Male Reproductive System

1
Male Reproductive System
LEARNING OBJECTIVES To learn the nomenclature
and structures of the male reproductive system.
To understand the functions of these structures
and how they are interrelated to prove the
complete reproductive process in the male.
2
Reproductive Organs in the Male
Cowpers Gland
Rectum
Crura (pl)
Prostate
Seminal Vesicles
Ampulla
Bladder
Retractor Penis Muscle
Sigmoid Flexure
Retractor Penis Muscle
Vas Deferens
Caput Epididymis
Scrotum
Glans Penis
Cauda Epididymis
Testis
3
Overall functions of the male Produce and
maintain supply of sperm Detect females in
estrus Inseminate females and fertilize
the female gamete
Termed - Spermatogenesis
Using - Pheromones, Visual Cues
4
Structure of the Testis
Spermatic Cord - contains vas deferens,
pampiniform plexus, external cremaster
muscle nerves
Function in maturation of spermatozoa,
fluid absorption
Transport of sperm during ejaculation
Caput Epididymis
Vas Deferens
Efferent ductules - 6-12 tubles absorb fluids.
Seminiferous Tubule
Sperm producing cells - true germinal epithelium
Tunica Albuginea
- connective tissue which holds testis together
Maturation of spermatozoa
Corpus Epididymis
Final maturation and storage. Only sperm capable
of fertilization
Rete Testis
Function in sperm transport from
seminiferous tubules - 100 tubules
Cauda Epididymis
5
Spermatogonium Primary Spermatocyte Secondary
Spermatocyte Spermatids
Increasing maturity
Peristaltic-like contractions move sperm through
tubule
Primary Spermatocyte
Sertoli Cells
Myoid Cells
Support Spermatogenesis
Secondary Spermatocyte
Leydig Cells
Round Spermatids
Spermatids
Basement Membrane
Testosterone synthesis
Capillary
6
Functions of the testis 1. Produce Sperm
2.Transport sperm out of testis
3.Produce testosterone
Testosterone function
Spermatogonia
- Termed Spermatogenesis
Spermatid
Sertoli cells are involved with control of
development
Spermatozoa
- Not transported by sperm motility
1. Testis capsule - tunica albuginea - causes
pressure with some smooth muscle
contraction. 2. Seminiferous tubules - Myoid
cells contract to move spermatozoa 3. Efferent
ductules and Caput - water absorption causing the
sperm to be drawn towards the epididymis
- Leydig cells stimulated by Luteinizing
Hormone (LH) from anterior pituitary
1. Stimulates secondary sex characteristics
Muscle development, Accessory glands 2.
Maintains Libido 3. Maintain function of male
reproductive tract Penis and muscles for
ejaculation
7
Thermoregulation of the Testis Temperatures
3-5C less than body temperature are required for
Spermatogenesis to occur. One major factor is the
Scrotum Scrotal Properties that facilitate
thermoregulation 1.Location of Testis
2.Low insulation 3.Sweat gland
4.Tunica Dartos Change in testis
location Change in scrotal surface
area 5.External Cremaster Muscle
6.Thermoreceptors
- Outside away from body - air circulation
- Thin skin, low subcutaneous fat or hair
- Richly endowed - Evaporative cooling
- Smooth muscle which lines scrotal wall
- Vary closeness to body wall
- Vary thickness
- Relax when hot Contract when cold
Skeletal muscle - Striated
- Nerves in scrotum control response to
temperature of testis
8
2nd Major Factor - Blood supply to testis.
Pampiniform Plexus
1. Pampiniform Plexus Counter-current heat
exchange causes a cooling of arterial blood
supply Single artery surrounded by a
network of veins (Increased surface area)

Testicular Artery
2. Convoluted testicular artery on the
surface of the testis In Ram
temperature decrease 40C before
entering testis
Scrotum, testis and spermatic cord are all
involved in thermoregulation
9
Vascular Supply to Testis
Artery
Pampiniform Plexus
Veins
Testicular Artery
10
Cryptorchidism - Lack of testis descent into
scrotum and thus
thermoregulation is absent Bilateral - Is
sterile Unilateral - Is fertile -
Common in boars and stallions
No spermatogenesis Testosterone is produced
Reduce sperm producing capacity
Testis descent occurs late
Time of Testicular Descent Gestation
Length Bull 100-105 Days
280 Days Boar 100-110 Days
114 Days Stallion 300
Days 340 Days
Stallion testes should be down within 16
months Some may take two years. Testes are below
the inguinal ring after birth however.
11
Functions of the Epididymis 1.Transport of
sperm - 9-11 days in bull
Mechanisms Pressure of new sperm Regular
contraction of smooth muscle Stimulated
contractions of cauda
- transport from caput to cauda
- Sperm moving into caput from efferent
ductules. Pressure gradient formed
which surrounds the duct
Peristaltic-like contractions (every 6 sec) in
caput and corpus are independent of sexual
activity
Increased contractions stimulated by sexual
activity may reduce transport time in cauda itself
12
2. Concentration of sperm Mechanism
Fluid absorbed in Caput
- Fluid absorbed by efferent ductules.
Concentration doesnt change much after
proximal caput
- Contains tall columnar epithelium with
Sterocilia
Sterocilia absorb fluid to concentrate sperm
Rete contains 1X108 sperm/ml - cauda 7X109
sperm/ml Ram - 40 ml of fluid/day comes from
testis and reduced to 1ml
13
3. Maturation of sperm in Caput to Corpus region
1. Sperm gain ability to be motile and
fertilize the oocyte 2. Involves
biochemical and physical changes to sperm 3.
Controlled by rate of transport through
epididymis and epididymal secretions
4.Epididymal fluid changes
Publication permission granted by Dr. Richard J.
Blandau Taken from original films by the
University of Washington School of Medicine Sperm
maturation in the Male Reproductive Tract -
Development of Motility)
Covered by forward motility factor
Allows time for maturation to occur
Secretions are different in the various segments
of epididymis. Utilized to stimulate maturation
and motility
14
Examples of changes sperm undergo 1.
Increase in specific gravity 2. Nucleus more
condensed and stable 3. Increase (-)
charge on plasma membrane 4. Sperm
become less resistant to cold shock
5. Migration of cytoplasmic droplet
Changes necessary for fertilization to occur
Sperm lose H2O - become more dense

DNA in nucleus is inactive and held together by
disulfide bonding
Aid in fertilization? Covered with a
carbohydrate to bind to ovum
Rapid change in temperature damages sperm.
Membrane is fragile.
15
4. Storage of sperm - Cauda 1. 70 of sperm
in cauda 2. Four days of testicular
sperm produce is stored 3. Can be stored
for several weeks
Only approximately 1/2 sperm produced make it to
this point
Major site of sperm numbers in excurrent (outside
testis) ducts. 2 in vas deferens
Stored without loss of function - Arrests sperm
metabolism - sperm dont burnout Allows for
repetitive ejaculations of a short period Sperm
are indefinitely viable as prolonged sexual rest
results in the first couple of collections
showing poor sperm quality
16
Factors conducive to storage 1. Reduced
pH 2. Low O2 High CO2 3. High KNa ratio
4. Low concentrations of energy substrates
Present in Cauda Epididymal Fluid
pH in cauda is approximately 5.8
Slows oxidative metabolism
Opposite of extracellular fluid surrounding
normal cells of body
Slow metabolism
17
Other factors related to epididymal function
1. Temperature 2. Testicular androgens
3. Ejaculation frequency
Cooler (3-50C) than body temperature High
temperature interferes with spermatogenesis not
storage
Vital to epididymal function by maintaining
secretory activity Androgen binding protein
produced by sertoli cells keeps levels of
testosterone high in epididymis
Bull studs collect 2X / collection and usually
collect 2X / week or 3X / week depending on bull
18
Sperm Numbers in Region of the Male Tract (X109)
Sexually
Depleted Bull
Rested Bull 20 ejaculates 6
collections
in 5 hours per week Caput
19.4 16.2
22.6 Corpus 4.7
3.0
5.2 Cauda 37.6
13.7 26.2 Vas deferens
7.9 2.1
3.3 Ampulla
High ejaculation frequency the of immature
sperm in ejaculate do not increase
significantly. However the number decreases
19
Fate of unejaculated sperm ½ of produced
sperm not available for ejaculation 1.
Resorbed by excurrent duct system 2.
Sperm lost in urine
Masturbation loss of sperm
Epididymis, vas deferens and ampulla
Some selective removal of abnormal sperm in
epididymis (macrophages)
87 of daily sperm from epididymis of inactive
ram are found in urine
Management problem in Boars and sometimes
Stallions
20
Functions of vas deferens and ampulla for
transport of sperm 1. Low level steady-state
contractions of vas deferens 2. Increased
contractions caused by sexual excitement
Thick muscular wall This occurs in non-excited
state
Strong peristaltic contractions of smooth
muscle stimulated by nerves during sexual arousal
21
3. Sperm stored in ampulla age rapidly
Why? Increased temperature
Poorer environment for sperm
Bull, Stallion and Ram
No secretions produced like the cauda,
therefore increase in metabolic activity Male not
used for a period of time may have poor quality
sperm the first few ejaculates collected
22
Functions of seminal plasma 1. Transport
media 2. Culture media 3. Stimulates
sperm motility 4. Retards sperm
capacitation 5. Stimulates sperm transport
in female -
Gives fluid volume to sperm, helps move sperm
through the urethra. In sow volume is very
important for fertility
Proper environment for sperm viability and
motility in the female reproductive tract. Cow
the vagina is a hostile environment
Biochemical stimulation - cauda sperm were
quiescent. Seminal plasma activates metabolic
activity
Prevents sperm from events for immediate
fertilization. Why? Dont want them to activate
until they reach site of fertilization.
Secretions in cervix, uterus and oviduct
remove coating on sperm so they can fertilize
Uterine muscle contractions
Oxytocin and Prostaglandin F2a are in seminal
plasma
23
Sources of seminal plasma 1. 2. 3.
4. 5. 6. 7.
Testis Epididymis Vas deferens Ampulla
Minor Contribution
Secretory Gands
Seminal Vesicles Prostate Cowpers
(Bulbourethral)
Major Contribution
24
Chemical composition of seminal plasma
Nutrients 1. Fructose 2. Sorbital
3. Glycerol Phosphorylcholine 4.
Lactic Acid 5. Fatty Acids 6. Amino
Acids
Energy Source
- Major secretion in bull seminal vesicles (10X
glucose in blood) Not much in other species
Alcohol Sugar
Origin epididymis
May function in survival of sperm in epididymis
Anerobic - metabolic product
Energy
Energy
25
Buffers 1. Bicarbonate 2.
Citrate Other Components 1.
Ergothioneine 2. Cysteine 3.
Glutathione Function to protect sperm
Sperm produce H202 AA-SH
HS-AA H202 -gt -S-S- 2H20
- Control pH from rapid changes Cauda pH 5.8 to
seminal plasma pH 6.8
HCO3-
- Not a great contribution in seminal plasma
Use in AI extenders
- High amounts in stallion ampulla
All have Sulfide bonds
- in bull semen
- Act as antibacterial agents
(Peroxide)
Enzyme-Peroxidase
26
- F2a Stimulate muscle contractions
4. Prostaglandins 5.
Glycoproteins Sperm
Sperm decapacitation 6. Enzymes
7. Ions Na K Zn Ca Mg
Stimulation of sperm metabolism
i.e.
- Epididymis
Maturation - caput to cauda
- Coat sperm to retard capacitation Female
tract removes coat to allow fertilization
at AIJ
Activate various processes
-opposite epididymis
Na
K
27
Semen and ejaculation characteristics of
farm species
Cattle
Dairy Beef Sheep Swine
Horses Volume 6 4
1-2 225-400 60-100 Sperm conc 1.2
1.0 3.0 0.2
0.15 Billion/ml Total sperm 7
4 3 45 9
Billion Motile sperm 70 65 75
60 70 Morphology normal
80 80 90 60
70 pH 6.5-7.0 6.5-7.0
5.9-7.3 6.8-7.3 6.2-7.8
Volume and sperm concentration are inversely
related. Total sperm related to total volume
28
Bull (Ram) Not fractionated Pre-ejaculation
dribble - cowpers Ejaculate - Seminal vesicles
Prostate Stallion Fractionated Presperm
- Urethral glands Cowpers? Sperm rich -
Epididymal Ampulla, Prostate Postsperm -
Gel from Seminal Vesicles Penile Drip -
Prostate and Cowpers
- Species ejaculate in a fraction of a second
- Ejaculate mixed together (Sperm accessory

Fluid)
- Clear fluid - Cleans out the urethra before
mounting
Alkaline Fluid
Major Minor
- Ejaculation takes 30-45 seconds Can copulate
without ejaculation
Low sperm numbers
High sperm numbers
After ejaculation there is some drainage to clean
urethra
29
Boar Fractionated Presperm -
Prostate Sperm Rich - Seminal vesicles
Prostate Postsperm - Gel -
Cowpers gland
Ejaculate over 3-10 minutes - Has no ampulla
- Clear fluid
Very high sperm concentration
Small gel plugs which adhere together in
the cervix to block semen backflow into vagina
30
Cowpers Gland and Pelvic Muscles
Pelvic Urethral Muscle
Bulbo-cavernosus Muscle
Cowpers Glands
Ischiocavernosus Muscle
Retractor Penis Muscle
Sigmoid Flexure
31
Gel within Cowpers Gland
Gel Plug
Cowpers Gland
Pelvic Urethra