Chapter 7 Notes
Skeletal System: Tissue and
physiology
Skeletal tissue is the most
distinctive form of
connective tissue.
Functions of Skeletal Tissue
 Support
• Ex. Arch of foot, vertebral column,
etc.
 Protection
• Ex. Skull protects the brain, rib cage
protects lungs and heart.
 Movement
• Occurs with the help of joints - act as
levers
• Muscle contraction pulls on bones =
movement
Functions of Skeletal Tissue
 Mineral reservoir
o Calcium
o Homeostasis of blood calcium levels
Hemopoiesis - blood cell formation
o Occurs in red bone marrow
»chest
»spinal column in adults
ADULTS
»base of skull
»upper arm and thigh
»In infants or child, all bone marrow is
red.
Bone Shapes
• Long bone - consists of
6 parts.
Ex. femur, humerus
• Short bone - ex.
Carpals = fingers and
toes
• Flat Bone – scapula =
back (shoulder blade)
• Irregular bone vertebrae
Structure of Long Bone
• Diaphysis
– Main shaft
– Strong support
– Hollow = decrease
in weight
Structure of Long Bone
• Epiphysis
– Ends of long bone
– Bulbous shape allows
for muscle
attachment and gives
stability to joints
– Contains spongy
tissue
• contains marrow - red
or yellow
Spongy
bone
Compact
bone
Structure of Long Bone
• Articular cartilage
– Covers joint surface
of epiphysis
– Cushions jars and
blows
Structure of Long Bone
• Periosteum
– Dense fibrous
membrane
– Covers bone except at
joints
– Tedons interlace with
and anchor muscles
– Contain many blood
vessels (connects with
haversian canal)
– Osteoblasts (bone
forming cells) compose
inner layer
Structure of Long Bone
• Medullary Canal
– Tube of diaphysis
– Contains marrow
• Endosteum
– Membrane
– Lines medullary
cavity of long bone
Long Bone Anatomy
http://kidshealth.org/misc/movie/bodybasics/bone.html
Haversian System
• Identifies microscopic structure
of compact bone in the diaphysis
Haversian System Structure
• Lamellae (Lah-Mel-e)
– cylinder shaped layers
of calcified matrix
(non-living)
• Lacunae (la-Kew-nah)
– small spaces
– contains tissue fluid
where bone cells
(osteocytes) live
– imprisoned between
lamellae
Haversian System Structure
• Canaliculi
(Ka-NALi-ku-li)
– ultra small canals
– radiates out from lacunae
to connect each other
– connects also to haversian
canal
• Haversian canal
– Contains blood vessels and
lymphatic tissue
– Gives nutrients to lacunae
through canaliculi
– Gives nutrients to
osteocytes
Haversian System
Bone Development and Growth
• Osteogenesis - the
process of bone
formation
– At 12 weeks the
skeleton has
formed-made of
cartilage and
fibrous tissue.
Bone Development and Growth
• Fontanels - "soft
spots" of an
infant's skull
Osteogensis
• Intramembranous Development
– Prebone structure of skull and mandible
– Takes place within connective tissue
– Connective tissue enlarges to form osteoblasts
- bone forming cells.
– Bone matrix is formed
– Matrix is calcified by deposits of calcium and
salts.
– Flat bones grow by adding to their outside
boarders.
Osteogensis Continued
• Endochondral (all other bones)
– Begin as cartilage
– Cartilage develops periosteum - enlarges into a
ring
– Cartilage calcifies
– Ossification, hardening of bone, progresses
toward each epiphysis.
– During bone growth, ephiphyseal cartilage
remains between ends and shaft = growth plate.
Osteogensis Continued
Major stages (a-d fetal, e child, f adult) in the
development of the endochondral bone.
Bone Growth
• Diameter
– Osteoclasts - enlarge diameter of
medullary cavity by eating away wall.
– Osteoblasts - build new bone at
periosteum
– Occurs throughout life
Bone Growth Continued
• Childhood
– Bone ossification is greater than bone
resorption (decomposition) = taller
• Adulthood
– Bone ossification and resorption equal one
another.
– At 35-40, bone ossification decreases and
resorption is greater.
• Become hollow
• Vertebrae collapse = height decrease
• Brittle bones = death
Bone Growth
Bone Fracture
• Bone Fracture - break in continuity
of bone.
– Types
• Simple - skin remains unbroken
• Compound - broken ends protrude through
skin
– Easily infected - osteomyelitis
Bone Fractures Continued
• A complete fracture is when the bone has broken
into two pieces.
• A greenstick fracture is when the bone cracks on
one side only, not all the way through (occurs in
children).
• A single fracture is when the bone is broken in
one place.
• A comminuted (say: kah-muh-noot-ed) fracture is
when the bone is broken into more than two pieces
or crushed.
• A bowing fracture, which only happens in kids, is
when the bone bends, but doesn't break
• An open fracture is when the bone is sticking
through the skin.
Bone Fractures Continued
Bone Fractures Continued
• Repair - fracture healing
– Damage to blood vessels begins repair sequence.
– Dead bone is removed by osteoclasts-resorption.
– Osteoclasts used as framework for repair tissue
called callus.
– Callus tissue bonds broken ends of bone outside.
– Callus tissue binds medullary cavity.
– Callus tissue is molded and replaced with bone.
• Electrically induced osteogenesis - uses electrical
stimuli to heal fractures.
Bone Fractures Continued
• Major steps
in the repair
of a
fracture.
Osteoporosis
• Loss of calcified matrix & callogenous fibers.
• Occurs most frequently in elderly, white females.
• Decrease levels of estrogen and testosterone.
– Decreased osteoblast activity
– Decreased maintenance of existing bone
• Bone Degeneration
– Spontaneous fractures
– Curvature of the spine
• Treatment
– Estrogen therapy - after menopause
– Dietary supplement of calcium and vitamin D.
Cartilage
• Cartilage - connective tissue
– Types
• Hyaline
• Elastic Cartilage
• Fibrocartilage
Hyaline
• Most abundant
• Semi-transparentbluish, opalescent
• Covers articular
surface of bone
• Forms ends of ribs
that join to sternum
• Forms rings in trachea,
bronchi of lungs, &
nose
Elastic Cartilage
• Elasticity and
firmness
• Fibers form to
external ear,
epiglottis, tubes in
ear, nasal cavity
• Yellowish in color
Fibrocartilage
• Greatest tensile
strength
• Intervertebral
disks, point of
attachment of
some large tendons
to bones.
Structure of Cartilage
• Chondrocytes - cartilage cells.
• Avascular - contain no blood vessels.
– Receive oxygen and nutrients through diffusion.
• Increase of collagenous fibers and matrix
embedded in a gel (not calcified).
Function of Cartilage
• Shock absorption
• Resists collapse of passageways
• Allows bone growth