tissue

• A tissue is a group of cells that have a common embryonic origin and function together to carry out specialized activities.
• Tissues can be hard (bone), semisolid (fat), or liquid (blood).
• Histology is the science that deals with the study of tissues.
• A pathologist specialized in laboratory studies of cells and tissue for diagnoses is referred to as a histologist.
• Epithelial tissues cover body surfaces and line hollow organs, body cavities, duct, and forms glands.
• Connective tissues protect, support, and bind organs.
• Epithelial tissue consists of cells arranged in continuous sheets, in either single or multiple layers, are closely packed and held tightly together, cover the body's surface, and have three major functions.
• Tight junctions are web-like strands of transmembrane proteins that fuse cells together and seal off passageways between adjacent cells.
• Epithelial tissues develop from all three germ layers.
• Desmosomes contain plaque and cadherins that extends into the intercellular space to attach adjacent cells together.
• Desmosomes prevent epidermal cells from separating under tension and cardiac muscles cells from pulling apart during contraction.
• Gap junctions connect neighboring cells via tiny fluid-filled tunnels called connexons and contain membrane proteins called connexins.
• Tight junctions help to retard the passage of substances between cells and leaking into the blood or surrounding tissues.
• Hemidesmosomes resemble half of a desmosome and do not link adjacent cells but anchor cells to the basement membrane.
• Cell junctions are contact points between the plasma membranes of tissue cells.
• Hemidesmosomes contain transmembrane glycoprotein integrin.
• Integrins attach to intermediate filaments and the protein laminin present in the basement membrane.
• In epithelial cells, adhesion belts encircle the cell.
• Plasma membranes of gap junctions are separated by a very narrow intercellular gap (space) and allow communication of cells within a tissue.
• Nervous tissue develops from ectoderm.
• Tight junctions are common in epithelial tissues of the stomach, intestines, and urinary bladder.
• All connective tissue and most muscle tissues derive from mesoderm.
• Tissues of the body develop from three primary germ layers: Ectoderm, Endoderm, and Mesoderm.
• Stores energy as fat, provides immunity, muscular, generates the physical force needed to make body structures move and generate body heat, nervous, detects changes in body and responds by generating nerve impulses.
• Desmosome plaque attaches to intermediate filaments that contain protein keratin.
• Transmembrane glycoproteins called cadherins insert into the plaque and join cells.
• Adherens junctions are a dense layer of proteins called plaque that resists separation of cells during contractile activities and are located inside of the plasma membrane attached to both membrane proteins and microfilaments of the cytoskeleton.
• Secreted mucus from nonciliated simple columnar epithelium serves as a lubricant for the lining of digestive, respiratory, reproductive and urinary tracts.
• Nonciliated simple columnar epithelium contains columnar cells with microvilli at their apical surface and goblet cells.
• Nonciliated and ciliated epithelia are two types of epithelia.
• In the respiratory tract, goblet cells are interspersed among ciliated columnar epithelia.
• Secreted mucus on the surface of ciliated simple columnar epithelium traps inhaled foreign particles.
• Nonciliated simple columnar epithelium also prevents the destruction of the stomach lining by acidic gastric juices.
• Ciliated simple columnar epithelium consists of columnar epithelial cells with cilia at the apical surface.
• Structural classification of exocrine glands includes tubuloacinar glands, acinar glands, and unicellular glands.
• Connective tissue is the most abundant and widely distributed tissues in the body with numerous functions including binding tissues together, supporting and strengthening tissue, protecting and insulating internal organs, compartmentalizing and transporting, storing energy reserves and immune responses.
• Functional classification of exocrine glands includes endocrine glands and exocrine glands.
• Tubuloacinar glands have both tubular and rounded secretory parts.
• Extracellular matrix is the material located between the cells and consists of protein fibers and ground substance.
• Connective tissue is highly vascular, supplied with nerves, and the exception is cartilage and tendon.