Appendicular skeleton

Appendicular Skeleton

Comprised of 126 bones of limbs and their girdles

Pectoral Girdle (Shoulder Girdle)

• Comprised of clavicle and scapula - Attach upper limb to axial skeleton - Provide attachment sites for muscles that move upper limbs - Shoulder girdles + associated muscles = Shoulders

Clavicles (Collarbones)

• Only bone of shoulder girdle/upper limb that directly attaches to axial skeleton

Clavicles functions

• Anchors muscles - Braces scapula out laterally - Transmits compressive forces from upper limb to axial skeleton

Clavicle shape

• S-shaped bone - Cone-shaped sternal end articulates with the sternum - Flattened acromial end articulates with the scapula

Scapulae (Shoulder Blades)

• On posterior surface of rib cage, between ribs 2 and 7 - Flat and triangular, with three borders and three angles - Several large fossae named according to location

Glenoid fossa

shallow - allows for movement but also instability

The upper extremity

30 bones form skeletal framework of each upper limb(60 for both arms)

Arm (upper arm - between shoulder and elbow)

Humerus

Forearm

Radius and ulna

Hand

• 8 carpal bones in the wrist - 5 metacarpal bones in the palm - 14 phalanges in the fingers

Arm

• Head of humerus articulates superiorly with the glenoid cavity scapula - Two condyles (trochlea and capitulum )articulate inferiorly with radius and ulna

Interosseous membrane

connects radius and ulna along their entire length

Ulna

• Articulates with distal humerus and proximal radius - Olecranon locks into the olecranon fossa on humerus to keep elbow from hyperextending - Distally, the head of the ulna does not directly articulate with the bones in the wrist

Radius

• Head articulates with the capitulum of humerus and radial notch of ulna - Distally, the radius articulates with the carpal bones of the wrist. - Hand moves with the radius

8 bones

Carpus (wrist)

5 bones

Metacarpus (Palm)

14 bones

Phalanges (Fingers)

Proximal row—lateral to medial

Scaphoid, lunate, triquetrum, and pisiform

Distal row—lateral to medial

Trapezium, trapezoid, capitate, and hamate

Metacarpus (Palm)

• Numbered: I to V from thumb to little finger - Base articulates with carpals - Head articulates with proximal phalanges

Phalanges (Fingers)

Fingers numbered I to V starting at thumb (pollex)

Digit I (Pollex)

has 2 bones - proximal and distal phalanx;no middle phalanx

Digits II to V

have 3 bones—distal, middle, and proximal phalanx

Pelvic (Hip) Girdle

Two hip bones (coxal bones) and sacrum

Functions of Pelvic girdle

• Attach lower limbs to axial skeleton with strong ligaments - Transmit weight of upper body to lower limbs - Support pelvic organs

Ilium

• Superior region of coxal bone - Auricular surface articulates with sacrum (sacroiliac joint)

Ischium

Posterior-inferior part of hip bone

Pubis

• Anterior portion of hip bone - Pubis joins at pubic symphysis joint

Femur

• Largest and strongest bone in the body - Length ~ ¼ of person's height - Articulates proximally with acetabulum of hip and distally with tibia and patella

Patella

Sesamoid bone in quadriceps tendon

Tibia

• Medial leg bone - Receives weight of body from femur; transmits to foot

Fibula

• No articulation with femur - Limited weight bearing - Articulates proximally and distally with tibia

7 bones of Tarus

Calcaneous: Achilles tendon insertion, Talus: articulates with tibia, Navicular, Cuboid, Lateral, intermediate, and medial cuneiforms

Metatarsals

5 metatarsal bones (I to V from hallux to little toe)

1st metatarsal

• short and thick - Forms "ball" of foot

Digit I (Hallux)

has 2 bones - no middle phalanx

Digits II to V (toes)

have 3 bones—distal, middle, and proximal phalanx

Arches Of The Foot

Maintained by interlocking foot bones, ligaments, and tendons

Three arches

• Lateral longitudinal - Medial longitudinal - Transverse

Babies and Children

• Skull has fontanelles - Baby's head large relative to body - Convex curvatures of spine present at birth

Developmental Aspects: Old Age

• Intervertebral discs thin, less hydrated, and less elastic: Risk of disc herniation increases - Costal cartilages ossify: Rigid thorax causes shallow breathing and less efficient gas exchange