Abnormal Spermatogenesis and Male Fertility

GUYTON 81: Reproductive and Hormonal Functions of the Male (and Function of the Pineal Gland)
Abnormal Spermatogenesis and Male Fertility
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Destruction of seminiferous tubular epithelium by several diseases
Mumps  orchitis
Structures in genital ducts  degenerate tubular epithelia
Excessive temp of testes

Effect of Temperature on Spermatogenesis
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Prevent spermatogenesis and degeneration of most cells of the seminiferous tubules
Scrotum maintains temp of the testes ~ 2oc below internal temp
Cold days  scrotal reflex  scrotal musculature e contract  close to the body 

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maintain 2o deferential
Scrotum acts as cooling mechanism

Cryptorchidism
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Undescended testis/es  remains in abd, inguinal canal or else where
~ 3 wks to 1 mo before birth  scrotum
Stimulated by endogenous testosterone secretion
Incapable of forming sperm
Temp in abd (rising even slight)  tubular epithelium  degenerate interstitial

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structures remain
surgery is a must before adult sexual life
if testes is not able to secrete own testosterone to promote descent  surgery is unlikely

MALE SEXUAL ACT
Neuronal Stimulus for Performance of the Male Sexual Act
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Glans penis – most impt source of sensory nerve signal that initiate male sexual act
Sexual sensation  Slippery massaging action of intercourse  glans penis  Pudendal

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nerve  Sacral segment of SC  Brain
o Adjacent areas:
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Anal epithelium
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Scrotum
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Perineal structure
o Internal structures:
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Urethra
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Bladder
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Prostrate
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Seminal vesicles
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Testes
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Vas deferens
One of the causes of “sexual drive” is filling of the sexual organs with secretions
Mild infection and inflammation of these sexual organs may sometimes stimulate sexual

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desire
Aphrodisiac drugs, such as cantharidin, irritate the bladder and urethral mucosa, inducing

to be successful
Effect of Sperm Count on Fertility
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Semen: 3.5 mL; 120M sperm/ mL
o Variation: 35M to 200M sperm/ mL
o Average: 400 M sperm/ mL
Below  infertile

inflammation and vascular congestion.
Effect of Sperm Morphology and Motility on Fertility
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Infertility in Normal sperm count
o abnormal morphology
o nonmotile or relatively nonmotile

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Psychic Element of Male Sexual Stimulation
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Enhance the ability of a person to perform the sexual act
thoughts or dreaming of intercourse initiate the male sexual act  ejaculation
nocturnal emissions esp in teens

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GUYTON 81: Reproductive and Hormonal Functions of the Male (and Function of the Pineal Gland)
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can inhibit or initiate male sexual act

Dilation of large cavernous sinusoids of the erectile tissue
Integration of the Male Sexual Act in the Spinal Cord

Surrounded by strong fibrous coats
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Ejaculation still possible even SC is cut in lumbar segment
male sexual act results from inherent reflex mechanisms integrated in the sacral and

 pressure
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lumbar spinal cord
Initiators:
o Psychic stimulation (brain)
o Sexual stimulation (sexual orgrans)
o Usually both

Ballooning of erectile tissue
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Penis: hard and elongated
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Erection

STAGES OF THE MALE SEXUAL ACT
Penile Erection—Role of the Parasympathetic Nerves
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First effect of male sexual stimulation
Degree of erection is proportional to degree of stimulation
Parasympa  sacral SC  pelvic nerves  penis
Parasympa  NO and / or vasoactive intestinal peptides

Lubrication Is a Parasympathetic Function
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Urethral glands and the bulbourethral glands  mucus  urethra
Aid in lubrication during coitus
Most of the lubrication of coitus is provided by the female sexual organs
Unlubricated intercourse  grating, painful sensations  inhibit MSA

NO
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Guanosyl cyclase
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cGMP
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Arteriolar relaxation and SM relaxation
(corpora cavernosa & corpus spongiosum)
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Emission and Ejaculation Are Functions of the Sympathetic Nerves
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Culmination
Intense sexual stimulus  SC reflex center  sympa impulse  T12-L2  hyogastric

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& pelvic sympa nerve plexus  genitals  emission
Emission is the forerunner of ejaculation
o Contraction of vas deferens & ampulla  expulsion of sperm to internal

 blood flow to relaxed SM
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Further  in NO
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Blood flows rapidly while venous outflow is partially occluded
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urethra
Contraction of prostate gland  contraction of seminal vesicle  expel

prostatic & seminal fld  urethra
o Mixed w/ mucus from bulbourethral glands
Filling of internal urethra w/ semen  sensory signal  pudendal nerve  Sacral SC 
sensation of sudden fullness in internal genital organ

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GUYTON 81: Reproductive and Hormonal Functions of the Male (and Function of the Pineal Gland)
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Filling of internal urethra w/ semen  sensory signal  excite rhythmical contraction of
ischiocavernosus & bulbocavernosus  compress base of penis

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Both increases in pressure in both the erectile tissue of the penis and the genital ducts and
urethra, which “ejaculate” the semen from the urethra to the exterior  Ejaculation

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Rhythmical contractions of the pelvic muscles and even of some of the muscles of the
body trunk cause thrusting movements of the pelvis and penis, which also help propel the
semen into the deepest recesses of the vagina and perhaps even slightly into the cervix of
the uterus.

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This entire period of emission and ejaculation  Male orgasm
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Termination: 1 to 2 misn  erection ceases resolution

TESTOSTERONE AND OTHER MALE SEX HORMONES
SECRETION, METABOLISM, AND CHEMISTRY OF THE MALE SEX HORMONE
Secretion of Testosterone by the Interstitial Cells of Leydig in the Testes
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Androgens: testosterone, dihydrotestosterone, and androstenedione.

Secretion of Androgens Elsewhere in the Body
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Androgen – any hormone w/ masculinizing effects

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Adrenal glands - < 5% only in male adult even in women except for growth of pubic and
axillary hair

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Androgen producing cells  virilism

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Ovary  embryonic crest cells  arrhenoblastoma  androgen secreting tumor

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Ovary also secrete small amt of androgens but not significant

Testosterone
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much more abundant

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primary testicular hormone

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much testosterone  dihydrotestosterone

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Interstitial cells of Leydig  interstices between the seminiferous tubules
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20% of mass of human adult testes

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Almost nonexistent in pedia

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Most numerous in newborn make for first few months and after puberty when

Chemistry of the Androgens
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Steroid compounds

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Can be synthesized from cholesterol or acetyl coenzyme A

there is increase testosterone production
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Tumors  increase testosterone production

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Testicular germinal epithelium is destroyed by Xray or excessive heat but
Leydig cells are less easily destroyed
Metabolism of Testosterone
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3% free

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GUYTON 81: Reproductive and Hormonal Functions of the Male (and Function of the Pineal Gland)
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97% - bounded w/ plasma CHON

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Fetal life  placenta  chorionic gonadotropin  testes  moderate testosterone
production up to 10 wks or more after birth

o

Loose – albumin

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Thight – B-globulin  Sex hormone binding globulin

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No production up until puberty (10-13 y/o)

o

Circulates for 30 mins  then goes  tissues / degraded  excreted

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Increase production from stimulus from adenohypophysis at onset of puberty and last
most of the remainder of life

Testosterone  tissues  dihydrotestosterone  esp in prostate and ext genitals
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Dwindling rapidly beyond 50y/o to become 20-50 % of peak value by 80 y/o

Degradation and Excretion of Testosterone
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Testosterone  not fixed to tissues  converted  androsterone and

Functions of Testosterone During Fetal Development

dehydroepiandrosterone  conjugated  glucorodines (most) or sulfates  Bile to GIT

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Elaboration ~7th wk of embryonic life

or Kidney to Urine

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male chromosome  sex-determining region Y (SRY) gene  testis determining factor
(SRY protein)  gene activations  differentiation of genital ridge cells  production

Production of Estrogen in the Male
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1/5 amt in the nonpregnant female

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Reasonable amt is seen in urine

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Key points

of testosterone  ridge becomes testes
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in female ridge differentiates to estrogen secreting cells

Development of the male body characteristics
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penis

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scrotum

1. The concentration of estrogens in the fluid of the seminiferous tubules is quite high
and probably plays an important role in spermiogenesis. This estrogen is believed

Effect of Testosterone to Cause Descent of the Testes

to be formed by the Sertoli cells by converting testosterone to estradiol.

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2. Much larger amounts of estrogens are formed from testosterone and androstanediol
in other tissues of the body, especially the liver, probably accounting for as much as

testosterone
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80 percent of the total male estrogen production.

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pedia w/ undescended but normal tetses  inject testosterone  cause testes to descend
normally

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FUNCTIONS OF TESTOSTERONE

Descent during last 2-3 mos of gestation when testes secrete reasonable amt of

administration of gonadotrophic hormones  stimulate Leydig cells  testosterone 
descent of testes

General: Musculinization

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