Contents of the male urogenital triangle pdf - Perineum

Basic Anatomy

315

fatty layer of superficial fascia

urogenital diaphragm

anal canal

fat of ischiorectal fossa

perineal body

superior fascial layer

of urogenital diaphragm

inferior fascial layer of urogenital

diaphragm (perineal membrane)

scrotum

dartos muscle

Colles' fascia

superficial perineal pouch

deep perineal pouch

membranous layer of superficial fascia (Scarpa's fascia)

FIGURE 8.12

Arrangement of the superficial fascia in the urogenital triangle. Note the superficial and deep perineal pouches.

which covers the distal

glans penis,

expands to form the

and 8.16). At its distal extremity, the corpus spongiosum

spongiosum applied to their ventral surface (see Figs. 8.13

two dorsally placed corpora cavernosa and a single corpus

The erectile tissue is made up of

(Buck’s fascia).

cylinders of erectile tissue enclosed in a tubular sheath of

The body of the penis is essentially composed of three

Body of the Penis

(see Figs. 8.13 and 8.16).

corpora cavernosa

side in the dorsal part of the body of the penis, forming the

The two crura converge anteriorly and come to lie side by

(see Fig. 8.17).

corpus spongiosum

the penis and forms the

The bulb is continued forward into the body of

muscle.

ischiocavernosus

and is covered on its outer surface by the

Each crus is attached to the side of the pubic arch

muscles.

bulbospongiosus

and is covered on its outer surface by the

of the urogenital diaphragm. It is traversed by the urethra

situated in the midline and is attached to the undersurface

(Figs. 8.13, 8.16, and 8.17). The bulb is

crura of the penis

left

right

bulb of the penis

tissue called the

The root of the penis is made up of three masses of erectile

Root of the Penis

(Figs. 8.4 and 8.16).

The penis has a fixed root and a body that hangs free

Location and Description

In the male, the triangle contains the penis and scrotum.

Triangle

are described in subsequent sections.

The contents of the deep perineal pouch in both sexes

(see Figs. 8.12, 8.14, and 8.15).

perineal pouch

deep

superficial and deep layers of fascia is known as the

Contents of the Male Urogenital

Penis

and the

and

fascia

316

CHAPTER 8

The Perineum

dorsal vein

skin

membranous layer of superficial

deep fascia

(Buck's fascia)

corpus spongiosum

left crus

right crus

membranous part of

urethra

corona

corpus spongiosum

skin

openings of

urethral

glands

lacunae

fold of mucous membrane

fossa terminalis

external urethral

orifice

corpus spongiosum

glans penis

corona

corpus cavernosum

urethra

corpus cavernosum

deep artery

dorsal artery

superficial dorsal artery

superficial dorsal vein

fascia

FIGURE 8.13

The penis.

plexuses.

The nerve supply is from the pudendal nerve and the pelvic

Nerve Supply

are drained into the internal iliac nodes.

superficial inguinal nodes. The deep structures of the penis

The skin of the penis is drained into the medial group of

Lymph Drainage

The veins drain into the internal pudendal veins.

Veins

the internal pudendal artery.

All the above arteries are branches of

artery of the penis.

dorsal

In addition, there is the

artery of the bulb.

by the

(see Fig. 8.13); the corpus spongiosum is supplied

the penis

deep arteries of

The corpora cavernosa are supplied by the

Arteries

symphysis pubis to be attached to the fascia of the penis.

of deep fascia that extend downward from the linea alba and

The body of the penis is supported by two condensations

frenulum.

urethral orifice by a fold called the

covers the glans. It is connected to the glans just below the

is a hoodlike fold of skin that

foreskin

prepuce

The

thral meatus.

external ure

is the slitlike orifice of the urethra, called the

ends of the corpora cavernosa. On the tip of the glans penis

The penile urethra slit open to show the folds of mucous membrane and glandular orifices in the roof of

The three bodies of erectile tissue, the two corpora cavernosa, and the corpus spongiosum

A and B.

with the glans. C.

the urethra.

Blood Supply

pelvic fascia

levator ani

obturator internus

prostate

sphincter urethrae

muscle

dorsal nerve of penis

membranous part of urethra

artery of bulb

artery of crus

(deep artery of penis)

ischiocavernosus

urethra in bulb

bulbospongiosus

membranous layer of

superficial fascia

deep fascia of thigh

skin of medial side of thigh

scrotal nerves

bulb of penis

bulbourethral gland

crus of penis

inferior

fascial layer

of urogenital

diaphragm

superior fascial

layer of

urogenital

diaphragm

prostatic

urethra

FIGURE 8.14

Coronal section of the male pelvis showing the prostate, the urogenital diaphragm, and the contents of the

superficial perineal pouch.

levator ani

pelvic fascia

vagina

fascia of obturator internus

obturator

internus

obturator

membrane

dorsal nerve

of clitoris

internal pudendal

artery

artery of bulb

ischiocavernosus

bulb of vestibule

bulbospongiosus

greater vestibular gland

labium majus

labium minus

hymen

membranous layer of superficial fascia

sphincter

urethrae

superior

fascial layer of

urogenital diaphragm

artery of crus

(deep artery of clitoris)

crus of clitoris

inferior fascial layer

of urogenital diaphragm

deep fascia of thigh

skin of medial side of thigh

labial nerves

FIGURE 8.15

Coronal section of the female pelvis showing the vagina, the urogenital diaphragm, and the contents of the

317

superficial perineal pouch.

318

CHAPTER 8

The Perineum

deep dorsal vein

dorsal nerve

dorsal artery

crus of penis

corpora cavernosa

corpus spongiosum

glans penis

corona

deep dorsal vein

posterior scrotal nerves

perineal membrane

external urethral meatus

FIGURE 8.16

Root and body of the penis.

deep dorsal vein of penis

urogenital diaphragm

bulb of penis

superficial transverse
perineal muscle

levator ani

gluteus maximus

external anal sphincter

bulbospongiosus

ischiocavernosus

perineal body

corpus cavernosum

corpus spongiosum

crus of penis

FIGURE 8.17

Root of penis and perineal muscles.

Basic Anatomy

two sides and passes medially to encircle the urethra (see

deep perineal pouch. It arises from the pubic arch on the

The sphincter urethrae muscle surrounds the urethra in the

Sphincter Urethrae Muscle

the urethra (see Fig. 8.14).

penile urethra. It is the shortest and least dilatable part of

ous above with the prostatic urethra and below with the

surrounded by the sphincter urethrae muscle; it is continu

(1.3 cm) long and lies within the urogenital diaphragm,

The membranous part of the urethra is about 0.5 in.

Membranous Part of the Urethra

of the penis.

pudendal vessels and their branches, and the dorsal nerves

glands, the deep transverse perineal muscles, the internal

of the urethra, the sphincter urethrae, the bulbourethral

The deep perineal pouch contains the membranous part

the muscles and skin (see Fig. 8.8).

terminates in the superficial perineal pouch by supplying

The perineal branch of the pudendal nerve on each side

Perineal Branch of the Pudendal Nerve

muscle, and superficial transverse perineal muscles.

lowing muscles: external anal sphincter, bulbospongiosus

8.12 and 8.17). It serves as a point of attachment for the fol

the posterior margin of the urogenital diaphragm (see Figs.

This small mass of fibrous tissue is attached to the center of

Perineal Body

plied by the perineal branch of the pudendal nerve.

All the muscles of the superficial perineal pouch are sup

fix the perineal body in the center of the perineum.

into the perineal body. The function of these muscles is to

Each muscle arises from the ischial ramus and is inserted

terior part of the superficial perineal pouch (see Fig. 8.17).

The superficial transverse perineal muscles lie in the pos

Superficial Transverse Perineal Muscles

the penis.

press the crus penis and assist in the process of erection of

side (see Fig. 8.17). The action of each muscle is to com

The ischiocavernosus muscles cover the crus penis on each

Ischiocavernosus Muscles

process of erection of the penis.

drainage of the erectile tissue and thereby assisting in the

the deep dorsal vein of the penis, thus impeding the venous

residual urine or semen. The anterior fibers also compress

to compress the penile part of the urethra and empty it of

rior portion of the corpus spongiosum. Their function is

(see Fig. 8.17), cover the bulb of the penis and the poste

situated one on each side of the midline

giosus muscles,

bulbospon

ischiocavernosus muscles (see Fig. 8.17). The

cover them—namely, the bulbospongiosus muscles and the

ing the root of the penis, together with the muscles that

The superficial perineal pouch contains structures form

the thigh.

the perineal nerves and the posterior cutaneous nerves of

nerves, and the posterior surface is supplied by branches of

guinal nerves and the genital branch of the genitofemoral

The anterior surface of the scrotum is supplied by the ilioin

Nerve Supply

and lymph vessels after it.

nal canal, and into the scrotum, dragging its blood supply

on the posterior abdominal wall, down through the ingui

the testis during development has migrated from high up

of the first lumbar vertebra. This is to be expected because

ends in the lumbar (para-aortic) lymph nodes at the level

the testis and epididymis ascends in the spermatic cord and

superficial inguinal lymph nodes. The lymph drainage of

The wall of the scrotum is drained into the medial group of

Lymph Drainage

The veins accompany the corresponding arteries.

Veins

branches of the internal pudendal arteries supply the scrotum.

The external pudendal branches of the femoral and scrotal

Arteries

trol of the temperature of the testes.

promote heat loss and thus assist in the environmental con

Subcutaneous plexuses and arteriovenous anastomoses

they are fully described in Chapter 4.

tes, and the formation of the inguinal canal are interrelated,

Because the structure of the scrotum, the descent of the tes

anterior, medial, and lateral surfaces of each testis

Tunica vaginalis, which is a closed sac that covers the

versalis

Internal spermatic fascia derived from the fascia trans

Cremasteric fascia derived from the internal oblique

oblique

External spermatic fascia derived from the external

called Colles’ fascia.

nal wall, and Scarpa’s fascia (membranous layer), now

muscle, replaces the fatty layer of the anterior abdomi

Superficial fascia; the dartos muscle, which is smooth

Skin

The wall of the scrotum has the following layers:

(see Fig. 4.21).

epididymides, and the lower ends of the spermatic cords

anterior abdominal wall and contains the testes, the

The scrotum is an outpouching of the lower part of the

Location and Description

319

Scrotum

■

Blood Supply

Contents of the Superficial Perineal

Pouch in the Male

Nerve Supply

Contents of the Deep Perineal Pouch

in the Male

Fig. 8.14).

320

CHAPTER 8

penis (see Figs. 8.4, 8.14, 8.16, and 8.17). The external mea

is enclosed in the bulb and the corpus spongiosum of the

is about 6 in. (15.75 cm) long and

penile urethra

The

portion of the urethra (see Fig. 8.14).

by the sphincter urethrae muscle. It is the least dilatable

long and lies within the urogenital diaphragm, surrounded

is about 0.5 in. (1.25 cm)

membranous urethra

The

most dilatable portion of the urethra.

from the base to the apex (see Fig. 8.14). It is the widest and

about 1.25 in. (3 cm) long and passes through the prostate

is described on page 278. It is

prostatic urethra

The

static, membranous, and penile.

glans penis (see Fig. 8.4). It is divided into three parts: pro

from the neck of the bladder to the external meatus on the

The male urethra is about 8 in. (20 cm) long and extends

cles, and the prostate via the inferior hypogastric plexuses.

are then distributed to the vas deferens, the seminal vesi

parts of the sympathetic trunks. The postganglionic fibers

ers may synapse in ganglia in the lower lumbar or pelvic

neurons in the first and second lumbar ganglia. Other fib

fibers. Many of these fibers synapse with postganglionic

second lumbar segments in the preganglionic sympathetic

genital organs are thought to leave the cord at the first and

outflow (T1 to L2). The nervous impulses that pass to the

tem. Impulses pass down the spinal cord to the sympathetic

of nervous impulses takes place in the central nervous sys

At the climax of male sexual excitement, a mass discharge

semen.

seminal fluid,

accessory glands constitute the

bladder. The spermatozoa and the secretions of the several

contracts and prevents a reflux of the spermatozoa into the

press the urethra. Meanwhile, the sphincter of the bladder

contractions of the bulbospongiosus muscles, which com

ejected from the penile urethra as a result of the rhythmic

bourethral glands and penile urethral glands and is then

tatic urethra. The fluid now joins the secretions of the bul

seminal vesicles and prostate, are discharged into the pros

and the spermatozoa, together with the secretions of the

vesicles, and the prostate. The smooth muscle contracts,

epididymis and the vas deferens on each side, the seminal

thetic nerve fibers to the smooth muscle of the duct of the

nervous impulses, results in a discharge along the sympa

Friction on the glans penis, reinforced by other afferent

thral glands.

becomes moist as a result of the secretions of the bulboure

ing sex play, the external urinary meatus of the glans penis

During the increasing sexual excitement that occurs dur

vasoconstriction. The penis then returns to its flaccid state.

inhibited, the arteries supplying the erectile tissue undergo

ejaculation takes place, or the excitement passes off or is

Once the climax of sexual excitement is reached and

diameter and assumes the erect position.

ated and maintained. The penis thus increases in length and

is retarded so that the internal pressure is further accentu

By this means, the outflow of blood from the erectile tissue

pressing their draining veins against the surrounding fascia.

giosum become engorged with blood and expand, com

erectile tissue. The corpora cavernosa and the corpus spon

great increase in blood flow through the blood spaces of the

penis. Vasodilatation of the arteries now occurs, producing a

branches, which enter the erectile tissue at the root of the

the internal pudendal arteries and are distributed along their

the postganglionic neurons. The postganglionic fibers join

fibers enter the inferior hypogastric plexuses and synapse on

fourth sacral segments. The parasympathetic preganglionic

to the parasympathetic outflow in the second, third, and

stimuli. Efferent nervous impulses pass down the spinal cord

in a bombardment of the central nervous system by afferent

stimuli from the general body skin and genital skin, result

other psychic stimuli, fortified later by direct touch sensory

various sexual stimuli. Pleasurable sight, sound, smell, and

Erection in the male is gradually built up as a consequence of

the penis (see Fig. 8.14).

through the deep perineal pouch and supplies the skin of

The dorsal nerve of the penis on each side passes forward

Dorsal Nerve of the Penis

which supplies the skin and fascia of the penis.

the penis,

dorsal artery of

(deep artery of penis); and the

of the penis

arteries to the crura

artery to the bulb of the penis;

the deep perineal pouch and passes forward, giving rise to

The internal pudenal artery (see Fig. 8.14) on each side enters

Internal Pudendal Artery

perineal body. These muscles are clinically unimportant.

ischial ramus and passes medially to be inserted into the

sphincter urethrae muscle. Each muscle arises from the

The deep transverse perineal muscles lie posterior to the

Deep Transverse Perineal Muscles

result of erotic stimulation.

of the urethra. The secretion is poured into the urethra as a

of the urogenital diaphragm) and enter the penile portion

ducts pierce the perineal membrane (inferior fascial layer

beneath the sphincter urethrae muscle (see Fig. 8.14). Their

The bulbourethral glands are two small glands that lie

which micturition can be voluntarily stopped.

thra and relaxes during micturition. It is the means by

The muscle compresses the membranous part of the ure

sphincter.

The perineal branch of the pudendal nerve supplies the

Nerve Supply

The Perineum

Action

Bulbourethral Glands

the

Erection of the Penis

-
-

Ejaculation

-
-

Male Urethra

and the orifices of the urethra and the vagina.

In the female, the triangle contains the external genitalia

Triangle

the urogenital diaphragm.

bulbourethral glands open into the penile urethra below

(navicular fossa) (see Fig. 8.4). The

fossa terminalis

the urethra that lies within the glans penis is dilated to form

tus is the narrowest part of the entire urethra. The part of

the

Contents of the Female Urogenital