Summarize the following text to main points and sub-points and make detailed explain for them:

ght angle to each other with material called (microtubule 
organizing center) (MTOC). 
 
 
      • 2 centriole at right angle to each other at each cell → centrosome.  
      • Each centriole is formed of 9 triplets of microtubule. 
      • Each triplets → 3 microtubule A, B & C. 
      • A is complete microtubule (13 protofilament) but B & C are incomplete       
          microtubule (10 protofilament) as they share in 3 protofilaments.  
 
 
 
 
 
 
 
 
 
       1- Form mitotic spindle during cell division. 
       2- Form the basal  of cilia & Flagella. 
 
 
 
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1st Year Histology 
 
 Hair like processes of highly organized microtubule. 
 Formation:  
• The centriole migrate to apical cell membrane to form the base of cilia. 
• From each triplets, 2 microtubule (A & B) grow upward to form the shaft of cilia. 
• Unorganized microtubule → Rootlet of cilia. 
 
 
1- Rootlet → unorganized microtubules. 
2- Base → similar to centriole. 
3- Shaft → 
  LM: acidophilic striation. 
  EM:  
- Formed of 9 doublet of microtubules & 2 central singlets in a protein 
sheath ( axoneme)  . ﻳﻌﻧﻲ ﻣﺣﻭﺭ
- Each doublet is 2 microtubule (A) complete & (B) incomplete. 
- From A microtubule 3 proteins arise → 
                        1- Radial spoke → to the center. 
                        2- Nexin → from A to B of another doublets. 
                        3- Dynein → 2 arms contain ATPase enzyme. 
Function: Brush away things from the surface  
                                      of the cells 
 
 
Flagella 
 The same structure as cilia  
 ( 100 µm ).  
 In human, the only cell with one flagellum is spermatozoa.  
 
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1st Year Histology 
 
LM:  Appear as bundles of fibril by silver stain. 
EM: Show 3 types: 
1- Thin filament (actin):  
• 5nm in diameter. 
• Present in 2 forms:  
             Stable in muscle cell. 
             Unstable in the ❶cell under cell membrane (exo & endocytosis)  
         ❷ associated with organelle (moving them) ❸ in mitotic cell (cleavage). 
2- Intermediate filament: 
    • 10nm in diameter. By immunecytochemical stain 
    • Types:  
          - Keratin in skin epithelium. 
          - Vimentin in cells of mesenchymal origin. 
          - Desmin in muscles. 
          - Glial in nervous tissue. 
          - Neurofilament in nerve cell. 
3- Thick filament (myosin):  
  • 15nm in diameter. (2 heavy chain & 4 light chains like golf stick)  
  • Present in muscle. 
 
 
 
 
 
 
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1st Year Histology 
 
♥ 3 types → 
            (1) Stored food :- 
                       Glycogen →  
                               LM :- not seen by H&E but appear red with best's carmine 
                                                                  & magenta with PAS. 
                               EM :- electron dense particle 2 forms →  
                                                  β rosette  & large α particle . 
               Lipid →  
                               LM :- not seen by H&E but seen by Sudan III → orange 
                                                                                     Sudan black → black 
                               EM :- Electron lucent vacules. 
               Secretion granules →  
                        Include mucous droplets & certain hormones 
 
           (2) Pigments:-      Endogenous pigment 
 
                 Lipofuscin 
                 Melanin 
             Hemoglobin 
        Yellow brown 
    Present in 
neuron & Cardiac 
muscle. 
↑ with age 
Black in color 
present in skin  
& retina 
     Protect body 
from UV ray of the 
sun. 
 
 
     Red in color  
present in RBC 
         most important  
       pigment. 
 
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1st Year Histology 
                                       Exogenous pigment 
 
Carbon 
Carotene 
 black color 
 With smoking in lung or 
Tatoo in skin. 
 orange color 
 present in Vitamin A rich 
food as carrot. 
 
           (3) Crystals:- Present in some cells as sertoli cell of testis. 
 
 
 
 
 
 
 Colloid substance in which (organelle, inclusion & cytoskeleton) are 
suspended. 
 Form 50% of cell volume. 
 Function → 
1- Coordinate movement of Organelle. 
2- Contain enzyme that share in metabolism. 
3- Transport signals from cell membrane to sites inside the cell. 
4- Provide viscosity of cytoplasm. 
 
 
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1st Year Histology 
 
 The most prominent structure in the cell. 
 
  
- Shape → Rounded, Oval, flat, lobulaled & irreqular. 
- Size → Small, medium & large. 
- Site → central, peripheral, apical, Basal & eccentric. 
- Stain→deep basophilic(inactive cell)& vesicular basophlic(active cells) 
- Number → usually single nucleus  - 2 nuclei in liver cell  
         mullinucleated in muscle cell -No nuclei in RBC's  not true cell. 
 
 
                                      4 Companents:  
                                   A- Nuclear envelope.                  
 
                     B- Nucleolus. 
                C- chromatin.                       
 
                       D- Nuclear matrix. 
 
 
 
 
 
(A) Chromatin 
          ♥ DNA + Histone protein → chromatin. 
          ♥ Coiled chromatin → chromatid. 
          ♥ 2 chromatid = chromosome. 
          ♥ In non-dividing cell, DNA present in the form of chromatin. 
 
 
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1st Year Histology 
 
          ♥ 2 types of chromatin: 
Eu chromatin 
Hetero chromatin 
- active DNA 
- Inactive DNA  
 - Extended uncoiled 
- Highly coiled  
- LM: Light basophilic (vesicular) 
- Deep basophilic  
- EM: Electron lucent granule. 
- Electron dense granule. 
- 3 types: Peripheral 
               Nucleolus associated 
                Islets  
 
(B) Nuclear envelope: 
 It's 2 unit membrane (inner & outer), separated by a space called (perinuclear     
                  space) or (intermembranous space) 40-70 nm. 
 
 The 2 membrane fuse together at certain points to form (nuclear pore) that     
                          connect between nucleus & cytoplasm.  
 
1- Outer membrane: Continuous with RER.  
2- Inner membrane: Contain fibrous lamina that:- 
• Stabilize the nuclear envelope. 
• Provide a site for chromatin  
                 in non dividing cell. 
 
3- Nuclear pore: Octagonal structure: ﻟﻠﻔﻬﻡ 
  • Annulus:  8 large protein granule arranged in inner & outer ring in each 
                                                                                                         pore. 
  • Radial spoke: from 8 granules to the center of the pare. 
  • Plug: electron dense granule in the center. 
 
 
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1st Year Histology 
    • Function of nuclear pore →  
          1) Allow passage of mRNA. 
          2) Allow passage of Ions & molecules < 9 nm without energy. 
          3) Molecules > 9 nm can pass by active transport utilizing energy. 
 
 
(C) Nucleolus: 
- Spherical structure up to 1mm & contain rRNA + protein. 
- LM: intense basophilic. 
- EM: 3 component: 
1- 
Nuclear organizing region: 
          Pale area contain DNA that code for rRNA. Chromosome (13, 14, 15,   
                                                                                                          21, 22) 
2- 
Fibrillar components: (10 nm) 
Maturing ribosome , ribosomal subunit that not mature yet  & waiting to be    
                                     exported to cytoplasm. 
3- 
Granular components: (20 nm)        Mature ribosome → rRNA + protein. 
Function: rRNA synthesized in nucleolus & protein synthesized in cytoplasm  
                        then bind together & migrate to cytoplasm as mature ribosome. 
 
(D) Nuclear Matrix: 
- It fill the space between chromatin & nucleolus. 
- Contain protein, enzyme, metabolites, ions & fibril called (nucleoskeleton). 
N.B:  
Function of nucleus:  
1- Carries all genetic information. 
2- Formation of RNA. 
3- Play major role in cell cycle & cell division. 
 
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1st Year Histology 
 
 


Summary :