Divisions of Skeletal Systems

**Divisions of Skeletal System** * 206 bones in 2 divisions * Axial Skeleton: 80 bones (skull, vertebral column, thorax) * Appendicular Skeleton: 126 bones (limbs & girdles) **Surface Markings:** * Depressions (openings) * Processes (projections) **SKULL** **22 cranial bones:** * **Cranial Bones (8):** * Form cranial cavity, protect brain * Frontal Bone: Forehead * Parietal Bone: Sides + roof (vault) of cranial cavity * Sutures: Immovable joints between skull bones * Coronal, Sagittal, Lambdoid * Temporal Bone: Lateral sides + base of Cranium * Surface Features: * External Auditory Meatus (directs sound to inner ear) * Zygomatic Process (cheekbone) * Styloid Process: Attachment for muscles + ligaments of tongue & neck * Occipital Bone: Posterior most of cranium base * Surface Features: * External Occipital Protuberance (muscle ligament attachment) * Foramen Magnum: Opening for spinal cord * Occipital Condyles: Articulate with atlas * Sphenoid: Butterfly-shaped, articulates with all other cranial bones * Surface Features: * Sella Turcica: Houses pituitary gland * Superior Orbital Fissure: Passage of nerves & vessels * Pterygoid Processes * Ethmoid: Part of anterior cranial base, medial wall of orbits * Superior part of nasal septum, lateral walls of nasal cavity * Surface Features: * Crista Galli: Attachment for falx cerebri * Perpendicular Plate: Nasal septum * Superior, Middle Nasal Conchae: Form nasal conchae * **Facial Bones (14):** * Form face * Support entrances to digestive & respiratory systems * Protect & support special sense organs * Mandible: Lower jawbone, largest, strongest, moveable * Surface Features: * Condylar Process: Articulates with temporal bone, TMJ * Mental Foramen: Vessels, nerve passage **NASAL SEPTUM** * Formed from bone & cartilage * Divides nasal cavity into two halves **VOMER** * Inferior portion of nasal septum **MAXILLAE** * Upper jaw, separates nasal from oral cavity * Palatine process: Posterior part of hard palate **NASAL BONES** * Form bridge of nose **LACRIMAL** * Smallest facial bones, form medial part of orbit **ZYGOMATIC** * Prominence of cheeks, part of orbit **INFERIOR NASAL CONCHAE** * 2 eye sockets, formed by 7 bones, contains 5 foramina **ORBIT** * Eye socket, formed by 7 bones, contains 5 foramina **PARANASAL SINUSES** * Cavities within cranial & facial bones * Located near nasal cavity * Lighten skull, resonating chambers for speech * Mucous membranes line sinuses * Secretions drain into nasal cavity **HYOID BONE** * Does not articulate with any other bone * Ligament suspension to styloid process * Supports tongue * Attachment site for muscles of tongue, neck, & pharynx * Surface features: greater & lesser horns **FETAL SKULL** * Fontanelles: Unossified mesenchymal tissue * 2 major functions: * Allow shape & size modification during birth * Allow for rapid growth of brain during infancy **VERTEBRAL COLUMN** * Functions: protects spinal cord, supports head, neck, & trunk * Attachment point for ribs, pelvic girdle, muscles, & ligaments * 26 bones in 5 regions **Curves are stronger than straight line, maintain balance** * Cervical, thoracic, lumbar, sacral curves **Abnormal Curvatures - From Congenital, Developmental, or Pathological Causes** * Scoliosis: Lateral bending of column * Hyperkyphotic: Thoracic or sacral curve * Hyperlordotic: Lumbar or cervical curve **Parts of Vertebra:** * **Body:** Weight-bearing * **Vertebral Arch:** Forms foramen, encloses spinal cord * **Spinous & Transverse Processes:** Attachment site for muscles & ligaments * **Intervertebral Foramen:** Formed with adjacent vertebrae * **Intervertebral Disc:** Fibrocartilage, shock absorption **CERVICAL VERTEBRAE C1-C7** * Have transverse foramen * C1: Atlas, lacks body * C2: Axis, prominent dens * C3-C6: Bifid spinous processes * C7: Vertebral prominens **THORACIC VERTEBRAE T1-T12** * Pentagonal vertebral body * Additional facets for rib articulation (costal facets) * Spinous processes: long, flattened, pointing inferiorly **LUMBAR VERTEBRAE L1-L5** * Sturdy, largest vertebrae * Body is prominent * Spinous process: short, blunt, pointing posteriorly * **HERNIATED DISC:** Inner portion "pushes" through weak spot in outer portion * Pinches nearby nerve **SACRUM & COCCYX** * **SACRUM:** Fusion of 5 sacral vertebrae (S1-S5) * Foundation for pelvic girdle * Sacral foramina allow passage of nerves & vessels * **COCCYX:** Fusion of 4 coccygeal vertebrae **THORAX - CAGE** * Formed by sternum, ribs, & vertebrae * Protects vital organs, supports pectoral girdle * Anchors muscles for breathing, body movement **THORAX - RIBS** * 12 pairs of ribs * Strong but flexible, protection & support * Pairs 1-7: true ribs, direct articulation w/ sternum * Pairs 8-10: false ribs, indirect articulation w/ sternum via costal cartilage * Pairs 11-12: floating ribs, no sternal articulation * Each rib articulates w/ corresponding vertebrae **INTERCOSTAL SPACES** * Occupied by muscles, vessels, & nerves **APPENDICULAR SKELETON** * Primary function: aid in movement * Includes bones of the: * Upper & lower limbs (30 each) * Pectoral & pelvic girdles **PECTORAL GIRDLE** * Consists of clavicle + scapula * Attaches upper limb to vertebral column * Stabilized by muscles, shoulder & trunk muscles **CLAVICLE** * Transfers mechanical force for upper limb to trunk * **Sterno-clavicular joint:** medial articulation with manubrium * **Acromio-clavicular joint:** lateral articulation with acromion of scapula **SCAPULA** * “Shoulder blade”, single flat bone * Spine, acromion process, coracoid process * Glenoid cavity: shallow, articulates w/ humerus * **Glenoid cavity** * **Coracoid process** * **Spine** * **Acromion process** * **Scapular spine** * **Glenoid cavity** * **Coracoid process**