C T -S :

CHAPTER TWENTY-SEVEN: MALE REPRODUCTION
The organs of the male reproductive tract can be categorized by function. In addition to serving in
a reproductive capacity, several of the male reproductive structures serve a urinary system function.
testes
ducts
accessory sex glands
The male gonads, testes, are stored in a
protective sac called the scrotum. The
scrotum is divided into two isolated
compartments by a strip of fibrous
connective tissue called the scrotal septum.
<
scrotal septum
<
scrotal raphe
<
unequal suspension
<
cremaster muscle (skeletal muscle)
<
dartos muscle (smooth muscle)
<
spermatic cord: blood vessels,
nerves, lymphatic vessels, vas
deferens, cremaster muscle
<
testicular arteries
<
testicular veins a.k.a. pampiniform
plexus
•
blood flow from testicles
•
increased surface area for
trapping heat & moving it
away from testes
What are the functions of the scrotum?
<
testicular support
<
testicular protection
<
temperature regulation
<
sexual experience . . . nerves
How do the testicles arrive at/into the scrotum?
<
inguinal canal
<
gubernaculum . . . testes to scrotal floor . . . “pull”
<
descent at 7th month of development
•
descent failure termed cryptorchidism
- increased risk of testicular cancer
- increased risk of sterility
-1-
The testicles are covered by several layers of protective connective
tissue.
<
tunica vaginalis- double layered serous membrane
<
tunica albuginea -subdivisions into septum/lobules in the
testes
The tunica albuginea invaginates to form a series of lobules which
make up the testicle. Housed within each lobule is a series of
“coiled” tubes called seminiferous tubules.
Between the seminiferous tubules are cells called interstitial
endocrinocytes or Leydig cells.
What are the functions of the testicles?
<
production of sperm
<
production of testosterone
<
production of a contribution of fluid to semen
<
regulates secondary sex characteristics
The walls of the seminiferous tubules
are a collection of several types of
cells. Functionally, these cells can be
divided into those which create sperm
and others which “support or nourish”
the developing sperm.
Cells which develop into sperm are
termed spermatogenic cells. There
are specific names for each cell as it
passes through sperm development spermatogenesis. Completion of
spermatogenesis takes approximately
65 days.
<
spermatogonia ( 46 Ch)
<
1°spermatocyte (46 Ch)
<
2°spermatocyte (23 Ch)
<
spermatids (23Ch)
<
“spermiogenesis”
<
sperm (23 Ch) a.k.a.
spermatozoa
The onset of spermatogenesis is
puberty. Each day a normal male
produces 400 million sperm.
Let’s add some new terminology to the chromosome numbers and type of spermatogonia cells present at each
phase of spermatogenesis.
<
diploid (2N)
<
haploid (1N)
<
type A daughter cell
<
type B daughter cell
-2-
Sperm are streamlined versions of spermatids. The loss of the spermatid cytoplasm creates a “sperm.”
<
head w/acrosome
hyaluronidase
proteinase
<
midpiece
ATP
<
flagellum
Cells which are located in between
spermatogenic cells are the sustentacular
cells or Sertoli cells.
<
tight junctions
<
blood-testis barrier . . . “self” issues
What are the functions of the Sertoli cells?
<
protection
<
nourish via blood -testis barrier
<
phagocytosis of spermatid cytoplasm
<
<
<
control spermatogenic cell
progression from periphery to lumen
contribute fluid to semen
secretes inhibin which alters the
release of FSH from the anterior
pituitary gland
-3-
The areas surrounding the seminiferous tubules are filled with interstitial cells a.k.a leydig cells or interstitial
endocrinocytes.
What are the functions of the interstitial cells?
<
support seminiferous tubules
<
respond to LH stimulation
<
testosterone production in response to LH
How does hormonal regulation of male reproductive
system operate?
<
hypothalamus
GnRH
<
anterior pituitary
FSH: spermatogenic, sertoli cells
LH: interstitial cells
<
interstitial cells
testosterone: spermatogenic cell
<
sertoli cells
androgen-binding protein (ABP):
spermatogenic cells
inhibin: anterior pituitary gland
FSH stimulates spermatogenesis and ABP
production. ABP binds testosterone at discrete sites
in the testes - seminiferous tubule lumen & interstitial
fluid.
LH (a.k.a. interstitial cell-stimulating hormone
ICSH) stimulates interstitial cell production of
testosterone from cholesterol.
Testosterone stimulates spermatogenesis and ABP
production. ABP binds testosterone at discrete sites in the testes - seminiferous tubule lumen & interstitial
fluid. ABP is working in positive feedback.
Inhibin is produced by the Sertoli cells. It decreases the production of FSH and LH from the anterior
pituitary. Inhibin is working in a negative feedback.
-4-
What are somatic effects of testosterone?
What are the somatic effects of dihydrotestosterone
(DHT)?
Some cells will not respond to
testosterone, however, they will respond to a
modified form - DHT. For example, the prostate
gland responds to DHT not testosterone.
NOTE
In some neurons of the brain, testosterone is
converted into estrogen in order to carry out “brain
masculinization”.
TESTICULAR DESCENT
GENITAL ENLARGEMENT AT PUBERTY
INCREASED SEBACEOUS GLAND PRODUCTION AT
PUBERTY
LARYNX ENLARGEMENT
CHARACTERISTIC SKELETAL MUSCLE DEPOSITION
CHARACTERISTIC HAIR DEPOSITION
SEXUAL BEHAVIOR
LIBIDO
EPIPHYSEAL PLATE CLOSURE
EXTERNAL GENITAL DEVELOPMENT
GENITAL ENLARGEMENT AT PUBERTY
INCREASED SEBACEOUS GLAND PRODUCTION AT
PUBERTY
LARYNX ENLARGEMENT
CHARACTERISTIC SKELETAL MUSCLE DEPOSITION
CHARACTERISTIC HAIR DEPOSITION
SEXUAL BEHAVIOR
LIBIDO
EPIPHYSEAL PLATE CLOSURE
ANABOLIC METABOLISM
The contents of the testes are collected into a
“collection” organ - epididymus. The epididymus sits
atop the testes with the head being most superior and the
tail most inferior, in orientation.
<
head
efferent ducts
<
body
ductus epididymus
<
tail
ductus epididymus
The epididymus consists of pseudostratified ciliated
columnar epithelium with sterocilia and a band of
smooth muscle called the dartos muscle.
-5-
What are the functions of the epididymus?
<
stores sperm
<
provides swimming instructions to sperm
<
propels sperm during coitus
<
reabsorbs old sperm
The vas deferens (a.k.a. ductus deferens) in the long tube which transports stored sperm from the epididymus
to outside of the body via the urethra. Its passage begins external to the pelvic cavity, proceeding internally
into the pelvis where it joins the urethra at the level of the prostate gland. Remember that the vas deferens
enters the pelvic cavity through the inguinal canal as part of the spermatic cord.
<
ampulla of vas deferens
<
seminal vesicles (x2)
60% semen volume
yellowish viscous fluid
<
<
alkaline contribution to semen
fructose contribution to semen
ascorbic acid contribution to semen
vesiculase (a.k.a. semenogelin) for coagulation
contribution of semen
prostaglandins for sperm motility
prostaglandins for sperm viability
prostaglandins for vaginal and uterine contractions
seminal vesicle ducts (x2)
ejaculatory duct (x2)
site of sperm and semen mixing
propel semen into the prostatic urethra
The prostatic urethra is the first region of the
urethra where it passes from the urinary
bladder through the middle of the prostate
gland.
<
prostatic urethra: prostate gland
<
membranous urethra: urogenital
diaphragm
<
penile (spongy) urethra: penis
<
external urethral orifice
-6-
Along the length of the urethra, various
accessory organs provide “input” into the
contents of the urethra during ejaculation.
<
ejaculatory ducts (x2)
<
prostate gland (x1)
•
connective tissue capsule
•
fibromuscular stroma w/
smooth muscle
•
tubular-alveolar glands
The prostate gland serves the following
functions.
<
provides 33% of seminal fluid
contributions
<
milky contribution
<
provide citrate for conversion to
ATP during the Kreb’s cycle
<
provides substances which enhance
sperm motility
<
provides a gel-liquid transition
medium
<
provides an assortment of proteases
involved in the liquid transition
•
fibrinolysin
•
hyaluronidase
•
acid phosphatase
<
prostate-specific antigen (PSA)
The two bulbourethral (a.k.a. Cowper’s
glands) are located w/in the urogenital
diaphragm. The ducts of the bulbourethral
glands empty their contents into the spongy
urethra. The functions of these glands
include
<
small contribution to semen
<
contribute a thick, clear mucus
<
provides mucus to coat the urethra
prior to ejaculation
<
provides alkaline mucus to reduce
the acidity of urethral lumen created
by presence of residual urine
-7-
The penis (Latin for “tail”) is subdivided into three regions - root, shaft/body and glans penis. While
the length of the penis contains “cores” of
tissue, the arrangement of these cores differs
w/in each region of the penis.
The two “cores” of erectile tissue are termed
corpus spongiosum and corpora cavernosa.
<
dense connective tissue sheath
<
corupus spongiosum (x1) w/ spongy
urethra
<
copora cavernosa (x2) each w/ a deep
arteries
<
dorsal blood vessels
<
dorsal nerves
The regions of the two corpora cavernosa varies
as these erectile tissues progress proximal to
distal.
<
crus (“winged”) region at the root of the
penis - proximally
<
consistent diameter passing through the
shaft of the penis
The corpus spongiosum varies as this erectile
tissue progress proximal to distal.
<
consistent diameter passing through the
root and shaft of the penis
<
enlarged regions, corona & glans
penis, at the distal end of the penis
-8-
SEMEN
How does semen differ from sperm and seminal fluid?
What is the final pH of semen? 7.2 -7.6
What is the role of the chemical, seminalplasmin, found in semen?
What is the final semen volume? 2-5 ml
What is the sperm count? 50 -130 million sperm
MALE SEXUAL RESPONSE
This is a two part response.
<
erection
•
stimulation triggers the parasympathetic reflex
•
release of nitric oxide (NO) locally
•
vasodilation of deep arteries of corpora cavernosa
•
swelling of the corpora cavernosa lead to stiffening of the penis
<
ejaculation
•
peaked stimulation of the spinal reflex at L1 and L2 triggers sympathetic response
•
reproductive glands propel at speed of 200 inches/second
at same time
•
bladder sphincter muscle contract preventing urine from leaving the bladder
RECENT ISSUES
<
decrease sperm production
•
hydrocarbons
•
estrogenic chemicals
•
clothing choices
•
antibiotics i.e. TCN
<
abnormal sperm production
•
radiation
•
lead exposure
•
pesticide exposure
•
lack of selenium
•
marijuana
•
alcoholism
<
erectile dysfunction . . . low levels of nitric oxide
•
causes
medication usage: BP, antihistamines (Tagamet), antidepressants (i.e. Prosac)
diseases: diabetes mellitus, arteriosclerosis, varicose veins
trauma
cancer
•
sidenafil (Viagra)
MOA: increases NO levels
side effects: blue/green vision, stuffy nose, death
usage in women?
-9-
HOMEOSTATIC IMBALANCES
Cause
benign prostatic
hyperplasia
enlarged prostate gland
treatments: medications
cryptoorchidism
undescending testes
hypospadiasis
abnormal urethral opening
impotence
failure to achieve erection
inguinal hernia
gut bulges into the inguinal canal
prostate cancer
tumor within the prostate gland
treatments: medications, surgery, radiation
prostatitis
inflammation of the prostate gland
testicular cancer
rare, young males w/ hx of orchitis, 90% cure rate with testicle
remoal
MEDICAL PROCEDURES
Procedure
Details
castration
removal of testicles
circumcision
removal of prepuce
orchitis
testicular lumps “mumps”
orchiectomy
removal of a testicle
vasectomy
vas deferens is severed
October 17, 2006 (11:12am)
C:\MyFiles\LCCC\a&p hybrid\lecture_f\ap.lec_malerepro.wpd
-10-
`