Appendicular Skeleton

• Appendicular skeleton


  Composed of 126 bones of the limbs (appendages) and the pectoral and pelvic girdles, which attach the limbs to the axial skeleton
• Bones of the Shoulder Girdle

  • Clavicle
  • Scapula
• Clavicle


  • Slender, doubly curved bone
  • Attaches to the manubrium of the sternum medially and to the scapula laterally
  • Acts as a brace to hold the arm away from the top of the thorax and helps prevent shoulder dislocation
• Scapula


  • Commonly called "wings" because they flare when we move our arms posteriorly
  • Not directly attached to the axial skeleton; loosely held in place by trunk muscles
  • Triangular shape with a flattened body and three borders (superior, medial, lateral)
  • Has three angles (superior, inferior, lateral)
  • Glenoid cavity in the lateral angle receives the head of the arm bone
  • Has two important processes: acromion and coracoid process
• Acromion


  • Enlarged lateral end of the spine of the scapula
• Coracoid process


  • Beaklike process that points laterally over the top of the shoulder and anchors some of the muscles of the arm
• Bones of the Upper Limbs


  • Arm
  • Forearm
  • Hand
• Humerus


  • Typical long bone of the arm
  • Proximal end has a rounded head that fits into the shallow glenoid cavity of the scapula
  • Has greater and lesser tubercles as sites of muscle attachment
  • Midpoint of the shaft has a roughened area called the deltoid tuberosity
  • Distal end has the medial trochlea and lateral capitulum that articulate with bones of the forearm
  • Has depressions (coronoid fossa, olecranon fossa) and epicondyles that allow movement of the elbow
• Radius


  • Lateral bone of the forearm
  • Proximal end has a disk-shaped head that forms a joint with the capitulum and humerus
  • Has a radial tuberosity where the tendon of the biceps muscle attaches
• Ulna


  • Medial bone of the forearm
  • Proximal end has the anterior coronoid process and posterior olecranon process separated by the trochlear notch, which grip the trochlea of the humerus
• Bones of the Hand

  • Carpals
  • Metacarpals
  • Phalanges
• Carpals


  • Eight bones arranged in two irregular rows of four bones each, forming the wrist
• Metacarpals


  • Numbered 1 to 5 from the thumb side of the hand toward the little finger
  • Heads become the "knuckles" when the fist is clenched
• Phalanges


  • Bones of the fingers
  • Each hand contains 14 phalanges, with 3 in each finger except the thumb which has 2
• Bones of the Pelvic Girdle

  • Ilium
  • Ischium
  • Pubis
• Pelvic Girdle


  • Formed by two coxal bones (hip bones)
  • Attached securely to the axial skeleton to bear the weight of the upper body
  • Protects the reproductive organs, urinary bladder, and part of the large intestine
• Ilium


  • Largest part of the hip bone
  • Connects posteriorly to the sacrum at the sacroiliac joint
  • Has an iliac crest that is an important landmark for injections
  • Ends anteriorly in the anterior superior spine and posteriorly in the posterior superior spine
• Ischium


  • The "sit down" bone
  • Has an ischial tuberosity that receives body weight when sitting
  • Has an ischial spine that narrows the outlet of the pelvis during childbirth
• Pubis


  • Most anterior part of the hip bone
  • Fuses anteriorly with the other pubic bone to form the pubic symphysis
  • Together with the ischium, forms the obturator foramen
• Acetabulum


  • Deep socket formed by the fusion of the ilium, ischium, and pubis that receives the head of the thigh bone
• Characteristics of Male and Female Pelvis

  • Female pelvis has a larger and more circular inlet
  • Female pelvis is shallower with lighter and thinner bones
  • Female ilia flare more laterally
  • Female sacrum is shorter and less curved
  • Female ischial spines are shorter and farther apart, resulting in a larger outlet
  • Female pubic arch is more rounded with a greater angle
• Bones of the Lower Limbs

  • Thigh
  • Leg
  • Foot
• Femur


  • Heaviest and strongest bone in the body
  • Proximal end has a ball-like head, neck, and greater and lesser trochanters
  • Trochanter, intertrochanteric crest, and gluteal tuberosity are sites for muscle attachment
  • Distal end has lateral and medial condyles that articulate with the tibia and a patellar surface that forms a joint with the patella
• Tibia


  • Larger and more medial of the two leg bones
  • Proximal end has medial and lateral condyles that articulate with the femur
  • Has a tibial tuberosity where the patellar ligament attaches
  • Distal end has a process called the distal malleolus that forms the inner bulge of the ankle
• Fibula


  • Thin, sticklike bone that lies alongside the tibia
  • Distal end forms the lateral malleolus, the outer part of the ankle
• Tarsus


  • Posterior half of the foot, composed of seven tarsal bones
  • Largest tarsals are the calcaneus (heel bone) and talus
• Metatarsals


  • Five bones forming the sole of the foot
• Phalanges


  • Fourteen bones forming the toes
  • Each toe has 3 phalanges except the great toe which has 2
• Foot Arches


  • Medial and lateral longitudinal arches, and a transverse arch
  • Ligaments and tendons help hold the bones in the arched position
• Types of Joints


  • Fibrous
  • Cartilaginous
  • Synovial
• Fibrous Joints


  • Bones united by fibrous tissue
  • Sutures of the skull have essentially no movement
  • Syndesmoses have more "give" than sutures
• Cartilaginous Joints


  • Bone ends connected by cartilage
  • Pubic symphysis and intervertebral joints are amphiarthrotic
  • Epiphyseal plates and first rib-sternum joints are synarthrotic
• Synovial Joints


  • Articulating bone ends separated by a joint cavity containing synovial fluid
  • Features: articular cartilage, fibrous articular capsule, joint cavity, reinforcing ligaments, bursae
• Types of Synovial Joints

  • Plane
  • Hinge
  • Pivot
  • Condylar
  • Saddle
  • Ball-and-socket
• Plane Joint


  • Articular surfaces are essentially flat, allowing only short slipping or gliding movements
• Hinge Joint


  • Cylindrical end of one bone fits into trough-shaped surface on another, allowing angular movement in one plane
• Pivot Joint


  • Rounded end of one bone fits into a sleeve or ring of bone, allowing rotation around the long axis
• Condylar Joint


  • Egg-shaped articular surface fits into an oval concavity, allowing movement in two axes but not rotation
• Saddle Joint


  • Each articular surface has both convex and concave areas, allowing essentially the same movements as condylar joints
• Ball-and-Socket Joint


  • Spherical head of one bone fits into a round socket in another, allowing movement in all axes including rotation