Structure of Bone Gross Anatomy of a Long

Structure of Bone Gross Anatomy of a Long Bone Microscopic Anatomy Bone Markings Pages 137 -140

Anatomy of a Long Bone � Three major sections: ◦ Diaphysis ◦ Proximal Epiphysis ◦ Distal Epiphysis

Anatomy of a Long Bone �Diaphysis (a. k. a. shaft) ◦ most of bone’s length ◦ Composed of compact bone �Periosteum ◦ ◦ Covers the outside of the diaphysis Fibrous connective tissue membrane Provides insertion site for tendons & ligaments Perforating (Sharpey’s) fibers secure periosteum to underlying bone �These are made up of thick bundles of collagen © 2015 Pearson Education, Inc.

Figure 5. 3 a The structure of a long bone (humerus of arm). Articular cartilage Proximal epiphysis Diaphysis (a) Distal epiphysis Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined by endosteum)

Figure 5. 3 c The structure of a long bone (humerus of arm). Endosteum Yellow bone marrow Compact bone Periosteum Perforating (Sharpey’s) fibers Nutrient arteries (c)

Anatomy of a Long Bone �Epiphysis ◦ Ends of the bone ◦ Composed mostly of spongy bone enclosed by thin layer of compact bone ◦ Line vs. plate depends on age �Articular cartilage ◦ Covers the external surface of the epiphyses ◦ Made of hyaline cartilage ◦ Decreases friction at joint surfaces © 2015 Pearson Education, Inc.

Figure 5. 3 b The structure of a long bone (humerus of arm). Articular cartilage Spongy bone (b) Compact bone

Anatomy of a Long Bone � Epiphyseal plate ◦ Flat plate of hyaline cartilage seen in young, growing bone ◦ Causes lengthwise growth of a long bone �Think of a divergent plate boundary � Epiphyseal line ◦ Remnant of the epiphyseal plate ◦ Seen in adult bones © 2015 Pearson Education, Inc.

Figure 5. 3 a The structure of a long bone (humerus of arm). Articular cartilage Proximal epiphysis Diaphysis (a) Distal epiphysis Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined by endosteum)

Anatomy of a Long Bone � Marrow (medullary) cavity ◦ Cavity inside the shaft ◦ Contains: �yellow marrow (mostly fat) in adults �red marrow for blood cell formation in infants ◦ Lined by the endosteum (thin connective tissue) �In adults, red marrow is situated in cavities of spongy bone ◦ In flat bones ◦ In epiphyses of some long bones © 2015 Pearson Education, Inc.

Figure 5. 3 a The structure of a long bone (humerus of arm). Articular cartilage Proximal epiphysis Diaphysis (a) Distal epiphysis Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined by endosteum)

Bone Markings �Surface features of bones ◦ Attachments sites for muscles, tendons, and ligaments ◦ Passages for nerves and blood vessels � Categories of bone markings ◦ Projections or processes ◦ Depressions or cavities © 2015 Pearson Education, Inc.

Table 5. 1 Bone Markings (1 of 3).

Table 5. 1 Bone Markings (2 of 3).

Table 5. 1 Bone Markings (3 of 3).

Microscopic Anatomy of Compact Bone � Osteocytes (mature bone cells) ◦ situated within cavities known as lacunae � Lacunae ◦ arranged in concentric rings called lamellae � Lamellae ◦ rings situated around the central (Haversian) canal © 2015 Pearson Education, Inc.

Figure 5. 4 b Microscopic structure of compact bone. Lamella Osteocyte (b) Canaliculus Lacuna Central (Haversian) canal

Microscopic Anatomy of Bone � Central (Haversian) canal � Osteon (Haversian system) ◦ Opening in the center of an osteon ◦ Runs lengthwise through bone ◦ Carries blood vessels and nerves ◦ A unit of bone containing central canal and matrix rings © 2015 Pearson Education, Inc.

Figure 5. 4 a Microscopic structure of compact bone. Spongy bone Osteon (Haversian system) Lamellae Perforating (Volkmann’s) canal Blood vessel continues into medullary cavity containing marrow Blood vessel Compact bone Central (Haversian) canal Perforating (Sharpey’s) fibers Periosteum Periosteal blood vessel (a)

Figure 5. 4 c Microscopic structure of compact bone. Osteon Interstitial lamellae Lacuna Central (Haversian) canal (c)

Haversian System summary � From � 1. � 2. � 3. � 4. � 5. smallest to largest structure: Osteocyte Lacunae Lamellae Central (Haversian) canal Osteon (Haversian system)

Microscopic Anatomy of Bone � Canaliculi ◦ Tiny canals that radiate from the central (Haversian) canal to the lacunae ◦ a transport system that connects all bone cells to a nutrient supply � Perforating (Volkmann’s) canal ◦ Canal perpendicular to the central canal ◦ Carries blood vessels and nerves © 2015 Pearson Education, Inc.

Figure 5. 4 b Microscopic structure of compact bone. Lamella Osteocyte (b) Canaliculus Lacuna Central (Haversian) canal

Chemical Composition of Bone � Organic flexible parts of the matrix make bone ◦ Cells, fibers (collagen), ground substance � salts of calcium phosphate deposited in the extracellular matrix make bone hard © 2015 Pearson Education, Inc.