BIO 202 – Lecture Exam #1 Study Guide: Structural Organization, Homeostasis, Cells, Tissues, Integumentary System, and Bones

Levels of Structural Organization

Overview of Structural Hierarchy

The human body is organized into a hierarchy of structural levels, each building upon the previous. Understanding these levels is fundamental to anatomy and physiology.

• Chemical Level: Atoms and molecules form the basis of all matter. Examples include water (H2O), proteins, and DNA.

• Cellular Level: Cells are the basic units of life, such as neurons or muscle cells.

• Tissue Level: Groups of similar cells working together to perform a specific function. Examples: epithelial tissue, connective tissue.

• Organ Level: Two or more tissue types combine to form organs, such as the heart or liver.

• Organ System Level: Multiple organs working together for a common purpose, e.g., the digestive system.

• Organism Level: The complete living individual, integrating all previous levels.

Homeostasis

Maintenance of Internal Stability

Homeostasis is the process by which the body maintains a stable internal environment despite external changes. It is essential for survival and proper function.

• Negative Feedback: Reverses the original stimulus to restore balance. Example: Body temperature regulation.

• Positive Feedback: Amplifies the original stimulus. Example: Childbirth (oxytocin release).

Feedback Mechanism Components

• Stimulus: A change in the environment that disrupts homeostasis.

• Receptor: Detects the change (e.g., sensory neurons).

• Afferent Pathway: Carries the signal to the control center.

• Control Center: Processes information and determines response (often CNS or endocrine system).

• Efferent Pathway: Carries the response signal from the control center.

• Response: The action that restores balance.

Plasma Membrane

Structure and Function

The plasma membrane surrounds each cell, providing structure and regulating entry and exit of substances.

• Phospholipid Bilayer: Composed of hydrophilic heads and hydrophobic tails.

• Embedded Proteins: Facilitate transport and communication.

• Selectively Permeable: Allows certain substances to pass while restricting others.

Membrane Transport

Mechanisms of Movement Across the Membrane

Cells use various methods to transport substances across the plasma membrane, depending on energy requirements and substance size.

• Passive Transport (No ATP):

  • Diffusion: Movement of molecules from high to low concentration.

  • Facilitated Diffusion: Uses carrier proteins for transport.

  • Osmosis: Diffusion of water across a membrane.

• Active Transport (Requires ATP):

  • Endocytosis: Cell takes in substances. Types include:

    • Phagocytosis: "Cell eating" of large particles.

    • Pinocytosis: "Cell drinking" of fluids.

    • Receptor-mediated Endocytosis: Specific uptake using receptors.

  • Exocytosis: Cell expels substances.

Solutions & Tonicity

Effects of Solutions on Cells

Tonicity describes how a solution affects cell volume, based on solute concentration relative to the cell.

• Solution: Mixture of solvent (usually water) and solute (such as salt).

• Hypertonic: Higher solute concentration outside the cell; cell shrinks (crenation).

• Hypotonic: Lower solute concentration outside; cell swells and may lyse.

• Isotonic: Equal solute concentration; no net movement of water.

Epithelial Tissue

Characteristics and Functions

Epithelial tissue covers surfaces and lines cavities, providing protection and facilitating absorption and secretion.

• Polarity: Distinct apical and basal surfaces.

• Cellularity: Composed almost entirely of cells.

• Basement Membrane Attachment: Anchors tissue.

• Avascular: Lacks blood vessels; nutrients diffuse from underlying tissues.

• High Regeneration Capacity: Rapidly replaces lost cells.

Glands

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

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

Epithelial Membranes

• Serous Membranes: Line closed cavities; have visceral and parietal layers. Examples: pleura (lungs), pericardium (heart), peritoneum (abdomen).

• Mucous Membranes: Line cavities open to the exterior (e.g., respiratory tract).

• Cutaneous Membrane: The skin; protects the body.

Connective Tissue

Structure and Function

Connective tissue supports, binds, and protects other tissues and organs. It is the most abundant tissue type in the body.

• Matrix: Consists of ground substance and fibers (collagen, elastic, reticular).

• Usually Vascular: Most types have blood vessels, except cartilage.

Integumentary System

Structure and Functions

The integumentary system includes the skin and associated structures, providing protection and other vital functions.

• Epidermis: Keratinized stratified squamous epithelium.

• Cells: Keratinocytes (produce keratin), Melanocytes (produce melanin), Langerhans cells (immune function).

• Dermis: Areolar and dense irregular connective tissue.

• Hypodermis: Adipose tissue; not a true skin layer.

• Functions: Protection, temperature regulation, sensation, vitamin D synthesis.

Bone Classification

Types and Structure of Bones

Bones are classified by location and shape, and are composed of different tissue types.

• Axial Skeleton: Skull, vertebral column, rib cage.

• Appendicular Skeleton: Limbs and girdles.

• Shapes: Long (femur), Short (carpals), Flat (sternum), Irregular (vertebrae).

• Tissue Types: Compact bone (osteons), Spongy bone (trabeculae).

Functions of Bone

• Support: Framework for the body.

• Protection: Shields vital organs.

• Movement: Provides leverage for muscles.

• Mineral Storage: Stores calcium and phosphate.

• Blood Cell Formation: Occurs in red marrow.

Long Bone Anatomy

Structure of a Typical Long Bone

Long bones have distinct regions and specialized functions.

• Diaphysis: Shaft; composed of compact bone.

• Epiphysis: Ends; composed of spongy bone.

• Medullary Cavity: Hollow center; contains marrow.

• Yellow Marrow: Fat storage (in adults).

• Red Marrow: Site of blood cell formation (in flat bones in adults).

Bone Cells

• Osteoblasts: Build new bone matrix.

• Osteoclasts: Resorb (break down) bone matrix.

• Osteocytes: Maintain bone tissue.

Ossification

Bone Formation Processes

Ossification is the process of bone formation, starting from either hyaline cartilage or fibrous connective tissue.

• Endochondral Ossification: Bone forms from hyaline cartilage (most bones).

• Intramembranous Ossification: Bone forms from fibrous connective tissue (flat bones).

Hormonal Control of Calcium

Regulation of Blood Calcium Levels

Calcium levels in the blood are tightly regulated by hormones.

• Parathyroid Hormone (PTH): Increases blood Ca2+ by stimulating osteoclasts.

• Calcitonin: Decreases blood Ca2+ by stimulating osteoblasts.

Fracture Healing

Stages of Bone Repair

Bone healing occurs in four main stages after a fracture.

1. Hematoma Formation: Blood clot forms at the fracture site.

2. Fibrocartilaginous Callus: Soft callus forms, bridging the gap.

3. Bony Callus: Hard callus replaces the soft callus.

4. Bone Remodeling: Bone is reshaped to its original form.

Factors Affecting Bone Repair

• Nutrition: Adequate intake of calcium, vitamin D, and protein.

• Hormones: Growth hormone, PTH, and others influence repair.

• Age: Younger individuals heal faster.

• Blood Supply: Essential for healing.

• Physical Stress: Appropriate mechanical stress promotes bone strength.