Osseous Tissue (Bone Tissue). Classification of Bone by Tissue Type Two basic types of Tissue 1....

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Osseous Tissue (Bone Tissue)

Transcript of Osseous Tissue (Bone Tissue). Classification of Bone by Tissue Type Two basic types of Tissue 1....

Osseous Tissue (Bone Tissue)

Classification of Bone by Tissue Type

• Two basic types of Tissue1. Compact bone

• Homogeneous• Looks “smooth”

2. Spongy bone• Small needle-like

pieces of bone• Many open spaces

(like sponge)• Keep bones light

Figure 5.2b

Review:

• Bone is a type of connective tissue2 Parts:

1. Cells (living)

2. Matrix (nonliving substance released by cells)

A. FiberB. Ground Substance

1. Cells• Osteocytes— mature bone cells• Osteoblasts— bone-forming cells (germ cells or “bud” cells)• Osteoclasts —bone-destroying cells (“breakers”)

A. primarily collagen fibersflexibility tensile strength (the strength to endure stretching

forces) B. calcium salts (hardness)

contain calcium and phosphorus great compressional strength (the strength to endure

squeezing forces)

2. Matrix

Bone Remodeling

constant balance of bone deposit and removal that occurs throughout your life

bone deposit occurs at a greater rate when bone is injured

bone resorption allows calcium of degraded bone matrix to move into the blood. About 10% of bone is

replaced every year in an adult skeleton

boneformation

bonereabsorption

osteoblasts osteoclasts

Maintenance of Bone

Control of Remodeling

Hormonal                                                       

–  Rising blood Ca2+ levels trigger the thyroid to release calcitonin 

–  Calcitonin stimulates calcium salt deposit in bone 

–  Falling blood Ca2+ levels signal the parathyroid glands to release Parathyroid hormone (PTH) 

–  PTH signals osteoclasts to degrade bone matrix and release Ca2+ into the blood 

boneformation

bonereabsorption

osteoblasts osteoclastsCalcitonin (CT)

from thyroidParathyroidhormone (PTH)

from parathyroid

Hormonal effects

bone

formation

bone

reabsorption

osteoblasts osteoclasts

Before age 25

Increase bone mass

boneformation

bonereabsorption

osteoblasts osteoclasts

Age 25-50

boneformation

bonereabsorption

osteoblasts osteoclasts

Age 50-on

Decrease bone mass

bone

formation

bone

reabsorption

osteoblasts osteoclasts

Stress effects

Stress increases bone density

http://www.youtube.com/watch?v=yFJ4iswRiu4&feature=related