Bio 125: Lecture 5

  1. Tissues
    groups of closely associated cells that performs related functions and are similar in structure
  2. What are the four major categories of tissues?
    • Epithelial tissue (epithelium)
    • Connective tissue
    • Nervous tissue
    • Muscular tissue
  3. Epithelial tissue (epithelium):
    sheets of cells covering body surface or lining a body cavity
  4. Connective tissue:
    • Includes C.T. proper (fats and ligaments), cartilage, bone, and blood
    • provides support
  5. Nervous tissue:
    • main components of the nervous system
    • provides control
  6. Muscular tissue:
    • includes skeletal, cardiac, and smooth muscle
    • movement
  7. To perform specific functions… the tissues are organized into
    organs such as the stomach, heart, kidneys, and lungs
  8. Histology:
    the study of tissues.
  9. Histology provides
    the structural basis for a study of organ physiology
  10. Epithelia:
    the tissue that covers the external body surface (epidermis), lines its cavities and tubules, and generally “marks off our insides from our outsides”
  11. Since glands develop from ________ _______ they are also classed as epithelium
    epithelial membranes
  12. Epithelia occur at the interfaces between two different
  13. What are five functions of epithelium?
    • protections
    • absorption
    • filtration
    • secretion
    • sensory reception
  14. Six unique characteristics of epithelial tissue:
    • Cellularity
    • Special Contacts
    • Polarity
    • Supported by connective tissue
    • Avascular but innervated
    • High regenerative capacity
  15. Cellularity-
    composed almost entirely of cells
  16. Special Contacts-
    forms continuous sheets held together by tight junctions and desmosomes
  17. Polarity-
    apical (upper free) and basal (lower attached surfaces)
  18. Supported by connective tissue-
    reticular and basal laminae (basement membrane)
  19. Avascular but innervated-
    epithelial tissue does not have blood vessels, but you may find receptor cells
  20. High regenerative capacity-
    rapidly replaces lost cells by cell division
  21. Epithelia are classified according to two criteria:
    • The arrangement or relative number of layers (first name of tissue)
    • Cell shape (last name of tissue)
  22. 2 Kinds of Arrangement:
    • simple
    • stratified
  23. simple:
    consisting of one layer of cells attached to the basement membrane
  24. stratified:
    consisting of two or more layers of cells
  25. 3 Kinds of Cell shape:
    • squamous
    • cuboidal
    • columnar
  26. squamous:
    cells wider than tall (plate-like)
  27. cuboidal:
    cells are as wide as tall (cube-like)
  28. columnar:
    cells are taller than they are wide (column-like)
  29. The nuclei of each cell…
    • squamous: flat
    • cuboidal: spherical
    • columnar: oval
  30. stratified epithelia are named according to
    the cells at the apical surface of the epithelial membrane, not those resting on the basement membrane
  31. Image Upload 1
    Simple Columnar Epithelium
  32. Image Upload 2
    Stratified Cuboidal Epithelium
  33. Pseudostratified epithelium:
    • Actually a simple columnar epithelium (one layer of cells), but… because its cells vary in height and the nuclei lie at different levels above the basement membrane… it gives a false appearance of being stratified.
    • (This epithelium is often ciliated).
  34. Transitional epithelium:
    • Stratified squamous epithelium are formed of rounded, or “plump” cells with the ability to slide over another to allow the organ to be stretched
    • Note: only found in urinary system organs… ex. Bladder
    • Found in urinary system
    • Bladder ———|
    • Uterus ———| “Stretch”
    • Urethra ———|
    • Bladder is 6-cell layers when empty and 3-cell layers when full
  35. Simple squamous epithelium:
    single layer of flat cells with disc-shaped nuclei and sparse cytoplasm
  36. Functions of simple squamous epithelium:
    Passage of material by passive diffusion and filtration and secretes lubricating substances in serosae (membranes)
  37. Endothelium (inner covering)-
    slick lining of hollow organs
  38. Mesothelium (middle covering)-
    lines peritoneal, pleural, and pericardium cavities; covers visceral organs of those cavities
  39. Location of simple squamous epithelium:
    renal corpuscles, alveoli of lungs, lining of heart, blood and lymphatic vessels, lining of ventral body cavity (serosae)
  40. Simple cuboidal epithelia-
    single layer of cube-like cells with large, spherical central nuclei
  41. Functions of simple cuboidal epithelia:
    secretion and absorption
  42. Location of simple cuboidal epithelia:
    kidney tubules, secretary portions of small glands, ovary surface
  43. Simple columnar epithelia-
    single layer of column-shaped (rectangular) cells with oval nuclei; some bear cilia at their apical surface; may contain goblet (mucus secreting) cells
  44. Functions of simple columnar epithelia:
    Absorption; secretion of mucus, ion transport, ciliated type propels mucus or reproductive cells by ciliary action
  45. Location of simple columnar epithelia:
    • non-ciliated form lines digestive tracts, gallbladder, and ducts of small glands
    • Ciliated form lines small bronchi, fallopian tubes, and uterus
  46. Pseudostratified columnar epitheliam-
    all cells originate at basement membrane; only tall cells reach the apical surface; may contain goblet cells and bear cilia; nuclei lie at varying heights within cells (gives false impression of stratification)
  47. Function of pseudostratified columnar epithelia:
    secretion of mucus; propulsion of mucus by cilia
  48. Locations of pseudostratified columnar epithelia:
    • Non-ciliated form is in ducts of male reproductive tubes and ducts of large glands
    • Ciliated form lines trachea and most of upper respiratory tract
  49. Stratified squamous epithelium:
    many layers of cells; superficial layers are squamous in shape while deeper layers of cells appear cuboidal or columnar; thickest epithelial tissue; adapted for protection
  50. Function of stratified squamous epithelium:
    protects underlying tissues in areas subject to abrasion
  51. Location of stratified squamous epithelium:
    • Keratinized forms- epidermis
    • Non-keratinized forms- lining of esophagus, mouth, and vagina
  52. Stratified cuboidal epithelium:
    generally two layers of cube-shaped cells
  53. Function of Stratified cuboidal epithelium:
  54. Location of Stratified cuboidal epithelium:
    forms largest ducts of sweat glands and forms ducts of mammary glands and salivary glands
  55. Stratified columnar epithelium:
    several layers; basal cells usually cuboidal; superficial cells elongated
  56. Function of Stratified columnar epithelium:
    protection and secretion
  57. Location of Stratified columnar epithelium:
    rarest tissue type, found in male urethra and large ducts of some glands
  58. Transitional epithelium:
    basal cells usually cuboidal or columnar; superficial cells dome-shaped or squamous; undergoes transitions in shape
  59. Function of Transitional epithelium:
    Stretches and permits distention of urinary bladder causing thinning (from 6 to 3 layers when filled with urine)
  60. Location of Transitional epithelium:
    lines ureters, urinary bladder, and part of urethra
  61. Gland
    • many epithelial cells that make and secrete a product
    • The product of a gland are aqueous fluids that usually contain proteins
    • Epithelial cells forming glands are highly specialized to remove materials from the blood and to manufacture them into new materials, which they secrete (recall RER)
  62. Glands are classified by:
    • The site of release: endocrine (“internally releasing”) vs. Exocrine (“externally releasing”)
    • The relative number of cells forming the gland
  63. Exocrine glands:
    • retain their ducts, and their secretions empty through these ducts to an epithelial surface. (internal and external)
    • Local activity; diverse groups of glands
  64. Endocrine glands:
    • lose their surface connection (duct) as they develop; thus they are referred to as “ductless glands”
    • Secrete hormones directly into the blood or lymphatic vessels that weave through the glands to specific target organs far from the site of release
  65. Unicellular:
    scattered within epithelial sheets
  66. Multicellular:
    formed by invaginations or evaginations and usually have ducts tube-like connections to epithelial sheets) that carry products of exocrine glands to epithelial surface
  67. Unicellular Exocrine Glands (The Goblet cell):
    • Scattered throughout epithelial lining of intestines and respiratory tubes, between columnar cells
    • Goblet cells produce mucin, glycoprotein that dissolved H2O to become slimy (mucin + water = mucus); covers, protects, and lubricates many internal body surfaces
  68. Multicellular Exocrine Glands have two basic parts:
    • Secretory unit
    • Epithelium-walled duct
  69. Classified by structure of duct:
    • Simple (unbranched)
    • Compound (branched)
  70. Categorized by secretory unit structure:
    • Tubular (secretory cells form tubes)
    • alveolar= acinar (secretory cells form small flask-like sacs)
    • Tubuloalveolar (secretory cells form tubular and alveolar units)
  71. KNOW THIS FOR MIDTERM; Understand chart
    Image Upload 3
  72. Three factors act to bind epithelial cells to another:
    • Adhesion proteins in the plasma membranes link together adjacent cells
    • The wavy contours of the membranes of adjacent cells (tongue and groove)
    • Special cell junctions
  73. Tight junctions (zonula occludens):
    • A belt-like junctions that extends around periphery (apical region)
    • Closes off extracellular space
    • Some proteins in plasma membrane of adjacent cells are fused… preventing molecules from passing between cells of epithelial tissue
  74. Adherens junctions (zonula adherens):
    • An anchoring junction just below tight junctions
    • Transmembrane linker proteins attach to actin microfilaments of the cytoskeleton and bind adjacent cells
    • With tight junctions, form the tight junctional complex around apical lateral borders of epithelial tissues
  75. Desosomes (“anchoring junctions”):
    • The main junctions for binding cells together
    • Two disc-like plaques connected across intercellular space
    • Plaques of adjoining cells are joined by proteins called cadherins
    • Proteins interdigitate into extracellular space
    • Intermediate filaments insert plaques from cytoplasmic side
  76. Gap junctions (nexus):
    • Tunnel-like passageway between two adjacent cells (anywhere)
    • Let small molecules move directly between neighboring cells
    • Cells are connected by hollow cylinders of protein (connexons)
  77. Basal lamina:
    • the border between the epithelia and the underlying C.T.
    • Non-cellular supporting sheet of proteins secreted by epithelial cells
  78. Functions of basal lamina:
    • Act as selective filter, determining which molecules from capillaries enter the epithelium
    • Acts as scaffolding along which regenerating epithelial cells can migrate
    • The basal lamina and reticular layers of the underlying connective tissue deep to it form the basement membrane
  79. Clinical application of basal lamina:
    • In untreated cases of diabetes mellitus, the basement membranes associated with endothelium of capillaries thicken over time, probably because that take up glucose which is present in very high concentrations.
    • Thickening is especially evident in capillaries of kidneys and the retina of the eyes, making them nonfunctional. This is why kidney failure and blindness are major symptoms of diabetes
  80. microville :
    • finger-like extensions of plasma membrane
    • Maximizes surface area across which small molecules enter or leave
    • Abundant in epithelia of small intestine and kidney
  81. Cilia:
    • whip-like, highly motile extensions of apical surface membranes
    • Axoneme- a set of microtubules; contains a core of nine pairs of microtubules encircling one middle pair; each pair of microtubules arranged in a doublet
    • Movement of cilia: in coordinated waves
  82. Flagella:
    • extremely long cilia used to propel cells/ organisms
    • Example: sperm cells
    • Movement of flagella: whiplike pattern
Card Set
Bio 125: Lecture 5
Ch4 Tissues Part 1