessory glands: seminal vesicles, prostate gland & bulbourethral glands

    • Copulatory organ: penis

    • Scrotum


  • Testes are suspended in the scrotum

    • Spermatozoa development requires slightly lower temperature (35ºC)

      • Scrotum contains 2 separate muscle groups:

        • Dartos muscle = smooth muscle below epithelial layer

          • Contracts when testicles are too cold

        • Cremaster muscle = skeletal muscle

    • Testes are also separated from one another by scrotal septum

      • Externally visible as the perineal raphe

Spermatozoa development follows a pathway from the seminiferous tubule – rete testes - epididymis. If not ejaculated, the spermatozoa will remain in the epididymis and be digested (8-10 weeks). If sexually active, spermatozoa will finally mature in the epididymis.

Testes and ducts

  • Epididymis: where spermatozoa undergo final maturation

  • Ductus deferens (Vas deferens): tube between epididymis & ejaculatory duct

    • “Spermatic cord” encases the ductus deferens as well as testicular artery & vein

    • Penetrates into the pelvic cavity via “inguinal canal”

      • Common site for hernia

  • Spermatic cord: Vas deferens + nerve + blood and lymphatic vessels + cremaster

    • Ejaculatory duct: connection between ductus deferens & seminal vesicle

    • Seminal vesicles: secrete fructose-rich fluid to aid in spermatozoa viability

      • 60% ejaculatory volume

      • Heavily innervated by the sympathetic nervous system

    • Prostate gland: glandular tissue encased by smooth muscle

      • Secretes alkaline buffer to neutralize vaginal acids (enhance spermatozoa viability)

      • 40% ejaculation volume

      • Heavily innervated by the sympathetic nervous system

    • Bulbourethral glands (Cowper’s glands): superficial to the pelvic diaphragm

      • Secrete mucus-rich solution to neutralize urethra & lubricate penis prior to coitus

    Pay attention to paired vs. unpaired glands that lie along the spermatozoa ejaculatory pathway.

    The prostate gland enlarges with age. It is a normal process. Prostate cancer is the second leading cause of death in males. Patient morbidity is not necessarily from the prostate cancer, but the metastasis of the carcinoma that usually enters the spinal cord & brain.


    • Copulatory organ

      • Proximal region = root

      • Middle shaft = body

      • Distal region = glans penis

    • Body = three large tubes of tissue

      • Corpora cavernosapenis: paired dorsal tubes with large arterial bloodflow

        • Normally “gated” by the sympathetic nervous system

      • Corpus spongiosumpenis: single tube that encases the spongy urethra

    • Glans penis = expanded distal end of the corpora spongiosum penis

      • Prepuce is very loosely attached to corpora spongiosum penis


    • Circumcision of foreskin/prepuce in effort to prevent infection (makes glans penis easier to clean)

      • Secretes “smegma” that can collect under the prepuce and initiate infection

    The “dorsal artery/vein” is in reference to “dorsal” on a 4-legged animal rather than the patient being “erect” in anatomical position.

    During erection, the parasympathetic nervous system “opens” the gates of the deep arteries within the corpora spongiosum penis in order to allow blood to enter the capillary bed.

    Female Reproductive Organs

    • Primary sex organ = ovary/ovaries

      • Gametes (follicles) are not produce, they were formed during fetal development

      • Secrete androgen hormones (estrogen) for secondary sex organ development & sex organ maturation

    • Secondary sex organs

      • Required for fertilization

        • Vagina, uterine/fallopian tubes, uterus&mammary glands


    • Similar to testicles: endocrine gland along with gamete storage

      • Pre-puberty = smooth & pinkish

      • Post-puberty = grey & wrinkled (ovulation scars the ovaries)

  • Located in “ovarian fossa” of the pelvis

    • Secured in place by 4 membranes:

      • Broad ligament = parietal peritoneum supporting uterine tubes & uterus

      • Mesovarium = region of the broad ligament supporting ovaries

      • Ovarian ligament = anchors uterus & ovaries

      • Suspensory ligament = extension of the broad ligament anchored to pelvic wall

        • Where you find ovarian artery & vein

  • Ovaries

    • The cortex contains many oocytes in various stages of development

    • The medulla is a connective tissue rich in blood vessels

    • The ovaries are covered by the tunica albuginea and the germinal epithelium

    • The ovaries are not attached to the Fallopian tubes

    Fallopian tubes

    • Tubes originating at the uterus and ending near the ovaries

    • At the ovarian end, the fimbraemust catch ova & direct into the tubular apparatus

      • Fimbrae located distal to the uterus, in “infundibulum” region of the uterine tube apparatus

    • Uterine tube structure:

      • Inner mucosa

      • Middle muscularis (circular & longitudinal muscle same as intestinal tract)

      • Outer serosa = visceral peritoneum

    • Ova takes 4-5 days to travel the uterine tube…this is when you fertilize the ova


    • Fundus= region where uterine tubes enter

    • Body= main region

    • Cervix= entrance to vagina (similar in shape to ileocecal valve)

      • Uterine cavity has distinct regions

        • Cervical canal= tube in cervix region

        • Isthmus(“internalos”)of uterus= line between cervical canal & uterine cavity

        • Uterine osteum(“os”)= Outermost portion of cervical canal


    • Wall = 3 functional layers (metria):

      • Perimetrium= visceral peritoneum

      • Myometrium= 3 layers of smooth muscle (like the stomach)

      • Endometrium= stratum functionale (menses) & stratum basale

    Female Reproductive Organs: Vagina

    • Female copulation organ

    • 3 layers of tissue:

      • Mucosal layer = non-keratinized stratified squamous

        • Folded into rugae (vaginal rugae…similar to urinary bladder rugae & gastric rugae…allows distension)

        • Acidic (pH 4.0) to inhibit colonization

      • Muscularis layer = similar to intestinal tract (circular & longitudinal layers)

      • Fibrous layer = anchors vagina to pelvis

    Female Reproductive Organs

    • External genitilia = vulva

    Notes: the labia majora have hair & sebaceous glands & are homologous to the male scrotum. The labia minora are hairless & have sebaceous glands.

    Female genital mutilation (FGM)

    Masculinization due to male hormone exposure

    Pregnant man (due to incomplete

    sex change)

    Mammary glands (secondary sex organs)

    • Modified sudoriferous glands (extension of the integumentary system)

    • From ribs 2-4 up into the axillary region

      • Axillary interface is clinically relevant since most cases of breast cancer center around the lymphatic drainage of the breast in the axillary region

    • Each gland = 15-20 lobes

      • Each lobe contains 1 duct (15-20 ducts) & separated by adipose tissue

      • Each lobe comprised of mammary alveoli (like pulmonary alveoli…sphere shaped)

  • Note the flow of breast milk: mammary duct – lactiferous ducts – lactiferous sinus – nipple. Milk is stored in the lactiferous sinus prior to being mobilized to the nipple. Areola = glandular tissue that secretes oily secretions to lubricate nipple.

  • Twins

    • Fraternal twins = non-identical

      • more than 1 ova will ovulate

      • More than 1 ova fertilized simultaneously = fraternal twins

    • Monozygotic twins = genetically identical

      • 1 fertilized ova develops into 2 separate embryos

        • Conjoined twins = split into 2 embryos, share the same placental sac

    • Semi-identical twins = when secondary oocyte is not divided into a “cell” & polar body, but divides equally

      • Fertilize both = one set of maternal DNA, two sets of paternal DNA

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