Musculoskeletal Physiology 2023 - PDF

BONE TISSUE DR AISHA MOHD DIN Department of Basic Sciences  Understand how bones are classified by their macroscopic and microscopic features  Understand how bone is developed and physiologically controlled  Composed of bones, cartilages, and ligaments joined tightly together to form a st...

BONE TISSUE DR AISHA MOHD DIN Department of Basic Sciences  Understand how bones are classified by their macroscopic and microscopic features  Understand how bone is developed and physiologically controlled  Composed of bones, cartilages, and ligaments joined tightly together to form a strong, flexible framework for the body  Skeleton functions  Support  Protection  Movement  Electrolyte balance  Acid-base balance  Blood formation  Osseous tissue  Connective tissue with a hardened matrix  Deposition of calcium phosphate and other minerals  Mineralization and calcification  Classified based on shape and corresponding function  Four categories  Long bones  Short bones  Irregular bones  Flat bones  Epiphysis  Ends of the bone  Composed of cancellous (spongy) bone  Contains red bone marrow  Layered with hyaline cartilage  Diaphysis  Shaft of the bone  Composed of compact bone  Medullary cavity  Contains yellow bone marrow  Epiphyseal plate (children and adolescent)  Bone consist of cells, fibers & ground substance Osteoblasts  Four main types of bone cells Bone-forming cells  Osteogenic (osteoprogenitor) Found along endosteum and cells are stem cells found in the periosteum endosteum Stress and fracture stimulate cells to multiply and rebuild bone  Osteocytes Octeoclasts  Former osteoblasts that have Bone-dissolving cells been trapped in their lacunae Have 3 or 4 nuclei  Maintain bony matrix Ruffled border secrete hydrogen (H+)  Strain sensors (regulate bone and chloride (Cl– ) ions into the remodeling) extracellular fluid  Matrix  composed of inorganic and organic components  Inorganic component  85% Hydroxyapaptite  Composed mainly of CaPO4 salt  Organic components  Protein and carbohydrate  Collagen  Gives bones a combination of flexibility  Osteon (haversian system)  Basic structural unit of compact bone  Central (haversian) canal surrounded by concentric lamellae (matrix)  Perforating canals  Transverse or diagonal passages into the central canal  Originate at nutrient foramen  Composed by a network of spicules and trabeculae  Spaces filled with red marrow  Beams arranged to sustain stress commons.wikimedia.org  In an adult, red bone marrow occupies the medullary cavities in the regions colored red  Red marrow turns to fatty yellow bone marrow and no longer produces blood  Yellow bone marrow occurs in the long bones of the limbs  Ossification or osteogenesis  Formation of bone  Ossification methods  Intramembranous ossification  Endochondral ossification  Produces flat bones of skull and clavicles  Starts with osteoid  End with diploe  Bone develops from a hyaline model  Begins around the sixth week of fetal development and continues into a person’s 20s  Vertebrae, ribs, scapulae, pelvic bones, bones of the limbs  Bones grow in length and width  Bone Elongation (Growth in length)  Involves epiphyseal plates  Result from multiplication of chondrocytes  Epiphyseal plate is depleted in the late teens to early twenties and leaves a dense spongy bone called epiphyseal line  No gap between epiphysis and diaphysis when the epiphyseal plate is depleted (on x- ray)  A person cannot grow taller  Closes at different ages in different bones and in different regions of the same bone  Closure in various bones is often used in forensic science to estimate the age at death of a subadult skeleton  Appositional growth where the deposition of new tissue at the surface  Occurs by intramembranous ossification at the bone surface  Osteoblasts in the inner layer of periosteum deposit osteoid tissue on the bone surface, calcify it, and become trapped in it as osteocytes  Marrow cavity widens as bone increases in diameter  Osteoclasts of the endosteum dissolves tissue on the inner bone surface to increase the marrow cavity diameter  Absorption of old bone and deposition of new  Replaces about 10% of the skeletal tissue per year  Repairs microfractures, releases minerals into the blood, and reshapes bones in response to use and disuse  Osteoclasts removes matrix and get rid of unnecessary mass  Osteoblasts deposit new osseous tissue and thicken the bone  Bones give evidence of a person’s sex, race, height, weight, exercise habits, nutritional status, and medical history  Remodeling of bone depends on a precise balance between deposition and resorption, between osteoblasts and osteoclasts  Mineral deposition  Calcium and phosphate are allowed to reach their solubility product  Precipitate in the matrix  Ectopic ossification  Abnormal calcification of soft tissue (lungs, brain, eye, muscles, arteries  Mineral resorption  HCl secreted by osteoclasts  Acid phosphatase enzyme  Digest collagen  Hypocalcemia  Leads to excessive excitability of nervous system  Muscle tremors, spasms (inability of the muscle to relax)  Hypercalcimia  Leads to depression of nervous system, muscle weakness, sluggish reflexes and sometimes cardiac arrest  Regulated by three hormones  Calcitonin  Secreted by parafollicular cells in thyroid  Promote deposition of calcium in the bone  Decreases calcium level in blood  Inhibit osteoclasts, promote osteoblast activity (particularly in pregnant women)  Parathyroid hormone  Secreted by parathyroid glands  Promotes bone resorption  Increases calcium level in blood  Raise osteoclast population  Promotes calcium reabsorption in kidneys  Promotes calcitriol synthesis  Calcitriol  Increases calcium level in blood  Promotes more calcium absorption by intestine  Promotes reapsorption from skeleton  Osteoporosis  Sever loss of bone density  Osteoclast more active than osteoblasts  Osteosarcoma  Most common and deadly form of bone cancer  Metastasizes quickly  Osteogenesis imperfecta  Brittle bones  Defect in collagen deposition (genetic disorder)  Long bones of the limbs stop growing in childhood,  Growth of other bones is unaffected  A person has a short stature but a normal-sized head and trunk  Failure of the chondrocytes in the metaphysis to multiply and enlarge  Spontaneous mutation that can arise any time DNA is replicated