Dr. Amal M. Moustafa,, Department of Histology & Cytology

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3 THE CELL The animal cell is the structural and functional unit in the body Interphase cell: this term is used to denote any cell that is not dividing, whether it is preparing for the next division or has lost its ability to divide The interphase cell consists of: 1- The Cytoplasm 2- The Nucleus surrounded by cell membrane

4 The Cytoplasm It is composed of: I - Cell organelles. II - Cell inclusions. III - cell matrix.

5 I-THE CELL ORGANELLES They are living components in the cytoplasm which are essential for the life of the cell and perform specific functions inside the cell. Types of cell organelles: 1-Membranous cell organelles: They are surrounded by a unit membrane e.g. mitochondria, Golgi apparatus, lysosomes, endoplasmic reticulum, peroxisomes and coated vesicles. They are important for the metabolic activity in the cell. 2-Non-membranous cell organelles: They are not surrounded by unit membrane e.g. microfilament microtubules, centeriole, cilia and flagella. They are important as a cyto-skeleton of the cell.

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7 Def. It is the outer limiting membrane which surrounds the cell and regulates the passage of materials into or out of the cell.

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9 Function of Cell Membrane 1-Passive diffusion, e.g. gases, O2, CO2 as well as essential ions. 2-Active transport, e.g. A.A., glucose and fatty acid. They need the presence of certain enzymes and energy. 3-Selective transport for hormones, drugs and bacteria. They need receptors and energy. 4- Endocytosis (Internalization of solid or liquid materials inside the cell): phagocytosis: solid particle pinocytosis. Transportation of fluids Receptor-mediated endocytosis:expels out any waste product 5. Exocytosis: 6. Sodium potassium pump: By this process Na+ is continuously pumped outside the cell and K+ enters the cell. 7-. The cell membrane may be modified in certain cells which perform different variable functions: a. Microvilli (absorptive epith). b. Cilia (in respiratory tract). c. Flagellae (in sperms). d. Formation of cell junctions. e. Formation of myelin sheath. Dr. Amal M. Moustafa,, Department of Histology & Cytology

10 Definition : They are membranous cell organelles be the as they provide the cell with ATP gives energy for the different vital activities. they contain the enzymes of Kreb's

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12 EM: Appear as double membranous vesicles. The outer membrane is smooth & permeable to small molecules and ions. The inner membrane reveals a number of folds which usually project like shelves in the matrix of the mitochondrion called (cristae). The number of the cristae is directly proportional to the activity of the cell. The matrix: The inner membrane encloses a space called intramembranous space. This space is filled with the matrix, which appears more electron dense than the outer surrounding cytoplasm. It contains electron dense granules called matrix granules that are rich in Ca++ or Mg++ cations. The matrix also contains the enzymes of citric acid cycle

13 Definition: They are non - membranous cell organelles They are..sites for protein synthesis in the cell Molecular structure: They are composed of ribosomal RNA (rrna) and proteins. Size: They are very small spherical bodies, nm in diameter EM: The individual ribosome appears as an electron dense granule composed of two subunits; small and large subunits. Types of ribosomes: Free ribosomes: they are scattered individually in the cytoplasm: Attached ribosomes: they are attached to the outer surface of the endoplasmic reticulum rer

14 Function of ribosomes Ribosomes synthesize proteins, as they translate the message, which is carried by mrna. Free ribosomes are concerned with synthesizing proteins for the use of the cell. (Cytoplasmic matrix, nuclear proteins and some mitochondrial proteins). Attached ribosomes are concerned with synthesizing proteins that are segregated inside rer to be either secreted outside the cell as secretory proteins or produces lysosomal proteins and integral proteins.

15 RETICULUM ENDOPLASMIC Definition: It is a membranous cell organelle formed of a reticulum of anastomosing and intercommunicating narrow tubules, cisternae and vesicles. Site: In the cytoplasm, it extends from the nuclear envelope to the cell membrane. Types: There are two specialized types:- 1-Rough endoplasmic reticulum or granular (rer): 2-Smooth endoplasmic reticulum or a granular (ser): ER

16 1-Rough endoplasmic reticulum or granular (rer): It is prominent in cells specialized for protein secretion, such as plasma cell and pancreatic acinar cells. With light microscope, it does not appear as a reticulum but it imparts on the cytoplasm its basophilia (due to the presence of polysomes on its surface). With EM, it appears as parallel flattened membranous cisternae, which are sometimes continuous with the outer membrane of the nuclear envelope. Its cytoplasmic surface is rough, due to attached polyribosomes.

17 Function of rer: It is concerned with segregation of the proteins which were synthesized by ribosomes: It provides protection of the cytoplasm from the hydrolytic destructive effect of the hydrolytic enzymes.

18 2. Smooth endoplasmic reticulum (ser): Definition: It is a type of ER. With EM: It appears as communicating narrow membranous tubules. Function of ser: Concerns with lipid synthesis, e.g. steroid hormones. It is the site for detoxification of certain hormones and toxic substances such as alcohol & phenobarbitone. Plays a role in glycogen synthesis. Plays a role in muscle contraction which pumps Ca ions for muscle contraction and withdraw them during muscle relaxation.

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23 Definition: They are membrane bounded cell organelles which contain a large variety of acid hydrolases for intra-cytoplasmic digestion. Site: They are present in the cytoplasm of all cells, but they are abundant in cells which have phagocytic activity like macrophages. With EM two types of lysosomes are seen: Primary lysosomes: They are spherical membrane bounded vesicles with a homogenous moderate electron dense granular core. Functionally they are not yet engaged in intra-cellular digestion. They contain a large number of acid hydrolases (among them, protease, ribonuclease, lipase, acid phosphatase, sulfates, ect..). Lysosomes cannot be identified with certainty without the detection of acid phosphatase activity or the activity of any one of the acid hydrolases present in them. Secondary lysosomes: They are spherical membrane bounded vesicles with heterogenous electron dense core. They are functionally engaged in intra-cellular digestion. They are larger than primary lysosomes. They develop by fusion between primary lysosomes and phagosomes. Secondary lysosomes Primary lysosomes

24 Definition: It is in all cells except mature erythrocytes (R. B. Cs.) and blood platelets. It is essential for the life of the cell. It controls all the metabolic activities in the cell and plays an important role in heredity and cell division. Structure of the Nucleus Nuclear membrane It contains 46-d chromosomes Nucleous. Nuclear sap

25 Centrioles Def. non memb. Cell org.import...cell divis. Associated with it pricentriolar bodies form..mtocs

26 EM :Two cylinder perpendicular on each other

27 Functions of centrioles

28 Def. hair like processes project from free surface of cells Site resp.system, uterus & F.T Number: several hundreds/cell Size : 10-15um 15um in lengh & 0.2um in diameter Cilia

29 EM/ cilia formed of: Shaft,basal body&rootlets

30 *Function of Cilia: Can beat rhythmically in one direction to move a thin film of mucous or fluid on the surface of cells. *****Stereocilia*** Non motile cilia present in Epidydmis

31 Flagella Cytoplasmic processes = tail of sperm. EM: Similar to T.S. in shaft of cilia. But:Each doublets has large outer fiber much longer (200nm) Whip like swimming movement. One Flagellum/sperm

32 Cytoplasmic filaments *Def. non memb,they are thread like str. Present in variable amount in diff. Cells. *Type 1-Thin F... 2-Thick F.. (actin) (myosin) Resp[osible for Muscle contraction 3-Intermediate F. Play a role in support,maintain shape of cells

33 Microtubules Def: pipe like stru.,uniform &variable length. Distribution: all over cytoplasm. polymerized at MTOCs at centrioles, EM: hollow tubules T.S..tiny circles

34 Site 1-basal Body of cilia 2-centromere of chromsomes.

35 Function Of Microtubules *Cytoskeleton of the cell. shape of the cells. *Main component cilia, flagella &centeriol *act as guiding traks for trasport material &organelles

36 Cell Inclusions They are non living materials in cytoplasm: Products of metabolism Or Substance are taken inside cells from its surrounding. They include: Stored food,pigments & Crystals

37 1-Stored food: A-Glycogen LM. Hx&E dissolve leaving irregular small empty spaces and the cytoplasm appears vacuolated. EM n There are 2 Type A & B

38 A granules(liver)

39 B granules(muscle)

40 B- Fat Large lipid globules or droplets

41 2-Pigments They are coloured substances in the cells without staning. A-Exogenous pigments: Lipochromes(Carotene) Yellow skin. Dust..inhaled by lung.black lung. Tattoo produced by needle pricks in skin Minerals..Lead grey line in gingiva: Silver..black pigm. in skin

42 B-Endogenous pigments These are pigments produced by the body: Hb in RBCs Red colour Hb derivatives Haemosiderin(golden brown).bilirubin (yellow brown).biliverdin (green ) Melanin..Brown or black(skin,hair,eye) Lipofuscin pigments (golden brown) : In cardiac muscle nerve cells & hepatocytes. They are residual bodies that are not hydrolized by lysosomal enzymes. They increase with age

43 3-Crystals Calcium Oxalates & Calcium carbonates. They are present in pathological condition

44 Cytoplasmic Matrix (Cytosol) It is gel like struc. Filling intercellular spaces( ) cytop. Organelles &Inclutins

45 EM : appears as fragile supporting framework (microtrbecular lattic) Functions: The lattice binds many e nzymes, prot.,nutrients &precursors of macromolec. Holds cell org.in their right position.

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