U2 Lecture 1 Flashcards
1. List and describe the functions of the skeletal system 2. Differentiate between the two divisions of the skeletal system and give examples 3. Describe the classification of bone based on shape, giving examples for each type 4. Describe the anatomy of flat bones and long bones 5. List and describe the functions of the 4 cell types found in bone 6. Discuss modeling and remodeling of bone
Functions of the skeletal system
- Support
- Protection from abrasions
- Mineral storage
- Triglyceride storage
- Red and white blood cell formation (hemopoiesis)
- Leverage (assistance in movement)
Composition of the skeletal system
- The skeleton is all bones and connective tissues which attach them to each other (cartilage, ligaments, joints etc)
What is unique of each bone?
Each bone is an organ containing osseous (connective) tissue, blood vessels, nerves, lymphatic vessels, cartilage, and connective tissue coverings
What is found within bones?
- articular cartilage
- spongy bone (containing red bone marrow)
- red bone marrow
- epiphyseal line
- compact bone
- endosteum (lines medullary cavity)
- nutrient artery
- medullary cavity (contains yellow bone marrow in adults)
- periosteum
Divisions of the skeletal system
Axial and Appendicular skeleton
Types of bones
long (humerus), short (trapezoid, wrist bone), flat (sternum), irregular (vertebra), sesamoid (patella), sutural (skill bones), and pneumatized (ethmoid)
Anatomy of flat bones
compact bone and spongy bone (diploe)
Anatomy of sutural bones
- found between suture in the skull, not everyone has them
Anatomy of long bones
- Sections: epiphysis, metaphysis and diaphysis
- Components: spongy bone, compact bone, endosteum, periosteum, medullary cavity and nutrient artery
Importance of the endosteum and the periosteum
Important for bone growth and remodeling
Define Periosteum
- Connective tissue membrane covering external surface of bone
- continuous with tendons, connective tissue of joints
- attached to bone matrix via perforating fibers
Periosteum layers
- Outer fibrous layer
2. Inner osteogenic layer
Define endosteum
- Lining inner surfaces of bone including marrow cavity, trabecullae of spongy bone, canals of compact bone
- Contains osteogenic cells (important for bone growth and remodeling)
Define osteology
The study of bone tissue
Main composition of bone
Connective tissue
What makes up connective tissue?
Extracellular matrix and cells
What makes up the extracellular matrix?
Ground substance and fibers
Define ground substance
Organic and inorganic compoents
What type of fibers are found in the extracellular matrix?
Collagen fibers
What are the 4 types of cells found within bones?
Osteogenic cells, osteoblasts, osteocytes and osteoclasts
Define osteogenic (osteoprogenitor) cells
Stem cells that are formed from mesenchyme (embryonic connective tissue)
What type of cells do osteogenic cells form?
Osteoblasts
- osteogenic cells go through mitosis to form daughter osteogenic cells and then differentiate into osteoblasts
Define osteoblasts
Cells that form bone matrix and eventually builds bone
- They synthesize organic components of matrix and initiate calcification (takes calcium from blood and deposit it within matrix by exocytosis)
- They are immature cells
What type of cells do osteoblasts form?
Osteocytes
Define osteocytes
Mature cell involved in maintaining bone tissue
Define osteoclasts
Break down bone for bone resorption
- They release proteolytic enzymes and acids to degrade collagen and release minerals to blood
- Formed from myeloid stem cells (not osteogenic cells)
Define bone modeling
Bone is formed by osteoblasts without prior bone resorption
- happens during growth
- produces change in bone size and shape
Define bone remodeling
Occurs when bone is first resorbed by osteoclasts and then formed in the same location by osteoblasts
- happens throughout life
Goal of modeling and remodeling
Achieve strength for loading and lightness for mobility
- deposit bone where it is needed to achieve peak strength (during growth)
- remove damaged bone where it’s not needed to avoid bulk and maintain strength (during adulthood)
Define fatigue damage
damage to bone after repeated loading and wear
How do cells react to fatigue damage?
- Osteocytes detect location and magnitude of damage
- Osteoclasts remove damage
- Osteoblasts replace it with new bone
- Restores bone’s material composition, micro- and macro-architecture
Steps of bone remodeling
- Activation: pre-osteoclasts are stimulated and differentiate under the influence of cytokines and growth factors into mature active osteoclasts
- Resorption: osteoclasts digest mineral matrix (old bone)
- Reversal: end of resorption, recruitment of osteoblasts
- Formation: osteoblasts synthesize new bone matrix
- Quiescence: osteoblasts become resting bone lining cells on the newly formed bone surface
Osteoclast characteristics
- Sealing zone
- Ruffled Border
- Functional Secretory Domain
