OsteologyOsteologyOsteology

Dr. Carmen E. Rexach Anatomy 35 Mt San Antonio College Functions of the Skeletal System:

•Support • Movement •Protection • Hemopoiesis ++ -3 • Electrolyte balance (Ca /PO4 ) • Acid-base balance • Storage of heavy metals General Classification of Individual Bones •By shape –Long –Short –Flat – irregular • Short bones – Cube shaped • Long bones – Carpals and tarsal – longer than wide – have a marrow cavity –Ex: femur, humerus • Flat bones • Irregular bones – Broad surfaces for –Varied shapes muscle attachment – Prominent surfaces – Enclose and protect – Ex: vertebrae, soft organs sphenoid bone – Ex: roofing bones of skull, scapula, clavicle General Classification of Individual Bones by developmental location

•Sesamoid • Sutural (Wormian) • intramembranous • intramembranous development within development within a tendon a suture •Ex: patella Composition of Long and Flat Bone

• Composition – Compact (dense) outside – Spongy (cancellous) inside •Flat bones = diploë •Long bones = trabeculae Regions of long bone

• Diaphysis • Epiphysis • Medullary cavity • Epiphyseal plate vs. epiphyseal line •Periosteum • Fibrous layer • Osteogenic layer • Sharpey’s fibers • Nutrient foramina •Endosteum • Articular cartilage General anatomy of long and flat bone Surface features: articular • Facet – smooth flat articulating surface • Condyle – smooth rounded articulating knob anatomical • Head – prominent condyle on a neck surgical • Anatomical neck •Surgical neck Surface features: non-articular (prominences)

• Crest or line •Tubercle – narrow ridge – small rounded rough •Tuberosity process – large roughened surface •Trochanter • Epicondyle –massive roughened process (femur only) – a roughened projection next to a condyle • Process – any marked bony prominence •Spine – a long slender process Surface features: depressions/openings

• Fossa •Meatus – a flattened shallow – blind ended canal (temporal depression bone) •Sulcus •Fissure –narrow, long groove – a wide slit in bone •Alveolus • Foramen (foramina) –a socket (teeth) – any opening in bone •Sinus •Canal –a cavity – long foramen Surface Features Surface Features Histology of Osseous Tissue

• Connective Tissue –Matrix • Non-living ground substance, stuff •Composition – 85% Hydroxyapatite crystals

»Ca10(PO4)6(OH)2

– 10% CaCO3 –Other minerals » Mg, Na, K, Fl, etc. –collagen – Cells Rickets and Osteomalacia Cells

– Osteogenic – Osteoclasts • line the inner periosteum • fixed macrophage • produce new bone cells • Break down old bone through mitosis cells – Osteoblasts – bone lining cells • secrete matrix • line the surface of • high metabolic rate bones • Osteoblasts trapped in • regulate calcium and lacunae phosphate passage – Osteocytes • highly branched • surrounded by matrix • low metabolic rate

On bone surface

Multinucleated <150μm in diameter Use HCl to dissolve bone minerals

Bone structure

•Compact bone – Solid bone tissue – Haversian system = osteon • Concentric lamellae and central canal • Lacunae, canaliculi • Spongy (cancellous) bone – First bone tissue to be laid down – trabeculae = lattice of thin plates – Spicules = rods and spines that fuse together to form trabeculae – Porous, filled with bone marrow – Arranged in lamellae, but few osteons – Light weight + strength to bone

Bone marrow

•Red – Myeloid tissue – Distribution in child vs. adult – hematopoietic • Yellow – Fatty marrow replaces red bone marrow in adults – Not hematopoietic, except in severe or chronic anemia • Can revert back to red bone marrow Development of Bones

• Ossification = osteogenesis – deposition of bone tissue – begins at approx 4 weeks gestation – apparent at approx 10 weeks – bone tissue arises as connective tissue from embryonic mesenchyme –Two types • Endochondral • intramembraneous Endochondral

• built on a hyaline cartilage model (perichondrium) • ossification results in spongy bone first then an outer layer of compact bone •1o in diaphysis, 2o in epiphysis Increasing the Diameter of Developing (Endochondral) Bone

• appositional growth on the outer surface • osteogenic cells differentiate into osteoblasts • matrix, blood vessels added to outer (periosteal) surface • osteoclasts remove matrix at the endosteal surface • marrow cavity enlarges as bone diameter enlarges

Intramembranous Bone Development (dermal ossification)

• roofing bones of the skull, mandible, clavicle • proceeds without a hyaline cartilage model • bone tissue deposited “between sheets” of fibrous connective tissue • spongy bone then outer layers of compact bone • Diploe = spongy bone between 2 layers of compact bone

Organization of the Skeleton (Major Divisions) •Axial – bones that form the axis of the body – support and protect the organs of the head, neck and trunk • Appendicular – the bones of the upper and lower extremities + 2 bony girdles that attach the extremities to the axial skeleton Number of bones: axial skeleton

Structure Fetus Adult Cranial 8 8 Facial 14 14 Auditory ossicles 6 6 Hyoid 1 1 Vertebral column 33±1 26±1 Rib cage 25 25 Total 87±1 80±1 Number of bones: appendicular skeleton

Structure Fetus Adult

Pectoral girdle 4 4 Upper extremities 60 60 Pelvic girdle 6 2 Lower extremities 60 60 Total 130 126 Total skeleton 217 206