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Skeletal System: Tissue and physiology
Skeletal tissue is the most distinctive form of connective tissue.
Chapter 7 Notes
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 Calciumo Homeostasis of blood calcium levels
Hemopoiesis - blood cell formationoOccurs in red bone marrow
»chest»spinal column in adults»base of skull»upper arm and thigh»In infants or child, all bone marrow
is red.
ADULTS
Bone ShapesBone Shapes
• Long boneLong bone - consists of 6 parts.
Ex. femur, humerus• Short boneShort bone - ex.
Carpals = fingers and toes
• Flat BoneFlat Bone – scapula = back (shoulder blade)
• Irregular boneIrregular 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 fiberous
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
borders.
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. (involves addition of Ca+ and Phosphorous ions)
– 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
http://www.personal.psu.edu/staff/m/b/mbt102/bisci4online/bone/bone5.htm
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
http://www.pennmedicine.org/encyclopedia/em_DisplayAnimation.aspx?gcid=000112&ptid=17
Bone marrow aspiration, direct removal of a small amount (about 1–5 millilitres) of bone marrow by suction through a hollow needle.
Bone Fracture
• Bone Fracture - break in continuity of bone.– Types
•Simple - skin remains unbroken•Compound - broken ends protrude through
skin– Easily infected - osteomyelitis
http://www.muschealth.com/video/Default.aspx?videoId=10226&cId=2&type=rel
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.
• 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.http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter6/animation__osteoporosis.html
http://www.muschealth.com/video/Default.aspx?cId=2
Cartilage
• Cartilage - connective tissue– Types
• Hyaline • Elastic Cartilage• Fibrocartilage
Hyaline
• Most abundant• Semi-transparent-
bluish, 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