What is?
Hematopoiesis
Bone Formation
• Fetal
– INTRAMEMBRANOUS
OSSIFICATION
– ENDOCHONDRAL OSSIFICATION
• From birth to young adult
– APPOSITIONAL (flat, short, irregular
bones)
• Increase diameter for ALL bones
– INTERSTITIAL (EPIPHYSEAL PLATE)
• Increase length
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
• These are both Connective Tissues
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
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  Haversian Canals  Canalculi 
Lacunae
BONE (MICROSCOPIC VIEW)
canaliculi
osteocyte in lacunae
Haversian canal
ossified matrix (lamellae)
CANCELLOUS BONE:
TRABECULAE
• Trabeculae: Needlelike Pieces of Bone
(Surround Spaces)
• Contains Osteocytes
• How Cancellous Bone Gets Its Blood Supply:
– Periosteum  Bone Marrow  Openings in
Trabeculae
BONE TISSUE is
OSSEOUS TISSUE
COMPONENTS: MATRIX, PROTEIN
FIBERS, CELLS
• Typical Connective Tissue
COMPOSITION OF BONE MATRIX
• INORGANIC COMPONENTS
• Minerals (Esp. Ca and Phosphate)
• Forms hydroxyapatite
• Gives Matrix Hardness and Strength
• ORGANIC COMPONENTS
• Complex Mixture of Carbohydrates and Proteins
• Gives Matrix Strength
• PROTEIN FIBERS: COLLAGENOUS
Types of 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
BONE MARROW is MYELOID TISSUE
Myeloid tissue is a
biologic tissue with the
ability to perform
hematopoiesis.
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/FUNCTIO
NS
– 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
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
Fetal Bone Formation
Osteogenesis
• The cartilaginous skeleton is changed to
bone in one of two ways:
– Intramembranous ossification
– Endochondral ossification
#1.
INTRAMEMBRANOUS
OSSIFICATION
• How Bones Form in the Fetus
– DEFINITION
• “Within Membrane Bone
Formation”
•Intramembranous bone formation in
• Method by Which Flat Bones
a fetal pig skull.
Form
•Flat bones of the skull develop by IO.
•Embryonic mesenchyme cells form • MECHANISM
a membrane (Mes) &
– Connective Tissue Membrane 
•differentiate into osteoblasts that
– Cells Develop Into Osteoblasts 
•form bony spicules or cancellous
bone (CsB).
– Secrete Organic Matrix and
•Eventually osteonsform.
Collagenous Fibers
– Calcification Occurs
#2. ENDOCHONDRAL OSSIFICATION
• Embryonal hyaline cartilage
is model for bone formation.
• Osteoblasts begin to calcify
the cartilage
• Osteoblasts and osteoclasts
are constantly reshaping the
bone
• Epiphyseal plate is site of
continued bone growth;
indicates the bone is not yet
mature.
• ENDOCHONDRAL OSSIFICATION
– DEFINITION
• “Within Cartilage Bone
Formation”
• Method by Which Most Bones
Form
– MECHANISM
• Cartilage Model 
• Periosteum Forms 
• Cells Develop Into
Osteoblasts 
• Secrete Organic Matrix and
Collagenous Fibers
• Calcification Occurs
– *Note: In Both Types of
Ossification:
• Osteoclasts Resorb Bone 
• Forms Medullary Cavity,
Spaces in Cancellous Bone
Bone Growth - Animation
•http://www.anatomy.gla.ac.uk/fab/tutorial/generic/bonet.html
FETAL SKELETON
BONE GROWTH AND RESORPTION
• How Bones Increase in Size after Birth
– FLAT BONES (Also Short, Irregular Bones)
grow by APPOSITIONAL GROWTH
– Growth By Adding to the Surfaces
– LONG BONES grow in length by 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
Epiphyseal Plate
The epiphyseal plate allows for growth
in bones.
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)
• http://www.youtube.c
om/watch?v=6Cn4uu
sbGk8
BONE GROWTH AND RESORPTION
• 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)
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)
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
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
CARTILAGE
• CHARACTERISTICS
– MATRIX
• FIRM/FLEXIBLE GEL
– PROTEIN FIBERS
• COLLAGENOUS
– CELLS
• CHONDROCYTES
• Chondrocytes Lie in
Lacunae
– AVASCULAR: Oxygen
and Nutrients by Diffusion
Similarities and Differences
Bone
f
Cartilage
l
Similarities
and
Differences
Collagen
Bone
Ground substance/matrix
Cells
Protection
Connective tissue
Mitosis (both grow)
Appositional, insterstitial
Lacunae
Osteocytes
Vascular,
Endochondral,
Intermembranous
Hydroxyapatite
matrix
Cartilage
Chondrocytes
Joints,avascular
Gel matrix
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
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