Bone Tissue
Bone Markings
 Bulges, depressions, and holes serve
as
– Sites of attachment for muscles, ligaments,
and tendons
– Joint surfaces
– Conduits for blood vessels and nerves
Bone Markings: Projections
 Sites of muscle and ligament attachment
– Tuberosity—rounded projection
– Crest—narrow, prominent ridge
– Trochanter—large, blunt, irregular surface
– Line—narrow ridge of bone
– Tubercle—small rounded projection
– Epicondyle—raised area above a condyle
– Spine—sharp, slender projection
– Process—any bony prominence
Table 6.1
Bone Markings: Projections
 Projections that help to form joints
– Head
• Bony expansion carried on a narrow neck
– Facet
• Smooth, nearly flat articular surface
– Condyle
• Rounded articular projection
– Ramus
• Armlike bar
Table 6.1
Bone Markings: Depressions
and Openings
 Meatus
– Canal-like
passageway
 Sinus
– Cavity within a bone
 Fossa
– Shallow, basinlike
depression
 Groove
– Furrow
 Fissure
– Narrow, slitlike
opening
 Foramen
– Round or oval
opening through a
bone
Table 6.1
Cartilage – Three types
 Hyaline – Most abundant
– Articular cartilages – cover the ends of bones
at moveable joints
– Costal cartilages – connect the ribs and
sternum
– Laryngeal cartilages – for the skeleton of the
larynx (voice box)
– Tracheal and bronchial cartilages – reinforce
the respiratory passages
– Nasal cartilages – support the external nose.
Cartilage
 Elastic – Contains more stretchy elastic
fibers.
– Found in the external ear and form the
epiglottis, the flap that closes on the larynx
when you swallow.
 Fibrocartilage – Rows of chondrocytes and
thick collagen fibers
– Very high tensile strength and compressible.
Found between the vertebral disks, the padlike cartilages of the knee, and the pubic
symphysis.
Cartilage
 Cartilage grows in two ways:
– Appositional growth – growth from the
outside.
– Interstitial growth – growth from within.
Functions of Bones
 Support – Bones give shape and support
to the entire body and provide places for
organs to attach. Allows standing, etc.
 Protection – Cranial bones protect the
brain, vertebrae protect the spinal cord, rib
cage protects the thoracic organs.
 Movement – Skeletal muscles, which are
attached to bone by tendons, use bones to
move the body and its parts.
Functions continued
 Mineral storage - Calcium and
phosphorus are stored in bones and are
constantly being deposited and
withdrawn.
 Blood cell formation – AKA
hematopoiesis occurs in the marrow of
certain bones.
Four Classes of Bone (bases on
shape)
 Long Bones – Longer than they are wide.
Consist of a shaft and 2 ends. All bones
of the limbs are long bones except the
carpals, tarsals, and patella.
 Short Bones – Roughly cube-like. Tarsals
and carpals.
 Flat Bones – Thin, flat, and usually
somewhat curved. Sternum, ribs, scapula,
and cranial bones.
Four Classes of Bone
 Irregular Bones – Bones that don’t fit
any of the previous shapes. Vertebrae
and pelvic bones.
Structure of Bones
 Two layers. The external layer that
appears smooth and solid is compact
bone. Internal to this is the spongy bone.
– Spongy bone is comprised of small, needlelike pieces called trabeculae that form a
honeycomb. The spaces between trabeculae
are filled with red or yellow bone marrow.
– Long bones are primarily compact bone, but
may have a fair amount of spongy bone.
– Flat bones have two parallel layers of
compact bone with a layer of spongy bone
between.
General Structure of Long Bones
 Diaphysis – The shaft or long axis of the
bone. It has a thick collar of compact
bone that surrounds the central medullary
cavity that contains fat (yellow bone
marrow).
 Epiphysis – The ends of the bone
consisting of the distal epiphysis and
proximal epiphysis. The exterior is
compact bone while the interior is spongy
bone. The joint surfaces of each are
covered with a thin layer of articluar
(hyaline) cartilage which absorbs stress
and cushions during movement.
Structure of a Flat Bone
Figure 6.4
Location of Red Bone Marrow
 Red marrow is known as hematopoietic
tissue because it gives rise to blood
cells.
– Typically found within the cavities of
spongy bone.
– In adults, the medullary cavity extends into
the epiphyses, and a little red marrow is
found in most long bones. Blood cell
production is limited to the head of the
femur and humorous.
Location of Red Bone Marrow
– More important are the flat bones
(sternum) and irregular bones (pelvic
bones).
– Yellow marrow can be converted to red
marrow if a person becomes anemic and
needs enhanced Red Blood Cell
production.
Bone Tissue
Pages 3&4 of notes will be on a
WS
Composition of bone tissue
 Bone tissue is composed of 2 types of
tissues
– Organic
– Inorganic
Organic portion:
35% of mass
 The organic portion consists of the bone
cells and the organic matrix
– The Bone cells are the:
•
•
•
•
Osteocytes
Osteoblasts
Osteoclasts
FYI: There are also osteoprogenitor cells that
are the precursers to blasts & cytes. They are
derived from mesenchyme & found on all bone
surfaces.
Blasts, clasts & Cytes
Organic portion
 The Organic Matrix aka. Osteoid
– is produced by the osteoblasts
• Analogy: The organic matrix is the portion that
is deposited first as the “grillwork” or framework
of the bone during the process of
OSTEOGENESIS
• It consists of ground substance and collagen
fibers produced by CT cells
• Its function is to provide the bone with tensile
strength and resilience – in other words, to
make the bone a little flexible
• Review: ground substance, collagen fibers &
EC matrix functions!!
Inorganic matrix:
65% of mass
 The inorganic matrix consists of inorganic salt
compounds mainly:
– Calcium & phosphorus salt compounds
 Its function is to give Strength to the bone
 Analogy: It is formed during
OSTEOGENESIS by the process of
Mineralization
– The inorganic matrix minerals are deposited into
the organic matrix “grillwork”
– The enzyme alkaline phosphatase mediates this
process
Two types of bone
tissue
Know slides, locations, functions
Compact bone tissue (cbt)
 Arranged in OSTEONS aka Haversian
system
 Contains a series of openings that
permit exchange of materials
between osteocytes (& other bone cells)
and the blood.
 Location: look at diagrams
Osteon diagram – cross section
osteocytes
 Lacunae, osteocytes, & canaliculi
Osteon diagram – sagittal section
Cancellous (spongy) bone tissue
 Main structures are the trabeculae
which are needlelike structures of
minerals that are arranged along stress
lines to provide strength
 Materials are exchanged by diffusion
since there are NO canals for passage
 Location: ends of long bones & middle
of flat, short, and irregular bones
Bone marrow
 Aka myeloid tissue
 Yellow bone marrow
– Fat storage
– Found in medullary canal of long bones
 Red bone marrow
– Found in spongy bone (ends of long
bones, flat bones, irregular bones)
– Hematopoiesis (formation of all blood cells)
Types of growth
 Longitudinal growth – bone growth in
length at epiphyseal plates (till plates
ossify)
 Appositional growth – bone growth in
diameter (throughout life)
– Known as remodeling
 These 2 types work together to make
the bones long enough & strong enough
Regulation of bone growth
Bone is a dynamic and active
tissue. They are constantly
being remodeled according to
the activities that we do.
Main factor = Ca levels in blood
Ca imp for bone strength but
also for nervous & muscular
system to work correctly!!!
Regulation by hormonal feedback
 Purpose: to maintain optimal ionic
calcium levels in blood
– This is your body’s TOP priority!!!
 A main factor that affects what our bone
tissue does is our blood calcium level
– Optimum blood Ca 2+ level = 9-11 mg/100 ml of
blood
– Calcium ions are VERY important for muscle &
nervous function – our body cares more about this
level than it does our bone strength!!
Regulation by hormonal
feedback
 PTH (parathyroid gland) – activated when Ca
levels in blood are too low
– (hypocalcemia) - promotes calcium
reabsorption
– Calcium will go from bone to blood
 Calcitonin (thyroid gland) activated when Ca
levels in blood are too high
– (hypercalcemia) - promotes calcium
deposition
– Calcium will go from blood to bone
Regulation by mechanical stress
 Purpose: keep bones strong
–This is the secondary purpose
 Wolff’s law states that bones will
grow according to the stresses
placed upon them
–So activities that compress bones
and pull on muscles which pull on
bones can make bones stronger
How they work together to
regulate
 PTH & calcitonin (hormones) determine
WHEN the remodeling will occur
– Primary purpose = Ca 2+ regulation in
blood
 The Mechanical stresses determine
WHERE the remodeling will occur
– Secondary purpose = where will the
calcium ions be deposited or reabsorbed
from
Fractures &
Disorders
• This section of info will be part
of a lab practical quiz along with
the tissue slides & functions
from earlier in the notes
Instructions
• Construct a chart or other type of
graphic organizer for the 9 types of
fractures
• You will also need to be able to identify
the X-rays or pictures of each.
• See Lab practical slide study on
webpage for quiz review.
Common types of fractures
 1. Comminuted
– Bone breaks into
many fragments
– Common in aged
whose bones are
more brittle (contain
less organic matrix)
Common types of fractures
 2. Compression
– Bone is crushed
– Common on
osteoporotic bones
(or bones that are
porous for other
reasons)
Common types of fractures
 3. Depressed
– Broken bone portion is pressed inward
– Typical of skull fracture
Common types of fractures
 4. Impacted
– Broken bone ends are forced into each
other
– Commonly occurs when one attempts to
break a fall with outstretched arms
– Or when one jumps off something too high
Impacted
Common types of fractures
 5. Spiral
– Ragged break occurs when excessive
twisting forces are applied to a bone
– Common sports fracture
Spiral fractures
Spiral fracture
Common types of fractures
 6. Greenstick
– Bone breaks
incompletely, much
in the way a green
twig breaks
– Common in children
whose bones are
more flexible (more
organic matrix
present)
7. Simple fracture
 Bone does not protrude through skin
8. Compound Fractures
 Bone protrudes through skin
9. Epiphyseal fracture
 Bone shears off at growth plate
 Can cause problems with early
ossification at location of break
Example:Clavicle fracture
Example: Fracture
Example: dislocation
Disorders
Osteoporosis
 Define:
– reabsorption outpaces deposition
– chemical composition remains the same
BUT less total bone mass
– SO bones become more porous & lighter
– Which leads to fractures & deformities from
body weight
 Who is affected?
– Mainly: Aged, post-menopausal women
osteoporosis
 Contributing factors
– Decreased estrogen
– Decreased calcium & protein
– Vitamin D metabolic disorders
– Hormone conditions
– Insufficient exercise
– Immobility
 Treatments
– Replace what is missing
– Medication for metabolic disorders
osteoporosis
Osteomalacia (rickets)
 Define:
– Chemical composition is abnormal (% are
not right)
– Increase in organic matrix – decrease in
inorganic matrix
– Indequate mineralization so bones are too
soft
– Lack of calcium deposition
 Who is affected?
– More severe effects in children since they
are still growingbut primarily a nutritional
disorder
osteomalacia
 Contributing factors:
– Vitamin D &/or calcium deficiency
– Poor nutrition
 Treatments:
– Supplementation
– Sunlight: think about why Vitamin D
deficiency would lead to this disorder!
osteomalacia
Other disorders – add to notes
 Osteomyolitis: inflammation of bone and
muscle
 Gigantism: excess of growth hormone before
epiphyseal plates have ossified
 Acromegaly: excess of growth hormone after
epiphyseal plates have ossified
 Dwarfism: deficit of growth hormone as well
as other factors
 Achondroplasia: most common form of
dwarfism– autosomal dominant but can be
from mutation
gigantism
 Robert Wadlow
 Lots of internal
health problems
including joint
problems
acromegaly
 Epiphyseal plates are sealed so bones
can only grow in diameter/thickness
achondroplasia
 Disproportionate dwarfism
 Normal torso & head
 Short arms & legs
Hypopituitary dwarfism
 More proportionate dwarfism