Human Anatomy: Chapter 5 - The Structure and Function of Bones, Study notes of Anatomy

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Human Anatomy: Chapter 5

CONTENT

1. Movement
2. Protection and supporting soft tissue
3. Blood cell production
4. Energy storage (in yellow bone marrow)
5. Storage of calcium and phosphate - Functions of bone Perichondrium - surrounded by dense irregular connective tissue Extracellular matrix - Protein fibers embedded in a gel-like substance Chondroblasts - cells that produce cartilage matrix Chondrocytes - mature cartilage cells that reside in lacunae (protection) Avascular - no blood supply **blood added to cartilage forms bone Fibrocartilage - Thick collagen fibers: has great tensile strength, shock absorber -found on (Menisci of knee, intervertebral discs, pubic symphysis) Elastic cartilage - contains elastic fibers, provides flexibility (epiglottis and external ear)

Hyaline cartilage - flexible, but resilient; found in respiratory system (larynx, trachea, bronchi, costal cartilage, nose, articular cartilage, epiphyseal plate, fetal skeleton, etc.) -most prevalent **associated with blood entering and forming bone Axial skeleton - (trunk) skull, vertebral column, ribs and sternum Appendicular skeleton - (extremities) upper and lower limbs, scapula & clavicle, pelvic bones Long bone - longer length than width (ulna, radius, femur, etc.) Short bone - same length and width (capitate (carpal) bone, talus, etc.) Flat bone - protection and attachment sites (scapula, sternum) Irregular bone - unique shape (sphenoid bone, vertebra) Sesamoid bone - (like sesame seed) round-shaped (patella, sutural bone) Compact (cortical) bone - surrounds spongy bone, heavy and tough in nature Spongy (cancellous/trabecular) bone - surrounded by compact bone in long bones, appears like honeycomb or sponge Disaphysis - (shaft) compact bone surrounding the medullary cavity, contains yellow marrow

Metaphysis - connection between epiphysis & diaphysis; epiphyseal line or plate "growth plate" Epiphysis - (ends) exterior=compact; interior=spongy; Houses the red bone marrow Yellow bone marrow - medullary cavity in adults, stores fat cells Red bone marrow - hematopoiesis (found in epiphyses of humerus and femur) (and in flat bones: skull, pelvis, ribs, and sternum) Articular cartilage - over joint, surface acts as friction and shock absorber (avascular) Medullary cavity - marrow cavity (yellow marrow) osteo - bone tissue Periosteum - double layer membrane that covers compact bone (surrounds compacts bone) -made of 2 layers (fibrous and osteogenic layer) peri - around Fibrous layer - dense irregular outer layer of periosteum Osteogenic layer - inner layer of periosteum containing bone cell and blood vessels that nourish or help with repairs, osteoblasts are found here

Endosteum - thin layer that lines the medullary cavity, lines central canals, covers trabeculae of spongey bone (surrounds spongy bone) Diloe - 2 thin plates of compact or spongy bone or trabeculae in between -no shaft or epiphyses -diloe -red marrow in trabeculae -Stronger than long bones - structure of short, flat, irregular, and sesamoid bones Osteon - main structural unit of compact bone, elongated cylinders, oriented parallel to the long axis Lamellae - "layers" of compact bone Circumferential lamella - a bony lamella that encircles the outer or inner surface of a bone Interstitial lamella - an area between osteons that is a remnant of older osteons that have been partially destroyed during bone rebuilding or growth concentric lamella - ring of calcified matrix surrounding the Haversian canal, Adjacent collagen fibers run in opposite directions Central (Haversian) canal - opening in the center of an osteon, runs through lamella, carries blood vessels and nerve fibers (runs vertical)

Perforating canal - connect blood supply of periosteum to central canal and medullary cavity (perpendicular to central canal, horizontal) Lacunae - small spaces between the lamellae which contain osteocytes Canaliculi - small canals that connect the lacunae and central canal -latticework of thin plates of bone called trabeculae orientated along lines of stress -spaces in between struts are filled with red marrow -found in end of long bones and inside flat bones (hip bones, sternum, sides of skull, and ribs) -No osteons or concentric lamellae, has interstitial lamellae - Elements of spongy bone -a type of connective tissue as seen by widely spaced cells separated by matrix -4 types of cells in bone tissue - histology of bone Matrix - 25% water 25% collagen fibers 50% crystalized mineral salts

1. Osteogenic cells
2. Osteoblasts
3. Osteocyte
4. Osteoclast - 4 types of cells in bone tissue Osteogenic cells - stem cell (begins maturing into osteoblast) (bone growth)

Osteoblast - matrix- synthesizing cell responsible for bone growth (not totally mature yet) (bone growth) Osteocyte - mature bone cell that maintains the bone matrix, inside lacunae (bone growth) Osteoclast - bone-reabsorbing cell (break down of bones) -osteoclasts carve out small tunnels and osteoblasts rebuild osteons -osteoclasts form leak-proof seal around cell edges and secrete enzymes and acids beneath themselves -release calcium & phosphorus into interstitial fluid -osteoblasts take over bone rebuilding (There is a continual redistribution of bone matrix along lines of mechanical stress...femur is fully remodeled every 4 months) - bone remodeling Osteoporosis - -decreased bone mass At risk: white, thin, menopausal, smoking, drinking females with family history : Athletes who aren't menstruating due to decreased body fat & decreased estrogen levels : People allergic to milk or low calcium intake -adequate diet, weight-bearing exercise, & estrogen replacement therapy (for post-menopausal women) -Behavior when young may be most important factor - Prevention of osteoporosis -roughly every 10 years old compact bone is replaced with new (distal part of femur is replaced every 5- 6 months) -Involves 2 processes - bone remodeling -bone deposit (osteoblasts)

-Bone resorption (osteoclasts) - 2 Processes of bone remodeling -mechanical stress: Wolff's law -Calcium blood levels - controls remodeling of bone Mechanical stress - pull on bone by skeletal muscle and gravity Bone stress - -stress increases deposition of mineral salts and production of collagen -lack of mechanical stress results in bone loss (can be caused by reduced activity while in cast, astronauts in weightlessness, and bedridden person) Weight-bearing exercises - build bone mass (walking or weight-lifting)