2Divisions of the Skeletal System Subdivided into two divisions:Axial Skeleton – bones that form the longitudinal axis of the bodyAppendicular Skeleton – bones of the limbs and girdlesSkeletal system also includes joints, cartilages, and ligamentsThe joints give the body flexibility and allow for movement.
3Functions of Bones Support Protection Internal framework, support and anchor soft organsBones of legs act as pillars to support body trunkRib cage supports the throacic wallProtectionBones protect soft body organsEx. The skull protects the brainEx. The vertebrae surround the spinal cord.
4Functions of Bones Movement Storage Skeletal muscles use the bones as levers to move the body.Remember – skeletal muscles are attached to the bones by tendons.StorageFat is stored in internal cavities of bones.Bones store minerals, most importantlyCalcium – important to muscles, nerves, and bloodPhosphorous
5Functions of Bones Blood Cell Formation Hematopoiesis = blood cell formationOccurs within the marrow of certain bones
6Classification of Bones The adult skeleton is composed of 206 bones.2 types of bone tissue:Compact bone – dense and looks smoothSpongy bone – composed of needlelike pieces of bone and lots of open space
7Classification of Bones Bones are classified according to shape into 4 groups: long, short, flat, irregularLong: longer than they are wide, mostly compact boneShort: cube-shaped, mostly spongy boneFlat: thin, flattened, and usually curved, 2 thin layers of compact bone and a layer of spongy bone in middlemost bones of the skull, ribs, and sternumIrregular: the vertebrae and the hip bones
8Structure of a Long Bone The diaphysis makes up most of the bone’s length, composed of compact bone.Covered by a protective connective tissue membrane called the periosteumThe epiphyses are the ends of the long bone.Mostly spongy boneCartilage covers this part of the bone.Provides a smooth, slippery surface that lubricates the joints.
9Structure of BoneEpiphyseal line – thin line of bony tissue on epiphysisRemnant of the epiphyseal plateCauses the lengthwise growth of a long bone.By the end of puberty, bones stop growing and epiphyseal plates are completely replaced by bone.Mark the previous location of epiphyseal plateInteractive Web
10Structure of BoneIn adults, the cavity in the shaft of the bone stores adipose tissue (fat).Yellow MarrowIn infants, this area forms blood cells, and red marrow is found there.In adults, red marrow is only found in the cavities of spongy bone of flat bones and some long bones.
11Bone Markings Bumps, ridges, and holes in bones. Indicate where muscles, tendons, and ligaments attach, and where blood vessels and nerves passed.p.115
12Axial Skeleton head, neck, trunk SKULL HYOID BONE (upper neck, under jaw, mandible)VERTEBRAL COLUMN (spine/backbone)THORACIC CAGE (rib cage-12 pairs)STERNUM
13Appendicular Skeleton limbs and bones connecting the limbs to the:PECTORAL GIRDLE (scapula & clavicle)UPPER LIMBS (arms)PELVIC GIRDLE (coxal bones)LOWER LIMBS (legs)
14Microscopic Structure of Bone MATRIX composed of collagen and inorganic saltsOSTEOCYTES (mature bone cells) are enclosed in tiny chambers called LACUNAE and form concentric “ring” (layers) around a passageway called the HAVERSION CANALThe osteocytes are connected by small passages called CANALICULI (canaliculus) through which tiny “branches” or processes pass
16Microscopic Structure of Bone The circular layers of matrix material and osteocytes, along with the haversian canal, forms a unit called a HAVERSIAN SYSTEM.The haversian canals are interconnected by passages called VOLKMANN’S CANALS.All of these canals contain blood vessels and nerve fibers
18Bones of the Skull 1. Frontal - anterior portion above eyes 2. Parietal – one on each side of the skull, just behind frontal bone3. Occipital – forms the back of the skull and base of the cranium4. Temporal – forms parts of the sides and base of cranium5. Sphenoid – wedged between several other bones in anterior portion of the cranium6. Maxilla – forms upper jaws7. Mandible – lower jaws, only moveable bone of the skull
20Vertebral Column 3 types of vertebrae: Cervical: First 7 (neck)Thoracic: 12 vertebraeLumbar: Last 5 (lower back)Intervertebral disks: flexible cartilage, cushion vertebrae and absorb shockSacrum: fusion of 5 vertebraeCoccyx: fusion of 3-5 small, irregularly shaped vertebrae.“tailbone”
21Bones Ribs – Thoracic Cage, 12 pairs Pectoral Girdle: Shoulder. True Ribs – first seven pairs, attach directly to STERNUM by costal cartilageFalse Ribs – last five pairsFloating ribs – last two pairsPectoral Girdle: Shoulder.Two clavicles (collar bones) and two scapula (shoulder blade)
22Bones Arms: Upper arm – humerus. Lower arm – radius and ulna. Wrist – 8 small bones called carpelsFingers – Metacarpels, PhalangesPelvic Girdle: Hips. Two large bones called COXAL BONESLegs: Upper leg (thigh) - FEMUR. Lower leg – tibia & fibula.Ankle and Upper foot – 7 bones called TARSALS,Largest is the heel bone called the CALCANEOUSToes – Metatarsals, Phalanges
23Broken BonesA simple fracture is when the bone is broken cleanly but does not penetrate the skin.A compound/open fracture is when the bone is sticking through the skin.A greenstick fracture is when the bone cracks on one side only, not all the way through.A comminuted (say: kah-muh-noot-ed) fracture is when the bone is broken into many fragments or crushed.A compression fracture is when the bone is crushed.A depressed fracture is when the bone is broken and pressed inward (typical of skull fracture).A spiral fracture is when a break occurs from excessive twisting forces applied to the bone.