Bones and skeletal tissue

Appositional growth

Chondroblasts in perichondrium secrete matrix against surface of existing cartilage (top: adds to existing cartilage, increases thickness)

Interstital growth

Chondrocytes within lacunae divide & secrete new matrix, expanding cartilage from within (bottom to top, increases length)

Long bones

Humerus, radius, ulna, femur, tibia, metacarpals, metatarsals, phalanges, clavicle

Short bones

Cube shaped (carpals & tarsals)

• sesamoid bones form from within tendons

• patella

Flat bone

Thin, flat, slightly curved: Sternum, scapulae, ribs, ilium, some cranial bones (frontal, occipital, parietal, lacrimal)

Irregular bones

Vertebrae, ischium & pubis, ethmoid, sphenoid, temporal, zygomatic, mandible, maxilla, sacrum, coccyx, hyoid

Compact bone

dense outer layer on every bone that appears smooth and solid (straight part of femur)

Spongy bone

Made up of a honeycomb of small pieces of bone called trabeculae (top of femur)

Red or Yellow

Open spaces between trabeculae are filled with what color bone marrow?

Hematopoiesis

Occurs in red bone marrow, primary cite of new blood cell formation

Yellow bone marrow

Color is due to higher number of adipocytes, stores triglycerides, as adults most red marrow is converted to yellow.

Anemia

What causes yellow bone marrow to convert to red?

Diaphysis

tubular shaft that forms long axis of bone

• consists of compact bone surrounding central medullary cavity filled with yellow marrow in adults

Epiphyses

ends of long bones that consist of compact bone externally and spongy bone internally

• Articulate cartilage: covers articular (joint) surfaces

Epiphyseal line

between diaphysis and epiphysis, remnant of childhood __________ plate (disc) where bone growth occurs

Periosteum

double-layered membrane, covers external surfaces except joints

• Anchoring points for tendons & ligaments

• Primitive osteogenic stem cells

• many nerve fibers & blood vessels

• enter shaft through nutrient foramen opening

Endosteum

Covers internal bone surface, trabeculae of spongy bones

• Canals that pass through compact bone

• Delicate connective tissue membrane

• Osteogenic cells

Epiphyseal plate

maintains thickness, consists of 5 zones

• Resting

• Proliferation

• Hypertoncic

• Calcification

• Ossification

Growth hormone

most important hormone in stimulating epiphyseal plate activity in infancy and childhood

Thyroid hormone

modulated activity of growth hormone, ensuring proper proportions

Testosterone

end growth by inducing epiphyseal plate closure (promise adolescents growth spurts, estrogen for females)

Dwarfism

Under secretion of growth hormone

Gigantism

Over secretion of growth hormone

Complete

broken all the way through

Incomplete

not broken all the way through

Nondisplaced

position of bone after fracture: ends retain normal position

Displaced

position of bone after fracture: ends are out of alignment

Compound

skin is penetrated

Closed

skin is not penetrated

Bone composition

Hydroxyapatite’s (mineral salts) make up 65%, tiny calcium phosphate crystals in & around collagen fibers

Cells of bone tissue

• Osteogenic cells

• Osteoblasts

• Osteocytes

• Bone-lining cells

• Osteoclasts

Osteocytes

mature bone cells in lacunnae that no longer divide, maintains bone tissue, responds to mechanical stimuli such as increased force on bone

• communicate information to osteoclasts and osteoblasts so bone remodeling can occur

Osteoblast

forms bone matrix, secretes unmineralized bone matrix called osteoid (responsible for bone growth)

Osteogenic cell

mitotically active stem cells in periosteum and endosteum

• differentiate into osteoblasts or bone-lining cells

Osteoclast

derived from same stem cells that become macrophages, resorbs bone

• giant, multinucleate cells fungi in in bone resorption

• ruffled borders increase surface area

• located in depressions called resorption bays

Complete, displaced, simple

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Incomplete, nondisplaced, simple

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Complete, displaced, compound

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