346
UNIT 3
Organ Systems
1.
Ductus epididymis
: Each
ductus epididymis
is a highly
convoluted tube (about 6 m long) that has three regions:
head, body
, and
tail
(Figs. 18-16 to 18-17B). They are lined
by
pseudostratif ed columnar epithelium
with
long stereo-
cilia
that absorb large volumes of
testicular fl
uid from the
lumen and secrete a variety of substances, including
glycero-
phosphocholine
, which inhibits capacitation of spermatozoa
from occurring in the male reproductive tract. The tail of the
epididymis is the region where spermatozoa mature and are
stored.
2.
Ductus deferens
: Each
ductus deFerens
is a long tube that
courses partly within a spermatic cord. Its proximal end
connects with the tail of the epididymis. The distal portion
becomes enlarged and is known as the
ampulla
. After its
junction with the duct of the
seminal vesicle
, the
ductus
deFerens
continues its course to form the
ejaculatory duct
.
The ductus deferens is lined by
pseudostratif ed columnar
epithelium
and surrounded by a thick muscularis consisting
of three layers of smooth muscle (Fig. 18-18A–C).
3.
Ejaculatory
ducts
: The two
ejaculatory ducts
are surrounded
by the prostate gland (Fig. 18-19A,B). They are straight
tubes, lined by
pseudostratif ed columnar
and
simple
columnar epithelium
. The ejaculatory ducts open into the
prostatic urethra
at the
colliculus seminalis
. The colliculus
seminalis is a median elevation of the
verumontanum
, the
portion of the male prostatic urethra where the ducts open.
4.
Urethra
: The
urethra
is a long tube (about 20 cm) lined by
various types of
epithelium
. It is a common passage shared by
the urinary system and reproductive system in the male. It can
be divided into three regions: the
prostatic
, the
membranous
,
and the
spongy (penile) urethra
. The
prostatic urethra
, lined
by
transitional epithelium
, is connected with the bladder at
its proximal end and passes through the prostate gland. The
prostatic urethra is wider than other parts of the urethra and
has two ejaculatory ducts opening into the urethra. The short
membranous urethra
is lined by pseudostrati± ed columnar
epithelium; it is the intermediate and narrowest part of the
urethra. The membranous urethra connects the prostatic
urethra to the spongy urethra. The
spongy urethra
, also called
the
penile urethra
, is lined by strati± ed columnar epithelium.
It passes through the penis and is the longest segment of the
urethra (Fig. 18-22).
Accessory Genital Glands
The
accessory genital glands
are exocrine glands that include
the
prostate gland
, paired
seminal vesicles
, and
bulbourethral
glands
. (1) The
prostate gland
is a collection of about 40 small
tubuloalveolar glands lined by
simple columnar epithelium
and
supported by a connective tissue stroma.
Prostatic secretions
contain
proteolytic enzymes, acid phosphatase, citric acid,
f brinolysin
, and
lipids
(Fig. 18-20A,B). (2) Each
seminal
vesicle
has a single convoluted tube with a branched and folded
mucosa lined by
pseudostratif
ed columnar epithelium
. The
epithelium is supported by a thin connective tissue layer that
is surrounded by two layers of smooth muscle (
muscularis
).
The seminal vesicle produces seminal fl
uid containing
Fructose
,
prostaglandins
,
fl avins
,
phosphorylcholine
,
vitamin C
, and
proteins
(Fig. 18-21A–C).
Semen
is a mixture of seminal fl
uid,
prostatic secretion, spermatozoa, and testicular fl
uid. (3) The
bulbourethral glands
are a small pair of glands lined by
simple
columnar epithelium
. They produce
preejaculate
(
preseminal
)
fl uid that lubricates the urethra before ejaculation.
Penis
The
penis
is an external genital organ that consists of three
cylinders of
erectile tissue
, including the
corpora cavernosa
(two) and the
corpus spongiosum
(one). The corpus spongiosum
contains the urethra in its center. The penis has a unique blood
supply (dorsal arteries, deep arteries, and helicine arteries)
and drainage (super±
cial veins, arteriovenous shunts) that are
correlated with its erection (Fig. 18-22).
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