The Appendicular Skeleton Biology 260 M. Iyengar Classification of Bones • 206 bones in human skeleton – Grouped by bone shape • Short, long, irregular, and flat • Divided into two groups based on location – Axial skeleton • Skull, vertebral column, and thoracic cage – Appendicular skeleton • Pectoral girdle and upper limbs • Pelvic girdle and lower limbs Flat bone (sternum) Long bone (humerus) Irregular bone (vertebra), right lateral view Short bone (talus) Gross Anatomy of Bone Tissue • Bone Markings – External surface of bones are NOT smooth – Features may act as • Attachment places for muscles, ligament, or tendons • Joint surfaces • Openings for blood vessels or nerves Articulations / Joints • Fibrous – Bones joined by dense fibrous connective tissue – Most are immovable, but depends on their length – Three types: Sutures, Syndesmoses, & Gomphoses • Cartilaginous – Bones united by cartilage – Not highly movable – Two types: Synchondroses & Symphyses • Synovial – Bones separated by fluid-filled (synovial) joint cavity – All are diarthrotic (freely movable) – Include almost all limb joints – Have specific characteristics The Pectoral Girdle The Pectoral Girdle • Clavicle - appears straight when viewed anteriorly, and S-shaped when viewed superiorly or inferiorly • Sternal end articulates medially with manubrium at sternoclavicular joint • Acromial end articulates laterally with acromion process of scapula at the acromioclavicular joint The Clavicle The Pectoral Girdle • Scapula – triangular bone, sits on posterosuperior rib cage – three borders: medial, lateral, and superior – Coracoid process – hook-shaped projection on anterior surface – Subscapular fossa – inferior to coracoid process; provides an attachment site for subscapularis muscle – Glenoid cavity – shallow indentation found on lateral surface; articulates with humerus in shoulder joint – Spine – posterior ridge of bone; crosses from medial to lateral along superior scapula and terminates as acromion at acromioclavicular joint (AC) – Supraspinous fossa – superior to spine; infraspinous fossa is inferior The Scapula The Humerus • Proximal epiphysis has a medially oriented, ball-shaped humeral head; articulates with glenoid cavity at shoulder joint; • Capitulum – spherical knob on anterior and lateral aspect of distal epiphysis • Trochlea – spool-shaped knob on anterior and medial aspect of distal epiphysis • Olecranon fossa – deep indentation found on posterior aspect of distal epiphysis is a continuation of trochlea • Deltoid tubercle – main feature of diaphysis; provides a site of attachment for deltoid muscle • Medial and lateral epicondyle; provide attachment sites for muscles Bones of the forearm • Both articulate with humerus proximally and with carpal bones distally; articulate with one another both at a proximal and distal radioulnar joint – Ulna - Medial bone in anatomical position • Trochlear notch – U-shaped notch; articulates with trochlea of humerus • Olecranon – large protrusion found on posterior aspect of trochlear notch • Anterior lip of trochlear notch – projection called coronoid process; fits into coronoid fossa of humerus – Radius - Lateral bone in anatomical position, thumb side • Radial head – round and flattened structure; articulates with capitulum of humerus at elbow joint • Radial styloid process – at lateral tip of radius; forms lateral boundary of wrist and provides joint stabilization The Hand – Carpals - 8 short bones arranged in two rows containing four bones each *Starting point is the row proximal to the radius under the thumb Some → Scaphoid Lovers → Lunate Try → Triquetrum Positions → Pisiform That → Trapezium They → Trapezoid Can’t → Capitate Handle→ Hamate Carpals lunate triquetrum scaphoid pisiform trapeziod trapezium capitate hamate The Hand – Metacarpals - Numbered I–V from lateral to medial – Phalanges • a proximal, middle, and distal phalanx • Thumb (pollex) consists of only a proximal and distal phalanx Bones of the Pelvic Girdle • Formed by os coxae bones that articulate with the sacrum • Composed of three fused bones – All contribute to acetabulum, a deep socket on lateral aspect – Ilium and pubis also contribute to obturator foramen, an opening in each coxal bone, through which nerves and blood vessels travel Bones of the Pelvic Girdle • Ilium forms superior portion of coxal bone – Iliac crest – superior border of ala (flared superior “wing” of ilium) – Anterior superior iliac spine (ASIS) – bony projection found at anterior end of iliac crest • Just inferior to ASIS is a smaller ridge called anterior inferior iliac spine – Greater sciatic notch is a deep groove found inferior to posterior inferior iliac spine through which sciatic nerve passes – Posterior inferior iliac spine (PSIS) – bony ridge found at posterior end of iliac crest; just inferior to PSIS Bones of the Pelvic Girdle • Ischium – composed of ischial body and ramus; forms C- shaped posteroinferior portion of coxal bone – Posterior ischial body forms part of acetabulum – Ischial spine projects posteriorly and medially from body to which a ligament from sacrum attaches – Lesser sciatic notch, just inferior to spine, provides a passageway for blood vessels and nerves – Anterior ischial ramus – forms a portion of obturator foramen – Ischial tuberosity – prominent feature of posteroinferior aspect of ischium; bears all of upper body’s weight when seated Bones of the Pelvic Girdle • Pubis – smallest coxal bone – Superior pubic ramus – contributes to acetabulum structure – Pubic body and inferior pubic ramus – form parts of boundary of obturator foramen – Pubic symphysis – joint where two pubic bodies are separated by a fibrocartilaginous pad – Pubic arch – angle formed by two pubic bodies; differs between genders Gender Differences of the Pelvis The Femur • Largest and strongest bone in body and only bone in thigh – Proximal epiphysis features a prominent spherical head that articulates with acetabulum at hip joint – Greater trochanter – large protuberance found lateral to neck – Lesser trochanter, found medial and distal to greater trochanter – Linea aspera – prominent line found running down posterior shaft; – Medial and a lateral condyle which articulate with tibia at knee joint – Intercondylar fossa – indentation found between condyles of posterior distal epiphysis; smooth anterior surface is called patellar surface The Patella • Triangular patella (kneecap) articulates with patellar surface on femur – Sesamoid bone located within tendon of anterior thigh muscle – Proximal end of patella is base and distal tip is apex Point the apex away from you & lay it on a flat surface. It will lay on the side it belongs to. apex apex The lateral facet LAYS flat Tibia • Larger medial bone of leg; responsible for bearing weight of body – Two concave depressions, medial and lateral condyles, at proximal end of tibia articulate with femoral condyles in knee joint – Condyles are separated by a ridge called intercondylar eminence – medial malleolus, a palpable lump of bone found at ankle – Flat end of distal epiphysis is articular surface; component of ankle joint Fibula • Fibula – smaller lateral bone of leg, – Head of fibula articulates with lateral tibia proximally at proximal tibiofibular joint – Fibula expands into palpable lateral malleolus distal to distal tibiofibular joint – Lateral malleolus articulates with lateral talus; helps stabilize ankle joint The Foot • Tarsals - 7 short bones make up ankle region; connects leg to foot • Metatarsals, numbered I–V from medial to lateral • Phalanges in toes: toes II–V have proximal, middle, and distal phalanges; great toe or hallux has only a proximal and distal phalanx *Starting point is the row proximal to the tarsal under the toe Tiger → Talus Cubs → Calcaneus Need → Navicular MILC → Medial, Intermediate, Lateral cuneiform 7 Tarsal Bones talus calcaneus cuboid cuneiforms navicular.