Pelvis

Identify the following bones, bony landmarks, joints, and ligaments of the pelvis:

Ilium

אנטומיה - הגפה התחתונה (1): אגן ומפרק הירך

Anterior Superior Iliac Spine (ASIS):

○ prominent projection at the anterior

end of the iliac crest.

■ Identifying the inguinal ligament,

which attaches here.

■ Locating the McBurney’s point,

used in diagnosing appendicitis.

■ Measuring leg length or aligning

surgical incisions.

● Anterior Inferior Iliac Spine (AIIS):

○ Located just below the ASIS

○ Site for muscle attachment (rectus

muscle - part of the

quadriceps) and the

ligament, one of the strongest

ligaments in the body.

—ASIS-

Palpable hip landmark
Attachment of the inguinal ligament
Used to find McBurney's point
Used to measure leg length

AIIS
- Located just inferior to the ASIS
- Origin of the rectus femoris
- Attachment of the iliofemoral ligament
- Important for hip stability and hip flexion

Iliac Crest:
○ the superior border that supplies
attachment for several
abdominal muscles and the
latissimus dorsi
● Posterior Superior Iliac Spine (PSIS):
○ posterior end of the iliac crest
○ Helpful in Identifying the
sacroiliac joint.
● Posterior Inferior Iliac Spine (PIIS):
○ Attachment site for the
sacrospinous ligament, which
helps stabilize the sacroiliac
joint.

Iliac Crest = Top ridge; attachment for abdominal muscles and latissimus dorsi; landmark for L4.
PSIS = Back upper bump; helps locate the sacroiliac joint.
PIIS = Back lower bump; attachment for a stabilizing pelvic ligament.

Ischium-The ischium is the lower back part of the hip bone.

It's the "sit bone" because it bears your weight when you're sitting.

Detailed Study Materials on Hip and Thigh Anatomy and Pathology Flashcards | Quizlet

Ischial tuberosity

○ Serves as the attachment site for several

important structures, including

hamstrings and sacrospinous ligaments

■ This is where the Hamstrings attach.

○ Supports body weight when sitting.

● Ischial Spine:

○ Sharp, bony projection located superior

to the ischial tuberosity.

○ Attachment of sacrospinous ligament

■ Helps convert the greater sciatic

notch into the greater sciatic

foramen

Ischial tuberosity
- "Sit bone"
- Supports body weight while sitting
- Origin of the hamstrings
- Common site of hamstring avulsion and ischial bursitis
Ischial spine
- Sharp projection superior to the tuberosity
- Attachment for the sacrospinous ligament
- Helps form the greater sciatic foramen
- Important landmark for assessing fetal station during labor

Pubic-

Pubic Crest:

○ Thickened anterior border of the pubic

bone.

○ Attachment site for the rectus abdominis

muscle and the inguinal ligament.

● Pubic Tubercle:

○ A small, palpable projection located

lateral to the pubic symphysis.

● Pectineal Line:

○ A sharp ridge on the superior ramus of

the pubis.

○ Attachment site for the pectineus muscle

and contributes to the pelvic brim.

Pubic Crest
- Thickened anterior border of the pubis
- Attachment for the rectus abdominis
- Near the attachment of the inguinal ligament
Pubic Tubercle
- Small palpable bump lateral to the pubic symphysis
- Medial attachment of the inguinal ligament
- Landmark for inguinal hernias
Pectineal Line
- Ridge on the superior pubic ramus
- Attachment for the pectineus muscle
- Forms part of the pelvic brim, dividing the false and true pelvis
- Sacrum / Coccyx

Week 2C: Sacral Vertebrae Flashcards | Quizlet

Sacrum:

○ Triangular bone formed by the fusion of five sacral

vertebrae.

○ Sacral Promontory:

■ Landmark in obstetrics for measuring pelvic

dimensions.

○ Sacral Canal: Houses the cauda equina

■ Used for epidural anesthesia.

○ Sacral Foramina: Allow passage of the sacral

nerves.

○ Median Sacral Crest: Provides attachment for

ligaments and muscles.

● Coccyx:

○ A small, triangular bone formed by the fusion of

three to five rudimentary vertebrae.

○ It provides attachment for the levator ani .

Sacrum
- Five fused vertebrae (S1–S5)
- Connects the spine to the pelvis and transmits body weight
Sacral Promontory
- Landmark used in obstetrics to assess pelvic size
Sacral Canal
- Contains the cauda equina
- Site for caudal epidural anesthesia
Sacral Foramina
- Openings for the sacral spinal nerves
Median Sacral Crest
- Posterior ridge for muscle and ligament attachment
Coccyx
- Fused tailbone (3–5 vertebrae)
- Attachment for the levator ani, an important pelvic floor muscle
- Can become painful after trauma (coccydynia)

Pubic Symphysis:

The pubic symphysis is a cartilaginous joint that connects the left and right pubic bones.

Symphysis Pubis Dysfunction (SPD) - Symptoms, Causes & Training Tips

A cartilaginous joint that connects

the two pubic bones

● Provides stability to the pelvic ring

● Allows slight movement during

activities like walking or childbirth.

Acetabulum: The acetabulum is a deep, cup-shaped socket on the outside (lateral side) of the pelvis.

Its job is to hold the head of the femur, forming the hip joint.

Deep, cup-shaped socket on the outer

pelvis that holds the head of the femur

(thighbone) to form the hip joint

● Formed by the fusion of all three pelvic

bones

● Crucial for weight-bearing and stability

Sacrospinous ligament:

Runs from the ischial spine to the lateral

sacrum.

● It converts the greater sciatic notch into

the greater sciatic foramen

○ This is the passage of the sciatic

nerve, pudendal nerve, and

piriformis muscle.

● It also opposes nutation (forward

rotation of the sacrum) during weight-

bearing and gait.

Feature	Description
Attachment	Ischial spine → lateral sacrum
Main function	Converts the greater sciatic notch into the greater sciatic foramen
Structures passing through	Sciatic nerve, pudendal nerve, piriformis muscle (among others)
Additional role	Stabilizes the pelvis and resists excessive sacral nutation during standing and walking

Sacrotuberous ligament:

The sacrotuberous ligament is a strong ligament that connects the:

Sacrum → Ischial tuberosity ("sit bone")

This ligament runs from the sacrum to

the ischial tuberosity.

● It converts the lesser sciatic notch into

the lesser sciatic foramen

○ which allows passage of the

internal pudendal nerve, artery,

and vein, as well as the tendon of

the obturator internus muscle.

○It resists nutation and prevents

excessive movement of the

sacrum.

Sacrospinous	Sacrotuberous
Goes to ischial spine	Goes to ischial tuberosity (sit bone)
Makes greater sciatic foramen	Makes lesser sciatic foramen
Higher	Lower

Identify the major foramen of the pelvic cavity and their contents and accurately categorize the neurovascular and muscular structures that traverse each opening

Obturator foramen:

Transobturator Approach For Cystocele Repair With Anterior Wall Mesh | Contemporary OB/GYN

Covered by the obturator

membrane

● Allows passage of the

obturator nerve, artery,

and vein.

Only three important structures travel through the obturator canal:

Obturator nerve → supplies the medial (inner thigh) muscles and sensation to part of the inner thigh.
Obturator artery → brings blood to the medial thigh.
Obturator vein → drains blood from the medial thigh.

Greater Sciatic notch: The greater sciatic foramen is a large opening in the back of the pelvis. It is the main exit from the pelvis to the buttock and lower limb.

PPT - Gluteal Region PowerPoint Presentation, free download - ID:3036676

Lesser sciatic notch
Pelvic inlet and outlet

Identify the contents of the pelvic cavity
Define the spaces of the urogenital triangle and describe the contents within the superficial and deep perineal pouch
Identify the following pelvic muscles, innervation and the corresponding actions
1. Muscles of the pelvic walls
  1. Obturator internus muscles
  2. Piriformis muscles
2. Muscles of the pelvic diaphragm
  1. Levator Ani
  2. Coccygeus muscles
3. Peroneal muscles
  1. Bulbospongiosus
  2. Ischiocavernosus
Identify the following pelvic vasculature
1. Anterior trunk of the internal iliac
  1. Obliterated umbilical artery
  2. Obturator artery
  3. Uterine artery
  4. Inferior vesical artery
  5. Vaginal artery (not in males)
  6. Middle rectal artery
  7. Internal pudendal artery
    1. Penile artery
  8. Inferior gluteal artery
2. Posterior trunk of the internal iliac
  1. Iliolumbar artery
  2. Lateral sacral artery
  3. Superior gluteal artery
3. Lymphatic nodes
  1. Superficial inguinal nodes
  2. Deep inguinal nodes
Identify the location and innervations of the pelvis
1. Sacral plexus
  1. Superior and inferior gluteal nerve
  2. Pudendal nerve
  3. Sciatic nerve
2. Autonomic innervation
  1. Sacral sympathetic trunk
  2. Pelvic Splanchnic nerves
  3. Hypogastric plexus
Identify the location, anatomical features, subdivisions, and innervations of the following structures:
1. Genitourinary System
  1. Bladder
  2. Urethra: differences between male and female anatomy, urethral sphincters
2. Gastrointestinal System
  1. Rectum
  2. Anus / Anal Canal: Pectinate line, Anal sphincter
3. Male Genitalia
  1. Penis
    1. Glans penis,
    2. Body: Corpus Spongiosum, Corpora cavernosa
    3. Root: Bulb of the penis, Crura of the penis
  2. Scrotum
    1. Testes: Seminiferous tubules
    2. Epididymis
    3. Dartos and cremaster muscle
  3. Ductus (Vas) deferens
  4. Ejaculatory ducts
  5. Seminal vesicles
  6. Prostate gland
  7. Bulbourethral glands
4. Female Genetalia
  1. Ovaries
  2. Uterus
    1. Uterine (Fallopian) Tubes
    2. Cervix
  3. Vagina
  4. External genitalia:
    1. Mons pubis
    2. Labia majora and minora
    3. Clitoris
    4. Vestibule
    5. Greater vestibular (Bartholin) gland
  5. Ligaments: Broad, Round, Ovarian, Suspensory, Cardinal ligaments

Identify the following bones, bony landmarks, joints, and ligaments of the pelvis:

Ilium

Structure	What You Need to Know	Clinical Importance
Ilium	Largest part of the hip bone. Contains important landmarks: ASIS, AIIS, Iliac Crest, PSIS, PIIS.	Important for identifying ligaments, muscle attachments, and surgical landmarks.
ASIS (Anterior Superior Iliac Spine)	Prominent projection at the anterior end of the iliac crest.	• Attachment of the inguinal ligament. • Used to locate McBurney's point. • Used to measure leg length and align surgical incisions.
AIIS (Anterior Inferior Iliac Spine)	Located just below the ASIS.	Attachment for the rectus femoris muscle and iliofemoral ligament.
Iliac Crest	Superior border of the ilium.	Attachment for several abdominal muscles and the latissimus dorsi.
PSIS (Posterior Superior Iliac Spine)	Posterior end of the iliac crest.	Helpful landmark for identifying the sacroiliac joint.
PIIS (Posterior Inferior Iliac Spine)	Inferior to the PSIS.	Attachment site for the sacrospinous ligament, helping stabilize the sacroiliac joint.

B. Ischium:

Structure	Description / Identification	Clinical Importance
Ischium	Inferior and posterior portion of the hip bone.	Contains the ischial spine and ischial tuberosity.
Ischial Tuberosity	Attachment site for the hamstrings and sacrospinous ligament. Supports body weight while sitting.	Common site for ischial bursitis and hamstring tendon injuries.
Ischial Spine	Sharp projection superior to the ischial tuberosity. Attachment of the sacrospinous ligament. Converts the greater sciatic notch into the greater sciatic foramen.	Landmark used in obstetrics to assess labor because it marks the narrowest part of the pelvic outlet.

Structure

Description / Identification

Clinical Importance

Ischium

Inferior and posterior portion of the hip bone.

Contains the ischial spine and ischial tuberosity.

Ischial Tuberosity

Attachment site for the hamstrings and sacrospinous ligament. Supports body weight while sitting.

Common site for ischial bursitis and hamstring tendon injuries.

Ischial Spine

Sharp projection superior to the ischial tuberosity. Attachment of the sacrospinous ligament.

Converts the greater sciatic notch into the greater sciatic foramen.

Landmark used in obstetrics to assess labor because it marks the narrowest part of the pelvic outlet.

PUBIS

Structure	Description / Identification
Pubis	Anterior portion of the hip bone.
Pubic Crest	Thickened anterior border of the pubic bone. Attachment for the rectus abdominis and inguinal ligament.
Pubic Tubercle	Small palpable projection lateral to the pubic symphysis.
Pectineal Line	Sharp ridge on the superior pubic ramus. Attachment for the pectineus muscle and contributes to the pelvic brim.

Sacrum / Coccyx

Sacrum: MedlinePlus Medical Encyclopedia Image

Structure	Description / Identification
Sacrum	Triangular bone formed by fusion of five sacral vertebrae.
Sacral Promontory	Landmark used for measuring pelvic dimensions in obstetrics.
Sacral Canal	Houses the cauda equina; used for epidural anesthesia.
Sacral Foramina	Allow passage of the sacral nerves.
Median Sacral Crest	Attachment site for ligaments and muscles.

Pubic Symphysis

Structure	Description / Identification	Clinical Importance
Pubic Symphysis	Cartilaginous joint connecting the two pubic bones. Provides stability to the pelvic ring and allows slight movement during walking and childbirth.	Pregnancy hormones increase flexibility, which may lead to Symphysis Pubis Dysfunction (SPD) causing pain and instability.

Structure

Description / Identification

Clinical Importance

Pubic Symphysis

Cartilaginous joint

connecting the two pubic bones. Provides stability to the pelvic ring and allows slight movement during walking and childbirth.

Pregnancy hormones increase flexibility, which may lead to Symphysis Pubis Dysfunction (SPD) causing pain and instability.

Acetabulum

Structure	Description / Identification
Acetabulum	Deep, cup-shaped socket on the outer pelvis that holds the head of the femur to form the hip joint. Formed by the fusion of the ilium, ischium, and pubis. Crucial for weight-bearing and stability.

Structure

Description / Identification

Acetabulum

Deep, cup-shaped socket on the outer pelvis that holds the head of the femur to form the hip joint.

Formed by the fusion of the ilium, ischium, and pubis. Crucial for weight-bearing and stability.

Sacrotuberous Ligament

Feature	Description
Attachments	Runs from the sacrum to the ischial tuberosity.
Function	Converts the lesser sciatic notch into the lesser sciatic foramen.
Structures Passing Through	• Internal pudendal nerve • Internal pudendal artery and vein • Tendon of the obturator internus muscle
Additional Function	Resists nutation and prevents excessive movement of the sacrum.

Sacrospinous Ligament

Feature	Description
Attachments	Runs from the ischial spine to the lateral sacrum.
Function	Converts the greater sciatic notch into the greater sciatic foramen.
Structures Passing Through	• Sciatic nerve •Pudendal nerve • Piriformis muscle
Additional Function	Opposes nutation (forward rotation of the sacrum) during weight-bearing and gait.

High Yield

Objective	Know These Structures
a. Ilium	ASIS, AIIS, Iliac Crest, PSIS, PIIS
b. Ischium	Ischial Tuberosity, Ischial Spine
c. Pubis	Pubic Crest, Pubic Tubercle, Pectineal Line
d. Sacrum/Coccyx	Sacral Promontory, Sacral Canal, Sacral Foramina, Median Sacral Crest, Coccyx
e. Pubic Symphysis	Cartilaginous joint connecting both pubic bones
f. Acetabulum	Hip socket formed by all three pelvic bones
g. Sacrotuberous Ligament	Sacrum → Ischial Tuberosity → Forms Lesser Sciatic Foramen
h. Sacrospinous Ligament	Ischial Spine → Sacrum → Forms Greater Sciatic Foramen

Identify the Major Foramen of the Pelvic Cavity and Their Contents

Obturator Foramen:

Feature	Information
Location/Description	Large opening in the pelvic bone that is covered by the obturator membrane.
Neurovascular Structures	• Obturator nerve • Obturator artery • Obturator vein
Muscular Structures

Feature

Information

Location/Description

Large opening in the pelvic bone that is covered by the obturator membrane.

Neurovascular Structures

• Obturator nerve

• Obturator artery

• Obturator vein

Muscular Structures

Greater Sciatic Notch (Greater Sciatic Foramen)

Category	Information
Formation	Formed by the sacrotuberous ligament, sacrococcygeal ligaments, ilium, and sacrum/coccyx.
Mnemonic (PDF)	"I Prefer Queens of Siam"
Neurovascular Structures	• Inferior gluteal nerve • Pudendal nerve • Sciatic nerve • Posterior femoral cutaneous nerve
Muscular Structures	• Piriformis muscle • Nerve to quadratus femoris • Nerve to obturator internus
Additional Information	Shape and size of the greater sciatic notch vary between individuals and may be used in forensic anthropology to estimate sex.

Lesser Sciatic Notch (Lesser Sciatic Foramen)

Category	Information
Formation	Formed by the sacrotuberous ligament, sacrococcygeal ligaments, ilium, and sacrum/coccyx.
Mnemonic (PDF)	"POO"
Neurovascular Structures	• Internal pudendal nerve • Internal pudendal artery • Internal pudendal vein
Muscular Structures	• Obturator internus tendon• Nerve to obturator internus

Pelvic Inlet

Category	Information
Also Called	Pelvic brim / Superior pelvic aperture
Description	Superior opening of the pelvic cavity.
Formed By	• Sacral promontory• Arcuate line of the ilium• Pectineal line of the pubis• Pubic symphysis• Pubic crest
Neurovascular Structures Passing Through	Not listed in the PDF
Muscular Structures Passing Through	Not listed in the PDF

Pelvic Outlet

Category	Information
Also Called	Inferior pelvic aperture
Description	Inferior opening of the pelvic cavity.
Formed By	• Coccyx• Ischial tuberosities• Pubic symphysis
Neurovascular Structures Passing Through	Not listed in the PDF
Muscular Structures Passing Through	Not listed in the PDF

Contents of the Pelvic Cavity

Structure	Description / Function (from PDF)
Urinary Bladder	Organ of the urinary system located within the pelvic cavity.
Ureters	Tubes that enter the pelvic cavity and connect to the urinary bladder.
Pelvic Genital Organs	Reproductive organs located within the pelvic cavity.
Rectum	Terminal portion of the gastrointestinal tract located within the pelvic cavity.
Blood Vessels	Pelvic arteries and veins supplying the pelvic organs.
Lymphatics	Lymphatic vessels located throughout the pelvic cavity.
Nerves	Pelvic nerves supplying the pelvic organs and surrounding structures.

Define the spaces of the urogenital triangle and describe the contents within the superficial and deep perineal pouch

Urogenital Triangle:

Category	Information
Location	Anterior portion of the perineum.
Function	Contains the external genitalia and the openings of the urogenital system.
Spaces	• Superficial Perineal Pouch (Space) • Deep Perineal Pouch (Space)

Category

Information

Location

Anterior portion of the perineum.

Function

Contains the external genitalia and the openings of the urogenital system.

Spaces

• Superficial Perineal Pouch (Space)

• Deep Perineal Pouch (Space)

Superficial Perineal Pouch (Space)

Category	Information
Definition	A potential space located between the perineal membrane (superiorly) and the superficial fascia of the perineum (inferiorly).
Location	Between the pubic symphysis and ischial tuberosities.

Contents of the Superficial Perineal Pouch

Category	Structures
External Genitalia	Root of the penis (male) / clitoris (female)
Perineal Muscles	• Bulbospongiosus muscle • Ischiocavernosus muscle • Superficial transverse perineal muscle
Neurovascular Structures	• Internal pudendal artery • Internal pudendal vein • Pudendal nerve

Category

Structures

External Genitalia

Root of the penis (male) / clitoris (female)

Perineal Muscles

• Bulbospongiosus muscle

• Ischiocavernosus muscle

• Superficial transverse perineal muscle

Neurovascular Structures

• Internal pudendal artery

• Internal pudendal vein

• Pudendal nerve

Deep Perineal Pouch (Space)

Category	Information
Definition	A true space located between the perineal membrane (inferiorly) and the inferior fascia of the pelvic diaphragm (superiorly).

Contents of the Deep Perineal Pouch

Category	Structures
Urinary Structures	• Urethra
Muscles	• External urethral sphincter• Urethrovaginal sphincter (females)
Glands	• Cowper's (Bulbourethral) glands (males)
Neurovascular Structures	• Internal pudendal artery• Internal pudendal vein• Pudendal nerve

Perineal Membrane

Feature	Information
Definition	Strong fibrous sheet of connective tissue that stretches across the urogenital triangle.
Function	Separates the superficial and deep perineal pouches.
Location	Lies between the levator ani muscle and the superficial perineal pouch.
Attachments	Extends from the ischiopubic rami to the pubic symphysis.

Perineal Body

Feature	Information
Location	Midpoint at the junction of the urogenital triangle and the anal triangle.
Function	Serves as the convergence point for several pelvic floor muscles.
Importance	Supports the urethral and anal sphincters, contributing to urinary and fecal continence.

Comparison of the Two Perineal Pouches

Feature	Superficial Perineal Pouch	Deep Perineal Pouch
Type of Space	Potential space	True space
Boundaries	Between the perineal membrane and superficial fascia	Between the perineal membrane and inferior fascia of the pelvic diaphragm
Contains	Root of penis/clitoris	Urethra
	Bulbospongiosus muscle	External urethral sphincter
	Ischiocavernosus muscle	Urethrovaginal sphincter (female)
	Superficial transverse perineal muscle	Bulbourethral (Cowper's) glands (male)
	Internal pudendal artery & vein	Internal pudendal artery & vein
	Pudendal nerve	Pudendal nerve

Identify the following pelvic muscles, innervation and the corresponding actions
1. Muscles of the pelvic walls
  1. Obturator internus muscles
  2. Piriformis muscles

i. Obturator Internus Muscle

Category	Information
Location	Muscle of the pelvic wall.
Origin	Margins of the obturator foramen, obturator membrane, ischial ramus, and pubic ramus.
Insertion	Greater trochanter of the femur.
Innervation	Nerve to the obturator internus.
Actions	• External rotation of the hip • Abduction of the hip when the hip is flexed • Stabilization of the hip
Clinical Correlation	The pudendal nerve passes near the obturator internus as it exits the pelvis through the lesser sciatic foramen. Compression or irritation can lead to pudendal neuralgia, causing chronic perineal pain.

ii. Piriformis Muscle

Category	Information
Location	Muscle of the pelvic wall.
Origin	Anterior surface of the sacrum and the gluteal surface of the ilium near the iliac spine.
Insertion	Greater trochanter of the femur.
Innervation	Nerve to piriformis.
Actions	• External rotation of the hip • Abduction of the hip when the hip is flexed • Stabilizes the head of the femur in the acetabulum
Clinical Correlation	Piriformis syndrome: Compression or irritation of the sciatic nerve by the piriformis muscle can produce sciatica-like pain in the buttock and leg.

Comparison Table

Feature	Obturator Internus	Piriformis
Origin	Obturator foramen, obturator membrane, ischial ramus, pubic ramus	Anterior sacrum and gluteal surface of ilium
Insertion	Greater trochanter of femur	Greater trochanter of femur
Innervation	Nerve to obturator internus	Nerve to piriformis
Primary Actions	External rotation, hip abduction (when flexed), stabilization	External rotation, hip abduction (when flexed), stabilization of femoral head
Clinical Correlation	Pudendal neuralgia	Piriformis syndrome (sciatic nerve compression)

Muscles of the Pelvic Diaphragm

Feature	Information
Forms	The pelvic floor (funnel-shaped pelvic diaphragm).
Components	Levator ani and coccygeus muscles, along with their fascia.
Extent	Stretches from the pubis (anteriorly) to the coccyx (posteriorly) and from one lateral pelvic wall to the other.
Clinical Correlation	Repetitive stress (such as labor and delivery) can stretch and damage the levator ani muscles, resulting in pelvic floor insufficiency, uterine prolapse, and urinary incontinence.

I. Levator Ani

Component	Origin	Insertion
Pubococcygeus	Back of the pubic bone and anterior part of the obturator fascia	Coccyx, sacrum, and the tendinous center of the perineum
Iliococcygeus	Fascia of the obturator internus muscle	Coccyx and the anococcygeal raphe
Puborectalis	Lower part of the pubic symphysis and the superior fascia of the urogenital diaphragm	Forms a sling around the rectum, creating the anorectal angle, which is critical for maintaining fecal continence.

Summary:

Category	Information
Innervation	Not specified in the PDF.
Actions	• Supports the pelvic floor through its three muscle components.• Puborectalis forms the anorectal angle, which is essential for fecal continence.
Clinical Correlation	Weakness of the levator ani can lead to Pelvic Organ Prolapse (POP), commonly seen in postmenopausal women or after multiple vaginal births.

II. Coccygeus (Ischiococcygeus) Muscle

Category	Information
Origin	Ischial spine and bony projection of the ischium
Insertion	Inferior end of the sacrum and the coccyx
Innervation	Anterior rami of spinal nerves S4 and S5
Actions	• Supports the posterior part of the pelvic floor • Stabilizes the pelvic floor, helping maintain the position of the pelvic organs • Flexion of the coccyx (important during defecation and childbirth)
Clinical Correlation	Pelvic floor muscle dysfunction can pull on the coccyx and cause coccyx pain, which may improve with pelvic floor physical therapy.

Comparison Table:

Feature	Levator Ani	Coccygeus
Location	Pelvic diaphragm	Pelvic diaphragm
Components	Pubococcygeus, Iliococcygeus, Puborectalis	Single muscle
Origin	Pubic bone, obturator fascia, obturator internus fascia, pubic symphysis, superior fascia of the urogenital diaphragm (varies by component)	Ischial spine and ischium
Insertion	Coccyx, sacrum, tendinous center of perineum, anococcygeal raphe, rectal sling (varies by component)	Inferior sacrum and coccyx
Innervation	Not specified in the PDF	Anterior rami of S4–S5
Actions	Supports pelvic floor; Puborectalis forms the anorectal angle for fecal continence	Supports and stabilizes the posterior pelvic floor; flexes the coccyx

Exam Summary

Muscle	Remember This
Levator Ani	Three parts: Pubococcygeus, Iliococcygeus, Puborectalis. The Puborectalis forms the anorectal angle, which is essential for fecal continence. Weakness can cause pelvic organ prolapse.
Coccygeus	Origin: Ischial spine → Insertion: Sacrum & coccyx → Innervation: S4–S5 → Action: Supports and stabilizes the pelvic floor and flexes the coccyx during defecation and childbirth.

Perineal Muscles

i. Bulbospongiosus:

Category	Bulbospongiosus
Muscle Group	Superficial perineal muscle
Location	Located in the superficial perineal pouch of the urogenital triangle.
Origin	Perineal body.
Insertion	Male: Wraps around the bulb of the penis and inserts into the perineal membrane and the corpus spongiosum of the penis.Female: Surrounds the bulbs of the vestibule and inserts into the perineal membrane and the corpus cavernosum of the clitoris.
Innervation	Perineal branch of the pudendal nerve.
Actions	• Assists in ejaculation by rhythmically contracting to expel semen from the urethra (male). • Constricts the vaginal orifice and assists in clitoral erection by compressing the bulbs of the vestibule (female). • Provides pelvic floor support. • Contributes to urinary continence by compressing the urethra. • Contributes to fecal continence by supporting the external anal sphincter.

II. Ischiocavernosus

Category	Ischiocavernosus
Muscle Group	Superficial perineal muscle
Location	Located in the superficial perineal pouch of the urogenital triangle.
Origin	Ischial tuberosity and ischiopubic ramus.
Insertion	Crura of the penis or clitoris.
Innervation	Perineal branch of the pudendal nerve.
Actions	• Maintains erection.• Helps with ejaculation.• Assists in emptying the last bits of urine.• Stabilizes the erectile structures.

High-Yield Comparison

Feature	Bulbospongiosus	Ischiocavernosus
Muscle Type	Superficial perineal muscle	Superficial perineal muscle
Location	Superficial perineal pouch	Superficial perineal pouch
Origin	Perineal body	Ischial tuberosity and ischiopubic ramus
Insertion	Corpus spongiosum (male) / Corpus cavernosum of clitoris (female)	Crura of penis or clitoris
Innervation	Perineal branch of the pudendal nerve	Perineal branch of the pudendal nerve
Main Actions	Ejaculation, constricts vaginal orifice, assists clitoral erection, supports pelvic floor, aids urinary and fecal continence	Maintains erection, assists ejaculation, empties the last urine, stabilizes erectile structures

Identify the following pelvic vasculature
1. Anterior trunk of the internal iliac
  1. Obliterated umbilical artery
  2. Obturator artery
  3. Uterine artery
  4. Inferior vesical artery
  5. Vaginal artery (not in males)
  6. Middle rectal artery
  7. Internal pudendal artery
    1. Penile artery

Inferior gluteal artery

The anterior division of the internal iliac artery primarily gives rise to visceral branches that supply the pelvic organs, perineum, external genitalia, and portions of the gluteal region.

Artery	Location / Course	Structures Supplied (Function)	Important Features / Clinical Notes
Obliterated Umbilical Artery	Branch of the anterior division of the internal iliac artery.	Gives rise to the superior vesical artery, which supplies the urinary bladder.	Distal portion becomes the medial umbilical ligament after birth.
Obturator Artery	Branch of the anterior division; travels toward the obturator canal.	Supplies the obturator internus muscle and the medial thigh.	Passes through the obturator foramen with the obturator nerve and vein.
Uterine Artery(Female only)	Branch of the anterior division.	Supplies the uterus and vagina.	Crosses over the ureter, an important relationship to remember during surgery to prevent ureteral injury ("water under the bridge").
Inferior Vesical Artery(Male)	Branch of the anterior division.	Supplies the urinary bladderand prostate.	Present in males according to the PDF.
Vaginal Artery(Female only)	Branch of the anterior division.	Supplies the vagina and urinary bladder.	Not present in males.
Middle Rectal Artery	Branch of the anterior division.	Supplies the rectum.	The PDF notes it is often associated with internal hemorrhoids.
Internal Pudendal Artery	Branch of the anterior division that travels into the perineum.	Supplies the perineum, external genitalia, and anal canal.	Gives rise to the inferior rectal artery, perineal artery, and dorsal artery of the penis/clitoris.
Penile Artery	Branch of the internal pudendal artery.	Supplies the penis.	Listed in the PDF as a branch of the internal pudendal artery.
Inferior Gluteal Artery	Branch of the anterior division.	Included as a branch of the anterior division of the internal iliac artery.	Listed in the pelvic vasculature section of the PDF.

Branches of the Internal Pudendal Artery

Branch	Supplies
Inferior Rectal Artery	Anal canal
Perineal Artery	Perineum
Dorsal Artery of the Penis / Clitoris	Penis or clitoris
Penile Artery	Penis

Artery	Remember This
Obliterated Umbilical Artery	Becomes the medial umbilical ligament and gives rise to the superior vesical artery.
Obturator Artery	Supplies the obturator internus muscle and medial thigh.
Uterine Artery	Crosses over the ureter; supplies the uterus and vagina.
Inferior Vesical Artery	Supplies the bladder and prostate.
Vaginal Artery	Supplies the vagina and bladder (female only).
Middle Rectal Artery	Supplies the rectum; associated with internal hemorrhoids in the PDF.
Internal Pudendal Artery	Main blood supply to the perineum, external genitalia, and anal canal.
Penile Artery	Branch of the internal pudendal artery supplying the penis.
Inferior Gluteal Artery	Branch of the anterior division of the internal iliac artery.

Posterior Trunk (Posterior Division) of the Internal Iliac Artery

The posterior division of the internal iliac artery primarily gives rise to parietal branches, which supply the pelvic walls, gluteal region, sacrum, and supporting musculoskeletal structures rather than the pelvic organs.

Artery	Location / Course	Structures Supplied (Function)	Important Features
Iliolumbar Artery	Branch of the posterior division of the internal iliac artery.	Listed as a posterior division branch supplying the pelvic supporting structures.	One of the three major branches of the posterior trunk.
Lateral Sacral Artery	Branch of the posterior division of the internal iliac artery.	Listed as a posterior division branch supplying the pelvic supporting structures.	Travels along the sacrum.
Superior Gluteal Artery	Branch of the posterior division of the internal iliac artery.	Supplies the gluteal muscles.	Largest branch of the posterior division shown in the pelvic vasculature diagrams.

High-Yield Summary:

Posterior Division Branch	Remember This
Iliolumbar Artery	Posterior division branch that supplies pelvic supporting structures.
Lateral Sacral Artery	Posterior division branch that courses along the sacrum and supplies pelvic supporting structures.
Superior Gluteal Artery	Posterior division branch that supplies the gluteal region.

Easy Way to Remember

Posterior Branch	Think of...
Iliolumbar	Ilium + lumbar region
Lateral Sacral	Sacrum
Superior Gluteal	Gluteal muscles (buttock)

Memory Trick: "I Love Glutes"

I = Iliolumbar artery
L = Lateral sacral artery
G = Superior gluteal artery

This mnemonic matches the three branches listed in your pelvic anatomy

Lymphatic nodes
1. Superficial inguinal nodes
2. Deep inguinal nodes

The pelvic lymphatic system contains superficial (palpable) and deep (non-palpable) lymph nodes that drain different regions of the pelvis, lower limb, and external genitalia. Knowing what each node drains helps identify the possible source of infection or cancer spread.

Superficial Inguinal Nodes

Category	Study Guide
Location	Located in the superficial inguinal region (groin). They are superficial and palpable, located near the femoral pulse.
Palpable?	Yes – can normally be palpated during a physical examination.
Drainage	• Anterior abdominal wall• Inguinal region• External genitalia
Clinical Correlation	A "lump in the groin" may indicate disease involving structures drained by these nodes. The PDF specifically notes evaluating for STIs or anal cancer, not just leg pathology.

Deep Inguinal Nodes

Category	Study Guide
Location	Located in the deep inguinal region. They are part of the deep (non-palpable) pelvic lymphatic system.
Palpable?	No – deep and non-palpable.
Drainage	• Receive lymph from the superficial inguinal nodes.• Drain the deep structures of the leg.
Relationship	Act as the next drainage station after the superficial inguinal nodes before lymph continues centrally.

Other Deep Pelvic Lymph Nodes

Lymph Node Group	Drains
External iliac nodes	Pelvic viscera
Internal iliac nodes	Pelvic viscera
Pararectal nodes	Colorectal area
Sacral nodes	Colorectal area
Lumbar lymph nodes	Primary sites for testicular cancer and ovarian cancer metastasis (not the inguinal nodes).

Feature	Superficial Inguinal Nodes	Deep Inguinal Nodes
Location	Superficial groin	Deep groin
Palpable	✅ Yes	❌ No
Drain	Anterior abdominal wall, inguinal region, external genitalia	Superficial inguinal nodes and deep structures of the leg
Clinical Pearl	Enlarged with infections or disease affecting structures they drain (e.g., STI or anal cancer per the PDF)	Receive drainage from superficial nodes and deep leg structures

Identify the location and innervations of the pelvis
1. Sacral plexus
  1. Superior and inferior gluteal nerve
  2. Pudendal nerve
  3. Sciatic nerve
2. Autonomic innervation
  1. Sacral sympathetic trunk
  2. Pelvic Splanchnic nerves
  3. Hypogastric plexus

Sacral Plexus:

The sacral plexus is formed by the lumbosacral trunk (L4–L5) and the anterior rami of S1–S4. It lies on the anterior surface of the piriformis muscle on the posterior pelvic wall and supplies the pelvis, gluteal region, perineum, and lower limb.

Category	Study Guide
Location	Lies on the anterior surface of the piriformis muscle in the posterior pelvis.
Formation	Lumbosacral trunk (L4–L5) + S1–S4 ventral rami.
Function	Provides motor and sensory innervation to the pelvis, gluteal region, perineum, and lower limb.

Superior and Inferior Gluteal Nerves

Nerve	Location / Course	Innervates
Superior Gluteal Nerve	Branch of the sacral plexus that exits the pelvis to the gluteal region.	Gluteus medius, gluteus minimus, and tensor fasciae latae.
Inferior Gluteal Nerve	Branch of the sacral plexus that exits the pelvis to the gluteal region.	Gluteus maximus.

Superior gluteal nerve = gluteus medius & minimus + TFL
Inferior gluteal nerve = gluteus maximus

Pudendal Nerve:

Category	Study Guide
Location / Course	Branch of the sacral plexus that travels to the perineum.
Innervates	• Perineum • External genitalia • External anal sphincter • Perineal muscles (including bulbospongiosus and ischiocavernosus).
Clinical Importance	The perineal branch supplies the superficial perineal muscles.

Category

Study Guide

Location / Course

Branch of the sacral plexus that travels to the perineum.

Innervates

• Perineum

• External genitalia

• External anal sphincter

• Perineal muscles (including bulbospongiosus and ischiocavernosus).

Clinical Importance

The perineal branch supplies the superficial perineal muscles.

Sciatic Nerve:

Category	Study Guide
Location / Course	Largest branch of the sacral plexus that exits the pelvis to enter the lower limb.
Innervates	Lower limb (listed as a major branch of the sacral plexus in the PDF).

Autonomic Innervation of the Pelvis

The pelvic autonomic nervous system consists of sympathetic and parasympathetic fibers that regulate involuntary functions of the pelvic organs. The PDF identifies three major autonomic structures:

Sacral sympathetic trunk
Pelvic splanchnic nerves
Hypogastric plexus

Sacral Sympathetic Trunk:

Category	Study Guide
Location	Located within the pelvis as part of the autonomic nervous system.
Type	Sympathetic.
Function	Contributes sympathetic fibers to the pelvic organs through the pelvic autonomic plexuses.

Pelvic Splanchnic Nerves:

Category	Study Guide
Location	Pelvic autonomic nerves arising within the pelvis.
Type	Parasympathetic.
Function	Provide parasympathetic innervation to the pelvic organs.

Hypogastric Plexus:

Category	Study Guide
Location	Pelvic autonomic nerve plexus within the pelvis.
Function	Network that distributes autonomic fibers (sympathetic and parasympathetic) to the pelvic organs.

High-Yield Summary Table

Structure	Location	Innervates / Function
Sacral Plexus	Anterior surface of piriformis	Pelvis, gluteal region, perineum, lower limb
Superior Gluteal Nerve	Branch of sacral plexus	Gluteus medius, gluteus minimus, tensor fasciae latae
Inferior Gluteal Nerve	Branch of sacral plexus	Gluteus maximus
Pudendal Nerve	Branch of sacral plexus to perineum	Perineum, external genitalia, external anal sphincter, perineal muscles
Sciatic Nerve	Branch of sacral plexus	Lower limb
Sacral Sympathetic Trunk	Pelvis	Sympathetic fibers to pelvic organs
Pelvic Splanchnic Nerves	Pelvis	Parasympathetic fibers to pelvic organs
Hypogastric Plexus	Pelvis	Distributes autonomic fibers to pelvic organs

Superior gluteal → Medius, Minimus, TFL
Inferior gluteal → Maximus
Pudendal → Perineum
Sciatic → Lower limb
Sacral sympathetic trunk = Sympathetic
Pelvic splanchnic nerves = Parasympathetic
Hypogastric plexus = Autonomic distribution center