Handout Urogenital Muscle and Bones part 1

Handout Urogenital Muscle and Bones part 1

1. Slide Title Slide Number
Osseous Pelvis: Introduction Slide 2
Osseous Pelvis: Features Slide 3
Pelvic Ligaments and Foramina Slide4
Pelvic Regions Slide 5
Android Versus Gynecoid Pelvis Slide 6
Pelvic Measurements Slide 7
Muscles of Pelvic Cavity Slide 8
Pelvic Floor Muscles Slide 9
Perineum Slide 10
Urogenital and Anal Triangles Slide 11
Slide Title Slide Number
Perineal Membrane: Introduction Slide 12
Perineal Membrane: Deep and Superficial Pouches Slide 13
Deep Pouch Slide 14
Male Superficial Pouch Slide 15
Female Superficial Pouch Slide 16
Neurovascular Structures in Superficial Pouch Slide 17
Perineal Body Slide18
Sacral Plexus Slide 19
Pudendal Nerve Slide 20
Spinal, Epidural, and Pudendal Blocks Slide 21
PowerPoint Handout 1: Lab 1, Musculoskeletal Pelvis & Perineum

2. 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 thesacrumand thecoccyx.
•The appendicular skeleton's contribution to the pelvis is theright and left hip bones (pelvic bones or os coxae), which are joined anteriorly by the
fibrocartilaginouspubic symphysis.The mature hip bones are formed by the fusion of three bones.
•Ilium
•Ischium
•Pubis
AnteriorPosterior
Osseous Pelvis: Introduction

3. 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
Ischiopubic Ramus
Osseous Pelvis: Features
Il iopecti neal (ili opubic)
ine

4. 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

5. Thepelvic brimdivides the abdominopelvic cavity into theabdominal cavitysuperiorly and the and thepelvic cavityinferiorly.
•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.
•Thegreater 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.
•Thelesser pelvis (aka: true pelvis)is the spacebetween the pelvic brim (pelvic inlet) and
thepelvic diaphragm(muscular floor of the pelvis). The space within the lesser pelvis is a
component of the pelvic cavity.
Pelvic
Brim (Inlet)
Iliac
Crest
Pelvic Regions
True pelvis
False pelvis

6. 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

7. 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.
•Theinterspinous distanceis the transverse distance between the ischial spines, which is typically the narrowest diameter of the birth canal.
•Thetransverse diameteris the distance between the inner edges of the ischial tuberosities.
•Thetrue (anatomical) conjugate diameteris the distance between the sacral promontory and the most superior point on the pubic symphysis. This distance
can only be measured on radiographs.
•Theobstetrical conjugate diameteris 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).
•Thediagonal conjugate diameteristhe 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 theobstetricalconjugate. Once the diagonalconjugate is
measured, the examinersubtracts 1.5 to 2 cm from thediagonal conjugate measurement.
Pelvic Measurements
Obstetrical conjugate calculated after hand withdrawn.
(Example: 13.5 cm (Diagonal) – 2 cm = 11.5 cm (Obstetric)
Diagonal
Conjugate
Obstetrical
Conjugate

8. Pelvic muscles contribute to the walls and floor of the pelvic cavity.
•Lateral walls
•Obturator internusmuscle: 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 thefollowing muscles: levator ani and coccygeus (next slide).
Pelvic
Diaphragm
Muscles of Pelvic Cavity

9. 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
iliococcygeusmusclehas its origin on thetendinous 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

10. 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.
•Theurogenital hiatusis 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.
rectal hiatus
(anal aperture)
Perineum

11. 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.
•Theurogenital triangleis 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.
•Theanal triangleis 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.
rectal hiatus
(anal aperture)
Anal Triangle
Urogenital Triangle
Urogenital and Anal Triangles

12. 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

13. The perineal membrane separates the urogenital triangle into two pouches (spaces).
•By definition, thedeep 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
Pelvic Diaphragm
Superficial Pouch
Deep Pouch (Fibromuscular Region)
“Urogenital Diaphragm”
Deep Pouch (A Recess Ischioanal Fossa)
Perineal Membrane
Figure 1
Figure 2
Colles Fascia

14. 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, whichinferiorly 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
Female Deep Perineal Space
Male Deep Perineal SpaceDeep Pouch

15. The following structures are located within the male superficial pouch.
•Thesuperficial transverse perineal musclesextend from the ischial tuberosities and the rami to the perineal body medially. They function to stabilize the
perineal body.
•Therootof 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

16. The following structures are located within the female superficial pouch.
•Thesuperficial transverse perineal musclesextend from the ischial
tuberosities and the rami to the perineal body medially. They function to
stabilize the perineal body.
•Thegreater vestibular (Bartholin's) glands
•Thebulbsof 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

17. 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

18. 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

19. 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

20. 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

21. 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