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TISSUE: THE LIVING FABRIC Tissue: group of cells that are similar in structure and function Histology: study of tissues Types of Tissues: 1. Epithelium (covering) 2. Connective (support) 3. Muscle (movement) 4. Nervous (control) Part I: Epithelial Tissue Epithelial Tissue “epithe” = laid on, covering Structure: 1. Covering and lining epithelium 2. Glandular epithelium Function: Protection Absorption Filtration Secretion Special Properties 1. Polarity Apical surface = exposed free surface or edge (some with microvilli, cilia) Basal surface = lower, attached surface 2. Specialized contacts Fits close together to form continuous sheets Special Properties 3. Supported by connective tissue Rests on basement membrane 4. No blood supply (avascular) Rely on diffusion and underlying connective tissue for food/O2 5. Regeneration – Replace lost cells Classification Two names = (# cell layers) + (shape of cells) Cell Layers: simple or stratified Shapes: squamous, cuboidal, or columnar Simple Epithelium Absorption, secretion, filtration Very thin Simple Epithelium Simple Epithelium Simple squamous Filtration, rapid diffusion Capillary walls, air sacs in lungs, kidney filtration Serous membranes: slick layer lining ventral body cavity and its organs Simple Epithelium Simple cuboidal Secretion & absorption Lines ducts of glands (salivary), kidney tubules, ovary surface Simple Epithelium Simple columnar Absorption and secretion Lines digestive tract Microvilli, cilia Mucous membranes: lubricating mucus Simple Epithelium Pseudostratified columnar Rests on basement membrane – false impression (pseudo) of being multi-layered Secretes or absorbs Respiratory tract – cilia propels mucus from lungs Stratified Epithelium 2+ layers, more durable Main function = protect Stratified Epithelium Stratified squamous Withstand abuse, friction Esophagus, mouth, outer portion of skin Stratified Epithelium Stratified cuboidal Usually 2 layers Mainly in ducts of large glands (sweat, mammary, salivary) Sweat Gland Esophageal Gland Stratified Epithelium Stratified columnar Thick, waterproof layer Pharynx, male urethra, lining ducts Transitional Epithelium Able to change shape (cuboidal squamous) Lining of hollow urinary organs (bladder, ureter, urethra) Stretches when filled with urine Glandular Epithelium Gland: make and secrete a particular product 2 Types: Endocrine gland: produce hormones secreted into tissue fluid or bloodstream Exocrine gland: secrete products into ducts onto body surfaces or body cavities Eg. mucous, sweat, oil, saliva, bile Exocrine Glands Unicellular Multicellular Mucus cells or goblet cells Duct structure Part II: Connective Tissue Connective Tissue Most abundant and widely distributed tissue Main classes: Connective tissue proper (loose & dense) 2. Cartilage 3. Bone 4. Blood 1. Functions: Binding and support 2. Protection 3. Insulation 4. Transport substances 1. Classification Variations in blood supply Avascular (no blood) – cartilage Poorly vascular – tendons, ligaments Extracellular matrix Produced by cells, secreted to exterior Ground substance: “glue” - fills space between cells & fibers water + adhesion proteins + polysaccharides Fibers: provide support Collagen - strength Elastic – stretch Reticular – fine network, “skeleton” of organs Loose Connective Tissue Universal packing material Subclasses: areolar, adipose, reticular Structure: softer, fewer fibers, gel-like matrix Functions: Cushion & protect organs (areolar, fat) Store nutrients (fat) Internal framework (reticular) Fight infection (areolar) Cells: fibroblasts, adipocytes (fat cells) Locations: under skin, lymph nodes, hips, behind eyeballs Dense Connective Tissue Tendons & ligaments Subclasses: dense regular, dense irregular, elastic Structure: mainly collagen fibers Functions: Elastic Resist tension Cells: fibroblasts Locations: tendons (muscle-bone), ligaments (bone-bone), lower layers of skin Cartilage Subclasses: hyaline, elastic, fibrocartilage Structure: flexible, no nerves or blood Functions: Support Compression Cells: chondroblasts, chondrocytes Locations: larynx, joints, tip of nose, ear, intervertebral discs, rib-breastbone, knee joint Bone Osseous tissue Subclasses: compact, spongy Structure: hard, calcified matrix; blood vessels Functions: support & protect Store calcium Blood cell formation (marrow) Cells: osteoblasts, osteocytes Locations: bones Blood Vascular tissue Subclasses: blood cells, plasma Structure: fluid within blood vessels, no fibers Functions: Transport vehicle (nutrients, wastes, gases, hormones) Cells: white blood cells (leukocytes), red blood cells (erythrocytes), platelets Locations: blood vessels Part III: Muscle Tissue 3 types: Skeletal muscle Cardiac muscle Smooth muscle Skeletal Muscle Description: Long, cylindrical Multinucleate (2+ nuclei) Striated (banded appearance) Function: Muscles contract, pull on bones or skin cause body movements Location in the body: Attached to skeleton Other features: Voluntary control Cardiac Muscle Description: Striated Uninucleate (1 nucleus) Branching cells – fit at junctions called intercalated discs Function: Propel blood through blood vessels to all parts of body Locations in the body: Walls of the heart Other features: Involuntary control Smooth Muscle Description: No visible striations 1 central nucleus Spindle-shaped (pointed ends) Function: Propel substances through hollow organs Locations in the body: Walls of organs (stomach, bladder, uterus, blood vessels) Other features: Involuntary control Contracts slowly Peristalsis: wavelike motion that moves food through SI Part IV: Nervous Tissue Main component of nervous system Structure: neuron = dendrite + cell body + axon Function: regulates and controls body functions Location in the body: brain, spinal cord, nerves Part IV: Nervous Tissue 2 Major Cell Types: Neurons Respond to stimuli Transmit electrical impulses Other cells Support, insulate, protect neurons