Chapter 8: The Appendicular Skeleton

The Appendicular Skeleton Allows us to move and manipulate objects Includes all bones besides axial skeleton: the limbs the supportive girdles

The Pectoral Girdle Also called the shoulder girdle Connects the arms to the body Positions the shoulders Provides a base for arm movement Consists of: 2 clavicles 2 scapulae Connects with the axial skeleton only at the manubrium Figure 8–2a

The Clavicles Also called collarbones Long, S-shaped bones Originate at the manubrium (sternal end) Articulate with the scapulae (acromial end) Figure 8–2b, c

The Scapulae Also called shoulder blades Broad, flat triangles Articulate with arm and collarbone Anterior surface-subscapular fossa Structures Body Sides superior border medial border (vertebral border) lateral border (axillary border) Corners superior angle inferior angle lateral angle

Head Holds glenoid cavity Coracoid process-anterior, smaller Which articulates with humerus to form shoulder joint Coracoid process-anterior, smaller Acromion-posterior, larger

Scapular spine: ridge across posterior surface of body Separates 2 regions: supraspinous fossa infraspinous fossa

The Upper Limbs arms, forearms, wrists, & hands Humerus-arm The long, upper armbone Articulates with the pelvic girdle Structures Proximal Epiphysis separated by intertubercular groove: greater tubercle: lateral forms tip of shoulder lesser tubercle: anterior, medial

Head: Neck: Shaft rounded, articulating surface contained within joint capsule Neck: Anatomical neck- margin of joint capsule Surgical neck: the narrow metaphysis Shaft Deltoid tuberosity: a bulge in the shaft attaches deltoid muscle Radial groove: for radial nerve posterior to deltoid tuberosity

Distal Epiphysis Medial and lateral epicondyles: for muscle attachment Condyle of the humerus: Trochlea: coronoid fossa & olecranon fossa articulates with ulna Capitulum: radial fossa articulates with radius

With radius Ulnar head: articulates with head of radius forms proximal radioulnar joint Ulnar head: prominent styloid process attaches forearm to wrist

The Forearm-antebrachium Consists of 2 long bones: ulna & radius Ulna Articulations With humerus Forearm extended: olecranon (elbow point) enters olecranon fossa Forearm flexed: coronoid process enters coronoid fossa

Radius Articulations Ulnar notch: Styloid process: distal end articulates w/ wrist & radius Styloid process: stabilizes wrist joint

Wrist 8 carpal bones: allow wrist to bend and twist 4 proximal carpal bones Scaphoid bone: near styloid process Lunate bone: medial to scaphoid Triquetrum: medial to lunate bone Pisiform bone: anterior to triquetrum 4 distal carpal bones Trapezium: lateral Trapezoid bone: medial to trapezium Capitate bone: largest Hamate bone: medial, distal

Hands 5 Metacarpal Bones Phalanges long bones of the hand Numbered I–V from lateral (thumb) to medial Articulate with proximal phalanges Phalanges Pollex (thumb): 2 phalanges (proximal, distal) Fingers: 3 phalanges (proximal, middle, distal)

The Pelvic Girdle Hipbones - Os Coxae Made up of 3 fused bones: ilium ischium pubis Acetabulum - hip socket meeting point of ilium, ischium, & pubis on the lateral surface of the os coxae articulates with head of femur

Marks Obturator foramen: Pubic symphysis: formed by ischial and pubic rami attaches hip muscles Pubic symphysis: gap between pubic tubercles padded with fibrocartilage

The Pelvis Consists of 2 ossa coxae, sacrum, & coccyx Stabilized by ligaments of pelvic girdle, sacrum, and lumbar vertebrae

Divisions of the Pelvis True Pelvis Pelvic brim: upper edge of true pelvis encloses pelvic inlet Perineum region: inferior edges of true pelvis forms pelvic outlet perineal muscles support organs of pelvic cavity False pelvis blades of ilium above arcuate line

Childbearing Modifications Enlarged pelvic outlet Broad pubic angle (> 100°) Less curvature of sacrum and coccyx Wide, circular pelvic inlet Broad, low pelvis Ilia project laterally, not upwards Due to above, female pelvis is smoother & lighter

Lower Limbs Femur Structures Proximal Epiphysis Femoral head: Neck articulates with pelvis at acetabulum Neck narrow area between head & trochanters Greater & lesser trochanters tendon attachments

Patella - kneecap Shaft Distal Epiphysis A sesamoid bone Linea aspera: most prominent ridge of shaft attaches hip muscles Distal Epiphysis Medial & lateral epicondyles: above the knee joint Medial & lateral condyles: form part of knee joint Patella - kneecap A sesamoid bone Base attaches quadriceps femoris Apex attaches patellar ligament

Tibia Structures Proximal Epiphysis Shaft Distal Epiphysis Medial and lateral tibial condyles articulate with medial & lateral condyles of femur Tibial tuberosity: attaches patellar ligament Shaft Anterior margin: sharp ridge of shinbone Distal Epiphysis Medial malleolus: medial projection at ankle Figure 8–13

Fibula Fibula/tibia articulations: Interosseous membrane: head inferior tibiofibular joint Interosseous membrane: binds fibula to tibia Lateral malleolus: lateral projection of ankle

Ankle - tarsus consists of 7 tarsal bones Talus carries weight from tibia across trochlea Calcaneus (heel bone): transfers weight from talus to ground & attaches Achilles tendon Cuboid bone: articulates with calcaneus Navicular bone: articulates with talus and 3 cuneiform bones Medial cuneiform Intermediate cuneiform Lateral cuneiform Figure 8–14a

Feet 5 metatarsal bones phalanges long bones of foot numbered I–V, medial to lateral Articulate with toes phalanges bones of the toes hallux: big toe, 2 phalanges (distal, proximal) Other 4 toes: 3 phalanges (distal, medial, proximal) Figure 8–14a

Arches Arches transfer weight from 1 part of the foot to another Longitudinal Arch Calcanear portion: lateral Talar portion: medial Transverse Arch Formed by a difference in curvature between medial and lateral borders of the foot Figure 8–14b