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Chapter 8: The Appendicular Skeleton

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The Appendicular Skeleton Figure 81

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

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The Pectoral Girdle Figure 82a

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The Pectoral Girdle Also called the shoulder girdle Connects the arms to the body Positions the shoulders Provides a base for arm movement

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The Pectoral Girdle Consists of: 2 clavicles 2 scapulae Connects with the axial skeleton only at the manubrium

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The Clavicles Figure 82b, c

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The Clavicles Also called collarbones Long, S-shaped bones Originate at the manubrium (sternal end) Articulate with the scapulae (acromial end)

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The Scapulae Also called shoulder blades Broad, flat triangles Articulate with arm and collarbone

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The Scapula Anterior surface: the subscapular fossa Figure 83a

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Structures of the Scapula Posterior surface Figure 83c

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The Upper Limbs Arms, forearms, wrists, and hands Note: arm (brachium) = 1 bone, the humerus

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The Humerus Figure 84

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The Humerus Also called the arm The long, upper armbone Articulates with the pectoral girdle

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The Forearm Figure 85

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The Forearm Also called the antebrachium Consists of 2 long bones: ulna (medial) radius (lateral)

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Ulna: The Olecranon Superior end of ulna Point of elbow Superior lip of trochlear notch Articulates with trochlea of humerus

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The Wrist Figure 86

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The Wrist 8 carpal bones: 4 proximal carpal bones 4 distal carpal bones allow wrist to bend and twist

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Metacarpal Bones The 5 long bones of the hand Numbered IV from lateral (thumb) to medial Articulate with proximal phalanges

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Phalanges of the Hands Pollex (thumb): 2 phalanges (proximal, distal) Fingers: 3 phalanges (proximal, middle, distal)

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The Pelvic Girdle Figure 87

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The Pelvic Girdle Made up of 2 hipbones (ossa coxae) Strong to bear body weight, stress of movement Part of the pelvis

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Os Coxae Made up of 3 fused bones: ilium (articulates with sacrum) ischium pubis

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The Acetabulum Also called the hip socket Is the meeting point of the ilium, ischium, and pubis Is on the lateral surface of the os coxae Articulates with head of the femur (lunate surface)

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The Pelvis Figure 88

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

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Divisions of the Pelvis Figure 89

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Divisions of the Pelvis True pelvis: encloses pelvic cavity False pelvis: blades of ilium above arcuate line

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The True Pelvis Pelvic brim: upper edge of true pelvis encloses pelvic inlet

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Comparing the Male and Female Pelvis Figure 810

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Comparing the Male and Female Pelvis Female pelvis: smoother lighter less prominent muscle and ligament attachments

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Pelvis Modifications for Childbearing 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

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The Lower Limbs Functions: weight bearing motion Note: leg = lower leg; thigh = upper leg

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Bones of the Lower Limbs Femur (thigh) Patella (kneecap) Tibia and fibula (leg) Tarsals (ankle) Metatarsals (foot) Phalanges (toes)

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The Femur The longest, heaviest bone Figure 811

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The Patella Figure 812

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The Patella Also called the kneecap A sesamoid bone Formed within tendon of quadriceps femoris Base attaches quadriceps femoris Apex attaches patellar ligament

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The Tibia Figure 813

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The Tibia Also called the shinbone Supports body weight Larger than fibula Medial to fibula

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The Fibula Attaches muscles of feet and toes Smaller than tibia Lateral to tibia

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The Ankle Also called the tarsus: consists of 7 tarsal bones Figure 814a

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Bones of the Ankle Talus: carries weight from tibia across trochlea Calcaneus (heel bone): transfers weight from talus to ground attaches Achilles tendon Cuboid bone: articulates with calcaneus

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Feet: Metatarsal Bones 5 long bones of foot Numbered IV, medial to lateral Articulate with toes

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Feet: Phalanges Phalanges: bones of the toes Hallux: big toe, 2 phalanges (distal, proximal) Other 4 toes: 3 phalanges (distal, medial, proximal)

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Feet: Arches Arches transfer weight from 1 part of the foot to another Figure 814b

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Studying the Skeleton Reveals characteristics: muscle strength and mass (bone ridges, bone mass) medical history (condition of teeth, healed fractures) sex and age (bone measurements and fusion) body size

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Male and Female Skeletons Table 81