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Anatomy IV > Perineum > Flashcards

Perineum Flashcards

1
Q

What is the perineum?

A

Diamond-shaped region located just inferior to the pelvic diaphragm that supports male and female external genitalia, as well as to accommodate the terminal pathways for the urinary and GI tracts

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2
Q

Anterior boundary of perineum:

A

Pubic symphysis

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3
Q

Posterior boundary of perineum:

A

Tip of the cocyx

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4
Q

Lateral boundary of perineum:

A

Ischial tuberosities, ischipubic rami and sacrotuberous ligaments

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5
Q

Superior boundary of perineum:

A

Pelvic diaphragm

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6
Q

The perineum can be further subdivided into 2 triangular regions by a line that traverses both ischial tuberosities:

A

Urogenital and anal triangles

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7
Q

What is the UG triangle?

A

It is located anterior (ventral) to the line defined by the ischial tuberosities, ischiopubic rami, and pubic symphysis. It contains the UG diaphragm, external genitalia, and the terminal part of the urinary tract

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8
Q

What is the anal triangle?

A

Located posterior (dorsal) to the same line. This space is defined by the coccyx, sacrotuberous ligament, and ischial tuberosities and contains the anal canal, the ischioanal fat pad, and ischioanal fossa

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9
Q

What is compartmentalization?

A

The UG triangle is occupied by several distinct layers of fascia that compartmentalize this region into a superficial and deep pouch

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10
Q

What is the deep pouch?

A

Comprised of a muscular diaphragm (UG diaphragm) that is attached laterally along the ischipubic rami and bridges across the full extent of the UG-triangle. This deep transverse perineal muscle (and assoc fibers that contribute to the urethra in the male and female) lie superiorly to a fibrous aponeurotic sheet - perineal membrane to form the UG diaphragm

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11
Q

How is the UG diaphragm suspended?

A

Laterally by the ischipubic rami and is anchored at midline at its posterior border by a thickened centralized tendon - perineal body.

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12
Q

The perineal body is anchored to the:

A

Anal canal, which in turn is suspended posteriorly by the anal coccygeal ligament to the cocyx at midline

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13
Q

Where is the perineal membrane located?

A

Inferior to the deep transverse perineal muscle. It is made up of a tough aponeurotic sheet (tendinous sheet) which maintains the integrity of the UG diaphragm

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14
Q

Anterior boundary of deep pouch of UG diaphragm:

A

Body of pubis, just lateral to the pubic symphysis (an opening - hiatus for deep dorsal vein - bridges the region of the pubic symphysis)

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15
Q

Lateral boundary of deep pouch of UG diaphragm:

A

Ischiopubic rami (IPR) up to the ischial tuberosities

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16
Q

Posterior boundary of deep pouch of UG diaphragm:

A

A transverse line through ischial tuberosities through the center attachment called the perineal body

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17
Q

Superior boundary of deep pouch of UG diaphragm:

A

Investing fascia (not continuous) formed from the fascia coverings from the levator ani and obturator internus muscles

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18
Q

Inferior boundary of deep pouch of UG diaphragm:

A

Perineal membrane

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19
Q

Contents of the deep pouch (8):

A
  1. Deep transverse perineal m - M&F
  2. Compressor urethrae and sphincter urethrovaginalis - F
  3. Membranous urethrae - M&F
  4. Bulbourethral glands
  5. Dorsal n. penis (M) and clitoris (F)
  6. Internal pudendal a. - M&F
  7. Dorsal and deep arteries of the penis/clitoris
  8. Internal pudendal vv - M&F
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20
Q

What is the superficial pouch (compartment) of the UG triangle?

A

Includes the external genitalia and their investing fascias, and it can be subdivided into 2 spaces, one that lies between the perineal membrane and the deep perineal fascia - deep space of the superficial pouch. The other is located between the deep perineal fascia and the superficial perineal fascia - superficial space (of the superficial pouch)

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21
Q

What are the components of the DEEP space of the superficial compartment?

A
  • Deep perineal fascia (Gallaudet’s fascia)
  • Crus of penis (corpora cavernosa), bulb of penis (corpus spongiosum), ischiocavernosus m, bulbospongiosus m, superficial transverse perineal m, deep perineal nn, and perineal aa.
  • F: crus of clitoris, bulb of vestibule, greater vestibular gland, ischiocavernosus m, bulbospongiosus m, superticial transverse perineal mm, deep perineal nn, and perineal aa
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22
Q

What is the deep perineal fascia?

A

Gallaudet’s fascia - is the investing fascia of the erectile tissue muscles in both male and female. This fascia is incredibly thick and has a firm attachment to the posterior border of the perineal membrane and laterally to the ischipubic rami. It reflects and firmly attaches to the body of the penis and clitoris at the anterior boundary of the perineum and becomes continuous with their respective deep penile fascia (Buck’s fascia) and the deep fascia of the clitoris

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23
Q

The deep perineal fascia is also continuous with the:

A

External abdominal oblique fascia

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24
Q

Components of the superficial space of the superficial compartment:

A

This region is defined as the space located between the deep perineal fascia and the superficial perineal fascia. It contains fatty CT invested by the superficial perineal fascia

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25
Q

What is the superficial perineal fascia?

A

It has firm attachment to the posterior margin of the perineal membrane and the ischiopubic rami. It reflects on to the body of the penis and clitoris ad becomes continuous with their respective superficial facial layers (superficial fascia of the penis and of the clitoris)

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26
Q

The superficial perineal fascia and the superficial penile/clitoral fascia in the male:

A

The superficial perineal fascia and the superficial penile fascia contain smooth muscle fibers (dartos muscle) that make attachments to the skin of the scrotum and penis. This layers LACKS fatty tissue and is continuous with Camper’s and Scarpa’s fascia on the anterior abdominal wall.

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27
Q

The superficial perineal fascia and the superficial clitoral fascia in the female:

A

The superficial perineal fascia lacks a Dartos layer but contains both a fatty and membranous fascia which are continuous with Camper’s and Scarpa’s fascia respectively

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28
Q

Male external genitalia includes:

A

Scrotum and penis

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29
Q

What is the scrotum?

A

A double sac, separated by a septum which houses the testicles. It consists of 2 layers - an outer layer of skin containing hair follicles and glands (sweat and sebaceous) , overlying a thickened fascial layer (superficial perineal fascia) that contains smooth muscle fibers (Dartos layer)

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30
Q

What is the function of the scrotum?

A

Regulates testicular temperature by contracting (in response to the cooling of the testicles) or relaxing in response to elevated temperature

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31
Q

What is the innervation of the scrotum?

A

Sensory by:

  1. Anterior scrotal n (branch of ilioinguinal n)
  2. Genital branch of genitofemoral n.
  3. Posterior scrotal (branch of pudendal n)
  4. Perineal branch of the posterior femoral cutaneous n.
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32
Q

Blood supply to the scrotum by:

A
  1. Posterior scrotal a. - branch of the internal pudendal a
  2. Anterior scrotal a - branch of the external pudendal a
  3. Testicular a - very small contribution to the scrotum
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33
Q

What is the penis composed of?

A

3 cylinders of specialized erectile tissue (corpora cavernosa - paired) and the corpus spongiosum which are firmly anchored to the UG diaphragm. These erectile tissues are invested by muscles and 2 layers of perineal fascia in the UG triangle and merge to form the body of the penis

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34
Q

What is the corpora cavernosum?

A

Paired cylinders of erectile tissue, with their proximal ends (crus) fused to urogenital diaphragm and the ischiopubic rami. The distal ends form 2/3’s of the penile body and terminate with blunt ends that are capped by the glans of the penis (terminal part of the corpus spongiosum)

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35
Q

In the UG triangle, the crus are invested by:

A

Deep penile fascia (Buck’s), then by ischiocavernousus m., which is then invested by a second layer of the deep perineal fascia (Gallaudet’s) The deep perineal fascia blends with the deep penile fascia on the body of the penis

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36
Q

What is the corpus spongiusom (CS)?

A

Single midline cylinder of erectile tissue that contains the penile urethra. At its proximal end, it si firmly attached to the perineal membrane - penile bulb.

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37
Q

The penile bulb receives glandular secretions from the paired:

A

Bulbourethral glands (cowper’s glands) and defines the transition from the membranous urethra (found in the UG diaphragm) to the penile urethra

38
Q

As the CS continues ventrally, it attaches in between the 2 corpora cavernosum on their inferior surface to form:

A

The body of the penis. The CS is also invested by the deep penile fascia, from the penile bulb to the margin of corona of the glans (glans is NOT covered by this fascia)

39
Q

What is the tunica albuginea?

A

Each of the erectile tissues (corpora cavernosum and spongiosum) have a thick fibrous outer capsule

40
Q

The body of the penis is a pendulous structure that is attached to the:

A

Pubic symphysis by the suspensory ligament of the penis and terminates as the glans of the penis. The glans of the penis is void of both deep and superficial penile fascia.

41
Q

At the tip of the glans, the penile urethra terminates as the:

A

External urethral meatus and just deep to this is an expanse in the urethra called the navicular fossa - designated to disrupt linear flow of urine to produce a concentrated stream upon urination

42
Q

Innervation of the perineum is provided mostly by the:

A

Pudendal n (S2-4)

43
Q

What is the pathway of the pudendal n?

A

It has its origin from the sacral plexus and is derived from ventral rami of S2-4. The nerve exits out of the pelvis into the gluteal region via the greater sciatic foramen and enters the perineum, through the lesser sciatic foramen, by passing anterior to the sacrotuberous ligament and posterior to the sacrospinous ligament and tip of the ischial spine. The pudendal n. enters the perineum in the ischianal fossa of the anal triangle

44
Q

What are the branches of the pudendal n?

A

The branching pattern of the pudendal nerve in the male and female are identical, however naming of the perineum branches are gender specific

  1. Inferior rectal n
  2. Distal branches of pudendal n –> branches into a perineal n. and dorsal n. of penis (clitoris)
  3. Perineal n –> superficial perineal n (sensory) and deep perineal n (motor)
    • Superificial perineal branch –> posterior scrotal branch (or labial)
  4. Dorsal n
45
Q

What is the course of the inferior rectal n?

A

Upon entering the perineum, the pudendal n gives off 2-3 midline branches that provide sensory to the anal canal. These nerves and accompanying arteries/veins traverse the ischianal fat pad en route to the rectum

46
Q

Describe the distal branches of the pudendal n:

A

After giving off the inferior rectal nn, the pudendal n runs along the lateral perineum wall, on the surface of the obturator internus m and is invested by the obturator internus fascia until it reaches the posterior border of the UG diaphragm. This region is the pudendal canal. At the posterior boundary of the UG diaphragm, the pudendal n. splits to give rise to a perineal n and dorsal n of the penis (clitoris)

47
Q

The perineal n. gives rise to:

A

Superficial (sensory) and deep (motoe) perineal nn

48
Q

The deep perineal n. branch supplies motor to:

A

Erectile tissue muscles, superficial transverse perineal m and the msucles located in the deep compartment - external urethra sphincter m and deep transversus perineal m.

49
Q

The superficial perineal branch terminates as the:

A

posterior scrotal branch (or labial) and provides sensory to these regions

50
Q

Describe the course of the dorsal nerve:

A

Enters the deep pouch on the superior surface of the UG diaphragm (piercing the superior perineal fascia) and runs along the ischiopubic rami border, almost up to the anterior border of the UG diaphragm. Along with the dorsal a, it exits the UG diaphragm by piercing the perineal membrane and then runs along the crus of the corpus cavernosum to the dorsal body of the penis

51
Q

The dorsal n and a of the penis travel between:

A

The tunic albuginea of the corpus cavernosum and the deep penile fascia of the penis (Buck’s) to provide sensory to the body and glans of the penis (clitoris)

52
Q

Describe the autonomic input to the erectile tissues:

A

Autonomic input to the erectile tissues of the penis (clitoris) is supplied by the pelvic splanchnics (pregang parasymp fibers) and sympathetics from the sacral splanchnics making up the inferior hypogastric plexus

53
Q

Both sets of autonomic fibers - pelvic and sacral splanchnics - converge as:

A

Cavernous nerves, from the inferior hypogastric plexus, and pierce the pelvis and UG diaphragms to innervate the erectile tissues in the male and female

54
Q

What is the blood supply to the perineum?

A

Branching pattern of M and F internal pudendal a are identical (w different naming).

55
Q

The internal pudendal a supplies:

A

The deep structures of the perineum. This is a branch of the internal iliac a located in the pelvis. It follows the same pathway as the pudendal n in leaving the pelvis and entering the perineum

56
Q

Once in the perineum, the internal pudendal a. gives off:

A

An inferior rectal branch and then proceeds within the pudendal canal to the free border of the UG diaphragm where it gives rise to a perineal branch (supplies sturctures within the superficial compartment) prior to piercing the deep compartment of the UG diaphragm

57
Q

In the deep compartment, the internal pudendal a gives off:

A

Deep artery of the penis/clitoris (suppies corpus cavernosum) and the dorsal a of the penis/clitoris.

58
Q

The skin of the penis and that surrounding the clitoris is supplied by:

A

External pudendal a (branch of femoral a)

59
Q

Venous branches of the internal pudendal vv mirror the arteries and all follow the return path alongside their counterparts into the internal pudendal v EXCEPT:

A

The deep dorsal v of the penis/clitoris.

60
Q

The deep dorsal v drains into the:

A

Prostatic plexus (M) and the inferior vesical plexus (F)

61
Q

The venous return of the skin surrounding the penis/clitoris is via the:

A

External pudendal v

62
Q

The female external genitalia consists of:

A

Mons pubis, labia majora, labia minora, clitoris, vestibule, bulbs of the vestibule, crura of the clitoris, vestibular gland, vaginal and urethral orifice. Named vulva or pudendum

63
Q

What is the mons pubis?

A

Rounded fatty elevation located anterior to the pubic symphysis. It consists of an underlying fatty layer of subcutaneous CT and is covered with coarse pubic hair beginning at the onset of puberty. Posterior to the mons pubis are the labia majora and minora

64
Q

What is the labia majora?

A

Two symmetrical folds of skin that provide protection for the vaginal and urethral orifices. These folds are lined with subcutaneous fat, covered with pubic hair and flank the pudendal cleft (slit between the labia majora that opens to the vestibule of the vagina). The labia majora meet anteriorly to form the anterior labial commissure but does not join posteriorly

65
Q

What is the labia minora?

A

It is paired hairless folds of skin (with little subcutaneous fat) that flanks the vestibule of the vagina. Unlike the majora, the 2 folds of the minora join anteriorly at the base of the clitoris as the anterior frenulum and posteriorly as the posterior frenulum of the labia minora

66
Q

What is the clitoris?

A

Formed by the joining of the paired corpus cavernosa. Each corpus cavernosum forms a crus (paired) which firmly attaches to the perineal membrane and ischiopubic rami.

67
Q

The corpus cavernosum is invested by:

A

A deep clitoral fascia, which is much thinner than its male counterpart.

68
Q

The crus is covered by:

A

Ischiocavernosus muscle and is invested by the deep perineal fascia

69
Q

The body of the clitoris is derived mostly from:

A

Corpus cavernosum

70
Q

What is the prepuce?

A

The body and glans of the clitoris is covered anteriorly by a wrap of skin called prepuce

71
Q

What is the vestibular bulb?

A

Male equivalent of the corpora spongiosum but unlike the male, they are paired in the female. They are located lateral to the vaginal/urethra orifice at the base of the labia minora, firmly attached to the perineal membrane and invested by a thin layer of deep clitoral fascia

72
Q

The vestibular bulbs are covered by what?

A

The bulbospongiosus muscle and invested by the deep perineal fascia

73
Q

What are the greater vestibular glands?

A

Located within the base of labia minora, posterior to the vestibular bulbs, and just lateral to the vaginal opening.

74
Q

What is the purpose of the greater vestibular glands?

A

These glands provide lubrication to the vaginal opening upon sexual stimulation. Both glands give off a short duct that opens just lateral to the vaginal opening. The external urethra orifice is located just anterior to the vaginal orifice and is contained by the labia minora

75
Q

Innervation of the female perineum?

A

R and L pudendal n.

76
Q

What does the pudendal n branch off to in the female perineum?

A

Inferior rectal n, perineal n, and dorsal n of the clitoris

77
Q

The perineal n gives rise to:

A

the superficial perineal n –> which terminates as the posterior labial n and the deep perinal n

78
Q

What does the deep perineal n. provide?

A

Motor fibers to the erectile tissue muscles in the deep compartment

79
Q

Describe the path of the dorsal n of the clitoris:

A

Enters the deep compartment and travels along the ischialpubic ramus –> pierces the perineal membrane and –> travels on the superior surface of the crus of the clitoris –> then reflects on the dorsal surface of the body of the clitoris and terminates on the glans of the clitoris

80
Q

What is the blood supply and return from female perineum?

A

Internal pudendal artery providing the inferior rectal, perineal, and dorsal artery of the clitoris

81
Q

What is the anal triangle?

A

Region that is posterior (dorsal) to the transverse line between the ischial tuberosities, flanked laterally by the sacrotuberous ligaments and posteriorly by the tip of the coccyx.

82
Q

The anal triangle contains the:

A

Ischioanal fossa, anal canal, the external anal sphincter, ischioanal fat pad, and the pudendal canal

83
Q

What does the pudendal canal allow the passage of?

A

Internal pudendal artery and vein and pudendal n (S2-4) to structures associated with the UG triangle

84
Q

What is the ischianal fossa occupied by?

A

Ischioanal fat pad - a fibrous/elastic fat mass that maintains the shape of the region surrounding the anal canal (and within the anterior recess, lateral to the birth canal)

85
Q

What makes up the roof of the ischioanal fossa?

A

Formed by the levator ani (pelvic diaphragm), which encircles the anal canal

86
Q

The walls of the ischioanal fossa are defined by:

A

The coccyx, sacrotuberous ligament, the obturator internus m and the ischiopubic rami

87
Q

What is the anterior recess?

A

The ischioanal fossa has direct communication with the recesses (paired) - a space that is bounded inferiorly by the UG diaphragm, medially by the levator ani/pelvic diaphragm, laterally by the obturator internus m/fascia and the medial surface of the ischiopubic rami and anteriorly by the body of the pubis

88
Q

What are the contents of the ischioanal fossa?

A
  1. Pudendal canal - accommodates passage (between the surface of the obturator internus m and its fascia) of the internal pudendal a and v and the pudendal n. from their entrance into the ischial anal fossa to structures associated with the UG triangle
  2. Inferior rectal a, v, n
  3. Ischioanal fat pad
89
Q

What is the anal canal?

A

Anchored at the midline by the anococcygeal ligament (posterior to the canal) and the perineal body anteriorly. The puborectalis m. and the pelvic diaphragm also maintain its position

90
Q

Sensory to the perineum:

A
  1. Ilioinguinal n (L1)
  2. Genitofemoral - genital branch (L2)
  3. Perineal branch of posterior femoral cutaneous n
91
Q

What is an episiotomy?

A

During childbirth, it may be necessary to surgically enlarge the birth canal to accommodate the delivery of the baby. To prevent damage to the pubococcygeus m. of the levator ani, a controlled incision is made (either by median incision from the posterior opening of the vagina to the external anal sphincter or by a medail/lateral incision from the posterior wall of the vagina towards the ischiopubic rami

92
Q

What 3 things do you need to consider when inserting a catheter into a male urethra?

A
  1. Select appropriate diameter of catheter - opening of the external urethral meatus has the narrowest diameter of all 3 parts of the healthy male urethra
  2. The wall of the membranous urethra (located in the deep perineal pouch) is very thin and easily torn away from the penile or prostatic urethra
  3. Penile urethra makes a 80-90 degree superior bend in the bulb of the penis. THe membranous urethra could tear away from the penile urethra causing urine to leak into the perineum

Anatomy IV (4 decks)

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