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Overview of Histology: Understanding the Four Major Tissue Types

This chapter introduces histology, focusing on the arrangement and functions of cells in tissues. It highlights the four major tissue types: epithelial, connective, muscle, and nervous. The characteristics and roles of various epithelial tissues, including simple and stratified types, are explored, along with glandular epithelia and their secretion mechanisms. Connective tissue types, including fibrous, cartilage, and bone, are described, along with their roles in support and protection. Additionally, the chapter examines muscle tissue contracting functionalities, providing a foundational understanding of tissue structure and function in the human body.

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Overview of Histology: Understanding the Four Major Tissue Types

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  1. Histology The Study of Tissues Chapter 5

  2. Introduction • Cells are arranged in tissues that perform specialized structural and functional roles • Four Major Types of Tissue: • Epithelial • Connective • Muscle • Nervous

  3. 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

  4. 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

  5. Simple Cuboidal Epithelium • Single layer of cube-shaped cells • Carries on secretion and absorption in the kidneys and various glands

  6. 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

  7. 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

  8. Stratified Squamous Epithelium • Composed of many layers • Protects underlying cells • Covers the skin • Lines the mouth, throat, vagina and anal canal

  9. 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

  10. 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

  11. Transitional Epithelium • Specialized to change under tension • In the walls of various organs of the urinary system

  12. 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.

  13. Exocrine Glands

  14. Endocrine Glands

  15. Merocrine Gland-Exocrine

  16. Apocrine Gland-Exocrine

  17. Holocrine Gland-Exocrine

  18. 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

  19. Major Types • Fibroblast • Produces collagenous and elastic fibers • Macrophages: • Function as phagocytes • Mast cells can release heparin and histamine located near blood vessels

  20. 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

  21. FIBERS • Dense Connective Tissue • Reticular Fibers

  22. Loose Fibrous Connective Tissue • Forms thin membranes between organs • Found beneath skin and between muscles

  23. Adipose Tissue • Specialized form of loose connective tissue that stores fat • Found beneath skin, certain abdominal membranes, around kidneys, heart, and joints

  24. Dense Fibrous Connective Tissue • Composed of strong collagenous fibers • Found in tendons, ligaments, white portions of the eyes and deep layer of skin

  25. 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

  26. Hyaline

  27. Elastic

  28. Fibrocartilage

  29. Bone • Contains mineral salts and collagen • Cells usually in concentric circles around osteonic canals and are interconnected by canaliculi • Active tissue that heals rapidly

  30. 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

  31. Reticuloendothelial Tissue • Composed of phagocytic cells that are widely distributed throughout body • Defends the body against invasion by microorganisms

  32. Muscle Tissue • General Characteristics • Muscle tissue contract causing tissues around them to move • Work in pairs (Extension/Flexion) • Three Types • Skeletal • Smooth • Cardiac

  33. 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.

  34. Smooth Muscle Tissue • In the walls of hollow internal organs • Usually, it’s controlled by involuntary activity

  35. Cardiac Muscle Tissue • Found only in the heart • Cells are joined by intercalated disks and form branched networks.

  36. 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

  37. Neurons and Neuroglial Cells Nerve Fiber Cytoplasm Nucleus Neuroglial cell Nuclei Cell Membrane

  38. Quiz Simple Sqamous

  39. Nervous

  40. Transitional Epithelium

  41. Hyaline Cartilage

  42. Simple Columnar

  43. Stratified Cuboidal

  44. Loose Fibrous Connective

  45. Bone

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