Principles of Tissue and Epithelial Classification

Principles of Tissue

• Epithelial tissue, muscle tissue, nervous tissue, and connective tissue are the primary tissue types.
• Embryonic development includes the layers: endoderm, mesoderm, and ectoderm.
• Histogenesis is the process of primary germ layers differentiating into different tissues.
• Extracellular matrix is the non-living material between cells in a tissue. Key components include water, proteins, glycoproteins, proteoglycans, and polysaccharides.
• The extracellular matrix helps tissues bind together structurally and allows cellular communication through connections with integrins and the plasma membrane.

Epithelial Tissue

• Epithelial tissue is divided into membranous (covering or lining) and glandular epithelium.
• Membranous epithelium lines or covers body surfaces and cavities like serous cavities and the respiratory, digestive, and genitourinary tracts.
• Glandular epithelium consists of secretory units of endocrine or exocrine glands, producing materials.

Classification of Membranous Epithelial Tissue

• Squamous (flat), cuboidal, columnar, and pseudostratified columnar are types.
• Simple squamous, simple cuboidal, simple columnar, pseudostratified columnar, stratified squamous (with or without keratin), stratified cuboidal, and stratified columnar.
• Transitional epithelium lines hollow organs subjected to stress

Glandular Epithelium

• Specialized in secretory activities.
• Exocrine glands discharge secretions into ducts.
• Endocrine glands, also called ductless glands, discharge secretions directly into the blood or interstitial fluid

Functional Classification of Exocrine Glands

• Apocrine glands: secretion products collect near the apex of the cell and are secreted via pinching off of the cell's end (e.g., mammary glands)
• Holocrine glands: cells need to break apart to complete function (e.g., sebaceous glands)
• Merocrine glands have ducts (most numerous)

Connective Tissue

• Connective tissue functions in support, protection, transportation, and general functions.
• Connective tissue types include fibrous (loose, areolar, adipose, reticular), dense (irregular, regular), bones, cartilage (hyaline, fibrocartilage, elastic), and blood(fibrous connective tissue).

Bone Tissue

• Bone tissue is a uniquely hard and strong connective tissue, providing support, protection, attachment sites for muscles, and mineral storage.

Cartilage Tissue

• Cartilage tissue is composed of chondrocytes, is avascular, and nutrients diffuse through the matrix.
• Hyaline, fibrocartilage, and elastic are main types.

Blood Tissue

• A liquid tissue that transports substances, regulates body temperature, and regulates body pH. It contains neither ground substance nor fibers.

Muscle Tissue

• Muscle tissue types: skeletal (voluntary), smooth (involuntary), and cardiac (involuntary).

Nervous Tissue

• Nervous tissue functions in rapid regulation and integration of body activities and comprises neurons, conducting units of the system.

Tissue Repair

• Tissue repair depends on the tissue type (epithelial and connective regenerate better). Muscle and nervous tissue regenerate less effectively.

Body Membranes

• Thin tissue layers that cover surfaces, line cavities, divide spaces, and/or surround organs.
• Types include cutaneous (skin), serous, and mucous.
• Synovial membranes line joint cavities and produce synovial fluid to reduce friction.