Appendicular Skeleton: Pelvis (OS Coxa) and Associated Muscles
Module: Skeletal Topic: Pelvis View: Superior
Ala of Sacrum:
Location:
sacrum (base)
Description:
paired, wing-like, laterally projecting masses
modification of the S1 vertebral transverse process
Comments:
the base of the sacrum is the superior surface of the S1 vertebra
Anterior Inferior Iliac Spine:
Location:
ilium (anterior)
at the upper margin of the acetabulum
Description:
roughened projection
Comments:
provides attachment for the rectus femoris muscle
Anterior Superior Iliac Spine:
Location:
ilium (anterior end of iliac crest)
Description:
a small, rounded, bony projection
Comments:
provides attachment for the lateral end of the inguinal ligament and for the sartorius and the tensor fasciae latae muscle
Coccyx:
Location:
posterior pelvic wall
lower back, inferior to the S5 vertebra
Description:
a small, triangular bone
consists of 3 to 5, variably fused, poorly developed vertebrae
Comments:
know as the “tailbone”
rudiment of the tail in the other vertebrates
Iliac Crest:
Location:
ilium
Description:
a prominent ridge on the superior margin
Comments:
provides attachment for muscles of the back, the thigh, and the abdominal wall
landmark for the intramuscular injections
Iliac Fossa:
Location:
ilium (pelvic surface)
Description:
a broad, shallow concavity
forms the posterolateral wall of the greater pelvis
Comments:
the right iliac fossa contains cecum, vermiform appendix, and terminal ileum
the left iliac fossa contains the terminal descending colon
Ilium:
Location:
pelvis
Description:
the largest of 3 coxal (hip) bones
has a large, wing-like superior extension (ala); the law form the bony walls of the greater (false) pelvis
contributes to the acetabulum (hip joint socket) and wall of the lesser (true) pelvis
articulates with the sacrum at the sacroiliac joint
Comments:
fused with the ischium and the pubis in an adult to form the coxal (hip) bone
bony pelvis is formed by paired hip bones and the sacrum
Intervertebral Disc:
Location:
between the vertebral bodies (C2 to S1)
Description:
outer part: annulus fibrosis consisting of a fibrocartilage ring
inner part: nucleus pulposus composed of mucoid material
Comments:
no disk between the atlas (C1 vertebra) and axis (C2 vertebra)
Ischial Spine:
Location:
ischium
Description:
a pointed projection
Comments:
provides attachment for the pelvic diaphragm (coccygeus muscle) and the sacrospinous ligament
landmark for administering anesthetic during childbirth (“pudendal block”)
Ischium:
Location:
pelvis
Description:
1 of 3 coxal (hip) bones
characteristic features include a tuberosity and the spine
contributes to the acetabulum (hip joint socket), the obturator foramen, and the wall of the lesser (true) pelvis
Comments:
fused with ilium and pubis in adults to form coxal (hip) bone
obturator foramen formed by rami of pubis and ischium
Lumbar Vertebra:
Location:
lower back
between T12 and S1 vertebrae
Description:
5 individual vertebrae
characteristic features include a large size, kidney bean-shaped body, and a thick, blunt spinous process
Comments:
bodies are arranged to form the prominent anterior convexity (limbar curvature; also known as lumbar lordosis, which can be accentuated pathologically)
intervertebral discs between the lumbar vertebrae most commonly herniate (“slipped disk”)
Pelvic Inlet:
Location:
pelvis
Description:
a ridge of bone marking the junction of the false (greater) pelvis and true (lesser) pelvis
sacrum, ilium, and pubis contribute to the inlet
sacral promontory and alae; arcuate line of the ilium; pectineal line of the superior pubic ramus; and the pubic crest on the body of the pubis form the pelvic intel
Comments:
known as the “pelvic brim”
wide and oval-shaped in females
heart-shaped in males
Pubic Crest:
Location:
pubis (body)
Description:
rounded, upper border of the body
ends laterally as a pubic tubercle
Pubic Symphysis:
Location:
pelvis (anterior midline)
Description:
the joint is formed by 2 pubic bones and an intervening fibrocartilage disc
Comments:
in females, the fibrocartilage softens in late pregnancy to allow slight separation of the pubic bones
Pubic Tubercle:
Location:
pubis (body)
Description:
a small projection lateral to the pubis symphysis
Comments:
provides attachment for the medial end of the inguinal ligament
Pubis:
Location:
pelvis
Description:
1 of 3 coxal (hip) bones
characteristic features include the body and the rami (superior and inferior)
midline junction of the pubic bones forms the pubic symphysis
contributes to the acetabulum (hip joint socket), obturator foramen, and the wall of the lesser (true) pelvis
Comments:
fused with ilium and ischium in an adult to form coxal (hip) bone
Sacro-iliac Joint:
Location:
pelvis
Description:
synovial joint between the sacrum and ilium
limited movement due to rough, irregular articular surfaces
Comments:
a major point of force (weight) transforms from the trunk to the lower limb
Sacrum:
Location:
lower back
between L5 and Co1 vertebrae
posterior wall of the pelvis
Description:
5 fused vertebrae
a triangular bone wedged between hip bones
Comments:
sacra; promontory 9the prominent, projecting edge of the base of the sacrum formed by the superior border of the S1 vertebral body) is a landmark for establishing female pelvic dimensions
Module: Muscular Topic: Abdomen View: Anterior
Rectus Abdominis m :
Action:
flexion of the trunk (sit-ups)
compression of the anterior abdominal wall
Origin:
pubis (crest and symphysis)
Insertion:
sternum (xiphoid process)
costal cartilages 5-7
Innervation:
ventral rami of the T7-12 spinal nerves
Comment:
3 or 4bellies, separated by tendinous intersections
encased in fibrous (rectus) sheath
important in "straining" (e.g., lifting, defecation, urination, child-birth)
functions in respiration ("abdominal breathing"
Module: Muscular Topic: Hip & Thigh View: Posterior
Gluteus Maximus m. :
Action:
extension of the thigh
lateral rotation of the thigh
abduction of the thigh
Origin:
ilium (ala)
sacrum
coccyx
Insertion:
iliotibial tract
femur (gluteal tuberosity)
Innervation:
inferior gluteal nerve
Comments:
important for powerful extension of the femur (running, climbing stairs, rising a from seated position)
NOT important in walking
Gluteus Medius m. :
Action:
abduction of the thigh (non-weight-bearing)
lowers pelvis on the weight-bearing side
Origin:
ilium (ala)
Insertion:
femur (greater trochanter)
Innervation:
superior gluteal nerve
Comments:
lowering (“tilting” downward) the pelvis on the weight-bearing side allows non-weight-bearing limbs to swing forward during walking
acts with the gluteus minimus
Module: Muscular Topic: Back View: Posterior
Erector Spine m. :
Action:
unilateral: lateral flexion and rotation of vertebral column and head
bilateral: extension of vertebral column and head
Origin:
iliocostalis: common origin and ribs
longissimus: common origin
spinalis: spinous processes and nuchal ligament
Insertion:
iliocostalis: ribs (1-12) and transverse processes (cervical)
longissimus: transverse processes (cervical and thoracic), ribs, and mastoid process
spinalis: spinous processes (cervical and thoracic) and occipital bone
Innervation:
dorsal rami of the spinal nerves
Comments:
“antigravity" muscles
composed of 3 muscular columns (lateral to medial): iliocostalis, longissimus, and spinalis
common origin of the erector spinae: dorsal sacrum, iliac crest, and spinous processes
Latissimus Dorsi m. :
Action:
adduction of the arm
extension of the arm
medial rotation of the arm
Origin:
sacral and lumbar spines via thoracolumbar fascia
ilium (iliac crest) via thoracolumbar fascia
ribs (lower four)
spinous processes of T6-12 vertebrae
scapula (inferior angle)
Insertion:
humerus (floor of intertubercular sulcus)
Innervation:
thoracodorsal nerve