3. Classification of Bones
Long bones
Typically longer than wide
Have a shaft with heads at both ends
Contain mostly compact bone
Examples:
Femur (thigh bone),
humerus (arm bone),
all the bones of the limbs (except
wrist and ankle)
4. Classification of Bones
Short bones
Generally cube-shape
Contain mostly spongy bone
Examples: Carpals (wrist), tarsals (ankle)
5. Classification of Bones
Flat bones
Thin layers of compact bone
around a layer of spongy bone
Usually curved
Examples: Skull, ribs,
sternum (breastbone),
scapula (shoulder blade)
6. Classification of Bones
Irregular bones
Irregular shape
Do not fit into other bone
classification categories
Example: Vertebrae, hip,
auditory ossicles
7. Classification of Bones
Sesamoid (round) bones
Small and nodular
Embedded within tendons adjacent
to joints
Example: kneecap (patella)
8. Parts of a Long Bone
Diaphysis = shaft
Consists of a central medullary cavity filled
with marrow
Surrounded by a thick collar of compact
bone
Epiphyses = expanded ends
1-proximal & 1-distal
Consists mainly of spongy bone
Surrounded by thin layer of compact bone
Epiphyseal plate =
area of hyaline (articular) cartilage causing
lengthwise growth of a long bone at
junction of epiphyses and diaphysis
Epiphyseal line =
remnant of epiphyseal plate
10. Bone Structure – Gross Anatomy
Periosteum
= Tough, outer dense white fibrous connective tissue protective covering
of the diaphysis
Richly supplied with blood vessels, nerves
Serves as an osteogenic layer contains osteoblasts & osteoclasts,
cells that form and repair bone tissue
Serves as an insertion for tendons and ligaments
Endosteum
= Thin, inner lining of the medullary cavity
Contains osteoblast & osteoclast cells
Medullary cavity
= Hollowed central region
Houses marrow
11. Bone Structure – Gross Anatomy
Articular cartilage
= Pad of hyaline cartilage covering the external
surface of the epiphyses
Decreases surface friction
Osteoarthritis – thinning of articular cartilage
Sharpey’s fibers
= Secures periosteum to underlying bone
Nutrient arteries
Supply bone cells with nutrients
Enter bone thru nutrient foramen
in compact bone
13. Hyaline Cartilage Connective Tissue
D:
Most common cartilage
Avascular = no healing
Composed of:
Chondrocytes (in lacunae)
Abundant collagen fibers
Amorphous rubbery matrix
L:
Found at ends of bones, in joints, soft
part of nose, larynx, rings of cartilage
in trachea, costal cartilage
Entire embryonic skeleton is hyaline
cartilage
F:
Support
14. Microscopic Structure - Tissue
Bones are classified according to their types (2)
Compact bone
homogeneous, mainly in long bones
continuous extracellular matrix w/o space
dense, concentric circles of osseous tissue
site of red blood cell formation in children
Spongy bone
heterogeneous, mainly in short bones
small needle-like pieces of bone
many open spaces
site of red blood cell formation in adults
lightens bone
15. Histology of Compact Bone – Micro Anatomy
Osteon (Haversian System)
Structural unit of bone
Elongated cylinders cemented together
to form the long axis of bone
Components of an osteon:
Osteocytes – spider shaped bone cells
Lacunae – chambers/cavities containing
osteocytes
Lamellae – concentric matrix of collagen and
calcium salts
Central canal (Haversian canal) – center of
osteon containing blood vessels and nerves
Communicating canals within compact bone
Canaliculi – connect the lacunae together
Volkman canals (Perforating canals) – connect
blood vessels and nerve supply of adjacent
central canals together
Perpendicular to the central canal
17. Consist of poorly organized trabeculae
Trabeculae are small needle-like pieces of bone
Open space exists between trabeculae
Nourished by diffusion from nearby central canals
Histology of Spongy Bone – Micro Anatomy
18. Histology of Bone
Organic component (35%) – CELLS
Osteoprogenitor cells: -- Derived from mesenchyme (a loosely organized,
mainly mesodermal embryonic tissue that develops into connective and skeletal tissues, including blood and
lymph); Can undergo mitosis and become osteoblasts
Osteoblasts -- Form bone matrix by secreting collagen; Cannot
undergo mitosis BUILDERS!!!
Osteocytes -- Mature bone cells derived from osteoblasts; Principle
bone cell; Cannot undergo mitosis; Maintain daily cellular activities
Osteoclasts -- Function in bone reabsorption (destroy and clear
away bone matrix; Important in development, growth, maintenance
and repair of bone
Osteoid -- Primarily collagen, which give bone its tensile strength and
flexibility
Inorganic component (65%) – MINERAL SALTS
Hydroxyapatite, which is primarily calcium phosphate, gives bone its
hardness and compression strength
19.
20. Functions of Bone Tissue
Support of the body tissues
Legs & pelvis support body’s weight
Atlas supports the skull
Protection of underlying organs
Skull – protects the brain, eyes, ears
Rib cage & shoulder girdle – protects heart and lungs
Pelvic girdle – protects lower abdominal organs and internal
reproductive organs
Movement
Skeletal muscles attached to bones by tendons serve to move bones
Muscles use bones to work in opposition to cause movement
21. Functions of Bone Tissue
Mineral Homeostasis
Bones store many minerals including:
Calcium salts, mainly calcium phosphate
Magnesium, sodium, potassium, carbonate ions
Harmful minerals stored:
Lead, radium, strontium
Energy storage
Yellow marrow in the shaft of long bones
Serves as an important chemical energy storage (fat)
Can convert back to red marrow if blood cells are needed and revert
back to yellow marrow when there is a blood cell surplus
22. Functions of Bone Tissue
Hematopoiesis
Blood cell formation
All blood cells are formed in the red marrow of certain bones
Children: mostly in medullary cavities of long bones
Adults: spongy bones of skull, ribs, sternum, clavicles, vertebrae,
hip bones
24. 1. What is the process of red blood cell formation?
• hematopoiesis
2. What is the type of cell the undergoes mitosis and creates
osteoblasts?
• Osteoprogenitor
3. What type of marrow produces blood cells?
• red marrow
4. Where is the marrow found in children? Adults?
Medullary cavity; spongy bone
5. What are the two types of bone?
• Spongy; compact
6. What are the four shapes of bone? And give an example of each.
• Short carpals, tarsals, patella
• Long humerus, femur, radius, ulna, tibia, fibula, metacarpals,
metatarsals, phalanges
• Flat ribs, sternum, cranial and facial bones
• Irregular hip bones, vertebra
7. What is the inorganic compound that makes up bone? What does
this provide the bone with?
• Hydroxyapatite; compression strength
