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The Appendicular Skeleton
The Appendicular Skeleton

126 bones
o
Limbs (appendages)
o
Pectoral girdle (attaches arm to the axial skeleton)
o
Pelvic girdle (attaches leg to the axial skeleton)
The Pectoral (Shoulder) Girdle


Composed of two bones
o
Clavicle – collarbone
o
Scapula – shoulder blade
These bones are very light and allow the upper limb to have exceptionally free movement
because:
1. Each pectoral girdle attaches to axial skeleton at only 1 point =
sternoclavicular joint
2. The loose attachment of the scapula allows it to slide back & forth against the
thorax
3. The glenoid cavity is shallow & the shoulder joint is poorly reinforced by
ligaments

Consists of 2 bones:
1. Clavicle (collar bone) = slender, double curved bone
o
Attaches to manubrium of the sternum medially & to the scapula laterally
o
Acts as a brace to hold the arm away from the thorax & helps prevent
shoulder dislocation
2. Scapula (shoulder blade) = triangular & flare when we move our arms posteriorly
(“wings”)
o
Not directly attached to axial skeleton; held in place by trunk muscles
o
Flattened body w/ 2 processes:

Acromion process = the enlarged end of the spine of the scapula
 Connects w/ the clavicle @ the acromioclavicular joint

Coracoid process = beaklike
 Points over the shoulder & anchors some of the arm muscles
o
Suprascapular notch serves as a nerve passageway
o
Scapula has 3 borders & 3 angles:

Superior

Medial (vertebral)

Lateral (axillary)

Superior

Inferior

Lateral
borders
Angles
Bones of the Upper Limb (30)
 The arm is formed by a single bone

Humerus
o
Rounded proximal end fits into glenoid cavity of scapula
o
Opposite of the head – 2 bony processes = greater & lesser tubercles, sites of
muscle attachment
o
Midpoint of shaft – deltoid tuberosity where the deltoid m. attaches
o
Radial groove runs obliquely down the posterior shaft
o
Distal end – medial trochlea (looks like a spool) & lateral ball-like capitulum – both
articulate w/ bones of forearm
o
Above the trochlea anteriorly is a depression – coronoid fossa
o
On posterior surface is the olecranon fossa
o Both are flanked by medial & lateral epicondyles

Forearm – consists of the radius & ulna
o
Radius is lateral when the arm is in the anatomical position (on the thumb side) &
the ulna is medial
o
When the hand is rotated, the distal end of the radius crosses over & ends up
medial to the ulna.
o
Radius & ulna articulate @ small radioulnar joints
o
They are connected along their entire length by a flexible interosseous
membrane
o
Both have a styloid process @ their distal end
o
Disc-shaped radial head forms a joint w/ the capitulum of the humerus.
o
Below the head is the radial tuberosity where tendon of biceps m. attaches.
o
On the ulna’s proximal end are the anterior coronoid process & the posterior
olecranon process, which are separated by the trochlear notch.


These 2 processes grip the trochlea of the humerus in a pliers-like joint.
Hand consists of carpals, metacarpals & phalanges
o
8 carpals arranged in 2 irregular rows of 4 bones each form the part of the hand
called the carpus (wrist)

o
o
Bound together by ligaments that restrict movements between them.
Metacarpals form the palm

Numbered 1 to 5 from the thumb to the pinky

Clenched fist – heads of the metacarpals = knuckles
Phalanges (14) are the finger bones (3 in each finger & 2 in the thumb)
Carpals starting Left to Right (pinky to thumb both rows):
Joe took a Hamate and hit poor Pete in the
Capitate, breaking it into a Trapezoid and
Trapezium. He did it b/c he was Pisiform(d)
Triquetral times. The Judge said he was
Lunate and sent him to the Scaphoid.
The Bony Pelvis vs. the Pelvic Girdle

Bony Pelvis
o

Composed of:

Sacrum

Coccyx

Coxal bones (coxae) or ossa coxae (Hip bones)
Pelvic Girdle
o
Coxae are composed of three pair of fused bones

Ilium

Ischium

Pubic bone
The Pelvic Girdle: Right Coxal Bone

Coxae are large, heavy & attached securely to the axial skeleton.

Sockets that receive the femur are deep & heavily reinforced w/ ligaments.

Function = bearing weight; total wt. of upper body rests on pelvis.

Reproductive organs, bladder & part of large intestine lie within & are protected by
pelvis.

Each coxa is formed by the fusion of 3 bones:
1. Ilium (Large flaring bone - forms most of the coxa)
 Connects posteriorly w/ sacrum @ the sacroiliac joint.
 Alae - winglike portions of the ilia.
 Iliac crest – upper edge of alae that ends anteriorly in the anterior
superior iliac spine & posteriorly in the posterior superior iliac spine w/
small inferior spines located below these.
2. Ischium (“sit down bone”)
 Most inferior part of coxa.
 Ischial tuberosity, a roughened area, receives body wt. when sitting.
 Ischial spine, superior to the tuberosity, narrows the outlet through
which the baby passes during childbirth.
 Greater sciatic notch allows blood vessels & the large sciatic nerve to
pass from the pelvis posteriorly into the thigh.
3. Pubis or pubic bone
 Most anterior part of the coxa.
 Fusion of the rami of the pubis anteriorly & the ischium posteriorly
forms a bar of bone enclosing the obturator foramen, an opening
through which blood vessels & nerves pass into the anterior part of
the thigh.
 Pubic bones fuse anteriorly to form a cartilaginous joint called the
pubic symphysis.

The ilium, ischium, & pubis fuse @ the deep socket called the acetabulum (“vinegar
cup”); it receives the head of the femur.
The Bony Pelvis
Male pelvis

Female pelvis
Bony pelvis is divided into 2 regions:
o
False pelvis, superior to the true pelvis, is the area medial to the flaring portions
of the ilia.
o
True pelvis lies inferior to the flaring parts of the ilia & the pelvic brim.
o
Dimensions of the true pelvis are important for childbirth – must be large enough
for the head to pass.

Outlet is the inferior opening of the pelvis.

Inlet is the superior opening.
Differing characteristics between the male & female pelvis

Female inlet is larger & more circular.

Female pelvis as a whole is shallower & the bones are lighter & thinner.

Female ilia flare more laterally.

Female sacrum is shorter & less curved.

Female Ischial spines are shorter & farther apart; thus the outlet is larger.

Female pubic arch is more rounded because the angle of the pubic arch is greater.
Bones of the Lower Limbs

Carry our total body weight when standing = thicker & stronger.

The thigh has one bone – femur (thigh bone)

Femur (thigh bone)
o
Heaviest, strongest bone in the body.
o
Proximal end has ball-like head, neck and greater & lesser trochanters.
Trochanters are separated anteriorly by intertrochanteric line and posteriorly by
intertrochanteric crest.
o
Trochanters, inter.-crest & gluteal tuberosity are sites for muscle attachment.
o
Slants medially as it runs downward to bring knees in line w/ body’s center of
gravity. (more noticeable in females b/c of wider pelvis)
o
Distally are the lateral & medial condyles – articulate w/ tibia. (condyles
separated by condylar fossa)
o
Anteriorly on distal end is the patellar surface – forms a joint w/ patella (kneecap)

Lower leg has 2 bones – Tibia & Fibula
o

Connected by interosseous membrane.
Tibia (shinbone)
o
Larger & more medial
o
At proximal end – medial & lateral
condyles (separated by intercondylar
eminence) articlulate w/ distal end of
femur to form knee joint.
o
Patellar ligament attaches to tibial
tuberosity (anter.)
o
Distally, a process called medial malleolus
forms inner bulge of ankle.
o
Anterior surface has sharp ridge – anterior
border (unprotected by muscle – so you
can feel this)

Fibula
o
Thin & sticklike
o
Distally - lateral malleolus forms outer
part of ankle.

Foot – composed of tarsals, metatarsals &
phalanges
o
Two important functions: supports
body weight & serves as a lever
allowing us to propel body forward
when walking,etc.
o
7 Tarsals

Weight carried by the 2
largest tarsals:
 calcaneus
(heelbone) &
 talus (lies b/n tibia &
calcaneus)
o
5 metatarsals form the sole
o
14 phalanges form the toes (each
toe has 3, except the big toe)
o
Bones are arranged to form 3 strong arches:

2 longitudinal (medial & lateral), 1 transverse
 Ligaments bind foot bones together
 Tendons of the foot muscles help to hold bones in arched position
but allow for “springiness” – weak arches are referred to as “fallen
arches” or “flat feet”