Skeletal System: Day TwoLong 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 BoneDiaphysis

ShaftMakes up most of the bones length Composed of compact boneCovered and protected by a connective tissue membrane, the periosteumSharpey’s fibers secure the periosteum to the bone

Long BoneEpiphyses

Ends of long boneThin layer of compact enclosing an area filled with spongy boneArticular cartilage

instead of periosteum, covers its external surfacea glassy hyaline cartilage Provides a smooth, slippery surface that decreases friction at joint surfaces

Long BoneEpiphyseal Line

Thin line of bony tissue spanning the epiphysis that looks different from the rest of the bone in that areaRemnant (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 CavityIn 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 MarkingsReveal 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

CENTRAL CANAL

VOLKMANN’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 AnatomyOsteon

OsteonCentral canal plus the lamellae

Central Canal runs lengthwise through bone carrying blood vessels and nerves to all parts of the bone.

CanaliculiTiny 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 canalsCommunicate from outside of bone to the central canalRun at right angles

CENTRAL CANAL

CENTRAL CANAL

VOLKMANN’S CANAL

Bone Composition

Calcium Salts give bone its hardness

Organic parts (collagen) give bone flexibility and tensile strength