THE MALE REPRODUCTIVE SYSTEM
Feb 23, 2016
THE MALE REPRODUCTIVE SYSTEM
HOMEOSTASIS
male & female reproductive organs work together to produce offspring
female reproductive organs also contribute to sustaining the growth of embryos and fetuses
Sexual Reproduction
process by which organisms produce offspring by making germ cells (gametes)
fertilization: when male gamete (sperm) unites with female gamete (secondary oocyte) fertilized egg
males & females have anatomically distinct reproductive organs that function to
1. produce gametes2. facilitate fertilization3. sustain growth of embryo & fetus (female)
Males Females
Gonads: testesDucts
store & transport gametes
Accessory Sex Glands Supporting
Structures Penis
Gonads: ovariesDucts
transport gametesAccessory Sex
GlandsSupporting
Structures: Uterus
Reproductive Organs
Male Reproductive System
Organs:1. Testes2. system of ducts3. accessory sex glands4. supporting structures:
scrotum penis
Functions of the Male Reproductive System
1. Testes produces sperm & the male sex hormone Testosterone (T)
2. Ducts transport, store, & assist in maturation of sperm
3. Accessory sex glands secrete most of liquid portion of semen
4. Penis contains the urethra, passageway for ejaculation of semen & excretion of urine
5. Scrotum protects temperature-sensitive testes from temperature fluctuations
Scrotum
a supporting structure for the testesfeatures:loose skin & superficial fascia attached from
root of penisexternally:
raphe: median ridge that separates scrotum into right & left sides
internally: scrotal septum: divides scrotum into 2 sacs,
each with 1 testes
Scrotum - 2
features continued:dartos muscle: smooth muscle fibers
contraction causes wrinkled appearance (reduces heat loss)
cremaster muscle: skeletal muscle2 features regulate temp of testes:1. location outside trunk keeps temp 2 – 3 °C lower
than core body temp2. in response to cold temps, both muscles
contract moving testes closer to body so can absorb body heat
Testes (plural)/ Testis (singular)
aka testiclespaired oval glands develop near kidneys
begin descent into scrotum thru inguinal canals during latter half 7th month gestational age
leading edge covered with peritoneum called tunica vaginalis Hydrocele: serous fluid collects between this
& testis (injury or inflammation of epididymis)
Testes - 2
tunica albuginea: internal to tunica vaginalis dense irregular CT extends inward into testis forming septa:
divide testis into series of 200 – 300 lobules (internal compartments)
each lobule contains 1 – 3 coiled seminiferous tubules : *site of production of semen
spermatogenesis: process by which seminiferous tubules produce sperm
Seminiferous Tubules
2 types of cells:1. spermatogenic cells
sperm-forming cells: spermatogonia: stem cells primordial germ
cells arise in yolk sac & enter testes during 5th wk of
development: remain dormant until puberty 1° spermatocytes, 2° spermatocytes, spermatids,
sperm cells (layers of progressively more mature cells)
2. Sertoli cells function in supporting spermatogenesis
Spermatogenesis
Sertoli Cells
aka sustentacular cells extend from basement membrane lumen of
tubuleheld together by tight junctions
form obstruction known as the blood-testis barrier: all substances must pass thru Sertoli cells to reach developing sperm cells (after spermatogonia)
Sertoli Cell
Functions of the Sertoli Cells
1. nourish spermatocytes, spermatids, & sperm
2. phagocytoze excess spermatid cytoplasm as they develop into sperm
3. control movements of spermatogenic cells & release of sperm into lumen of seminiferous tubules
4. produce fluid for sperm transport5. secrete hormone inhibin6. mediate effects of T & FSH
Leydig Cells
interstitial cells (between seminiferous tubules)
*secrete T
Sperm
~300 million sperm complete spermatogenesis/d
~60 μm longonce ejaculated last ~48 hours w/in female
reproductive tract
Hormonal Control of the Testes
Ducts of the Male Reproductive System
fluid secreted by Sertoli cells generates pressure which pushes sperm & fluid along lumen of seminiferous tubule eventually released as ejaculate
Epididymis
epi = over or above / didymis = testisaka: ductus epididymisplural:epididymidescomma-shaped organlies along posterior border of each testis1. ductus epididymis2. head3. body4. tail
Ductus Epididymis
~6 m in lengthpseudostratified columnar epithelium lined with
microvilli called stereocilia increase surface area for reabsorbing
degenerated spermsurrounded by smooth muscleFunction of epididymis:
*sperm maturation (acquire motility & ability to fertilize an ovum)
smooth muscle contraction propels sperm into ductus deferens
sperm storage (viable up to several months)
Ductus Deferens/ Vas Deferens
ascends along posterior border of epididymis inguinal canal entering pelvic cavity loops over ureter passes down posterior surface of urinary bladder
terminal end is dilated = ampullapseudostratified columnar epithelium3 layers smooth muscle (inner & outer layers
longitudinal, middle layer circular)
Function of Vas Deferens
Function: 1. conveys sperm from epididymis urethra by
peristaltic contractions2. sperm storage (several months)
sperm not ejaculated are reabsorbed
Vasectomy
main method for sterilization of malesportion of each vas deferens is cut out & ends
ligatedsperm
production continues but do not reach exterior
degenerate & destroyed by phagocytes
Ejaculatory Ducts
formed by union of duct from seminal vesicle & ampulla of ductus deferens
pass inferiorly & anteriorly thru prostate gland
terminate in prostatic urethra where they eject sperm & seminal vesicle secretions just before the release of semen from urethra to exterior
Urethra
shared terminal duct of reproductive & urinary systems
passes thru: prostate deep muscles of perineum penis
Urethra
3 parts:1. Prostatic Urethra2. Membranous Urethra
portion thru deep perineal muscles3. Spongy (penile) Urethra
portion thru corpus spongiosum of penis ends at external urethral orifice
Parts of Male Urethra
Accessory Sex Glands
secrete most of liquid portion of semenInclude:1. Seminal Vesicles2. Prostate3. Bulbourethral Glands
Seminal Vesicles
aka seminal glandspaired, convoluted, pouchlike structuresposterior to base of urinary bladder (superior
surface) & anterior to rectum*secrete alkaline, viscous fluid: (~60% of vol
of semen) fructose prostaglandins clotting proteins (different from those in
blood)
Seminal Vesicles Fluid
alkaline to neutralize acidic environment of male urethra & female vagina (acids inactivate or kill sperm)
fructose:used for ATP production in spermprostaglandins contribute to sperm motility &
viabilityclotting proteins help semen clot after
ejaculation
Prostate
single, donut-shaped gland~size of a golf ballinferior to urinary bladdersurrounds prostatic urethraincreases in size from birth to puberty when
it expands rapidly until ~ age 30, remains stable ~ age 45, further enlargement may occur after that
Prostatic Fluid
milky, slightly acidic~25% of vol of semen empties urethra thru many prostatic ductscontains:1. citric acid (ATP production in sperm)2. several proteolytic enzymes
PSA: prostate-specific-antigen3. acid phosphatase (function unknown)4. seminalplasmin: bacteriocidal
Bulbourethral Glands
aka Cowper’s glandspea sized, inferior to prostate gland on either
side of membranous urethraducts open into spongy urethrasecrete 1. alkaline fluid (protects sperm from acidic
environment of spongy urethra)2. mucus lubricates end of penis & lining of
urethra (decreases # of sperm damaged during ejaculation)
Semen
mixture of sperm & seminal fluid
(secretions of seminiferous tubules, seminal vesicles, prostate, & Cowper’s glands)
average vol: 2.5 – 5 mL with 50 – 150 million sperm/mL
<20 million sperm per mL probably infertile pH: 7.2 – 7.7 provides sperm with:1. transportation medium2. nutrients3. protection from hostile acidic environment of
male urethra & female vagina
Penis
contains urethrapassageway for urine & semenParts:1. Body2. Glans Penis3. Root
Body of the Penis
Corpora Cavernosa: 2 dorsolateral
massesCorpus
Spongiosum: midventral mass spongy urethra
w/in
Circumcision
portion of prepuce (fore skin)surgical excised 3 – 4 days after delivery or 8th day for Jewish rite