SKELETAL TISSUES
CHAPTER 7
By John McGill
Supplement Outlines: Beth Wyatt
Original PowerPoint: Jack Bagwell
INTRODUCTION TO THE
SKELETAL SYSTEM
• STRUCTURE
– Organs: Bones
– Related Tissues: Cartilage and Ligaments
• PRIMARY FUNCTION
– Support
• PRIMARY TISSUES OF THE SKELETAL
SYSTEM
– BONE TISSUE
– CARTILAGE
• Connective Tissues
TYPES OF BONES
• LONG: Long and Narrow
• Humerus and femur
• SHORT: Cube/BoxShaped
– carpus and tarsus
– found in parts of skeleton
that require strength and
limited movement
• FLAT: Flat and Thin
• IRREGULAR: Complex
Shapes
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MACROSCOPIC
STRUCTURE:
Long Bones
• DIAPHYSIS
– Shaft
– Composed of Compact
Bone
• EPIPHYSES
– Both Ends Composed of
Cancellous Bone
• ARTICULAR
CARTILAGE
– “Joining Cartilage”
– Covers Epiphyses (Thin
Layer)
– Provides Cushioning at
Joints
MACROSCOPIC
STRUCTURE:
Long Bones
• PERIOSTEUM
–
–
–
–
–
Bone’s Covering
White
Thin but Tough
“Welded” to Underlying Bone
Contains Blood Vessels
• MEDULLARY (MARROW)
CAVITY
– Space Within the Diaphysis
– Contains Bone Marrow
• ENDOSTEUM
– Lines the Medullary Cavity
– Thin
MACROSCOPIC STRUCTURE:
SHORT, FLAT, IRREGULAR BONES
• Inner Portion:
Cancellous Bone
– “spongy bone”
• Surfaces: Compact
Bone
– dense and solid
• Periosteum Present
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MICROSCOPIC STRUCTURE OF BONE:
COMPACT BONE:
• HAVERSIAN
SYSTEMS
(OSTEONS)
– Microscopically,
Compact Bone is
Composed of
Haversian Systems
– Haversian Systems:
Microscopic Structural
Units of Compact
Bone
Microscopic structure - Haversian System
• Haversian system (osteon)consists of the canal and
surrounding structures
• Lamellae – concentric layers of
calcified matrix
• Lacunae – “little lakes”; where the
bone cells live
• Canaliculi – very small canals that
radiate from the lacunae; carry
nutrients
• Haversian canal – central canal
which carries blood vessels
•
FUNCTION OF HAVERSIAN SYSTEMS
– Blood Supply to Compact Bone
– Periosteum Æ Haversian Canals Æ
Canalculi Æ Lacunae
BONE (MICROSCOPIC VIEW)
canaliculi
osteocyte in lacunae
Haversian canal
ossified matrix (lamellae)
3
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 Æ
Bone Marrow Æ Openings in Trabeculae)
BONE TISSUE (OSSEOUS TISSUE)
• COMPONENTS: MATRIX, PROTEIN FIBERS, CELLS
– Typical Connective Tissue
• COMPOSITION OF BONE MATRIX
– INORGANIC COMPONENTS
• Minerals (Esp. Ca and Phosphate)
• Forms hydroxyapatite
• Constitute Approx. 65% of Bone Matrix
• Gives Matrix Hardness and Strength
– ORGANIC COMPONENTS
• Complex Mixture of Carbohydrates and Proteins
• Gives Matrix Strength
• PROTEIN FIBERS: COLLAGENOUS
– Also Gives Matrix Strength
• *NOTE: Matrix with Protein Fibers Means Hardness and
Strength
BONE CELLS
• OSTEOBLASTS
– Bone-Forming Cells
– Location: Periosteum (Primarily)
• OSTEOCLASTS
– Bone-Destroying Cells
– Location: Endosteum (Primarily)
• OSTEOCYTES
– Bone Cells (Mature Osteoblasts)
– Locations:
• 1) Compact Bone: Lacunae
• 2) Cancellous Bone: Trabeculae
4
BONE MARROW (MYELOID TISSUE)
• Tissue Type:
Connective Tissue
(Reticular)
• LOCATIONS
– Long Bones:
• Medullary Cavity
• Epiphyses:
– Spaces in Cancellous Bone
– Short, Flat, Irregular
Bones:
• Spaces in Cancellous
Bone
BONE MARROW TYPES:
RED MARROW
• DESCRIPTION/FUNCTIONS
– Red in Color Because
Functions in Hematopoiesis
• 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
BONE MARROW TYPES:
YELLOW MARROW
• 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
• LOCATIONS
– Most Bones in Adults Contain
Yellow Marrow
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Functions of Bones
• Support – support the weight of the rest of
the body
• Protection – protect the delicate body parts
• Movement – muscles attach to bone and
allow movement
• Mineral storage – calcium, phosphorous,
and other minerals are stored in the bone
• Hematopoiesis – red marrow plays an
important role in the formation of red blood
cells, some flat bones also play a role here
DEVELOPMENT OF
BONE
(OSTEOGENESIS)
• How Bones Form in the Fetus
• INTRAMEMBRANOUS OSSIFICATION
– DEFINITION
• “Within Membrane Bone
Formation”
• Method by Which Flat Bones
•Intramembranous bone formation in
Form
a fetal pig skull.
•Flat bones of the skull develop by IO. • MECHANISM
•Embryonic mesenchyme cells form
– Connective Tissue Membrane Æ
a membrane (Mes) &
– Cells Develop Into Osteoblasts Æ
•differentiate into osteoblasts that
•form bony spicules or cancellous
– Secrete Organic Matrix and
bone (CsB).
Collagenous FibersÆ
•Eventually osteonsform.
– Calcification Occurs
DEVELOPMENT OF BONE (OSTEOGENESIS)
ENDOCHONDRAL
OSSIFICATION
• Embryonal hyaline
cartilage precedes
bone formation.
• Inner cells change
into osteoblasts cells
in the perichondrium.
• Osteoblasts form the
periosteum.
• ENDOCHONDRAL OSSIFICATION
– DEFINITION
• “Within Cartilage Bone
Formation”
• Method by Which Most Bones
Form
– MECHANISM
• Cartilage Model Æ
• Periosteum Forms Æ
• Cells Develop Into
Osteoblasts Æ
• Secrete Organic Matrix and
Collagenous FibersÆ
• Calcification Occurs
– *Note: In Both Types of
Ossification:
• Osteoclasts Resorb Bone Æ
• Forms Medullary Cavity,
Spaces in Cancellous Bone
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Summary: Endochondral Ossification
• Bone forms from a cartilage model
• Osteoblasts begin to calcify the cartilage
• Osteoblasts and osteoclasts are constantly
reshaping the bone
• Centers of ossification appear in the
epiphyses
• Epiphyseal plate is site of continued bone
growth; indicates the bone is not yet
mature.
Osteogenesis (Bone formation)
• The cartilaginous skeleton is changed to bone in one
of two ways:
• Intramembranous ossification – happens in some flat
bones of body
– 1st step – cells differentiate into osteoblasts (centers of
ossification)
– 2nd – cells secrete ground substance
– 3rd – ground substance is calcified
– 4th – trabelculae appear and join to form spongy bone
– 5th - layer of spongy bone is covered on both sides by
compact bone
– 6th – growth occurs by appositional growth – the addition of
osseous tissue to its outer surface
Bone Growth - Animation
•http://www.anatomy.gla.ac.uk/fab/tutorial/generic/bonet.html
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FETAL SKELETON
BONE GROWTH AND RESORPTION
• How Bones Increase in Size after Birth
• Involves Bone Resorption : Destruction
• BONE GROWTH
– FLAT BONES (Also Short, Irregular Bones)
• APPOSITIONAL GROWTH
– Growth By Adding to the Surfaces
– LONG BONES
• 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
EPIPHYSEAL PLATE
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Epiphyseal Plate
• The epiphyseal plate
allows for growth in
bones.
Zones of the
Epiphyseal Plate
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)
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BONE GROWTH AND RESORPTION
• BONE RESORPTION
– Osteoclasts (Endosteum) Destroy Bone
from the Inner Surface of the Medullary
Cavity
BONE GROWTH AND RESORPTION
• BONE GROWTH AND RESORPTION
THROUGHOUT LIFE
– Both Growth and Resorption Go On
Throughout Life, But at Different Rates
• From Infancy Æ 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 Æ Old Age:
Resorption EXCEEDS Growth (Bones
Become Thinner, More Susceptible to
Fracture and Disease)
BONE GROWTH AND RESORPTION
• 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)
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REPAIR OF
BONE
FRACTURES
• FRACTURE: A Break in
the Continuity of Bone
FRACTURE HEALING
• VASCULAR DAMAGE
– Damage to Blood
Vessels
FRACTURE HEALING
• FORMATION OF
FRACTURE HEMATOMA
– Blood Clot Forms in
the Area of the
Fracture in Order to
Stop Bleeding
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FRACTURE HEALING
• FORMATION OF
CALLUS TISSUE
– Thickened Repair
Tissue That Binds the
Ends of the Bones
Together (Reason
That the Fracture is
Aligned and
Immobilized)
FRACTURE HEALING
• REPLACEMENT BY
BONE
– Callus Tissue
Becomes Bone (Action
of Osteoblasts),
Remodeled by
Osteoclasts
Epiphyseal Plate Fracture
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CARTILAGE
• CHARACTERISTICS
– MATRIX
• FIRM/FLEXIBLE GEL
– PROTEIN FIBERS
• COLLAGENOUS
– CELLS
• CHONDROCYTES
• Chondrocytes Lie in
Lacunae
– AVASCULAR: Oxygen
and Nutrients by Diffusion
CARTILAGE: Types
• Hyaline
• Elastic
• Fibrocartilage
HYALINE CARTILAGE
• Most Abundant and
Common
• Shiny
• Semitransparent
• Locations:
– Articular Cartilage
– Costal Cartilages
– Cartilage Rings in
Trachea and Bronchi
– Tip of Nose
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ELASTIC CARTILAGE
• Has Fewer Collagenous
Fibers Compared to
Hyaline
• In Addition, Contains
Elastic Fibers
• Locations:
– External Ear
– Epiglottis
– Eustachian Tube
FIBROCARTILAGE
• Cartilage With the
Most Collagenous
Fibers
• Locations:
– Symphysis Pubis
– Intervertebral Disks
– Menisci in Knee
GROWTH OF CARTILAGE
• INTERSTITIAL (ENDOGENOUS)
GROWTH
– DEFINITION: “Growth From Within”
– OCCURS WHEN: During Childhood and
Adolescence
• APPOSITIONAL (EXOGENOUS)
GROWTH
– DEFINITION: “Growth by Adding to the
Surfaces”
– OCCURS WHEN: During Adulthood
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