Chapter 5 Gross & Microscopic Bone Anatomy
The Skeletal System Parts of the skeletal system Bones (skeleton) Joints Cartilages Ligaments Divided into 2 divisions Axial skeleton Appendicular skeleton
Functions of Bones Support body Protect 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 types of bone tissue Compact bone - Homogeneous Spongy bone - Small needle-like pieces of bone - Many open spaces
Classification Based on Shape
Paranasal Sinuses Hollow parts of bones surrounding nasal cavity Functions: Lighten the skull Resonate and amplify voice
The Hyoid Bone Only bone that doesn’t articulate with another bone Moveable base for tongue
Gross Anatomy of a Long Bone Know 7 Structures 1. Diaphysis Shaft compact bone 2. Epiphysis Ends of the bone mostly spongy bone
3. Periosteum 4. Sharpey’s fibers 5. Arteries Outside covering of diaphysis Fibrous connective tissue membrane 4. Sharpey’s fibers Secure periosteum to bone 5. Arteries Supply bone cells with nutrients
6. Articular cartilage 7. Medullary cavity Covers the ends hyaline cartilage Decreases friction 7. Medullary cavity Cavity of shaft Contains yellow marrow (mostly fat) in adults Contains red marrow (for blood cell formation) in infants
Microscopic Anatomy of Bone Know 6 parts: 1. Osteon (Haversian System) A unit of bone 2. Central (Haversian) canal Opening in the center For blood vessels & nerves 3. Perforating (Volkmann’s) canals perpendicular to central canal
6. Canaliculi 4. Lacunae 5. Lamellae Cavities containing bone cells (osteocytes) Arranged in rings 5. Lamellae Rings around central canal 6. Canaliculi Tiny canals Radiate from central canal to lacunae Transport system
Changes in the Growing Skeleton In embryos, the skeleton is 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
Bone Growth Epiphyseal (growth) plates - growth of long bone during childhood - New cartilage is continuously formed - Older cartilage ossified (broken down & replaced by bone)
Remodeled & lengthened - until growth stops - Bones change shape somewhat & grow in width
Types of Bone Cells 1. Osteocytes 2. Osteoblasts – b for build Mature bone cells 2. Osteoblasts – b for build Bone-forming cells 3. Osteoclasts – hard c for kill Bone-destroying cells Break down bone matrix for remodeling and release of calcium Bone remodeling is a process by both osteoblasts and osteoclasts
Developmental Aspects At birth, skull bones incomplete Bones joined by fibrous membranes – fontanelles Fontanelles replaced by bone within 2 years Fetal skull is large compared to total body length
Upper Lower (UL) Ratio - Reaches 1:1 about age 10
Bone Fractures A break in a bone Types 1. Closed (simple) fracture –does not penetrate skin 2. Open (compound) fracture –penetrates through skin Bone fractures are treated by reduction and immobilization - Realignment of the bone
Common Types of Fractures
Repair of Bone Fractures 1. Hematoma (blood-filled swelling) is formed 2. Break is splinted by fibrocartilage to form a cartilaginous callus 3. Fibrocartilage callus is replaced by a bony callus 4. Bony callus is remodeled to form a permanent patch