ch. 6 bones tissues Flashcards
Cartilage
• Skeletal cartilage – Water lends resiliency – Contains no blood vessels or nerves – Perichondrium surrounds • Dense connective tissue girdle – Contains blood vessels for nutrient delivery – Resists outward expansion • All contain chondrocytes in lacunae and extracellular matrix
Hyaline cartilage
- Provides support, flexibility, and resilience
- Collagen fibers only; most abundant type
- Articular, costal, respiratory, nasal cartilage
Elastic cartilage
- Similar to hyaline cartilage, but contains elastic fibers
* External ear and epiglottis
Fibrocartilage
- Thick collagen fibers—has great tensile strength
* Menisci of knee; vertebral discs
Appositional growth
– Cells secrete matrix against external face of existing cartilage
Interstitial growth
– Chondrocytes divide and secrete new matrix, expanding cartilage from within
Classification of Bones
• 206 named bones in skeleton • Divided into two groups – Axial skeleton • Long axis of body • Skull, vertebral column, rib cage – Appendicular skeleton • Bones of upper and lower limbs • Girdles attaching limbs to axial skeleton
Classification of Bones by Shape
• Long bones • Short bones • Flat bones • Irregular bones Classification of Bones by Shape
Long bones
– Longer than they are wide
– Limb, wrist, ankle bones
Short bones
– Cube-shaped bones (in wrist and ankle)
– Sesamoid bones (within tendons, e.g., Patella)
– Vary in size and number in different individuals
Flat bones
– Thin, flat, slightly curved
– Sternum, scapulae, ribs, most skull bones
Irregular bones
– Complicated shapes
– Vertebrae, coxal bones
Seven important functions of bone
– Support – Protection – Movement – Mineral and growth factor storage – Blood cell formation – Triglyceride (fat) storage – Hormone production
Bones
• Are organs – Contain different types of tissues • Bone (osseous) tissue, nervous tissue, cartilage, fibrous connective tissue, muscle and epithelial cells in its blood vessels • Three levels of structure – Gross anatomy – Microscopic – Chemical
Gross Anatomy
• Bone textures – Compact and spongy bone • Compact – Dense outer layer; smooth and solid • Spongy (cancellous or trabecular) – Honeycomb of flat pieces of bone deep to compact called trabeculae
Structure of Short, Irregular, and Flat Bones
• Thin plates of spongy bone covered by compact bone
• Plates sandwiched between connective tissue membranes
– Periosteum (outer layer) and endosteum
• No shaft or epiphyses
• Bone marrow throughout spongy bone; no marrow cavity
• Hyaline cartilage covers articular surfaces
Structure of Typical Long Bone
• Diaphysis
– Tubular shaft forms long axis
– Compact bone surrounding medullary cavity
• Epiphyses
– Bone ends
– External compact bone; internal spongy bone
– Articular cartilage covers articular surfaces
– Between is epiphyseal line
• Remnant of childhood bone growth at epiphyseal plate
Membranes: Periosteum
• White, double-layered membrane
• Covers external surfaces except joint surfaces
• Outer fibrous layer of dense irregular connective tissue
– Sharpey’s fibers secure to bone matrix
• Osteogenic layer abuts bone
– Contains primitive stem cells – osteogenic cells
• Many nerve fibers and blood vessels
• Anchoring points for tendons and ligaments
Membranes: Endosteum
• Delicate connective tissue membrane covering internal bone surface
• Covers trabeculae of spongy bone
• Lines canals that pass through compact bone
• Contains osteogenic cells that can differentiate into other bone cells
Hematopoietic Tissue in Bones
• Red marrow
– Found within trabecular cavities of spongy bone and diploë of flat bones (e.g., Sternum)
– In medullary cavities and spongy bone of newborns
– Adult long bones have little red marrow
• Heads of femur and humerus only
– Red marrow in diploë and some irregular bones is most active
– Yellow marrow can convert to red, if necessary
Bone Markings
- Sites of muscle, ligament, and tendon attachment on external surfaces
- Joint surfaces
- Conduits for blood vessels and nerves
- Projections
- Depressions
- Openings
Bone Markings
• Projections
– Most indicate stresses created by muscle pull or joint modifications
• Depressions and openings
• Usually allow nerves and blood vessels to pass
Microscopic Anatomy of Bone: Cells of Bone Tissue
• Five major cell types • Each specialized form of same basic cell type – Osteogenic cells – Osteoblasts – Osteocytes – Bone lining cells – Osteoclasts
Osteogenic Cells
• Also called osteoprogenitor cells
– Mitotically active stem cells in periosteum and endosteum
– When stimulated differentiate into osteoblasts or bone lining cells
• Some persist as osteogenic cells
Osteoblasts
• Bone-forming cells
• Secrete unmineralized bone matrix or osteoid
– Includes collagen and calcium-binding proteins
• Collagen = 90% of bone protein
• Actively mitotic
Osteocytes
• Mature bone cells in lacunae
• Monitor and maintain bone matrix
• Act as stress or strain sensors
– Respond to and communicate mechanical stimuli to osteoblasts and osteoclasts (cells that destroy bone) so bone remodeling can occur
Bone Lining Cells
- Flat cells on bone surfaces believed to help maintain matrix
- On external bone surface called periosteal cells
- Lining internal surfaces called endosteal cells
