Comprehensive Study Guide for Skeletal, Muscular, Skin, and Digestive Systems

The Skeletal System

Major Bones and Their Locations

The human skeleton is divided into two main parts: the axial skeleton and the appendicular skeleton. Understanding the location and function of major bones is essential for anatomy and physiology.

• Axial Skeleton: Includes the skull, vertebral column, and rib cage. Provides support and protection for the brain, spinal cord, and thoracic organs.

• Appendicular Skeleton: Comprises the limbs and girdles (shoulder and pelvic). Facilitates movement and interaction with the environment.

Classification of Bones

Bones are classified based on their shape and structure:

• Long Bones: Longer than they are wide (e.g., femur, humerus).

• Short Bones: Nearly equal in length and width (e.g., carpals, tarsals).

• Flat Bones: Thin, flattened, and usually curved (e.g., sternum, skull).

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

Bones also contain two types of tissue:

• Compact Bone: Dense and strong, forms the outer layer.

• Spongy Bone: Porous, found at the ends of long bones and inside flat bones.

The epiphyseal plate is a region of growing tissue in children; after growth, it becomes the epiphyseal line.

Structure and Protection

The skeletal system provides structural support and protects vital organs:

• Skull protects the brain.

• Rib cage protects the heart and lungs.

• Vertebrae protect the spinal cord.

Bone Cells and Functions

• Osteocytes: Mature bone cells that maintain bone tissue.

• Osteoblasts: Cells that build new bone.

• Osteoclasts: Cells that break down bone tissue.

• Osteoporosis: Condition where bone density decreases, increasing fracture risk.

• Hematopoiesis: Blood cell formation, occurs in red marrow.

• Articular (Hyaline) Cartilage: Covers bone surfaces in joints, reduces friction.

• Fibrocartilage: Provides support and absorbs shock (e.g., intervertebral discs).

• Red Marrow: Produces blood cells.

• Yellow Marrow: Stores fat.

Types of Fractures

Fractures are classified by their characteristics:

• Simple (Closed) Fracture: Bone breaks but does not pierce the skin.

• Compound (Open) Fracture: Bone breaks and pierces the skin.

• Comminuted Fracture: Bone is shattered into several pieces.

• Greenstick Fracture: Bone bends and cracks, common in children.

Calcium Homeostasis and Minerals

Calcium levels in the body are regulated by hormones and minerals:

• Parathyroid Hormone (PTH): Increases blood calcium by stimulating osteoclasts.

• Calcitonin: Lowers blood calcium by inhibiting osteoclasts.

• Main Minerals: Calcium and phosphorus are essential for bone strength.

Equation:

$\text{Ca}^{2+} + \text{PO}_4^{3-} \rightarrow \text{Hydroxyapatite} \ (\text{bone mineral})$

Synovial Joints and Movements

Synovial joints are freely movable and have a synovial cavity:

• Basic Principles: Articular cartilage, synovial fluid, joint capsule.

• Types of Movement:

  • Flexion: Decreases angle between bones.

  • Extension: Increases angle between bones.

  • Hyperextension: Extension beyond normal range.

  • Abduction: Movement away from midline.

  • Adduction: Movement toward midline.

  • Rotation: Bone turns around its axis.

  • Pronation: Palm down.

  • Supination: Palm up.

  • Dorsiflexion: Foot upward.

  • Plantar Flexion: Foot downward.

The Muscular System

Muscle Insertion, Belly, and Origin

Muscle movement depends on three main anatomical features:

• Origin: Fixed attachment point.

• Insertion: Movable attachment point.

• Belly: Thick, central part of the muscle.

When a muscle contracts, the insertion moves toward the origin.

Types of Muscle Tissue

There are three types of muscle tissue, each with unique characteristics:

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

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

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

Impulse Transmission in Skeletal Muscle

Muscle contraction is initiated by nerve impulses:

• Neurotransmitter: Acetylcholine (ACh) is released at the neuromuscular junction.

• Minerals: Calcium ions (Ca2+) are essential for contraction.

• Synaptic Cleft: Gap between nerve and muscle; ACh crosses this to stimulate muscle.

Equation:

$\text{ACh} \rightarrow \text{Muscle Fiber Depolarization} \rightarrow \text{Ca}^{2+} \text{ Release} \rightarrow \text{Contraction}$

Metabolic Waste and Exercise Impact

• Lactic Acid: Produced during anaerobic respiration, causes muscle fatigue.

• Exercise: Resistance training increases muscle size (hypertrophy); endurance training increases stamina.

Isotonic vs. Isometric Contractions

• Isotonic Contraction: Muscle changes length, movement occurs (e.g., lifting weights).

• Isometric Contraction: Muscle length does not change, no movement (e.g., holding a plank).

Connective Tissues

• Tendons: Connect muscle to bone.

• Ligaments: Connect bone to bone.

• Cartilage: Provides cushioning in joints.

• Layers of Connective Tissue: Epimysium, perimysium, endomysium surround muscle fibers.

Skin and Body Membranes

Skin Layers and Functions

The skin is composed of three main layers:

• Epidermis: Outermost layer, provides protection.

• Dermis: Middle layer, contains blood vessels, nerves, and glands.

• Hypodermis: Deepest layer, stores fat.

Cells include keratinocytes, melanocytes, and Langerhans cells.

Body Cavities and Lining Tissues

• Body Cavities: Spaces within the body that house organs (e.g., thoracic, abdominal).

• Lining Tissue: Epithelial tissue lines cavities, provides protection and secretion.

Types of Membranes

• Mucous Membranes: Line body cavities open to the exterior.

• Serous Membranes: Line closed cavities, secrete serous fluid.

• Cutaneous Membrane: Skin.

• Synovial Membrane: Lines joint cavities, produces synovial fluid.

Exocrine vs. Endocrine Glands

• Exocrine Glands: Secrete products into ducts (e.g., sweat, salivary glands).

• Endocrine Glands: Secrete hormones directly into the bloodstream (e.g., thyroid, adrenal glands).

Burns and Rule of Nines

Burns are classified by depth and extent. The rule of nines estimates the percentage of body surface affected:

Body Region	Percentage
Head and Neck	9%
Each Arm	9%
Each Leg	18%
Anterior Trunk	18%
Posterior Trunk	18%
Perineum	1%

The Digestive System

Stomach Cells and Digestion

The stomach contains specialized cells for digestion:

• Parietal Cells: Produce hydrochloric acid (HCl).

• Chief Cells: Secrete pepsinogen (enzyme precursor).

• G Cells: Produce gastrin (hormone).

• Mucous Cells: Secrete mucus for protection.

Bile Production and Storage

• Bile: Produced by the liver, stored in the gallbladder, aids in fat digestion.

Functions of Small and Large Intestine

• Small Intestine: Main site for digestion and absorption.

• Large Intestine: Absorbs water, forms feces.

Order of food travel:

1. Mouth

2. Pharynx

3. Esophagus

4. Stomach

5. Small Intestine (duodenum, jejunum, ileum)

6. Large Intestine (cecum, colon, rectum)

7. Anus

Sphincters: Muscular rings that control passage of food (e.g., pyloric, ileocecal).

Digestive Enzymes and Locations

Enzyme	Substrate	Location
Amylase	Carbohydrates	Mouth, pancreas
Pepsin	Proteins	Stomach
Lipase	Fats	Pancreas, small intestine

Terminology Review

Review all key terms and definitions as outlined in class materials for comprehensive understanding.

Study Tips

• Scan chapters, then review content, tables, and figures.

• Focus on important parts emphasized in lectures.

• Study in groups if helpful.

• Complete all online assignments before the exam.

• Communicate with course instructors as needed.

• Watch associated videos and pace your studying.

Example: The femur is a long bone in the appendicular skeleton, providing support and facilitating movement.

Additional info: Academic context was added to expand brief points into full explanations and to logically group fragmented topics for clarity and completeness.