Chapter 2 of 5 - Anatomy Course
Skeletal System & Joints
Bones provide leverage and protection; joints couple stability with motion. This chapter links macroscopic structure to the movements tested on exams and in physical diagnosis.
Vignettes often reward knowing which joint type fails in a given injury (for example anterior shoulder dislocation at the glenohumeral joint) and which nerve runs nearby on the way to the clinic question.
Bone Structure and Remodeling
Compact bone forms dense shafts; spongy bone trabeculae resist multidirectional stress at epiphyses. Osteocytes maintain matrix; hydroxyapatite mineral confers hardness alongside collagen for toughness.
Wolff's law: bone architecture adapts to habitual loads; disuse leads to loss.
Mechanical load
Muscle pull, weight bearing, impact.
Osteocyte signaling
Mechanotransduction adjusts remodeling.
Osteoblast / osteoclast balance
Formation and resorption couple to net change.
Architecture updates
Trabeculae and cortical thickness follow stress lines.
Compact bone forms the dense cortex; spongy bone trabeculae resist multidirectional stress at the ends. Relate this layout to fracture patterns and bone scan uptake.
Calcium
Calcium phosphate mineral in hydroxyapatite crystals stiffens bone matrix; vitamin D and PTH regulate serum calcium and skeletal turnover.
Formula
Ca
Mol. Weight
40.08 g/mol
Joint Classification
| Category | Mobility |
|---|---|
| Fibrous | Little to none (skull sutures, tibiofibular syndesmosis) |
| Cartilaginous | Limited (symphysis pubis, intervertebral discs) |
| Synovial | Free movement; many types (hinge, pivot, saddle, ball-and-socket) |
Quick Check
Which joint type best describes the elbow (humeroulnar articulation) in terms of primary movement?
Fill in the Blank
The connective tissue that covers the outer surface of bone except at joint surfaces is the________.
Identify joint and motion vector
What movement was forced beyond physiologic range?
Recall stabilizing structures
Ligaments, labrum, capsule, muscles.
Trace adjacent nerves and vessels
Axillary nerve with shoulder, sciatic with hip replacement, etc.
Match classic presentation
Anterior shoulder, lateral ankle inversion, scaphoid fall on outstretched hand.
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