Bài giảng Biology 25: Human Biology - Chapter 11

Skeletal System Components: Bones, ligaments, and cartilage. Functions: Along with muscular system: Movement and locomotion. Mechanical work: Lifting, pulling, pushing objects. Body support. Protection of delicate internal organs (brain, heart, lungs, etc.) Calcium storage Homeostatic Role: Helps maintain constant blood calcium levels.

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Chapter 11Biology 25: Human BiologyProf. GonsalvesLos Angeles City CollegeLoosely Based on Mader’s Human Biology,7th editionSkeletal SystemComponents: Bones, ligaments, and cartilage.Functions: Along with muscular system:Movement and locomotion.Mechanical work: Lifting, pulling, pushing objects.Body support.Protection of delicate internal organs (brain, heart, lungs, etc.)Calcium storageHomeostatic Role:Helps maintain constant blood calcium levels.Skeletal System: Protection, Movement, & SupportConnective TissueLarge amounts of extracellular (ECF) material in the spaces between connective tissue cells.4 Types of Connective Tissue:Connective tissue properCartilageBoneBloodConnective Tissue ProperLoose connective tissue:Scattered collagen and tissue fluid.Dermis of skinDense fibrous connective tissue:Regular arranged.Collagen oriented in same direction.TendonsIrregularly arranged.Resists forces applied in many directions.Capsules and sheathsCartilageChondrocytes.Supportive and protective tissue.Elastic properties to tissues.Precursor to many bones.Articular surfaces on joints.BoneHydroxyapatite crystalsOsteoblasts:Bone-forming cellsOsteocytes:Trapped osteoblasts: less activeOsteoclasts:Bone resorbing cellsGeneral Anatomy of a Long Bone Diaphysis - main shaft of the boneEpiphysis - large end of the boneMetaphysis - where above meet during bone growthArticular Cartilage - covers epiphysis, reduce frictionPeriosteum - dense, white covering around the bonefibrous layer - blood, lymph, nerves pass throughosteogenic layer - where bone cells originateMedullary (marrow) Cavity - adults, yellow marrowEndosteum - lines medullary cavity, houses bone cells Microanatomy of Compact (Dense) Bone General Featuresfew empty spaces (dense)thicker in diaphysis than epiphysisconcentric ring-like structureOsteon (Haversian System) - Components of Compact Bonecentral (Haversian) canal - vessels and nervesosteocytes - mature bone cells (from osteoblasts)lacunae - spaces where osteocytes residelamellae - rings around canal, house lacunaecanaliculi - projections from lacunae + osteocytesSupporting Structuresperforating (Volkmann) canals - run perpendicularinterstitial lamellae - between osteons Ossification: The Formation of Bone During DevelopmentEndochondral Ossification (replacing hyaline cartilage)cartilage "bone model" formed in the embryoperichondrium - membrane around the cartilagevessel penetrates cartilage, brings osteoblastscartilage converted into compact boneperichondrium --> periosteumchondrocytes gradually hypertrophy and dievessels move into space and convert to boneprimary ossification center - in diaphysissecondary ossification center - in epiphysisepiphyseal plate - between the two, still cartilage Bone Remodeling - Spongy Bone Converted to Compact Boneosteoclasts - resorption of old bone tissuelysosome release of digestive enzymescell "phagocytoses" (engulfs) particlesosteoblasts - lay down new bone in its placebone constantly undergoes remodeling throughout lifeCa needed in muscle, nerve, blood clotting fractures repaired immediatelyFactors essential for proper bone growthCa and P in proper amount in diettrace amounts of Boron and ManganeseVitamin D - regulates Ca metabolismVitamin C - maintenance of bone matrixVitamin A - osteoclast/blast functionVitamin B12 - osteoblast functionHuman Growth Hormone (HGH) - pituitaryCalcitonin - thyroid, Ca absorption to boneParathormone - parathyroid, Ca release to bloodSex Hormones - Testosterone + Estrogen Classification of Bones Long Bones – considerably longer than wide; shaft with 2 ends (most limb bones, finger bones, etc.)Short Bones – roughly cube shaped (wrist bones)Sesamoid bone – short bone within a tendon (patella)Flat bones – Flattened, thin, and usually curved (most cranial bones, ribs, sternum, and scapula)Irregular bones – irregularly shaped (vertebrae, hip bones) Bone ClassificationThere are two divisions of the adult skeleton with a total of 206 bonesAxial Skeleton includes 80 bonesSkull (22), middle ear ossicles (6), hyoid (1), vertebral column (26), and thorax (25)Appendicular Skeleton includes 126 bonesPectoral girdle (4), upper extremities (60), pelvic girdle (2), and lower extremities (60)Synovial JointsStructureany joint where there is a space between bonessynovial cavity - space between the bonesfreely moveable joints (diarthrotic)articular cartilage - covers articular surfacearticular capsule - encloses the cavity itselffibrous capsule - attached to periosteumligaments - clearly defined connectionssynovial membrane - inner layer of capsuleproduces synovial fluidreduces friction in the jointaccessory ligaments - additional supportextracapsular - outside capsuleintracapsular - within capsulearticular discs (menisci) - pads between bonesbursae - sac-like structures that reduce frictionbetween tendons, muscle, ligaments: and bone
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