126 Anatomy & Physiology Essentials Copyright Goodheart-Willcox Co., Inc. Haversian system. Within the system, there are tiny sideways canals called canaliculi (kan-a-LIK-yoo-ligh). The canaliculi connect with the lacunae, forming a comprehensive transportation matrix for the supply of nutrients and removal of waste products throughout the Haversian system. The multiple Haversian systems are joined by perforating (Volkmann’s) canals, also running sideways. course through these tiny tunnels (Figure 5.7). Major passageways running in a lengthwise direction through the bone are called Haversian canals. Tiny cavities called lacunae (la-KOO-nee) are laid out in concentric circles called lamellae (la-MEHL-ee) around the Haversian canals. Osteocytes are housed in the lacunae, which act as protective islands for these cells. Each Haversian canal, with its surrounding layers of lacunae, forms a structural unit called an osteon, or Periosteum Periosteum C Diaphysis A Humerus B Cortical and trabecular bone Epiphysis Diaphysis Nutrient arteries Cortical bone Cortical bone Epiphysis Articular cartilage Articular cartilage Articular cartilage Endosteum Endosteum Blood vessel Yellow bone marrow Yellow bone marrow (in medullary cavity) Medullary canal Cortical bone Trabecular bone Red marrow cavities Trabecular bone © Body Scientific International Figure 5.6 The anatomical structure of a long bone. A—Anterior view of the humerus with the interior of the top half exposed. B—Cortical and trabecular bone of the epiphysis. C—Enlargement of the diaphysis.