Cells, Tissues and Skin Review

Importance of Understanding Cells

• Fundamental for comprehending human anatomy and physiology.
• All body functions depend on individual and combined activities of cells.
• Key role in homeostasis, with disease processes occurring at cellular level.

Levels of Structural Complexity

• Microscopic Level: Atoms, Organelle, Cell.
• Chemical Level: Molecules & Macromolecules.
• Tissue: Combination of cells.
• Organ: Group of tissues.
• Organism: Complete living entity.
• Organ System: Related organs functioning together.

Learning Objectives

1. Identify cellular organelles and their functions.
2. Describe plasma membrane structure and selective permeability.
3. Explain transport processes: simple diffusion, facilitated diffusion, osmosis, active transport.
4. Describe resting membrane potential and its maintenance.
5. Identify four primary tissue types and their functions.
6. Describe skin structure and functions.
7. Explain tissue repair mechanisms.

Cellular Organelles

• Common Features:
  • Plasma membrane, cytoplasm, nucleus.
  • Organelles: perform specific functions for cell specialization.
• Key Organelles:
  • Nucleus: Control center, houses DNA.
  • Ribosomes: Protein synthesis.
  • Endoplasmic Reticulum: Synthesizes/stores proteins and lipids.
  • Golgi Apparatus: Modifies, packages proteins and lipids.
  • Mitochondria: Powerhouse, produces ATP through cellular respiration.
  • Lysosomes: Digests biological material and recycles molecules.

Plasma Membrane Structure

• Composed of phospholipid bilayer:
  • Phosphate heads: hydrophilic.
  • Lipid tails: hydrophobic.
• Selectively permeable, allowing specific substances to cross.
• Contains integral and peripheral proteins for transport functions.

Transport Processes

• Passive Transport: No energy needed; includes simple diffusion, facilitated diffusion, and osmosis.
• Active Transport: Requires ATP; substances move against concentration gradient (e.g., Na+/K+ pump).
• Types of Diffusion:
  • Simple Diffusion: Lipid-soluble substances.
  • Facilitated Diffusion: Large or lipid-insoluble substances via proteins.
  • Osmosis: Water movement across membranes.

Tonicity

• Isotonic: No change in cell size.
• Hypertonic: Cell shrinks.
• Hypotonic: Cell swells; can burst.

Resting Membrane Potential

• Charge difference across membrane due to ion distribution.
• Sodium (Na+) & potassium (K+) concentration gradients established by pumps.
• Average RMP is -70 mV.

Tissue Types and Functions

1. Nervous Tissue: Communication; includes neurons.
2. Muscle Tissue: Movement; types include skeletal, cardiac, and smooth.
3. Epithelial Tissue: Protection, absorption, secretion, and filtration.
4. Connective Tissue: Supports and binds tissues; includes diverse types like bone, blood, and cartilage.

Skin Structure and Functions

• Composed of 4 primary tissues: epithelial, connective, smooth muscle, and nervous.
• Three main regions:
  • Epidermis: Protective layer.
  • Dermis: Contains blood vessels, nerves, and glands.
  • Hypodermis: Connective/adipose tissue anchoring skin.
• Functions: sensation, protection, metabolic functions, and thermoregulation.

Tissue Repair

• Involves inflammation, organization, and maturation.
• Minor wounds involve epidermis; major wounds affect both epidermis and dermis.
• Stages:
  1. Inflammation: prepares wound for repair.
  2. Organization: restores blood supply and collagen synthesis.
  3. Maturation: remodels collagen, returns to normal appearance or fibrosis.