The Appendicular Skeleton

THE SKELETAL SYSTEM The 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 Arm Forearm Hand Lower = leg Thigh Leg 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

Scapulae: triangular, paired, but don’t connect in back (adds thoracic flexibility)

Scapula Glenoid cavity articulates with the humerus Acromium articulates with clavicle Coracoid process projects anteriorly

Upper extremity Arm or Brachium = upper arm Forearm or Antebrachium 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

Right humerus, anterior view

Right humerus, posterior view

Forearm 2 bones: articulate with each other proximally and distally Radius is thinner proximally, like a spool of thread, and wide distally; ulna is slightly longer and looks like a monkey wrench (supposedly!) 2 bones: articulate with each other proximally and distally Interosseous membrane between them Ulna Olecranon hinges with the humerus forming elbow Styloid process distally Radius Contributes to wrist joint Styloid process anchors a ligament to wrist (thumb side)

Right forearm bones, anterior view

Right forearm bones, posterior view

In the anatomical position, the radius is lateral (thumb side); with pronation the palm faces posteriorly and the bones cross Left forearm Anatomical position Prone: body lying face down Suppine: body lying face up prone (you can remember prone if you think about how you would fall forward onto your face if you passed out) pronation moves the forearm into the prone position and supination moves it back to the anatomical position

Proximal and distal joints of the forearm proximal ulna

Hand Proximal is “wrist” – 8 carpal bones Palm of hand - 5 metacarpals Fingers (or digits) consist of miniature long bones called phalanges: thumb (“pollex”) has 2; fingers have 3: proximal, middle, distal Right hand, 2 views:

Pelvic Girdle (Hip Girdle) Strongly attached to axial skeleton (sacrum) Deep sockets 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

Hip bone (os coxae): 3 separate bones in childhood which fuse Ilium Ischium Pubis

Ilium Iliac crest Anterior superior iliac spine Greater sciatic notch Forms part of “acetabulum” (hip socket) which receives ball-shaped head of femur ilium

Ischium Body Ramus Ischial spine Ischial tuberosity Part of socket

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

Hip bones with labels

False (greater) and true (lesser) pelvis Ligaments

Pelvis and childbearing Male/female differences Large & heavy vs light & delicate Heart shaped pelvic inlet vs oval Narrow deep true pelvis vs wide & shallow Narrow outlet vs wide Less than 90 degree pubic arch vs more than 90 degree Birth canal changes shape as baby descends: head turns ¼ Higher: pelvic inlet (brim) - side to side largest Lower: pelvic outlet - largest in AP direction

Lower limb Thigh: femur Leg (lower leg) Tibia Fibula Foot

Thigh Femur is largest, longest and strongest bone in the body Head fits in socket (acetabulum) of pelvis Neck is weakest Greater trochanter Distal: lateral & medial condyles and epicondyles Patella: sesmoid bone

Right femur, anterior view

Right femur, posterior view

Leg Tibia: shin bone Fibula Interosseous membrane Medial and lateral condyles Tibial tuberosity Distal medial malleolus (medial ankle) Fibula Distal lateral malleolus (lateral ankle) Interosseous membrane

Right lower leg, anterior view

Foot Tarsus: 7 tarsal bones 5 metatarsals 14 phalanges Talus: articulates with tibia and fibula anteriorly and calcaneus posteriorly Calcaneus: heel bone Smaller cuboid, navicular, and 3 cunieforms (medial, intermediate and lateral) 5 metatarsals 14 phalanges Great toe is hallux

Right foot, superior (dorsal) view and inferior (plantar) view

Right foot, lateral and medial views

Arches