Lecture: Tissues

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VASUpharm14
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Lecture: Tissues
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2010-10-03 19:57:55
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IBHS 524: Nickola exam 3
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  1. tissues
    Collections of specialized cells that perform limited, yet specific functions
  2. histology
    study of tissues
  3. List 4 Tissue types
    • 1) Neural (2%)
    • 2) Epithelial (3%)
    • 3) Connective (45%)
    • 4) muscle (50%)
  4. context: 4 tissue types
    neural
    • 2%
    • transmits information
  5. context: 4 tissue types
    epithelial
    • 3%
    • covers inside & outside & forms glands
    • epithelial =
    • epithelia (cells covering external and internal surfaces): external (Body surface and lining of involutions; communicates with outside world) - skin, GI tract, respiratory tracts, urogenital tracts; internal (Lining of cavities and blood vessels & exocrine glands; does NOT communicate with outside world) - endothelium, mesothelium
    • + glands (structures made of cells that produce secretions)
  6. 4 functions of epithelial tissue
    • 1. protection - Abrasion, dehydration, chemicals, biologicals
    • 2. transport - Absorption or Excretion, Variable Permeability; tissue specific, Barrier influenced by
    • hormones, mechanical stress
    • 3. secretion - glands
    • 4. provide sensation -large sensory nerve supply
  7. 4 characteristics of epithelia
    • 1. polarity- extracellular: apical (smooth or not) side has cilia to sweep debris in respiratory tract and microvilli is to increase surface area 20X in the digestive tract; lateral side contacts neighboring cells; basal side contacts 'underlying stuff'; basolateral side is the lower sides and bottom
    • + Intracellular: organelles
    • 2. avascular - lack blood vessels so get nutrients via diffusion or absorption from apical or basal
    • 3. regenerative - replace lost or damaged (being scraped constantly) and continual division of stem cells
    • 4. cell attachment: to attach to neighboring cells and to underlying 'stuff' via:
    • a) intercellular cement: hyaluronic acid
    • b) cell adhesion molecules - transmembrane proteins that tie the cytoskeleton (actin, microtubules) to the cytoskeleton of neighboring cells, proteins in the underlying extracellular matrix; can serve as receptors; contribute to cell junctions
    • c) cell junctions - 4 types: tight, adherens, gap, desmosomes (button and hemi)
  8. context: 4 tissue types
    connective
    • 45%
    • provides support for other tissues, transports material, energy storage
  9. 2 categories of connective tissue
    • 1. classic/proper: connects epithelium to the rest of the body
    • 2. non-classic (fluid and supporting) : bone, blood, fat, lymph, cartilage
  10. context: 2 categories of connective tissue
    classic/proper 3 components
    • 1. cells - permanent resident: fibroblasts (MOST abundant and main source of ground substance and fibers), mesenchymal cells (C.T. stem cells and in epithelium and allows for regeneration), adipocytes (for energy storage, insulations, and shock absorbers); not permanent residents/varies: melanocytes (make and store pigments called melanin), immune cells (lymphocytes and macrophages)
    • 2. ground substance - it is viscous (impedes movement), water soluble (diffusion of O2), and fill spaces between cells or cells and fibers
    • 3. fibers - 3 types: collagen, elastic, reticular
  11. context: classic/proper 3 components
    ground substance
    • composed of proteoglycans (proteins + glycosaminoglycans)
    • composition of the proteoglycans is varied in each CT type
    • with 4 types of glycosaminoglycans:
    • 1. hyaluronic acid - intracellular cement. Aggregates proteins (la brea tar pits for microbes), glue to hold cell together and impede bacteria
    • 2. chondroitin sulfate - found in cartilage
    • 3. dermatan sulfate - found in dermis
    • 4. keratan sulfate - found in cornea
  12. context: classic/proper 3 components
    fibers (3)
    • 1. collagen
    • 2. elastic
    • 3. reticular
  13. context: classic/proper 3 components: 3 types of fibers
    collagen
    • MOST abundant protein in body (35%)
    • with 40 different types of collagen molecules
    • MOST abundant fiber: it is long, straight, unbranched, resistant to unidirectional stress, braided like rope making it stronger than steel, it will be the strength of ligaments and tendons.
  14. context: classic/proper 3 components: 3 types of fibers
    elastic
    • contain protein elastin
    • it is branched and wavy fibers
    • allowing for stretching and returning to original shape
    • found in: vessels, alveoli, tendon, ligaments
    • doesn't dominate in any one structure
  15. context: classic/proper 3 components: 3 types of fibers
    reticular
    • aka fibroblasts
    • contain some protein subunits as collagen, but different arrangement
    • synthesized by these reticular/fibroblasts cells
    • function to resist forces applied from many directions
    • forms an interwoven network called stroma
    • common location/function: stabilize the functional cells (parenchyma) of organs, the position of b.v. & nerves within organs. Component of reticular tissue
  16. context: 2 categories of connective tissue of the nonclassic component
    2 systems
    • 1. blood in the circulatory system - matrix (connective tissue not bone): plasma + soluble fibers; cells: red blood cells to transport oxygen, platelets for clotting, white blood cells for immunity
    • 2. lymph in the lymphatic system - matrix: lymph + soluble fibers; cells: white blood cells (lymphocytes) hang out in lymph nodes and monitor the body for infection
  17. 6 functions of connective tissue (no exposure to outside environment)
    vascular compared to epithelial
    • 1. structural framework
    • 2. connects different types of tissues
    • 3. transports fluids/dissolved material
    • 4. protection
    • 5. storing energy
    • 6. defense
  18. context: 4 tissue types
    muscle
    • 50%
    • movement (active & passive)
  19. underlying stuff
    • basal lamina (lamina lucida, lamina densa) of the basement membrane (basal lamina + reticular lamina connective tissue)
  20. 3 classifications of CAMS (cell adhesion molecules)
    • 1. cadherins - link cytoskeletons of neighboring cells
    • 2. integrins - link the cytoskeleton to proteins in matrix
    • 3. selectins -transient cell-cell binding in bloodstream
  21. 4 types of cell junctions
    • 1. tight junctions
    • 2. adherens junctions
    • 3. gap junctions
    • 4. desmosomes
  22. context: 4 types of cell junctions
    tight junctions
    • -cell membranes of adjacent cells are tightly stitched together via interlocking proteins
    • - no passage of water or solutes between cells: depends on the junctional proteins
    • -limits movement of integral proteins
    • Location: lateral surfaces
    • ex: digestive tract, blood brain barrier
  23. context: 4 types of cell junctions
    adherens junction
    • -usually found in epithelial tissue, below a tight junction
    • - an adhesion belt (Cadherins of CAM connect a web of cytoplasmic actin in cell #1 to a web of cytoplasmic actin in cell #2; actin of adjacent cells and cells can work together) encircles neighboring cells together
    • Location: lateral surfaces
    • ex: cardiac muscle, digestive tract
  24. context: 4 types of cell junctions
    gap junctions
    • allow for movement of small molecules and ions into adjacent cells and between cell membranes (via the gap)
    • connexons: interlocking channel proteins that hold adjacent cells together at gap jxns; open to form a hydrophilic pore and allow passage of ions and small molecules
    • Location: lateral surfaces of cells that require rapid intercellular communication
    • ex: cardiac and smooth muscle, synapses
  25. context: 4 types of cell junctions
    desmosomes
    • cell subject to high mechanical stress (skin) that can stretch, bend, twist, compress
    • Dense areas: concentration of CAM + intermediate filaments of cytoskeleton
    • two types:
    • 1. button: located on lateral surface; attaches adjacent cells via cadherins
    • 2. hemi: "half desmosomes" located on basolateral surface; attaches cell to basal lamina via integrin
  26. 2 types of classification of epithelia
    • 1. shapes - flat vs cube vs column
    • 2. # of layers - one (simple: located inside body so not for protection but for diffusion of "vitals"; location: lungs and blood vessels) vs many (stratified: protection is priority; location: body surface)
  27. 4 types of epithelia cells
    • 1. squamous - simple: most delicate, for absorption or excretion; located in line blood vessel (endothelium) and body cavity (mesothelium) - that doesn't communicate with the outside
    • -stratified: increase mechanical stress, tough but need mechanical stress, tough but need to be kept moist; located in esophagus, anus, vagina + keratin = water resistance in skin.
    • 2. cuboidal - simple: limited protection due to being only one layer, absorption, secretion; located in glands and ducts
    • -stratified: RARE. more protective (where secretions can be more rough) because of more layers, absorption and secretion; located in ducts (sweat glands)
    • 3. columnar - simple: protection from chemical insult, absorption and secretion, apical side typically have microvilli; located in intestines
    • -pseudostratified: protection, absorption and secretion, apical side typically ciliated; located in bronchi
    • -stratified: RARE. protection from low pH; located in urethra (due to urine)
    • 4. transitional - tolerates repeated cycles of stretching/recoil; located in bladder (empty looks stratified, full looks simple)
  28. 2 types of Glandular epithelia (yay finally!)
    • 1. endocrine glands
    • 2. exocrine glands
  29. context: 2 types of Glandular epithelia
    endocrine glands
    • aka "ductless glands"
    • release secretions into interstitial fluid (surround fluid) --> bloodstream
    • secretions: hormones into bloodstream
    • location: thyroid, pituitary
  30. context: 2 types of Glandular epithelia
    exocrine glands
    • release secretions into ducts that open onto epithelial surface (NOT into the bloodstream)
    • enzymes enter digestive tracts, sweat, tears, milk
    • 3 classifications based on types of secretion
  31. context: exocrine glands
    3 classifications of types of secretion
    • 1. serous glands
    • 2. mucous glands
    • 3. mixed exocrine glands
  32. context: 3 classifications of exocrine glands
    serous glands
    • watery solution containing enzymes
    • ex: parotid salivary glands
  33. context: 3 classifications of exocrine glands
    mucous glands
    • secrete mucins
    • ex: submucosal gland of small intestine
  34. context: 3 classifications of exocrine glands
    mixed exocrine glands
    • contain >1 type of gland cell therefore produces 2 different secretions
    • ex: serous and mucus, submandibular salivary glands
  35. goblet cells
    • the ONLY unicellular gland with each cell producing secretions
    • located: scattered in both simple and pseudostratified columnar epithelium
    • function: secrete mucin glycoproteins for protection and lubrication
  36. 4 types of Membranes
    • membranes = epithelium + connective tissue
    • 1. mucous
    • 2. synovial
    • 3. cutaneous
    • 4. serous
  37. context: 4 types of Membranes
    mucous membranes
    • line passageways that communicate with outside digestive, respiratory, urogenital
    • protected and moisturized via mucous (thicker secretion from glands)
  38. context: 4 types of Membranes
    synovial membranes
    • decrease friction between articulating bones (joints)
    • it is lubricated by synovial fluid (ground substance)
  39. context: 4 types of Membranes
    cutaneous membranes
    • covers exterior of body surface
    • thick, dry, and water resistant
  40. context: 4 types of Membranes
    serous membranes
    • line "sealed" body cavities and covers organs to minimize friction
    • it is lubricated by transudate (thin blood)

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