The superior half of the anal canal contains mucous membrane that is characterized
by a series of longitudinal ridges called anal
columns. These columns contain the terminal
branches of the superior rectal artery and vein

The pudendal nerve supplies most of the
innervation to the perineum. Toward the distal
end of the pudendal canal, the pudendal nerve
splits, giving rise to the perineal nerves and
continuing as the dorsal nerve of the penis or
clitoris

The rectosigmoid junction lies anterior to
the S3 vertebra

A transverse line joining the anterior ends
of the ischial tuberosities divides the perineum
into two triangles. The anal triangle, containing
the anus, is posterior to this line. The urogenital triangle, containing the root of the scrotum and penis in males and the external genitalia in females is anterior to this line

Parasympathetic stimulation in the female
produces an increase in vaginal secretions, erection of the clitoris, and engorgement of erectile
tissue in the bulbs of the vestibule

The pudendal canal is a space within the
obturator fascia, which covers the medial aspect
of the obturator internus and lines the lateral
wall of the ischioanal fossa

The posterior fornix is the deepest part of
the vagina and is closely related to the rectouterine pouch. The vaginal fornix is the recess around the cervix and is described as having
anterior, posterior, and lateral parts

The following structures are found in the
superficial perineal space: the root of the penis
and its associated muscles, the ischiocavernous
and bulbospongiosus. The proximal part of
the spongy urethra, superficial transverse perineal muscles, internal pudendal vessels, and
branches of the pudendal nerve are also located
in the superficial perineal space

The rounded vaginal part of the cervix extends into the vagina and communicates with it
through the external os. The cervical canal is
broadest at its middle part and communicates
with the uterine cavity through the internal
os and with the vagina through the external
os

The vestibule is the space between the labia
minora containing the openings of the urethra,
vagina, and ducts of the greater and lesser
vestibular glands. The greater vestibular glands
are round or oval and are partly overlapped
posteriorly by bulbs of the vestibule and, like
the bulbs, are partially surrounded by the bulbospongiosus muscles

The lumen of the spongy urethra is approximately 5 mm in diameter and expanded in the
bulb of the penis to form the intrabulbar fossa
and in the glans penis to form the fossa navicularis

In females, the deep perineal pouch contains the proximal part of the urethra, the
external urethral sphincter muscle, the deep
transverse perineal muscles, and related vessels and nerves

The ampulla is the widest and longest part
of the uterine tubes. It begins at the medial end
of the infundibulum. Oocytes expelled from
the ovaries are usually fertilized in the ampulla

The labia minora are folds of fat-free, hairless skin. They are enclosed in the pudendal
cleft within the labia majora, immediately surrounding the vestibule of the vagina. They have
a core of spongy connective tissue containing
erectile tissue and many small blood vessels

The parasympathetic fibers in the ovarian
plexus are derived from the vagus nerve

) The osseofibrous structures marking the
boundaries of the perineum include the pubic
symphysis, inferior pubic rami, ischial rami,
ischial tuberosities, sacrotuberous ligaments,
inferiormost sacrum, and coccyx (

) The arterial supply of the penis is mainly
from the branches of the internal pudendal
arteries. The deep arteries of the penis are the
main vessels supplying the cavernous spaces
in the erectile tissue of the corpora cavernosa
and are therefore involved in the erection of
the penis. The deep arteries pierce the crura
and run within the corpora cavernosa

The bulbospongiosus, external anal sphincter, and superficial and deep transverse perineal muscles converge at the site of the perineal
body

The ischiocavernous muscles surround the
crura in the root of the penis. Each muscle arises
from the internal surface of the ischial tuberosity and ischial ramus and passes anteriorly on
the crus of the penis, where it is inserted into
the sides and ventral surface of the crus and
the perineal membrane. The ischiocavernous
muscles force blood from the cavernous spaces
in the crura into the distal parts of the corpora
cavernosa, thus increasing the turgidity of the
penis

The pectinate line indicates the junction of
the superior part of the anal canal and the inferior part. The anal canal superior to the pectinate line differs from the part inferior to the
pectinate line in its arterial supply, innervation,
and venous and lymphatic drainage. The superior rectal artery supplies the superior part of
the anal canal and the inferior rectal arteries
supply the inferior part. Superior to the pectinate line, the internal rectal venous plexus
drains chiefly into the superior rectal vein—a
tributary of the inferior mesenteric vein and the
portal system. Inferior to the pectinate line the
internal rectal plexus drains into the inferior
rectal veins—tributaries to the caval venous system. Superior to the pectinate line, the lymphatics drain into the internal iliac lymph nodes into
the common iliac and lumbar nodes. Inferior to
the pectinate line, the lymphatics drain into the
superficial inguinal lymph nodes. Superior to
the pectinate line, the innervation is visceral;
inferior to the pectinate line, the innervation is
somatic

The distal end of the ovary connects to the
lateral wall of the pelvis by the suspensory ligament of the ovary. The ligament conveys the
ovarian vessels, lymphatics, and nerves to and
from the ovary and constitutes the lateral part
of the mesovarium of the broad ligament. The
ovary also attaches to the uterus by the ligament of the ovary

The uterus is a thick-walled, pear-shaped
muscular organ whose body lies between the
layers of the broad ligament. In the adult, the
uterus is usually anteverted and anteflexed; its
position changes with the degree of fullness of
the bladder and rectum

Only the cylindrical, narrow inferior part of
the uterus known as the cervix protrudes into
the uppermost vagina

Laterally, the peritoneum of the broad ligament is prolonged superiorly over the vessels
as the suspensory ligament of the ovary. The
part of the broad ligament by which the ovary
is suspended is the mesovarium. The part of the
broad ligament forming the mesentery of the
uterine tube is the mesosalpinx. The major part
of the broad ligament, the mesentery of the uterus, or mesometrium, is below the mesosalpinx
and mesovarium

The anterior aspect of the scrotum is supplied by anterior scrotal nerves derived from
the ilioinguinal nerve and by the genital branch
of the genitofemoral nerve. The posterior aspect of the scrotum is supplied by posterior
scrotal nerves, branches of the superficial perineal nerves, and the perineal branch of the posterior femoral cutaneous nerve