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BIO121-CHP5

The Skeletal System: Osseous Tissue and Skeletal Structure
by

Kimberly Fournier

on 18 September 2013

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Transcript of BIO121-CHP5

Announcements
*Chapter 6 Next Time

*Information for the Exam Instruction
Quiz can be found in syllabus!
Chapter 5 - Skeletal System
BIO121 - Human Anatomy
Osseous Tissue and Skeletal Structure
Structure of Bone
Bone Maintenance, Remodeling & Repair
Bone Development & Growth
Anatomy of Skeletal Elements
PowerPoint® Lecture Presentations prepared by Steven Bassett
Southeast Community College, Lincoln, Nebraska
Adapted by Kimberly Fournier, for BIO121, The University of Rhode Island
The Periosteum and Endosteum

Periosteum
Outer surface of the bone

Isolates and protects the bone from surrounding tissue

Provides a route and a place for attachment for circulatory and nervous supply

Actively participates in bone growth and repair

Attaches the bone to the connective tissue network of the deep fascia
Structure of Bone
Two types of osseous tissue

Compact bone (dense bone)
Compact bones are dense and solid
Forms the walls of bone outlining the medullary cavity
Medullary cavity consists of bone marrow

Spongy bone (trabecular bone)
Open network of plates
Structure of Bone
The Osteon
It is the basic unit of skeletal bones

Consists of:
Central canal
Canaliculi
Osteocytes
Lacunae
Lamellae
Structure of Bone
The Histological Organization of Mature Bone

Collagen fibers
Make up
2/3
of the bone matrix
Contribute to the tensile strength of bones
Collagen and hydroxyapatite make bone tissue extremely strong

Bone cells
Contribute only 2% of the bone mass
Structure of Bone
The Histological Organization of Mature Bone

The matrix
Calcium phosphate eventually converts to hydroxyapatite crystals
Hydroxyapatite crystals resist compression
Structure of Bone
The skeletal system is made of:

Skeletal bones
Cartilage
Ligaments
Connective tissue to stabilize the skeleton

Bones are dynamic organs, which consist of several tissue types
Introduction
The Periosteum and Endosteum

Endosteum
Inner surface of bone
Lines the medullary cavity
Consists of osteoprogenitor cells
Actively involved in repair and growth
Structure of Bone
The Periosteum and Endosteum

Periosteum and Tendons
Tendons are cemented into the lamellae by osteoblasts
Therefore, tendons are actually a part of the bone
Structure of Bone
Organization of Compact and Spongy Bone

Epiphysis
Each end of the long bones

Diaphysis
Shaft of the long bones

Metaphysis
Narrow growth zone between the epiphysis and the diaphysis
Structure of Bone
Functional Differences

Compact bone
Conducts stress from one area of the body to another area of the body

Generates tremendous strength from end to end

Weak strength when stress is applied to the side

Spongy bone
Trabeculae create strength to deal with stress from the side
Structure of Bone
Structural Differences

Compact bone
Consists of osteons
Makes up the dense, solid portion of bone

Spongy bone
Trabeculae are arranged in parallel struts
Trabeculae form branching plates
Trabeculae form an open network
Creates the lightweight nature of bones
Structure of Bone
The Cells of Mature Bone (continued)

Osteoprogenitor cells
Found on the inner and outer surfaces of bones

Differentiate to form new osteoblasts

Heavily involved in the repair of bones after a break

Osteoclasts
Secrete acids, which dissolve the bones thereby causing the release of stored calcium ions and phosphate ions into the blood

This process is called osteolysis
Structure of Bone
The Cells of Mature Bone

Osteocytes
Mature bone cells
Maintain the protein and mineral content of the matrix

Osteoblasts
Immature bone cells
Found on the inner and outer surfaces of bones
Produce osteoid, which is involved in making the matrix
Osteoblasts are involved in making new bone. This is a process called osteogenesis
Osteoblasts can convert to osteocytes
Structure of Bone
Bones (osseous tissue)

Supporting connective tissue
Specialized cells
Solid matrix

Outer lining
Called the periosteum

Inner lining
Called the endosteum
Structure of Bone
Functions of the skeletal system (continued)

Leverage
Muscles pull on the bones to produce movement

Protection
Ribs protect heart and lungs
Skull protects the brain
Vertebrae protect the spinal cord
Pelvic bones protect the reproductive organs
Introduction
Functions of the skeletal system

Support
Provides the framework for the attachment of other organs

Storage of minerals
Calcium ions: 98% of the body’s calcium ions are in the bones
Phosphate ions

Blood cell production
Bone marrow produces erythrocytes, leukocytes, and platelets
Introduction
Figure 5.3b Anatomy of a Representative Bone
Figure 5.3c Anatomy of a Representative Bone
Figure 5.2d The Internal Organization in Representative Bones
Figure 5.1b Histological Structure of a Typical Bone
Figure 5.1c Histological Structure of a Typical Bone
Figure 5.4c Anatomy and Histology of the Periosteum and Endosteum
Figure 5.1d Histological Structure of a Typical Bone
Figure 5.3a Anatomy of a Representative Bone
Figure 5.3a Anatomy of a Representative Bone
Figure 5.1a Histological Structure of a Typical Bone
Figure 5.4ab Anatomy and Histology of the Periosteum and Endosteum
Figure 5.2a-c The Internal Organization in Representative Bones
Factors Regulating Bone Growth (continued)
Hormones: Pituitary gland

Releases growth hormone (somatotropin)

Maintains normal activity of the epiphyseal cartilage
Bone Development and Growth
Factors Regulating Bone Growth (continued)
Hormones: Thyroid gland

Releases thyroxine (T4)

Maintains normal activity of the epiphyseal cartilage
Bone Development and Growth
Factors Regulating Bone Growth (continued)
Hormones: Thyroid gland

Releases calcitonin

Inhibits osteoclasts

Removes calcium ions from blood and adds it to bone
Bone Development and Growth
Factors Regulating Bone Growth (continued)
Hormones: Parathyroid gland
Releases parathyroid hormone

Stimulates osteoclasts

Stimulates osteoblasts

Increases calcium ion absorption from the small intestine to the blood
Bone Development and Growth
Factors Regulating Bone Growth
Nutrition
Calcium ions
Phosphate ions
Magnesium ions
Citrate
Carbonate ions
Sodium ions
Vitamins A, C, D (calcitriol)
Bone Development and Growth
Four major sets of blood vessels (continued)

Epiphyseal vessels
Supply nutrients to the medullary cavities of the epiphysis

Periosteal vessels
Supply nutrients to the superficial osteons
Bone Development and Growth
Enlarging the diameter of bone
Called appositional growth

Blood vessels that run parallel to the bone becomes surrounded by bone cells

“Tunnels” begin to form

Each “tunnel” has a blood vessel in it
Bone Development and Growth
Epiphyseal plate
Area of cartilage in the metaphysis

Also called the epiphyseal cartilage

Cartilage near the diaphysis is converted to bone

The width of this zone gets narrower as we age
Bone Development and Growth
Endochondral ossification (continued)
The cartilage near the epiphysis converts to bone

Blood vessels penetrate the epiphysis

Osteoblasts begin to develop spongy bone in the epiphysis

Epiphysis becomes the secondary center of ossification
Bone Development and Growth
Endochondral ossification
The developing bone begins as cartilage cells

Cartilage matrix grows inward
Interstitial growth

Cartilage matrix grows outward
Appositional growth

Blood vessels grow around the cartilage
Bone Development and Growth
There are two types of ossification

Intramembranous ossification
Involved in the development of clavicle, mandible, skull, and face

Endochondral ossification
Involved in the development of limbs, vertebrae, and hips
Bone Development and Growth
Before six weeks of development, the skeleton is cartilage
Cartilage cells will be replaced by bone cells
This is called ossification

Osteogenesis
Bone formation

Calcification
The deposition of calcium ions into the bone tissue
Bone Development and Growth
There are four major sets of blood vessels associated with the long bones

Nutrient vessels
Enter the diaphysis and branch toward the epiphysis

Re-enter the compact bone, leading to the central canals of the osteons

Metaphyseal vessels
Supply nutrients to the diaphyseal edge of the epiphysis
Bone Development and Growth
Enlarging the diameter of bone
Osteoblasts begin to produce matrix, thus creating concentric rings

As osteoblasts are laying down more bone material, osteoclasts are dissolving the inner bone, thus creating the marrow cavity
Bone Development and Growth
Endochondral ossification (continued)
Perichondrial cells convert to osteoblasts

Osteoblasts develop a superficial layer of bone around the cartilage

Blood vessels penetrate the cartilage

Osteoblasts begin to develop spongy bone in the diaphysis

This becomes the primary center of ossification
Bone Development and Growth
Intramembranous ossification
Mesenchymal cells differentiate to form osteoblasts

Osteoblasts begin secreting a matrix

Osteoblasts become trapped in the matrix

Osteoblasts differentiate and form osteocytes

More osteoblasts are produced, thus move outward

Eventually, compact bone is formed
Bone Development and Growth
Figure 5.8 Epiphyseal Cartilages and Lines
Figure 5.9a Appositional Bone Growth (Part 2 of 2)
Figure 5.9b Appositional Bone Growth
Figure 5.9a Appositional Bone Growth (Part 1 of 2)
Figure 5.7a Anatomical and Histological Organization of Endochondral Ossification (Part 1 of 2)
Figure 5.7b Anatomical and Histological Organization of Endochondral Ossification (Part 2 of 2)
Figure 5.7a Anatomical and Histological Organization of Endochondral Ossification (Part 2 of 2)
Figure 5.7b Anatomical and Histological Organization of Endochondral Ossification (Part 1 of 2)
Figure 5.10 Circulatory Supply to a Mature Bone
Figure 5.5 Histology of Intramembranous Ossification
Figure 5.7 Anatomical and Histological Organization of Endochondral Ossification
Figure 5.6 Fetal Intramembranous and Endochondral Ossification
Injury and Repair
When a bone is broken, bleeding occurs

A network of spongy bone forms

Osteoblasts are overly activated, thus resulting in enlarged callused area

This area is now stronger and thicker than normal bone
Bone Maintenance, Remodeling, and Repair
Aging and the Skeletal System
As women age, estrogen levels drop

Osteoclast control is lost
Osteoclasts are overactive

Bones become porous
This is osteoporosis
Bone Maintenance, Remodeling, and Repair
Aging and the Skeletal System
When we’re young, osteoblast activity balances with osteoclast activity

When we get older, osteoblast activity slows faster than osteoclast activity

When osteoclast activity is faster than osteoblast activity, bones become porous

Estrogen keeps osteoclast activity under control
Bone Maintenance, Remodeling, and Repair
Clinical Note 5.3 Fractures and Their Repair (Part 4 of 4)
Clinical Note 5.3 Fractures and Their Repair (Part 3 of 4)
Table 5.1 Common Bone Marking Terminology
Bone markings include:
Projections
Depressions
Fissures
Foramina
Canals (meatuses)
Anatomy of Skeletal Elements
There are seven broad categories of bones according to their shapes
Sutural bones
Irregular bones
Short bones
Pneumatized bones
Flat bones
Long bones
Sesamoid bones
Anatomy of Skeletal Elements
Figure 5.12c Examples of Bone Markings (Surface Features)
Figure 5.12b Examples of Bone Markings (Surface Features)
Figure 5.12e Examples of Bone Markings (Surface Features)
Figure 5.12d Examples of Bone Markings (Surface Features)
Figure 5.12a Examples of Bone Markings (Surface Features)
Figure 5.11 Shapes of Bones
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