Chapter 4 review

• Histology: the study of tissues; all tissues share two components: discrete population of cells and extracellular matrix (ECM)
• 4 primary tissue types: epithelial, connective, muscle, nervous.
• Epithelial tissues (epithelia)- tightly packed sheets of cells with no visible ECM; Cover and line all body surfaces and cavities.
• Connective tissue- ECM is a prominent feature for most connective tissue types; cells scattered through out, bind, support, protect, and allow for transportation of substances.
• Muscle tissue is made up of bundles of muscle fibers that contract to produce movement.
• Nervous tissues capable of generating, sending, and receiving messages, cells that support this activity also within unique ECM.
• The extracellular matrix- substances that surround cells of tissue; two main components: ground substance and protein fibers.
• Ground substance is shapeless and gel-like; contains the interstitial or extracellular fluids and specialized molecules.
• Protein fibers include collagen, elastic, and reticular fibers.
• Collagen fibers- make up 20-25% of all proteins in the body. Function-resistant to tension and pressure.
• Elastic fibers-function- allows tissues to stretch and return to resting length (elasticity).
• Reticular fibers- thin short collagen fibers-function- forms weblike structure in organs such as spleen that helps trap forgein cells.
• Cell junctions- another way cells bind to on another; 3 major types of cell junctions: tight junctions, desmosomes, and gap junctions.
• Tight junctions- hold cells closely together; space between is impermeable to movement of macromolecules; form seal around apical perimeter of cell. ex. between cell in blood vessels, skin, and urinary bladder.
• Desmosomes- increase strength of tissue but holding cells together; tissues subjected to mechanical stress.
• Gap junctions- small protein channels between adjacent cells; allow small substances to flow freely between each cells cytoplasm; inbetween cells that communicate with electrical signals (cardiac and smooth muscle cells.)
• Epithelial tissues- on every internal and external body surface; barrier between body functions include: protection, immune defenses, secretion, transport, and sensation.
• 4 types of simple epithelia: pseudostratified, squamous cuboidal , and columnar.
• Simple squamous epithelium- "fried egg" appearance. Function: diffusion of substances (oxygen, carbon dioxide), filtration. Location: air sacs of lung, kidney tubules, and lining blood vessels.
• Simple cuboidal epithelium- Functions: absorption and secretion "sweat". Location: renal tubules, ducts of many glands.
• Simple columnar epithelium- often have microvilli. Function: absorption. Location: small intestines. (more wide than tall)
• Pseudostratified ciliated columnar epithelium- only one layer think. Function: more stubstances across the surface of a cell. Location: lines nasal cavity, trachea (throat), and bronchi of lungs- respiratory system.
• stratified epithelium: function- protective barrier.
• keratinized stratified squamous epithelium- apical cellular layers are dead; filled with protein keratin; makes tissue tough and resistant to friction; location- outer layers of skin.
• Nonkeratinized stratified squamous epithelium- Function: protection. Located where surface must remain moist; locations: mouth, throat, esophagus, and vagina.
• Transitional epithelium-Function: ability to stretch without leaking. Location: only in urinary system; lines ureters, urinary bladder, and urethra.
• Glandular epithelia-glands- synthesize and secrete a product such as mucus, hormones, or enzymes.
• Endocrine- secretes hormones directly into blood stream without use of ducts. Examples are thyroid gland, ovaries, and pancreas.
• Exocrine- release products onto external surface of body or lining hollow organ. Examples are goblet cells that secretes mucus, sweat glands, and pancreas.
• Connective tissues common feature- their ECF plays an extensive role in their function vary.
• Cells of connective tissue proper- resident cells permanently inhabit tissue.
• Fibroblasts- mace ECM forms fibers.
• Adipocytes- store lipids, maintain fat.
• Mast cells- release histamine- inflammation.
• Phagocytes- phagocytize debris and pathogens; ex: macrophages and neutrophils.
• Loose connective tissue- example: areolar tissue. Location: beneath epithelium of skin, around blood vessels, and within walls of hollow organs.
• Dense irregular tissue- predominantly disorganized collagen fibers. Function: in high tension such as dermis (deep to skin) and surrounding organs and joints.
• Dense regular connective tissue:- organized into parallel collagen bundles. Function: provides resistance to tension in one plane of movement. Location: tendons and ligaments.
• Adipose tissue (fat tissue)- adipocytes can increase in size to a point where fibroblasts and ECM are scarcely visible; functions: Fat storage, insulation, shock absorption, and protection. Locations: hypodermis of skin, buttocks, belly, breasts.
• Hyaline cartilage- most abundant cartilage. Locations: on ends of bones (articular cartilage) Linking sternum to ribs, framing sections of respiratory tract, and in nose. Functions: provides tough but flexible support; absorbs shock. Two cell types: chrondroblast- forms cartilage, Chrondrocyte- mature cells; lines in a lacunae.