Cytology PDF

Cytology\ By\ Dr. Esam El-Shwihy - Light microscope - Ordinary stain - Basophilia: binding with the basic stain (hematoxylin) - Acidophilia: binding with the acidic stain (eosin) - Special stains - Electron microscope - Electron dense: dark - E...

Cytology\ By\ Dr. Esam El-Shwihy - Light microscope - Ordinary stain - Basophilia: binding with the basic stain (hematoxylin) - Acidophilia: binding with the acidic stain (eosin) - Special stains - Electron microscope - Electron dense: dark - Electron light (lucent): pale - *4- Inclusions*: They consist of *storage* forms of various *nutrients* and *pigments*. They are *not* *essential* for the *life* of the cell. - The Cytoplasm contains: - *2- Organelles:* They are the *living* active structures that are *essential* for the *life* of the cell. - Nucleus is formed of: - *1- Nuclear envelope.* - *2- Nucleolus.* - *3- Chromatin* - CELL MEMBRANE - \- All cells are bounded by a cell membrane (plasma-membrane or plasmalemma). - Functions : - 1- It maintains the *structural* *integrity* of the cell. - 2- It controls movements of substances in and out the cell (selective *permeability*). - 3- It can *recognize* antigens, foreign cells as well as altered cells. - Structure: - [Light microscope (L/M): ] - Cell membranes are *not* *visible* with the light microscope. [Molecular structure (The fluid-mosaic model) :] - The cell membrane consists mainly of: *1. Phospholipids bilayer* *2. Cholesterol* *3. Proteins*  I\) Phospholipids bilayer: \- It is formed of *double* layer. \- Each layer is formed of: Polar hydrophilic phosphate *heads* Non-polar hydrophobic *tails* of long fatty acid chains II\) Cholesterol molecules: \- They fill the *gaps* between the fatty acid *tails* and *prevent* their close *packing*. III\) Membrane Proteins: *Two* types: *[A) Integral (intrinsic) proteins:]* They are present *within* lipid dilayer. They constitutes the *fluid-mosaic model for membrane structure.* [*B) Peripheral Proteins:* ] They are associated with the *surfaces* of the bilayer. **[Cell coat (Glycocalyx)]** \- It is associated with the ***external*** surface of cell membrane. \- It consists of short chains of ***glycoprotein*** and ***glycolipids***. \- Functions: ***recognition***, ***protection*** and intercellular ***adhesions***.  **[Passage of materials across cell membrane]** 1. **[Passive transport: ]** The passage of molecules ***depends*** on their ***concentration*** gradients. ***No*** ***energy*** is needed during this process. 2. **[Active transport:]** Certain ions and molecules are transported ***against*** their ***concentration*** gradient from low concentration to higher one (e.g. sodium-potassium ***pump***). ***Energy*** is ***required*** in this process. The process is carried out by ***carrier*** ***proteins***. 3. **[Vesicle-mediated transport:]** \- The process includes either getting substances into the cell (**[endocytosis]**) or getting them out of the cell (**[exocytosis]**). **1- Endocytosis: Three forms:** ***A) Pinocytosis (cell drinking):*** The cell ***entraps*** extracellular ***fluid*** or forming the ***pinocytotic vesicle***. ***C( Phagocytosis (cell eating):*** It means cell ***eating***. It is the process of engulfing ***large*** ***particles*** e.g. bacteria, microorganisms by ***specialized*** ***cells*** known as ***phagocytes as*** ***macrophages***. ***B) Receptor mediated endocytosis:*** Specific ***receptors*** for substances (***ligands***) are located at the cell surface. Binding of a ligand to its receptor forms ligand-receptor ***complex*** in shallow ***invagination*** of cell membrane called ***coated*** ***pit***. Coated pits become deep and ***pinch*** ***off*** the cell membrane are known as ***coated*** ***vesicles***, which carry ligand-receptor complex ***into*** the ***cell***. By endosomes, receptors are ***dissociated*** from ligands by the acidic pH. ***Recycling*** of ***receptors*** to cell membrane and ***digestion*** of ***ligand*** by lysosomes occur. **2- Exocytosis:** It refers to ***release*** of cell products into the ***extracellular*** compartment.  **MITOCHONDRIA** Mitochondria are ***membranous*** organelles. **Structure:** **- L/M:** Mitochondria need ***special stains*** stained blue by ***iron*** ***haematoxylin*** and green with ***Janus*** ***green.*** **- E/M:** Each mitochondrion possesses a smooth ***outer** **membrane*** and folded ***inner** **membranes**.* The folds of the ***inner*** membrane are called ***cristae***. The large space enclosed by the inner membrane is known as the ***matrix** **space***. Protein particles *(**elementary** **particles**)* are attached to cristal membrane by a short stem. The ***heads*** of elementary particles has ***ATP*** ***synthetase*** activity. They form ATP. 1. ***The matrix space*** is filled with dense fluid composed of: 2. Enzymes of ***kreb's*** cycle (citric acid cycle). 3. ***Ribosomes***. 4. ***RNA:*** Transfer and messenger RNA. 5. ***DNA***. 6. ***Dense*** ***granules*** consisting of ***Ca+ ions***. **ENDOPLASMIC RETICULUM (ER)** - They are ***membranous*** organelles - There are two types of ER: - Both are ***continuous*** with each other. **A- Smooth Endoplasmic Reticulum (sER)** - **LM*:*** - **EM*:*** - **Function of sER:** 1. ***Detoxification*** of drugs. 2. ***Glycogen*** breakdown to glucose (glycogenolysis) and conversion of glucose into glycogen (glycogenesis). 3. ***Lipid*** synthesis 4. Regulates the calcium level essential for muscular ***contraction***. **B- Rough Endoplasmic Reticulum (rER)** - **L/M*:*** It gives ***localized*** cytoplasmic ***basophilia***. - **E/M:** It consists of an interconnecting ***network*** of membranous ***tubules***, ***vesicles*** and flattened ***sacs*** (***cisternae***). Its outer surface is studded with ***ribosomes.*** - **Functions of rER:** a. ***Secretory*** proteins. b. ***Lysosomal*** enzymes. - ***sER*** may be ***derived*** from rER. **GOLGI APPARATUS** It is a ***membranous*** cell organelle. **Structure:** - ***L/M:*** Golgi can be seen after ***special*** techniques e.g. ***silver*** - In ***secretory*** cells it is ***supranuclear***. - In ***nerve*** cells it usually forms a network ***around*** the nucleus. - ***Negative Golgi Image:*** After ***H&E*** staining in cells with ***intensely*** ***basophilic*** cytoplasm such as ***plasma*** ***cells***, Golgi apparatus appears as, clear ***unstained*** area ***near*** the ***nucleus*** called ***negative*** ***image*** of Golgi.   - ***E/M :*** a\) ***Cis-face*** (immature face) which is directed ***towards*** ***rough*** ***endoplasmic*** ***reticulum***. b\) ***Trans-face*** (mature or secretory face) is directed ***towards*** the ***plasmalemma***. - **Functions of Golgi apparatus:** ***Modification*** and ***concentration*** of the newly synthesized proteins. **LYSOSOMES** - Lysosomes are ***membranous*** cell organelles. - They constitute an intracellular ***digestive*** ***system.*** - They contain a variety of ***hydrolytic*** ***digestive*** ***enzymes.*** - Lysosomal ***enzymes*** are ***synthesized*** in ***rER*** and transported in vesicles to Golgi complex. - **Types of lysosomes:** 1. When primary lysosome interacts with ***pinocytotic*** vacuole it gives ***multivesicular* *body***. 2. When primary lysosome interacts with ***phagocytic*** vacuole it gives phagosome. 3. When primary lysosome interacts with ***autophagic*** vacuole it gives ***autophagosome***. - **Functions:** 1- Cellular ***defense*** by destruction bacteria. 2- ***Replace­ment*** of ead organelles. 3- ***Autolysis*** of tissue after death. **CENTRIOLES** - They are ***non*** ***membranous*** organelles. **L/M:** Centrioles are ***paired*** cylinders arranged ***perpendicular*** to each other located ***near*** the ***nucleus*** and are called the ***centrosome**.*  **EM** - Its wall is made up of ***nine*** ***bundles*** of ***microtubules***, each bundle consists of ***three*** microtubules (***triplets***). **Function:** 1. They form the ***mitotic*** ***spindle*** during cell division. 2. They form ***basal*** ***bodies*** of the cilia and flagella. **CILIA AND FLAGELLA** - ***Non***-***membranous*** organelles. - **Sites:** Cilia are present in some cells of ***respiratory*** system, female and male ***genital*** tracts. Flagellum is only present in the sperm in human. Each cilium or flagellum is composed of basal body and shaft (axoneme). 1. The ***basal*** ***body*** is a typical ***centriole*** (nine triplets of microtubules). 2. The ***axoneme:*** The axoneme is formed of ***outer** **nine** **doublets*** of microtubules surrounding ***central*** ***two** **singlets*** microtubules. ***Radial** **spokes*** projecting from subunit ***A*** of the doublet toward the ***central*** ***sheath***. ***Two*** ***dynein*** ***arms*** has ***ATPase*** activity radiates from ***A*** subunit to ***B*** subunit of adjacent doublet. ***Each*** ***A*** subunit has. **CELL INCLUSIONS** - Inclusions are ***non***-***living*** components of the cell they include: **I- Stored foods:** 1. ***Fat** droplets* are stored mainly in ***fat*** ***cells***. 2. ***Carbohydrates*** are stored in the form of ***glycogen*** which is ***abundant*** in ***liver*** ***cells*** and ***muscle*** ***fibers***. **II- Pigments:** \- Pigments are materials with ***natural*** ***colors*** and are classified into [two] types. ***1- Exogenous pigments: [ ]*** They enter the body from ***outside*** e.g. - ***Carotenes*** (yellowish or red pigment) are present in some ***vegetables*** as carrots and they are soluble in fat giving it its color. - ***Minerals*** e.g. ***lead*** (***blue***) & ***silver*** (***grey***). - ***Carbon:*** ***black*** particles that are prominent in the ***lung*** being phagocytosed by ***pulmonary*** ***macrophages***. - ***Tattoo***, a process by which pigments are introduced into deep layers of ***skin***. ***2- Endogenous pigments:*** - They are formed ***inside*** the body e.g. - ***Hemoglobin*** (cause ***red*** color of the blood) - ***Melanin**,* the ***dark*** ***brown*** or ***black*** pigment found in the ***skin***, ***hair*** and ***eye***. - ***Lipofuscin** **pigment**:* It is ***yellowish*** ***brown*** granules that increase with ***age***. **INTERPHASE NUCLEUS** **(Non-dividing nucleus)** 1. ***Nuclear envelope.*** 2. ***Chromatin***. 3. ***Nucleolus or nucleoli.*** 4. ***Nucleoplasm or karyoplasm.***  **NUCLEAR ENVELOPE** - It consists of two parallel membranes, each is a unite type membrane of about 7.5nm thickness separated by a 10-30nm space known as perinuclear space. - The ***inner*** nuclear membrane is associated with the ***peripheral*** ***chromatin***. - The ***outer*** nuclear membrane has ***ribosomes*** and is often ***continuous*** with rough endoplasmic reticulum (***rER***). - The nuclear envelope is not continuous, but form ***nuclear*** ***pores***. **CHROMATIN** - It is the hereditary material of the cell - In the interphase nucleus, chromatin has two forms: A\) Euchromatin (extended) which is the active form. B\) Heterochromatin (condensed) which is the inactive form. - Structure of chromatin: **NUCLEOLUS** - It is a dense ***non-*** ***membranous*** structure located in the nucleus. - It is ***observed*** only during ***interphase*** and ***disappears*** during cell ***division***. **L/M**, it is deeply ***basophilic*** due to its content of (***RNA***). **E/M**: the nucleolus consist of three distinct components, which are: - ***Pars amorpha:*** ***pale--staining*** ***centers*** with fine threads of chromatin representing ***chromosomes*** 13, 14, 15, 21 and 22 in humans ***(nucleolar organizers)*** encoding rRNA. - ***Pars fibrosa:*** Containing filaments of newly formed ***rRNA*** ***surrounding*** the fibrillar center. - ***Pars granulose*** (nucleolenema) having granular appearance and it is the site in which ***ribosomal*** ***subunits*** are assembled.  **GOOD LUCK**