Cell Structure, Tissue Types, and Integumentary System: Study Guide (Chapters 3-5)

Chapter 3: The Cell and Its Functions

Cell Membrane Structure and Function

The cell membrane (plasma membrane) is a selectively permeable barrier that surrounds the cell, maintaining homeostasis and mediating communication with the environment.

• Structure: Composed of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates.

• Membrane Proteins: Include integral and peripheral proteins; functions include transport, signaling, and structural support.

• Cholesterol: Stabilizes membrane fluidity.

• Glycocalyx: Carbohydrate-rich area on the cell surface important for cell recognition.

Membrane Transport Mechanisms

• Passive Transport: Movement of substances without energy input.

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

  • Osmosis: Diffusion of water across a semipermeable membrane.

  • Facilitated Diffusion: Transport of substances via carrier or channel proteins.

• Active Transport: Requires energy (ATP) to move substances against their concentration gradient.

  • Sodium-potassium pump: Maintains membrane potential by pumping 3 Na+ out and 2 K+ into the cell.

• Membrane Potentials: Electrical potential difference across the membrane, essential for nerve and muscle function.

• Osmotic Conditions:

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

  • Hypotonic: Lower solute concentration outside; cell swells.

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

• Bulk Transport:

  • Exocytosis: Export of materials via vesicles.

  • Endocytosis: Import of materials (includes phagocytosis and pinocytosis).

Cell Organelles and Their Functions

• Mitochondria: Site of ATP production (cellular respiration).

• Ribosomes: Protein synthesis.

• Rough Endoplasmic Reticulum (RER): Protein synthesis and modification.

• Smooth Endoplasmic Reticulum (SER): Lipid synthesis and detoxification.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.

• Lysosomes: Digestion of cellular waste.

• Peroxisomes: Breakdown of fatty acids and detoxification.

Nucleus and Genetic Material

• Nucleus: Contains DNA; controls cell activities.

• Nucleolus: Site of ribosomal RNA synthesis.

• Chromatin: DNA-protein complex; condenses to form chromosomes during cell division.

Cell Cycle and Division

• Stages of the Cell Cycle: Interphase (G1, S, G2) and Mitotic phase (Mitosis and Cytokinesis).

• Mitosis: Division of somatic cells; produces two identical daughter cells.

• Meiosis: Division of gametes; produces four genetically unique cells.

Example: Mitosis is essential for growth and tissue repair, while meiosis is necessary for sexual reproduction.

Chapter 4: Tissues

Basic Tissue Types

The human body is composed of four basic tissue types, each with specialized functions.

• Epithelial Tissue: Covers body surfaces, lines cavities, forms glands.

• Connective Tissue: Supports, binds, and protects organs.

• Muscle Tissue: Responsible for movement.

• Nervous Tissue: Initiates and transmits electrical impulses.

Types of Epithelial Tissues

• Shapes: Squamous (flat), cuboidal (cube-shaped), columnar (tall), pseudostratified columnar (appears layered but is not).

• Arrangements: Simple (single layer), stratified (multiple layers), transitional (stretchable).

Connective Tissue

• Cell Types: Fibroblasts, adipocytes, chondrocytes, osteocytes, blood cells.

• Matrix: Ground substance and fibers (collagen, elastic, reticular).

• Types: Loose areolar, adipose, dense regular, dense irregular, hyaline cartilage, fibrocartilage, elastic cartilage, bone, blood.

Muscle Tissue

• Types: Skeletal (voluntary, striated), cardiac (involuntary, striated), smooth (involuntary, non-striated).

• Functions: Movement, posture, heat production.

Nervous Tissue

• Components: Neurons (conduct impulses), neuroglia (support cells).

• Functions: Sensory input, integration, motor output.

Chapter 5: The Integumentary System

Structure and Function of Skin

The integumentary system includes the skin and its derivatives (hair, nails, glands). It serves as a protective barrier and has multiple physiological roles.

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

Histology of the Skin

• Epidermis: Outermost layer; composed of stratified squamous epithelium.

  • Five layers (from deep to superficial):

    1. Stratum basale

    2. Stratum spinosum

    3. Stratum granulosum

    4. Stratum lucidum (only in thick skin)

    5. Stratum corneum

  • Cell types: Keratinocytes, melanocytes, Langerhans cells, Merkel cells.

• Dermis: Deeper layer; contains connective tissue, blood vessels, nerves, glands, and hair follicles.

Skin Pigments and Hair

• Skin Pigments: Melanin (produced by melanocytes), carotene, hemoglobin.

• Hair Structure: Shaft, root, follicle; growth influenced by genetics and hormones.

• Arrector Pili Muscle: Smooth muscle attached to hair follicle; causes "goosebumps."

Glands and Nails

• Cutaneous Glands: Sebaceous (oil), sweat (eccrine and apocrine), ceruminous (earwax), mammary (milk).

• Nails: Protective coverings on fingers and toes; composed of hard keratin.

Skin Cancer and Burns

• Skin Cancer Types: Basal cell carcinoma, squamous cell carcinoma, melanoma.

• ABCD Rule of Cancer: Asymmetry, Border irregularity, Color variation, Diameter >6mm.

• Burn Categories: First-degree (epidermis only), second-degree (epidermis and part of dermis), third-degree (full thickness).

• Rule of 9's: Method to estimate body surface area affected by burns.

Example: A third-degree burn on the anterior and posterior surfaces of one leg would account for 18% of total body surface area using the Rule of 9's.