1. The Skeletal System
AP Biology

2. Divisions of the Skeletal System
Subdivided into two divisions:
Axial Skeleton – bones that form the longitudinal axis of the body
Appendicular Skeleton – bones of the limbs and girdles
Skeletal system also includes joints, cartilages, and ligaments
The joints give the body flexibility and allow for movement.

3. Functions of Bones Support Protection
Internal framework, support and anchor soft organs
Bones of legs act as pillars to support body trunk
Rib cage supports the throacic wall
Protection
Bones protect soft body organs
Ex. The skull protects the brain
Ex. The vertebrae surround the spinal cord.

4. Functions of Bones Movement Storage
Skeletal muscles use the bones as levers to move the body.
Remember – skeletal muscles are attached to the bones by tendons.
Storage
Fat is stored in internal cavities of bones.
Bones store minerals, most importantly
Calcium – important to muscles, nerves, and blood
Phosphorous

5. Functions of Bones Blood Cell Formation
Hematopoiesis = blood cell formation
Occurs within the marrow of certain bones

6. Classification of Bones
The adult skeleton is composed of 206 bones.
2 types of bone tissue:
Compact bone – dense and looks smooth
Spongy bone – composed of needlelike pieces of bone and lots of open space

7. Classification of Bones
Bones are classified according to shape into 4 groups: long, short, flat, irregular
Long: longer than they are wide, mostly compact bone
Short: cube-shaped, mostly spongy bone
Flat: thin, flattened, and usually curved, 2 thin layers of compact bone and a layer of spongy bone in middle
most bones of the skull, ribs, and sternum
Irregular: the vertebrae and the hip bones

8. Structure of a Long Bone
The diaphysis makes up most of the bone’s length, composed of compact bone.
Covered by a protective connective tissue membrane called the periosteum
The epiphyses are the ends of the long bone.
Mostly spongy bone
Cartilage covers this part of the bone.
Provides a smooth, slippery surface that lubricates the joints.

9. Structure of Bone
Epiphyseal line – thin line of bony tissue on epiphysis
Remnant of the epiphyseal plate
Causes the lengthwise growth of a long bone.
By the end of puberty, bones stop growing and epiphyseal plates are completely replaced by bone.
Mark the previous location of epiphyseal plate
Interactive Web

10. Structure of Bone
In adults, the cavity in the shaft of the bone stores adipose tissue (fat).
Yellow Marrow
In infants, this area forms blood cells, and red marrow is found there.
In adults, red marrow is only found in the cavities of spongy bone of flat bones and some long bones.

11. Bone Markings Bumps, ridges, and holes in bones.
Indicate where muscles, tendons, and ligaments attach, and where blood vessels and nerves passed.
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12. Axial Skeleton head, neck, trunk SKULL
HYOID BONE (upper neck, under jaw, mandible)
VERTEBRAL COLUMN (spine/backbone)
THORACIC CAGE (rib cage-12 pairs)
STERNUM

13. Appendicular Skeleton
limbs and bones connecting the limbs to the:
PECTORAL GIRDLE (scapula & clavicle)
UPPER LIMBS (arms)
PELVIC GIRDLE (coxal bones)
LOWER LIMBS (legs)

14. Microscopic Structure of Bone
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 small passages called CANALICULI (canaliculus) through which tiny “branches” or processes pass

16. Microscopic Structure of Bone
The circular layers of matrix material and osteocytes, along with the haversian canal, forms a unit called a HAVERSIAN SYSTEM.
The haversian canals are interconnected by passages called VOLKMANN’S CANALS.
All of these canals contain blood vessels and nerve fibers

18. 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

20. Vertebral Column 3 types of vertebrae:
Cervical: First 7 (neck)
Thoracic: 12 vertebrae
Lumbar: Last 5 (lower back)
Intervertebral disks: flexible cartilage, cushion vertebrae and absorb shock
Sacrum: fusion of 5 vertebrae
Coccyx: fusion of 3-5 small, irregularly shaped vertebrae.
“tailbone”

21. Bones Ribs – Thoracic Cage, 12 pairs Pectoral Girdle: Shoulder.
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)

22. Bones 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

23. Broken Bones
A simple fracture is when the bone is broken cleanly but does not penetrate the skin.
A compound/open fracture is when the bone is sticking through the skin.
A greenstick fracture is when the bone cracks on one side only, not all the way through.
A comminuted (say: kah-muh-noot-ed) fracture is when the bone is broken into many fragments or crushed.
A compression fracture is when the bone is crushed.
A depressed fracture is when the bone is broken and pressed inward (typical of skull fracture).
A spiral fracture is when a break occurs from excessive twisting forces applied to the bone.