Bones & Skeletal
(Osseous) Tissues
Functions of Bones
 Support – hard framework
that supports body & cradles
soft organs
 Protection – fused bones of
skull, vertebrae, rib cage
 Movement – skeletal muscles
use bones as levers
 Mineral Storage – calcium &
phosphate
 Blood Cell Formation
(hematopoiesis) – RBC & WBC
forms within red marrow
cavities of certain bones
Classification of Bones
 All bones contain external compact bone & internal
spongy bone filled with red or yellow bone marrow
Classification of Bones
 Classified according to shape:
– Long Bones – has a shaft & 2 ends; made mostly
of compact bone but may contain spongy bone in
its interior
• Ex. Femur, tibia, fibula, humerus, fingers of hand
– Short Bones – cube-like & contain mostly spongy
bone; compact bone provides thin surface layer
• Ex. Bones of carpus (wrist) & tarsus (ankle)
– Flat Bones – thin, flattened & usually a bit curved;
have 2 relatively parallel compact bone surfaces
• Ex. Sternum, ribs, skull
– Irregular Bones – bones that do not fit above
classification
• Ex. Vertebrae & os coxa (pelvis)
– Sutural Bones – small, flat, irregular shaped
bones of skull
– Sesamoid Bones – small, flat, shaped like sesame
seed; develop in tendons located near joints
• Ex. Knee cap
Why is Bone
considered an Organ?
 Bones are organs
(organ level of
organization) because
they contain different
types of tissue
– Osseous
– Nervous
– Blood
– Cartilage
Anatomy of Long Bones
 Diaphysis (shaft) – composed of a thick collar of
compact bone that surrounds a central medullary cavity
(marrow cavity)
– “dia” – passing through
 Epiphyses – bone ends
– Exterior made up of
compact bone
– Interior is spongy bone
• Why are the exterior &
interior regions of the
epiphyses structured
this way?
– Joint surface of each
epiphysis is covered with
thin layer of articular cartilage (cushion)
– “epi” – on top of
Anatomy of Long Bones
 Periosteum – outer surface of diaphysis
– Richly supplied with nerve fibers & blood vessels
 Endosteum – a delicate covering of internal bone
structures
– Why are there 2
wrappings found
within long bone
structure?
Anatomy of Short,
Irregular & Flat Bones
 Thin plates of
periosteumcovered compact
bone on outside
 Endosteumcovered spongy
bone (called
diploe in flat
bones) on inside
Hematopoetic Tissue
in Bones
 Hematopoeisis: formation of blood
cells
– “hema” – blood
– “poiesis” – production or formation of
 Infants
– Medullary cavity & all spongy bone
contain red marrow
 Adults
– Diaphysis is usually filled with fatty
(adipose) yellow marrow
– Majority of hematopoiesis in long bones
occurs in head of the femur & humerus
 Most important blood production occurs
in diploe of flat bones (sternum) & in
some irregular bones (hip bone)
Bone
Histology
Now what level of
organization are
we talking about?
 Bone contains
specialized cells & a
solid, sturdy matrix
(calcium salts deposited
around collagen protein
fibers)
 Osteocytes: mature bone
cells that occupy a lacuna
– “osteo” – bone
– “cyte” - cell
Bone Histology
 Bone cells are arranged in
cylindrical patterns
throughout bone around
thin tubes called
Haversian canals that
contain nerves & blood
vessels that nourish the
osteocytes.
 Tiny cytoplasmic extensions
called canaliculi connect
the osteocytes to one
another & the Haversian
canals.
Functions of Osteocytes
 Maintain the
protein & mineral
content of the
matrix
– Secrete chemicals that
dissolve old matrix &
then stimulate the
depositing of calcium
crystals
 Assist in the repair
of damaged bone
– If released from
lacunae, osteocytes
can become an
osteoblast or an
osteoprogenitor cell
Osteoprogenitor
Cells
 Stem cells that undergo
mitosis, producing
daughter cells that
differentiate into
osteoblasts
– Aid in repair
of bone
fractures
– Located in
the
endosteum
(which lines
marrow
cavities)
Osteoblasts
 Perform
osteogenesis
– Make & release
proteins & other
parts of matrix
– Before calcium salts
are deposited the
matrix is called
osteoid
– Osteoblasts elevate
the level of calcium
salts in matrix, thus
converting osteoid
to bone
Osteoclasts
 Cells that break
down bone matrix
 Large cells with
approximately 50
nuclei
 Dissolve matrix
by secreting
acids & certain
enzymes
 Dissolved
minerals are
reabsorbed in a
process called
osteolysis
– “lysis” – loosen
or dissolve
Osteoblast-OsteoclastOsteoprogenitor
Relationship
Osteoblast-Osteoclast
Relationship
 Osteoclasts are constantly destroying bone
matrix & osteoblasts are always adding it
– Remember…osteoblasts = building bone
– Remember…osteoclasts = crush bone
 When osteoclasts remove calcium salts
faster than osteoblasts deposit them, bones
weaken
 The converse is also true
– Stress body through exercise = strengthen muscle &
bones
– Declining muscular activity = reduction of bone mass
at sites of muscle attachment
Bone Formation &
Growth
 Begins to form 6
weeks after
fertilization
– It is cartilaginous
 Ossification occurs
– Process by which
cartilage is replaced by
bone
Types of Cartilage
 Hyaline cartilage:
– translucent matrix
– no prominent fibers
• Reduces friction in joints
 Elastic cartilage:
– tightly packed elastic fibers
• Flexible support
 Fibrocartilage:
– very dense collagen fibers
• Resists compression
Bone Remodeling
 Throughout adult life osteocytes, osteoclasts &
osteoblasts remain active
 In young adults, 1/5 of the adult skeleton is
recycled & replaced each year
 Regular exercise is essential in maintaining
normal bone structure
Bone Fractures
 Fractures are
cracks or breaks in
bone
 Most heal if
components of
blood supply survive
 Due to
– Extreme loads
– Sudden impacts
– Stresses from
unusual directions
Bone Repair Process
Bone Repair Process
Examples of Fractures
Examples of Fractures
Effects of Hormones
(Endocrine System) on Bone
 Relationship between the Endocrine & Skeletal
Systems
– Calcitriol: essential for normal Ca & P ion absorption
– Hormone GH (growth hormone): increases rate of mitosis of
chondrocytes & osteoblasts, increases rate of protein
synthesis (collagen & cartilage for cartilage & bone
formation)
– Parathyroid hormone: increases reabsorption of calcium
from bones to the blood, raises blood Ca levels & increases
absorption of Ca by small intestine & kidneys
– Calcitonin: decreases the reabsorption of Ca from bones,
lowering blood Ca levels
– Estrogen or Testosterone: promotes closure of epiphyses of
long bones (stops growth) & helps retain Ca in bones
(maintaining strong bone matrix)
Effects of Nutrition on Bone
 Body needs constant dietary supply of calcium,
phosphate salts, magnesium, fluoride, iron &
manganese
 Vitamin A stimulates osteoblast
activity
 Vitamin C stimulates osteoblast
development
 Lack results in scurvy, a loss of bone mass & strength
 Vitamins K & B12 make proteins (collagen) in bone
Effects of
Nutrition on Bone
 Vitamin D helps integrate Ca in
bone tissue
– If we do not replace Ca & P ions lost each
day in urine, these ions will be released
from bones
• Makes bones weaker
– Rickets (a form of osteomalacia)
caused by inadequate exposure to
sunlight
• Bones become flexible & bow out
 Ca is most abundant mineral in
body
– Helps bone growth
– Neuromuscular activity
 Make sure you READ the directions
& FOLLOW them CAREFULLY!
 You MUST wear your SAFETY EQUIPMENT!
– Acetic acid??? Chemical formula?
• CH3COOH
– Sodium oxalate??? Formula?
• Na2C2O4
 Answer all the Follow-Up
Questions after each Part.
 Clean your LAB STATIONS!
INTRODUCTION: What makes bones
strong?
Some say you should drink milk when your bones are
developing. Is this logical?

Using your knowledge of osseous tissue, perform the following
lab & answer the Conclusion & Application questions.
PART ONE: GOGGLES ARE REQUIRED FOR THIS LAB!!
1.
2.
Take an uncooked chicken bone & break it in half.
Take one side & pour the contents of the marrow cavity onto a slide
and create a wet mount using bromothymol blue dye (make sure the
slide contents are VERY thin!).
3. Look at the wet mount under the microscope using medium and/or
high power. DRAW WHAT YOU SEE (using your correct format for
microscope drawings) & label properly.
ANSWER the FOLLOW-UP QUESTIONS
PART TWO:
1. Take one half of the chicken bone & break it in half
again.
2. Place one half of the new broken bone into a test
tube containing distilled water & the remaining
half place into a test tube of acetic acid (vinegar).
3. Using masking tape & a pen, identify each test tube
as ACID & WATER.
4. Place the test tubes into a holder for 24-48 hours.
MAKE A PREDICTION: What do you think the effect
of each liquid will be on the bones?
The End
PART THREE: PUT YOUR GOGGLES
ON!!!
Must be completed 24-48 hours after Part Two!
1. Mark two clean test tubes as ACID & WATER
with a piece of masking tape & a pen.
2. Remove 3-4 milliliters of solution from each test
tube into the correct clean test tube. DO NOT
USE THE SAME PIPET FOR EACH TUBE!!!
3. Add 2-3 drops of 1% sodium oxalate into each of
the NEW test tubes filled with solution. Watch
what happens…DESCRIBE IT!
ANSWER the FOLLOW-UP QUESTIONS.
PART FOUR: POSITIVE CONTROL
TEST
1.
2.
3.
4.
Add 1.5 grams of calcium carbonate powder into a
beaker.
Add 6 ml of acetic acid, stir well allowing the gas to
evolve. Let any remaining solid settle to the bottom.
Filter the top portion of the liquid located in the beaker
into a clean test tube. This solution should be CLEAR.
Add 3 drops of 1% sodium oxalate solution to the
test tube of filtered liquid.
ANSWER the FOLLOW-UP QUESTIONS.
PART FIVE: Hardness, Color,
Texture Tests
1.
2.
3.
4.
Using a set of tweezers, extract each of the bones,
wash them off & check for hardness, using the
tweezers. WRITE DOWN YOUR OBSERVATIONS.
Using the magnifying glass, observe the color &
texture of the bones. WRITE DOWN YOUR
OBSERVATIONS.
Place the bones back into their original solutions &
store in the classroom for another 24-48 hours. You
may need to add more vinegar or water to your test
tubes.
REPEAT steps 1-2 after the 24-48 hour period is up.
ANSWER the FOLLOW-UP QUESTIONS.
The End
 Title Page
– Title of lab, Name, Date & Period
 Data & Observations
Part 1: Bone Marrow Extraction
Label the layers of the bone cross-section & the contents
found within each regions.
Part 2 & 5: Acid & Water Bones
Draw & label your Acid & Water beaker set-up.
Describe, compare & contrast the observations made for
hardness, color & texture of the bones in each beaker &
before & after letting them soak.
Part 4: Positive Control Test
Draw & label your Positive Control Test set-up.
Include necessary chemicals (include formula) & precipitate
found.
 Conclusions & Applications
– In paragraph format, answer the following
Conclusion & Application questions.
1. State your prediction for the experiment. Was it supported or
not? Explain.
2. What makes bones strong? Some say you should drink milk
when your bones are developing. Is this logical? Explain your
answer using ideas investigated in this lab.
3. What is a positive control test & why is such a test performed?
Describe the precipitate found at the bottom of the test tube.
Why was it there? What did its presence confirm?
Conclusion & Application
Questions (cont)
4. What is typical/healthy pH of blood? Is this acidic or basic?
Why is blood pH important to understand when talking about
the health of bone tissue?
5. Think about one of the most common staples of the American
diet – soda. What is the pH of soda? Is it acidic or basic?
What in the soda gives it this pH?
6. What effect could drinking a high quantity soda each day
have on the health of bone? What is the chemical reaction
that takes place? Explain your answer using examples from
this lab.
7. What other body parts are made from/of a high proportion of
calcium? Describe one other application of this lab to another
part of the body other than bone.