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Male Reproductive System
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Male Reproductive Organs scrotum and testes ducts accessory sex glands penis
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Male Reproductive Organs
penis
testicle within scrotum
epididymis
ductus deferens
seminal vesicleprostate gland
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Scrotum (cont.)
pendulous sac of loose skin and fascia supports testes divided internally by medial septum,
supporting each testis left testes is usually suspended lower
than the right so they are not compressed against each other
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Scrotum (cont.)
location (outside the body) and muscle fibers regulate temperature of the testes
production and survival of sperm require temperature about 3o lower than normal body temperature
contains Dartos muscle
- contains smooth muscle fibers
- causes wrinkling of scrotum
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Cremaster Muscle continuation of internal oblique muscle stimulation by touch or cold results in
contraction of muscle pulling testicles closer to the body
presence of cremasteric reflex indicates integrity of the first lumbar nerve segment
absence of reflex indicates damage
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Testes primary sex organs; male gonads paired oval glands two inches long, one inch in diameter develop high in posterior fetal abdominal wall descend into scrotum during seventh month
of fetal development suspended in scrotum by spermatic cord
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Testes (cont.)
Produce:
- sperm
- testosterone divided into compartments (about 250) called
lobules formed by inward extensions of tunica albuginea
- contain several highly coiled tubules called seminiferous tubules
spermatozoa are formed in walls of tubules
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Covering of Testes tunica vaginalis
- pouch-like sac of peritoneum
- formed during descent of the testes tunica albuginea
- internal to tunica vaginalis
- dense, white, fibrous tissue
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Cryptorchidism
occurs when testes fail to descend into scrotum results in sterility because of higher temperature in
pelvic cavity
- higher temperature destroys cells involved in development of sperm cells
Treatment:
- human growth hormone
- surgery
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Seminiferous Tubules Consists of:
- spermatogenic cells
- sustenacular cells
- blood-testis barrier
- basement membrane
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Spermatogenic Cells line walls of seminiferous tubules towards lumen of tubules cells are
progressively more mature Cells in various stages of development:
- spermatogonia
- primary spermatocytes
- secondary spermatocytes
- spermatids
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Spermatogonia most immature cells lie next to basement membrane have 46 chromosomes (diploid)
Primary Spermatocytes produce four spermatids have 46 chromosomes (diploid)
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Secondary Spermatocytes cells formed by first nuclear division
(reduction division) each cell has 23 chromosomes (haploid)
Spermatids cells formed by second nuclear division
(equatorial division) - mitotic each cell has 23 chromosomes (haploid)
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Sustentacular Cells extend from outer basement membrane to the
lumen support and nourish developing cells immature cells are embedded in luminal
membranes secrete inhibin
- protein hormone
- directly affects anterior pituitary by inhibiting FSH secretion
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Follicle-Stimulating Hormone FSH encourages spermatogenesis and
stimulates sustentacular cells once adequate spermatogenesis level is
achieved, inhibin is secreted
- inhibits FSH secretion and decreases spermatogenesis
if spermatogenesis occurs too slowly, lack of inhibin permits FSH secretion
- increases rate of spermatogenesis
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Blood-Testis Barrier
developing sperm have surface antigens recognized as foreign by immune system
prevents an immune response against sperm
isolates cells from blood
Basement Membrane surrounds each seminiferous tubule
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Mature Sperm travel through seminiferous tubules to
straight tubules through rete testis and from testes into epididymis
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Epididymis
half-moon-shaped organ encircling posterior of each testis
site of sperm maturation contains highly coiled tube called the ductus
epididymis used for storage of spermatozoa continuous with ductus deferens during ejaculation, muscle contractions move
sperm and seminal fluid into ductus deferens
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Ductus Deferens also called vas deferens or seminal duct 18 inch long tube carries spermatozoa from epididymis of
each testis to an ejaculatory duct ascends along posterior border of
epididymis
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Ductus Deferens (cont.) enters pelvic cavity through inguinal canal loops over side and down posterior surface
of urinary bladder terminal end is called ampulla stores sperm and moves sperm from
epididymis to urethra seminal vesicle joins at distal end of
ampulla
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Vasectomy method of sterilization portion of each ductus deferens is
removed sperm production continues but cannot
be expelled from body
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Ejaculatory Duct distal end of ampulla one inch long formed from union of duct from seminal
vesicle and ductus deferens passes into prostate gland joins prostatic urethra eject sperm into prostatatic urethra just
prior to ejaculation
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Urethra tube extends from urinary bladder to tip of penis about 8 inches long Three parts:
- prostatic urethra
- membranous urethra
- spongy urethra
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Prostatic Urethra passes through prostate gland
Membranous Urethra passes through urogenital diaphragm
Spongy Urethra passes through corpus spongiosum of
penis
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Male Reproductive Glands seminal vesicles prostate gland bulbourethral glands
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Seminal Vesicles paired, convoluted, pouch-like structures posterior to and at base of urinary bladder secrete an alkaline, viscous fluid
- contains fructose, prostaglandins, and fibrinogen
- helps to neutralize acid of female tract
- provides nourishment for sperm
- 60% of the volume of semen
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Fructose used for ATP production
Prostaglandins contribute to sperm motility and viability may also stimulate muscular contraction
within female reproductive tract
Fibrinogen aids in semen coagulation
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Prostate Gland single, donut-shaped, walnut size inferior to urinary bladder surrounds superior portion of urethra secretes milky, slightly acidic fluid
- contains citric acid, acid phosphate, clotting emzymes, and fibrinolysin
- aids in sperm motility and viability
- 25% of the volume of semen
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Bulbourethral Gland also known as Cowper’s glands paired, size of peas lie beneath prostate gland on either side of
membranous urethra ducts open into spongy urethra secrete alkaline, mucus-containing fluid
- neutralizes acid ; lubricates end of penis
- 10% of the volume of semen
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Penis cylindrical organ transports urine and semen through urethra
to the outside of body Consists of:
- body
- glans penis
- root
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Body of the Penis composed of three cylindrical masses of
spongy erectile tissue enclosed in fascia and skin permeated by
blood sinuses sexual stimulation causes dilation of arteries
supplying penis blood accumulates in erectile tissue, and penis
swells and elongates, producing an erection
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Erectile Tissue corpora cavernosa penis
- two dorsolateral masses corpus spongiosum penis
- smaller midventral mass
- contains spongy urethra
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Glans Penis distal end of corpus spongiosum slightly enlarged forms tip of penis Anatomy:
- corona
- external urethral orifice
- prepuce or foreskin
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Corona margin of glans penis
External Urethral Orifice slitlike opening of urethra
Prepuce or Foreskin covers the glans penis often removed in circumcision
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Circumcision removal of part or all of the prepuce many physicians believe it decreases risk of
urinary tract infections, possible protection from penile cancer, and lowers risk of sexually transmitted diseases
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Root of Penis attached portion Consists of:
- bulb of penis
expanded portion of the base of the corpus spongiosum penis
- crura
separated and tapered portions of the corpora cavernosa penis
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Semen Mixture of:
- sperm secretions of the seminal vesicles,
prostate gland, and bulbourethral glands
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Characteristics of Semen volume
- 2.3 - 2.5 ml per ejaculation color
- milky appearance because of prostate secretion
sperm count
- 50 - 150 million sperm per ml
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Characteristics of Semen (cont.)
motility of sperm
- at least 60% active, good forward motility in order to be viable
pH is slightly alkaline (7.20 - 7.60) specific gravity - denser than water (1.0280) morphology
- at least 80% normally shaped in order to be viable
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Characteristics of Semen (cont.)
antibiotics - seminalplasmin
- has ability to destroy certain bacteria nutrients - fructose
- provides energy source necessary for sperm motility
buffers - phosphate and bicarbonate
- maintain relatively constant pH of semen
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Characteristics of Semen (cont.)
enzymes - hyaluronidase, proteinases
- digest material covering ovum clotting enzymes
- coagulate semen fibrinolysin
- liquifies coagulated semen
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Hormonal Control of Male Reproductive System Controlled by:
- GnRH (gonadotropin releasing hormone)
- FSH (follicle-stimulating hormone)
- LH (luteinizing hormone)
- inhibin
- testosterone
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Gonadotropin Releasing Hormone secreted by hypothalamus carried by anterior pituitary gland
- stimulates the release of gonadotropins,
follicle-stimulating hormone, and luteinizing hormone
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Follicle-Stimulating Hormone stimulates sustentacular cells in
seminiferous tubules
- secrete chemicals that stimulate spermatogenesis
- secrete inhibin which has a negative feedback effect on anterior pituitary gland, inhibiting secretion of FSH
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Luteinizing Hormone stimulates interstitial endocrinocytes
located in spaces within seminiferous tubules
stimulates testosterone secretion
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Androgens male sex hormones testosterone is principal androgen
- synthesized from cholesterol in the testes
- in some target cells testosterone is not active and must be reduced and converted into dihydrotestosterone (DHT)
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Androgen Functions male pattern of development before
birth sexual characteristics sexual functions metabolism
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Male Pattern of Development Before Birth development of reproductive system ducts descent of testes development of external genitals (by DHT) converts some androgens into estrogens
which aid in brain development
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Sexual Characteristics development and enlargement of male
sex organs development of male secondary sex
characteristics
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Male Secondary Sex Characteristics muscular and skeletal growth wide shoulders, narrow hips pubic, axillary, facial, and chest hair
growth thickening of skin increased sebaceous gland secretion enlargement of larynx and deepening of
voice
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Sexual Functions male sexual behavior spermatogenesis sex drive
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Metabolism androgens are anabolic hormones which
stimulate protein synthesis
- leading to heavier muscle and bone mass in males
cause cessation of bone growth by stimulating closure of epiphyseal plate
increase rate of metabolism and production of red blood cells
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