The Skeletal System Overview

The Skeletal System

• Pectoral Girdle: Comprised of 4 bones: 2 scapulas and 2 clavicles.
• Clavicle: Long, curved bones found at the base of the neck.
• Scapula: Flat bones located on the posterior thorax (shoulder blades).
• Acromion Process: Superior lateral process that articulates with the manubrium of the sternum.
• Coracoid Process: Superior anterior process for muscle attachment.
• Glenoid Fossa: Depression (socket) that forms the shoulder joint; articulates with the head of the humerus.
• Humerus: Long bone of the arm.
• Head of the Humerus: Rounded proximal end of the humerus, articulates with the glenoid fossa.
• Trochlea: Medial pulley-shaped condyle that articulates with the trochlear notch of the ulna, forming a major part of the elbow joint.
• Capitulum: Articulates with the head of the radius at the elbow joint.
• Epicondyles: Medial and lateral eminences located above the 2 condyles at the distal end of the humerus.
• Ulnar: Medial bone of the forearm; largest bone of the forearm.
• Olecranon Process: Tip of the elbow, also known as the funny bone.
• Trochlear (Semilunar) Notch: Depression that articulates with the trochlea of the humerus.
• Head of the Ulna: Rounded distal end of the ulna.
• Styloid Process: Thin posterior process located on the distal end of the ulna.
• Radius: Lateral bone of the forearm; head articulates with the capitulum of the humerus.
• Carpals: Short bones that comprise the wrist; 8 bones total (4 in each hand).
• Metacarpals: Long bones of the palm and back of the hand; 5 in each hand.
• Phalanges: Bones of the fingers and toes.
• Fingers: Each finger contains 3 phalanges; each thumb contains 2 phalanges.
• Os Coxa: The large hip bone.
• Ilium: Superior portion of the pelvic girdle; top of the hip is called the crest.
• Ischium: Posterior portion of the hip bone; where one sits.
• Pubis: Anterior portion of the pelvic girdle.
• Acetabulum: Socket of the hip joint.
• Obturator Foramen: Largest foramen in the body.
• Femur: Largest bone of the thigh.
• Head of the Femur: Portion that fits into the acetabulum (socket of the hip).
• Trocanters: Large, blunt processes on the proximal end of the femur.
• Condyles of the Femur: Articulate with the tibia, forming the knee joint.
• Patella: Kneecap.
• Tibia: Medial bone of the leg; articulates with the femur to form the knee joint.
• Tibial Tuberosity: Prominence just below the knee.
• Medial Malleolus: Inner ankle.
• Fibula: Smaller, lateral bone of the leg.
• Tarsals: Short bones of the ankle.
• Calcaneus: Heel bone.
• Achilles Tendon: Tendon that attaches to the heel bone.
• Metatarsals: Long bones of the foot; 5 in each.
• Phalanges of the Feet: Total of 28, 2 in the big toe, and 3 in each of the other toes.

Additional Notes:

• Body: The main part of a bone
• Ramus: A branch of a bone
• Fissure: A narrow cleft or groove
• Fossa: A shallow depression
• Foramen: An opening through a bone
• Groove: A furrow or channel
• Meatus: A tube-like passageway
• Sinus: An air-filled cavity within a bone

Skeletal System Divisions

• Appendicular Skeleton: Bones of the limbs and the pectoral and pelvic girdles.
• Axial Skeleton: Bones of the skull, vertebral column, ribs, and sternum.
• Total Bone Count: The human skeleton has 206 bones.
• Auditory Ossicles: (3) Three small bones in each ear (6 total), responsible for hearing.
• Hyoid Bone: A single bone located in the neck beneath the tongue, essential for speech.
• Chest Bones: 25 bones comprise the bony chest, including the sternum and ribs.

Bone Disorders

• Osteoporosis: Decreased bone mass often due to low estrogen levels after menopause.
• Fracture: A break in a bone.
• Complete Fracture: Break extends all the way across the bone.
• Incomplete Fracture: Break extends partway across the bone.
• Greenstick Fracture: Bone bends on one side and breaks on the opposite side.
• Comminuted Fracture: Bone is broken into several pieces.
• Open (Compound) Fracture: Broken bone protrudes through the skin.
• Displaced Fracture: Broken bone ends are moved out of position.
• Reduction: Realignment of broken bone ends.

Joint Functions

• Arthrology: The study of the joints of the body.

• Joint: The site where two or more bones meet, permitting the movement of bones in the skeleton. Also known as articulations and arthroses.

• Synarthrosis: Immovable joint.

• Fibrous Connective Tissue: Connects the surfaces of synarthrosis joints.

• Cranial Sutures & Sternocostal Joints: Examples of synarthrosis joints.

• Amphiarthrosis: Slightly movable joint.

• Examples of Amphiarthrosis Joints: Intervertebral discs and pubic symphysis.

• Diarthrosis (Synovial Joint): Freely movable joint; characterized by:

  • Articular Cartilage: Covers the surfaces of the bones.
  • Joint Cavity: Space between the bones filled with synovial fluid.
  • Joint Capsule: Fibrous connective tissue that encloses the joint cavity.

Muscles

• Linea Alba: The line of white fibrous connective tissue between the rectus abdominis muscles.
• Iliopsoas Muscle: Located between the lumbar vertebrae and the femur; flexes the thigh.
• Diaphragm: Large muscle that contracts during breathing.
• Deltoid Muscle: Triangular muscle between the clavicle, scapula, and humerus; extends across the shoulder to the arm.
• Supraspinatus Muscle Located between the scapula and humerus.
• Biceps Brachii Muscle: Main flexor of the forearm.
• Synergist: Assists the prime mover.
• Infraspinatus Muscle: Located between the scapula and humerus.
• Brachialis Muscle: Muscle located below the biceps brachii; between the humerus and the ulna; flexes the forearm.
• Triceps Brachii: Large muscle of the posterior arm; extends the forearm.
• Flexor Carpi Ulnaris Muscle: Located on the anteriomedial surface of the forearm.
• Flexor Carpi Radialis Muscle: Located just lateral to the flexor carpi ulnaris.
• Flexor Digitorum Superficialis Muscle: Flexes the fingers.
• Brachioradialis Muscle: Large muscle of the anterior arm; extends from the lateral elbow to the wrist.
• Pronator Teres Muscle: Muscle located just medial to the brachioradialis.
• Pronator Quadratas Muscle: Pronates the hand (turns the palm down).