SKELETON FUNCTIONS OF BONE:

SKELETON FUNCTIONS OF BONE: SKELETON: 1. Performs a mechanical function in forming the skeletal support of the body and in forming a leverage system whereby work and movement are possible. 2. Serves as attachment points for muscles. 3. Protects vital organs of the cranial and thoracic cavities. 4. Serves as a reservoir of minerals supplying calcium and phosphate to the blood. 5. Contains red marrow, with the function of producing formed elements of the blood. 1. Axial Skeleton (80 bones) 2. Appendicular Skeleton (126 bones) AXIAL SKELETON: I. SKULL 28 BONES + Associated bone (1) CRANIUM (EIGHT (8) BONES THAT SURROUND AND PROTECT THE BRAIN) A. Frontal bone (1) B. Occipital (1) 1. foramen magnum 2. occipital condyle C. Parietal bones (2) D. Sphenoid (1) 1. greater wing (orbital surface) 2. lesser wing 3. sella turcica (pituitary gland or hypophysis "sits" here) E. Temporal bones (2) 1. petrous portion- contains middle (containing ear ossicles) & inner ear (cochlea) 2. internal acoustic meatus (cranial nerve VIII exits) 3. Squamous portion 4. external acoustic (auditory) meatus leading to tympanic membrane 5. mastoid process (contains air sinus) 6. zygomatic process (articulates w/zygomatic bone to form the zygomatic arch) 7. carotid canal 8. jugular foramen 9. mandibular fossa 10. styloid process F. Ethmoid (1) Rev. 9/24/08 1

1. cribriform plate 2. crista galli 3. perpendicular plate (part of nasal septum) 4. superior and middle nasal conchae (turbinates) FACIAL BONES (FOURTEEN (14) BONES) G. Nasal bones (2) form bridge of the nose H. Maxillae (2) 1. palatine process of maxilla 2. alveolar process (margin) contains alveoli for the roots of the upper teeth I. Zygomatic bones (2) 1. with zygomatic process of the temporal forms the zygomatic arch J. Mandible (1) 1. body 2. ramus 3. mandibular condyle 4. coronoid process 5. alveolar process (margin) contains alveoli for the roots of the lower teeth K. Lacrimal bones (2): location of the nasolacrimal duct L. Palatine bones (2) M. Vomer (1) 1. with perpendicular plate of the ethmoid forms the nasal septum N. Inferior nasal conchae (turbinates) (2) O. Hyoid (1) (note: not part of the skull) SUTURES* OF THE SKULL (There are many but we will learn these): 1. Coronal between frontal and parietal bones 2. Lambdoid between parietal and occipital bones 3. Sagittal between parietal bones 4. Squamous between part of the temporal and parietal bones * Sutural (wormian) bones found within the sutures of many people; they are sesamoid# bones #sesamoid bones form within fibrous tissue FONTANELS unossified membranous areas between cranial bones on an infant. Major fontanels named Frontal (Anterior), Occipital (Posterior), Sphenoidal (Anterolateral) and Mastoid (Posterolateral). They are important during the birth of the baby allowing temporary molding of a baby's head as it passes through the birth canal. Rev. 9/24/08 2

AIR SINUSES four of the cranial bones and one of the facial bones contain air spaces or sinuses. Functions: 1. Decrease weight of the skull 2. Act as resonance chambers in the production of the voice A. Paranasal sinuses 1. Frontal sinuses 2. Maxillary sinuses 3. Sphenoid sinuses 4. Ethmoid sinuses B. Mastoid sinuses in each temporal bone; continuous with nasopharynx (superior portion of the throat). II. BONES OF THE VERTEBRAL COLUMN ADULT contains 26 separate bony segments (vertebrae) CHILDREN 33 or 34 vertebrae ADULT CHILD Neck (cervical) 7 7 Chest (thoracic) 12 12 Small of the back (lumbar) 5 5 Sacrum (fusion of 5) 1 5 UCoccyx (fusion of 4 or 5) 1 4 or 5 26 33 or 34 Systematic Naming of Vertebrae: C-1 to C-7, T-1 to T-12, L-1 to L-5, etc. Each vertebra except the first two cervical have: 1. Body (anterior) a. serves as the weight bearing part b. an intervertebral disc (symphysis) of compressible fibrocartilage acts as a cushion and shock absorber between each pair of vertebral bodies. 2. Pedicles extending posteriorly from the body as two short, thick projections 3. Laminae pair of broad, flat plates extending from the pedicles and fusing at the midline. 4. Spinous process projects posteriorly at the point of laminar fusion. 5. Transverse processes entending laterally from the junction of the pedicle and lamina of either side. 6. Vertebral foramen large opening in each vertebra through which the spinal cord passes. Rev. 9/24/08 3

7. Superior and inferior articular processes project vertically near the junction of pedicles and laminae. Superior process of one vertebra articulates with inferior surface of the next. CERVICAL VERTEBRAE- all have transverse foramina for vertebral arteries & veins ATLAS (C-1) first cervical vertebra supports the head, has no body or spinous process. AXIS (C-2) second cervical vertebra has large, toothlike projection, the odontoid process or dens which fits into anterior portion of the atlas and forms axis of rotation (pivotal joint) for the skull THORACIC VERTEBRAE have facets to articulate with the ribs. LUMBAR VERTEBRAE lack facets and are very large. SACRUM formed by the fusion of five sacral vertebrae forms the posterior portion of the pelvic girdle. COCCYX (tailbone) formed by the fusion of four or five rudimentary vertebrae. VERTEBRAL COLUMN Normal curvatures are normally four curves. 1. Thoracic and sacral curves (primary curves) present at birth. 2. Cervical curve (secondary curve) appears at about 3 months when infant begins to hold it's head up. 3. Lumbar curve (secondary curve) appears when infant begins to walk. Exaggerated curves may be due to injury, disease or poor posture. 1. Increase in thoracic curvature is called kyphosis or hunchback. 2. Increase in lumbar curve called lordosis or swayback. 3. A lateral curvature of the spine is called scoliosis. III. BONES OF THE THORAX a cone shaped cage to protect the organs of the chest and it Rev. 9/24/08 4

also plays an important role in respiration. A. Twelve pairs of ribs form the "bars" of the cage. Ribs 24 (12 pair) slender, curved, relatively flexible bones (flat bones). All attached posteriorly to the thoracic vertebrae. Anteriorly none of the ribs are actually attached to the sternum rather, they are attached via bars of hyaline cartilage (costal cartilage). First seven pairs of ribs called true ribs or VERTEBROSTERNAL ribs since their costal cartilages actually articulate with the sternum. Last five ribs are called false ribs: a. superior three pairs called VERTEBROCHONDRAL ribs since their costal cartilages turn upward to join the cartilage of the rib above. b. last two pair of ribs have no anterior attachment and are called floating or VERTEBRAL ribs. Typical rib has: 1. Head and tubercle which articulate with facets on vertebra of the thorax. 2. Shaft curves around the side of the chest. 3. Note that ribs curve downward from posterior to anterior. B. Sternum (breastbone) anteriorly C. Vertebral column posteriorly. APPENDICULAR SKELETON: UPPER EXTREMITIES (32 bones each) A. Shoulder girdle 1. Clavicle ( collar bone ) 2. Scapula ( shoulder blade ) a. glenoid cavity b. spine c. acromion d. coracoid process e. margins or borders (superior, axillary, vertebral) f. supraspinous and infraspinous fossae B. Humerus (arm) 1. head 2. capitulum Rev. 9/24/08 5

4. trochlea 5. medial and lateral epicondyles 6. olecranon fossa 7. coronoid fossa C. Radius and Ulna (forearm) 1. Radius a. head b. neck c. radial tuberosity d. styloid process 2. Ulna a. olecranon process b. trochlear notch (semilunar notch) c. coronoid process d. radial notch e. styloid process D. Carpus (wrist) -eight small bones (also, carpal bones) NOT "carpals" E. Metacarpus (palm of hand) (also, metacarpal bones) NOT "metacarpals" 1. five bones forming the palm of the hand 2. numbered 1-5, thumb is number one F. Phalanges (skeletal elements of the fingers) 1. each finger has three: proximal, middle and distal phalanx 2. thumb (Pollex) has only two: proximal and distal phalanx LOWER EXTREMITIES (30 bones each) A. Bones of the Pelvis 1. Sacrum (formed from 5 sacral vertebrae in child) 2. Coccyx 3. Os Coxae (2) hip bones: form the pelvic girdle a. three portions or regions (Note: these are separate bones in child) 1) ilium or iliac portion 2) ischium or ischial portion 3) pubis or pubic portion b. acetabulum (means "vinegar bowl") articulates with head of femur c. obturator foramen (obturator: to stop up; obturator membrane) d. pubic symphysis e. sacroiliac joint f. iliac crest f. greater sciatic notch g. angle of pubic arch (male: less than 90 ; female: more than 90 ) B. Femur (thigh region) 1. head 2. neck 3. greater and lesser trochanters Rev. 9/24/08 6

4. lateral and medial condyles C. Patella (kneecap) a sesamoid bone within the patellar tendon which protects the knee joint. D. Tibia and fibula (leg region) 1. Tibia (shin bone; medial) a. lateral and medial condyles b. tibial tuberosity c. medial malleolus 2. Fibula (smaller bone of the leg; lateral) a. lateral malleolus E. Tarsus (ankle; consists of seven bones) (also, tarsal bones) NOT "tarsals" 1. calcaneus (heelbone, largest) 2. talus articulates foot with tibia F. Metatarsus (instep; consists of five bones; 1-5; big toe is 1) (also, metatarsal bones) NOT "metatarsals" G. Phalanges (skeletal elements of the toes) 1. each toe has three: proximal, middle and distal phalanx 2. big toe (Hallux) has only two: proximal and distal phalanx Rev. 9/24/08 7