SKELETAL SYSTEM

- the bones of your skeleton. 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

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

skull

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)

boneBONE 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.


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. Replaces much of the red marrow in diaphysis through childhood

ENDOSTEUM - lining of the medullary cavity

 

Two Types of Bone Tissue

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

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

skullBones 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

fontanel

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


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 (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?