SKELETAL SYSTEM



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

- 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:

EPIPHYSIS – expanded ends of bone. ARTICULATES (forms a joint) with another bone.

DIAPHYSIS – shaft of the bone

ARTICULAR CARTILAGE – hyaline cartilage covering the ends of bones

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

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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. ENCHONDRAL BONES = all other bones.

[pic] 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.

[pic]As long as growth is occurring, a “band” of cartilage (called an epiphyseal disk, growth plate) remains between the diaphysis and the epiphysis.

[pic]Bones increase in length as these cartilage cells continue to reproduce and ossify

[pic]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

[pic]Growth in thickness of bone occurs as osteoblasts from beneath the periosteum produce bone matrix and built compact bone just underneath the periosteum

[pic]Bone tissue is constantly being 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

2. AMPHIARTHOTIC – slightly moveable joint, vertebrae

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.

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. Mandilbe – lower jaws, only moveable bone of the skull

Sutures

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, see page 138

- 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

Ribs – Thoracic Cage, 12 pairs

- True Ribs – first seven pairs, attach directly to STERNUM by costal cartilage

- False Ribs – last five pairs

- Floating ribs – last two pairs

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 carpels

Fingers – Metacarpels, 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

What About Broken Bones?

• 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.

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Scared Lovers Try Positions That They Can't Handle.

SKELETON LABELING

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