Skeletal and Muscular Systems: Study Guide for Anatomy & Physiology Exam

Study Guide - Smart Notes

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The Skeletal System

Functions of the Skeletal System

The skeletal system provides structural support, protection for internal organs, facilitates movement, stores minerals, and houses bone marrow for blood cell production.

Bone matrix components: The main protein is collagen, and the primary mineral is calcium.

Cells of Bone: Osteocytes, Osteoblasts, Osteoclasts, Osteogenic Cells

Osteocytes: Mature bone cells that maintain bone tissue.
Osteoblasts: Cells responsible for bone formation.
Osteoclasts: Cells that break down bone tissue for remodeling.
Osteogenic cells: Stem cells that differentiate into osteoblasts.

Bone Membranes

Periosteum: Outermost membrane with fibrous outer and cellular inner layers.
Endosteum: Incomplete cellular membrane lining the marrow cavity, central canals, and trabeculae.

Types of Bone Tissue

Compact bone: Dense structure with osteons (central canals, lamellae, canaliculi, lacunae).
Spongy bone: Contains trabeculae, lighter and stores bone marrow, withstands stress from multiple directions.

Types of Bones

Long, flat, sutural, irregular, short, sesamoid: Know their general characteristics and be able to recognize examples.

Structure of Long Bones

Diaphysis: Shaft, contains medullary cavity.
Epiphysis: Ends, mostly spongy bone covered by compact bone.
Metaphysis: Region between diaphysis and epiphysis.

Osteogenesis and Ossification

Osteogenesis is the process of bone formation, always involving calcification.

Intramembranous ossification: Bone develops directly from mesenchymal tissue (e.g., flat bones of skull).
Endochondral ossification: Bone develops by replacing hyaline cartilage (e.g., long bones).

Bone Remodeling

Appositional growth: Bone increases in diameter.
Remodeling: Involves bone resorption and deposition; regulated by osteoclasts and osteoblasts.

Hormonal Regulation of Bone

Vitamin D, Vitamin C: Essential for bone health; deficiency leads to bone disorders.
Growth hormone (GH): Stimulates bone growth; excess leads to gigantism/acromegaly, deficiency to pituitary dwarfism.
Parathyroid hormone (PTH) and Calcitonin: Regulate calcium levels in blood and bone.

Calcium Homeostasis

PTH: Released in response to low calcium, increases blood calcium.
Calcitonin: Released in response to high calcium, decreases blood calcium.

Fractures

Types: Closed, open, comminuted, greenstick, displaced.
Steps in fracture repair: Hematoma formation, fibrocartilaginous callus, bony callus, bone remodeling.

Axial and Appendicular Skeleton

Axial skeleton: Skull, vertebral column, rib cage.
Appendicular skeleton: Limbs and girdles.

Joints (Articulations)

Fibrous joints: Sutures, gomphoses, syndesmoses.
Cartilaginous joints: Synchondroses, symphyses.
Synovial joints: Most mobile; types include planar, hinge, pivot, condylar, saddle, ball-and-socket.
Movements: Flexion, extension, abduction, adduction, circumduction, rotation.

The Muscular System

Functions of the Muscular System

Muscles produce movement, maintain posture, stabilize joints, and generate heat.

Connective tissue membranes: Epimysium, perimysium, endomysium.

Muscle Structure

Fascicle: Bundle of muscle fibers.
Muscle fiber types: Parallel, convergent, pennate, bipennate, multipennate, circular.
Origin and insertion: Origin is the fixed attachment, insertion moves with contraction.
Levers: First, second, and third class levers in muscle action.

Microscopic Structure of Muscle

Sarcomere: Functional unit of muscle; contains thick (myosin) and thin (actin, troponin, tropomyosin) filaments.
Myofibrils: Bundles of protein filaments.

Neural Control/Excitation Phase

Neuromuscular junction (NMJ): Site where motor neuron stimulates muscle fiber.
Acetylcholine (ACh): Neurotransmitter released into synaptic cleft.

Excitation-Contraction Coupling

Steps: Action potential, ACh release, depolarization, calcium release, cross-bridge formation.
Relaxation: Removal of calcium, breakdown of ACh.

Muscle Contraction Types

Isotonic: Muscle changes length (concentric and eccentric).
Isometric: Muscle length remains constant.

Muscle Fiber Types

Type I (slow-twitch): Fatigue-resistant, aerobic, used for endurance.
Type II (fast-twitch): Fatigue quickly, anaerobic, used for power and speed.

Energy for Muscle Contraction

ATP: Main energy source.
Aerobic respiration: Uses oxygen, produces more ATP.
Anaerobic fermentation: No oxygen, produces lactic acid.

Cardiac and Smooth Muscle

Cardiac muscle: Involuntary, striated, found in heart.
Smooth muscle: Involuntary, non-striated, found in walls of hollow organs.

Summary Table: Types of Joints

Joint Type	Structure	Example
Fibrous	Sutures, gomphoses, syndesmoses	Skull sutures, teeth sockets
Cartilaginous	Synchondroses, symphyses	Epiphyseal plate, pubic symphysis
Synovial	Planar, hinge, pivot, condylar, saddle, ball-and-socket	Knee, elbow, shoulder

Key Equations

Muscle force:
ATP production (aerobic):

Additional info:

Some details on bone and muscle physiology were expanded for clarity and completeness.