BIO 210 CHAPTER 7 SKELETAL TISSUES – SUPPLEMENT
I.
II.
III.
IV.
INTRODUCTION TO THE SKELETAL SYSTEM
A.
STRUCTURE
Organs: Bones
Related Tissues: Cartilage and Ligaments
B.
PRIMARY FUNCTION
Support
PRIMARY TISSUES OF THE SKELETAL SYSTEM
A.
BONE TISSUE
B.
CARTILAGE
Connective Tissues
TYPES OF BONES
A.
LONG: Long and Narrow
B.
SHORT: Cube/Box-Shaped
C.
FLAT: Flat and Thin
D.
IRREGULAR: Complex Shapes
E.
MACROSCOPIC STRUCTURE
1.
LONG BONES
a.
DIAPHYSIS
Shaft
Composed of Compact Bone
b.
EPIPHYSES
Both Ends
Composed of Cancellous Bone
c.
ARTICULAR CARTILAGE
“Joining Cartilage”
Covers Epiphyses (Thin Layer)
Provides Cushioning at Joints
d.
PERIOSTEUM
Bone’s Covering
White
Thin but Tough
“Welded” to Underlying Bone
Contains Blood Vessels
e.
MEDULLARY (MARROW) CAVITY
Space Within the Diaphysis
Contains Bone Marrow
f.
ENDOSTEUM
Lines the Medullary Cavity
Thin
2.
SHORT, FLAT, IRREGULAR BONES
Inner Portion: Cancellous Bone
Surfaces: Compact Bone
Periosteum Present
MICROSCOPIC STRUCTURE OF BONE
A.
COMPACT BONE: HAVERSIAN SYSTEMS (OSTEONS)
Microscopically, Compact Bone is Composed of Haversian
Systems
Haversian Systems: Microscopic Structural Units of Compact
Bone
1.
STRUCTURE OF HAVERSIAN SYSTEMS
Each Haversian System Composed of 4 Structures
a.
LAMELLAE
Rings of Bone Matrix
V.
VI.
Concentric
Cylindrical (Extend Lengthwise)
b.
LACUNAE
“Little Lakes”
Microscopic Fluid - Filled Spaces in Bone Matrix
House Osteocytes
c.
CANALICULI
Microscopic Canals in Bone Matrix
Contain Blood Vessels
Connect Lacunae to Each Other and Connect
Lacunae to Haversian Canal
d.
HAVERSIAN CANAL
Central Canal
Extends Lengthwise Through Each Haversian
System
Contains Blood Vessels and Nerves
2.
FUNCTION OF HAVERSIAN SYSTEMS
Blood Supply to Compact Bone
Periosteum  Haversian Canals  Canalculi  Lacunae
B.
CANCELLOUS BONE:TRABECULAE
Trabeculae: Needlelike Pieces of Bone (Surround Spaces)
Contains Osteocytes
How Cancellous Bone Gets Its Blood Supply: From Bone Marrow by Diffusion
(Periosteum  Bone Marrow  Openings in Trabeculae)
BONE TISSUE (OSSEOUS TISSUE)
A.
COMPONENTS: MATRIX, PROTEIN FIBERS, CELLS
Typical Connective Tissue
B.
COMPOSITION OF BONE MATRIX
1.
INORGANIC COMPONENTS
Minerals (Esp. Ca and Ph)
Constitute Approx. 65% of Bone Matrix
Gives Matrix Hardness and Strength
2.
ORGANIC COMPONENTS
Complex Mixture of Carbohydrates and Proteins
Gives Matrix Strength
C.
PROTEIN FIBERS: COLLAGENOUS
Also Gives Matrix Strength
*NOTE: Matrix with Protein Fibers Means Hardness and Strength; Complements
Functions 1 and 2
D.
CELLS
1.
OSTEOBLASTS
Bone-Forming Cells
Location: Periosteum (Primarily)
2.
OSTEOCLASTS
Bone-Destroying Cells
Location: Endosteum (Primarily)
3.
OSTEOCYTES
Bone Cells (Mature Osteoblasts)
Locations: 1) Compact Bone: Lacunae, 2) Cancellous
Bone: Trabeculae
BONE MARROW (MYELOID TISSUE)
Tissue Type: Connective Tissue (Reticular)
A.
LOCATIONS
Long Bones: Medullary Cavity, Epiphyses: Spaces in Cancellous Bone
Short, Flat, Irregular Bones: Spaces in Cancellous Bone
B.
TYPES
1.
VII.
VIII.
RED MARROW
a.
DESCRIPTION/FUNCTIONS
Red in Color Because Functions in Hematopoiesis
b.
LOCATIONS
Children: All Bones Contain Red Marrow
Adults: Certain Bones Contain Red Marrow
Flat Bones of the Skull
Sternum, Ribs, Vertebrae
Pelvic Bones
Epiphyses of Humerus and Femur
2.
YELLOW MARROW
a.
DESCRIPTION/FUNCTIONS
Yellow in Color Because Contains Largely Adipose Tissue
Yellow Marrow Was Once Red Marrow, Now Yellow B/C
It No Longer Functions in Hematopoiesis (D/T Decreased
Demand for Hematopoiesis in Adults)
b.
LOCATIONS
Most Bones in Adults Contain Yellow Marrow
FUNCTIONS OF BONES
A.
SUPPORT
Major Function; Bones are Body’s Supporting Framework
Due to Structure of Bones (Hardness, Strength)
B.
PROTECTION
Bones Protect Organs
Examples: Skull Bones Protect Brain, Vertebral Column Protects Spinal Cord,
Rib Cage Protects Heart and Lungs, etc.
Due to Structure of Bones (Hardness, Strength)
C.
MOVEMENT
Movement is the Result of Bones and Muscles Working Together
Skeletal Muscles are Attached to Bones, Muscle Contracts, Pulls on a Bone(s),
Produces Movement at a Joint
D.
MINERAL STORAGE
Bones Store Minerals (Esp, Ca, Ph)
Helps Maintain Homeostasis of Blood Mineral Levels
Example: Increased Blood Ca  Ca Moves from Blood to Bone (Hormone
Controlled)  Decreases Blood Ca Levels
E.
HEMATOPOIESIS
Blood Cell Formation, Function of Red Bone Marrow
DEVELOPMENT OF BONE (OSTEOGENESIS)
How Bones Form in the Fetus
A.
INTRAMEMBRANOUS OSSIFICATION
1.
DEFINITION
“Within Membrane Bone Formation”
Method by Which Flat Bones Form
2.
MECHANISM
Connective Tissue Membrane  Cells Develop Into
Osteoblasts  Secrete Organic Matrix and Collagenous Fibers 
Calcification Occurs
B.
ENDOCHONDRAL OSSIFICATION
1.
DEFINITION
“Within Cartilage Bone Formation”
Method by Which Most Bones Form
2.
MECHANISM
Cartilage Model  Periosteum Forms  Cells Develop Into
Osteoblasts  Secrete Organic Matrix and Collagenous Fibers 
Calcification Occurs
IX.
X.
XI.
*Note: In Both Types of Ossification: Osteoclasts Resorb Bone  Forms Medullary
Cavity, Spaces in Cancellous Bone
BONE GROWTH AND RESORPTION
How Bones Increase in Size after Birth
Involves Bone Resorption : Destruction
A.
BONE GROWTH
1.
FLAT BONES (Also Short, Irregular Bones) –
APPOSITIONAL GROWTH
Growth By Adding to the Surfaces
2.
LONG BONES
a.
GROWTH IN LENGTH – EPIPHYSEAL PLATE
Epiphyseal Plate: Layer of Hyaline Cartilage That Lies B/T
Epiphyses and Diaphysis
Didn’t Ossify During the Fetal Period (Purpose: To Allow
Bone Growth in Length)
Epiphyseal Plate 1) Thickens and 2) Ossifies Repeatedly
When Growth in Length is Complete, Cells in EP Stop
Mitosis and the Entire Plate Ossifies, What Remains is
Epiphyseal Line
b.
GROWTH IN DIAMETER – COMBINED ACTION OF OSTEOBLASTS AND OSTEOCLASTS
Osteoblasts (Periosteum) Build New Bone on the Outer
Surface
Osteoclasts (Endosteum) Destroy Bone from the Inner
Surface of the Medullary Cavity (Enlarges Med. Cavity)
B.
BONE RESORPTION
C.
BONE GROWTH AND RESORPTION THROUGHOUT LIFE
Both Growth and Resorption Go On Throughout Life, But at Different
Rates
From Infancy  Young Adulthood: Growth EXCEEDS Resorption
(Bones Grow and are Thick)
During Late 20’s/Early 30’s: Growth EQUALS Resorption
(Bones Remain Relatively Constant)
From Mid 30’s/Early 40’s  Old Age: Resorption EXCEEDS Growth
(Bones Become Thinner, More Susceptible to Fracture and Disease)
D.
BONES RESPONSE TO STRESS
Bone Stress = Weight Bearing Applied to Bones
Bone Stress Increases the Activity of the Osteoblasts (Helps Offset the Effects
of Aging on Bones)
REPAIR OF BONE FRACTURES
A.
FRACTURE: A Break in the Continuity of Bone
B.
FRACTURE HEALING
1.
VASCULAR DAMAGE
Damage to Blood Vessels
2.
FORMATION OF FRACTURE HEMATOMA
Blood Clot Forms in the Area of the Fracture in Order to Stop
Bleeding
3.
FORMATION OF CALLUS TISSUE
Thickened Repair Tissue That Binds the Ends of the Bones
Together (Reason That the Fracture is Aligned and Immobilized)
4.
REPLACEMENT BY BONE
Callus Tissue Becomes Bone (Action of Osteoblasts), Remodeled
by Osteoclasts
CARTILAGE
A.
CHARACTERISTICS
1.
MATRIX (FIRM/FLEXIBLE GEL),
B.
C.
PROTEIN FIBERS (COLLAGENOUS),
CELLS (CHONDROCYTES)
Chondrocytes Lie in Lacunae
2.
AVASCULAR: Oxygen and Nutrients by Diffusion
TYPES
1.
HYALINE CARTILAGE
Most Abundant and Common
Shiny; Semitransparent
Locations: Articular Cartilage, Costal Cartilages, Cartilage Rings
in Trachea and Bronchi, and Tip of Nose
2.
ELASTIC CARTILAGE
Has Fewer Collagenous Fibers Compared to Hyaline
In Addition, Contains Elastic Fibers
Locations: External Ear, Epiglottis, and Eustachian Tube
3.
FIBROCARTILAGE
Cartilage With the Most Collagenous Fibers
Locations: Symphysis Pubis, Intervertebral Disks, Menisci in Knee
GROWTH OF CARTILAGE
1.
INTERSTITIAL (ENDOGENOUS) GROWTH
a.
DEFINITION: “Growth From Within”
b.
OCCURS WHEN: During Childhood and Adolescence
2.
APPOSITIONAL (EXOGENOUS) GROWTH
a.
DEFINITION: “Growth by Adding to the Surfaces”
b.
OCCURS WHEN: During Adulthood