Transcript Tissues
Tissues Organized groups of cells that are similar in structure and function Tissues • Tissues are organized into organs. • Organs can contain more than one type • Four main types: – Epithelial Tissue – Connective Tissue – Muscle Tissue – Nervous Tissue Epithelial Tissue • Also called epithelium (epithe = covering) • Lining, covering, and glandular tissue of body • Functions include protection, absorption, filtration, and secretion • Special Properties: – Avascular – Reproduce rapidly – Packed together tightly Epithelial Tissues • Each epithelium has two names: – One signifies the number of cell layers : • simple epithelium (one layer of cells) • stratified epithelium (more than one layer) – The second name describes the shape of its cells • Squamous cells (flattened like fish scales) • Cuboidal cells (cube-shaped like dice) • Columnar cells (shaped like columns) Simple squamous epithelium • Single layer • Thin squamous cells resting on basement membrane • Forms serous membranes that line the body cavity • In air sacs of lungs Simple cuboidal epithelium • Single layer • Cuboidal cells resting on basement membrane • Common in glands and ducts • Forms walls of kidney tubules Simple columnar epithelium • Single layer • Columnar cells • Goblet cells that secrete mucus are in this layer • Lines digestive tract • Mucous membranes that line body cavities Pseudostratified Columnar Epithelium • Vary in height so false impression that stratified • Functions in secretion and absorption • Lines respiratory tract Stratified squamous epithelium • Most common stratified epithelium • Found in areas that receive friction, like esophagus, mouth, and skin Transitional Epithelium • Highly modified stratified squamous epithelium • Forms lining of urinary bladder, ureter, and urethra • Basal layer = columnar / cuboidal • When organ is distended (stretched) with urine, the cells flatten and become squamous-like • Allows ureter wall to stretch with greater volumes of urine Glandular Epithelium • Gland – one or more cells that make and secrete a product • Secretion – product of gland that contains proteins in aqueous solution • Endocrine gland – ductless, diffuse secretion (hormones) directly into the blood (ex: thyroid, adrenal, pituitary glands) • Exocrine gland – retain ducts, secretions empty through ducts to epithelial surface (ex: sweat glands, liver, pancreas) Connective Tissue • Connects body parts • Most abundant and widely distributed tissue • Functions include protecting, supporting, and binding together other tissues • Well vascularized (exceptions tendons, ligaments; cartilage is avascular) • Connective tissues includes cells plus extracellular matrix – nonliving substance outside cells Extracellular Matrix • Produced by connective tissue and secreted to exterior • Ground substance composed largely of water and proteins • Cell adhesion proteins allow connective tissue cells to attach to matrix fibers • The following types of connective tissue are discussed in order of most rigid to softest Bone • Bone – osseus tissue, composed of bone cells in cavities called lacunae, surrounded by hard matrix of calcium salts and collagen fibers • Protects and supports body organs Cartilage • Less hard and more flexible than bone • Chondrocyte – mature cartilage cell • Hyaline cartilage – most widespread – Abundant collagen fibers in a matrix with glassy appearance (hyalin = glass) – Forms larynx, connects ribs to sternum, covers bones to form joints – Fetus skeleton made of hyaline cartilage Hyaline Cartilage Fibrocartilage • Highly compressible • Forms disks between vertebrae Elastic Cartilage • Found in a structure with elasticity • Supports external ear Dense Connective Tissue • Also called dense fibrous tissue • Collagen fibers as main matrix element • Fibroblasts – fiber forming cells between collagen fibers • Two types: – Tendons – connect skeletal muscles to bones – Ligaments – connect bones to bones at joints • Ligaments more stretchy (more elastic fibers) than tendons Dense Fibrous Tissue Loose Connective Tissue • Softer, fewer fibers and more cells than other connective tissues except blood • Areolar tissue – most widely distributed connective tissue – Soft, pliable, “cobweb”-like tissue – Cushions and protects body organs it wraps – Provides reservoir of water and salts for surrounding tissue – site where nutrients are obtained and wastes released Areolar Tissue Loose Connective Tissue • Adipose Tissue – commonly called fat – Areolar tissue in which fat cells predominate – Insulates body and protects it from extreme T – Stored in body and cushions some organs Adipose Tissue • Oil occupies most of a fat cell’s volume and compresses the nucleus, displacing it to one side Blood • Blood – vascular tissue; consists of blood cells surrounded by a matrix called blood plasma • Atypical connective tissue • Transport vehicle for cardiovascular system Muscle Tissue • Muscle tissues are highly specialized to contract or shorten to produce movement Skeletal Muscle • Skeletal muscle tissue – skeletal muscle organs connected to the skeleton. • Controlled voluntarily • Form flesh of the body – muscular system • Contraction leads to pulling on bone or skin • Result is movement or changes in expression • Cells are long, cylindrical, multinucleate, and have obvious striations Skeletal Muscle • • • • • Long Cylindrical Multinucleate Striations Called “muscle fibers” Cardiac Muscle • Found only in the heart • Contractions lead to propelling of blood through the blood vessels • Cardiac muscle cells are uninucleate, short, branching with striations and fit tightly together at intercalated disks – Gap junctions with ion flow • Involuntarily controlled Cardiac Muscle • • • • • Cells short Striated Branching Uninucleate Intercalated Discs Smooth Muscle • Smooth muscle (Visceral Muscle) – found in walls of hollow organs (stomach, uterus, blood vessels, etc.) • Contractions lead to the organ constricting or dilating so substances are propelled • No striations, uninucleate, spindle-shaped Smooth Muscle • No striations • Uninucleate • Pointed ends (spindle shaped) Nervous Tissue • Nervous Tissue – made of cells called neurons • Neurons receive and conduct electrochemical impulses from one part of body to another • Neurons and supporting cells (insulate and protect neurons) make up the nervous system: the brain, spinal chord, and nerves • Cytoplasm drawn out in extensions allows neurons to conduct impulses long distances Neuron • Neurons in human hippocampus