Chapter 3 - Ch 3 PDF

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Ch 3...

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Chapter 3 – The Skeletal System Bones: An Overview 

Function of bones o Movement o Storage of minerals o Blood cell formation

o Shape o Support o Protection 

Types of bones o Irregular bones – vertebrae o Sesamoid – patella, wrist, ankle

o Long bones – femur, humerus o Short bones – carpals, phalanges o Flat bones – sternum Structure of Bone Typical Long Bone 

Major features o Head: enlarged, rounded end o Neck: constricted area; attaches head to body o Body: main portion

Macroscopic structure  

Proximal and distal epiphysis Diaphysis

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Articular cartilage – hyaline cartilage; very thick hyaline covering the ends of the bone

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Spongy bone (red bone marrow) Periosteum

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Metaphysis Epiphyseal line

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Nutrient arteries Medullary cavity (yellow bone marrow) – present in adults Endosteum (lines medullary cavity)

Microscopic structure   

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Histology of bone o Connective tissue; cells separated by hard matrix Bone cells o Osteogenic cell – osteoblast – osteocyte - || - osteoclast Osteogenic cells o Undifferentiated cells o Surface cells (found in inner layer of periosteum, endosteum) o Can divide to replace themselves or can change into osteoblasts Osteoblasts o Surface cells o Cant divide

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o Change into osteocytes when surrounded by matrix o Form new matrix and collagen fibers o **”bone builders”** o **synthesize an secrete collagen fibers** Osteocytes o Mature bone cells o Cant divide

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o Osteoblast surrounded by matrix, enclosed in lacunae o Maintain bone tissue but don produce new matrix o **maintain daily metabolism** Osteoclasts o Large cells formed from fused monocytes (WBC) o Surface cells o Secrete enzymes that dissolve bone matrix o Function in bone growth, repair, remodeling o **move concentrated with endosteum** Bone tissue o Compact bone – dense o Spongy bone AKA cancellous bone – porous Bone matrix o Not completely solid  Small space for vessel and red bone marrow  Spongy bone has many spaces  Compact bone has very few o 25% water o 25% organic matrix (collagen fibers – strength, flexibility) o 50% inorganic matrix (mineral salts – hardness) o Mineralization (calcification)  Hardening of tissue when mineral crystals deposit around collagen fibers Compact or dense bone o Solid hard layer of bone o Composed of osteons

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o Forms shaft of long bone, external surface of all bones o Resists stresses produced by weight and movement Osteon (haversian system) o Concreteric rings (lamellae) of calcified matrix surrounding a haversian canal o **all compact bones are made up o haversian systems** o Osteocytes lie between lamellae in lacunae o **lacunae are located between lamellae** Osteocytes o Communicate with adjacent cells via processes that extend through canaliculi filled with ECF Spongy bone o Lattice work of thin plates of bone called trabeculae oriented along lines of stress o Spaces between trabeculae filled with red marrow o Found in ends of long bones and in flat bones Bones containing red marrow in adults o Flat bones    

Cranial Pelvis Ribs Sternum

o Proximal humerus and femur Bone Growth and Remodeling 

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Bone growth in length o At the epiphyseal plate  Cartilage cells are produced by mitosis on epiphyseal side of plate  Cartilage cells are destroyed and replaced b bone on diaphyseal side of plate o At age 18-25, epiphyseal plates close  Cartilage cells stop dividing, bones replaces cartilage (epiphyseal line) o Growth in length stops Bone growth in diameter o By appositional growth at the bone growth o Periosteal cells differentiate, changes into osteoblasts, form bone ridges then a tunnel around periosteal blood vessel o Concretic lamellae fill in tunnel to form an osteon Bone remodeling o Osteoclasts continuously carve out tunnels, osteoblasts rebuild osteons o Bone matrix is continuously redistributing alone lines of mechanical stress

Division of the skeletal system 

Skeletal system divisions o 206 bones, 2 divisions  Axial skeleton    

Skull Hyoid bone Thoracic cage

Appendicular skeleton    

Shoulder girdle Upper limbs Lower limbs Pelvic girdle

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Spinal column

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Axial skeleton o Fetal skull  “soft spots” between cranial bones  Passage through birth canal, growth of brain o Vertebral column  Functions  

Support Flexibility

 Protection of spinal cord  Attachment for muscles (movement)  Consists of 26 vertebrae  5 vertebral region  Cervical (7) in the neck  Thoracic (12) in the thorax  Lumbar (5) in lower back  Sacrum (5, fused)  Coccyx (4, fused) o Spinal curvatures  Primary curves  Thoracic and sacral; formed during fetal development  Secondary curves  Cervical forms when infant raises head  Lumbar forms when infant sits up and begins to walk o Intervertebral discs  Fibrocartilage ring with a pulpy center  Shock absorbers  Inferior to vertebrae C 2 −L5  Change in flexibility of the vertebral column o Thorax  Bony cage  

Sternum Ribs

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 Costal cartilages  Thoracic vertebrae  Houses, protects thoracic organs  Allows breathing, flexible Appendicular skeleton o Pectoral (shoulder) girdle  Scapula and clavicle  Clavicle articulates with sternum  Scapula articulates with clavicle, held in place by muscles o Pelvic girdle (pelvis)  Pelvis = sacrum, coccyx, 2 os coxae o Pelvic brim  Separates false from true pelvis  False pelvis holds only abdominal organs o Pelvic inlet and outlet  Pelvic inlet (pelvic brim) – sacral promontory to superior edge of symphysis pubis  Pelvic outlet – inferior tip of coccyx to inferior edge of symphysis pubis o Sex differences  Male – heavier bones  Heart-shaped pelvic inlet  Long, narrow sacrum  Narrow pelvic outlet, pubis arch 90 degrees  Short, wide sacrum

Bony Features and Landmarks 

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Major features o Facet  Small, flattened joint surface o Condyle – rounded facet  Knuckle-like Projections o Process – prominent projection o Trochanter – large blunt process (on femur) o Tuberosity – large rounded prominence Ridges o Crest – thin ridge of bone

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o Spine – sharp ridge Depressions o Fossa – shallow depressions Openings o Foramen (foramina) – rounded/oval opening o Meatus – tubular passage o Sinus – filled cavity

Joints 

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Types of joints o Fibrous – immovable joint o Cartilaginous – little to no movement  Connection by hyaline cartilage/fibrocartilage  Partially moveable o Synovial – moveable Synovial joint o Secreted by synovial membrane o Mixture of interstitial fluid and hyaluronic acid  Lubricates joints  Supplies nutrients to, removes wastes from chondrocytes Other special features o Accessory ligaments  Extracapsular ligaments  Outside joint capsule (e.g. fibular collateral ligament, FCL)  Intracapsular ligaments  Within capsule (e.g. ACL) o Articular discs/menisci  Attached around edges to capsule  Allow 2 bones of different shape to fit tightly  Increase stability of knee o Bursae  Small sacs lines with synovial membrane  Fluid-filled cushions between bone and soft tissues (tendons) at moveable joints  Associated with “high wear and tear” joints (knee, elbow, shoulder)

Spine Curvature Disorders   

Scoliosis – abnormal lateral curvature on the vertebral column Kyphosis – abnormally rounded upper back Lordosis – significant inward curvature of the lower back

Aging and Skeletal System   

Birth – adolescence – bone growth is greater than bone loss Young adult – rates are equal Middle age and beyond – bone loss is greater than growth o Bones become more brittle and lose mass o After age 30 in females, 60 in males

Osteoporosis    

Condition f porous bones Osteopenia = low bone mass Bone reabsorption occurs more rapidly than bone deposition Spontaneous fractures during every day activities

Fracture 

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Any break in a bone o Partial  Incomplete, crack o Complete  Broken into 2 or more pieces o Closed (simple)  Doesn’t break through skin o Open (compound)  Broken ends protrude through skin Steps to repair o Phagocytosis remove dead bone cell tissue o Chondrocytes form fibrocartilage to broken bone ends o Fibrocartilage turns into spongy bone o Spongy bone I converted to compact bone

Diagrams to know...