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Perineum UTHSCSA Anatomy Module 5

Objectives:

When you have completed your study of this material, you should be able to:
1. Define the boundaries of the perineum.
2. Define the inferior pelvic aperture (pelvic outlet).
3. Define the pelvic diaphragm and name the muscles that make it up.
4. Give the boundaries and contents of the anal triangle.
5. Give the boundaries and contents of the ischiorectal fossa.
6. Give the location and contents of the pudendal canal.
7. Name the branches of the pudendal nerve and name the structures which each branch innervates.
8 Define the urogenital diaphragm, giving its musculature, perineal fascias, and perineal spaces.
9. Define the central tendon of the perineum (perineal body).
10. Give the contents of the male perineum.
11. Give the innervation and lymphatic drainage of the scrotum.
12. For the penis, give its composition, parts, ligaments, arterial and venous supply, lymphatic drainage, and innervation.
13. Give the contents of the superficial and deep perineal spaces for each gender. Label a diagram showing the structures found in these spaces.
14. Name the muscles of the superficial perineal space.
15. List three differences distinguishing the male and female perineum.
16. List and define the parts of the vulva.
17. Give the vascular supply and lymphatic drainage of the vulva.
18. Discuss the innervation of the female perineum.

Define the Perineum:

A diamond shaped region extending from the tip of the coccyx to the ischial tuberosities, and then to the symphysis pubis.

What are the superior and inferior boundaries of the perineum?*

1) Inferior boundary: is skin.
2) Superior boundary: Roof is the pelvic outlet (2 diaphragms: UGD and pelvic diaphragm).
3) In other words, it is the region superficial to (inferior to) the inferior pelvic aperture (pelvic outlet).

What are the bony boundaries of the perineum? *

Boundaries of the perineum: Superiorly, the perineum is limited by 2 diaphragms: the pelvic diaphragm and the UGD; inferiorly, it has a free surface covered by skin. Its other boundaries are as follows:
1. Symphysis pubis *
2. Inferior pubic rami *
3. Ischial rami
4. Ischial tuberosities
5. Sacrotuberous ligament *
6. Coccyx *

What are the two divisions of the perineum?

The perineum is divided into two triangles by a transverse line between the two ischial tuberosities.
a. Urogenital triangle - contains the external urogenital organs.
b. Anal triangle - contains the anal canal.

Describe the inferior pelvic aperature:

Inferior pelvic aperture (pelvic outlet) - it is the "roof" of the perineum or the "floor" of the pelvic cavity

What closes the inferior pelvic aperature?

1. Closed in both the male and female by 2 diaphragms (UGD and pelvic) except where it transmits the urethra, vagina (female), and the anal canal.
2. Anterior part of the inferior pelvic aperture is closed primarily by the urogenital diaphragm. (UGD)
3. Posterior part of the inferior pelvic aperture is closed by the pelvic diaphragm (the 2 levator ani muscles and the 2 coccygeus muscles).

Describe the pelvic diaphragm:

PELVIC DIAPHRAGM - a muscular bed that is the floor of the pelvic cavity

Describe the shape and location of the pelvic diaphragm:

A. It is part of the roof of the perineum.
B. It closes the posterior pelvic outlet in the same way that a funnel might close it. It is a muscular bed that forms the V-shaped floor of the pelvic cavity. The anal canal passes through it.

Describe the composition of the pelvic diaphragm:

Composition - the two levator ani muscles and the two coccygeus muscles.

What are the boundaries of the anal triangle?

1. Posteriorly - the tip of the coccyx.
2. Posterolaterally - the gluteus maximus muscles, and the sacrotuberous ligaments to the ischial tuberosities.
3. Anteriorly - the line joining the ischial tuberosities.

What are the contents of the anal triangle?

1. Anal orifice
2. External anal sphincter
3. Ischiorectal fossae

What muscle closes the anus? What is its action? What nerve innervates it?**

1) Sphincter ani externus muscle - the external anal sphincter;
2) this muscle is voluntarily controlled and closes the anus as well as drawing the anal canal anteriorly.
3) It is innervated by the inferior rectal nerve (origin = pudendal nerve).

Where is the Ischiorectal fossa located? What is the anterior recess of this fossa? Where is its posterior recess?

1) Located between the skin of the anal triangle and the pelvic diaphragm (levator ani muscles and coccygeus muscles).
2) Its anterior recess extends above the urogenital diaphragm to the body of the pubis. 3) Its posterior recess lies between the coccygeus and the gluteus maximus.

What are the boundaries of the Ischiorectal fossa? **

a. LATERALLY - obturator internus and ischium
b. medially - LEVATOR ANI
c. posteriorly - GLUTEUS MAXIMUS and sacrotuberous ligament
d. inferiorly - UGD anteriorly, ischiorectal fossa is posterior to the UGD so boundary is SUPERIOR FASCIA OF UGD , and SKIN LATERAL TO THE ANUS

What are the contents of the ischiorectal fossa?

1) fat,
2) internal pudendal vessels and branches,
3) branches of the pudendal nerve.

Where do the 2 ischiorectal fossa communicate with one another?

The 2 ischiorectal fossae communicate with each other:
1) posterior to the anal canal
2) superior to the anococcygeal ligament

What is the Pudendal canal and where is it located? *

Pudendal (Alcock's) canal:
A fibrous tunnel in the fascia FASCIAL CLEFT of the obturator internus muscle.
It is located in the LATERAL WALL of the ischiorectal fossa, medial to the ischial tuberosity.

What structures pass through the pudendal canal?

1) Most of the internal pudendal vessels
2) The branches of the pudendal nerve

Where does the pudendal nerve arise from?

Arises from the sacral plexus by separate branches from the anterior division of S2, S3, and S4.

How does the pudendal nerve leave the pelvis?

It leaves the pelvis by passing through the greater sciatic foramen (between the piriformis and coccygeus muscles).

How does the pudendal nerve enter the ischiorectal fossa?

From the greater sciatic foramen It crosses lateral to the ischial spine and sacrospinous ligament and enters the ischiorectal fossa through the lesser sciatic foramen.

When does the pudendal nerve divide? What are its branches? *

As it enters the pudendal canal (Alcock's canal), the pudendal nerve divides into three branches:
1). Inferior rectal nerve
b. Perineal nerve
c. Dorsal nerve of the penis (or clitoris) - arises in the pudendal (Alcock's) canal, passes through the urogenital diaphragm (deep perineal space), and passes onto the dorsum of the penis (or clitoris) where it runs lateral to the dorsal artery of the penis (or clitoris). It is sensory to the body and glans of the penis (clitoris).

What are the functions of the inferior rectal nerve?

Sensory to the skin around the anus; motor to the external anal sphincter. This nerve is sometimes called the inferior hemorrhoidal nerve.

What are the functions of the perineal nerve? *

1) Sensory to scrotum (or labia)
2) motor to the muscles in the superficial perineal space
3) motor to the muscles in the deep perineal space (muscles of the UGD).

Where does the Dorsal nerve of the penis (or clitoris) arise from? What is its function?

1) Arises in the pudendal (Alcock's) canal, passes through the urogenital diaphragm (deep perineal space), and passes onto the dorsum of the penis (or clitoris) where it runs lateral to the dorsal artery of the penis (or clitoris).
2) It is sensory to the body and glans of the penis

What are the cutaneous nerves of the Buttocks?

1. Superior cluneal nerves (posterior primary rami of L1-3 )
2. Middle cluneal nerves (posterior primary rami of S1-3 )
3. Inferior cluneal nerves (anterior primary rami of S1-3)

What is the urogenital diaphragm and what does it close?

1) The urogenital diaphragm is a thin sheet of striated muscle along with its superior and inferior fascial layers, all of which stretch between the two sides of the pubic arch.
2) The urogenital diaphragm closes the anterior part of the pelvic outlet

What is the anterior border of the urogenital diaphragm? Describe this structure: *

Transverse perineal ligament -it is fused fascia and nonmuscular; ANTERIOR BORDER of the urogenital diaphragm (UGD).

Where is the arcuate ligament of the pubis?

Arcuate ligament of the pubis - located at the inferior margin of the symphysis pubis.

Where is the deep dorsal vein?

Deep dorsal vein - located between the transverse perineal ligament and the arcuate ligament of the pubis.

What are the contents of the Urogenital Diaphragm?

1. Sphincter urethrae muscle
2. Deep transverse peroneus (perineal) muscle

Describe the Sphincter Urethrae muscle; How does it differ in the male and female?

a. It is the voluntary sphincter of the urethra.
b. In the female, its fibers encircle the urethra and some fibers extend to the vagina.
c. In the male, its fibers encircle the membranous urethra. The bulbourethral glands (Cowper's glands) are found within its muscle fibers.

Describe the Deep transverse peroneus (perineal) muscle:

Its fibers compose the posterior part of the urogenital diaphragm.

Define the central tendon of the perineum; Why is it important?

Central tendon of the perineum (also known as the perineal body or "the perineum"): a small,
1) wedge-shaped mass of fibrous tissue at the center of the perineum;
2) a number of the perineal muscles have a common attachment at this tendon

What perineal muscles have a common attachment to the central tendon of the perineum? **

1) levator ani muscles,
2) bulbospongiosus, AKA BULBOCAVERNOSUS
3) superficial transverse perineal muscles,
3) the deep transverse perineal muscles,
4) some fibers of the external anal sphincter,

Describe the superficial perineal fascia; why is this fascia important?

1) Superficial perineal fascia (also known as Colles' fascia); it is the fibrous layer of the tela subcutanea (deep to the skin).
2) It is important in confining urine that can be released by a rupture of the urethra.

What areas are covered by the superficial perineal fascia (Colle's) and what other fascias is this fascia continuous with? ***

1) . Continuous with SCARPA'S FASCIA (the DEEP LAYER of the abdomen's superficial fascia [TELA SUBCUTANEA]) on the anterior abdominal wall.
2) . Anteriorly, it is prolonged over the penis and scrotum in the male (it is superficial to Buck's fascia of the penis); it covers part of the structures of the vulva in the female.
3) . Posteriorly, it is fused to the posterior margin in the urogenital diaphragm.
4) . Laterally, it is fused to the fascial lata of the thigh; it also covers the ischial tuberosity.

Name the three perineal fascias:

1. Superficial perineal fascia (also known as Colles' fascia); it is the fibrous layer of the tela subcutanea (deep to the skin).
2. Inferior fascia (of the urogenital diaphragm) - also known as the perineal membrane.
3. Superior fascia (of the urogenital diaphragm) - superior to the UGD; that is, in the male, it is inferior to the prostate gland; it is superior to the sphincter urethrae muscle and the deep transverse perineal muscle.

What are the two perineal spaces? *

1. Superficial perineal space - the FASCIAL SPACE between the SUPERFICIAL PERINEAL FASCIA (Colles' fascia) and the inferior fascia of the UGD (PERINEAL MEMBRANE).
2. Deep perineal space - the fascial space enclosed by the superior and inferior fascias of the urogenital diaphragm (UGD).

What does the Superficial perineal space contain in the male?

In the male, it contains the:
1) root of the penis (and associated muscles)
2) the proximal part of the spongy (cavernous) urethra.

What does the Superficial perineal space contain in the female?*

In the female, it contains:
1) the root structures of the clitoris (and associated muscles),
2) Two greater vestibular glands (Bartholin's glands), and the two vestibular bulbs.

What does the Superficial perineal space contain in both sexes?

In both sexes, it contains:
1) branches of the internal pudendal vessels
2) branches of the pudendal nerves.

What are the muscles of the superficial perineal space? (5 muscles)**

1.) Two superficial transverse perineus (perineal) muscles.
2.) Bulbospongiosus (BULBOCAVERNOSUS) muscle - covers the bulb of the corpus spongiosum in the male; it covers the vestibular bulbs and the Bartholin's glands in the female.
3.) Two ischiocavernosus muscles - cover the crura of the corpus cavernosum in the male; cover the crura of the clitoris in the female.

What does the Deep perineal space contain in the male?***

In the male, this space contains:
1) the membranous urethra,
2) the sphincter urethra muscle (with the bulbourethral or Cowper's glands),
3) the deep transverse perineus muscle.

What does the Deep perineal space contain in the female?*

In the female, it contains:
1) part of the urethra,
2) the sphincter urethrae muscle,
3) the inferior part of the vagina,
3) the deep transverse perineus muscles.

What does the Deep perineal space contain in both sexes? *

In both sexes, it contains:
1) the internal pudendal vessels
2) the DORSAL NERVE of the penis/clitoris.

What are the layers of the urogenital triangle from inferior to superior?

1) Skin
2) Fat and other CT
3) Superficial perineal fascia
4) Superficial perineal space
5) Inferior fascia of the UGD
6) Deep Perineal space = UGD
7) Superior fascia of the UGD
8) Anterior recess of the Ischiorectal fossa
9) Inferior Fascia of pelvic diaphragm.

What two parts make up the male perineum?

1) Scrotum
2) Penis

What is the scrotum?

Scrotum -
1) a pouch derived from the anterior abdominal wall,
2) it contains the testes and their coverings.
3) It is composed of skin and dartos muscle.

Define Dartos muscle:

Dartos muscle - smooth muscle which causes the wrinkled appearance of the scrotal skin.

How is the scrotum innervated anteriorly and posteriorly?

Innervation of the scrotum:
1). Anterior - anterior scrotal branches of the ilioinguinal nerve (L1) and genital branch of genitofemoral nerve (L1-L2).
2). Posterior - scrotal branches of the perineal nerve (origin: pudendal nerve) and the perineal branch of the posterior femoral cutaneous nerve (S1-S3).

What are the lymphatics of the male perineum?

1) Penis and scrotum drain to inguinal lymph nodes
2) Testicles drain to lumbar lymph nodes

Which side of the penis is dorsal and which is ventral?

1) The anterior surface of the flaccid penis is the dorsal surface.
2) The posterior surface of the flaccid penis (nearest the urethra) is the ventral surface of the penis.

What is the penis composed of?

1) It is composed of three cavernous bodies, each enclosed in a dense, fibrous capsule known as the tunica albuginea.
a. Corpus cavernosum penis (2) - in dorsal part of penis. Note: the deep artery in each one.
b. Corpus spongiosum penis (1) - in ventral part of penis; it contains the spongy (cavernous) urethra.

What does Buck's fascia surround?

The deep fascia of the penis (Buck's fascia) surrounds:
1) all three cavernous bodies,
2) the 2 dorsal arteries and nerves,
3) the deep dorsal vein.
4) This fascia also separates corpus spongiosum from the two corpora cavernosa.

Define the crus:

Crus - The posterior part of each corpus cavernosum; attached to the ischiopubic ramus. Each crus is covered by the ischiocavernosus muscle.

Define the Bulb of the penis:

Bulb of the penis - Posterior part of the corpus spongiosum; it is attached to the inferior fascia of the urogenital diaphragm (perineal membrane). The bulb is covered by the bulbospongiosus muscle.

Define the root of the penis:

Root of the penis - The attached portion located in the superficial perineal space; formed by the two crura, the bulb, and the muscles covering each of them.

Define the Body of the penis:

Body of the penis - The free part of the penis, which is pendulous in the flaccid state; formed by the two corpora cavernosa and the corpus spongiosum.

Define the glans penis:

Glans penis - The distal expanded portion of the corpus spongiosum; it covers the blunt ends of the corpora cavernosa.

Define the prepuce:

Prepuce - A double layer of skin which covers the glans; this is removed in the operation of circumcision.

Define the frenulum:

Frenulum - A median fold passing from the deep layer of the prepuce to the glans penis.

What are the ligaments of the penis?

a. Fundiform ligament -
b. Suspensory ligament -

Describe the fundiform ligament of the penis:

1) Continuous with Scarpa's fascia (the fibrous layer of the tela subcutanea of the anterior abdominal wall);
2) splits into two parts which encircle the penis superficial to the deep fascia of the penis (Buck's fascia)...
3)continuous with the superficial perineal fascia (Colle's fascia)

Describe the suspensory ligmant of the penis:

Arises from the symphysis pubis and is attached to the deep fascia of the penis (Buck's fascia).

What are the arteries of the penis?

1) 2 Dorsal arteries of the penis
2) 2 Deep arteries of the penis

Describe the dorsal arteries of the penis:

1) The continuation of the internal pudendal artery (origin of the internal pudendal artery is the internal iliac artery).
2) Each dorsal artery of the penis runs through the UGD to the dorsal penis where it is then located between the deep dorsal vein and the dorsal nerve, deep to Buck's fascia.

Describe the deep arteries of the penis:

1) A branch of the internal pudendal artery;
2) these arteries enter each crus of the penis and then run within the corpus cavernosum to supply the cavernous spaces that fill with blood during erection.

Describe the mechanism of erection:

1) With erotic stimulation, nerve impulses transmitted through the preganglionic parasympathetic fibers in the pelvic splanchnic nerves (S2, S3, S4) result in relaxation of the smooth muscles in the walls of the deep arteries of the penis entering the cavernous spaces.
2) Blood is then allowed to flow freely into the cavernous spaces with resulting compression of the venous return.

What are the veins of the penis?

a. Superficial dorsal vein - Under the skin on the dorsal surface of the penis.
b. Deep dorsal vein - An unpaired vein that runs between the two dorsal arteries, deep to Buck's fascia.

Describe the deep dorsal vein: *

1.) It enters the pelvis through the gap between the TRANSVERSE PERINEAL LIGAMENT (the anterior border of the urogenital diaphragm) and the ARCUATE LIGAMENT OF THE PUBIS (the posterior margin of the pubic symphysis).
2.) It drains into the venous plexus around the prostate gland, which then drains into the internal iliac veins.

What are the differences between the male and female perineum?

1. The vagina pierces the urogenital diaphragm (UGD.
2. The urethra is anterior to the vagina; it pierces the UGD and is surrounded by the sphincter urethra muscle.
3. The clitoris (which is homologous to the penis) does not contain the urethra.

What is the vulva composed of?

Vulva (pudendum) - The female's external genital organs. The vulva includes:
1) the mons pubis,
2) the labia majora,
3) the labia minora,
4) the vestibule of the vagina,
5) the clitoris,
6) the bulb of the vestibule,
7) the greater vestibular glands.

Define mons pubis

Mons pubis - The rounded fatty eminence anterior to the symphysis pubis.

Describe the labia majora:

Labia majora (singular: labium majus) -
1) Homologous to the scrotum;
2) joined anteriorly by the anterior labial commissure.
3) It contains the distal ends of the round ligaments of the uterus, which pass through the inguinal canals.

Describe the labia minora: *

Labia minora (singular: labium minus) -
1) Thin, delicate folds of hairless skin which enclose the vestibule of the vagina
2) lie on each side of the orifices of the urethra and the vagina.
3) Each labium minus splits at its anterior end into 2 folds: anterior fold - PREPUCE of clitoris; posterior fold - FRENULUM of the clitoris.

Define vestibule of the vagina; What opens here?

1) Vestibule of the vagina - The space between the labia minora.
2) It receives the openings of the:
a) urethra,
b) the vagina,
c) the ducts of the greater vestibular glands (Bartholin's glands).

Define external urethral orifice:

a. External urethral orifice - Located posterior to the clitoris and anterior to the vaginal orifice.

Define vaginal orifice:

b. Vaginal Orifice - Inferior and posterior to the external urethral orifice.

Define hymen:

c. Hymen - A thin, incomplete fold of mucous membrane surrounding the vaginal orifice.

Describe the greater vestibular glands:**

Greater vestibular (Bartholin's) glands -
1) Located on each side of the vestibule, posterolateral to the vaginal orifice.
2) Located in the SUPERFICIAL PERINEAL SPACE just caudal to the bulb of the vestibule, deep to the bulbospongiosus muscle.
3) They are homologous to the bulbourethral (Cowper's) glands in the male, but they are not located in the urogenital diaphragm.

What is the clitoris homologous to?

Homologous to the penis in the male, but not transversed by the urethra.

What is the clitoris composed of?

1) Composed of two corpora cavernosa with attached crura and a glans.
2) There is no corpus spongiosum.
3) Each crus is covered by an ischiocavernosus muscle.

What is the arterial supply of the clitoris?

The arterial supply is from the deep and dorsal arteries of the clitoris (branches of the internal pudendal artery).

What is the venous return of the clitoris?

The venous return from the clitoris is through the deep dorsal vein → vesical venous plexus.

What structure in the female is homologous to the corpus spongiosum and the bulb of the penis?

Bulbs of the vestibule - two erectile tissue masses that are homologous to the corpus spongiosum and the bulb of the penis.

Where are the bulbs of the vestibule located?

They lie on either side of the vaginal orifice in the superficial perineal space and are covered by the paired bulbospongiosus muscles.

Where are the female lubrication glands?

Just caudal to each bulb (of the vestibule) is a greater vestibular gland, also covered by the bulbospongiosus muscle.

What is the vascular supply of the labia?

labia - supplied by labial vessels from perineal branches of internal pudendal vessels

What is the vascular supply of the vulva?

vulva - supplied by the external pudendal vessels (origin or destination: femoral vessels)

Where does the lymph from the vulva drain? What about the ovaries?*

1) lymph from the vulva drains to inguinal nodes.
2) Lymph from the ovaries drain to lumbar lymph nodes

What is the innervation of the female perineum?

As in the male, the musculature and skin of the female perineum are mainly innervated by branches of the pudendal nerve.
However to block pain you also need to block the posterior femoral cutaneous nerve

What are three other nerves in addition to the pudendal that supply the perineum?

a. The anterior labial branches of the ilioinguinal nerves (L1).
b. The genital branch of the genitofemoral nerve. (L1-L2)
c. Perineal branches of the posterior femoral cutaneous nerve (long pudendal nerve). S1-S3

Where is the pudendal nerve anesthetized?

The pudendal nerve may be anesthetized where it passes lateral (dorsal) to the ischial spine.

What is the inferior rectal artery a branch of?*

The internal pudendal artery

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