SKELETAL SYSTEM

- support and protection
- body movement - muscles "pull" on bones
- blood cell formation- hemopoiesis - occurs in red bone marrow
- storage of inorganic salts - calcium, magnesium, sodium, potassium...

Organization

- normally 206 bones with 2 Main Divisions: AXIAL & APPENDICULAR

1. AXIAL: head, neck, trunk

skull, hyoid bone (upper bone anatomyneck, under jaw, mandible), vertebral column (spine/backbone)
thoracic cage (ribs), 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:

1. EPIPHYSIS - 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.

5. MEDULLARY CAVITY - hollow chamber within the diaphysis connects to spaces in spongy bone. Filled with soft specialized tissue called bone marrow.
     ENDOSTEUM - lining of the medullary cavity

- Red Marrow - mainly in spongy bone in adults, produces blood cells
- Yellow Marrow - fat storage

Two Types of Bone Tissue

1. COMPACT (cortical) BONE - wall of the diaphysis, solid, strong
2. SPONGY (cancellous) BONE - epiphysis.

Microscopic Structure

- MATRIX composed of collagen and inorganic salts
- OSTEOCYTES (mature bone cells) are enclosed in tiny chambers called LACUNAE and form concentric rings called LAMELLA
- CANALICULI (canaliculus) connect the osteocytes

HAVERSION CANALS & VOLKMANN'S CANALS provide passageways for blood vessels.

 

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.

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, have a lubricating fluid called SYNOVIAL fluid.

Ball & Socket   | Hinge | Pivot | Saddle

skull

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

 

fontanelSutures - 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


Foramen Magnum - Large opening through the underside of the skull, spinal cord enters skull


The Rest of the Bones

Vertebrae - Cervical | Thoracic | Lumbar

Ribs - Thoracic Cage, 12 pairs
- True Ribs - first seven pairs, attach directly to STERNUM by costal cartilage
- False Ribs - last five pairs (Vertebralchondral)
- Floating ribs - last two pairs (Vertebral)

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

carpalstarsal

 

What About Broken Bones?