OsteologyOsteologyOsteology
Dr. Carmen E. RexachAnatomy 35
Mt San Antonio College
Functions of the Skeletal System:
• Support• Movement• Protection• Hemopoiesis• Electrolyte balance (Ca++/PO4
-3)• Acid-base balance• Storage of heavy metals
General Classification of Individual Bones
• By shape– Long– Short– Flat– irregular
• Long bones– longer than
wide– have a marrow
cavity– Ex: femur,
humerus
• Short bones– Cube shaped– Carpals and tarsal
• Flat bones– Broad surfaces for
muscle attachment– Enclose and protect
soft organs – Ex: roofing bones of
skull, scapula, clavicle
• Irregular bones– Varied shapes– Prominent surfaces – Ex: vertebrae,
sphenoid bone
General Classification of Individual Bonesby developmental location
• Sesamoid• intramembranous
development within a tendon
• Ex: patella
• Sutural (Wormian)• intramembranous
development within a suture
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
• Head– prominent condyle on a
neck• Anatomical neck• Surgical neck
anatomical
surgical
Surface features:non-articular (prominences)
• Crest or line– narrow ridge
• Tuberosity– large roughened surface
• Epicondyle– a roughened projection
next to a condyle
• Tubercle– small rounded rough
process• Trochanter
– massive roughened process (femur only)
• Process– any marked bony
prominence• Spine
– a long slender process
• Fossa– a flattened shallow
depression• Sulcus
– narrow, long groove• Alveolus
– a socket (teeth)• Sinus
– a cavity
• Meatus– blind ended canal (temporal
bone)• Fissure
– a wide slit in bone• Foramen (foramina)
– any opening in bone• Canal
– long foramen
Surface features:depressions/openings
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
• line the inner periosteum• produce new bone cells
through mitosis– Osteoblasts
• secrete matrix• high metabolic rate• Osteoblasts trapped in
lacunae– Osteocytes
• highly branched• surrounded by matrix• low metabolic rate
– Osteoclasts• fixed macrophage• Break down old bone
cells– bone lining cells
• line the surface of bones
• regulate calcium and phosphate passage
Multinucleated<150μm in diameter
On bone surface
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
80±187±1Total2525Rib cage26±133±1Vertebral column11Hyoid66Auditory ossicles1414Facial88CranialAdultFetusStructure
Number of bones: appendicular skeleton
206217Total skeleton126130 Total6060Lower extremities26Pelvic girdle6060Upper extremities44Pectoral girdle
AdultFetusStructure
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