SKELETAL SYSTEM Information
- The bones of your skeleton are made up of OSSEUS TISSUE.
- Bone tissue is a type of connective tissue. Your skeleton performs several important functions.
•
•
•
•
support and protection
body movement - muscles "pull" on bones
blood cell formation- “hemopoiesis ' occurs in red bone marrow
storage of inorganic salts - especially calcium phosphate, but also magnesium, sodium,
potassium, carbonates and others
Organization
- Adults normally have 206 bones (infants around 300) with 2 Main Divisions: AXIAL &
APPENDICULAR
1. AXIAL: head, neck, trunk
skull, hyoid bone (upper neck, under jaw, mandible)
vertebral column (spine/backbone)
thoracic cage (rib cage-12 pairs)
sternum
2. APPENDICULAR: limbs and bones connecting the limbs to the:
pectoral girdle (scapula & clavicle), UPPER LIMBS (arms)
pelvic girdle (coxal bones), LOWER LIMBS (legs)
BONE STRUCTURE:
"LONG BONE" = typical bone
Major parts:
1. EPIPHYSIS - expanded ends of bone. ARTICULATES
(forms a joint) with another bone.
2. DIAPHYSIS - shaft of the bone
3. ARTICULAR CARTILAGE - hyaline cartilage covering
the ends of bones
4. PERIOSTEUM - tough membrane-like covering over
entire bone, except for articular cartilage. Connects with
tendons and ligaments. Forms bone tissue.
**tendons connect bone to muscle while ligaments connect
bone to bone
5.MEDULLARY CAVITY - hollow chamber within the
diaphysis connects to spaces in spongy bone. Filled with
soft specialized tissue called bone marrow.
• " Red Marrow” - mainly in spongy bone in adults. Produces blood cells
• " Yellow Marrow” - fat storage.
6. ENDOSTEUM - lining of the medullary cavity
Two Types of Bone Tissue
1. COMPACT (cortical) BONE - wall of the diaphysis in long bones; solid, strong
2. SPONGY (cancellous) BONE – epiphysis of long bones. Covered with a thin layer of compact
bone. Many branching, bony "plates"
Microscopic Structure
-MATRIX composed of collagen and inorganic salts
- OSTEOCYTES (mature bone cells) are enclosed in tiny chambers called LACUNAE and
form concentric "ring" (layers) around a passageway called the HAVERSION CANAL
- The osteocytes are connected by minute passages called CANALICULI (canaliculus)
through which tiny "branches" or processes pass
- The circular layers of matrix material and osteocytes, along with the haversian canal,
forms a unit called a HAVERSIAN SYSTEM. Compact bone tissue is formed in this way
- The haversian canals are interconnected by passages called VOLKMANN'S CANALS. All
of these canals contain blood vessels and nerve fibers
Bone Development and Growth:
There are two types of bone based on the way the bones form
1. Intramembranous bones = broad, flat bones of the skull. These bones form from
membrane-like sheets of connective tissue
2. Endochondral bones = all other bones.
•
•
•
•
•
•
Bones first form as hyaline cartilage. The cartilage then gradually changes into bone tissue a process called OSSIFICATION, which begins near the middle of the diaphysis in an area
called the PRIMARY OSSIFICATION CENTER. Later the bone begins to ossify in the
epiphysis - these areas are called the SECONDARY OSSIFICATION CENTERS.
As long as growth is occurring, a "band" of cartilage (called an epiphyseal disk; aka:
growth plate) remains between the diaphysis and the epiphysis.
Bones increase in length as these cartilage cells continue to reproduce and ossify
Cartilage cells form cells called OSTEOBLASTS. These cells produce bone matrix and
once the cell is enclosed in bone matrix it is considered to be a mature bone cell and called
an OSTEOCYTE
Growth in thickness of bone occurs as osteoblasts from beneath the periosteum produce
bone matrix and build compact bone just underneath the periosteum
Bone tissue is constantly replaced as special cells called OSTEOCLASTS dissolve bone
tissue from within the medullary cavity - a process called RESORPTION. At the same time
new bone tissue is being added to the outside of the bone.
3 Basic Types of Joints (articulations):
1. SYNARTHROTIC - immoveable joint, such as bones in the skull, these junctions are called
SUTURES. - Fibrous Joints
2. AMPHIARTHROTIC - slightly moveable joint, vertebrae - Cartilaginous Joints
3. DIARTHROTIC - freely moveable joint, such as shoulders, hips, knees, elbows, wrists, fingers…
--these joints are enclosed within a fibrous capsule which contains a lubricating fluid called
SYNOVIAL fluid. These are called SYNOVIAL JOINTS.
Ball & Socket
Hinge
Pivot
Saddle
Gliding
Bones of the Skull
1. Frontal - anterior portion above eyes
2. Parietal - one on each side of the skull, just behind frontal bone
3. Occipital - forms the back of the skull and base of the cranium
4. Temporal - forms parts of the sides and base of cranium
5. Sphenoid - wedged between several other bones in anterior portion of the cranium
6. Maxilla - forms upper jaws
7. Mandible - lower jaws, only moveable bone of the skull
Sutures - connection points between skull bones
1. Coronal - between frontal and parietal bones
2. Lambdoidal - between occipital and parietal bones
3. Squamosal - between temporal and parietal bones
4. Sagittal - between parietal bones
Fontanels - "soft spots" of an infant's skull, these form sutures as you age
- anterior fontanel, posterior fontanel, sphenoid fontanel, mastoid fontanel
The Rest of the Bones
Ribs - Thoracic Cage, 12 pairs
- True Ribs - first seven pairs (attach directly to STERNUM by costal cartilage)
- False Ribs - last five pairs (attach to the sternum indirectly through the cartilage of the 7th
vertebrae)
- Floating ribs - last two pairs (connected to vertebrae only, not sternum)
Pectoral Girdle: Shoulder. Two clavicles (collar bones) and two scapula (shoulder blade)
Arms: Upper arm - humerus. Lower arm - radius and ulna.
Wrist - 8 small bones called carpals
Fingers - Metacarpals, Phalanges
Pelvic Girdle: Hips. Two large bones called COXAL BONES
Legs: Upper leg (thigh) - FEMUR. Lower leg - tibia & fibula.
Ankle and Upper foot - 7 bones called TARSALS,
Largest is the heel bone called the CALCANEOUS
Toes - Metatarsals, Phalanges
There are 54 bones alone in your wrists and hands!!
Vertebral Column
32 bones
What About Broken Bones?
Fractures
•
•
•
•
•
•
•
•
•
•
A complete fracture
A greenstick fracture
A comminuted (say: kah-muh-noot-ed)
A bowing fracture
An compound/open fracture
A spiral fracture
An oblique fracture
A transverse fracture
An avulsed fracture
A fissured fracture
ABNORMALITIES OF THE SKELETAL SYSTEM
1. OSTEOSARCOMA
2. TENDONITIS
3. SPRAINS/STRAINS
4. LEUKEMIA
5. RHEUMATOID ARTHRITIS
6. OSTEOARTHRITIS
7. OSTEOPOROSIS
8. OSTEOGENESIS IMPERFECTA
9. SPINA BIFIDA
10. PAGETS DISEASE
11. RICKETS
12. SCOLIOSIS
13. KYPHOSIS
14. LORDOSIS
15. ANKYLOSIS
16. OSTEOMALACIA
17. CLUBFOOT
18. ACHONDROPLASIA