6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven...

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Transcript of 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven...

Page 1: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.
Page 2: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.

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Bone cells› Osteoblasts› Osteocytes› Osteoclasts› Stem cells or osteochondral progenitor cells

Woven bone: collagen fibers randomly oriented

Lamellar bone: mature bone in sheets Cancellous bone: trabeculae Compact bone: dense

Page 3: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.

Bones are composed of connective tissue, chemicals, and fats

Solid outer layer - compact bone› Composed of

osteons An inner layer of

spongy bone › a honeycomb of flat,

needle-like projections called trabeculae.

Above: Note the relationship btwn the compact and spongy bone.

Below: Close up of spongy bone.

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Volkmann’s canals› Perpendicular to the

haversian canals. › Connect the blood and

nerve supply in the periosteum to those in the haversian canals and the medullary cavity.

Haversian canals › allow the passage of

blood vessels, lymphatic vessels, and nerve fibers.

› Surrounded by layers of bone called a lamella.

osteon

Page 5: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.
Page 6: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.

Osteoblasts› Bone building cells› Synthesize and secrete

collogen fibers and other organic components of the bone matrix

› Initiate calcification› Found in the periosteum

and the endosteum Ossification

› Formation of bone by osteoblasts.

› Cells surround themselves by matrix.

osteoblasts

Bone matrix

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Osteocytes. › Mature bone cells.

› Osteoblasts that have become trapped by the secretion of matrix.

› Responsible for maintaining the bone tissue

Lacunae› spaces occupied

by osteocyte cell body Canaliculi

› canals that allow for nutrient filled liquid to fill the lacunae

Page 8: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.

OsteoclastsCells that ecretes digestive enzymes to digest bone matrix

bone resorptionConcentrated in the endosteum.On the side of the cell that faces the bone surface,

ruffled border. Pumps out hydrogen ions

Create an acid environment that eats away at the matrix.

Page 9: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.

www.academic.pgcc.edu/~aimholtz/AandP/LectureNotes/ANP1_Lec/Skeletal/BoneTissue.ppt

Why is there a depression underneath the osteoclast?

What advantage might a ruffled border confer?

What is the name of the third cell type shown here?

What do you think the tan material represents?

Page 10: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.

Diaphysis - Shaft› Compact bone

Epiphysis - End of the bone› Cancellous bone

Epiphyseal plate - growth plate› Hyaline cartilage; present until

growth stops Epiphyseal line: bone stops

growing in length Medullary cavity: contains

marrow

› In children medullary cavity is red marrow,

› In adults marrow is yellow in limb bones and skull (except for epiphyses of long bones). • Red marrow is found in in

the cavities of the spongy bone of flat bones

Page 11: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.

Periosteum› Outer is fibrous

› Inner is single layer of bone cells including osteoblasts, osteoclasts and osteochondral progenitor cells

› connected to bone matrix via Sharpey’s fibers

Endosteum. › Similar to inner layer of

periosteum.

› Lines all internal spaces

Page 12: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.

•Osteocytes•Lamellae•Haversian canals•Osteon•Volkmann’s canals•Lacunae

•Diaphysis•Periosteum•Sharpy’s fibers•Epiphyses •Epiphyseal plate•Epiphyseal line•Yellow marrow•Medullary cavity•Sharpy’s fibers

Page 13: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.

Consists of organic and inorganic components.› Organic component are secreted by the osteoblasts:

Collagen fibers Elastin

› Inorganic component Calcium phosphate Calcium hydroxide magnesium, fluoride, & sodium.

Page 14: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.
Page 15: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.

What if the collagen and elastin were removed from this bone.

What if the Calcium phosphate, Calcium hydroxide and the other minerals were removed from this bone?

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Page 17: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.

Figure 5.2

Page 18: 6-2 Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone : collagen fibers randomly oriented Lamellar.
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Prenatal: cartilage model

Fetus: some conversion to bone

Childhood: primary and secondary ossification sites formed

Adolescence: cartilage growth plate elongates

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Changes in shape, size, strength:› Dependent on diet, exercise, age

Bone cells regulated by hormones:› Parathyroid hormone (PTH): removes calcium

from bone› Calcitonin: adds calcium to bone

Repair: hematoma and callus formation

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Protection: encases most internal organs

Support: allows body positions

Permit movement: muscle attachments for movement

Mineral reservoir: calcium, phosphorus

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Classified by degree of movement:› Fibrous joint: immovable (e.g., fontanels)› Cartilagenous joint: slightly movable, cartilage

connection (e.g., backbone)› Synovial joint: freely movable

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Figure 5.12a

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Joint capsule: synovial membrane + hyaline cartilage

Synovial membrane secretes synovial fluid as lubricant

Hyaline cartilage cushions

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Sprains: stretched or torn ligaments

Bursitis and tendinitis: inflammations

Arthritis: inflammation of joints