ch.4

Flashcards for the Tissue Level of Organization, covering types, functions, structures, and techniques related to tissue study.

Tissue

A group of cells working together to perform a specific function.

Histology

The study of tissues.

Epithelial Tissue

Tissue that covers exposed surfaces, lines internal passageways, and forms secretory glands.

Characteristics of Epithelial Tissue

1. Avascular: Lacks blood vessels.2. Polarity: Exhibits distinct apical (free) and basal (attached) surfaces.3. Cellularity: Cells are closely packed with little extracellular material.4. Attachment: Attached to a basement membrane.5. Regeneration: High capacity for cell division and renewal.

Primary functions of Epithelial Tissue

1. Physical Protection: From abrasion, dehydration, and chemical agents.2. Control Permeability: Regulates the movement of substances into or out of the body.3. Provide Sensation: Contains sensory nerves.4. Produce Specialized Secretions: Forms glands for secretion.

Connective Tissue

Tissue that provides support, fills internal spaces, stores energy, and connects different parts of the body.

Characteristics of Connective Tissue

1. Specialized Cells: Contains various cell types.2. Extracellular Matrix: Primarily composed of protein fibers and ground substance.3. Vascularity: Generally vascularized (rich blood supply), unlike epithelium, with exceptions like cartilage.4. Never Exposed: Always covered by epithelial tissue.

Primary functions of Connective Tissue

1. Structural Framework: Establishes the body's framework.2. Transport: Moves fluids and dissolved materials.3. Protection: Protects delicate organs.4. Support & Interconnection: Supports, surrounds, and interconnects other tissues.5. Energy Storage: Stores energy, especially lipids.6. Defense: Defends the body from invading microorganisms.

Muscle Tissue

Tissue that contracts to produce movement.

Main types of Muscle Tissue and their characteristics

1. Skeletal Muscle: Striated, voluntary, responsible for moving bones.2. Cardiac Muscle: Striated, involuntary, found only in the heart wall.3. Smooth Muscle: Non-striated, involuntary, found in the walls of internal organs and blood vessels.

Nervous Tissue

Tissue that conducts electrical impulses and carries information.

Key cell types of Nervous Tissue

1. Neurons: Cells that detect stimuli, transmit electrical signals (action potentials), and communicate information.2. Neuroglia (Glial Cells): Supporting cells that protect, nourish, and insulate neurons, and maintain the chemical environment.

Microscopy

The use of microscopes to study cells and tissues.

Simple Squamous Epithelium

A single layer of flat cells that functions in absorption, diffusion, and reduction of friction.

Locations of Simple Squamous Epithelium

1. Alveoli: Air sacs of the lungs.2. Endothelium: Lining of blood vessels and lymphatic capillaries.3. Mesothelium: Serous membranes lining ventral body cavities (pericardium, pleura, peritoneum).

Cuboidal Epithelium

Epithelium consisting of cube-shaped cells, involved in secretion and absorption.

Locations of Cuboidal Epithelium

1. Glands and Ducts: Forms secretory portions of glands and their ducts.2. Kidney Tubules: Involved in filtration and reabsorption.3. Thyroid Follicles: Produces thyroid hormones.

Columnar Epithelium

Tall and slender epithelial cells that are involved in absorption and secretion.

Locations of Columnar Epithelium

1. Digestive Tract: Lining of the stomach, small and large intestines.2. Gallbladder: Lining.3. Uterine Tubes: Ciliated columnar epithelium moves oocytes.

Stratified Epithelium

Multiple layers of cells that provide protection in areas of high abrasion.

Subtypes and locations of Stratified Epithelium

1. Stratified Squamous Epithelium: Found in the skin surface (keratinized), lining of the mouth, throat, esophagus, vagina, anus (non-keratinized). Provides robust protection.2. Stratified Cuboidal Epithelium: Rare; found in ducts of sweat glands and mammary glands.3. Stratified Columnar Epithelium: Rare; found in small regions of the pharynx, epiglottis, anus, and parts of the urethra.4. Transitional Epithelium: Found in the urinary bladder, ureters, and renal pelvis; allows for significant stretching and recoiling.

Exocrine gland

Glands that secrete substances through ducts to an external surface.

Common examples of Exocrine Glands

Sweat glands, salivary glands, mammary glands, sebaceous glands, digestive glands (e.g., in the stomach and intestines).

Endocrine gland

Glands that release hormones into the interstitial fluid.

Common examples of Endocrine Glands

Thyroid gland, adrenal glands, pituitary gland, parathyroid glands, pancreas (islets of Langerhans), gonads.

Hemidesmosomes

Connections that attach epithelial cells to the basement membrane.

Tight junctions

Interlocking membrane proteins that prevent the passage of water and solutes between cells.

Desmosomes

Strong connections that provide adhesion between cells, resisting stretching and twisting.

Gap Junctions

Intercellular connections formed by connexons that allow for direct chemical and electrical communication between adjacent cells.

Adhesion Belts

Continuous bands of proteins (actin filaments) that help reinforce tight junctions, encircling epithelial cells just deep to the tight junction.

Scar tissue

A dense, collagenous framework produced during the regeneration process after tissue injury, often less functional than original tissue.