Do Now: 1. How many bones can you name in 60 seconds? (Time yourself on the clock- Be Honest! 2. Make a guess for what 3 of the functions the skeletal system are. 3. If “osteo” means bone, then what is an osteocyte? What about an osteoblast?

Ch 5: The Skeletal System Axial Skeleton, Skull, Vertebrae, Appendicular Skeleton, Skeletal Conditions Joints

The Skeletal System 1. Bones (skeleton) 2. Joints 3. Cartilages Parts of the skeletal system 1. Bones (skeleton) 2. Joints 3. Cartilages 4. Ligaments

Axial vs. Appendicular Divided into two divisions: Axial skeleton – bones that form the longitudinal axis of the body Example: skull, bony thorax, & vertebral column Appendicular skeleton – bones of the limbs and girdles Example: arms, shoulder, legs, hips

Functions of Bones 1. Support of the body 2. Protection of soft organs 3. Movement due to attached skeletal muscles 4. Storage of minerals and fats 5. Blood cell formation

Bones of the Human Body Two basic types of bone tissue Compact bone The adult skeleton has 206 bones Two basic types of bone tissue Compact bone Homogeneous Spongy bone Small needle-like pieces of bone Many open spaces Figure 5.2b

Classification of Bones Long bones Typically longer than wide Have a shaft with heads at both ends Contain mostly compact bone Examples: Femur, humerus

Classification of Bones Short bones Generally cube-shape Contain mostly spongy bone Examples: Carpals, tarsals

Classification of Bones Flat bones Thin and flattened Usually curved Thin layers of compact bone around a layer of spongy bone Ex: Skull, ribs, sternum

Classification of Bones Irregular bones Irregular shape Do not fit into other bone classification categories Example: Vertebrae and hip

Classification of Bones on the Basis of Shape Figure 5.1

Intro to Skeletal System Video 05 _Human Body Skeletal System 2:30-5:30

Bone Markings Surface features of bones Sites of attachments for muscles, tendons, and ligaments Passages for nerves and blood vessels Categories of bone markings Projections and processes – go out Depressions or cavities – go in

Gross Anatomy of a Long Bone Diaphysis Shaft Composed of compact bone Epiphysis Ends of the bone Composed mostly of spongy bone 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 a Long Bone Periosteum Outside covering of the diaphysis Fibrous connective tissue membrane Arteries Supply bone cells with nutrients Figure 5.2c

Structures of a Long Bone Articular cartilage Covers the external surface of the epiphyses Made of hyaline cartilage Decreases friction at joint surfaces Figure 5.2a

Microscopic Anatomy of Bone Osteon (Haversian System) A unit of bone Central (Haversian) canal Opening in the center of an osteon Carries blood vessels and nerves Perforating (Volkman’s) canal Canal perpendicular to the central canal

Microscopic Anatomy of Bone Figure 5.3

Microscopic Anatomy of Bone Figure 5.3

Microscopic Anatomy of Bone Lacunae Cavities containing bone cells (osteocytes) Arranged in concentric rings Lamellae Rings around the central canal Sites of lacunae Detail of Figure 5.3

Canaliculi Microscopic Anatomy of Bone Tiny canals Radiate from the central canal to lacunae Form a transport system Detail of Figure 5.3

Types of Bone Cells Osteocytes Osteoblasts Osteoclasts Mature bone cells Osteoblasts Bone-forming cells Osteoclasts Bone-destroying cells Break down bone matrix for remodeling and release of calcium Bone remodeling is a process by both osteoblasts and osteoclasts

Bone Structure

Changes in the Human Skeleton In embryos, the skeleton is primarily hyaline cartilage During development, much of this cartilage is replaced by bone Cartilage remains in isolated areas Bridge of the nose Parts of ribs Joints

Long Bone Formation and Growth Figure 5.4a

Bone Growth Epiphyseal plates allow for growth of long bone during childhood New cartilage is continuously formed Older cartilage becomes ossified Cartilage is broken down Bone replaces cartilage

Do Now What are the major parts of the skeletal system? What are the four types of bones? Why do you think there needs to be four different types of bones?

Bone Growth Bones are remodeled and lengthened until growth stops Bones change shape somewhat Bones grow in width

Long Bone Formation and Growth Figure 5.4b

Remodeling The adult skeleton: maintains itself replaces mineral reserves Remodeling: recycles and renews bone matrix **** involves osteocytes, osteoblasts, and osteoclasts

Bone Remoldeling cont’d Bone continually remodels, recycles, and replaces Turnover rate varies If deposition is greater than removal, bones get stronger If removal is faster than replacement, bones get weaker

Bone Growth

Effects of Exercise on Bone Mineral recycling allows bones to adapt to stress Heavily stressed bones become thicker and stronger

Bone Degeneration Bone degenerates quickly Up to 1/3 of bone mass can be lost in a few weeks of inactivity

Fractures- cracks or breaks in bones caused by physical stress

Bone Fractures A break in a bone Healing time is approx. six to eight weeks for simple fractures Healing time varies

Types of fractures Simple (closed) – clean break, does not break skin Compound (open) – broken ends of the bone protrude through soft tissue and skin Comminuted – bone breaks into many fragments

Bone Fragments Compression - bone is crushed Depressed – broken bone is pressed inward Impacted – broken bone end are forced into each other

Bone Fragments Spiral – ragged break caused by twisting forces Greenstick – incomplete break, common in children Figure 6–16 (9 of 9)

Common Types of Fractures Table 5.2

Treatment Two Steps: 1. Bone fractures are treated by reduction and then immobilization

Treatment continued 2. Realignment of the bone Closed reduction – bone ends are forced back into normal position by doctor’s hands Open reduction – surgery is needed to put bone ends together using pins or wires 3. After reduction, it is immobilized by a cast or traction to allow for healing

Repair of Bone Fractures Hematoma (blood-filled swelling) is formed Break is splinted by fibrocartilage to form a callus Fibrocartilage callus is replaced by a bony callus Bony callus is remodeled to form a permanent patch

Stages in the Healing of a Bone Fracture Figure 5.5

Age and Bones Bones become thinner and weaker with age Osteopenia weakening of bones’ mass begins between ages 30 & 40 Bone mass loss per decade Women lose 8% Men lose 3%

Sec 1 Review

The End of Section 1 Assignments for this section: Review Questions from Notes Numbers 1-9 Ch5 Handout ｷPg1-2