Mechanism Of Disease

UNIT

One
Mechanisms of Disease

CHAPTER

1
Cell Structure and Function
Functional Components of the Cell The Nucleus The Cytoplasm and Its Organelles
Ribosomes Endoplasmic Reticulum Golgi Complex Lysosomes and Peroxisomes Mitochondria

Signal Transduction and Cell Communication
Cell Membrane Receptors Messenger-Mediated Control of Nuclear Function

Membrane Potentials
ElectricalPotentials Action Potentials

The Cytoskeleton
Microtubules Microfilaments

Body Tissues Cell Differentiation Embryonic Origin of Tissue Types Epithelial Tissue
Simple Epithelium Stratified and Pseudostratified Epithelium Glandular Epithelium

The Cell Membrane Cell Metabolism and Energy Sources Anaerobic Metabolism Aerobic Metabolism Cell Membrane Transport, Signal Transduction, andGeneration of Membrane Potentials Movement Across the Cell Membrane
Passive Movement Active Transport and Cotransport Endocytosis and Exocytosis Ion Channels

Connective or Supportive Tissues
Loose Connective Tissue Dense Connective Tissue

Muscle Tissue
Skeletal Muscle Smooth Muscle

Cell Junctions and Cell-to-Cell Adhesion

he cell is the smallest functional unit that an organism can bedivided into and retain the characteristics necessary for life. Cells with similar embryonic origin or function are often organized into larger functional units called tissues. These tissues in turn combine to form the various body structures and organs. Although the cells of different tissues

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Unit One: Mechanisms of Disease

and organs vary in structure and function, certaincharacteristics are common to all cells. Cells are remarkably similar in their ability to exchange materials with their immediate environment, obtaining energy from organic nutrients, synthesizing complex molecules, and replicating themselves. Because most disease processes are initiated at the cellular level, an understanding of cell function is crucial to understanding the disease process. Somediseases affect the cells of a single organ, others affect the cells of a particular tissue type, and still others affect the cells of the entire organism.

FUNCTIONAL COMPONENTS OF THE CELL
Although diverse in their organization, all eukaryotic cells (cells with a true nucleus) have in common structures that perform unique functions. When seen under a light microscope, three major components of theeukaryotic cell become evident: the nucleus, the cytoplasm, and the cell membrane (Fig. 1-1). The internal matrix of the cell is called protoplasm. Protoplasm is composed of water, proteins, lipids, carbohydrates, and electrolytes. Water makes up 70% to 85% of the cell’s protoplasm. The second most abundant constituents (10% to 20%) of protoplasm are the cell proteins, which form cell structuresand the enzymes necessary for cellular reactions. Proteins can also be found complexed to other compounds as nucleo-

proteins, glycoproteins, and lipoproteins. Lipids comprise 2% to 3% of most cells. The most important lipids are the phospholipids and cholesterol, which are mainly insoluble in water; they combine with proteins to form the cell membrane and the membranous barriers that separatedifferent cell compartments. Some cells also contain large quantities of triglycerides. In the fat cells, triglycerides can constitute up to 95% of the total cell mass. The fat stored in these cells represents stored energy, which can be mobilized and used wherever it is needed in the body. Few carbohydrates are found in the cell, and these are used primarily for fuel. Potassium, magnesium,phosphate, sulfate, and bicarbonate ions are the major intracellular electrolytes. Small quantities of sodium, chloride, and calcium ions are also present in the cell. These electrolytes facilitate the generation and transmission of electrochemical impulses in nerve and muscle cells. Intracellular electrolytes participate in reactions that are necessary for cellular metabolism.

The Nucleus
The...