Bone & joints
General
Anatomy-bone
Author: Dariusz Borys, M.D.
Last author update: 1 January 2012
Last staff update: 30 April 2021
Copyright: 2003-2023, PathologyOutlines.com, Inc.
PubMed Search: Bone [title] Normal anatomy
Cite this page: Borys D. Anatomy-bone. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/bonenormalanatomy.html. Accessed April 1st, 2023.
Definition / general
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Basic function of bone:
- Bone is the basic unit of the skeletal system and provides shape and support for the body, as well as protection for some organs
- There are 206 bones in the human skeleton: 80 axial skeletal bones (e.g. skull, vertebral column and sacrum) and 120 appendicular skeletal bones (e.g. bones of extremities, scapula, pelvis)
Gross structure of bone
- Epiphysis – region between the growth plate or growth plate scar and the extended end of bone, covered by articular cartilage
- Metaphysis – region between the growth plate and diaphysis; contains abundant trabecular bone, but the cortical bone thins here comparing to diaphysis
- Diaphysis or shaft – region between metaphyses, composed mainly of compact cortical bone
- Physis (epiphyseal plate, growth plate) – region of bone that separates the epiphysis from metaphysis
- Zone of endochondral ossification in actively growing bone or the epiphyseal scar in a full grown bone
- Cross section: periosteum, cortex (composed of cortical bone or compact bone), medullary space (composed of cancellous or spongy bone)
- Bone composition: 35% organic (cells, proteins), 65% calcium hydroxyapatite (contains 99% of body's calcium, 85% of phosphorus, 65% of sodium, also magnesium)
- Hydroxyapatite crystal is formed via phase transition; 12 day lag between matrix deposition and mineralization
- Collagen resists tension, hydroxyapatite and proteoglycans in cartilage resist compression
- Thicker cortex in middle of long bones resists bending; cancellous bone at ends of long bones resists compression
Classification
- Bones are divided on the basis of their location, shape, size and structure
Based on location, bones can be classified as:
- Axial skeleton – bones of the skull, scapula, vertebral column
- Appendicular skeleton – bones of the pectoral girdle, pelvis and limbs
Based on shape, bones can be classified as:
- Flat bone – bones of the skull, sternum, pelvis and ribs
- Tubular bone – long tubular bones are bones of the extremities (e.g. femur, humerus); short tubular bones are bones of hands and feet
- Irregular bone – bones of the face and vertebrae
- Sesamoid bones – patella
Based on size, bones can be classified as:
- Long bone – tubular bones of extremities (e.g. femur, humerus)
- Short bone – cuboidal in shape, in the foot (tarsal bones) and wrist (carpal bones)
Blood supply
Long bones:
Large irregular bones, short bones and flat bones:
Venous and lymphatic drainage:
Nerve supply of bone:
- The blood supply of bone varies with different types of bone, but vascular supply is especially rich in bones rich in red bone marrow
Long bones:
- Diaphyseal nutrient artery – most important arterial supply, passes obliquely through cortical bone
- Metaphyseal and epiphyseal arteries – numerous small arteries supply the ends of bones; these blood vessels arise from arteries that supply adjacent joints, anastomose with the diaphyseal capillaries and terminate in bone marrow
- Periosteal arterioles - these vessels supply the outer layers of cortical bone
Large irregular bones, short bones and flat bones:
- These bones are supplied by superficial periosteal arterioles
Venous and lymphatic drainage:
- Blood is drained from the bone via venous and lymphatic vessels that accompany arteries and frequently leave through foramina near the articular end of the bones
Nerve supply of bone:
- Nerves are most rich in articular extremities of long bones, vertebrae and larger flat bones
- Nerves accompany the blood vessels to the interior of the bone and to the perivascular spaces of the haversian canals
- The periosteal nerves are sensory, causing periosteum to be particularly sensitive to tearing or tension
Bone tissue types and structure
Based on texture, bone can be classified as:
Based on matrix arrangement bone can be classified as:
- Bone tissue can be classified based on texture, matrix arrangement; also maturity and developmental origin (see Histology topic)
Based on texture, bone can be classified as:
- Compact bone (dense bone, cortical bone) – dense bone that surrounds trabecular bone in the center, contains Haversian system and secondary osteons
- Sponge bone (trabecular bone, cancellous bone) – sponge-like with numerous cavities, located in the center of bone cavity, consists of connected bony trabeculae
Based on matrix arrangement bone can be classified as:
- Lamellar bone – mature bone with collagen fibers arranged in lamellae
- Lamellae of sponge bone are arranged parallel to each other
- In contrast, lamellae of compact bone are organized concentrically to around vascular canal (haversian canal)
- Woven bone – immature bone; collagen fibers in woven bone are arranged in irregular random arrays and contain smaller amounts of mineral substance and a higher proportion of osteocytes to lamellar component
- Woven bone is eventually converted to lamellar bone
Diagrams / tables
Images hosted on other servers:
Femur
Humerus
Patella
Pelvis: left-male, right-female
Radius and ulna
Tibia and fibula
