Perineum

Question 1

What is the Perineum?

Answer 1

Perineum a diamond shaped area of the body starting from the bony pelvic outlet, outer pelvic fascia, mons pubis to the intergluteal cleft in females and root of penis to the intergluteal cleft in males.

Question 2

What are the Oseofibrous boundaries of the Perineum>

Answer 2

Pubic symphysis and the ischiopubic rami anteriorly ischial tuberosities laterally, and sacrum and coccyx posteriorly with the sacrotuberous ligament posterolaterally.
Dividing the diamond shaped area by a line joining the ischial tuberosities into two triangular areas forming
Urogenital triangle - anteriorly which is covered with the urogenital membrane that is pierced by the urethra and vagina in females
Anal triangle – posteriorly that has no membranous covering.
The dividing line passes through the deeper lying Perineal body which is a mass of interlacing and converging muscular and tendinous fibers, of Bulbospongiosus, external anal sphincter, superficial and deep perineal muscles, sphincter urethrae, levator ani and other muscular layers around perineum.

Question 3

What is perineal fascia?

Answer 3

Perineal fascia is continuation of the abdominal fascia
Fatty layer (Campers) of the anterior abdominal fascia continues in the perineum and gives the prominence of the mons pubis in females whereas in males the fat amount is diminished and in the urogenital areas replaced by the dartos muscle.

Question 4

What is superficial perineal fascia?

Answer 4

The membranous layer (Scarpa’s) of the superficial fascia also continues in the perineum as Perineal fascia (Colles) and contains the urogenital perineal structures but does not continue into the anal region

Question 5

What is Deep perineal fascia (Buck’s)?

Answer 5

fascia investing all the perineal muscles (bulbospongiosus, ischiocavernosus and transverse perineal muscles) gives rise to the deep perineal fascial layers. Attached to the ischiopubic rami and the suspensory ligaments of the penis and clitoris, later merges with the external oblique fascia of the abdomen.

Question 6

Where is the Superficial Perineal Pouch?

Answer 6

Lies in between the urogenital membrane and the superficial perineal fascia with the ischiopubic rami on both sides

Question 7

What are the contents of the Male Superficial Perineal Pouch?

Answer 7

Root (bulb and crura) of the penis and associated muscles (ischiocavernosus and bulbospongiosus).
Proximal (bulbous) part of the spongy urethra.
Superficial transverse perineal muscles.
Deep perineal branches of the internal pudendal vessels and pudendal nerves.

Question 8

What are the contents of the Female Superficial Perineal Pouch?

Answer 8

Clitoris and associated muscles (ischiocavernosus).
Bulbs of the vestibule and surrounding muscle (bulbospongiosus).
Greater vestibular glands.
Superficial transverse perineal muscles.
Related vessels and nerves (deep perineal branches of the internal pudendal vessels and pudendal nerves).

Question 9

Where is the Deep Perineal Pouch?

Answer 9

Space between the parietal layer of the pelvic fascia and the perineal membrane with the obturator membranes placed laterally

Question 10

What are the contents of the Male Deep Perineal Pouch?

Answer 10

Intermediate part of the urethra, the narrowest part of the male urethra.
Deep transverse perineal muscles, immediately superior to the perineal membrane (on its superior surface), running transversely along its posterior aspect.
Bulbourethral glands, embedded within the deep perineal musculature.
Dorsal neurovascular structures of the penis.

Question 11

What are the contents of the Female Deep Perineal Pouch?

Answer 11

Proximal part of the urethra.
A mass of smooth muscle in the place of deep transverse perineal muscles on the posterior edge of the perineal membrane, associated with the perineal body.
Dorsal neurovasculature of the clitoris.

Question 12

What is the Sphincter Urethrae Muscle?

Answer 12

The Sphincter Urethrae muscle surrounds the urethra in the deep perineal pouch. It arises from the pubic arch on the two sides and passes medially to encircle the urethra.

Question 13

What are the names of the parts of the male urethra?

Answer 13

Intramural (preprostatic) part - 0.5-1.5 cm
Prostatic urethra - 3.0-4.0 cm
Intermediate (membranous) part - 1.0-1.5 cm
Spongy urethra - 15 cm

Question 14

What is the location of the male Intramural (preprostatic) part - 0.5-1.5 cm and what are its features?

Answer 14

Extends almost vertically through neck of bladder

Surrounded by internal urethral sphincter; diameter and length vary, depending on whether bladder is filling or emptying

Question 15

What is the location of the male Prostatic urethra - 3.0-4.0 cm and what are its features?

Answer 15

Descends through anterior prostate, forming a gentle, anteriorly concave curve; is bounded anteriorly by a vertical trough-like part (rhabdosphincter) of external urethral sphincter

Widest and most dilatable part; features urethral crest with seminal colliculus, flanked by prostatic sinuses into which prostatic ducts open; ejaculatory ducts open onto colliculus, hence urinary and reproductive tracts merge in this part

Question 16

What is the location of the male Intermediate (membranous) part - 1.0-1.5 cm and what are its features?

Answer 16

Passes through deep perineal pouch, surrounded by circular fibers of external urethral sphincter; penetrates perineal membrane

Narrowest and least distensible part (except for external urethral orifice)

Question 17

What is the location of the male Spongy urethra - 15 cm and what are its features?

Answer 17

Courses through corpus spongiosum; initial widening occurs in bulb of penis; widens again distally as navicular fossa (in glans penis)

Longest and most mobile part; bulbourethral glands open into bulbous part; distally, urethral glands open into small urethral lacunae entering lumen of this part

Question 18

What is the scrotum?

Answer 18

Cutaneous fibromuscular sac for the testes and associated structures. Pigmented skin and dartos fascia - a fat-free fascial layer including smooth muscle fibers (dartos muscle) responsible for the rugose (wrinkled) appearance of the scrotum. Dartos muscle assists the cremaster muscles in holding the testes closer to the body, all of which reduces heat loss.

Question 19

What is contained within the scrotum?

Answer 19

Two scrotal sacs with a midline scrotal raphe, internally, the scrotum is divided into two compartments, formed by a prolongation of the dartos fascia.
Anterior scrotal arteries, terminal branches of the external pudendal arteries (from the femoral artery), supply the anterior aspect of the scrotum. Posterior scrotal arteries, terminal branches of the superficial perineal branches of the internal pudendal arteries, supply the posterior aspect . The scrotum also receives branches from the cremasteric arteries (branches of the inferior epigastric arteries
Scrotal veins; accompany the arteries, draining primarily to the external pudendal veins.
Lymphatic vessels from the scrotum carry lymph to the superficial inguinal lymph nodes

Question 20

What are the nerves of the scrotum?

Answer 20

The nerves of the scrotum include branches of the lumbar plexus to the anterolateral surface, and branches of the sacral plexus to the posterior and inferior surfaces:
Genital branch of the genitofemoral nerve (L1, L2): supplying the anterolateral surface.
Anterior scrotal nerves: branches of the ilioinguinal nerve (L1) supplying the anterior surface.
Posterior scrotal nerves: branches of the perineal branch of the pudendal nerve (S2-S4) supplying the posterior surface.
Perineal branches of the posterior cutaneous nerve of thigh (S2, S3): supplying the posteroinferior surface.
Sympathetic fibers conveyed by these nerves assist in the thermoregulation of the testes, stimulating contraction of the smooth dartos muscle in response to cold (reduces surface area/closer to perineum) or stimulating the scrotal sweat glands while inhibiting contraction of the dartos muscle in response to warmth

Question 21

What are the testes?

Answer 21

Paired ovoid reproductive glands that produce sperms (spermatozoa) and male hormones, primarily testosterone
Testes are suspended in the scrotum by the spermatic cords, with the left testis usually suspended (hanging) more inferiorly than the right testis.
Visceral layer of the tunica vaginalis, parietal layer of the tunica vaginalis
Coiled seminiferous tubules in which the sperms are produced. The seminiferous tubules are joined by straight tubules to the rete testis, a network of canals in the mediastinum of the testis.
Testicular arteries
Veins emerging from the testis and epididymis form the pampiniform venous plexus. The pampiniform plexus is part of the thermoregulatory system of the testis (along with the cremasteric and dartos muscles) helping to keep this gland at a constant temperature. The veins of each pampiniform plexus converge superiorly, forming a right testicular vein, which enters the inferior vena cava (IVC), and a left testicular vein, which enters the left renal vein.

Question 22

What is the lymphatic drainage of the testes?

Answer 22

Lymphatic drainage of the testis follows the testicular artery and vein to the right and left lumbar (caval/aortic) and preaortic lymph nodes.

Question 23

What are the autonomic nerves of the testes?

Answer 23

Autonomic nerves of the testis arise as the testicular plexus of nerves on the testicular artery, which contains vagal parasympathetic and visceral afferent fibers and sympathetic fibers from the T7 segment of the spinal cord

Question 24

What is the epididymis of the testes?

Answer 24

An elongated structure on the posterior surface of the testis. Efferent ductules of the testis transport newly developed sperms to the epididymis from the rete testis. The duct becomes progressively smaller as it passes from the head of the epididymis on the superior part of the testis to its tail. At the tail of the epididymis, the ductus deferens begins as the continuation of the epididymal duct. In the lengthy course of this duct, the sperms are stored and continue to mature.

Question 25

What is the spermatic cord?

Answer 25

Structures running to and from the testis and suspends the testis in the scrotum
begins at the deep inguinal ring lateral to the inferior epigastric vessels, passes through the inguinal canal, exits at the superficial inguinal ring, and ends in the scrotum at the posterior border of the testis
The coverings of the spermatic cord include the following:

The cremaster muscle is innervated by the genital branch of the genitofemoral nerve (L1, L2), a derivative of the lumbar plexus . The cremaster is striated muscle receiving somatic innervation, whereas the dartos is smooth muscle receiving autonomic innervation.

Question 26

What is the contents of the spermatic cord?

Answer 26

Ductus deferens (vas deferens): a muscular tube approximately 45 cm long that conveys sperms from the epididymis to the ejaculatory duct.
Testicular artery: arising from the aorta and supplying the testis and epididymis.
Artery of ductus deferens: arising from the inferior vesical artery.
Cremasteric artery: arising from the inferior epigastric artery.
Pampiniform venous plexus: a network formed by up to 12 veins that converge superiorly as right or left testicular veins.
Sympathetic nerve fibers on arteries and sympathetic and parasympathetic nerve fibers on the ductus deferens.
Genital branch of the genitofemoral nerve: supplying the cremaster muscle.
Lymphatic vessels: draining the testis and closely associated structures , passing to the lumbar lymph nodes.

Question 27

What is the contents of the penis?

Answer 27

The penis consists of thin skin, connective tissue, blood and lymphatic vessels, fascia, the corpora cavernosa, and corpus spongiosum containing the spongy urethra and is divided into three parts; root, body, and glans.
It is composed of three cylindrical cavernous bodies of erectile tissue: the paired corpora cavernosa dorsally joined to each other except superiorly where they form the crura of the penis, each crus is attached to the inferior part of the internal surface of the corresponding ischial ramus, anterior to the ischial tuberosity.
Single corpus spongiosum ventrally, contains the spongy urethra
Layers; each cavernous body has an outer fibrous covering - tunica albuginea
Deep fascia of the penis (Buck fascia), the continuation of the deep perineal fascia that forms a strong membranous covering for the corpora cavernosa and corpus spongiosum, binding them together
Root of the penis, the attached part, consists of the crura, bulb, and ischiocavernosus and bulbospongiosus muscles. Located in the superficial perineal pouch, between the perineal membrane superiorly and the deep perineal fascia inferiorly
Bulb of penis is the enlarged posterior part penetrated superiorly by the urethra.
Body of the penis is the free part that is suspended from the pubic symphysis
Distally, the corpus spongiosum expands to form the conical glans penis, or head of the penis

Question 28

What does the root of the penis consist of?

Answer 28

The root of the penis consists of the two crura, which are proximal parts of the corpora cavernosa attached to the pubic arch and the bulb of the penis, which is the proximal part of the corpus spongiosum anchored to the perineal membrane.

Question 29

What is the vasculature of the penis?

Answer 29

Dorsal arteries of the penis run on each side of the deep dorsal vein in the dorsal groove between the corpora cavernosa, supplying the fibrous tissue around the corpora cavernosa, the corpus spongiosum and spongy urethra, and skin.
Deep arteries of the penis pierce the crura proximally and run distally near the center of the corpora cavernosa, supplying the erectile tissue in these structures.
Arteries of the bulb of the penis supply the posterior (bulbous) part of the corpus spongiosum and the urethra within it as well as the bulbourethral gland.
In addition, superficial and deep branches of the external pudendal arteries supply the penile skin, anastomosing with 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. They give off numerous branches that open directly into the cavernous spaces. When the penis is flaccid, these arteries are coiled, restricting blood

Venous Drainage of Penis; Blood from the cavernous spaces is drained by a venous plexus that joins the deep dorsal vein of the penis in the deep fascia. This vein passes between the laminae of the suspensory ligament of the penis, to enter the pelvis, where it drains into the prostatic venous plexus. Blood from the skin and subcutaneous tissue of the penis drains into the superficial dorsal vein(s), which drain(s) into the superficial external pudendal vein. Some blood also passes to the internal pudendal vein.
Innervation of Penis; The nerves derive from the S2-S4 spinal cord segments and spinal ganglia, passing through the pelvic splanchnic and pudendal nerves. Sensory and sympathetic innervation is provided primarily by the dorsal nerve of the penis, a terminal branch of the pudendal nerve, which arises in the pudendal canal and passes anteriorly into the deep perineal pouch. It then runs to the dorsum of the penis, where it runs lateral to the dorsal artery. It supplies both the skin and glans penis. The penis is richly supplied with a variety of sensory nerve endings, especially the glans penis. Branches of the ilioinguinal nerve supply the skin at the root of the penis. Cavernous nerves, conveying parasympathetic fibers independently from the prostatic nerve plexus, innervate the helicine arteries of the erectile tissue.

Question 30

What makes up the female urogenital triangle?

Answer 30

Mons pubis, labia majora (enclosing the pudendal cleft), labia minora (enclosing the vestibule of vagina), clitoris, bulbs of vestibule, and greater and lesser vestibular glands

Question 31

In the female urogenital triangle, What is mons pubis?

Answer 31

fatty eminence anterior to the pubic symphysis, pubic tubercles, and superior pubic rami

Question 32

In the female urogenital triangle, What is labia majora?

Answer 32

prominent folds of skin that indirectly protect the clitoris and urethral and vaginal orifices

Question 33

In the female urogenital triangle, What are labia minora?

Answer 33

rounded folds of fat-free, hairless skin ,surround and close over the vestibule of vagina into which both the external urethral and the vaginal orifices open.

Question 34

In the female urogenital triangle, What is the clitoris?

Answer 34

is an erectile organ located where the labia minora meet anteriorly . The clitoris consists of a root and a small, cylindrical body, which are composed of two crura, two corpora cavernosa, and the glans of the clitoris. The crura attach to the inferior pubic rami and perineal membrane, deep to the labia. The body of the clitoris is covered by the prepuce. Together, the body and glans of the clitoris are approximately 2 cm in length and <1 cm in diameter.

Question 35

In the female urogenital triangle, What is the vestibule?

Answer 35

is the space surrounded by the labia minora into which the orifices of the urethra and vagina and the ducts of the greater and lesser vestibular glands open. The external urethral orifice is located 2-3 cm posteroinferior to the glans of the clitoris and anterior to the vaginal orifice. On each side of the external urethral orifice are the openings of the ducts of the paraurethral glands.

Question 36

What is the vasculature of the female urogenital organs?

Answer 36

Abundant arterial supply to the vulva is from the external and internal pudendal arteries. The internal pudendal artery supplies most of the skin, external genitalia, and perineal muscles. The labial arteries are branches of the external pudendal artery, as are those of the clitoris.
Labial veins are tributaries of the internal pudendal veins.
Nerves; The anterior aspect of the vulva (mons pubis, anterior labia) is supplied by derivatives of the lumbar plexus: the anterior labial nerves, derived from the ilioinguinal nerve, and the genital branch of the genitofemoral nerve.
The posterior aspect of the vulva is supplied by derivatives of the sacral plexus: the perineal branch of the posterior cutaneous nerve of the thigh laterally and the pudendal nerve centrally, posterior labial branches supply the labia. Deep and muscular branches of the perineal nerve supply the orifice of the vagina and superficial perineal muscles. The dorsal nerve of the clitoris supplies deep perineal muscles and sensation to the clitoris.
The vestibule and erectile bodies of the clitoris receive parasympathetic fibers via cavernous nerves from the uterovaginal nerve plexus.

Question 37

What is the perineal nerve?

Answer 37

The perineal nerve isthe terminal branch of the pudendal nerve. It typically originates in the last portion of the pudendal canal (within the Alcock’s canal) or just as the pudendal nerve exits the canal. It runs anteriorly through the perineum, accompanied by theperineal artery.

Question 38

What are the features of the anal triangle?

Answer 38

ISCHIOANAL (rectal) FOSSAE:
Located on each side of the anal canal are large fascia-lined, wedge-shaped spaces between the skin of the anal region and the pelvic diaphragm
Filled with fat and loose connective tissue.
Communicate by means of the deep postanal space over the anococcygeal body.
Each ischioanal fossa is bounded:
Laterally by the ischium and overlapping inferior part of the obturator internus, covered with obturator fascia.
Medially by the external anal sphincter, with a sloping superior medial wall or roof formed by the levator ani as it descends to blend with the sphincter; both structures surround the anal canal.
Posteriorly by the sacrotuberous ligament and gluteus maximus.
Anteriorly by the bodies of the pubic bones, inferior to the origin of the puborectalis. These parts of the fossae, extending into the UG triangle superior to the perineal membrane (and musculature on its superior surface), are known as the anterior recesses of the ischioanal fossae.

Question 39

The contents of the ischioanal fossa include the following structures, all prone to lesions or compression:

Answer 39

Internal pudendal artery, vein, and nerve. …
Inferior rectal artery and vein.
Inferior rectal nerve.
Posterior scrotal vessels and nerves.
Perineal branch of S4 and perforating cutaneous nerve.
Lymphatics.

Question 40

What is the anal canal?

Answer 40

2.5- 3.5 cm, begins at the narrowing of the rectal ampulla (Puborectalis), ends at the anus
Internal anal sphincter – involuntary, superior 3rd of the canal, circular muscle fiber. Contracted by the sympathetics of superior rectal and hypogastric plexuses and contraction is inhibited by the parasympathetics through the pelvic splanchnic nerves.
External anal sphincter – Voluntary in control, forms a broad band on inferior 2/3rd , attached posteriorly to the annococcygeal body and anteriorly to the perineal body. Inferior rectal nerve S4 is the main nerve supply, some nerve fibers from the nerves to the levator ani also supply the external anal sphincter.
Anal columns: Internal superior half of the mucous membrane of anal canal has longitudinal ridges called the anal columns and contain the terminal branches of the superior rectal artery and vein.
Anorectal junction; where the rectum joins the anal canal. At this point, the wide rectal ampulla abruptly narrows as it traverses the pelvic diaphragm. The inferior ends of the anal columns are joined by anal valves. Superior to the valves are small recesses called anal sinuses

Question 41

What is the vasculature of the anal canal?

Answer 41

Superior rectal artery supplies the anal canal superior to the pectinate line. The two inferior rectal arteries supply the anal canal inferior to the pectinate line as well as the surrounding muscles and perianal skin. The middle rectal arteries assist with the blood supply to the anal canal by forming anastomoses with the superior and inferior rectal arteries.
Internal rectal venous plexus drains in both directions from the level of the pectinate line. Superior to the pectinate line, the internal rectal 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 around the margin of the external anal sphincter. The middle rectal veins (tributaries of the internal iliac veins) mainly drain the muscularis externa of the ampulla
Lymphatics
Superior to the pectinate line, the lymphatic vessels drain deeply into the internal iliac lymph nodes and through them into the common iliac and lumbar lymph nodes . Inferior to the pectinate line, the lymphatic vessels drain superficially into the superficial inguinal lymph nodes, as does most of the perineum.

Question 42

What is the innervation of the anal canal?

Answer 42

Nerve supply to the anal canal superior to the pectinate line is visceral innervation from the inferior hypogastric plexus, including sympathetic and visceral afferent fibers .
Sympathetic fibers maintain the tonus of the internal anal sphincter.
Parasympathetic fibers inhibit the tonus of the internal sphincter and evoke peristaltic contraction for defecation. Visceral afferents travel with the parasympathetic fibers to spinal sensory ganglia S2-S4.
Superior to the pectinate line, the anal canal is sensitive only to stretching, which evokes sensations at both the conscious and the unconscious (reflex) levels.
Inferior to the pectinate line is somatic innervation derived from the inferior anal (rectal) nerves, branches of the pudendal nerve, this part of the anal canal is sensitive to pain, touch, and temperature. Somatic efferent fibers stimulate contraction of the voluntary external anal sphincter.