Cytoplasm and Cell Inclusions in Cytology

Cytology/ lec3 01/03/1439 1 Farah E. Ismaeel

The Cytoplasm The cytoplasm is the part of the cell located outside the nucleus full the space between nuclear envelop and plasma membrane consists of cytosol is a larger fluid component. 2. Organelles (little organs) are bathing metabolically active structures. (living) 3. Cytoskeleton is protein components which determine the shape and motility of eukaryotic cells. 4. Inclusions are the minor cytoplasmicstructures that are not usually surrounded by a plasma membrane. (non living) 1. 01/03/1439 2 Farah E. Ismaeel

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Cytosol Cytosol is an aqueous gel called the cytoplasmic matrix. The matrix consists of : inorganic ions (Na, K, and Ca2) organic molecules such as intermediate metabolites, carbohydrates, lipids, proteins, and RNAs. 3. contains hundreds of enzymes, such as those of the glycolytic pathway. 4. oxygen, CO2, electrolytic ions, low-molecular-weight substrates, metabolites, and waste products 1. 2. 01/03/1439 4 Farah E. Ismaeel

organelles inclusions living nonliving permanent temporary essential Not essential Active inert Have vital function Is only a result as fat All cells have it Some cells have it 01/03/1439 5 Farah E. Ismaeel

Inclusions The cytoplasmic inclusions are temporary non-living structures that accumulate in the cytoplasm of certain cells not able to carry out any metabolic activity and are not bound by membranes. Inclusions are stored nutrients, secretory products, and pigment granules. 01/03/1439 6 Farah E. Ismaeel

Example of inclusions Glycogen: Glycogen granules is the most common form of glucose in animals and is especially abundant in cells of muscles, and liver Lipids: Lipids are triglycerides in storage form is the common form of inclusions, not only are stored in specialized cells (adipocytes) but also are located as individuals droplets in various cell type especially hepatocytes. These are fluid at body temperature and appear in living cells as refractile spherical droplets. 01/03/1439 7 Farah E. Ismaeel

Example of inclusions Crystals: Crystalline inclusions have long been recognized as normal constituents of certain cell types such as Sertoli cells and Leydig cells of the human testis, and occasionally in macrophages Pigments: The most common besides hemoglobin of red manufactured by melanocytes of the skin and hair, pigments cells of the retina and specialized nerve cells in the substantia nigra of the brain. These pigments have protective functions in skin and aid in the sense of sight in the retina but their functions in neurons is not understood completely. Furthermore, cardiac tissue and central nervous system neurons shows yellow to brown pigment called lipofuscin, some believed that they have lysosomal activity. pigment blood in the melanin, body, cells is 01/03/1439 8 Farah E. Ismaeel

Pigments Endogenous pigments they formed by the cells Exogenous come from outside. like tattoo marks, carotene the epithelial surface of lung alveoli where it ingests inhaled particulate matter known as dustcells. and dust 01/03/1439 9 Farah E. Ismaeel

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Organelles All cells have the same basic set of intracellular organelles, which can be classified into two groups: (1) Membranous organelles with plasma membranes that separate the internal environment of the organelle from the cytoplasm. (2) Non membranous organelles without plasma membranes. 01/03/1439 11 Farah E. Ismaeel

The membranes of membranous organelles have different form: 1. Vesicular as in smooth-surfaced endoplasmic reticulum 2. plicated as in the inner mitochondrial membrane. 01/03/1439 12 Farah E. Ismaeel

each type of organelle contains a set of unique proteins. 1. In membranous organelles, these proteins are either incorporated into their membranes or sequestered within their lumens. For example, the enzymes of lysosomes are separated by a specific enzyme resistant membrane from the cytoplasmic because their hydrolytic activity would be detrimental to the cell. 2. In Non membranous organelles, unique proteins usually self assemble into polymers that form the structural elements of thecytoskeleton. matrix the 01/03/1439 13 Farah E. Ismaeel

Membrane bounded organelles Endoplasmic reticulum (ER) The largest organelle of most eukaryotic cells is ER. ER is a network of intercommunicating channels and sacs formed by a continuous membrane which encloses a space called cisternae this network (reticulum) extends from the surface of the nucleus to the cell membrane. 01/03/1439 14 Farah E. Ismaeel

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Endoplasmic reticulum (ER) The main function of ER is the transport of materials by forms transport vesicles in which large molecules are transported to other parts of the cell. Often, these vesicles are on their way to the plasma membrane or the Golgi apparatus. There are two types of ER according to the present of ribosome, Smooth ER Rough ER and 01/03/1439 17 Farah E. Ismaeel

Rough ER (RER) RER is studded with ribosomes on the side of the membrane that faces the cytoplasm. Here, proteins are synthesized and enter the ER interior, where processing and modification begin. Some of these proteins membrane, and someare forexport. Is found in all cells except erythrocytes and is especially abundant in pancreas (pancreatic acinar cell that produce digestive enzymes), fibroblasts produce collagen and plasma immunoglubins. are incorporated into cells that produce 01/03/1439 18 Farah E. Ismaeel

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Function of RER Has role in the synthesis of protein to be exported outside the cell. Modification of newly formed polypeptides. Assembly of multichain protein. Initial glycosylationof the glycoprotein which means addition of glucose to the protein. 01/03/1439 21 Farah E. Ismaeel

RER has a highly regulated system to prevent nonfunctional proteins being forwarded to the pathway for secretion or to other organelles. New proteins that cannot be folded or assembled properly by chaperones undergo ER-associated degradation (ERAD), in which unsalvageable proteins are translocated back into the cytosol, conjugated to ubiquitin, and then degraded by proteasomes. 01/03/1439 22 Farah E. Ismaeel

Quality control during protein production in the RER and properly functioning ERAD to dispose of defective proteins are extremely important and several inherited diseases result from malfunctions in this system. For example, in some forms of osteogenesis imperfect bone cells synthesize and secrete defective procollagen molecules which cannot assemble properly and produce very weak bone tissue. 01/03/1439 23 Farah E. Ismaeel

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