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Anatomy and physiology of the prostate

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Single, midline lobed structure. Component of the male reproductive system. One of two key glandular components. Prostate ... Embryology and development ... – PowerPoint PPT presentation

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Title: Anatomy and physiology of the prostate


1
Anatomy and physiologyof the prostate
  • Dr Andrew Potter
  • Registrar
  • Department of Radiation Oncology
  • Royal Adelaide Hospital

2
Prostate - overview
  • Single, midline lobed structure
  • Component of the male reproductive system
  • One of two key glandular components
  • Prostate (single)
  • Seminal vesicles (paired)
  • Produce nutritive and lubricating fluid - seminal
    fluid in which spermatozoa are conducted

3
Male reproductive tract
4
Structure - macro
  • Partly glandular, partly fibromuscular
  • Most of its glandular tissue lies posterior and
    lateral to prostatic urethra
  • About the size of a walnut
  • Surrounds prostatic urethra
  • Enclosed within thin dense fibrous capsule
  • Inner loose sheath derived from pelvic fascia
    prostatic sheath
  • Continuous inferiorly with superior fascia of
    urogenital diaphragm
  • Posteriorly it is part of rectovesical septum
  • Separates bladder, seminal vesicles and prostate
    from rectum
  • Prostatic venous plexus lies between fibrous
    capsule and prostatic sheath
  • Base, apex and 4 surfaces (posterior, anterior
    2 infero-lateral)

5
Structure - lobes
  • Anterior
  • Tissue lying anterior to urethra
  • No glands fibromuscular tissue only
  • Median
  • Cone-shaped region between ejaculatory ducts and
    urethra
  • Lateral (left right)
  • Main mass of gland, continuous posteriorly
  • Separated by prostatic urethra
  • Posterior
  • Describes postero-medial part of lateral lobes
    palpable through rectum on DRE

6
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7
Structure - micro
  • Fibro-elastic capsule
  • Incomplete septa extend into central stroma ? 50
    poorly defined lobules
  • Supporting tissue contains smooth muscle fibres
    innervated by sympathetics (? contraction)
  • Glandular tissue consists of tubulo-acinar
    glands, concentric around urethra
  • Main prostatic glands are in peripheral 2/3 of
    gland drain via 20 long ejaculatory ducts into
    distal urethra
  • These glands give rise to cancer
  • Inner 1/3 of gland consists of submucosal glands
    drain via short urethral sinuses
  • Innermost glands mucosal glands open directly
    into urethra
  • Mucosal and submucosal glands increase in size
    with age
  • Glandular epithelium is pseudo-stratified
  • Transitional epithelium in ducts

8
Prostate - histology
9
Prostate - zones
  • CZ - central zone
  • 20 of prostate volume
  • Benign hypertrophy
  • 25 of malignancies
  • TZ - transitional zone
  • 5 of prostate volume
  • PZ - peripheral zone
  • 70 of prostate volume
  • 70 of malignancies

10
Position and relations
  • Base of prostate (vesicular surface) closely
    related to bladder neck
  • Prostatic urethra enters middle of base near
    anterior surface
  • Apex
  • Inferior
  • related to superior fascia of urogenital
    diaphragm
  • rests on sphincter urethrae muscle
  • embraced by medial margins of levator ani muscles

11
Position and relations
  • Posterior surface
  • triangular and flattened transversely
  • faces posteriorly and slightly inferiorly towards
    urogenital diaphragm
  • rests on ampulla of rectum (therefore this
    surface is palpable PR)
  • shallow median groove/sulcus demarcates lateral
    lobes
  • lateral lobes often fused sometimes called
    posterior lobe
  • superiorly on posterior surface is a shallow
    groove where ejaculatory ducts enter the prostate
  • this groove marks the middle lobe between
    ejaculatory ducts and urethra.
  • Middle lobe lies posterior to uvula vesica on
    bladder
  • Superiorly in contact with inferior part of
    trigone of bladder
  • Prostatic utricle located in substance of middle
    lobe

12
Position and relations
  • Anterior surface
  • Transversely narrow and convex
  • Extends from apex to base
  • Inferolateral surfaces meet anteriorly with
    anterior surface, resting on fascia covering
    levator ani
  • Prostatic ductules (20-30) open into prostatic
    sinuses on each side of urethral crest and
    posterior wall of prostatic urethra

13
Blood supply
  • Arterial supply
  • Arteries derived from internal pudenal, inferior
    vesical and middle rectal arteries (branches of
    internal iliac)
  • Venous drainage
  • Veins form prostatic venous plexus around sides
    and base of prostate located between capsule
    and sheath
  • Drains into internal iliac veins
  • Also communicates with vesical venous plexus and
    vertebral venous plexuses
  • Postulated mechanism for L-spine mets being common

14
Lymphatics and innervation
  • Lymphatic drainage
  • Lymph vessels terminate in internal iliac and
    sacral lymph nodes
  • Some vessels from posterior surface pass with
    lymph vessels from bladder to external iliac LNs
  • Innervation
  • Parasympathetic fibres arise from pelvic
    splanchnic nerves
  • Sympathetic fibres from inferior hypogastric
    plexuses

15
Embryology and development
  • Multiple endodermal outgrowths arise from
    prostatic portion of urethra ? grow into
    surrounding mesenchyme
  • Endoderm differentiates into glandular epithelium
  • Mesenchyme differentiates into dense stroma and
    smooth muscle

16
Seminal vesicles
  • Paired, pouchlike structures, 5cm long
  • Posterior to and at base of bladder
  • Produces viscous, alkaline fluid to neutralise
    acidity of female genital tract
  • About 60 of ejaculate
  • Contains fructose - energy source for sperm

17
Function
  • Prostate
  • Produces alkaline fluid to neutralise acidic
    vaginal secretions (sperm more viable in more
    alkaline conditions)
  • Clotting enzymes and fibrinolysin - clots semen
    to hold it in female reproductive tract, with
    fibrinolysin acting shortly thereafter to release
    motile sperm

18
Function
  • Seminal vesicles
  • Supply fructose - nutrition for sperm
  • Secrete prostaglandins - contract smooth muscle
    in male and female reproductive systems (sperm
    transport)
  • Provide the bulk of ejaculated fluid to assist in
    sperm conduction
  • Secrete fibrinogen to form the basis of clots

19
Ejaculation
  • Result of a spinal reflex in 2 phases
  • Emission
  • Sympathetic supply stimulates smooth muscle
    contraction in prostate, reproductive ducts and
    seminal vesicles
  • Delivers prostatic fluid sperm seminal
    vesicle fluid (semen) into urthera
  • Expulsion
  • Constriction of bladder sphincter to prevent
    retrograde ejaculation
  • Reflex rhythmic contraction of skeletal muscles
    at base of penis expels semen through urethra to
    outside

20
Effects of testosterone
  • Promotes development of prostate and seminal
    vesicles - weeks 7-12 of gestation
  • Promotes hypertrophy into adulthood
  • Benign prostatic hypertrophy (BPH) is a common
    finding with age
  • Requires the presence of androgens but not
    necessarily causal
  • ? Related to prostate cancer risk
  • Androgen deprivation a target of therapy

21
Prostate specific antigen (PSA)
  • Protein produced by glandular tissue of prostate
  • Present in small but measurable quantities in
    normal, healthy men
  • normal range increases with age
  • Elevated PSA suggests
  • Benign hypertrophy
  • Recent ejaculation
  • Prostatitis/infection
  • Prostate cancer
  • FreeBound PSA ratio and PSA/Prostatic index may
    help differentiate benign from malignant causes

22
Summary - prostate
  • Single, midline glandular structure
  • Part of the male reproductive system
  • Function is to produce prostatic fluid - a
    component of semen, working closely with seminal
    vesicles
  • Closely related to seminal vesicles, rectum,
    bladder
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