Muscular System, Skeletal System, Joints, and Nutrition: Study Guide

Nutrition

Key Definitions in Nutrition

Understanding the basic terms in nutrition is essential for grasping how the body processes and utilizes nutrients for energy and growth.

• Metabolism: The sum of all chemical reactions that occur within a living organism to maintain life. It includes both anabolic (building up) and catabolic (breaking down) processes.

• Cellular Respiration: The process by which cells convert glucose and oxygen into energy (ATP), carbon dioxide, and water.

• Nutrition: The intake and utilization of food substances by which organisms obtain energy and materials for growth, maintenance, and repair.

• Catabolism: The metabolic pathways that break down molecules into smaller units and release energy.

• Anabolism: The metabolic pathways that construct molecules from smaller units, requiring energy input.

Nutrient Categories and Biological Importance

Nutrients are classified based on their chemical nature and function in the body.

• Macronutrients: Carbohydrates, proteins, and fats; provide energy and structural materials.

• Micronutrients: Vitamins and minerals; essential for enzyme function and cellular processes.

• Water: Vital for chemical reactions, transport, and temperature regulation.

Each category is crucial for maintaining biological activity, growth, and homeostasis.

Processing Nutrients

Nutrient processing occurs in three main stages:

• Digestion: Breakdown of food in the gastrointestinal tract.

• Absorption: Uptake of nutrients into the bloodstream, primarily in the small intestine.

• Cellular Metabolism: Utilization of nutrients within cells for energy and biosynthesis.

Cellular Respiration: Reactants and Products

Cellular respiration involves the following:

• Reactants: Glucose (C6H12O6) and oxygen (O2).

• Products: Carbon dioxide (CO2), water (H2O), and ATP (energy).

Pathways of Glucose Oxidation

Glucose oxidation occurs via three main mechanisms:

• Glycolysis: Occurs in the cytoplasm; net gain of 2 ATP.

• Krebs Cycle (Citric Acid Cycle): Occurs in the mitochondrial matrix; net gain of 2 ATP.

• Electron Transport Chain: Occurs in the inner mitochondrial membrane; net gain of 34 ATP.

Overall equation:

$\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{ATP}$

Muscular System

Types of Muscle Tissue

Muscle tissue is classified into three types, each with distinct structure and function.

• Skeletal Muscle: Voluntary, striated, attached to bones for movement.

• Cardiac Muscle: Involuntary, striated, found only in the heart.

• Smooth Muscle: Involuntary, non-striated, found in walls of hollow organs.

Shared Characteristics of Muscles

• Excitability (responsiveness to stimuli)

• Contractility (ability to shorten)

• Extensibility (ability to stretch)

• Elasticity (ability to return to original shape)

Functions of Muscles

• Movement of body parts

• Maintenance of posture

• Stabilization of joints

• Heat generation

Muscle Structure and Organization

Muscle tissue is organized in a hierarchical manner:

• Whole muscle → fascicles → muscle fibers → myofibrils → myofilaments

Connective tissue layers:

• Perimysium: Surrounds fascicles (bundles of muscle fibers).

• Endomysium: Surrounds individual muscle fibers.

Muscle Fiber Structure and Function

• Muscle fibers are long, cylindrical cells containing multiple nuclei and myofibrils.

• Myofibrils are composed of repeating units called sarcomeres, responsible for contraction.

Skeletal Tissue Features

• Origin: Attachment to stationary bone

• Insertion: Attachment to moving bone

• Motor Unit: A motor neuron and all the muscle fibers it innervates

Orientation of Smooth Muscle

• Arranged in sheets, often in two layers (longitudinal and circular) for coordinated contraction.

Comparison of Muscle Types

Feature	Skeletal	Cardiac	Smooth
Striations	Yes	Yes	No
Control	Voluntary	Involuntary	Involuntary
Location	Bones	Heart	Organs
Cell Shape	Long, cylindrical	Branched	Spindle-shaped

Skeletal System

Bone Classification

• Long bones: Longer than wide (e.g., femur)

• Short bones: Cube-shaped (e.g., carpals)

• Flat bones: Thin, flattened (e.g., sternum)

• Irregular bones: Complex shapes (e.g., vertebrae)

Structural Components of a Long Bone

• Diaphysis: Shaft, composed of compact bone

• Medullary cavity: Central cavity containing bone marrow

• Epiphyses: Ends of the bone, composed of spongy bone

• Periosteum: Outer fibrous layer

• Endosteum: Inner lining of the medullary cavity

Ligaments and Tendons

• Ligaments: Connect bone to bone

• Tendons: Connect muscle to bone

Bone Cells

• Osteoblasts: Bone-forming cells

• Osteocytes: Mature bone cells

• Osteoclasts: Bone-resorbing cells

Compact vs. Spongy Bone

Feature	Compact Bone	Spongy Bone
Density	High	Low
Location	Diaphysis	Epiphyses
Structure	Osteons	Trabeculae

Microscopic Anatomy of Compact Bone

• Composed of osteons (Haversian systems)

• Central canal contains blood vessels and nerves

• Lacunae house osteocytes

Ossification of Long Bones

• Begins in the embryo (primary ossification center)

• Secondary ossification occurs in epiphyses after birth

Joints

Types of Joints

• Fibrous Joints: Bones joined by dense connective tissue; immovable (e.g., sutures in skull)

• Cartilaginous Joints: Bones joined by cartilage; slightly movable (e.g., intervertebral discs)

• Synovial Joints: Bones separated by a fluid-filled cavity; freely movable (e.g., knee, shoulder)

Functional Classification of Joints

Type	Movement	Example
Synarthrotic	Immovable	Sutures
Amphiarthrotic	Slightly movable	Intervertebral discs
Diarthrotic	Freely movable	Knee, elbow

Components of a Synovial Joint

• Articular cartilage

• Joint (synovial) cavity

• Articular capsule

• Synovial fluid

• Ligaments

Arthritis

• Osteoarthritis: Degenerative joint disease due to wear and tear

• Rheumatoid Arthritis: Autoimmune disorder causing inflammation of joints

Movements of Joints

• Flexion/Extension/Hyperextension: Decreasing/increasing angle between bones

• Abduction/Adduction: Moving limb away/toward midline

• Elevation/Depression: Lifting/lowering a body part

• Protraction/Retraction: Moving a body part forward/backward

• Inversion/Eversion: Turning sole of foot inward/outward

• Dorsiflexion/Plantar Flexion: Bending foot upward/downward

Joint Types and Examples

Joint Type	Movement	Example
Pivot	Rotation	Neck
Hinge	Flexion/Extension	Elbow, knee

Additional info: Images referenced in the original file are not included, but students should be able to label diagrams of bone and muscle tissue, including features such as osteons, fascicles, and connective tissue layers.