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Introduction to Tissues: Types and Organization

This chapter defines the four major tissue types - epithelium, connective, muscle, and nervous - and explores their characteristics, organization, and subcategories. It also discusses the different modes and types of secretion in glandular epithelium and the characteristics of connective tissue.

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Introduction to Tissues: Types and Organization

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  1. Chapter 4 Tissues

  2. Organization of Tissues Types There are four major tissue types: Epithelium Connective Muscle Nervous

  3. Characteristics of Epithelial tissue • High cellularity - lots of densely packed cells with … • Specialized intercellular contacts - such as tight junctions, desmosomes and gap junctions. • Basement membranes & other c.t. support - anchors to connective tissue. • Polarity - it has an apical side and a basal side (a free edge and a fixed edge). • Avascular - no blood supply. Receive oxygen and nutrients by diffusion • Highly mitotic - cells readily regenerate.

  4. Free Surface and Attached Surface • Polarity: • apical and basolateral surfaces

  5. Intercellular Connections • Support and communication

  6. Tight Junctions • Between 2 cell membranes

  7. Gap Junctions • Allow rapid communications

  8. Desmosomes • CAMs, dense areas, and intercellular cement

  9. Attachment to Basal Lamina • Hemidesmosomes

  10. Typical arrangement of epithelium

  11. Subcategories of epithelial tissue • i. Simple • 1. squamous • 2. cuboidal • 3. columnar • ii. Stratified • 1. squamous • 2. cuboidal • 3. columnar • iii. Special (doesn’t fall neatly into either of the above) • Pseudostratified columnar • Transitional

  12. Classes of Epithelia

  13. Simple Squamous Epithelium Figure 4–3a

  14. Simple Squamous Top view Thyroid tissue Kidney

  15. Stratified Squamous Epithelium

  16. Stratified squamous

  17. Keratinizing Stratified Squamous Keratin layer of dead cells

  18. Simple Cuboidal Epithelium Figure 4–4a

  19. Simple Cuboidal Simple squamous cell Nuclei

  20. Stratified Cuboidal Epithelium Figure 4–4b

  21. Stratified Cuboidal

  22. Simple Columnar Epithelium

  23. Simple Columnar Basement membrane Goblet cells

  24. Stratified Columnar Epithelium

  25. Stratified Columnar Stratified Columnar Rare, found in the male urethra and few other places. Apical layer Basal layer

  26. Pseudostratified Columnar Epithelium

  27. Pseudostratified columnar a.

  28. Pseudostratified columnar b. Cilia

  29. Transitional Epithelium

  30. Transitional Found only in the urinary tract

  31. Glandular Epithelium: exocrine glands

  32. Modes of Secretion • Merocrine secretion – sweat glands

  33. Modes of Secretion • Apocrine secretion – mammary glands

  34. Modes of Secretion • Holocrine secretion – sebaceous (oil) glands

  35. Types of Secretions • Serous glands: • watery secretions • Mucous glands: • secrete mucins • Mixed exocrine glands: • both serous and mucous

  36. Unicellular Glands • Goblet cells are the only unicellular exocrine glands: • scattered among epithelia • e.g., in intestinal lining

  37. Structure of Multicellular Exocrine Glands • Structural classes of exocrine glands Figure 4–7 (1 of 2)

  38. Structure of Multicellular Exocrine Glands Figure 4–7 (2 of 2)

  39. Characteristics of Connective Tissue • Common developmental origin - it is all from mesoderm • Mostly well vascularized (except cartilages, tendons and ligaments) • Low cellularity - the general arrangement is a variable (often scant) number of cells in a non-living matrix. • The matrix: • fibers of protein (collagen, elastic & reticular) • ground substance (proteoglycans, cell adhesion molecules & interstitial fluid

  40. Connective tissue

  41. Subcategories of Connective tissue • i. Embryonic • 1. Mesenchyme • ii. Connective tissue proper • 1. Loose • a. Areolar • b. Adipose • c. Reticular • 2. Dense • a. Irregular (elastic or yellow) • b. Regular (white fibrous) • 3. Cartilage • a. Hyaline • b. Elastic • c. Fibrocartilage • 4. Bone (osseous) • 5. Blood

  42. Mesenchyme

  43. Loose c.t.: areolar

  44. Reticular Tissue • Provides support Figure 4–10b

  45. Loose c.t.: reticular

  46. Adipose Tissue • Contains many adipocytes (fat cells) Figure 4–10a

  47. Loose c.t.: adipose

  48. Types of Adipose Tissue • White fat: • most common • stores fat • absorbs shocks • slows heat loss (insulation)

  49. Types of Adipose Tissue • Brown fat: • more vascularized • adipocytes have many mitochondria • breaks down fat • produces heat

  50. Dense Regular Connective Tissue • Attachment and stabilization

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