Functions of the Male Reproductive System

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Functions of the Male Reproductive System

• Production of gametes
• Male sex cells, i.e., sperm
• Synthesis of androgens
• Male sex hormones, i.e., testosterone
• Delivery of sperm into the female reproductive
  tract.

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• Scrotum
• Sac of skin and superficial fascia
• Contains male gonads (testes)
• Low T? by 3?C.

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Vervet Monkey
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Cremaster muscle

• As a result of cremaster muscle contraction
• The distance btwn the testes and abdominal cavity
  will
• The distance btwn the testes and the tibia will
• As ambient air T? decreases, the level of
  cremaster muscle contraction will

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Testes

• Male gonads
• Surrounded by 2 tunics
• Tunica vaginalis
• Derived from the parietal peritoneum.
• Tunica albuginea

Tunica vaginalis
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The testicle must migrate from the its site of
formation (at the level of the kidney) through
the belly and groin, and into the scrotum. It can
get stuck anywhere along this path between the
kidney and the scrotum. Such failure to descend
properly is known as cryptorchidism.
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Testes

• Divided into lobules
• Each lobule contains seminiferous tubules the
  sperm factories
• Btwn the seminiferous tubules are interstitial
  cells (a.k.a. Leydig cells), which secrete
  testosterone

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Name these cells! What do they do? Why do we see
small blood vessels associated with them?
What are all these tubes? What is their function?
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Testes

• Receive blood from the testicular a.
• Drained by the testicular v.
• A section of the testicular v. called the
  pampiniform plexus surrounds the testicular a. as
  it descends to the testis. How does this help
  keep the testes cool?

WARM ?
? COOL
Testis
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Testes

• All blood vessels, lymphatic vessels, and nerves
  going to and from the testis are wrapped in a
  connective tissue sheath called the spermatic
  cord.
• It also contains the vas deferens which
  transports sperm.

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Penis

• Penis scrotum make up the external genitalia
• Delivers semen into the vagina.
• Root, shaft, and glans penis
• Prepuce (foreskin) covers the glans penis

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Penis

• Contains the urethra as well as 3 erectile
  bodies
• 2 dorsal erectile tissues known as corpora
  cavernosa
• 1 midventral tissue known as corpus spongiosum
• Surrounds penile urethra
• Expands distally to form the glans penis

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Epididymis

• One behind each testis
• Site of sperm maturation and storage
• Sperm travel from the seminiferous tubules to the
  epididymis via the rete testis
• Contains smooth muscle

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Prostatic urethra
Ejaculatory duct
Ejaculatory duct
Seminal vesicle
Seminal vesicle
Vas deferens
Vas deferens
Epididymis
Epididymis
Rete testis
Rete testis
Seminiferous tubule
Seminiferous tubule
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Urethra

• 3 sections
• Prostatic
• Within the prostate
• Membranous
• Within the urogenital diaphragm
• Penile (spongy)
• Within the penis
• Bounded by the external and internal urethral
  orifices.

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Seminal Vesicles

• Found on posterior bladder
• Secrete seminal fluid
• Makes up 60 of semen
• Contains
• Fructose
• Prostaglandins
• Coagulating enzyme

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Prostate Gland

• Found inferior to the bladder encircling the
  urethra
• Secretes prostatic fluid
• Makes up 30 of semen
• Contains
• Citrate
• Prostate specific antigen

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Bulbourethral Glands

• A.k.a. Cowpers glands
• Secrete a basic mucus after erection but prior to
  ejaculation in order to flush out the urethra

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10 testicular fluid


60 seminal fluid
SEMEN

30 prostatic fluid
Protects Activates Transports
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Cortical activity (Sexual thoughts)
Mechanical Stimulation
Increased parasympathetic motor output to the
penis
Sensory info sent to spinal cord
Increased release of nitric oxide on penile
arterioles
Erection
Dilation of penile arterioles
Increased influx of blood into the penis and
decreased efflux of blood from the penis
Corpus spongiosum and cavernosa engorge with blood
Compression of penile venules
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Increased sympathetic motor output to the penis
Sexual sensory stimuli reach threshold level
Emptying of reproductive ducts and glands into
the urethra
Contraction of internal urethral sphincter
Contraction of bulbospongiosus muscles
Prevention of urine release or semen reflux
Ejaculation
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• All body cells except for sperm and eggs are
  diploid they have 2 copies of each chromosome.
• 46 total
• 23 pairs
• Sperm and eggs are haploid they have 1 copy of
  each chromosome.
• 23 total

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23
46
23
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Diploid body cells such as skin cells, muscle
cells, nerve cells, etc.
Mitosis
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Mitosis
Spermatogenesis
Diploid germ cells
Haploid Sperm
Spermatogenesis sperm formation. Consists of 2
phases meiosis and spermiogenesis.
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Primary Spermatocyte (46)
Spermatogonium (46)
Type B Spermatogonium (46)
Replicates its DNA
Divides via mitosis
Type A Spermatogonium (46)
Stays at the periphery of the seminiferous to
maintain a population of germ cells.
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Spermatid (23)
Secondary Spermatocyte (23)
Spermatid (23)
Primary Spermatocyte (46)
Meiosis I
Meiosis II
Spermatid (23)
Secondary Spermatocyte (23)
Spermatid (23)
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Spermiogenesis
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Hypothalamus releases GnRH
Anterior pituitary releases FSH and LH
FSH causes testicular Sertoli cells to release
androgen binding protein (ABP)
LH causes testicular interstitial cells to
release testosterone
ABP concentrates testosterone in the seminiferous
tubules
Testosterone enters the blood stream
Testosterone stimulates male sexual
characteristics
Testosterone stimulates spermatogenesis
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Testosterone levels in the blood are too high
Testosterone inhibits pituitary release of FSH
and LH
Testosterone release by interstitial cells
declines
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Rate of sperm synthesis is too high
Sertoli cells release inhibin
Inhibin decreases hypothalamic GnRH release
Pituitary release of FSH and LH declines
Testosterone release by interstitial cells and
ABP release by Sertoli cells decline
Rate of sperm synthesis declines
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What hormone would you want to stimulate or block
in order to develop a best-selling birth control
pill for men?
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Testosterone

• Masculinizes embryonic genitalia
• Masculinizes brain
• Pubescent development of reproductive structures
• Promotes growth of axillary and facial hair
• Enlargement of larynx
• Enhances skeleton and muscle mass
• Boosts metabolic rate
• Thickens skin