CHP7 Bone Tissue

4 process achondroplastic dwarfism achondroplastic

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: owth & remodeling (cont.) Bone Bone grows by 2 methods~ interstitial & appositional growth Interstitial= @ epiphyseal plate, matrix is added to extend epiphyseal length of bone length Appositional= matrix added to external surface to increase matrix width width • Osteoblasts deposit matrix in layers parallel to outer surface Osteoblasts & osteoclasts dissolve bone on inner surface to enlarge marrow cavity marrow • Osteitis deformans & other bone deformities result if one process outpaces the other (Table 7.4) process Achondroplastic dwarfism Achondroplastic Achondroplastic dwarfism= short stature but normal-sized short head and trunk head • Long bones of the limbs stop growing in childhood due to Long failure of chondrocytes (zones 2-3) to multiply & enlarge failure • Condition occurs if spontaneous mutation of allele during Condition DNA replication DNA • Mutant allele is dominant so kids of heterozygous a.d. are Mutant 50:50 50:50 Pituitary dwarfism= deficiency of growth hormone…stunts deficiency growth of all bones (short stature w/ normal proportions) all Bone Physiology Bone Physiology of osseous tissue~ bone is a metabolically active organ that influences entire body by regulating minerals minerals • Mineral deposition; mineral resorption; & homeostasis of Mineral Ca2+ & PO43Ca • 2 iimportant ions required for many compounds (ATP, DNA) & mportant body functions (pH balance, communication, contraction, clotting) Mineralization= crystallization process Mineralization crystallization • Ca2+, PO43- & other ions are removed from blood plasma & deposited in bone tissue deposited Mineral deposition Mineral Steps of the mineralization process~ • Osteoblasts produce collagen fibers that spiral along the Osteoblasts length of osteon in alternating directions length • Fibers become ‘encrusted’ w/ minerals & harden matrix • Crystals forms only when [ion] reaches a critical value (= Crystals solubility product) solubility • Most tissues have inhibitors to prevent calcification, but Most osteoblasts are able to block them to produce salts of matrix osteoblasts • ‘Seed crystals’ serve as positive feedback signals to form Seed positive more crystals since they attract more ions from solution to crystalize crystalize Ectopic ossification= abnormal calcification Ectopic • May occur in lungs, brain, eyes, muscles, tendons (= May calculus in soft...
View Full Document

Ask a homework question - tutors are online