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Reproductive System. Chapter 27. Male Reproductive System. Anatomy Scrotum Testes Penis Duct system Accessory glands & semen . Scrotum. Maintains testicular temperature at ~ 3 o C lower than core temperature Surface area varies in response to external temperature. Figure 27.2.

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Male reproductive system l.jpg
Male Reproductive System

  • Anatomy

    • Scrotum

    • Testes

    • Penis

    • Duct system

    • Accessory glands & semen


Scrotum l.jpg
Scrotum

  • Maintains testicular temperature at ~ 3oC lower than core temperature

  • Surface area varies in response to external temperature

Figure 27.2


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Testes

  • Primary reproductive organ of the male:

    • Produces sperm & testosterone

    • Testicular lobules contain coiled seminiferous tubules.

    • Seminiferous tubules: the location of sperm production

    • Interstitial cells in the connective tissue around the seminiferous tubules produce testosterone

Figure 27.3a


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Penis

  • Designed to deliver sperm into the female reproductive tract

    • Penile root

    • Penile shaft

    • Glans penis

Figure 27.4


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Penis

  • Corpus spongiosum

    • midline & ventral surrounds urethra; proximally forms the bulb of the penis; distally forms glans penis

  • Corpora cavernosa

    • paired dorsal erectile bodies that terminate proximally in the crura (crus) of the penis that are anchored to the pubic arch


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Duct system: male

  • Epididymus

  • Vas deferens

  • Urethra; (three regions)

    • Prostatic urethra

    • Membranous urethra

    • Penile urethra


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Duct system: male

  • Epididymus: receives immature sperm from the rete testis; as the sperm move through the epididymus (~20 days) they become fully motile

Figure 27.3a


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Duct system: Male

  • Ductus (vas) deferens: from the epididymus merges with the

    • Seminal vesicle duct to form the

    • Ejaculatory duct which enters the

    • Prostate & empties into the urethra

Figure 27.3a


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Duct system: male

  • Urethra: serves both urinary & reproductive systems

  • Three regions

    • Prostatic urethra

    • Membranous urethra

    • Penile urethra

Figure 27.1


Accessory glands seminal vesicles l.jpg
Accessory glands – Seminal Vesicles

  • on posterior bladder wall:

  • make alkaline, seminal fluid containing: fructose, ascorbic acid, vesiculase (coagulating enzyme) & prostaglandins:

  • Seminal fluid: 2/3 of volume of semen

Figure 27.1


Accessory glands prostate gland l.jpg
Accessory glands - Prostate gland

  • Surrounds urethra

  • Produces a milky, slightly acidic fluid

    • citrate, multiple enzymes & PSA (prostate specific antigen):

  • Prostatic fluid: ~1/3 of semen volume

Figure 27.1


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Accessory glands

  • Bulbourethral glands:

  • Produce a thick clear mucous that neutralizes acidic urine

Figure 27.1


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Semen

  • Semen:

  • Milky white mixture of sperm & accessory gland secretions

  • Provides:

    • Nutrients for sperm

    • Chemical protection / activation

    • Acts as a transport medium for sperm


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Male Sexual Response

  • Erection: enlargement & stiffening of the penis

  • Parasympathetic reflex

    • Triggers local release of Nitric Oxide causing

    • Arteriolar dilation & increased blood flow to erectile tissues

  • Expansion of erectile tissues interferes with veins that drain the system & maintains erection


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Male Sexual Response

  • Ejaculation: propulsion of semen through the duct system

  • SNS discharge causes

    • Contraction throughout the ductal system

    • Contraction of bladder sphincter &

    • Contraction of the bulbospongiosus muscles of the penis


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Male Sexual Response

  • Refractory period: After ejaculation there is a refractory period during which a male is unable to have another ejaculation (minutes  hours)


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Spermatogenesis

  • Cell differentiation events that produces male gametes (spermatozoa)


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Spermatogenesis

  • Diploid (2n):

    • having 2 of each chromosome type (n) human 2n=46

  • Haploid:

    • having 1 of each chromosome type human n = 23

  • body cells are diploid (2n)

  • Gametes are haploid (n)

  • When 2 gametes fuse at fertilzation, n + n = 2n

    • diploidy restored


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Comparison of Mitosis & Meiosis

  • Meiosis:

  • Two consecutive nuclear divisions producing

  • Four haploid daughter cells

Figure 27.6


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Meiotic Cell Division: Meiosis I

  • Meiosis:

  • Meiosis I: separates homologous chromosomes into different cells (i.e. diploid  haploid)

  • cells still retain 2 copies of each gene

Figure 27.7


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Meiotic Cell Division: Meiosis II

  • Meiosis:

  • Meiosis II: separates chromatids into separate cells

  • generates cells with only 1 copy of each gene

Figure 27.7


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Spermatogenesis

  • Occurs in the seminiferous tubules;

  • Spermatogonia form epithelial basal layer of cells

  • Spermatogonia (sperm stem cell)

    • Divide by mitosis until puberty forming a large population


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Spermatogenesis

  • At puberty mitotic divisions of spermatogonia form

  • Two daughter cells with different functions

    • Type A cells

    • Type B cells


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Spermatocytes to Spermatids

  • Type A: remains to maintain the spermatogonia stem cell

  • Type B: primary spermatocyte (2n):

    • Pushed toward lumen

    • Meiosis I forming secondary spermatocytes (n) which undergo

    • Meiosis II forming 4 spermatids (immature sperm)


Spermatogenesis spermatids to sperm l.jpg
Spermatogenesis: Spermatids to Sperm

  • Spermatogenesis: (spermatids  sperm) a streamlining process

    • Sperm head (filled with DNA)

    • Acrosome (filled with lysosomal enzymes)

    • Midpiece (mitochondrial wrapped contractile filaments)

    • Tail (flagellum)

Figure 27.9a


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Spermatogenesis

  • Sertoli (Sustentacular) cells:

  • Divide seminiferous tubule into 2 compartments;

    • Isolate newly formed sperm from blood:

    • blood-testis barrier prevents formation of antibodies against sperm


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Hormonal Regulation: Male

  • Brain-testicular axis:

  • Interactions between:

    • Hypothalamus

    • Anterior pituitary

    • Testes


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Brain-testicular axis

  • Hypothalamus  Gonadotropin-Releasing Hormone (GnRH)

  • GnRHAnterior pituitary secretion of

    • Leutinizing Hormone (LH a.k.a. Interstitial Cell Stimulating Hormone: ICSH)

      • Stimulates interstitial cells to produce testosterone

    • Follicle Stimulating Hormone (FSH)

      • allows spermatogenesis by making cells receptive to testosterone


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Brain-testicular axis

  • Testosterone acts locally as the trigger for spermatogenesis

  • Testosterone inhibits:

    • Release of GnRH (hypothalamus)

    • Release of gonadotropins (anterior pituitary)

  • Inhibin is produced by Sertoli cells when sperm counts are high; inhibits GnRH & FSH release


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Hormonal Regulation of Testicular Function

  • Feedback inhibition on hypothalamus & pituitary from:

    • Rising levels of testosterone

    • Increased inhibin

Figure 27.10


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Brain-testicular axis

  • Perinatal FSH, LH & testosterone levels:

    • Near pubertal levels to allow development of the male reproductive system;

    • After a few months of age the levels drop to low levels until onset of puberty


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Testosterone mechanism & effects:

  • Testosterone is synthesized from cholesterol & exerts effects by activating specific genes

  • Testosterone targets accessory organs (ducts, glands & penis) causing them to grow to adult proportions


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Testosterone mechanism & effects:

  • Testosterone induces:

  • Secondary sex characteristics:

    • pubic & axillary hair

    • voice change

    • facial hair

    • thickening of the skin

    • increased sebum production

    • increase in bone & muscle mass


Female reproductive system l.jpg
Female Reproductive System

Figure 27.11

  • Anatomy

    • Ovaries

    • Duct System:

      • Fallopian Tubes

      • Uterus

    • Vagina & external genitalia


Ovaries l.jpg
Ovaries

  • Ovaries: primary female reproductive organ

  • Ovaries produce the female

    • Gamete (ova/egg)

    • Sex hormones (estrogens & progesterone)

Figure 27.14a


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Ovaries

  • Ovaries: paired organ

    • Found on either side of the uterus

    • Held in place by ligaments

Figure 27.14a


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Ovaries

Figure 27.12

  • Ovarian follicles within the ovary consist of an:

    • Oocyte (immature ovum) encased in one or more layers of cells

      • Single layer: follicle cells;

      • Multiple layers: granulosa cells

    • Follicles at different stages have different structures


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Ovaries

Figure 27.12

  • Follicle stages & structures:

    • Primordial follicle: single layer of follicle cells surrounding oocyte

    • Primary follicle: two or more layers of granulosa cells

    • Secondary follicle: fluid filled spaces appear within granulosa & merge to form the vesicular follicle.


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Ovaries

Figure 27.12

  • Follicle stages (cont):

    • Vesicular (Graafian) follicle: bulges from the ovary surface & will rupture at ovulation releasing the oocyte

    • Corpus luteum: follicle remnant after rupture that forms the glandular corpus luteum


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Female Duct System

Figure 27.14a

  • Fallopian tubes: uterine tubes, oviducts

    • Infundibulum: open funnel shaped structure with finger-like projections (fimbriae) that drape over ovary

    • Ampulla: widened region arching over ovary (the usual site of fertilization)

    • Isthmus: narrowed region where tube enters upper region of uterus


Female duct system uterus l.jpg
Female Duct System - Uterus

  • hollow, thick walled, pear shaped, muscular organ that receives, retains & nourishes a fertilized ovum

  • Uterine support comes from the mesometrium, the lateral cervical ligaments, the uterosacral ligaments & the round ligaments


Female duct system uterine wall l.jpg
Female Duct System: Uterine Wall

  • Endometrium: mucosal lining of columnar epithelium

  • Myometrium: muscular middle layer: interlaced bundles of smooth muscle

  • Perimetrium: outer covering of visceral peritoneum


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Female Duct System: Uterine Wall

  • endometrium is a dynamic layer of epithelium with two layers

  • Stratum functionalis: undergoes cyclic changes in response to ovarian hormones & is shed during menstruation

  • Stratum basalis: deeper layer that forms a new stratum functionalis after menstruation

Figure 27.15


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Vagina

Figure 27.14a

  • female organ of copulation & birth canal


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Vagina

Figure 27.14a

  • 3 layers

  • Mucosa: stratified squamous epithelium with rugae (ridges)

  • Muscularis: smooth muscle

  • Adventitia: fibroelastic connective tissue


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Vagina

Figure 27.14a

  • Environment:

  • In adults, vaginal pH is decreased

    • Helps to prevent infection

    • Also hostile to sperm

  • In adolescents, vaginal pH is increased

    • More alkaline environment presents an increased risk for Sexually Transmitted Disease


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Vagina

  • Proximal end of the vagina:

  • Surrounds the cervix of the uterus

  • Forming a recess (fornix) around the cervix;

  • Distal end forms the vaginal orifice with mucosal hymen (in virginal females)


External genitalia l.jpg
External Genitalia

  • Mons pubis: rounded fat pad overlying the pubic symphysis

  • Labia

    • Labia majora: two fatty skin folds with hair (homologous to scrotum)

    • Labia minora: two smaller, hairless skin folds (homologous to the male ventral penis)

Figure 27.16


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External Genitalia

  • Vestibule = the recess surrounded by the labia minora includes:

    • Urethral opening

    • Vaginal orifice

    • Vestibular gland orifices

Figure 27.16


External genitalia51 l.jpg
External Genitalia

  • Clitoris:

    • Small, protruding structure:

    • Composed of erectile tissue (penis homolog)

    • Hooded by anterior folds of the labia minora (prepuce of clitoris)

  • Perineum: diamond shaped region from pubic arch to coccyx & laterally to the ischial tuberosities


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Oogenesis

Figure 27.20

  • maturation process for the ovum (egg);

  • Oogonia: fetal stem cells (diploid) start meiosis to become primary oocytes.


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Oogenesis

Figure 27.19


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Oogenesis

  • Two routes for secondary oocyte:

    • If fertilized - secondary oocyte expels second polar body (nonviable) & rapidly completes Meiosis II

    • If unfertilized - secondary oocyte deteriorates

Figure 27.19


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The Ovarian Cycle:

  • 28 Days

  • Follicular phase: days 1-14

  • Luteal phase: days 14-28


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Follicular phase:

Figure 27.20

  • Days 1 -14

  • Primordial follicle matures to form a primary follicle

  • Follicular cells proliferate forming granulosa cells which regulate / stimulate oocyte maturation


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Follicular phase:

Figure 27.20

  • Days 1 -14 (cont)

  • Connective tissue condenses around the follicle forming:

    • The theca folliculi; theca & granulosa cells produce estrogens

  • Granulosa cells produce:

    • A transparent membrane (zona pelucida) around the oocyte

    • Clear liquid forms the antrum (cavity) of the secondary follicle


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Follicular phase:

Figure 27.20

  • Days 1 -14 (cont)

  • Antrum expands until the oocyte is isolated on a stalk within the follicle

  • Now ~1in. in diameter the vesicular follicle bulges from the surface of the ovary; the oocyte is surrounded by a capsule of granulosa cells (corona radiata)


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Follicular phase:

Figure 27.20

  • Day 14

  • Ovulation: the vesicular follicle wall ruptures, expels the secondary oocyte with its corona radiata


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Luteal phase:

Figure 27.12

  • Days 14-28

  • The ruptured follicle collapses & remaining theca & granulosa cells enlarge & form an endocrine gland: the corpus luteum

Figure 27.20


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Luteal phase:

Figure 27.12

  • Days 14-28 (cont)

  • The corpus luteum secretes progesterone & some estrogen

    • If no fertilization occurs the corpus luteum degenerates to form the corpus albicans (scar)

    • If fertilization occurs the corpus luteum persists until the placenta takes over hormone production (~3 mos.)

Figure 27.20



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Hormonal Regulation:

  • During puberty GnRH (& thus FSH/LH) production increases until the adult cycle is achieved:

    • First menses = menarche

Figure 27.22a, b


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Hormonal Interactions:

  • Day 1

  • Day 1: GnRH levels rise stimulating anterior pituitary release of FSH & LH

  • FSH & LH stimulate follicle growth & maturation;

    • LH stimulates theca cells to produce androgens which diffuse into the follicle & are converted to estrogens by granulosa cells



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Hormonal Interactions:

  • Rising estrogen levels provide negative feedback to the anterior pituitary

  • Inhibiting release of FSH/LH but encouraging storage of FSH/LH

  • Within the ovary estrogen intensifies the effect of FSH enhancing estrogen production


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Hormonal Interactions:

  • As estrogen continues to rise it exerts a positive feedback on the adenohypophysis resulting in a burst of LH

Figure 27.21


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Hormonal Interactions:

  • Day 14

  • LH surge prompts maturation of the primary follicle to form the secondary oocyte & triggers ovulation

Figure 27.21


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Hormonal Interactions:

  • At ovulation, estrogen levels decline

  • LH surge also transforms the ruptured follicle into a corpus luteum

    • Stimulates production of progesterone & estrogen

Figure 27.21


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Hormonal Interactions:

  • Rising progesterone & estrogen exert negative feedback of FSH/LH release

Figure 27.21



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Hormonal Interactions:

  • Day 27

  • After the corpus luteum stops functioning the decline in hormone levels allows

  • {Day 1} Increased GnRH (FSH/LH)



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The Uterine Cycle

  • Days 1-5

  • Menstrual phase: uterus sheds stratum functionalis of endometrium.

    • Hormone levels are at their lowest

    • GnRH & FSH begin to rise

    • The functionalis layer detaches from the stratum basalis & is passed through the vagina (3-5 days of bleeding)


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The Uterine Cycle

  • Days 6-14

  • Proliferative phase: Endometrium rebuilds itself.

    • Estrogen induces progesterone receptors in the endometrial cells;

    • The proliferative phase ends with ovulation & associated rise in LH


The uterine cycle76 l.jpg
The Uterine Cycle

  • Days 15-28

  • Secretory phase: endometrium is prepared for implantation of the embryo.

  • Progesterone acts on the endometrium

    • Spiral arteries enhance blood supply

    • The functionalis is converted into a secretory mucosa (secretes glycogen)


The uterine cycle77 l.jpg
The Uterine Cycle

  • Days 15-28

  • As progesterone levels rise, LH levels decline:

    • If fertilization has not occurred the progesterone level declines (corpus luteum degenerates) & the endometrium degenerates.

    • If fertilization has occurred: Ch 28


Menstrual cycle l.jpg
Menstrual cycle

  • Gonadotropins, Hormones, & the Ovarian & Uterine Cycles

  • FSH, LH, Follicle, Uterus

Figure 27.22 a,b,c, d


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Estrogen mechanism & effects:

  • Estrogen induces:

  • Secondary sex characteristics:

    • Growth of the breasts

    • Increased deposits of subcutaneous fat

    • Widening & lightening of the pelvis


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Female sexual response

  • Clitoris, vaginal mucosa & breasts become engorged with blood

  • Clitoral & Nipple erection

  • Increased vestibular gland activity lubricates the vestibule


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Female orgasm

  • No ejaculation

  • Muscle tension increases throughout the body

  • Pulse & BP rise

  • Uterus contracts rhythmically

  • No refractory period


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Sexually Transmitted Disease

  • Gonnorrhea: Neisseria gonnorrhea

  • Invades the mucosa of the reproductive tracts:

    • Congenital  blindness

    • Male: urethritis, painful urination

    • Female: variable symptoms: may lead to PID (pelvic inflammatory disease) & sterility


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Sexually Transmitted Disease

  • Syphilis: Treponema pallidum:

  • Primary: Initial presentation of chancre at the site of infection;

    • Painless, heals spontaneously;

    • Congenital  death

  • Secondary: pink skin rash, fever & joint pain

  • Tertiary: destructive lesions (gumma) in CNS, blood vessels, bone & skin


Sexually transmitted disease84 l.jpg
Sexually Transmitted Disease

  • Chlamydia: Chlamydia trachomatis;

  • Congenital: conjunctivitis  blindness, pneumonia

  • Male: urethritis, testicular pain, urogenital inflammation, arthritis

  • Female: 80% no symptoms; PID may lead to sterility


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Final Freebie

  • All somatic body cells = diploid

  • _______ogonia = diploid

  • Primary ___cyte = diploid

  • Secondary ___cyte = haploid

  • Gamete (Sperm/ova) = haploid















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