Axial skeleton – bones of the skull, vertebral column, and rib cage

80 bones make up the Axial Skeleton

Appendicular skeleton – bones of the upper and lower limbs, shoulder, and hip

126 bones of the Appendicular skeleton

Support – form the framework that supports the body and cradles soft organs

Protection – provide a protective case for the brain, spinal cord, and vital organs

Movement – provide levers for muscles Mineral storage – reservoir for minerals,

especially calcium and phosphorus Blood cell formation – hematopoiesis occurs

within the marrow cavities of bones

Long bones – longer than they are wide (e.g., humerus)

Short bones Cube-shaped bones of the

wrist and ankle Sesamoid- Bones that form

within tendons (e.g., patella)

Flat bones – thin, flattened, and a bit curved (e.g., sternum, and most skull bones)

* Irregular bones – bones with complicated shapes (e.g., vertebrae and hip bones)

General FactsGeneral Facts

a.a. The skull is made of The skull is made of 2222 bones: 8 cranial, 13 bones: 8 cranial, 13 facial, mandiblefacial, mandible

b.b.There are There are 206206 individual bones in an adult. individual bones in an adult. Some are hinged and others are fused to one Some are hinged and others are fused to one anotheranother

c.c. The upper jaw (The upper jaw (maxillaemaxillae) is fused to the cranium. ) is fused to the cranium. The lower jaw ( The lower jaw (mandiblemandible) is moveable.) is moveable.

d.d.The infant skull is incompletely developed and The infant skull is incompletely developed and features features fontanels fontanels or soft spots to aid passage or soft spots to aid passage thru the birth canal and allow for growth of the thru the birth canal and allow for growth of the brain.brain.

General Facts continued. . . General Facts continued. . .

e.e. The vertebrate is made of:The vertebrate is made of:

7 7 cervical cervical vertebraevertebrae

12 12 thoracicthoracic vertebrae vertebrae

5 5 massive lumbarmassive lumbar vertebrae vertebrae

SacrumSacrum, which is a triangular bone made of 5 , which is a triangular bone made of 5 fused bones at the end of the vertebral column.fused bones at the end of the vertebral column.

CoccyxCoccyx, which is made up of 4 fused bones , which is made up of 4 fused bones at the end of the sacrum (tailbone). It is at the end of the sacrum (tailbone). It is immovable in humans, but flexible in cats, dogs, immovable in humans, but flexible in cats, dogs, and monkeysand monkeys

General Facts continued. . . General Facts continued. . .

There are 12 pairs of ribs which attach to the There are 12 pairs of ribs which attach to the sternum thru the sternum thru the thoracic vertebraethoracic vertebrae. .

the first 7 pairs of ribs are true (or the first 7 pairs of ribs are true (or vertebrosternal) ribs that join the sternum directly vertebrosternal) ribs that join the sternum directly by their costal cartilages.by their costal cartilages.

the remaining 5 ribs are false ribs: the first 3 the remaining 5 ribs are false ribs: the first 3 pairs are vertebrochondral ribs and the last 2 pairs pairs are vertebrochondral ribs and the last 2 pairs are floating ribs.are floating ribs.

Bones grow from the growth Bones grow from the growth plates in the plates in the epiphyseal disksepiphyseal disks

Bones grow from the growth plates in the Bones grow from the growth plates in the epiphyseal disksepiphyseal disks

Bones thicken with weight bearing exercise

Lack of exercise leads to bone atrophy

Vitamin D necessary to absorb calcium for bone strength

Vitamin C necessary for collagen Vitamin A necessary for bone growth

Tutorial on Bones of the Skull

Periosteum – double-layered protective membrane Outer fibrous layer is dense regular

connective tissue Inner osteogenic layer is composed of

osteoblasts and osteoclasts Richly supplied with nerve fibers, blood,

and lymphatic vessels, which enter the bone via nutrient foramina

Secured to underlying bone by Sharpey’s fibers

Endosteum – delicate membrane covering internal surfaces of bone

Marrow:-Yellow: Located in the center of the diaphysis in the medullar canal. Made mostly of fat cells, contains many blood vessels, some leukocytes (WBC). Functions as a fat storage center.-Red: Located at the ends of the long bones. Where some erythrocytes (RBC) and WBCs are made.

Compact bone – dense outer layer. Makes up the walls of the diaphysis. Spongy bone – honeycomb of trabeculae filled with yellow bone marrow.

Fills the epiphyses to reduce the weight of the skeleton.

Long bones consist of a diaphysis and an epiphysis Diaphysis

▪ Tubular shaft that forms the axis of long bones

▪ Composed of compact bone that surrounds the medullary cavity

▪ Yellow bone marrow (fat) is contained in the medullary cavity

Epiphyses Expanded ends of long bones Exterior is compact bone, and the

interior is spongy bone Joint surface is covered with articular

(hyaline) cartilage Epiphyseal line separates the diaphysis

from the epiphyses

Osteocytes – mature bone cellsLacunae – small cavities in bone that

contain osteocytesCanaliculi – hairlike canals that

connect lacunae to each other and the central canal

Haversian system, or osteon – the structural unit of compact bone

Lamella – weight-bearing, column-like matrix tubes composed mainly of collagen

Haversian, or central canal – central channel containing blood vessels and nerves

Volkmann’s canals – channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the Haversian canal

Osteoporosis- reduction in bone mineral density which leads to fractures

FracturesCancerScoliosis- curvature of the spineRickets Caused by lack of vitamin D

in childrenBone wasting or atrophy

10 Types of Fractures10 Types of Fractures

1.1. Compression Fracture: bone crushed; common in Compression Fracture: bone crushed; common in the vertebral columnthe vertebral column

2.2. Comminuted fracture: most commonly seen in Comminuted fracture: most commonly seen in the brittle bones of the elderlythe brittle bones of the elderly

3.3. Compound fracture: fracture in which the bone Compound fracture: fracture in which the bone ends penetrate the skinends penetrate the skin

4.4. Closed reduction: non-surgical realignment of Closed reduction: non-surgical realignment of broken bone ends and splinting of the bone.broken bone ends and splinting of the bone.

5.5. Depressed fracture: common fracture of the skull Depressed fracture: common fracture of the skull in which the bones become concavein which the bones become concave

10 Types of Fractures (cont.)10 Types of Fractures (cont.)

6.6. Simple fracture: bone is cleanly broken and does Simple fracture: bone is cleanly broken and does not penetrate the skin; commonly called a closed not penetrate the skin; commonly called a closed fracturefracture

7.7. Impacted fracture: fracture in which the broken Impacted fracture: fracture in which the broken ends are pushed into each otherends are pushed into each other

8.8. Open fracture: fracture that required surgical Open fracture: fracture that required surgical realignment of the broken bone endsrealignment of the broken bone ends

9.9. Greenstick fracture: common in children; bone Greenstick fracture: common in children; bone splinters but doesn’t break completely; splinters but doesn’t break completely; sometimes referred to as a “hairline” fracturesometimes referred to as a “hairline” fracture

10.10.Spiral fracture: bone breaks due to twisting Spiral fracture: bone breaks due to twisting forces: common in sports injuriesforces: common in sports injuries

Closed reduction

compound

Open reduction

Impacted

Impacted