Musculoskeletal Pelvis & Perineum Overview

 
PowerPoint Handout 1: Lab 1, Musculoskeletal Pelvis & Perineum
 
The pelvis is the region of the body surrounded by a ring of bones that structurally connects the vertebral column to the lower extremity. The axial skeleton
and the appendicular skeleton both contribute bones to the pelvis.
The axial skeleton's contribution to the pelvis is the sacrum and the coccyx.
The appendicular skeleton's contribution to the pelvis is the right and left hip bones (pelvic bones or os coxae), which are joined anteriorly by the
fibrocartilaginous 
pubic symphysis
. The mature hip bones are formed by the fusion of three bones.
Ilium
Ischium
Pubis
 
Anterior
 
Posterior
 
Osseous Pelvis: Introduction
Osteology of the pelvis
Anterior superior iliac spine (ASIS)
Anterior inferior iliac spine
Pelvic brim
Sacral promontory
Sacral ala
Iliopectineal (iliopubic) line
Superior margin pubic
symphysis
Ischial spine
Ischial tuberosity
Ischiopubic ramus
Pubic arch
Pubic tubercle
Acetabulum
Obturator foramen
Pubic symphysis
It is important to note that the pubic
tubercles and the anterior superior
iliac spines are in the same vertical
plane when the pelvis is in its
anatomical position.
Ischiopubic Ramus
 
Osseous Pelvis: Features
 
Pelvic ligaments
Obturator membrane
Sacrotuberous ligament
Sacrospinous ligament
Anterior and posterior sacroiliac ligaments
Pelvic foramina whose boundaries are formed partially by ligaments
Greater sciatic foramen
Lesser sciatic foramen
Obturator canal
 
Pelvic Ligaments and Foramina
 
The 
pelvic brim
 divides the abdominopelvic cavity into the abdominal cavity superiorly and the and the pelvic cavity inferiorly.
The 
abdominal cavity 
is the space between the diaphragm and the pelvic brim (pelvic inlet).
The 
pelvic cavity 
is the space between the pelvic brim (pelvic inlet) and the muscular pelvic floor.
 
The pelvic brim divides the pelvis into two regions.
The 
greater pelvis (aka: false pelvis) 
is the space within the pelvis between the level of the
iliac crests and the pelvic brim. The space within the greater pelvis is a component of the
abdominal cavity.
The 
lesser pelvis (aka: true pelvis) 
is the space between the pelvic brim (pelvic inlet) and
the pelvic diaphragm (muscular floor of the pelvis). The space within the lesser pelvis is a
component of the pelvic cavity.
 
Pelvic Regions
 
True pelvis
 
False pelvis
 
An android (male-like) pelvis can be differentiated from a gynecoid
(female-like) pelvis by comparing the shape of the pelvic inlet, the
size and shape of the pelvic outlet, and the subpubic angle (See
Table 1).
 
Android Versus Gynecoid Pelvis
 
Table 1
 
Female
 
Male
 
The size of the lesser pelvis is important in obstetrics because it determines, to a large extent, the capacity for vaginal childbirth. Several measurements,
determined radiographically or manually during pelvic examination, are used to assess the size of the lesser pelvis and its suitability for a vaginal delivery.
The 
interspinous distance
 is the transverse distance between the ischial spines, which is typically the 
narrowest
 diameter of the birth canal.
The 
transverse diameter 
is the distance between the inner edges of the ischial tuberosities.
The 
true (anatomical) conjugate diameter
 is the distance between the sacral promontory and the most superior point on the pubic symphysis. This distance
can only be measured on radiographs.
The 
obstetrical conjugate diameter
 is the shortest distance between the sacral promontory and the pubic symphysis. This distance cannot be measured
directly during the pelvic examination but can be calculated by first determining the diagonal conjugate diameter (see below).
The 
diagonal conjugate diameter
 is the distance between the sacral promontory (palpated by the middle finger) and the anterior surface of the pubic
symphysis' inferior margin.
This distance can be determined during a pelvic examination, which is then used to calculate the obstetrical conjugate. Once the diagonal conjugate is
measured, the examiner subtracts 1.5 to 2 cm from the diagonal conjugate measurement.
 
Pelvic Measurements
 
13.5 cm
Obstetrical conjugate calculated after hand 
withdrawn.
(Example: 13.5 cm (Diagonal) – 2 cm = 11.5 cm (Obstetric)
 
Diagonal
Conjugate
 
Obstetrical
Conjugate
 
 
 
 
Pelvic muscles contribute to the walls and floor of the pelvic cavity.
Lateral walls
Obturator internus muscle
:  The obturator internus muscle inserts on the internal surface of the obturator membrane and passes through the 
lesser
sciatic foramen 
to insert on the greater trochanter of the femur. Within the pelvis, the obturator internus muscle is covered in thick fascia called the
obturator fascia.
Posterior walls
Piriformis muscle
: The proximal attachment of the piriformis muscle is on the anterior aspects of the S2-4 vertebral segments and passes through the
greater sciatic foramen 
to its distal attachment on the greater trochanter of the femur.
Floor
The 
pelvic floor (pelvic diaphragm)
 is a funnel--shaped structure composed of the following muscles: levator ani and coccygeus (next slide).
 
Pelvic
Diaphragm
 
Muscles of Pelvic Cavity
 
The following muscles form the funnel-shaped pelvic floor (pelvic
diaphragm).
Levator ani 
(consisting of 3 muscles)
Puborectalis muscle
Pubococcygeus muscle
Iliococcygeus muscle: 
(Note that the
iliococcygeus muscle has its origin on the 
tendinous arch
,
which is continuous with the obturator fascia.)
Coccygeus (ischiococcygeus) muscle
The coccygeus muscle's superior border is adjacent to the
inferior border of the piriformis muscle.
Its origin is on the ischial spine and the pelvic surface of
the sacrospinous ligament.
It inserts onto the lateral margin of coccyx and the most
inferior portion of sacrum.
 
Pelvic Floor Muscles
 
https://3d4medic.al/8K6xxapi
 
The funnel-shaped 
pelvic floor (diaphragm) 
forms a physical boundary between the 
pelvic cavity 
and the 
perineum
.
 
The 
perineum
 is a diamond-shaped region of the body wall inferior to the pelvic diaphragm between the buttocks and thighs. Its borders consist of the
following structures.
Anterior: inferior border of pubic symphysis
Anteriolateral margin: ischiopubic ramus
Posteriolateral margin: sacrotuberous ligament
Posterior: tip of coccyx
 
The 
pelvic floor 
contains openings for important structures to pass
between the pelvic cavity and the perineum.
The 
urogenital hiatus
 is an anterior opening in the pelvic floor
through which structures pass to enter the in the urogenital
triangle of the perineum. Note that different structures pass
through this hiatus in males as compared to females
In males the 
urethra
 passes from the lesser pelvis to the
perineum via the urogenital hiatus.
In females the 
urethra
 and 
vagina
 pass from the lesser
pelvis to the perineum via the urogenital hiatus.
The 
rectal hiatus (anal aperture) 
is a posterior opening of the
pelvic floor through with the anal canal passes to enter the anal
triangle region of the perineum.
 
Perineum
 
The diamond-shaped 
perineum
 can be further subdivided into two triangular regions (
urogenital triangle 
and 
anal triangle
) by an imaginary line
connecting the two ischial tuberosities. Take note that the two triangles are not in the same plane when the pelvis is in anatomical position.
The 
urogenital triangle
 is the 
anterior
 triangular region of the diamond-shaped perineum
In anatomical position, the urogenital triangle is oriented in a horizontal plane.
The urogenital triangle contains the urethra and external genitalia.
 
The 
anal triangle
 is the 
posterior
 triangular region of the diamond-shaped perineum
In anatomical position, the anal triangle is oriented in a plane that is almost vertical.
The anal triangle contains the anal canal, anus, external anal sphincter, inferior rectal nerve (branch of pudendal nerve), and the fat-filled
ischioanal fossa.
 
Anal Triangle
 
Urogenital Triangle
 
Urogenital and Anal Triangles
 
The 
perineal membrane 
is an important fascial layer 
within the urogenital triangle
.
Its attachments are on the ischial tuberosities and the ischiopubic rami.
The posterior margin of the perineal membrane is NOT attached to bone but is anchored at its midline to the 
perineal body
.
The perineal membrane creates an important boundary that separates the perineum into two spaces. (See next slide for details.)
A 
deep space (pouch) 
superior to the perineal membrane
A 
superficial space (pouch) 
inferior the perineal membrane
 
Perineal Membrane: Introduction
 
The 
perineal membrane 
separates the urogenital triangle into two pouches (spaces).
By definition, the 
deep perineal pouch (space)
 is the space located between the
perineal membrane and the fascia covering the 
inferior
 side of the pelvic floor
(diaphragm) muscles (Figure 1). However, there are many  inconsistencies in diagrams
as to what constitutes the deep perineal space. I think it is easiest to consider the deep
space as consisting of two subregions.
Fibromuscular region: This is the thin region of muscle resting on the superior
side of the perineal membrane. In older textbooks, this is a structure that was
described as the urogenital diaphragm. (Some present authors call this the
“perineal membrane.”) This region of the deep space contains skeletal muscle,
neurovascular structures, and the bulbourethral glands in males.
The anterior recess of the ischioanal fossa is an anterior continuation of the fat-
filled ischioanal fossa. The anterior recess is located between the fibromuscular
portion of the deep pouch and the levator ani muscles. The medial region of the
anterior recess is smaller in size compared to the lateral region.
The 
superficial perineal pouch (space)
 is located between the perineal membrane and
membranous superficial fascia (Colles fascia).
 
Perineal Membrane: Deep and Superficial Pouches
 
Figure 1
Figure 2
 
Colles Fascia
 
The “fibromuscular” region of the the deep pouch differs by gender.
Male deep Pouch
Deep transverse perineal muscle
Urethra
 passes through the deep space
External urethral sphincter
Bulbourethral glands
Internal pudendal artery and branches
Dorsal nerve of penis
Female Deep Pouch
Deep transverse perineal muscle
Urethra
 and 
vagina
 passes through the deep space
External urethral sphincter
Compressor urethrae muscle
Urethrovaginalis sphincter muscle
Internal pudendal artery and branches
Dorsal nerve of clitoris
 
Note on Anatomical Terminology: The perineal membrane is sometimes referred
to as the “inferior fascia of the urogenital (UG) diaphragm.” However, the UG
diaphragm is a structure now considered to no longer exist. It was described as a
single (thin) layer of skeletal muscle “sandwiched” between the deep fascia of
the pelvic diaphragm, which inferiorly is the perineal membrane and superiorly
the “superior fascia of the urogenital diaphragm." However, evidence of the
superior fascia is lacking. In addition, the external urethral sphincter (sphincter
urethrae muscle) was previously thought to be the principle content of the deep
pouch. However, the external urethral sphincter is now recognized to be
contained within the wall of the urethra and extends superiorly beyond the thin
region that was formerly identified as the urogenital diaphragm.
 
Deep Pouch
 
The following structures are located within the  male 
superficial pouch
.
The 
superficial transverse perineal muscles
 extend from the ischial tuberosities and the rami to the perineal body medially. They function to stabilize the
perineal body.
The 
root of the penis (bulb and crura) 
and 
muscles (ischiocavernosus and bulbospongiosus) 
surrounding
 
the root are in the superficial pouch.
Details of these structures will be explained in a future lab.
 
Male Superficial Pouch
Bulb + Crura = Root
surrounds crura
surrounds bulb
 
The following structures are located within the female superficial pouch.
The 
superficial transverse perineal musc
les extend from the ischial
tuberosities and the rami to the perineal body medially. They function to
stabilize the perineal body.
The 
greater vestibular (Bartholin's) 
glands
The 
bulbs of the vestibule, 
the
 crura, 
and
 muscles (ischiocavernosus and
bulbospongiosus) 
surrounding the bulb and crura are all located in the
superficial pouch.
Details of these structures will be explained in a future lab.
 
Female Superficial Pouch
 
The following neurovascular structures are located within the superficial pouch.
Perineal branches of internal pudendal artery
Perineal branches of pudendal nerve
 
Neurovascular Structures in Superficial Pouch
 
The 
perineal body 
is an important  fibromuscular structure maintaining the integrity of the pelvic floor. It is located in the midline of the body along
the posterior border of the perineal membrane where the urogenital and anal triangles meet. It is a central attachment point for the following
structures/muscles.
Perineal membrane
Anterior muscle fibers of levator ani
External anal sphincter
Bulbospongiosus muscle
External urethral sphincter
Superficial and deep transverse perineal muscles
Sphincter urethrovaginalis (females)
CLINICAL ANATOMY: 
The perineal body is especially important in women because it is the final support of the pelvic viscera. Disruption of
the perineal body can result in loss of support and prolapse of pelvic viscera.
 
Levator Ani
 
Coccygeus
 
Obturator
Internus
 
Perineal Body
 
The 
sacral plexus 
is located anterior to the piriformis muscle in the
pelvic cavity.
It is composed of the S1-S4 ventral rami that enter the pelvic
cavity by passing through the anterior sacral foramina.
The sacral plexus receives nerve fiber contributions from the
lumbar plexus via the 
lumbosacral trunk
 to form the 
lumbosacral
plexus
.
The lumbosacral trunk consists of some axons from the L4
ventral ramus and all the axons from the L5 ventral ramus.
The lumbosacral trunks enter the pelvic cavity by passing
inferiorly across the sacral alae.
 
Sacral Plexus
 
Lumbosacral plexus branches
See MSI Labs 4 and 5 to review the branches of the lumbosacral plexus that supply the lower extremity.
The pudendal nerve branches from the S2-S4 ventral rami of the sacral plexus.
It exits the pelvic cavity inferior to the piriformis muscle via the greater sciatic foramen.
It passes around the sacrospinous ligament to enter the lesser sciatic foramen.
It then courses through the ischioanal fossa along its lateral wall within the fascia of the obturator internus muscle called the pudendal (Alcock’s) canal.
Branches
The inferior rectal nerves supply the external anal sphincter and skin of perianal region inferior to pectinate line.
The perineal nerve branches from the pudendal nerve and ultimately divides into two branches.
The superficial perineal nerve branch becomes the posterior scrotal nerve (male) or labial nerves (female) providing sensation to those areas.
The deep perineal (motor) nerve branch supplies muscles of the perineum and pelvic floor (external urethral sphincter, bulbospongiosus,
ischiocavernosus, and levator ani muscles).
The pudendal continues as the dorsal nerve of the penis or clitoris, which penetrates the perineal membrane to provide sensory innervation to the
skin of the penis or clitoris.
 
Pudendal Nerve
CLINICAL ANATOMY: 
Spinal Block vs Epidural Block
A spinal block is the delivery of anesthesia into the CSF of the subarachnoid space by a single injection.
The anesthesia usually begins to take effect within 1 minute and results in anaesthetizing the body
below, and sometimes above, the site of injection. After administration, the patient may not be able to
move his or her lower extremities until the anesthetic wears off. A headache may follow the procedure,
which is most likely a result of CSF leakage at the injection site.
An epidural block is the administration of an anesthetic and analgesic into the epidural space through a
catheter. This method provides greater control of prolonged pain relief because of continuous,
controlled infusion. To anesthetize the lower extremity and pelvis, this procedure can be done in the
same location as a lumbar puncture. If the anesthesia is introduced into the sacral canal via the sacral
hiatus (caudal epidural block), only the S2-S4 nerve roots are anesthetized (birth canal, pelvic floor, and
external genitalia). This procedure spares the lower extremity, which is why it is a popular choice for
participatory child birth. However, it must be administered in advance of the actual delivery.
CLINICAL ANATOMY:
A pudendal nerve block is a common anesthesia
technique for perineal anesthesia during obstetric
procedures, including vaginal birth during the second
stage of labor, vaginal repairs, and anorectal surgeries
such as hemorrhoidectomies.  The pudendal nerve is
anesthetized where it enters the lesser sciatic
foramen, 1 cm inferior and medial relative to the
attachment of the sacrospinous ligament to the
ischial spine. This procedure can be accomplished by
the following approaches:  transvaginal (figure),
transperineal, or perirectal.
 
Spinal, Epidural, and Pudendal Blocks
Slide Note
Embed
Share

Explore the anatomy of the pelvis and perineum, including the osseous pelvis structure, features, ligaments, and pelvic regions. Learn about the division of the abdominopelvic cavity and key neurovascular structures in this comprehensive PowerPoint presentation.

  • Anatomy
  • Pelvis
  • Perineum
  • Musculoskeletal
  • Presentation

Uploaded on Mar 27, 2024 | 2 Views


Download Presentation

Please find below an Image/Link to download the presentation.

The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author. Download presentation by click this link. If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.

E N D

Presentation Transcript


  1. PowerPoint Handout 1: Lab 1, Musculoskeletal Pelvis & Perineum Slide Title Slide Number Slide Title Slide Number Perineal Membrane: Introduction Slide 12 Osseous Pelvis: Introduction Slide 2 Perineal Membrane: Deep and Superficial Pouches Slide 13 Osseous Pelvis: Features Slide 3 Deep Pouch Slide 14 Pelvic Ligaments and Foramina Slide4 Male Superficial Pouch Slide 15 Pelvic Regions Slide 5 Female Superficial Pouch Android Versus Gynecoid Pelvis Slide 16 Slide 6 Neurovascular Structures in Superficial Pouch Pelvic Measurements Slide 17 Slide 7 Perineal Body Muscles of Pelvic Cavity Slide 18 Slide 8 Sacral Plexus Pelvic Floor Muscles Slide 19 Slide 9 Pudendal Nerve Perineum Slide 20 Slide 10 Urogenital and Anal Triangles Spinal, Epidural, and Pudendal Blocks Slide 11 Slide 21

  2. Osseous Pelvis: Introduction The pelvis is the region of the body surrounded by a ring of bones that structurally connects the vertebral column to the lower extremity. The axial skeleton and the appendicular skeleton both contribute bones to the pelvis. The axial skeleton's contribution to the pelvis is the sacrum and the coccyx. The appendicular skeleton's contribution to the pelvis is the right and left hip bones (pelvic bones or os coxae), which are joined anteriorly by the fibrocartilaginous pubic symphysis. The mature hip bones are formed by the fusion of three bones. Ilium Ischium Pubis Posterior Anterior

  3. Osseous Pelvis: Features Osteology of the pelvis Anterior superior iliac spine (ASIS) Anterior inferior iliac spine Pelvic brim Sacral promontory Sacral ala Iliopectineal (iliopubic) line Superior margin pubic symphysis Ischial spine Ischial tuberosity Ischiopubic ramus Pubic arch Pubic tubercle Acetabulum Obturator foramen Pubic symphysis It is important to note that the pubic tubercles and the anterior superior iliac spines are in the same vertical plane when the pelvis is in its anatomical position. Anterior Inferior Iliac Spine Pubic Arch Iliopectineal (iliopubic) ine Ischiopubic Ramus

  4. Pelvic Ligaments and Foramina Pelvic ligaments Obturator membrane Sacrotuberous ligament Sacrospinous ligament Anterior and posterior sacroiliac ligaments Pelvic foramina whose boundaries are formed partially by ligaments Greater sciatic foramen Lesser sciatic foramen Obturator canal

  5. Pelvic Regions The pelvic brim divides the abdominopelvic cavity into the abdominal cavity superiorly and the and the pelvic cavity inferiorly. The abdominal cavity is the space between the diaphragm and the pelvic brim (pelvic inlet). The pelvic cavity is the space between the pelvic brim (pelvic inlet) and the muscular pelvic floor. The pelvic brim divides the pelvis into two regions. The greater pelvis (aka: false pelvis) is the space within the pelvis between the level of the iliac crests and the pelvic brim. The space within the greater pelvis is a component of the abdominal cavity. The lesser pelvis (aka: true pelvis) is the space between the pelvic brim (pelvic inlet) and the pelvic diaphragm (muscular floor of the pelvis). The space within the lesser pelvis is a component of the pelvic cavity. Iliac Crest False pelvis Pelvic Brim (Inlet) True pelvis

  6. Android Versus Gynecoid Pelvis An android (male-like) pelvis can be differentiated from a gynecoid (female-like) pelvis by comparing the shape of the pelvic inlet, the size and shape of the pelvic outlet, and the subpubic angle (See Table 1). Table 1 Female Male

  7. Pelvic Measurements The size of the lesser pelvis is important in obstetrics because it determines, to a large extent, the capacity for vaginal childbirth. Several measurements, determined radiographically or manually during pelvic examination, are used to assess the size of the lesser pelvis and its suitability for a vaginal delivery. The interspinous distance is the transverse distance between the ischial spines, which is typically the narrowest diameter of the birth canal. The transverse diameteris the distance between the inner edges of the ischial tuberosities. The true (anatomical) conjugate diameter is the distance between the sacral promontory and the most superior point on the pubic symphysis. This distance can only be measured on radiographs. The obstetrical conjugate diameter is the shortest distance between the sacral promontory and the pubic symphysis. This distance cannot be measured directly during the pelvic examination but can be calculated by first determining the diagonal conjugate diameter (see below). The diagonal conjugate diameter is the distance between the sacral promontory (palpated by the middle finger) and the anterior surface of the pubic symphysis' inferior margin. This distance can be determined during a pelvic examination, which is then used to calculate the obstetrical conjugate. Once the diagonal conjugate is measured, the examiner subtracts 1.5 to 2 cm from the diagonal conjugate measurement. Obstetrical Conjugate Diagonal Conjugate Obstetrical conjugate calculated after hand withdrawn. (Example: 13.5 cm (Diagonal) 2 cm = 11.5 cm (Obstetric)

  8. Muscles of Pelvic Cavity Pelvic muscles contribute to the walls and floor of the pelvic cavity. Lateral walls Obturator internus muscle: The obturator internus muscle inserts on the internal surface of the obturator membrane and passes through the lesser sciatic foramen to insert on the greater trochanter of the femur. Within the pelvis, the obturator internus muscle is covered in thick fascia called the obturator fascia. Posterior walls Piriformis muscle: The proximal attachment of the piriformis muscle is on the anterior aspects of the S2-4 vertebral segments and passes through the greater sciatic foramen to its distal attachment on the greater trochanter of the femur. Floor The pelvic floor (pelvic diaphragm) is a funnel--shaped structure composed of the following muscles: levator ani and coccygeus (next slide). Pelvic Diaphragm

  9. Pelvic Floor Muscles https://3d4medic.al/8K6xxapi The following muscles form the funnel-shaped pelvic floor (pelvic diaphragm). Levator ani (consisting of 3 muscles) Puborectalis muscle Pubococcygeus muscle Iliococcygeus muscle: (Note that the iliococcygeus muscle has its origin on the tendinous arch, which is continuous with the obturator fascia.) Coccygeus (ischiococcygeus) muscle The coccygeus muscle's superior border is adjacent to the inferior border of the piriformis muscle. Its origin is on the ischial spine and the pelvic surface of the sacrospinous ligament. It inserts onto the lateral margin of coccyx and the most inferior portion of sacrum.

  10. Perineum The funnel-shaped pelvic floor (diaphragm) forms a physical boundary between the pelvic cavity and the perineum. The perineum is a diamond-shaped region of the body wall inferior to the pelvic diaphragm between the buttocks and thighs. Its borders consist of the following structures. Anterior: inferior border of pubic symphysis Anteriolateral margin: ischiopubic ramus Posteriolateral margin: sacrotuberous ligament Posterior: tip of coccyx The pelvic floor contains openings for important structures to pass between the pelvic cavity and the perineum. The urogenital hiatus is an anterior opening in the pelvic floor through which structures pass to enter the in the urogenital triangle of the perineum. Note that different structures pass through this hiatus in males as compared to females In males the urethra passes from the lesser pelvis to the perineum via the urogenital hiatus. In females the urethra and vagina pass from the lesser pelvis to the perineum via the urogenital hiatus. rectal hiatus (anal aperture) The rectal hiatus (anal aperture) is a posterior opening of the pelvic floor through with the anal canal passes to enter the anal triangle region of the perineum.

  11. Urogenital and Anal Triangles The diamond-shaped perineum can be further subdivided into two triangular regions (urogenital triangle and anal triangle) by an imaginary line connecting the two ischial tuberosities. Take note that the two triangles are not in the same plane when the pelvis is in anatomical position. The urogenital triangle is the anterior triangular region of the diamond-shaped perineum In anatomical position, the urogenital triangle is oriented in a horizontal plane. The urogenital triangle contains the urethra and external genitalia. The anal triangle is the posterior triangular region of the diamond-shaped perineum In anatomical position, the anal triangle is oriented in a plane that is almost vertical. The anal triangle contains the anal canal, anus, external anal sphincter, inferior rectal nerve (branch of pudendal nerve), and the fat-filled ischioanal fossa. Urogenital Triangle rectal hiatus (anal aperture) Anal Triangle

  12. Perineal Membrane: Introduction The perineal membrane is an important fascial layer within the urogenital triangle. Its attachments are on the ischial tuberosities and the ischiopubic rami. The posterior margin of the perineal membrane is NOT attached to bone but is anchored at its midline to the perineal body. The perineal membrane creates an important boundary that separates the perineum into two spaces. (See next slide for details.) A deep space (pouch) superior to the perineal membrane A superficial space (pouch) inferior the perineal membrane

  13. Perineal Membrane: Deep and Superficial Pouches Figure 2 The perineal membrane separates the urogenital triangle into two pouches (spaces). By definition, the deep perineal pouch (space) is the space located between the perineal membrane and the fascia covering the inferior side of the pelvic floor (diaphragm) muscles (Figure 1). However, there are many inconsistencies in diagrams as to what constitutes the deep perineal space. I think it is easiest to consider the deep space as consisting of two subregions. Fibromuscular region: This is the thin region of muscle resting on the superior side of the perineal membrane. In older textbooks, this is a structure that was described as the urogenital diaphragm. (Some present authors call this the perineal membrane. ) This region of the deep space contains skeletal muscle, neurovascular structures, and the bulbourethral glands in males. The anterior recess of the ischioanal fossa is an anterior continuation of the fat- filled ischioanal fossa. The anterior recess is located between the fibromuscular portion of the deep pouch and the levator ani muscles. The medial region of the anterior recess is smaller in size compared to the lateral region. The superficial perineal pouch (space) is located between the perineal membrane and membranous superficial fascia (Colles fascia). Figure 1 Pelvic Diaphragm Deep Pouch (A Recess Ischioanal Fossa) Deep Pouch (Fibromuscular Region) Urogenital Diaphragm Superficial Pouch Colles Fascia Perineal Membrane

  14. Deep Pouch Male Deep Perineal Space The fibromuscular region of the the deep pouch differs by gender. Male deep Pouch Deep transverse perineal muscle Urethra passes through the deep space External urethral sphincter Bulbourethral glands Internal pudendal artery and branches Dorsal nerve of penis Female Deep Pouch Deep transverse perineal muscle Urethra and vagina passes through the deep space External urethral sphincter Compressor urethrae muscle Urethrovaginalis sphincter muscle Internal pudendal artery and branches Dorsal nerve of clitoris Female Deep Perineal Space Note on Anatomical Terminology: The perineal membrane is sometimes referred to as the inferior fascia of the urogenital (UG) diaphragm. However, the UG diaphragm is a structure now considered to no longer exist. It was described as a single (thin) layer of skeletal muscle sandwiched between the deep fascia of the pelvic diaphragm, which inferiorly is the perineal membrane and superiorly the superior fascia of the urogenital diaphragm." However, evidence of the superior fascia is lacking. In addition, the external urethral sphincter (sphincter urethrae muscle) was previously thought to be the principle content of the deep pouch. However, the external urethral sphincter is now recognized to be contained within the wall of the urethra and extends superiorly beyond the thin region that was formerly identified as the urogenital diaphragm. External Urethral Sphincter

  15. Male Superficial Pouch The following structures are located within the male superficial pouch. The superficial transverse perineal muscles extend from the ischial tuberosities and the rami to the perineal body medially. They function to stabilize the perineal body. The root of the penis (bulb and crura) and muscles (ischiocavernosus and bulbospongiosus) surroundingthe root are in the superficial pouch. Details of these structures will be explained in a future lab. Bulb + Crura = Root surrounds crura surrounds bulb

  16. Female Superficial Pouch The following structures are located within the female superficial pouch. The superficial transverse perineal muscles extend from the ischial tuberosities and the rami to the perineal body medially. They function to stabilize the perineal body. The greater vestibular (Bartholin's) glands The bulbs of the vestibule, the crura, and muscles (ischiocavernosus and bulbospongiosus) surrounding the bulb and crura are all located in the superficial pouch. Details of these structures will be explained in a future lab.

  17. Neurovascular Structures in Superficial Pouch The following neurovascular structures are located within the superficial pouch. Perineal branches of internal pudendal artery Perineal branches of pudendal nerve

  18. Perineal Body The perineal body is an important fibromuscular structure maintaining the integrity of the pelvic floor. It is located in the midline of the body along the posterior border of the perineal membrane where the urogenital and anal triangles meet. It is a central attachment point for the following structures/muscles. Perineal membrane Anterior muscle fibers of levator ani External anal sphincter Bulbospongiosus muscle External urethral sphincter Superficial and deep transverse perineal muscles Sphincter urethrovaginalis (females) CLINICAL ANATOMY: The perineal body is especially important in women because it is the final support of the pelvic viscera. Disruption of the perineal body can result in loss of support and prolapse of pelvic viscera. Coccygeus Obturator Internus Levator Ani

  19. Sacral Plexus The sacral plexus is located anterior to the piriformis muscle in the pelvic cavity. It is composed of the S1-S4 ventral rami that enter the pelvic cavity by passing through the anterior sacral foramina. The sacral plexus receives nerve fiber contributions from the lumbar plexus via the lumbosacral trunk to form the lumbosacral plexus. The lumbosacral trunk consists of some axons from the L4 ventral ramus and all the axons from the L5 ventral ramus. The lumbosacral trunks enter the pelvic cavity by passing inferiorly across the sacral alae.

  20. Pudendal Nerve Lumbosacral plexus branches See MSI Labs 4 and 5 to review the branches of the lumbosacral plexus that supply the lower extremity. The pudendal nerve branches from the S2-S4 ventral rami of the sacral plexus. It exits the pelvic cavity inferior to the piriformis muscle via the greater sciatic foramen. It passes around the sacrospinous ligament to enter the lesser sciatic foramen. It then courses through the ischioanal fossa along its lateral wall within the fascia of the obturator internus muscle called the pudendal (Alcock s) canal. Branches The inferior rectal nerves supply the external anal sphincter and skin of perianal region inferior to pectinate line. The perineal nerve branches from the pudendal nerve and ultimately divides into two branches. The superficial perineal nerve branch becomes the posterior scrotal nerve (male) or labial nerves (female) providing sensation to those areas. The deep perineal (motor) nerve branch supplies muscles of the perineum and pelvic floor (external urethral sphincter, bulbospongiosus, ischiocavernosus, and levator ani muscles). The pudendal continues as the dorsal nerve of the penis or clitoris, which penetrates the perineal membrane to provide sensory innervation to the skin of the penis or clitoris.

  21. Spinal, Epidural, and Pudendal Blocks CLINICAL ANATOMY: Spinal Block vs Epidural Block A spinal block is the delivery of anesthesia into the CSF of the subarachnoid space by a single injection. The anesthesia usually begins to take effect within 1 minute and results in anaesthetizing the body below, and sometimes above, the site of injection. After administration, the patient may not be able to move his or her lower extremities until the anesthetic wears off. A headache may follow the procedure, which is most likely a result of CSF leakage at the injection site. An epidural block is the administration of an anesthetic and analgesic into the epidural space through a catheter. This method provides greater control of prolonged pain relief because of continuous, controlled infusion. To anesthetize the lower extremity and pelvis, this procedure can be done in the same location as a lumbar puncture. If the anesthesia is introduced into the sacral canal via the sacral hiatus (caudal epidural block), only the S2-S4 nerve roots are anesthetized (birth canal, pelvic floor, and external genitalia). This procedure spares the lower extremity, which is why it is a popular choice for participatory child birth. However, it must be administered in advance of the actual delivery. CLINICAL ANATOMY: A pudendal nerve block is a common anesthesia technique for perineal anesthesia during obstetric procedures, including vaginal birth during the second stage of labor, vaginal repairs, and anorectal surgeries such as hemorrhoidectomies. The pudendal nerve is anesthetized where it enters the lesser sciatic foramen, 1 cm inferior and medial relative to the attachment of the sacrospinous ligament to the ischial spine. This procedure can be accomplished by the following approaches: transvaginal (figure), transperineal, or perirectal.

Related


More Related Content

giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#