The skeletal system osseous tissue and skeletal structure
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Chapter 6: Bones Skeletal Tissues. The Skeletal System: Osseous Tissue and Skeletal Structure. Introduction - components. The Bones - about 206 Bone tissue , or osseous tissue, is the major component of the skeletal system. Bones are dynamic organs made up of several tissues types.

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The skeletal system osseous tissue and skeletal structure

Chapter 6: Bones Skeletal Tissues

The Skeletal System:Osseous Tissue and Skeletal Structure


Introduction components
Introduction - components

  • The Bones - about 206

    • Bone tissue, or osseous tissue, is the major component of the skeletal system.

      • Bones are dynamic organs made up of several tissues types.


Introduction functions
Introduction - Functions

  • The skeletal system has a variety of functions:

    • Support: bones are the body’s infrastructure

    • Storage of minerals: calcium salts; 98% of the body’s calcium is in the bones and adipose

    • Hematopoiesis: the bone marrow produces new blood cells

    • Protection: many delicate organs are surrounded by bone

    • Leverage: muscles pull on bone to produce movement  


Structure of bone
Structure of Bone

  • Bones:

    • Support connective tissues:

      • Cells

      • Solid matrix containing calcium salts

        • hydroxyapaptite

    • Outer covering called periosteum:

      • Continuous with the deep fascia

    • Inner cellular lining is called the endosteum.


The histological organization of mature bone
The Histological Organization of Mature Bone

  • The matrix:

    • 2/3 of bone weight is calcium phosphate:

      • Hydroxyapatite crystals:

        • Very resistant to compression

  • Collagen fibers:

    • 1/3 of the bone matrix:

      • Very resistant to stretch

  • Collagen and hydroxyapatite make bone tissue extremely strong.

  • Cells account for about 2–3% of bone tissue.


Cells of mature bone
Cells of Mature Bone

  • Osteocytes = mature cells:

    • Maintain bone tissue

  • Osteoblasts immature, active cells:

    • Found on inner and outer surfaces of a bone.

    • Osteoblasts produce osteoid.

    • The process of making new bone is called osteogenesis.

  • Osteoprogenitor cells:

    • Found on inner and outer surfaces of a bone.

    • Divide and differentiate to form new osteoblasts.

  • Osteoclasts are giant multinucleated cells:

    • Perform osteolysis



Cells of mature bone1
Cells of Mature Bone

Figure 5.1 Structure of a Typical Bone


Compact and spongy bone histology
Compact and Spongy Bone - Histology

Figure 5.2b,d The Internal Organization of Representative Bones



Functional Differences between Compact and Spongy Bone

  • Epiphyses, or ends

  • The diaphysis, or shaft

  • The metaphysis:

    • Connecting region between the epiphyses and diaphysis

Figure 5.3a Anatomy of a Representative Bone


The periosteum and endosteum
The Periosteum and Endosteum

Figure 5.4 The Periosteum and Endosteum


Bone development and growth
Bone Development and Growth

  • Before six weeks of development the skeleton is cartilage.

  • Osteogenesis is bone formation.

    • Ossification is bone replacing existing tissue. 

  • Calcification is the process of depositing calcium salts into tissues. 


Factors regulating bone growth
Factors Regulating Bone Growth

  • Ions:

    • Calcium, phosphate, magnesium, citrate, carbonate, sodium

  • Vitamins:

    • Vitamins A and C

    • Vitamin D derivatives


Factors regulating bone growth1
Factors Regulating Bone Growth

  • Parathyroid hormone (PTH) acts to increase overall availability of calcium ions in the blood.

    • Increased osteoclast activity is the direct result of PTH levels.  

  • Calcitonin is the antagonist of PTH.

  • Growth hormone and thyroxine increase osteoblast activity leading to bone growth.

  • Sex hormones increase bone growth dramatically during puberty.


Hormonal control of bone tissue
Hormonal Control of Bone Tissue

Human Growth Hormone (hGH):

(Pituitary gland)

Thyroxine:

(Thyroid gland)

Stimulate

Osteoblasts

Sex Hormones:

(estrogen, progesterone, testosterone)

(Ovaries and Testes)

Calcitonin:

Inhibits Osteoclasts

(Thyroid gland)

Parathyroid Hormone:

(Parathyroid gland)

Stimulates Osteoclasts

Calcitriol:

Increases Ca2+ absorption

from intestine.

(Skin and kidneys)


Bone disorders
Bone disorders

  • Ricketts

  • Osteoporosis


Intramembranous ossification
Intramembranous Ossification

[Insert fig 5.5]

Figure 5.5 Intramembranous Ossification



Endochondral ossification
Endochondral Ossification

  • Bone development from hyaline cartilage

  • Bone growth in length

  • Shotgun Biology




Endochondral ossification1
Endochondral Ossification

Figure 5.8 Epiphyseal Cartilages and Lines


Steps of endochondral ossification

1. The perichondrium covering the hyaline cartilage “bone” is infiltrated with blood

vessels.

2. Osteoblasts secrete osteoid against the hyaline cartilage diaphysis, encasing it in a bony collar.

STEPS OF ENDOCHONDRAL OSSIFICATION


Steps of endochondral ossification1

3. Chondrocytes within the diaphysis hypertrophy and the surrounding cartilage matrix starts to be calcified.

4. The chondrocytes, however, die and the matrix begins to deteriorate.

STEPS OF ENDOCHONDRAL OSSIFICATION


Steps of endochondral ossification2

5. In month 3, the forming cavities are invaded by a collection of elements called the periosteal bud.

6. The entering osteoclasts partially erode the calcified cartilage matrix.

STEPS OF ENDOCHONDRAL OSSIFICATION


Steps of endochondral ossification3
STEPS OF ENDOCHONDRAL OSSIFICATION collection of elements called the periosteal bud.


Steps of endochondral ossification4

7. Osteoblasts secrete osteoid around the remaining fragments of hyaline cartilage forming trabeculae of spongy bone.

STEPS OF ENDOCHONDRAL OSSIFICATION


Steps of endochondral ossification5

8. As the primary ossification center enlarges, osteoclasts break down the newly formed spongy bone and open up a medullary cavity in the center of the diaphysis.

STEPS OF ENDOCHONDRAL OSSIFICATION


Steps of endochondral ossification6

9. The epiphyses remain formed of cartilage until shortly before or after birth.

10. Secondary ossification centers form in the epiphyses. The events of ossification are like the events of the diaphysis, except, that spongy bone mains in the internal and no medullary cavity forms.

STEPS OF ENDOCHONDRAL OSSIFICATION


Steps of endochondral ossification7
STEPS OF ENDOCHONDRAL OSSIFICATION before or after birth.


Steps of endochondral ossification8
STEPS OF ENDOCHONDRAL OSSIFICATION before or after birth.


Epiphyseal before or after birth.

plate

LONGITUDINAL BONE GROWTH


Bone growth
BONE GROWTH before or after birth.


Injury and repair
Injury and Repair before or after birth.

Figure 5.11 Fracture Repair


Bone markings
Bone Markings before or after birth.

Table 5.1 Common Bone Marking Terminology


Classification of bones
Classification of Bones before or after birth.

Figure 5.13 Shapes of Bones


Bone markings1
Bone Markings before or after birth.

Figure 5.14 Examples of Bone Markings


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