CHS 06-07 BONES AND SKELETAL TISSUES This chapter provides a review of bone and skeletal tissue. The human skeleton is composed primarily of two connective tissues: (1) cartilage and (2) bone. CHARACTERISTICS OF CARTILAGE There are no blood vessels or nerves extending into the matrix of cartilage. An epithelial membrane (the perichondrium) surrounds the cartilage and provides surface protection as well as attachment points for BV and nerves. Cells called chondrocytes are associated with the perichondrium and extend into the matrix. There are three types of cartilage associated with the skeletal system: Elastic Cartilage Fibrous Cartilage Hyaline Cartilage There are two patterns of cartilage growth: Appositional Growth Interstitial Growth CHARACTERISTICS AND CLASSIFICATION OF BONE Classification of bones can be done according to shape by placing bones into one of four or six shape categories: Long Bones Short Bones Sesamoid bones can be classified in this group. Flat Bones Irregular Bones Wormian bones can be classified in this group. Sesamoid Bones Wormian Bones Sutural Bones 34
BONE STRUCTURE Types of Bone Compact Cancellous Spongy Bone Bone Structures Periosteum Sharpey s Fibers Nutrient Foramen Diaphysis Epiphysis Epiphyseal Plate Epiphyseal Line Medullary Cavity Yellow Marrow Red Marrow Endosteum Types of Bone Cells Osteoblasts Osteocytes Osteoclasts Microscopic Structure Osteon Central Canal Perforating Canal Haversian Canal (Transverse; Volkmann s) Lamellae 35
Lacuna Canaliculi BONE MARKINGS See the bone marking table in your laboratory manual to review bone markings. There is also a copy of the table in your text will provide the same information. Observe that there are two categories of bone markings: projections or processes, all of which grow out of the bone surface and depressions or cavities, which are indentations of the bone. Trick: all terms beginning with T are projections and all terms beginning with F (except facet) are depressions. OSTEOGENESIS: THE PROCESS OF BONE DEVELOPMENT Intramembranous Ossification Osteoprogenitor Cells Endochondral Ossification BONE HOMEOSTASIS Bone chemistry must be continually shuffled to maintain balance. Some regions of bone are constantly replaced (ex: distal femur every four months). Others (ex: shaft of femur) are not changed within a lifetime. Bone requires specific minerals and vitamins: calcium, phosphate, potassium, carbonate, sodium, magnesium, vitamin D, vitamin C, vitamin A and vitamin B 12. Hormones regulate bone homeostasis just as they regulate all other cellular and systemic functions. The major hormones involved in maintenance of bone integrity include: Calcitonin Calcitriol Human Growth Hormone HGH Insulin Parathyroid Hormone Sex Hormones PTH Estrogens and Testosterones Thyroid Hormones T 3 and T 4 36
BONE REMODELING When an injury occurs, homeostasis is disrupted and must be re-established (ex: fractures - any break in a bone). Steps in re-modeling include: Fracture hematoma forms. Death of bone cells at injury site. Swelling, inflammation, phagocytic infiltration. Blood vessel infiltration. Procallus forms. Fibroblasts and osteoprogenitor cells invade. Formation of fibrocartilage begins. Bony callus forms from fibrocartilage. Remodeling occurs. Compact bone replaces spongy bone and the periphery of the fracture. BONE FACTS/FUNCTIONS CHAPTER 7 MATERIAL These functions/responsibilities of specific bones are considered important for you to remember: Cheekbone Structure Costal Facets Cribriform Plates Crista Galli Hyoid Bone Intervertebral Discs Pelvis Female Male Ribs 37
True False Floating Sella Turcica Transverse Foramen 38
DISORDERS/DISEASES FRACTURES Fractures are treated by closed (hands on) repair or by open reduction (surgery with pins and everything!) Closed A/k/a simple. No break through the skin. Colles Distal end of the radius. Pronounced Koll-ease. Comminuted Splinters at the site of the impact. Common in aged persons. Complete Clean break all the way. Compression Crushed bones, as in osteoporosis. Depression Skull fracture. Greenstick One side breaks other bends (in kids). Open Compound: goes through the skin. Partial Incomplete break across the bone. Pott s Distal end of the fibula. Spiral Twisted apart. A ragged break. Common sports injury. Stress Microscopic from repeated impact. Osteoarthritis DISEASES Deterioration of intervertebral discs, etc. Osteogenesis Imperfecta Osteomalacia/Rickets Osteomyelitis Brittle Bone Disease ("Lobstein syndrome ). Weak, easily broken bones due to errors in Type-I collagen production. Wormian bones are a marker for various diseases and are important in the primary diagnosis of Brittle Bone Disease. Group of disorders in which bones are soft due to lack of mineral content, such as insufficient calcium or vitamin D. Called rickets when seen in children. Inflammation of bone caused by bacteria that enter via a wound. Osteoporosis Loss of bone mass. Osteosarcoma Paget s Disease Bone cancer in a long bone of a limb. An aggressive cancer that tends to metastasize to the lung. Uncoordinated osteoclast activity causing irregular thickening of bone. 39