3. Components of the cytoskeleton: intermediate filaments microtubules microfilaments (actin filaments) Microtubules: diameter 25 nm are hollow tubes composed of 13 strands of protofilaments that are formed from proteinaceous tubulin subunits (alpha and beta-tubulin ) m icrotubules are bound to other cytoskeletal elements and cytoplasmic organelles

6. Chief distribution of microtubules: interphase cell in mitosis cilia + kinetosomes

7. Mi c rofilament s (actin filaments) have diameter only 5-7 nm are composed of actin, a protein involved in muscle contraction each microfilament is formed with hundreds of globular subunits - G-actin - organized into a double-stranded helix with a 36 nm repeat - F- actin microfilaments are very dynamic structures that are continually dissociated and reassembled

9. in muscle cells – rhabomyocytes and cardiomyocytes, microfilaments are associated with myosin filaments and form stable structures called as myofibrils

15. mitochondria are autonomic organelles – contain own DNA and ribosomes that differ from cytoplasmic ones and produce several own proteins new mitochondria originate from preexisting mitochondria by division

18. Function of G.a.: is engaged in segregation of newly formed or synthesized cellular constituents and their directing to their final destination in cell s the cis-fa c e is closest to the ER and represents the site at which the material enters the organelle ( forming face ) the trans-face is adjacent to secretion vesicles and storage granules and represents the exit site for most constituents ( maturing face )

20. Function: free ribosomes / polysomes / are site s of protein synthesis for the use of the cell bound ribosomes

21. Endoplasmic reticulum was discovered with introduction of electron microscope in to cytology t he organelle is identical with the cytoplasmic compartment that stains with basic dyes and is known as the ergastoplasm in the light microscope 2 forms: the rough ER , with ribosomes bound to the outer membrane surface (RER), and smooth ER that is ribosome-free (SER) Rough endoplasmic reticulum consists of anastomosing flattened sacs - cisternae with polysomes on external surface of limiting membrane

22. RER is abundant especially in glandular cells and corresponds to basophilic regions of the cytoplasm glucose-6-phosphatase is used as marker for this compartment Function of t he RER : is a major site of synthesis of proteins that are produced for the use of other cells

23. Smooth endoplasmic reticulum is made up convoluted tubules or small vesicles that intercommunicate each other contains no attached ribosomes is usually found more peripherally in the cell it corresponds with cytoplasmic areas that are neutrophilic or sligthly acidophilic t he relationship between both forms of ER is very flexible Golgiho aparát

24. Function: the site of lipid synthesis , the site of synthesis and break-down of glycogen, is angaged in formation of membran in the cell, converts toxic molecules to nontoxic derivatives that can be excreted in muscle cells – functions as pool of Ca ions

25. steroidogenic cells abundant SER mitochondria with tubules

27. Secondary lysosomes are larger than primary ones; the diameter of them ranges between 1 to 2 mm originate as a result of fusion of primary lysosomes with the structure s containing the substance to be digested subdivided on the basis of morphology in to: phagolysosomes – originate by fusion of primary lysosomes with phagocytic Vacuoles autophagic vacuoles – by fusion of primary lysosomes with cellular components such as e.g. mitochondria or RER structural picture of s. l. - variable

28. Residual bodies ( telolysosomes ) = are final form s of secondary lysosomes that are enzymic inactive c ontain material not digested by lysosomal enzymes Function: degradation not only of intracellular substances and damaged structures but also exogenous provenience

30. Peroxisomes (microbodies ) are spherical, membrane-limited organelle s, about 0,5 - 1.0  m in diameter in several cells ( in liver and kidney ) , they contain a dense crystalline core termed a nucleoid are usually found close to the ER contain more than 40 enzymes that are responsible for a variety of catabolic and anabolic r eactions very typical enzyme of this organelle is the catalase destroys hydrogen peroxide urate oxidase, oxidase of D- amino acids Function: take participation in synthetic as well as catabolic processes in cells (synthesis of bile acids, synthesis of phospholipids etc)

31. Centriol e paired organelle ovoid body ( cca 0,2 µm wide x 0,2-0,5 µm long) in all cells that divide mitotically (except blood and nerve cells) located nearly the nucleus and is surrounded by an area of cytoplasm different from the rest by lesser staining = the centrosome ultrastructural appearance 9 sets of microtubule triplets composed of 3 microtubules of 15 to 20 nm in diameter support ing the periphery pericentriolar structures (appendages)

34. Lipid droplets variable diameter 100 nm - 10 µm they serve as a local store of energy and also as a source of short carbon chains i n ordinary histological sections these are likely appear as round clear areas in the cytoplasm, because the lipid is extracted by solvents used in the preparation of the specimen , a fter osmium tetroxide fixation, lipid droplets transit into insoluble and extraction resistant form and appear as black spherical structures in the light microscope t he same appearance lipid droplets show also in electron m icrographs th e degree of blackening or electron density depends upon the degree of unsaturation of the lipid and the nature of the fixative used

35. Carbohydrates are most ly stored in the form of glycogen is not apparent in routine histological sections but may be selectively stained by the P eriodic A cid-Schiff ´s reaction (PAS) (brilliant magenta). i n electron micrographs, the glycogen shows granular appearance (in dependence of fixative used) i t occurs in 2 form s: as dense, roughly izodiametric, 15 to 30 nm particles, referred to as the beta – particles or as rosette-like aggregates of larger size called alpha particles

36.  - granul es / cca 20 nm  - granul es / cca 450 - 600 nm g ly c ogen in TEM

38. Lipofuscin a tan or light brown pigment that fluoresces a golden-brown in ultraviolet light an amount of lipofuscin is progressively increased with advancing age ("wear and tear" pigment) – neurons (cells of the autonomic ganglion) r ecently lipofuscin is thought to be end product of lysosomal activity and is regarded as the indigestible residues of phagocytosed material or degenerated organelles

39. THE CELL CYCLE cell cycle or generation time (individual history of the cell) = time from one mitosis to the beginning of the next , it occurs in all tissues with cell turnover; characterised by many events in both the cell nucleus and the cytoplasm cell cycle : interphase and mitosis Interphase is divided G 1 - postmitotic S- DNA synthesis G 2 - pre mitotic mitosis (pro-, meta-, ana, telophase) G 1 – 8 - 25 h , intense synthesis of RNA and proteins, number of organelles increases, the cell volume of daugter cell is restored to normal size S - 8 h , synthesis of DNA and its duplication, after S phase completion chromosomes composed of 2 identical chromatids, centriol is replicated G 2 - (post DNA duplication) - 3 h , cell continues in growth and cumulates energy, tubulin is synthesized, preparation to mitosis,

41. Mitosis cca 1 h (40-120 min)

42. Metaphase

43. Late anaphase constriction ring from microfilaments is organized in the equatorial plane of the parent cell further narrowing of the ring leads to separation of both daughter cells