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Histology The Study of Tissues. Chapter 5. Introduction. Cells are arranged in tissues that perform specialized structural and functional roles Four Major Types of Tissue: Epithelial Connective Muscle Nervous. Epithelial Tissue. General Characteristics Covers free body surfaces
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Histology The Study of Tissues Chapter 5
Introduction • Cells are arranged in tissues that perform specialized structural and functional roles • Four Major Types of Tissue: • Epithelial • Connective • Muscle • Nervous
Epithelial Tissue • General Characteristics • Covers free body surfaces • Major tissue of glands • Anchored to connective tissue by basement membrane • Lacks blood vessels • Contains little intercellular material • Replaced continuously • Functions to protect, secrete, absorb and excrete
Simple Squamous Epithelium • Single layer of thin flattened cells • Functions in the exchange of gases in the lungs and lines blood vessels and various membranes
Simple Cuboidal Epithelium • Single layer of cube-shaped cells • Carries on secretion and absorption in the kidneys and various glands
Simple Columnar Epithelium • Composed of elongated cells whose nuclei are located near the basement membranes • Lines the uterus and digestive tract • Often have absorbing cells that possess microvilli • Contains goblet cells that secrete mucus
Pseudostratified Columnar Epithelium • Appears stratified because nuclei are located at two or more levels • May have cilia that move mucus or sex cells • Lines tubes of respiratory and reproductive systems
Stratified Squamous Epithelium • Composed of many layers • Protects underlying cells • Covers the skin • Lines the mouth, throat, vagina and anal canal
Stratified Cuboidal Epithelium • Composed of two or three layers of cube-shaped cells • Lines larger ducts of the mammary glands, sweat glands, salivary glands and pancreas • Protects
Stratified Columnar Epithelium • Top layer of cells in contains elongated columns, bottom layers are cube-shaped • Found in male urethra and vas deferens • Also in parts of the pharynx • Tissue protects and secretes
Transitional Epithelium • Specialized to change under tension • In the walls of various organs of the urinary system
Glandular Epithelium • Composed of cells specialized to secrete substances • Glands consist of one or more cells • Exocrine glands secrete into ducts • Endocrine glands secrete into tissues fluid or blood • Exocrine glands classified according to the composition of their secretions • Merocrine glands secrete fluid without loss of cytoplasm • Apocrine glands lose portions of cells during secretion • Holocrine glands release cells filled with secretory products • Serous cells secrete watery fluid with high enzyme content; mucous cells secrete mucus.
Connective Tissue • General Characteristics • Connects, supports, protects, provides framework, fills spaces, stores fat, produces blood cells, protects against infection, helps repair damaged tissues. • Located some distance apart • Intercellular matrix consists of fibers and ground substances
Major Types • Fibroblast • Produces collagenous and elastic fibers • Macrophages: • Function as phagocytes • Mast cells can release heparin and histamine located near blood vessels
Connective Tissue Fibers • Collagenous fibers • Composed of collagen and have great tensile strength • Dense Connective Tissue • Tissue consisting mainly of collagenous fibers • Elastic Fibers • Composed of microfibrils embedded in elastin and are elastic • Reticular Fibers • Very fine collagenous fibers
FIBERS • Dense Connective Tissue • Reticular Fibers
Loose Fibrous Connective Tissue • Forms thin membranes between organs • Found beneath skin and between muscles
Adipose Tissue • Specialized form of loose connective tissue that stores fat • Found beneath skin, certain abdominal membranes, around kidneys, heart, and joints
Dense Fibrous Connective Tissue • Composed of strong collagenous fibers • Found in tendons, ligaments, white portions of the eyes and deep layer of skin
Cartilage • Provides framework • Composed of fibers and gel-like ground substance • Usually enclosed in a perichondrium • Lacks direct blood supply and is slow to heal • Major Types • Hyaline • Elastic • fibrocartilage
Bone • Contains mineral salts and collagen • Cells usually in concentric circles around osteonic canals and are interconnected by canaliculi • Active tissue that heals rapidly
Blood • Transports substances and helps maintain a stable internal environment • Composed of red cells, white cells, and platelets suspended in plasma • Formed by special tissue in the hallow parts of certain bones
Reticuloendothelial Tissue • Composed of phagocytic cells that are widely distributed throughout body • Defends the body against invasion by microorganisms
Muscle Tissue • General Characteristics • Muscle tissue contract causing tissues around them to move • Work in pairs (Extension/Flexion) • Three Types • Skeletal • Smooth • Cardiac
Skeletal Muscle Tissue • Muscles containing this tissue usually are attached to bones and controlled by conscious effort • Cells, or muscle fibers, are long and threadlike • Muscle fibers contract when stimulated by nerve action and then relax immediately.
Smooth Muscle Tissue • In the walls of hollow internal organs • Usually, it’s controlled by involuntary activity
Cardiac Muscle Tissue • Found only in the heart • Cells are joined by intercalated disks and form branched networks.
Nervous Tissue • Found in the brain, spinal cord, and peripheral nerves • Neurons (nerve cells) • Sense changes and respond with nerve impulses to other neurons or body parts • Coordinate, regulate, and integrate body activities • Neuroglial Cells • Some forms bind and support nervous tissue • Other carry on phagocytosis • Still others connect neurons to blood vessels
Neurons and Neuroglial Cells Nerve Fiber Cytoplasm Nucleus Neuroglial cell Nuclei Cell Membrane
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