SGU Histology

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Anonymous
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31038
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SGU Histology
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2010-08-24 01:43:30
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Gupta 8/2010
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  1. The cell in general
    • -Surrounded by cell membrane
    • -Composed of nucleus and cytoplasm (organelles and inclusions)
    • -Cellular shape, size and structure vary
  2. Cell membrane in general
    • -8 to 10 nm in width
    • -trilaminar consisting of outer, inner electron-dense lamina and electron-lucent intermediate lamina
    • -consists of 2 leaflets of phospholipid molecules
    • -integral transmembrane protein and peripheral membrane protein associated with bilayer
  3. Glycocalyx coat
    • -glycolipid and glycprotein
    • -present in external leaflet of cell membrane
    • -protects cell from mechanical and chemical damage
  4. Functions of cell membrane
    • -selectively permeable
    • -special receptor sites for antigen recognition and immunological mechanisms (phagocytosis)
    • -special receptor sites for hormone activated cellular events
  5. Nucleus
    • -bounded by nuclear envelope, contains chromatin, nucleolus, nuclear matrix
    • -most are spherical or ovoid; can be spindle-shaped (smooth muscle), bean shaped (monocytes), or multilobulated (neutrophil leucocytes)
    • -skeletal muscle cells and osteoclasts have several nuclei
    • -mammalian erythrocytes lack nuclei
  6. Nuclear envelope
    • -consists of 2 concentric membranes separated by 25 nm-wide perinuclear space
    • -outer membrane: ribosomes, continuous with RER
    • -inner membrane: bound to membrane proteins to which specific sites of chromatin are attached
    • -interrupted by pores which provide selective and active transport between nucleus and cytoplasm
  7. Chromatin
    • -composed of DNA, basic proteins, histones/nonhistone chromosomal proteins
    • -heterochromatin: in basophilic clumps, in relatively inactive cells
    • -euchromatin: in active cells, lightly stained, uniformly dispersed
  8. Barr body
    -sex chromatin prominent in neutrophils in females
  9. Nucleolus
    • -spherical and basophilic structure
    • -prominent in cells that are actively synthesizing protein
    • -composed of DNA loops; contains rRNA genes
    • -involved in rRNA synthesis
  10. Ribosomes
    • -small electron-dense cytoplasmic particles (15-25 nm in dia.)
    • -occur as ribosome or polyribosomes
    • -occur freely in cytoplasm or with RER
    • -all cells except mammalian erythrocytes contain ribosomes
    • -function: protein synthesis
  11. Rough endoplasmic reticulum
    • -network of tubules, bounded by membranes with ribosomes
    • -aggregates of RER appear basophilic, involved in protein synthesis
    • -after ribosomes are surrounded by membrane, branches off to form secretory vesicle then goes to the lumen by exocytosis
  12. Smooth endoplasmic reticulum
    • -abundant in cells involved in lipid metabolism
    • -enzymes for synthesis of steroid hormones located on membranes of smooth ER
    • -involved in drug detoxification
    • -involved in release and recapture of calcium ion during contraction/relaxation of muscles
  13. Golgi apparatus
    • -can be stained with silver salt or osmium; appears as black network of cisternae
    • -consists of parallel membranes bounded by flattened cisternae, tubules, and vesicles
    • -function: site for accumulation, concentration, and packaging of secretory proteins into membrane bound vesicles (FedEX)
    • -function: biosynthesis of glyco-proteins/lipids, phospholipids, and neutral lipids
  14. Lysosomes
    • -membrane-bounded vesicles that contain various hydrolytic enzymes (nucleases, proteases, lipases)
    • -enzymes are synthesized in RER, transferred to golgi apparatus where modified and packaged as primary lysosomes
    • -fuse with phagocytosed material, composite structure termed secondary structure
    • -after digestion, contents of secondary lysosomes retained as lipofuscin (age pigment)
  15. Peroxisomes
    • -small membrane-bounded organelles, containing oxidase and catalase enzymes which synthesize and destroy H2O2
    • -energy derived from oxidation used for metabolic processes
    • -abundant in hepatocytes and cells of proximal convoluted tubules of kidney
    • -detoxify certain substances (i.e. ethanol); plays role in gluconeogenesis
  16. Mitochondria
    • -stained with Janus Green B in living cells
    • -chief source of energy, ATP synthesis
    • -inner membrane thrown into cristae which contains enzymes that function oxidative phosphorylation
    • -mitochondrial matrix contains DNA, ribosomes, respiratory enzymes
    • -lacking mitochondria -> muscular dystrophy
  17. Microfilaments
    • -composed mainly of actin and myosin filaments, cause cellular contraction in muscle cells
    • -form a thin sheath just below plasmalemma, associated with endocytosis, exocytosis, cell migratory activity
  18. Intermediate filaments-Keratin filaments
    • -keratin filaments provide mechanical stability by formation of desmosomes
    • -also present in keratinized epithelium for protection
  19. Intermediate filaments-Desmin
    -support muscle cells
  20. Intermediate filaments-neuro
    -support nerve cells
  21. Intermediate filaments-glial
    -supports astrocytes and neurolemmocytes (Schwann cells)
  22. Microtubules
    • -play significant role in maintenance of cell form and transport of organelles and vesicles (secretory granules)
    • -play essential role in cell division; major component of the centriole
    • -centriole comprised of 9 groups of 3 microtubules in longitudinal and parallel arrangement
  23. Cytoplasmic inclusions-glycogen
    -in liver cell and muscle, can be demonstrated by PAS reaction
  24. Cytoplasmic inclusions-lipid
    -in adipose cells, can be demonstrated with osmic acid fixation
  25. Cytoplasmic inclusions-melanin
    -in skin and pigment epithelium of retina
  26. Cytoplasmic inclusions-hemosiderin
    -result of hemoglobin degradation
  27. Cytoplasmic inclusions-lipofuscin
    • -indigestible residue of phagocytosis commonly found in cardiac muscle, liver an nerve cells
    • -pigment increases with age
  28. Tight junction
    • -found in epithelial cells, consists of irregularly anastamosing ridges (transmembrane protein) that seal neighboring cells together in a beltlike fashion
    • -constitutes a barrier to prevent passage of water soluble molecules from lumen to intercellular space
  29. Adhering junction
    • -zonula adherens: cells held together by transmembrane protein linker and bundle of actin filaments run parallel to junctional cell membrane (prominent in lining cells of intestines)
    • -desmosomes: transmembrane protein linker and intercellular electron-dense plaque, forms hairpin loop
    • -hemidesmosomes: connect the cells from extracellular matrix protein
  30. Gap junction
    • -permit direct passage of inorganic ions, water soluble molecules from cell to cell
    • -intercellular space bridged by interlocking transmembrane proteins of apposed membrane
  31. Cilia
    • -one way passage
    • -found in respiratory, male and female system
    • -surrounded by plasma membrane, composed of 9 doublet microtubules around 2 central microtubules
    • -basal body is located at the BASE of the cilia, resembling centrioles
  32. Flagellum
    • -single long cilium
    • -responsible for movement
    • -i.e. spermatozoon
  33. Microvilli
    • -cytoplasmic evagination to increase the free surface for absorption
    • -i.e. small intestines
  34. Stereocilia
    • -long, rigid microvilli
    • -i.e. hair cells of spiral organ (corti) of inner ear
  35. Epithelium
    • -consists of sheets of aggregated cells of similar type
    • -rests on basement membrane (PAS technique or silver salt staining)
    • -lamina lucida (thin, semi-transparent) + lamina densa (composed of proteoglycans, type of collagen) = subbasal lamina (composed of reticular fibers)
    • -function: protection, absorption, secretion, diffusion, strengthen membrane
  36. Simple squamous epithelium
    • -thin, flat, scale-like cells
    • -spherical or oval nucleus gives slightly bulging appearance
    • -i.e. lining of blood vessels, pleural and peritoneal cavities, pulmonary arteries, glomerular capsule
  37. Simple cuboidal epithelium
    • -cuboidal cells with centrally placed nucleus
    • -i.e. thyroid gland, collecting kidney ducts
  38. Simple columnar epithelium
    • -tall, narrow cells
    • -nucleus is oval, located near base of cell
    • -i.e. stomach, intestines, gall bladder
  39. Pseudostratified columnar epithelium
    • -single layer of cells, but because of different cell shape and nuclei location, gives impression of stratified epithelium
    • -in trachea and bronchii (ciliated form)
  40. Stratified squamous epithelium
    • -several layers of cells with most superficial cells having squamous shape
    • -i.e. skin (keratinized form - cannot see nucleus), cornea (non-keratinized)
  41. Stratified cuboidal epithelium
    • -i.e. lining of extretory ducts of glands
    • -mostly 2 layers
  42. Stratified columnar epithelium
    -i.e. in parotid and mandibular gland ducts
  43. Transitional epithelium
    • -lines certain hollow organs, capable of considerable distension
    • -i.e. urinary bladder and urethra
    • -in relaxed state, superficial cells are dome-shaped and bulge into lumen
    • -when stretched, reduced to only few layers of flattened cells
  44. Glands in general
    -consists of glandular or secretory epithelium and duct system (parenchyma) with supportive framework of connective tissue (stroma)
  45. Classification of glands
    • -unicellular and multicellular glands
    • -endocrine (ductless gland, secretion released into intercellular fluid and transported to site of action by blood) and exocrine (duct system)
    • -simple or compound gland
  46. Goblet cells
    • -produces mucous
    • -unicellular
  47. Simple straight tubular
    -i.e. large intestine
  48. Simple coiled tubular
    i.e. sweat glands
  49. Simple branched tubular
    -i.e. stomach
  50. Simple alveolar or acinar gland
    -i.e. sebaceous gland
  51. Simple branched acinar or alveolar gland
    -i.e. large sebaceous gland
  52. Simple tubulo-acinar gland
    -i.e. minor salivary gland of oral cavity
  53. Compound alveolar or acinar
    -i.e. parotid gland
  54. Compound tubulo-alveolar
    -i.e. pancreas
  55. Duct system
    • -intralobular (striated in salivary glands and intercalated ducts in pancreas)
    • -interlobular
    • -lobar ducts
    • -main ducts
  56. Serous glands
    • -produce thin, watery secretion
    • -spherical nuclei in center or lower half and their apical cytoplasm is filled with small secretory granules
    • -i.e. parotid salivary gland
  57. Mucous glands
    • -produce thick, viscous secretion that form a protective covering
    • -stain lightly with H&E because of mucin
    • -nuclei are flattened and displaced towards basal part of cell
  58. Seromucous or mixed
    • -both have serous an mucous acini
    • -serous cells are located over the mucous acini as serous demilunes
    • -i.e. in the mandibular salivary gland
  59. Merocrine
    • -secretory granules enclosed in a membrane
    • -discharged by exocytosis
  60. Apocrine
    • -membrane-bounded granule
    • -together with a rim of cytoplasm and plasmalemma is released from the APEX of the cell
    • -i.e. sweat and mammary glands
  61. Holocrine
    • -entire cell is released as the secretory product (highly dividing)
    • -i.e. sebaceous glands
  62. Cytocrine
    • -secretory material from one cell is transferred from one cell to the cytoplasm of another cell
    • -i.e. transfer of melanin pigment from melanocytes into keratinocytes
  63. Myoepithelial cells
    • -interposed between the secretory cells and basement membrane
    • -when contracted, these cells force the secretory product into the duct system

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