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Professor asastent of department histology, cytology and
embryology - KHODOROVSKA ALLA
Histology is the study of the tissues of the body and of how these
tissues are arranged to constitute organs. Each of the ...
The cell is the basic structural and functional unit of all
multicellular organisms, limited to an active cell
membrane, c...
Сytoplasm
Сytoplasm
The cytoplasm is a complex
colloidal system. The cytoplasm of a
cell consists of:
organelles
inclusi...
Сell membrane
Сell membrane
The cell membrane (plasmalemma) is an universal system which
form many structures of a cell. E...
Сell membrane
Сell membrane
The structure of each membrane includes:
Proteins make
50-60% of its weight,
lipids 30-40 % an...
Сell membrane
Сell membrane
Integral membrane proteins are tightly lodged in the lipid bilayer;
detergents are required to...
Сell membrane
Сell membrane
The inner and the outer dense line composed of a single layer of
phospholipids, between them s...
The plasmalemma carry out some of the important functions:
The plasmalemma carry out some of the important functions:

•Ba...
•Transport-through a membrane of cell freely passes water, salts and
substances with low molecular weight. Such transport ...
Facilitated diffusion
Facilitated diffusion

Certain molecules (e.g.,
glucose) cannot freely
diffuse across membranes
but ...
Some nondiffusible molecules can move into or out
of cell either along or against a concentration gradient.
Such movement ...
Endocytosis сells engulf extracellular substances and bring
them into the cytoplasm in membrane-limited vesicles by
mechan...
•In phagocytosis (“cell eating”), the cell engulfs insoluble
extracellular substances, such as large macromolecules or
ent...
Pinocytotic vesicles are usually smaller than phagosomes
Intercellular connections
Simple contact – membranes of two cells are on distance of 10-12
nm in such manner that glycocal...
Intercellular connections
Intercellular connections
Zonular adherentes

are band-like
adhesion. This device surrounds the cell and
joins it to its n...
Gap junctions,

Intercellular connections

also called communicating junctions, are regions of
intercellular communication...
Intercellular connections
Plasma membrane enfoldings of the

basal plasma
membrane increase the surface area available for...
Cytoplasm structures can be divided into 3 groups:
•Organelles
are
membrane-bound,
enzymecontaining, permanent subcellular...
Organelles constantly present in a cell are described as
membranous and nonmembranous.
The membranous organelles include:
...
The largest of the cytoplasmic organelles, mitochondria are the
energy providers of the cell. The size to bacteria (usuall...
The mitochondrial membranes create 2 membrane-limited spaces. The
intermembrane space is located between the inner and out...
Function the provide of cell with the energy for chemical and
mechanical work by storing energy generated from cellular
me...
The ribosomes are protein-synthesizing organelles. Each type of
ribosome has 2 unequal ribosomal subunits. Cytoplasmic rib...
They are intensely basophilic. Light microscopy reveals cytoplasmic
accumulations of ribosomes as basophilic patches, form...
Cytoplasmic ribosomes occur in 2 forms.
Free ribosomes are individual ribosomes dispersed in cytoplasm.
Polysomes are gr...
Endoplasmic Reticulum
The endoplasmic reticulum (ER) is a complex organelle involved in the
synthesis, packaging, and proc...
Rough endoplasmic reticulum (rER)
The also called granular endoplasmic reticulum, is studded with
ribosomes, many of them ...
Rough endoplasmic reticulum (RER)
rER is mainly concerned with the synhtesis of proteins for
sequestration from the rest o...
Smooth endoplasmic reticulum (SER)
The smooth endoplasmic reticulum (SER) lacks ribosomes
and thus appears smooth in elect...
Smooth endoplasmic reticulum (SER)
The sER is suspended in the
cytoplasm of many cells and
is especially abundant in cells...
The Golgi complex (Golgi apparatus) participates in many activities,
particularly those associated with secretion. It has ...
The cis face (convex face,
forming face) of the stack is
usually closest to adjacent
dilated ER cisternae and is
surround...
Lysosomes are spheric, membrane-limited vesicles that
may contain more than 50 enzymes each and function as
the cellular d...
Primary lysosomes are small (5-8 nm), with electron-dense
contents; they appear as black circles in electron micrographs. ...
Primary lysosomes
Secondary lysosomes are larger and less electron-dense and have a
mottled appearance in electron micrographs. They are for...
Residual bodies
are
membranelimited inclusion of
varying size and
electron
density
associated with the
terminal phases of
...
Primary lysosomes
Peroxisomes are membrane-limited, enzyme-containing vesicles
somewhat larger than primary lysosomes. Peroxisomes function ...
Microtubules are the thickest components of the cytoskeleton, with
diameters of 24 nm. They are fine tubular structures of...
Microfilaments are the thinnest cytoskeletal components (5-7 nm
wide). They are usually composed of one of several types o...
A centriole is a cylindric group of microtubules, 150 nm in overall
diameter and 350-500 nm long, containing 9 microtubule...
Centrioles are the structural organizers of the cell. Centriole
duplication is a prerequisite for cell division, and durin...
Prominent among inclusions serving as storage depots are spheric
lipid droplets, which differ in appearance depending upon...
NUCLEUS
Nuclei vary in appearance from tissue to tissue and cell to cell, but
they generally have a:

nuclear envelope
n...
NUCLEUS
The nuclear contents are set apart from the cytoplasm by a double
membrane called the nuclear envelope and a narro...
NUCLEUS
The envelope is perforated by many nuclear pores,
each of which has a diameter of about 70 nm and is
bounded by:

...
PORES
The pores provide a channel
for
the
movement
of
important molecules between
the nucleus and cytoplasm.
These
molecul...
Струкщ

Струкщ
Nucleoplasm
The nucleoplasm is the matrix in which the other
intranuclear components are embedded. It is composed of
enzym...
Nuclear chromatin
Nuclear chromatin is an intensely basophilic substance
consisting of DNA and associated histone and nonh...
Nuclear chromatin
Chromatin is a complex of DNA and proteins. It
is responsible for the characteristic basophilia of
the n...
Chromosomes
The chromosomes, the most highly condensed form of
chromatin, are visible during mitosis. In females, only one...
Nucleolus
During interphase (between mitoses), each nucleus
usually has at least one (or2) intensely basophilic body
calle...
Nucleolus
The term nucleolonema is used by light microscopists to refer to a
threadlike basophilic substructure of the nuc...
Nucleolus
pars fibrosa
pars granulosa
Thank you for attention !
Basic cytology
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Basic cytology

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Introduction in Histology. History of the science development. Basic cytology

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Transcript of "Basic cytology"

  1. 1. Professor asastent of department histology, cytology and embryology - KHODOROVSKA ALLA
  2. 2. Histology is the study of the tissues of the body and of how these tissues are arranged to constitute organs. Each of the fundamental tissues is formed by several types of cells and typically by specific associations of cells and extracellular matrix. Histology is classed as a subdiscipline of anatomy, because its methods involve dividing tissues and organs into pieces and preparing them for microscopic examination and chemical analyses. Two aspects of the subject are distinguished; special histology deals with the arrangement and special adaptations of tissues in the various organs whereas general histology deals with the components of the individual tissues. Cytology is the science about a cell.
  3. 3. The cell is the basic structural and functional unit of all multicellular organisms, limited to an active cell membrane, cytoplasm and nucleus. There are 2 basic cell types: Prokaryotic cells are typically small, single-celled organisms (bacteria) that lack a nuclear envelope, histones, and membranous organelles. Eukaryotic exist primarily components multicellular organisms. cells as of
  4. 4. Сytoplasm Сytoplasm The cytoplasm is a complex colloidal system. The cytoplasm of a cell consists of: organelles inclusions hyaloplasm The structure of hyaloplasm includes water, proteins, nucleinic acids, different polysaccharides and a lot of enzymes. The colloid system of hyaloplasm can be in a liquid or gel consistence. cytoplasm
  5. 5. Сell membrane Сell membrane The cell membrane (plasmalemma) is an universal system which form many structures of a cell. Each cell is bounded by a cell. The plasmalemma includes 3 layer: I. Glycocalyx (carbohydrates) II. Lipid bilayer (lipid molecule and proteins) III. Submembrane cortical layer (actin microfilaments and microtubules)
  6. 6. Сell membrane Сell membrane The structure of each membrane includes: Proteins make 50-60% of its weight, lipids 30-40 % and carbohydrates 5-10%. Most membrane proteins of the following 3 groups: proteins lipids carbohydrates carbohydrates Proteins іntegral transmembrane рeripheral lipids
  7. 7. Сell membrane Сell membrane Integral membrane proteins are tightly lodged in the lipid bilayer; detergents are required to extract them. They are folded, with their hydrophilic amino acids in contact with the phosphate groups of the membrane phospholipids and their hydrophobic amino acids in contact with the fatty-acid tails. Тransmembrane proteins from onlyone membrane surface, while others, penetrate the entire membrane and protrude from both sides. Peripheral membrane proteins are more loosely associated with the inner or outer membrane surface.
  8. 8. Сell membrane Сell membrane The inner and the outer dense line composed of a single layer of phospholipids, between them settle some proteins. Carbohydrates occur on plasma membranes mainly as oligosaccharide moieties of membrane glycoproteins and glycolipids. Membrane oligosaccharides have a characteristic branching structure and project from the cell's outer surface, forming a superficial coat called the glycocalyx that participates in cell adhesion and recognition. Structures of plasmalemma
  9. 9. The plasmalemma carry out some of the important functions: The plasmalemma carry out some of the important functions: •Barrier the plasmalemma separates a cell from an environment and other cells; the nucleus is separated from cytoplasm, membranes organelles from hyaloplasm. •Receptor on a surface of plasmalemma. There are special structures-receptors due to which the cell finds out different chemical substances, physical factors, other cells, hormones and antigens. special structures-receptors
  10. 10. •Transport-through a membrane of cell freely passes water, salts and substances with low molecular weight. Such transport is called passive. •The transport against a gradient of concentration is called active. Passive diffusion Passive diffusion Certain substances (e.g., water) can cross the membrane in either direction, following a concentration gradient. Passive diffusion does not require energy expenditure.
  11. 11. Facilitated diffusion Facilitated diffusion Certain molecules (e.g., glucose) cannot freely diffuse across membranes but must be helped across by a membrane component. This facilitated diffusion is often unidirectional, but it follows a concentration gradient and requires no energy.
  12. 12. Some nondiffusible molecules can move into or out of cell either along or against a concentration gradient. Such movement requires energy, usually as ATP. An example of this active transport is the sodium pump (Na+/K+-ATPase), which can expel sodium ions from a cell even when the external sodium concentration is higher than the internal one. Active Active transport transport
  13. 13. Endocytosis сells engulf extracellular substances and bring them into the cytoplasm in membrane-limited vesicles by mechanisms described collectively a endocytosis. Exocytosis removes substances from the cell. Cells use this process both for secretion and for excretion of undigested material. A membrane-limited vesicle or secretory granule fuses with the plasma membrane and releases its contents into the extracellular space, without disrupting the plasma membrane. Endocytosis Exocytosis
  14. 14. •In phagocytosis (“cell eating”), the cell engulfs insoluble extracellular substances, such as large macromolecules or entire bacteria. The vesicles formed are termed phagosomes. •In pinocytosis (“cell drinking”), the cell engulfs small amounts of intercellular fluid, which may contain a variety of solutes. Pinocytotic vesicles are usually smaller than phagosomes. Pinocytosis a f Phagocytosis f
  15. 15. Pinocytotic vesicles are usually smaller than phagosomes
  16. 16. Intercellular connections Simple contact – membranes of two cells are on distance of 10-12 nm in such manner that glycocalyx one cell adjoins with glycocalyx of another cell. The basic function is metabolism and information interchange between cells. Zonulae occludentes — also called tight junctions. Zonula occludens are located between adjacent plasma membranes most typically near the apices of epithelial cells. They form a "beltlike" junction that encircles the entire circumference of the cell. These junctions act as barriers that prevent the movement of molecules into the intercellular spaces.
  17. 17. Intercellular connections
  18. 18. Intercellular connections Zonular adherentes are band-like adhesion. This device surrounds the cell and joins it to its neighbors. Desmosomes (Maculae adherens). This is the most common type of tight junction between adjoining cells. A desmosome is a small circumscribed area of attachment – attachment plaques. At the side of a desmosome the plasma membrane (of each cell) is thickened because of the presence of dense layer of protein on inner surface. Desmosomes are serving to attach the basal cell membrane to the basal lamina.
  19. 19. Gap junctions, Intercellular connections also called communicating junctions, are regions of intercellular communication. They are widespread in epithelial tissues, in cardiac muscle smooth muscle cells and neurons. Gap junctions are built by six closely packed transmembrane proteins connexins that assemble to from structures called connexons. The two connexons fuse, forming the functional intercellular communication channel. The hydrophilic channel permits the passage of ions, small molecules and hormones.
  20. 20. Intercellular connections Plasma membrane enfoldings of the basal plasma membrane increase the surface area available for transport. The basal surface of some epithelia, especially those involved in ion transport, possesses multiple enfoldings of the basal plasma membrane. These enfoldings partition the basal cytoplasm and many mitochondria into the finger-like enfoldings. Synapse - type of contact between two nervous cells or between a nervous cell and a muscle. Through synapses pass nervous impulses.
  21. 21. Cytoplasm structures can be divided into 3 groups: •Organelles are membrane-bound, enzymecontaining, permanent subcellular compatrments. •Cytoplasmic inclusions are structures, membranebound or not, that are generally more transient than organelles and less actively involved in cell metabolism. •Cytoplasmic matrix the cytoskeleton is composed of proteinaceous elements that form a supporting network within the cytoplasm; some of these elements (microtubules) also form discrete cytoplasmic structures such as centrioles.
  22. 22. Organelles constantly present in a cell are described as membranous and nonmembranous. The membranous organelles include: endoplasmic reticulum (rER and sER) mitochondria Golgi apparatus lysosomes peroxisomes The nonmembranous organelles include: microtubules filaments (different varieties) centrioles ribosomes Membranous organelles are the most part of organelles of a cell.
  23. 23. The largest of the cytoplasmic organelles, mitochondria are the energy providers of the cell. The size to bacteria (usually 2-6 mm in lenght and 0.2 mm in diameter but quite variable) and have varios shapes: spheric, ovoid, filamentous. Each mitochondrion is bounded by 2 unit membranes. The outer mitochondrial membrane has a smooth contour and forms a continuous but relatively porous covering. It is freely permeable to various small molecules. The inner mitochondrial membrane is less porous and is therefore semipermeable. It has numerous infoldings, or cristae, that project into the mitochondrion’s interior. The mitochondrial cristae of most cells are shelflike, but those in steroid-secreting cells are typically more tubular.
  24. 24. The mitochondrial membranes create 2 membrane-limited spaces. The intermembrane space is located between the inner and outer membranes and is continuous with the interacristal space that extends into the cristae. The intercristal space, or matrix space, is enclosed by the inner membrane and contains the mitochondrial matrix. The mitochondrial matrix contains water, solutes, and large matrix granules, believed to be concerned with mitochondrial calcium-ion concentrations. It also contains circular DNA and mitochondrial ribosomes similar to those of bacteria. The matrix contains numerous soluble enzymes involved in such specialized mitochondrial functions as (citric acid the Krebs cycle cycle, tricarboxylic acid cycle), b-oxidation of lipids, and mitochondrial DNA DNA synthesis.
  25. 25. Function the provide of cell with the energy for chemical and mechanical work by storing energy generated from cellular metabolites in the high-energy bonds of ATP. Mitochondria are found in nearly all eukaryotic cells, and in most they are dispersed throughout the cytoplasm. However, they accumulate in the highest concentrations in cell types and intracellular regions with the highest energy requirements. Cardiac muscle cells are notable for the abundance of their mitochondria. Epithelial cells lining the kidney tubules have abundant mitochodria interdigitated between basal plasma membrane infoldings where active transport of ions and water occurs. DNA
  26. 26. The ribosomes are protein-synthesizing organelles. Each type of ribosome has 2 unequal ribosomal subunits. Cytoplasmic ribosomes are composed of ribosomal RNA (rRNA) synthesized in the nucleos and associated proteins synthesized in the cytoplasm. ribosomes
  27. 27. They are intensely basophilic. Light microscopy reveals cytoplasmic accumulations of ribosomes as basophilic patches, formerly termed ergastoplasm in grandular cells and Nissl bodies in neurons. In electron micrographs, ribosomes appear as small, electron-dense cytoplasmic granules. Nissl bodies
  28. 28. Cytoplasmic ribosomes occur in 2 forms. Free ribosomes are individual ribosomes dispersed in cytoplasm. Polysomes are groups of ribosomes evenly distributed along a single strand of messenger RNA (mRNA), an arrangement that permits synthesis of multiple copies of a protein from the same message. Polysomal ribosomes read (translate) the mRNA code and thus play a critical role in assembling amino acids into specific proteins, are found free in the cytoplasm (free polysomes) and attached to membranes of the rER. Free polysomes are involved in the synthesis of structural proteins and enzymes for intracellular use. Polysomes of the rER are involved in synthesizing proteins that are secreted or isolated.
  29. 29. Endoplasmic Reticulum The endoplasmic reticulum (ER) is a complex organelle involved in the synthesis, packaging, and processing of various cell substances. It is a freely anastomosing network (reticulum) of membranes that form vesicles, or cisternae; these may be elongated, flattened, rounded, or tubular. Transfer vesicles (transitional vesicles) are small, membranelimited vesicles that bud from the ER and cross the intervening cytoplasm to reach the Golgi complex for further processing or packaging of their contents. ER occurs in 2 forms: rough smooth
  30. 30. Rough endoplasmic reticulum (rER) The also called granular endoplasmic reticulum, is studded with ribosomes, many of them in polysomal clusters. rER cisternae are typically parallel, flattened, and elongated, especially in cells specialized for protein secretion (pancreatic acinar cells, plasma cells). The ribosomes give rER basophilic staining properties. The fine structure of rER (membranes and individual ribosomes) is visible only with the electron microscope.
  31. 31. Rough endoplasmic reticulum (RER) rER is mainly concerned with the synhtesis of proteins for sequestration from the rest of the cytoplasm, ie, secretory proteins such as collagen, proteins for incorporation into cell membranes, and lysosomal enzymes (separated from the rest of the cytoplasm to prevent autolysis). RER in protein-secreting epithelial cells often lies in the basal cytoplasm, between the plasma membrane and the nucleus.
  32. 32. Smooth endoplasmic reticulum (SER) The smooth endoplasmic reticulum (SER) lacks ribosomes and thus appears smooth in electron micrographs. SER cisternae are more tubular or vesicular than those of RER. SER stains poorly, if at all, so with the light microscope it is indistinguishable from the rest of the cytoplasm. Because it lacks ribosomes, the SER cannot synthesize proteins. It has many enzymes, important in lipid metabolism, steroid hormone synthesis, glycogen synthesis (glucose-6phosphatase), and detoxification.
  33. 33. Smooth endoplasmic reticulum (SER) The sER is suspended in the cytoplasm of many cells and is especially abundant in cells that synthesize steroid hormones (cells of the adrenal cortex, gonads in liver cells “hepatocytes”, where it is involved in glycogen synthesis and drug detoxification). Specialized SER termed sarcoplasmic reticulum is found in striated muscle cells, where it helps to regulate muscle contraction by sequestering and releasing calcium ions.
  34. 34. The Golgi complex (Golgi apparatus) participates in many activities, particularly those associated with secretion. It has an essential role in coordinating membrane flow and vesicle traffic among organelles. flattened cisternae; The composed of 3 major compartments: conspicious stack of 3-10 discrete, slightly curved, flattened cisternae; numerous small vesicles peripheral to the stack; a few large vacuoles, sometimes called condensing vacuoles, at the concave surface of the stack. flattened cisternae;
  35. 35. The cis face (convex face, forming face) of the stack is usually closest to adjacent dilated ER cisternae and is surrounded by transfer vesicles. Its cisternae stain more darkly with osmium. The trans face (concave face, maturing face) often harbors several condensing vacuoles and generally faces away from the nucleus. flattened cisternae; flattened cisternae;
  36. 36. Lysosomes are spheric, membrane-limited vesicles that may contain more than 50 enzymes each and function as the cellular digestive system. Their characteristic enzyme activities distinguish them from other cellular granules. The enzyme most widely exploited for their identification is acid phosphate, because it occurs almost exclusively in lysosomes. Other enzymes common in lysosomes are ribonucleases, deoxyribonucleases, cathepsins, sulfatases, b-glucoronidase, and phospholipases and other proteases, glucosidases, and lipases. Lysosomal enzymes usually occur as glycoproteins and are most active at an acidic pH. Lysosomes occur in various sizes and electron densities, depending on their level of activity.
  37. 37. Primary lysosomes are small (5-8 nm), with electron-dense contents; they appear as black circles in electron micrographs. They are the storage form of lysosomes, and their enzymes are mostly inactive. Lysosomes enzymes synthesized and coreglycosylated in the RER are transferred to the Golgi complex for further glycosylation; it is uncertain whether their final packaging as primary lysosomes occurs in the Golgi complex. The primary lysosomes disperse through the cytoplasm. They are found in most cells but are most abundant in phagocytic cells (macrophages, neutrophils). lysosomes
  38. 38. Primary lysosomes
  39. 39. Secondary lysosomes are larger and less electron-dense and have a mottled appearance in electron micrographs. They are formed by the fusion of one or more primary lysosomes with a phagosome. Their primary function is the digestion of products of heterophagy and autophagy; when the lysosomal enzymes mix with the phagosome contents, they become active. Lysosomal enzymes also catabolize certain products of cell synthesis, thus regulating the quality and quantity of secretory material. Secondary lysosomes occur throughout the cytoplasm in many cells, in numbers that reflect the cell’s lysosomal and phagocytic activity.
  40. 40. Residual bodies are membranelimited inclusion of varying size and electron density associated with the terminal phases of lysosome function. They contain undigestible materials such as pigments, crystals, and certain lipids.
  41. 41. Primary lysosomes
  42. 42. Peroxisomes are membrane-limited, enzyme-containing vesicles somewhat larger than primary lysosomes. Peroxisomes function in hydrogen peroxide metabolism. They contain urate oxidase, hydroxyacid oxidase, and d-amino acid oxidase, which produce hydrogen peroxide capable of killing bacteria; they also contain catalase, which oxidizes various substrates and uses the hydrogen removed in the process to convert the toxic hydrogen peroxide to water. Peroxisomes also participate in gluconeogenesis by assisting in the boxidation of fatty acids. They are found dispersed in the cytoplasm or in association with the SER. with
  43. 43. Microtubules are the thickest components of the cytoskeleton, with diameters of 24 nm. They are fine tubular structures of variable lenght, with dense walls (5 nm thick) and a clear internal space (14 nm in internal diameter). The walls are composed of subunits called tubulin heterodimers, each of which consists of one a-tubulin and one b-tubulin protein molecule. The tubulin heterodimers are arranged in protofilaments. Thirteen of these threadlike b-tubulin polymers of a- and b-tubulin align parallel to one another to form the wall of each microtubule. Microtubules increase in length by adding new heterodimers to one end, called the nucleation site. a-tubulin protofilaments
  44. 44. Microfilaments are the thinnest cytoskeletal components (5-7 nm wide). They are usually composed of one of several types of actin protein. In striated muscle cells, actin filaments form a stable paracrystalline array in association with filaments of myosin. Actin filaments in other cells are less stable and can dissociate and reassemble. These changes are regulated in part by calcium ions and cyclic AMP and by actin-binding proteins in the cytoplasm. Microfilaments are contractile, but to contract, they usually interact with myosin. In muscle cells, myosin forms thick filaments. In nonmuscle cells, it exists in soluble form.In nonmuscle cells, microfilaments are generally distributed as an irregular meshwork throughout the cytoplasm. tropomyosin myosin actin
  45. 45. A centriole is a cylindric group of microtubules, 150 nm in overall diameter and 350-500 nm long, containing 9 microtubule triplets in a pinwheel array. Each microtubule in a triplet shares a portion of the wall of the neighboring microtubule. An interphase (nondividing) cell has a pair of adjacent centrioles with perpendicular long axes, each surrounded by several electron-dense satellites, or pericentriolar bodies. Other cytoplasmic microtubules originate from the pericenriolar bodies and radiate into the cytoplasm.
  46. 46. Centrioles are the structural organizers of the cell. Centriole duplication is a prerequisite for cell division, and during mitosis the centrioles organize the microtubules of the mitotic spindle. Location. Between cell divisions, centrioles are near the nucleus, often surrounded by Golgi complexes. The centrioles and associated Golgi complexes constitute the cell cytocenter, which appears as a clear zone near the nucleus. During the S phase of interphase, each centriole duplicates by giving rise to a procentriole that grows at right angels to the original. During mitosis, the new centriole pairs migrate to opposite cell poles to organize the spindle.
  47. 47. Prominent among inclusions serving as storage depots are spheric lipid droplets, which differ in appearance depending upon the type of histologic preparation. Glycogen granules are inclusions that are PAS-positive in light microscopy and appear in electron micrographs as rosettes of electron-dense particles. Both lipid droplets and glycogen granules lack a limiting membrane. Melanin is a brownish pigment widely distributed in vertebrates, often found in electron-dense, membrane-limited granules termed melanosomes. It is particularly abundant in epidermal cells and in the pigment layer of the retina.
  48. 48. NUCLEUS Nuclei vary in appearance from tissue to tissue and cell to cell, but they generally have a: nuclear envelope nucleoplasm chromatin one to several nucleoli generally
  49. 49. NUCLEUS The nuclear contents are set apart from the cytoplasm by a double membrane called the nuclear envelope and a narrow (40-70 nm) intermembrane space called the perinuclear space. The nuclear envelope is often considered an exctension of the RER, because its outer surface is often peppered with ribosomes and shows occasional continuities with the RER. The inside of the inner membrane is lined with the fibrous lamina, a layer consisting of proteins called nuclear laminа. generally inside
  50. 50. NUCLEUS The envelope is perforated by many nuclear pores, each of which has a diameter of about 70 nm and is bounded by: 8 globular subunits called annular proteins, which present an octagonal appearance in some preparations. Each pore is covered by a proteinaceous diaphragm that is thinner than the envelope. globular subunits generally
  51. 51. PORES The pores provide a channel for the movement of important molecules between the nucleus and cytoplasm. These molecules include nucleic acids synthesized in the nucleus and used in the cytoplasm (mRNA, rRNA, tRNA) and proteins synthesized in the cytoplasm and used in the nucleus (histones, polymerases). nucleus generally
  52. 52. Струкщ Струкщ
  53. 53. Nucleoplasm The nucleoplasm is the matrix in which the other intranuclear components are embedded. It is composed of enzymatic and nonenzymatic proteins, metabolites, ions, and water. heterochromatin It includes the nuclear matrix – a fibrillar “nucleoskeletal” structure that appears to bind certain hormone receptors-and newly synthesized DNA.
  54. 54. Nuclear chromatin Nuclear chromatin is an intensely basophilic substance consisting of DNA and associated histone and nonhistone proteins. Nuclei containing highly coiled chromatin, termed heterochromatin, stain darkly with basic dyes. heterochromatin coiled
  55. 55. Nuclear chromatin Chromatin is a complex of DNA and proteins. It is responsible for the characteristic basophilia of the nucleus. The densely staining material is highly condensed chromatin called heterochromatin and the lightly staining material is a dispersed form called euchromatin.
  56. 56. Chromosomes The chromosomes, the most highly condensed form of chromatin, are visible during mitosis. In females, only one X chromosome (either of the 2) is used by each cell; The inactive X chromosome is often visible as a clump of heterochromatin termed sex chromatin, or the Barr body. In most cells, the Barr body is attached to the inner surface of the nuclear envelope. In a neutrophilic leukocyte, it may appear as a drumstick-shaped appendage of the lobulated nucleus.
  57. 57. Nucleolus During interphase (between mitoses), each nucleus usually has at least one (or2) intensely basophilic body called a nucleolus. Nucleoli are the synthesis sites for most ribosomal RNA (rRNA). The nucleolus disappears in preparation for mitosis and reappears after mitosis is completed.
  58. 58. Nucleolus The term nucleolonema is used by light microscopists to refer to a threadlike basophilic substructure of the nucleolus. The nucleolonema contains 2 rRNA-rich components distinguishable by electron microscopy. The pars fibrosa consists of densely packed ribonucleoprotein fibers, 510 nm in diameter. These fibers consist of the newly synthesized primary transcripts of the rRNA genes and associated proteins. The pars granulosa contains dense granules, 15-20 nm in diameter, that represent maturing ribosomal subunits during assembly for export to the cytoplasm. Nucleolus pars fibrosa pars granulosa
  59. 59. Nucleolus pars fibrosa pars granulosa
  60. 60. Thank you for attention !

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