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Chapter 4: Tissues, Glands, & Membranes - General Definitions

This chapter provides an overview of tissues, glands, and membranes, including their definitions and characteristics. It covers the four basic types of tissues - epithelial, connective, muscle, and nervous tissues - with a focus on epithelial tissue. The classification, unique characteristics, and structural-functional relationships of epithelial tissues are discussed, along with the classification and characteristics of glandular epithelium.

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Chapter 4: Tissues, Glands, & Membranes - General Definitions

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  1. Chapter 4 Tissues, Glands, & Membranes

  2. General Definitions: • Tissue - group of cells similar structure and function along with similar extracellular substances between the cells • Histology – microscopic study of tissue structure • Histo- = tissue, -ology = study

  3. Four Basic Types of Tissues • Epithelial tissues • Epi = on + thele = covering or lining • Connective tissues • Muscle tissues • Nervous tissues

  4. Epithelial Tissue, Unique characteristics • Very little extracellular material between cells. • Free surface – layer of cells not in contact with other cells. • Basement membrane – attaches the epithelial cells to underlying tissues. • Avascular – capillaries do not extend from the underlying tissues, so gases, nutrients, & wastes must diffuse across the basement membrane.

  5. Classification of Epithelia • Classified based on number of cell layers and cell shape • Layers: • Simple epithelium – 1 layer of cells • Stratified epithelium - >1 layer of cells • Note: When epithelium is stratified, it is named according to the shape of the cells at the free surface.

  6. Classification of Epithelia • Shape: • Squamous (flat and scale-like) • Cuboidal (cube shaped) • Columnar(tall and thin)

  7. Layers or “Arrangement”

  8. Shapes

  9. Simple Squamous Epithelium • Single layer of thin, flat cells • Line blood vessels, lymphatic vessels, heart, alveoli, kidney tubules, serous membranes • Diffusion, filtration, anti-friction, secretion, absorption

  10. Simple Cuboidal Epithelium • Single layer of cube-shaped cells, some with microvilli or cilia • Kidney tubules, glands/ducts, brain, bronchioles, ovary surface • Secretion, absorption, movement of particles

  11. Simple Columnar Epithelium • Single layer of tall, narrow cells, some with cilia/microvilli • Lining of stomach, intestines, glands, ducts, bronchioles, auditory tubes, uterus, uterine tubes • Secretion, absorption, movement of particles/oocytes

  12. Pseudostratified ColumnarEpithelium • Single layer of cells, some tall and thin, others not, nuclei at different levels, appear stratified, almost always ciliated • Lining of nasal cavity, nasal sinuses, auditory tubes, pharynx, trachea, bronchi • Synthesis/ secretion/ movement of mucus

  13. Transitional Epithelium • Stratified cells appear cuboidal when not stretched and squamous when stretched • Lining of bladder, ureters, superior urethra • Deals with changing volume of fluid in an organ, protects from urine contact

  14. Let’s practice:

  15. Simple Columnar Epithelium

  16. Simple Squamous Epithelium

  17. Stratified Squamous Epithelium

  18. Simple Cuboidal Epithelium

  19. Stratified Columnar Epithelium

  20. Pseudostratified Epithelium

  21. [bladder]

  22. Transitional Epithelium

  23. Stratified Cuboidal Epithelium

  24. Structural & FunctionalRelationships • Cell Layers & Cell Shapes • Single layers – control passage of materials through epithelium • Gas diffusion across lung alveoli • Fluid filtration across kidney membranes • Gland secretion • Nutrient absorption in intestines • Multiple layers – protect underlying tissues • Damaged cells replaced by underlying cells • Protect from abrasion (ex: skin, anal canal, vagina)

  25. Structural & FunctionalRelationships • Cell Layers & Cell Shapes, continued • Flat/thin (squamous) – diffusion, filtration • Diffusion in lung alveoli • Fluid filtration in kidney tubules • Cuboidal/columnar – secretion, absorption; contain more organelles • Secretory vesicles (mucus) in stomach lining • Mucus protects against digestive enzymes and acid • Secretion/absorption in kidney tubules made possible by ATP production by multiple mitochondria • Active transport of molecules into/out of kidney

  26. Structural & Functional Relationships • Free Cell Surfaces • Smooth – reduces friction • blood vessel lining – smooth blood flow • Microvilli – increase cell surface area; cells involved in absorption or secretion • Small intestine lining • Cilia – propel materials along cell’s surface • Nasal cavity/trachea – moves dust and other materials to back of throat (swallowed/cough up) • Goblet cells secrete mucus to entrap the “junk”

  27. Structural & FunctionalRelationships • Cell Connections • Tight junctions – bind adjacent cells together • Permeability layers – prevent passage of materials • Intestinal lining and most simple epithelia • Desmosomes – anchor cells to one another • Hemidesmosomes – anchor cells to basement membrane • Epithelia subject to stress (skin stratified squamous) • Gap Junctions – allow passage of molecules/ions between adjacent cells (communication) • Most epithelia

  28. Cell Connections

  29. Glandular Epithelium • Gland – multicellular structure secreting substance onto a surface, into a cavity, or into the blood. There are two types: • Exocrine gland(exo-outside + krino-to separate): glands with ducts; secretions pass through ducts onto a surface or into an organ • Simple – ducts w/o branches • Compound – ducts w/ branches • Tubular – tubes • Acinus/alveolus – saclike • Endocrine gland(endo-within): glands w/o ducts that secrete into blood • Hormonesare secreted into blood

  30. Exocrine Gland Structures - Simple *Goblet cells are the only unicellular gland.

  31. Exocrine Gland Structures - Compound

  32. Exocrine glands Classified according to what it Releases • Merocrine: FLUID is released (Most glands are in this group) • Serous cells = produce a watery secretion w/enzymes • Mucous cells = produce thicker secretions • Apocrine: Small portions of the cell break off & are released • Mammary glands, Ceruminous (ear wax), and some sweat glands • Holocrine: ENTIRE CELLS are released-Sebaceous Glands: oil in the skin)

  33. Connective Tissue • The most abundant and widely distributed tissue in the body • Multiple types, appearances and functions • Relatively few cells in extracellular matrix (think: fruit “cells” floating or suspended in Jell-O). • Matrix is made up of: • Protein fibers • Ground substance • Fluid

  34. Structure of Connective Tissue Three types of protein fibers : • Collagen fibers: • Rope-like; resist stretching • Reticular fibers: • Fine, short collagen fibers; branched for support • Elastic fibers: • Coiled; stretch and recoil to original shape • Ground substance – combination of proteins and other molecules • Varies from fluid to semisolid to solid • Proteoglycans – protein/polysaccharide complex that traps water

  35. Collagenous Fibers

  36. Elastic Fibers & Mast Cells

  37. Reticular Connective Tissue

  38. Naming of Connective Tissue Cells • Based on function: • Blast (germ) – produce (build) matrix • Cyte (cell) – cells maintain it • Clast (break) – cells break down for remodeling • Osteoblast (osteo-bone) – form bone • Osteocyte – maintain bone • Osteoclast – break down bone • Cells associated with the immune system are also found in connective tissue: • Macrophage (makros-large + phago-to eat) – large, mobile cells that ingest foreign substances found in connective tissue • Mast Cells – nonmotile cells that release chemicals that promote inflammation

  39. Functions of Connective Tissue • Enclose & Separateorgans and tissues from one another • Liver, kidney; (capsules form around) • muscles, blood vessels, nerves • Connect tissues to each other • Tendons – muscles to bone • Remember: TTT (tendons 2 types) • Ligaments – bone to bone • Remember: LLL (ligaments like to like) • Support and movement • Bones, cartilage, joints

  40. Functions of Connective Tissue, (cont.) • Storage • Fat stores energy; bone stores calcium • Cushion and insulation • Fat cushions/protects/insulates (heat) • Transportation • Blood transports gases, nutrients, enzymes, hormones, immune cells • Protection • Immune & blood cells protect against toxins/tissue injury; bones protect underlying structures

  41. Classification of Connective Tissues

  42. Loose Connective Tissue (Areolar) • Composition: ECM has fibroblasts, other cells, collagen, fluid-filled spaces • Functions: forms thin membranes between organs and binds them (loose packing material) • Locations: widely distributed, between glands, muscles, nerves, attaches skin to tissues, superficial layer of dermis

  43. Adipose Connective Tissue • Composition: very little ECM (has collagen and elastic fibers); large adipocytes filled with lipid • Functions: Stores fat, energy source, thermal insulator, protection/ packing material • Locations: Beneath the skin, in breasts, within bones, in loose connective tissues, around organs (kidneys and heart)

  44. Dense Fibrous/Collagenous Connective Tissue • Composition: ECM mostly collagen (made by fibroblasts), orientation varies • Functions: withstands pulling forces, resists stretching in direction of fibers orientation • Locations: tendons, ligaments, dermis of skin, organ capsules

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