Cytology 1 l General Histology & Biology MCQs for dental students

Cytology 1 ( cell membrane structure ) l General Histology & Biology (multiple choose question) MCQ for dental student

Histology & Biology 

Science of tissues which is concerned with microscopic structure of cells (cytology) and tissues in relation to their functions

Method For studying the structure of cells & tissues (Histology):

1-Microtechniques:

A-Techniques for preparing thin and transparent sections (Parrafin & fresh frozen section)

B- Techniques for staining sections & different components in cells (H&E) OR Special stain

2-Microscopy :

A- Light microscope = LM

B- Electron microscope = EM

CYTOLOGY

Def.

• Structural and functional unit in the body & formed of a complex structure called protoplasm

Size : Varies in the different tissue

A- Human ovum is the largest cell (150um)

B- Granule cell in the cerebellum is the smallest cell (4um) in the body

Shape 

• Varies in the different tissues & may be ( rounded, oval, stellate, squamous, cubical, polygonal, polyhedral, pyriform, or pyramidal)

Interphase Cell

• Any cell that is not dividing (Preparing For Next Division Or Lost Ability To Divide)

Composition:

1- Cell membrane.

2- Cytoplasm.

3- Inter-phase nucleus

1- Cell membrane (Plasmalemma Or Plasma Membrane)

Def.

Very thin membrane surround cell and separate it from surrounding & regulate passages of material in & out of cell

CELL MEMBRANE STRUCTURE :

L/M : 

• Very thin to be resolved = Not seen

E/M

1.                Its thickness is 9- 10 nm
2.                Appear as three parallel layer (trilamellar membrane)

A-     A-Outer & Inner dark layer (electron dense)

B-     B-Middle light layer ( electron lucent )

Function

1- Isolate cytoplasm from the external environment

2-Regulate Exchange of materials between the cell & its surrounding as sodium potassium pump

3- Endocytosis:

• A-     Phagocytosis: Internalization of solid materials inside the cell
• B-     Pinocytosis :Internalization of liquid materials inside the cell C- Receptor-mediated endocytosis

4- Exocytosis: - :Process by which the cell expels out any waste product

5- Miscellaneous functions in certain cells

• A-     Microvilli (absorptive epithelium)
• B-     Cilia (respiratory epithelium)
• C-     Flagellae (sperms).
• D-    Formation of cell junctions.
• E-      Formation of myelin sheath

Mitochondria

Definition  

Membranous cell organelle responsible for provide the cell with ATP which gives energy for the different vital activities.

Size

• 1.      Diameter: 0.5-1 μm.
• 2.      Length: A-2-4μm (rod-shaped) B-7μm (filament)

 Stain

A-     H&E: Couldn't be identified.

B-     Special stains:

2-     Iron H.: Dark blue.

3-     Janus green B (supravital stain): Green

4-     Histochemically: Reveal succinic dehydrogenase activite

2-Ribosome

Def.

Non-membranous cell organelles concerned with protein synthesis in the cell.

LM

1-Not be resolved individually by light microscope (routine stain) AS it is 20-30 nm in diameter

2- Specific stain: 

• Basic stains (hematoxilin & methylene blue): Basophilia when present in large number in cytoplasm due to phosphate groups in rRNA

E/M

1.  Electron dense granule 20-30 nm in diameter.
2.  Individual ribosome appears as an composed of two subunits (small & large subunit)
3.  Large subunit is twice the size of small.
4.  They may be held together by messenger RNA forming polyribosomes.
5.  Each ribosomal subunit is composed of ribosomal RNA (rRNA) and proteins

 see second part here