The Skeletal SystemChapter 5

The Skeletal System Parts of the skeletal system

Bones

Joints

Cartilage

Ligaments

Divided into two divisions

Axial Skeleton – torso and head

Appendicular Skeleton - limbs

Functions of the Bones

Support of the body

Protection of the soft organs

Movement due to attached skeletal muscles

Storage of Minerals and fats

Blood cell formation

Bones of the Human Body The skeleton has 206 bones

Two basic types of bone tissue Compact bone

Homogeneous Very dense and strong

Spongy bone Small needle-like

pieces of bone Many open spaces Purpose?

Figure 5.2b

Classification of Bones• Long Bones

• Description? Examples?

• Short Bones• Description? Examples?

• Flat bones• Description? Examples?

• Irregular Bones• Irregular shapes• Do not fit into any other bone classification

category• Examples?

Classification of Bones on the Basis of Shape

Figure 5.1

Gross Anatomy of a Long Bone

Diaphysis

Shaft of the bone

Composed primarily of _________ bone

Epiphysis

Ends of the bone

Composed primarily of _________ bone

Figure 5.2a

Structures of a Long Bone

Periosteum Outside covering of

the diaphysis

“Skin of the bone”

Vascular

Meaning?

Multiple functions

Sharpey’s fibers Secure periosteum to

underlying boneFigure 5.2c

Structures of a Long Bone

Articular cartilage

Covers external surfaces of epiphysis

Hyaline cartilage

Function?

Figure 5.2a

Structures of a Long Bone

Medullary cavity

Cavity of the shaft

Contains yellow marrow (mostly fat) in adults

Contains red marrow (for blood cell formation) in infants Figure 5.2a

Structures of Long Bone

Process – Projection from the bone

Purposes

Site of attachments for muscles

Create joints

Pathway for nerves, blood vessels

Microscopic Anatomy of Bone

Osteon (Haversian System) Bone is built around a “canal” Tube-like openings in the bone

DQ - What would these canals be used for?

Two types of Canals Central (Haversian) canal

Run longitudinally in the bode Perforating (Volkman’s) canal

Perpendicular to the Haversian Canal

Microscopic Anatomy of Bone

Figure 5.3

Microscopic Anatomy of Bone

Lacunae Tiny cavities

containing osteocytes (bone cells)

Lamellae Rings around the

central canal

Sites of lacunae

Figure 5.3

Microscopic Anatomy of Bone

Canaliculi

Tiny canals

Radiate from the central canal to lacunae

Not the same as Volkmann’s canal

Purpose = diffusionFigure 5.3

Bone Cells

3 Types of Bone cells

Osteocytes - Mature bone cell

Osteoblast – Bone forming cell

Osteoclast – Bone Destroying cell

Break down bone matrix for remodeling and release of calcium

Skeletal Functions

• Support and Protection:• Bones create the shape of our body

• Examples?• Bones provide a hard protective barrier

around vital organs• Examples?

• Movement:• Muscles attach to the bones across

joints• Work like levers

Skeletal Functions

• Blood cell production:• Hematopoiesis – the process of forming

blood cells• Not always in the bone marrow

• As embryo develops, production is in the liver and spleen

• Then switches to the marrow• 2 types of Marrow

• Red• Yellow

Hematopoiesis

• Red marrow produces erythrocytes, leukocytes, and thrombocytes• Which is RBC? WBC? Platelets?

• Red color is due to hemoglobin• Infants have mostly red marrow

• Why would this be?

• As aging occurs, most red marrow is replaced with yellow marrow• Yellow stores fat

Storage of Minerals

• Minerals account for about 70% of bone matrix• Calcium #1

• When blood calcium levels are low hormones stimulate osteoclasts to break down bone tissue• Why would they do this?

• High blood calcuim levels stimulate osteoblasts to form bone

Changes in the Human Skeleton

In a fetus, the skeleton is primarily hyaline cartilage

What happens to the cartilage as we develop?

Replaced by bone

Cartilage remains in isolated areas

Where?

Bone Growth and Development (Endochondral)

Replacement of cartilage begins in the primary ossification center Occurs in the diaphysis What type of cell is active?

Continues in secondary ossification sites in epiphysis Epiphyseal plate is created between primary

and secondary ossification sites. You might know this by a different name

Bone Growth and Development (Endochondral)

• During this process the Medullary Cavity must be formed.

• How is this done?• Growth Hormone (GH) and sex hormones

control bone growth• DQ - When does bone growth stop?• When the primary and secondary ossification

sites grow together, closing the epiphyseal plate.

Long Bone Formation and Growth

Figure 5.4a

Long Bone Formation and Growth

Figure 5.4b

Bone Homeostasis

• To stay healthy, bone is continually resorbed and deposited

DQ - Why would this be? So old bone is broken down and new bone can

be formed. Controlled by two factors

Calcium levels in blood Stress on bones

Example: Running If this process becomes unbalanced bones

lose their mass and become weaker

Classification of Fractures

• Simple (aka closed)• Break does not penetrate the skin

• Compound (aka open)• The Broken bone

penetrates through the skin

Types of fractures• Greenstick –

• incomplete, only one side of bone

• Transverse –• Complete break to right angle to lengthwise of

long bone. Usually traumatic

• Oblique -• Rare. Break at an angle

• Comminuted –• More than two fragments broken off. traumatic

Types of fractures

Types of fractures

• Impacted –• Occurs after a fall, vertebral column

compressed, and cracks

• Pathologic -• Disorder that weakens the bone, leading to

a fracture

• Stress -• A bone becomes stressed from over use. • Can cause slight breaks

Repair Bone fractures

• Break causes blood vessels to rupture• What does this cause?

• Osteoclasts will remove bone fragments

• New vessels and Fibrocartilage form around break• Cartilage will be replaced by a bony

callus• Cell types - osteoblasts

Repair of fracture (Bone remodeling)

• There is typically more bone produced at site of healing• Why would this be?

• How does the bone get back to normal?

• Osteoclasts will reshape to like original bone

Skeletal Differences

• Adult vs. Infant skull

• Infant - face is small in comparison to cranial bones• How much of an adults length is made of

the head? Infants?

• Adults = about 1/8 Infants = about 1/4

• Fontanels - soft spots• What is the purpose of fontanels?

• Provides room for the brain to grow

Skeletal Disorders• Use your book to come up with a one

sentences summary of each of the following disorders.• Osteoarthritis• Rheumatoid arthritis• Gouty arthritis (Gout)• Osteoporosis• Scoliosis• Kyphosis• Lordosis• Osteomyelitis – bacterial infection of the

bone, causing pain and discomfort.• Paget disease – Bone remodeling is not

balanced leading to abnormal and enlarged but brittle bones.

Skeletal Disorders

Due to poor posture, Helga has felt like she is constantly leaning forward. An X-ray reveals excessive flexion in the thoracic curvature.

Kyphosis

Jimbo was a four sport athlete in high school and has continued with high impact excercises. He has complained of stiffness in his knees. He has also started to develop bone spurs, which hinder movement.

Osteoarthritis

Skeletal Disorders

Phoebe’s phalanges have fused together, so she is unable to flex his fingers. Her family has a history of this disorder and it is discovered that she has a high quantity of uric acid in her blood.

Gouty Arthritis

Whitney’s muscles in her lumbar region are excessively tight. This has caused the lumbar vertebrae to curve laterally towards the tightened muscles.

Scoliosis

Skeletal disorders

Gertrude has experienced a dull pain in her lower back. An x-ray revealed a fracture of her L2, yet Gertrude does not recall any impact that may have caused the break.

Osteoporosis

Will-i-am experienced a compound fracture a week ago and the bones were reduced while on a hunting trip. He has since developed a fever and severe pain in the area of injury. It is suspected that he has a bacterial infection.

Osteomyelitis

Skeletal Disorders

Mac has experienced pain in his bones. Through an x-ray it has been determined that his femur is misshapen. He has also been told by his doctor that he has a high alkaline phosphatase level in his blood.

Paget’s Disease

Marge’s joints have become swollen, reddened and tender. It has been very painful to move. This seems to to go away, but it keeps coming back.

Rheumatoid Arthritis

Joints

• Every bone in the body articulates with another bone• Except the hyoid

• Not all joints are movable.• Where would immovable joints be found?

• 3 Types of Joints• Fibrous• Cartilaginous• Synovial

Types of Joints• Fibrous

• Immovable• Examples?

• Cartilaginous• Both ends connected by cartilage• Immovable to limited movement• Examples?

• Synovial• surrounded by joint cavity• Contain hyaline cartilage, ligaments, and

synovial fluid• Examples?

Knee injuries Torn ACL, MCL,

PCL, LCL

Types of synovial joints• Plane - no rotation – bones glide past one another

• Example

• Hinge - move on one axis – like a door hinge• Example

• Pivot - rotation around an axis• Example

• Condyloid - move on two axes• Example

• Saddle – move on two axes• Example

• Ball and socket - move in all axes• Example

Types of Synovial Joints Based on Shape

Types of Synovial Joints Based on Shape

Figure 5.29d–f

Motions• Flexion-Angle

decreases

• Extension -

• Rotation – Move around an axis

• Abduction -

• Adduction -

• Circumduction -

• Dorsiflexion – raising foot to the shin

• Plantar flexion -

• Elevation – raise a body part

• Depression – lower a body part

• Supination -

• Pronation -