Anatomy & Physiology

Anatomy & Physiology Study Guide

©2018 Achieve Page 82 7.9 Chapter Seven Review The skeletal system has five primary functions: • Skeletal elements have a variety of purposes, such as providing a framework for body posture and allowing for precise movements, as well as providing protection, mineral storage, and blood cell formation. An introduction to the skeletal system: • The skeletal system includes the bones of the skeleton and the cartilages, ligaments, and other connective tissues that stabilize or connect the bones. The functions of the skeletal system include support, storage of minerals and lipids, blood cell production, protection, and leverage. Bones are classified according to shape and structure, and feature surface markings: • Bones may be categorized as long bones, flat bones, sutural bones (Wormian bones), irregular bones, short bones, and sesamoid bones. • Each bone has characteristic bone markings, including elevations, projections, depressions, grooves, and tunnels. • The two types of bone tissue are compact (dense) bone and spongy (cancellous) bone. • A representative long bone has a diaphysis, epiphyses, metaphyses, articular cartilages, and a medullary cavity. • The medullary cavity and spaces within spongy bone contain either red bone marrow (for blood cell formation) or yellow bone marrow (for lipid storage). Bone is composed of matrix and several types of cells: osteocytes, osteoblasts, osteoprogenitor cells, and osteoclasts: • Osseous tissue is a supporting connective tissue with a solid matrix, which is ensheathed by a periosteum. • Bone matrix consists largely of crystals of hydroxyapatite; the minerals are deposited in lamellae. • Osteocytes, located in lacunae, are mature bone cells. Adjacent osteocytes are interconnected by canaliculi. Osteoblasts synthesize the bony matrix by osteogenesis. Osteoclasts dissolve the bony matrix through osteolysis. Osteoprogenitor cells differentiate into osteoblasts. Compact bone contains parallel osteons, and spongy bone contains trabeculae: • The basic functional unit of compact bone is the osteon, containing osteocytes arranged around a central canal. Perforating canals extend perpendicularly to the bone surface. • Compact bone is located where stresses come from a limited range of directions, such as along the diaphysis of long bones. • Spongy bone contains trabeculae, typically in an open network. • A bone is covered by a periosteum and lined with an endosteum. of 368