Anatomy & Physiology Study Guide: Tissues, Membranes, and Cellular Structure

Body's Extracellular Environment

The extracellular environment is the space outside the cells, filled with fluids and molecules that support cellular function.

• Composition: Includes water, electrolytes, proteins, nutrients, waste products, and extracellular matrix (ECM) components such as collagen and proteoglycans.

• Function: Provides structural support, mediates cell signaling, and facilitates the exchange of materials.

• Example: The interstitial fluid surrounding tissue cells is part of the extracellular environment.

Cell Communication Mechanisms

Cells use various mechanisms to adhere to each other and communicate, ensuring tissue integrity and coordinated function.

• Cell Adhesion: Involves cell adhesion molecules (CAMs) like cadherins and integrins that help cells stick to each other and the ECM.

• Contact Signaling: Direct physical contact between cells via membrane proteins.

• Chemical Signaling: Cells release signaling molecules (e.g., hormones, neurotransmitters) that bind to receptors on target cells.

• Electrical Signaling: In excitable tissues (e.g., nerves, muscles), electrical impulses transmit information rapidly.

• Example: Gap junctions allow ions and small molecules to pass directly between adjacent cells.

Histology and Tissue Types

Histology is the study of tissues, which are groups of similar cells performing specific functions. There are four primary tissue types in the human body.

• Definition of Tissue: A group of similar cells and their extracellular products that perform a common function.

• Definition of Histology: The microscopic study of tissue structure and function.

• Four Major Tissue Types:

  1. Epithelial Tissue

  2. Connective Tissue

  3. Muscle Tissue

  4. Nervous Tissue

Epithelial Tissue

Epithelial tissues cover body surfaces, line cavities, and form glands. They are specialized for protection, secretion, absorption, and filtration.

• Structure: Closely packed cells with minimal extracellular matrix, arranged in continuous sheets.

• Functions: Protection, absorption, secretion, excretion, and sensory reception.

• Specializations: Microvilli (increase surface area), cilia (move substances), tight junctions (prevent leakage).

• Properties: Polarity (apical and basal surfaces), avascularity (no blood vessels), high regenerative capacity.

Types of Epithelial Tissue

Epithelial tissues are classified by cell shape and number of layers.

Lab linked objective

Glands: Exocrine vs. Endocrine

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

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

• Structural Differences: Exocrine glands have ducts; endocrine glands are ductless.

Multicellular Exocrine Glands

These glands consist of multiple cells and have a more complex structure than unicellular glands.

• Structural Features: Ducts and secretory units (tubular, alveolar, or tubuloalveolar).

• Functional Features: Merocrine (secrete by exocytosis), holocrine (cell ruptures), apocrine (part of cell pinches off).

Connective Tissue

Connective tissues support, bind, and protect other tissues and organs. They have diverse structures and functions.

• Structure: Cells scattered within an abundant extracellular matrix (fibers and ground substance).

• Functions: Support, protection, insulation, storage, and transport.

• Specializations: Varying fiber types (collagen, elastic, reticular), ground substance composition, and cell types (fibroblasts, adipocytes, etc.).

Types of Connective Tissue

Lab linked objective

Connective Tissue Proper

• Loose Connective Tissue: Areolar, adipose, reticular.

• Dense Connective Tissue: Dense regular, dense irregular, elastic.

• Cartilage: Hyaline, elastic, fibrocartilage.

• Bone and Blood: Specialized connective tissues.

Membranes: Serous vs. Mucous

Body membranes are thin layers of tissue that cover surfaces, line cavities, and divide spaces or organs.

Tissue Repair and Healing

Tissue repair involves restoring tissue structure and function after injury.

• Key Processes: Inflammation, organization (formation of granulation tissue), regeneration (replacement with same tissue), and fibrosis (replacement with scar tissue).

• Variables Affecting Repair: Growth factors, extent of injury, blood supply, age, and nutrition.

• Example: Skin wound healing involves inflammation, proliferation of new cells, and remodeling.

Plasma Membrane Structure

The plasma membrane is a selectively permeable barrier that surrounds the cell, maintaining the internal environment.

• Structure: Phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates.

• Functions: Controls entry/exit of substances, cell signaling, cell recognition.

Membrane Transport Processes

Substances move across the plasma membrane via passive or active processes.

Cellular Structures and Organelles

Cells contain specialized structures (organelles) that perform distinct functions.

• Nucleus: Contains DNA, controls cell activities.

• Nucleolus: Produces ribosomes.

• Nucleolus: Dense region within the nucleus.

• Ribosome: Site of protein synthesis.

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

• Smooth Endoplasmic Reticulum (ER): Lipid synthesis, detoxification.

• Rough ER: Protein synthesis (has ribosomes attached).

• Lysosome: Digests cellular waste.

• Peroxisome: Breaks down fatty acids and detoxifies.

• Mitochondria: Produces ATP (cellular energy).

• Microtubules, Microfilaments, Intermediate Filaments: Cytoskeletal elements for structure and movement.

• Cilia and Flagella: Movement of cell or substances across cell surface.

Cell Cycle and Mitosis

The cell cycle is the series of events that cells go through as they grow and divide.

• Interphase: Cell grows, DNA replicates.

• Mitosis: Division of the nucleus; includes prophase, metaphase, anaphase, telophase.

• Cytokinesis: Division of the cytoplasm, resulting in two daughter cells.

Phases of Mitosis:

• Prophase: Chromosomes condense, spindle forms.

• Metaphase: Chromosomes align at the cell equator.

• Anaphase: Sister chromatids separate to opposite poles.

• Telophase: Nuclear envelope reforms, chromosomes decondense.

Key Equation (Osmosis Example):

Where is the flux, is the permeability coefficient, and is the concentration gradient across the membrane.

Additional info: Some content and structure were inferred and expanded for academic completeness and clarity.