Skeletal System: Day Two Long Bone Anatomy, Microscopic Anatomy, Bone Composition, and Joint Anatomy

Structure of Long Bone – Gross Anatomy Diaphysis (shaft) Epiphyses Epiphyseal Line Medullary Cavity Bone Markings

Long Bone Diaphysis Shaft Makes up most of the bones length Composed of compact bone Covered and protected by a connective tissue membrane, the periosteum Sharpey’s fibers secure the periosteum to the bone

Long Bone Epiphyses Ends of long bone Thin layer of compact enclosing an area filled with spongy bone Articular cartilage instead of periosteum, covers its external surface a glassy hyaline cartilage Provides a smooth, slippery surface that decreases friction at joint surfaces

Long Bone Epiphyseal Line Thin line of bony tissue spanning the epiphysis that looks different from the rest of the bone in that area Remnant (what’s left …) of the epiphyseal plate seen in young growing bone. Epiphyseal plates cause the length wise growth of a long bone.

Long Bone Medullary Cavity In adults, the cavity is primarily for storage of adipose tissue (yellow marrow) In infants, the cavity is used to form blood cells (red marrow) In adults, red marrow is in the cavities of spongy bone located in the flat bone and the epiphysis (ends) of long bone ONLY.

Long Bone Bone Markings Reveal were muscles, tendons, and ligaments were attached and where blood vessels and nerves passed Two categories: Projections – grow out from bone Depressions – indentations in the bone

Structure of Long Bone – Microscopic Anatomy Osteocytes Lacunae Lamellae Central canals Osteon Canaliculi Volkmann’s canals CENTRAL CANAL VOLKMAN N’S CANAL

Microscopic Anatomy of Long Bones Osteocytes – mature bone cells Found in lacunae (spaces) Arranged in circles called lamellae Lamellae circle around the Central Canal

Microscopic Anatomy Osteon Osteon Central canal plus the lamellae Central Canal runs lengthwise through bone carrying blood vessels and nerves to all parts of the bone. Canaliculi Tiny canals that extend out from the central canal to the lacunae. Form a transportation system that connects all osteocytes (bone cells) to the nutrient supply Volkmann’s canals Communicate from outside of bone to the central canal Run at right angles

CENTRAL CANAL VOLKMANN’S CANAL

Bone Composition Calcium Salts give bone its hardness Organic parts (collagen) give bone flexibility and tensile strength