HISTO PRELIM PRACTICAL

• Tissues: Groups of closely located cells organized to perform specific tasks.

Basic Tissue Types

• Epithelial, connective, muscle, and nervous tissues are the basic types.
• Epithelial tissue creates protective barriers, aids diffusion, consists of many tightly packed cells, covers body surfaces, and functions in protection, covering, and lining depending on its location.
• Connective tissue connects, supports, and underlies other tissues, providing a supporting framework that varies based on the connective tissue type.
• Muscle tissue contracts to enable body movement.
• Nervous tissue transmits and integrates data via the central and peripheral nervous systems.

Epithelial Tissue

• Epithelial tissue, characterized by high cellularity, covers body surfaces, lines cavities, and forms glands.
• Epithelial cells are abundant and lie close together.

Shapes of Cells

• Squamous cells are flattened cells involved in protection and diffusion, found in capillary walls and skin, and can be keratinized or non-keratinized.
• Cuboidal cells are cube-shaped cells found in kidney nephron tubules, involved in secretion and absorption.
• Columnar cells are tall, rectangular cells with cilia involved in absorption, secretion, protection, and lubrication, lining the gut tube's inner surface.

Layers

• Simple epithelium consists of one cell layer.
• Stratified epithelium consists of two or more cell layers.

Specialized Epithelial Tissues

• Transitional epithelium stretches tissues in the urinary tract.
• Keratinized stratified squamous epithelium makes up the epidermis of skin and contains a higher amount of keratin.
• Non-keratinized stratified squamous epithelium is present in regions prone to abrasion, like the oral mucosa and vaginal lining, containing less keratin.
• Pseudostratified ciliated columnar epithelium lines the trachea's inner surface, appearing falsely stratified, essentially a simple ciliated columnar epithelium.
• Endothelium lines blood vessel inner surfaces, standing as a specialized name for epithelial tissue.
• Ependymal cells are located in the nervous system to line the choroid plexuses.

Cell Surfaces

The cells of epithelial tissue has three types of surfaces differentiated by their location and functional specializations:

• Basal (base), Apical (top; cilia), and Lateral (sides)

Naming Epithelial Tissue

• Shape of the cells and layer presence or number should be considered when identifying the epithelial tissue

Connective Tissue

• Connective tissue is abundant, made of cells and an extracellular matrix, differing from epithelial tissue.
• Epithelial tissue is cell-rich, whereas connective tissue has an abundant extracellular matrix composed of ground substance and noticeable protein fibers.
• When naming epithelial cells, consider the cell type and fiber.

Cell Types in Connective Tissue

• Structural cells include fibroblasts, chondroblasts, osteoblasts, and odontoblasts. Immunological cells include plasma cells, leukocytes, and eosinophils.
• Defense cells include neutrophils, mast cells, basophils, and macrophages. Energy reservoir cells include adipose cells.

Fiber Types in Connective Tissue

• Collagen fibers are the most abundant, thick, strong, flexible fibers.
• Reticular fibers are thinner than collagen fibers, forming extensive structural support networks, exclusively seen in reticular tissues.
• Elastic fibers, thinner than collagen fibers, can stretch up to 150% of their original length and are more widely distributed than reticular fibers.

Classifications of Connective Tissues

• Proper connective tissues are classified into loose and dense types.
• Loose connective tissue has thin, loosely organized fibers in viscous ground substance and contains more cells and fewer fibers.
• Dense connective tissue has densely packed fibers and further classifies into dense regular and dense irregular types with fewer cells and more fibers.
• Specialized connective tissues include cartilage made of a gelatinous mix. Bone tissue has a mineralized extracellular matrix.
• Blood is fluid connective tissue that transports gases, nutrients, and wastes throughout the body.

Muscle Tissue

• Muscle tissue is extensible and elastic, able to be stretched back to original size and shape.
• Muscle tissue cells are contractile and distinguishable by their organized bundle of cells called muscle fibers.

Types of Muscle Tissues

• Skeletal muscle enables voluntary body movement with large, cylindrical, elongated cells.
• Cardiac muscle, found in the heart wall (myocardium), provides involuntary movement coordinated through gap junctions, with cylindrical cells and intercalated discs.
• Smooth muscle provides weak, slow, involuntary movements with spindle-shaped cells, each with a central nucleus.

Nerve Tissue

• Nerve tissue is specialized for irritability and conductivity, transmitting electrical impulses with a fluid-filled extracellular space for ion and neuromediator transport.

Types of Nerve Tissue Cells

• Neurons, the main cell component, have a large cell body (soma) and long projections (axons/dendrites) for transmitting data, significantly larger than glia.
• Glia supports nerve tissue, significantly outnumbers neurons, varies by region, and appears as smaller cells surrounding neurons.