The Appendicular Skeleton

Resident Orientation Course 2012By Dr. Totakhil

THE SKELETAL SYSTEMThe Appendicular Skeleton

• 2 pairs of limbs and 2 girdles– Pectoral (shoulder) girdle attaches upper limbs– Pelvic (hip) girdle secures lower limbs

• 3-Segmented limbs

Upper = arm Lower = Leg

Arm Thigh

Forearm Leg

Hand Foot

Pectoral Girdle(Shoulder Girdle)

• Clavicle – anterior: collar bone

– Sternal end attaches to the manubrium medially

– Acromial end articulates with the scapula laterally

• Scapula – posterior: shoulder blade

Scapula

• Glenoid cavity articulates with the humerus

• Acromium articulates with clavicle

• Coracoid process projects anteriorly

Scapulae: triangular, paired, does not connect in back (adds thoracic flexibility)

Upper Extremity

• Arm or Brachium = upper arm– Between shoulder and elbow (humerus)

• Forearm or Antebrachium– Radius & ulna

• Hand includes:– Wrist (carpus)– Palm (metacarpus)– Fingers (phalanges)

Arm

• Humerus is the only bone– Head of humerus fits into glenoid cavity of

scapula– Distal & medially, trochlea articulates with the

ulna– Distal & laterally capitulum articulates with the

radius– Medial & lateral epicondyles

Muscles of the Shoulder Girdle

Anterior Compartment Flexors

Posterior Compartment Flexors

Forearm

• Consists of 2 bones the radius and ulna

• These bones articulate with each other proximally

and distally

• An interosseous membrane is between these 2

bones

Radius

• Long bone situated on the lateral side of the forearm• Together with the ulna, it provides attachment for the

forearm muscles• It consists of an articular head above, which articulates

with the humerus and ulna to form the elbow joint• Consists of an articular surface below, which articulates

with the carpal bones to form the wrist• Its lower end rotates around the ulna, whose position is

fixed, to supinate and pronate the forearm and hand

Ulna

• Long bone situated on the medial side of the forearm.

• Together with the radius, they provide attachment for the forearm muscles

• Consists of a large trochlear surface above, which articulates with the humerus to form the elbow joint

• Consists of a small head below, which articulates with the radius to form the radioulnar joint

Radius is thinner proximally, like a spool of thread, and wide distally; ulna is slightly longer and looks like a monkey wrench (supposedly!)

Anatomic Position

• In the anatomical position:

– Radius is lateral (thumb side); with pronation the palm

faces posteriorly and the bones cross

• Prone: body lying face down

– You can remember prone if you think about how you

would fall forward onto your face if you passed out

• Supine: body lying face up

Proximal and Distal Joints of the Forearm

Muscles of the Forearm

Muscles of the Forearm

Hand

• Wrist: consists of 8 carpal bones– Articulate above with the radius at the radiocarpal joint– Articulate with each other at the intercarpal joints– Articulate below with the metatarsals at the

carpometacarpal joints

Hand

• Hand: consists of 5 metacarpals bones– The 1st metacarpal lies laterally, providing a base

for the thumb– The 5th metacarpal lies medially, forming a base

for the little finger– Proximally they articulate with the carpal bones at

the carpometacarpal joints– Distally they articulate with the proximal

phalanges at the metacarpophalangeal joints

Hand

• Fingers (or digits) consist of miniature long bones

called phalanges:

– Thumb has 2 bones: proximal and distal

– The other fingers have 3 bones: proximal, middle,

distal

Pelvic Girdle

• Strongly attached to axial skeleton (sacrum)• More stable than pectoral (shoulder) girdle• Less freedom of movement• Made up of the paired hip bones– “Bony pelvis” is basin-like structure: hip bones

plus the axial sacrum and coccyx

Male Pelvis Female Pelvis

Heavier Lighter and thinner

Heart shaped pelvic inlet Round or oval shaped pelvic inlet

Prominent muscle and ligament attachments

Less prominent muscle and ligament attachments

Sub-pubic angle is less than 90 degrees

Sub-pubic angle is greater than 90 degrees

Longer narrower pelvic cavity Shorter wider pelvic cavity

Differences Between Male and Female Pelvis

Hip bone (Os Coxae): 3 separate bones in childhood which fuse

Ilium

• Iliac crest

• Anterior superior iliac

spine

• Greater sciatic notch

• Forms part of

“acetabulum”

(hip socket) which receives

ball-shaped head of femur

Ischium

• Body

• Ramus

• Ischial spine

• Ischial tuberosity

• Part of hip socket

Pubis

• Joins medially in pubic symphysis• Forms “obturator foramen” (large hole) with ischium• Part of hip socket

Lower Limb

• Thigh: femur

• Leg (Lower Leg)

– Tibia

– Fibula

• Foot

Thigh

• Femur: Longest bone in the body

– It consists of a head above, which articulates with

the hip bone to form the hip joint

– Has two large condyles below, which articulate

with the tibia and patella to form the knee joint

Patella

• The patella, the largest sesamoid bone in the body

• It is embedded in the tendon of quadriceps femoris, and

is located anterior to the knee-joint

• Its outline is somewhat in the shape of an inverted

triangle

• It is separated from the femur by the suprapatellar bursa

Leg

• Tibia– The larger and medial of the two bones of the leg– It consists of two expanded extremities joined by

a shaft• Fibula– Lateral and more slender of the two bones of the

leg

Foot

• Tarsus: 7 tarsal bones– Talus: articulates with tibia and fibula anteriorly and

calcaneus posteriorly– Calcaneus: heel bone– Other bones: Cuboid, navicular, and 3 cunieforms (medial,

intermediate and lateral)

• 5 metatarsals• 14 phalanges– Great toe is called the hallux

Muscles of the Foot

Any Questions??

References

• www. rci.rutgers.edu