1. Microscopic arid modern stages of development of histology. Formation of descriptive, comparative and evolution histology.
Домикроскопический период (с IV в. до н. э. по 1665 г.)
Микроскопический период (с 1665 г. по 1950 г.). Начало периода связывают с именем английского физика Роберта Гука, который, во-первых, усовершенствовал микроскоп, во-вторых, использовал его для систематического исследования различных объектов и опубликовал результаты этих наблюдений в 1665 г. в книге "Микрография", в-третьих, впервые ввел термин "клетка" ("целлюля"). В дальнейшем осуществлялось непрерывное усовершенствование микроскопов и все более широкое использование их для изучения биологических тканей и органов.
Ботаник М. Шлейден заинтересовался происхождением клеток цитогенезисом. Результаты этих исследований позволили Т. Швану, на основании их сообщений, сформулировать клеточную теорию (1838-1839 гг.) в виде трех постулатов:
- все растительные и животные организмы состоят из клеток;
- все клетки развиваются по общему принципу из цитобластемы;
- каждая клетка обладает самостоятельной жизнедеятельностью, а жизнедеятельность организма является суммой деятельности клеток.
Современный этап развития гистологии начинается с 1950 г. с момента начала использования электронного микроскопа для изучения биологических объектов, хотя электронный микроскоп был изобретен раньше (Е. Руска, М. Кноль, 1931 г.). Однако для современного этапа развития гистологии характерно внедрение не только электронного микроскопа, но и других методов:
цито- и гистохимии;
гисторадиографии;
других вышеперечисленных современных методов.
2. Types of histological preparations. Stages of making of histological preparation for light and electron microscopy. Demands making to histological preparation.
Types of histological preparations
Stages of propagating of histological preparation
1) Taking and fixing of material
- physical (by thermal processing fixatives)
- Chemical (by immersion into the formalin and so on)
2) Condensation of material
- impregnation by condensing mediums (paraffin, celloidin etc)
- freezing
3) Preparing of sections on microtome
4) Staining of histological sections by histological dyes
-Acidic (eosin, acid fucsin)
-Basic (azur, hematoxylin)
-Neutral
5) Conclusion of section into preserving medium (Canadian, fir balsam, synthetic medium)
Requirement to histological preparation:
1) To reflect vital structure
2) Be transparent
3) Be contrast
4) Be constant
3. Tissues as systems of cells and their derivatives. Concept on cell and non-cellular structures. The basic thesis of cellular theory on the modem stage of development of science.
Tissue represents system of cells and non-cellular structures realizing definite function.
Cell is living system limited by plasmatic membrane, consisting of nucleus and cytoplasm, able to self-supporting, self-regulation and reproduction
Cell is the basis of development, structure and vital activity of all animal and vegetative organisms.
Non-cellular structures:
• symplast,
• syncytium and
• intercellular substance.
Symplasts are large formations consisting of plasmalemma with numerous nuclei.
Example is striated muscle fibre.
Symplasts appear as a result of junction of cells or division of nuclei without division of cytoplasm of cell.
Syncytium is characterized by that after division of initial cell daughter cells stay connected with each other with the help of fine cytoplasmic bridges (e.g., mesenchyme; spermatogonia of testis keep connection with each other for a long time).
Intercellular substance is derivative of cells predominantly of mesenchyme origin: proper connective tissues, cartilage and bone.
Cellular theory was founded by Shwann and Shleiden in 1838.
The main thesis of cellular theory:
4. Cell membrane (plasmalemma). Chemical composition and functions of plasmalemma. Intercellular junctions.
Cell is bounded from surrounding and from neighbor cells by plasmalemma – external cell membrane. Plasmalemma provides immediate connection of cell with extracellular environment.
Its thickness is 10 nm, it is formed by lipid and protein components.
Functions of plasmalemma:
1. Limiting function – it separates cell content from surroundings;
2. Transport function – through plasmalemma transport of substances is realized;
3. Receptor function – perception of signals from external for cell medium; taking part in formation of intercellular contacts.
Intercellular junctions:
Plasmalemma of multicellular organisms patricipates in formation of intercellular junctionsproviding intercellular interactions.
Following junctions are present:
1) simple. It is simple intimacy of plasmalemma of neighbor cells for distance 15-20 nm
2) compact. Layers of 2plasmalemma are max close and it makes impression of their junction.
3) nexus. In such type of junction ionic canaliculi (protein channels) are present in plasmalemma.
4) desmosome. consists of 2 electron dense halves of glycoprotein origin belonging to plasmalemma of neighbor cells.
5) synapse. These are junctions between nerve cells. Excitation from one cell passes to another.
5. Structural-chemical and functional characteristic of membranous organelles.
- endoplasmic reticulum,
Aggregation of vacuoles, flat membrane saccules or tubular formations.
There are 2 types of ER:
1) granular (rough) ER - its surface is covered by ribosomes;
2) smooth ER – its surface does not contain ribosomes.
- Golgi complex, is accumulation of flattened cisterns.
Functions:
• synthesis of polysaccharides and their connection with proteins;
• accumulation and excretion of ready secretions outside of cell;
• formation of
lysosomes.
- mitochondria,
Consist of external and internal membrane.
Cavity of mitochondria is filled by matrix containing mitochondrial DNA and ribosomes.
Function is ATP synthesis.
- lysosomes, are corpuscles containing hydrolythical enzymes – hydrolase splitting biopolymers till monomers.
- plasmalemma,
- peroxisomes
These are oval corpuscles containing enzymes of oxidizing of aminoacids and catalase which destroy H2O2.
Catalase of peroxysomes plays protective role because of H2O2 is toxic for cell.
6. Structural-chemical and functional characteristic of non-membranous organelles.
- ribosome,
are corpuscles consisting of big and small subunits – complex of ribosomal RNA with proteins. There are:
1) free ribosomes – freely located in hyaloplasm and synthesizing proteins for cell itself;
2) connected with ER ribosomes – synthesizing exported proteins.
- centrioles,
It represents cylinder which wall consists of 9 complexes of microtubules.
Each complex consists of 3 microtubules and it is called triplet.
- microtubules, ( contain protein tubulin)
- microfilaments (contain contractile proteins: actin, myosin);
- intermediate filaments (in different tissues they contain different proteins: in cells of epithelium – keratin, in cells of mesenchyme tissues – vimentin, in muscle cells – desmin)
7. Special organelles. Inclusions. Determination, classifiotion Hyaloplasm. Its physical-chemical properties, significance in vital activity of cell.
There are organelles of general significance present in the all cells and special present in specialized types of cells (cilia, flagella, myofibrils).
• Special organelles are typical for those cells which realize specializing functions.
• These are cilia, flagella, microvilli, basal folds, tonofibrills, myofibrils, neurofibrills.
Microvilli are fine and long growth of apical part of cells.
It promotes movement of content of microvilli into cell
- during absorption of substances in the lumen of intestine or
- during re-absorption of substances from renal tubules.
Cilia and flagella are derivatives of microtubules in specialized cells (of epithelium of bronchi, epithelium of uterus, spermatozoa).
• Cilia and flagella represent growth of cell ate the basis of them basal corpuscle is present, it is formed by 9 triplets of short microtubules.
• Cilia and flagella make function of movement.
Inclusions of cytoplasm are not obligatory components of cell appeared and disappeared depending on metabolic condition of cells.
- trophic, are lipid (droplets of neutral fats), carbohydrates (glycogen), protein.
- secretory, contain biologically active substances (hormones, neuromediators, factors of growth and others).
- excretory, are products of cell metabolism which undergo to removing.
- pigment, can be exogenic (dust powder, dyes) and endogenic (hemoglobin, bilirubin, melanin).
8. Nucleus. Significance in vital activity (foil and in transfer of genetic information. The basic components of nucleus.
Nucleus is the system of genetic determination and regulation of protein synthesis. The nucleus constitutes the central more dense part of the cell. It is usually rounded or ellipsoid. Nucleus provides 2 groups of general functions: 1) keeping and transmission of genetic information, 2) realization of genetic information, protein synthesis. In nucleus reduplication of DNA molecules takes place.
The basic components of nucleus: nuclear membrane, nucleolus, chromatin, caryoplasm.
Nuclear membrane or cariolemma consists of outer nuclear membrane and inner nuclear membrane. The outer nuclear membrane is continuous with endoplasmic reticulum. The space between the inner and outer membranes is the perinuclear space or nucleolemma cistern. The inner layer of the nuclear membrane provides attachment to the ends of chromosomes. Deep to the inner membrane there is a layer containing proteins and a network of filaments: this layer is called the nuclear lamina. At several points the inner and outer layers of the nuclear membrane fuse leaving gaps called nuclear pores. Their diameter is 80-90 nm.
Carioplasm (nucleoplasm) is fluid internal content of nucleus in which chromatin and nucleolus are located.
Chromatin looks like small basophilic granules inside of nucleus. During observation of alive or fixed cells in nuclei we can see zones of dense substance. It is called chromatin, because of its affinity for dyes. Chromatin is a complex of DNA and protein.
Depending on degree of decondensation of chromosomes there are: 1) euchromatin, complete decondensation of chromatin 2) heterochromatin, incomplete decondensation of chromatin.
Chromosomes are made up of DNA and proteins. The number of chromosomes in each cell is fixed for a given species and in man it is 46.
Nucleolus. In the cells of the all eukaryotic organisms in nuclei one or more nucleoli are present. They are stained by different dyes, especially basic (alkaline). They are basophilic. Nucleoli consist of a central filamentous zone and outer granular zone. Nucleoli are sites where ribosomal RNA is synthesized.
9. Cellular cycle of slit. Determination. Characteristic of its stages: mitotic cycle, growth and differentiation, active funtioning, senility and death. Cell cycle of somatic cells. Characteristic of periods of interphase and phases of mitosis.
Multiplication of cells takes place by division of pre-existing cells. Such multiplication constitutes an essential feature of embryonic development. Cell division is equally necessary after birth of the individual for growth and for replacement of dead cells. Time of cell existing from division till division or from division till death of cell is called the cell cycle.
Many cells of the body have a limited span of functional activity at the end of which they undergo division into two daughter cells. Each cell is genetically identical to the parent cell. The daughter cells in turn have their own span of activity followed by another division. The period during which the cell is actively dividing is the phase of mitosis (M phase). The period between two successive divisions is called the interphase.
Mitosis is universal method of division of somatic cells. Somatic cell division occurs in two phases. Firstly, the chromosomes duplicated in S phase are distributed equally between the two potential daughter cells. This process is known as mitosis. Secondly, the dividing cell is cleaved into genetically identical daughter cells by cytoplasmic division or cytokinesis.
Mitosis is continuous process, which is traditionally divided into four phases, prophase, metaphase, anaphase and telophase.
Prophase. During the prophase the chromatin of the chromosome becomes gradually more and more coiled so that the chromosome become recognizable as a thread-like structure that gradually acquires a rod-like appearance. Towards the end of prophase the two chromatids constituting the chromosome become distinct. The two centrioles separate and move to opposite poles of the cell. They produce a number of microtubules that pass from one centriole to the other and form a spindle. At the same time in the middle of prophase the nuclear membrane breaks down and the nucleoli disappear.
Metaphase. The nuclear envelope having disintegrated, the mitotic spindle moves into the nuclear area and each duplicated chromosome becomes attached, at a site called the kinetochore, to another group of microtubules of the mitotic spindle (kinetochore or chromosome microtubules). The kinetochore is a DNA and protein structure on each duplicated chromosome. The chromosomes become arranged in the plane of the spindle equator, known as the equatorial of metaphase plate. Metaphase occupies 1/3 of time of all mitosis.
Anaphase. This stage of mitosis is marked by the splitting of the centromere, which binds the chromatids of each duplicated chromosome. The mitotic spindle becomes lengthened by addition of tubulin subunits to its interpolar microtubules. The centrioles are thus pulled apart and the chromatids of each duplicated chromosome are drawn by the kinetochore microtubules to opposite ends of the spindle. Thus achieving an exact division of the duplicated genetic material. To the end of anaphase two groups of identical chromosomes (the former chromatids) are clustered at opposite poles of the cell. Anaphase is the shortest stage of mitosis.
Telophase. During the final stage of mitosis, the chromosomes begin to uncoil and to regain their interphase conformation. The nuclear envelope reassembles and nucleoli again become apparent. The process of cytokinesis also takes place during telophase. The plane of cytoplasmic division is usually defined by the position of the spindle equator, thus producing of two cells of equal size. The plasma membrane around the spindle equator becomes indented to form a circumferential furrow around the cell, the cleavage furrow. It progressively constricts the cell until it is cleaved into two daughter cells.
Duration of mitosis depends on line of factors especially from surrounding temperature. Damages of chromosomes and of mitotic apparatus under the action of unfavorable factors are accompanied with formation of atypical mitosis.
Amitosis and endoreproduction
Amitosis or atypical mitosisis indirect cell division.Although mitosis is always equal and symmetrical, cytokinesis may, in some situations, result in the formation of two daughter cells with grossly unequal amounts of cytoplasm or cytoplasmic organelles. Nucleus is in condition of interphase. Chromosomes are not condensed and formation of spindle does not occur. In other circumstances, amitosis leads to appearance of binucleate and multinucleate cells.
Endoreproduction is special type of cell reproduction. It is accompanied with double increasing of number of DNA in cell without consequent cytotomia and appearance of polyploid cells with increased number of chromosome content. This occurs as a result of total absence or incomplete separate stages of mitosis. Polyploid cells are formed in liver, in epithelium of urinary bladder, pigmented epithelium of retina, in acinar sections of salivary gland and pancreas, megacaryocytes of red bone marrow.
Meiosis
Meiosis is method of division of sexual cells containing haploid number of chromosomes. A different kind of cell division occurs during the formation of gametes. This consists of two successive divisions called the first and second meiotic divisions. The cells resulting from these divisions differ from other cell in the body in that:
a) the number of chromosomes is reduced to half the normal number,
b) the genetic information in the various gametes produced is not identical.
Meiosis consists of two successive divisions called the first and the second meiotic division. During the interphase preceding the first division duplication of the DNA content of the chromosomes takes place as in mitosis.
First meitotic division
The prophase of the first meiotic division is prolonged and is usually divided into a number of stages: leptotene, zygotene, pachytene, diplotene.
10. Reaction of cells for damaging actions. Reversible and irreversible changes of cells. Death of cells. Necrosis and apoptosis.
Organism and its cells constantly undergo to action of different chemical, physical or biogenic factors. When such factors act onto cell, reversible or irreversible changes are developed.
The aggregate of unspecific reversible changes of cytoplasm appeared under the action of different agents is called the paranecrosis. In the basis of paranecrosis denaturing changes of intracellular proteins lie.
In irreversible damage cell dies. During death of cell we can see coagulation and aggregation of nuclear chromatin, the caryopicnosis, destruction of nucleus, the caryorexis, solution of nucleus, the caryolysis, and also intracellular edema or lysis of cytoplasm.
Cell death. Dead and dying single cells are a common finding in tissues. In normal tissues, individual cell division may occur as part of cell turnover, during involution of tissue as part of normal embryological development or as part of cyclical changes in tissues or organs. Death of single cell also occurs in many pathological conditions. All of these examples of individual cell death are known as apoptosis.
Apoptosis is brought about by entirely different mechanisms than those that cause necrosis. It is a mode of cell and tissue death, which occurs in pathological conditions. Necrosis is caused mainly by different external factors, chemical or physical, we can watch damages of cellular functions and structures. In cell ionic composition is changed, membranous structures are edemic, synthesis of ATP, proteins, nucleic acids is stopped, degradation of DNA, activation of lysosomal enzymes occur. All this leads to solution of cell, lysis. A well-known example of necrosis is myocardial infarction, where heart muscle dies as a result of lack of oxygen. While apoptosis occurs in both pathological and normal conditions, necrosis is always pathological and is usually accompanied by an inflammatory reaction.
11 Periodization of human embryonic development. Progenesis. Morpho-functional characteristic of human sex cells.
Embryogenesis is part of ontogenesis, it includes from the moment of fertilization of oocyte by spermatozoon and formation of zygote till the birth.
Periods of embryogenesis:
1) primary 1st week of development
2) embryonic – 2-8th
3) fetal – from 9th week till the birth
Embryogenesis is closely connected with progenesis. It is period of development and mature of sexual cells – oocytes and spermatozoa.
Spermatozoa. f ormed in male genital glands –testes; they are mobile; consists of head and tail. Velocity=30-50 mm/sec, dimension=70 mm
Acrosome is flattened vesicle derives from Golgi complex. It contains enzymes necessary for penetration of spermatozoon into ovum (collagenase, acrosin, acidic phosphatase).
Tail of sperm consists of 4 sections: neck-connecting, intermediate, main, terminal. Basis of tail is axial thread – axonems consisting of 9 pairs of peripheral and 1 pair of central microtubules.
Oocyte. Is formed in female genital glands – ovaries. It contains haploid nucleus. Dimension=130mm. covered by 3 layers: internal oolema; dense brilliant zone; corona radiate.
Human oocyte is secondary isoletical type. Reserve of nutritive substances human oocyte loses during 12-24 hours after ovulation, then it is dead, if fertilization doesn’t take place.
12. Fertilization. Determination. Fotures of course of fertilization in human organism.
It is fusion of male and female sexual cells with formation of unicellular embryo – zygote with diploid number of chromosomes.
It occurs in ampular part of uterine tube. It is monospermic.
Some processes occur during fertilization.
1. Capacitation is the process of activation of sperms which occurs in oviduct under the action of mucous secretion of its glandular cells.
2. rotation of oocyte is realized at the expense of beating of sperm flagella (4rotations per minute).
3. acrosomal reaction. It is excretion of enzymes – hyaluronidase (splits proteins of hyaluronic acid present in zona pellucida) and tripsin (splits proteins of cytolemma of oocyte and cells of corona radiate) from spermatozoa. As a result corona radiate and zona pellucida disappear.
Cytolemma forms tubercle in the region of attachment of the sperm. Here sperm enters. Cortical granules move under oolema and their content is excreted into space between oolema ad zona pellucida. This is cortical reaction, at the expense of which dense membrane – fertilization membrane is formed. It prevents entry of other sperm and polyspermia.
Fusion of pronuclei.
Nuclei of female and male sexual cells transform to pronuclei, approach and stage of syncharion starts. Genomes mix and diploid number of chromosomes restores. As a result unicellular embryo – zygote is formed. After fertilization to the end of 1st day fragmentation starts.
13. Fragmentation. Determination. Characteristic of fragmentation of human embryo. Concept on morula, blastoeyst, embryoblast, trophoblast.
It is consequent mitotic division of zygote into daughter cells – blastomeres.
During fragmentation 2 types of blastomeres are formed:
1) light, from which trophoblas is formed
2) dark, from which embryoblast, body of embryo and provisory organs are formed.
Morulla
While process of fragmentation first of all compact accumulation of cells – morulla are formed.
Blastocyst
It is hollow vesicle; forms to the 4th day. Formation of blastocyst is terminal resylt of fragmentation of zygote. During 2 days (5th-7th) embryo is on stage of vacant blastocyst in cavity of uterus.
During this period in trophoblast and embryoblas changes occur. They are caused by preparing to penetration of embryo into the uterus wall – implantation.
14. Implantation. Its mechanisms. Features of implantation in human organism. Gastrulation. 'Embryonic histogenesis.
To 7th day the process of penetration of embryo into wall of uterus starts.
It lasts during 40 hours and includes 2 stages:
1) adhesion
2) invasion
In the 1st stage trophoblast fastens onto uterus mucosa and 2 layers are differentiated in it. These are cytotrophoblast and symplastotrophoblast. During the 2nd stage symplastotrophoblast produces proteolytic enzymes and destroys uterus mucosa.
Trophoblast at 1st 2 weeks uses products of destruction of maternal tissues (histiotroph type of nutrition). Further nutrition of embryo is realized immediately from maternal blood (hematotroph type of nutrition)
Gastrulation
It is process of formation of germ layers. 2 stages:
Delamination. It occurs on 7th day. Cells of embryoblast are divided into2 layers – external (epiblast; contains ectoderm, nerve lamina, mesoderm, chord) and internal (hypoblast; ectoderm).
Immigration. Starts on 14-15th day. As a result of immigration primary stria is formed. It is source of mesoderm. Embryo gets three-layered structure (ectoderm, entoderm, mesoderm)
Embryonic histogenesis.
It is process of appearance of specialized tissues from slightly differentiated cellular material of embryonic rudiments taking place during embryogenesis. Embryonic rudiments are source of development of tissues and organs during ontogenesis.
15. Concept on provisory organs of human being. Chorion, amnion, yolk sac, allantois, placenta. Their structure and functional significans.
They are organs developed during embryogenesis outside of embryo body. They realize different functions providing growth and development of embryo. Provisory organs are amnion, yolk sac, chorion, allantois, placenta.
Amnion
It is derived from wall of amniotic vesicle consisting of provisory ectoderm and provisory mesoderm of embryoblast. It participates in producing of amniotic fluid. Amnion realizes protective function preventing passing of harmful agents into embryo.
Yolk sac.
It is derived from wall of yolk vesicle consisting of provisory ectoderm and provisory mesoderm of embryoblast. It realizes trophic function till 3rd week
Allantois
Represents small finger-shaped projection of entoderm in caudal part of embryo. It is organ of gas exchange and excretion because through allantois vessels grow into chorion. On the 2nd month of embryogenesis it is reduced and forms a part of umbilical cord.
Chorion
It is derived from trophoblas and provisory mesoderm. Consists of 2 parts: smooth and villous (branchy). Function – participation in formation of placenta.
Placenta - consists of chorionic (fetal part) and decidua basalis (maternal side). Functions: Food and gas exchange fetal excretion of metabolic products of the fetus, regulation Incoming substances from mother to fetus, fetal immunological protection, production of hormones and bioactive substances necessary for the development of the fetus and pregnancy.
16. Concept on critical periods of development (P.G.Svetlov). Damage of processes of determination as reason of anomalies and deformities. The basic critical periods of development of human embryo.
Учение о критических периодах развития было создано в 1921 г. К. Стоккардом и в дальнейшем значительно углублено и расширено П. Г. Светловым. Критические периоды характеризуются наиболее высокой чувствительностью к воздействиям вредных факторов внешней среды.
П.Г.Светлов установил два критических периода в развитии плацентарных млекопитающих. Первый из них совпадает с процессом имплантации зародыша, второй — с формированием плаценты. Имплантация приходится на первую фазу гаструляции, у человека — на конец 1-й — начало 2-й недели. Второй критический период продолжается с 3-й по 8-ю неделю. В это время идут процессы нейруляции и начальные этапы органогенеза.
Повреждающие факторы внешней среды (химические агенты, в том числе лекарственные, радиация и др.) могут оказывать неодинаковое влияние на зародыши, находящиеся в разных стадиях развития: эмбриотоксическое или тератогенное. Эмбриотоксическое действие повреждающих факторов характерно для первого критического периода, тератогенное — для второго.
В период имплантации зародыш либо погибает (при повреждении многих бластомеров), либо дальнейший эмбриональный цикл не нарушается. При поражении зародыша в период плацентации и органогенеза характерно возникновение уродств. При этом пороки развития образуются в тех органах, которые в момент действия повреждающих агентов находились в процессе активной дифференцировки и развития.
Согласно учению о двух критических периодах эмбриогенеза, для снижения частоты гибели зародышей и врожденных пороков развития необходимо охранять организм женщины от неблагоприятных воздействий окружающей среды именно в первые 3—8 нед. беременности. К критическим периодам фетального развития относят 15—20-ю недели беременности (усиленный рост головного мозга) и 20—24-ю недели (формирование основных функциональных систем организма).
17. Tissues as system of slit and their appendages. Cells as leading elements of tissue. No-cellular stnictures: symplast, syntitium, intercellular substance. Stem cells and their properties. Differon.
Tissue represents system of cells and non-cellular structures realizing definite function.
Non-cellular structures:
Symplasts are large formations consisting of plasmalemma with numerous nuclei.
Example is striated muscle fibre.
Symplasts appear as a result of junction of cells or division of nuclei without division of cytoplasm of cell.
Syncytium is characterized by that after division of initial cell daughter cells stay connected with each other with the help of fine cytoplasmic bridges (e.g., mesenchyme; spermatogonia of testis keep connection with each other for a long time).
Intercellular substance is derivative of cells predominantly of mesenchyme origin: proper connective tissues, cartilage and bone.
Совокупность клеточных форм, составляющих линию дифференцировки, называют диффероном, или гистогенетическим рядом. Дифферон составляют несколько групп клеток: 1) стволовые клетки, 2) клетки-предшественники, 3) зрелые дифференцированные клетки, 4) стареющие и отмирающие клетки. Стволовые клетки — исходные клетки гистогенетического ряда — это самоподдерживающаяся популяция клеток, способных дифференцироваться в различных направлениях. Обладая высокими пролиферативными потенциями, сами они (тем не менее) делятся очень редко.
18. Regularities of appearance and evolution of tissues. Classification of tissues. Physiological and reparative regeneration.
В онтогенезе различают следующие этапы развития тканей:
· I этап топической дифференцировки – презумптивные (предположительные) зачатки тканей оказываются в определенных зонах цитоплазмы яйцеклетки, а затем и зиготы;
· II этап бластомерной дифференцировки – в результате дробления зиготы презумптивные зачатки тканей оказываются локализованными в разных бластомерах зародыша;
· III этап зачатковой дифференцировки – в результате гаструляции презумптивные зачатки тканей локализованы в различных участках зародышевых листков;
· IV этап гистогенез – процесс преобразования зачатков тканей в ткани в результате пролиферации, роста, индукции, детерминации, миграции и дифференцировки клеток.
Имеется несколько подходов к классификации тканей. Основными являютсяморфофункциональная и генетическая. Общепринятой является морфофункциональная классификация, в соответствии с которой выделяют четыре тканевых группы:
· эпителиальные ткани;
· соединительные ткани (ткани внутренней среды, опорно-трофические ткани);
· мышечные ткани;
· нервные ткани.
Физиологическая регенерация — непрерывное обновление структур на клеточном (смена клеток крови, эпидермиса и др.) и внутриклеточном (обновление клеточных органелл) уровнях, которым обеспечивается функционирование органов и тканей.
Репаративная регенерация — процесс ликвидации структурных повреждений после действия патогенных факторов; репаративную регенерацию следует рассматривать как нормальную реакцию организма на повреждение, характеризующуюся резким усилением физиологических механизмов воспроизведения специфических тканевых элементов того или иного органа.
19. General morpho-functional characteristic of epithelial tissues. Morpho-functional and genetic classification of epithelia.
- line surface of body, mucous and serous layers of internal organs and also form the number of glands.
According to this: tectorial and glandular epithelium. Tectorial is limiting tissue. It separates organism and its organs from external environment. Glandular realizes secretory function.
General morphological signs:
1. epitheliocytes are located as continuous layers and there is no intercellular substance among them
2. epithelium is located onto sharply marked basement membrane
3. blood vessels are absent in epithelium
4. it is characterized by sharply marked polarity of cells or layers
5. epithelium has high regenerative ability
Morphological classification:
In the base of morphological classification shape of cells and relation of cells to basement membrane lie. According to it – simple and stratified
20. Source of development, localization, foists of structure and functions of different types of simple epithelia.
Morphological classification:
Simple squamous – endothelium
1) mesenchyme
2) blood and lymph vessels, chambers of heart
3) consists of squamous endotheliocytes poor in organelles and containing pinocytotic vesicles
4) exchange of substances and gases between blood and surrounding tissue.
Simple cuboidal
1) mesoderm
2) renal tubules
3) consists of cuboidal epitheliocytes
4) reabsorption of substances from primary urine into blood
Simple prismatic
1) endoderm
2) organs of GIT: mucosa of stomach, small and large intestine, gall bladder, ducts of liver and pancreas
3) consists of prismatic epitheliocytes producing mucous secretion
4) participation in parietal digestion and absorption of products of splitting of food
Multi-lined ciliated epithelium
1) prechordal lamina of ectoderm
2) air-passing ways (nasal cavity, bronchi)
3) ciliated, goblet, intercalated, endocrine cells are present
4) cleaning of inspirited air from foreign particles; secretion of mucus; protecting mucosa from mechanical, infectious and other actions
21. Source of development, localization, features of structure and functions of different types of stratified epithelia.
It is epithelium which cells are located in few layers
Stratified squamous keratinizing
1) skin ectoderm
2) skin epidermis
3) consists of 5 layers: basal, spine-shaped, granular, brilliant, corneal)
4) barrier, protective
Stratified squamous non-keratinizing
1) ectoderm
2) oral cavity, esophagus, eye cornea, vagina
3) 3 layers: basal, spine-shaped, squamous
4) protective
Transitional
1) mesoderm
2) urine-passing ways (renal pelvis, ureter, urinary bladder, urethra)
3) 3 layers: basal, intermediate, superficial
4) barrier for exist of urine through the wall of organ
22. Secretory function of epithelial tissues. Glands, their structure and principles of classification. Histophysiology of secretory prosss. Types of secretion: mcrocrine, apocrine, holocrine.
Glandular epithelium consists of stroma and parenchyma
Parenchyma consists of epithelium (glandulocytes), stroma – CT with vessels and nerves
Classification
1. glands of internal secretion 2. glands of external secretion 3. glands of mixed secretion
Endocrine glands. Synthesize hormones passing immediately into blood and don’t have efferent ducts Exocrine glands. Produce secretion and excrete it into surrounding. They consist of terminal or secretory cells sections and efferent ducts through which secretion is produced.
Structure:
1. simple, having non-branched efferent duct
2. compound, having branched efferent duct
According to shape of terminal section:
1. tubular 2. alveolar 3. alveolar-tubular
Secretory cycle:
1) absorption of initial products by glandulocytes
2) synthesis and accumulation of secretion in them
3) excretion of secretion from glandulocytes
4) regeneration of their structure
Methods of secretion:
1. merocrine. Glandular cells completely keep their structure (cells of salivary glands)
2. holocrine. Is accompanied with accumulation of fat in cytoplasm and complete destruction of glandular cells (sebaceous glands)
3. apocrine. Partly destruction of glandular cells (mammary glands)
23. Concept on system of blood. Composition of blood and lymph, their main functions. Hemogram and leukocytic formula. Age-specific changes of blood.
System of blood includes: blood, lymph, organs of haemopoiesis (red bone marrow, thymus, spleen, lymphatic nodes
Functions: respiratory, transport, homeostatic, protective, excretory
Blood consists of 2 main components:
1. plasma (55-60% from blood volume)
90-93% water, 7-10% dry substances, 6-8% proteins, 1-3% other substances
2. formed elements (40-45%)
Hemogram – quantitative correlations of formed element in blood
Erythrocytes: in male 3.9-5.0*10(12)/l
In female 3.7-4.9*10(12)/l
Leucocytes = 4-9*10(9)/l
Thrombocytes = 200-300*10(9)/l
Leucocytic formula – correlation of different types of leucocytes: neutrophiles=48-78%; lymphocytes =20-35; eosinophiles = 0.5-5; monocytes = 6-8; basophils = 0-1
Lymph is a fluid of protein origin of yellowish color present in lymphatic capillaries and vessels. It consists of lymph plasma and formed elements. Lymph plasma is similar to blood plasma but has low content of proteins and less velocity. Formed elements contains lymphocytes (98%)
24. Formed elements of blood and lymph. Erythrocytes. Thrombocytes. Morphofunctional characteristic, content in blood.
Erythrocytes are non-nuclear cells without organelles. The basic function is respiratory – transport of oxygen and carbonic acid at the expense of Hb.
Number of erythrocytes:
in male 3.9-5.0*10(12)/l; Hb =130-160 gr/l
In female 3.7-4.9*10(12)/l; =120-140 gr/l
Shapes of E.: (change of shape – poikilocytosis)
1) disk-shaped
2) planocytes
3) spine-shaped or echinocytes
4) cupola-shaped or stomatocytes
5) sphere-shaped or spherocytes
E. are oxyphilic, they are stained into orange-pink color; life span – 120 days.
Thrombocytes
Are colorless corpuscles of round or oval shape. These blood platelets represent non-nuclear fragments of cytoplasm of giant cells of red bone marrow – megacaryocytes.
Each platelet consists of peripheral light part – hyalomere and central dark part – granulomere (participating in blood coagulation).
Their number is 200-300* 10(9)/l
25. Classification of leucocytes. Granulocytes a. agranulocytes. Structure, percent content according to leukocytic formula, functions.
Leucocytes are WBC, their number is 4-9*10(9)/l. all of them have nucleus.
According to morphological and tincture signs all the leucocytes are divided into: granular and agranular
Granulocytes:
1. neutrophilic – stained by basic and acid dyes into pink-violet color
2. basophilic – by basic dyes into dark blue color
3. eosinophilic – by acid dyes into bright-pink color
Neurophils
Are the most numerous group of l.; make up 48-78% from general number of L.; has the most phagocytic activity. In neurtophiles lyzozyme (bactericidic), lactoferrin (glue together bacteria), alkaline phosphotase (destroy DNA of bacteria) are present.
There are young, stick-nuclear and segment-nuclear cells.
Functions:
The basic function is antibacterial protection and they participate in inflammation reactions. Phagocytic index (number of particles absorbed by 1 cell) is equal 12-23.
Basophils
They make up 0-1% from number of L. large basophils metachromatic granules fill their cytoplasm. Basophilic granules contain heparin decreasing blood coagulation and histamine increasing permeability of vessels.
Eosinophils
Compose 0.5-5%. They contain numerous large oxyphilic glanules and a little number of azurophilic granules. Oxyphilic granules contain the main protein (destroy bacteria, helmins).
Function: antiparasitic protection. They participate in allergic and anaphylactic reaction.
Agranulocytes: lymphocytes and monocytes.
Lymphocytes. There are basic functional classes of lymphocytes – B(produce antibodies; humoral immunity) and T.(cellular immunity). Monocytes – predecessors of macrophages
26. Concept on haemopoiesis. Types of haemopoiesis. Embryonic haemopoiesis as development a blood as tissue. Its periods and their characteristic.
Haemopoiesis is the process of formation of formed elements of blood. Haemopoiesis can be:
1) embryonic
2) postembryonic
Embryonic haemopoiesis occurs in embryonic period. It leads to formation of blood as tissue. It includes 3 stages: mesoblastic, hepato-thymo-lienal stage, medullar.
Mesoblastic stage: haemopoiesis is realized in provisory organs. Haemopoietic cells appear at the end of 2nd and beginning of the 3rd week of development in provisory mesenchyme, in the wall of yolk sac, chorion. After reduction of yolk sac the liver becomes as temporal center of haemopoiesis.
Hepato-thymo-lienal stage:
a) haemopoiesis in liver. Liver is formed on 3-4 weeks of embryogenesis. Haemopoiesis in liver starts from 5-6th weeks. The source of haemopoiesis in liver is stem haemopoietic cell. From them blasts are formed, also erythrocytes, neutrophils and eosinophils are formed.
b) haemopoiesis in thymus. Thymus is founded at the end of the first month of embryogenesis. Haemopoiesis starts on 7-8 week. Beginning of formation T lymphocytes
c) haemopoiesis in spleen. Spleen is founded at the end of the first month of embryogenesis. Haemopoiesis starts from 12th week.
Medullar stage. Haemopoiesis starts in red bone marrow from 10-12th week of embryogenesis. Bone marrow is founded on the 2nd month of embryogenesis. Bone marrow provides thymus and other haemopoietic organs with stem cells of blood.
27. Postembryonic haemopoiesis. Representation on lymphoid and myeloid haemopoiesis. Unitary theory of heamopoiesis of Maximov A.A. Characteristic of stem, semistem cells and unipotent cells. Concept on colony-forming unit (CFU) of blood cells.
Postembryonic haemopoiesis is process of physiological regeneration of blood. It is realized in myeloid and lymphoid tissues composing base of haemoietic organs.
Myeloid haemopoiesis is realized in myeloid tissue: red bone marrow (located in epiphysis of tubular bones and spongy substance of flat bones). It leads to formation of erythrocytes, granulocytes, monocytes, thrombocytes.
Lymphoid haemopoiesis is realized in lymphoid tissues: thymus, lymph nodes, spleen. It leads to formation of T and B lymphocytes, plasmocytes.
Stem cells of blood are polypotent predecessors for all type of blood cells. They are self-supported population of cells. They are divided seldom. The first representation about stem cells was formulated by Maximov revealing of stem cells is possible while using of method of colony-formation. In spleen of mortally irradiated animals formation of colonies of haemopoietic cells are seen. Each stem cell forms 1 colony and is called colony-forming unit (CFU).
Unitary theory of Maximov:
All the blood cells are derived from one source – stem haemopoietic cell. There are 6 classes of cells:
1. stem cell of blood is polypotent, i.e it is able to differentiate into any formed element of blood
2. semistem cells are limitedly polypotent. They include: ancestor of myeloiesis and lymphopoiesis
3. unipotent cells are able to differentiate just into one type of formed elements of blood
4. blast cells
5. differentiating cells
6. differentiated mature cells
28.General morphofunctional characteristic and classification of connective tissues. General principles of organization of connective tissues. Features of structure, localization and cellular composition of loose fibrous connective tissue. General characteristic and structure of intercellular substance.
CT:
• Unites a large group of tissues derives from mesenchyme
• They compose more than 50% of body weight
• The basic components are cells and intercellular substance
• Intercellular substance consists of ground amorphous substance and fibers (collagen, elastic, reticular)
Functions: trophic, protective, supporting, plastic, structure-forming
Classification
I. proper CT:
1. fibrous: loose, compact (figurative, non-figurative)
2. CT with special properties: adipose, mucous, reticular, pigment
II. skeletal tissues
1. cartilage: hyaline, elastic, fibrous
2. bone: lamellar, reticulofibrous, cement and dentine of tooth
LFCT
Is present I all organs because it accompanies blood and lymphatic vessels and form stroma and layers of many organs. It is located under the basement membraes of epithelia. For its structure great number of cells ground substance ad a little number of disorderly arranged fibers are typical.
Cellular composition: fibroplasts, macrophages, tissue basophils, plasmatic cells, adipocytes, adventitial cells, pigmentocytes, pericytes of vessels, leucocytes.
Intercellular substance of CT is product of activity of fibroblasts, partly other CT and blood plasma. It consists of collagen, reticular, elastic fibers and ground amorphous substance.
29. Compact fibrous connective tissue, its varieties, localization, peculiarities of structure. Tendon as organ.
It is characterized by great number of fibers and a little number of cellular elements and of ground amorphous substance among them.
Depending on character of arrangement of fibrous structures it is divided into:
1. compact figurative (dense regular)
Arrangement of fibers is strictly put in order, in tendons, ligaments, fibrous membranes
2. compact non-figurative (dense irregular)
Is characterized by disorderly arrangement of fibers (reticular layer of dermis)
Сухожилие с остоит в основном из плотной оформленной соединительной ткани, но содержит также и рыхлую волокнистую соединительную ткань, образующую прослойки. На поперечном срезе сухожилия видно, что оно состоит из параллельно расположенных коллагеновых волокон, образующих пучки 1, 2, 3 и возможно 4 порядков. Пучки 1 порядка, наиболее тонкие, отделены друг от друга фиброцитами. Пучки 2 порядка состоят из нескольких пучков 1 порядка, окруженных по периферии прослойкой рыхлой волокнистой соединительной ткани, составляющей эндотеноний. Пучки 3 порядка состоят из пучков 2 порядка и окружены более выраженными прослойками рыхлой соединительной ткани – перитенонием. Все сухожилие окружено по периферии эпитенонием. В прослойках рыхлой волокнистой соединительной ткани проходят сосуды и нервы, обеспечивающие трофику и иннервацию сухожилия.
30. Connective tissues with special properties. Structure, localization and functional significance.
Reticular tissue
It has net-like structure; consists of reticular cells and reticular (argirophilic) fiber forming 3d-net. It forms stroma of haemopietic organs nad makes microenvironment blood cells.
Adipose tissue
2 varieties – white (widely spread in human organism=mulriocular) and brown (present in newborns=uniocular). Whire at is located under the skin, in lower part of peritoneum, on buttocks and thighs where it forms subcutaneous, in epiploon, mesogastrium and retro-peritoneal region. Brown at present in newborn on ncek near scapula, behind the sternum, along vertebra and in animals sleeping in winter. Function: participates in processes of warm-producing in newborns
Mucous CT
Present just in embrayo and is placed in umbilical cors. It consists of mucocytes synthesizing hyaluronic acid which determines jelly-like consistence of tissue. Prevents damage of placentar blood circulation.
Pigment CT
It is tissue in which number of pigment cells – melanocytes are located. To this tissue parts of skin in region of nipples, scrotum, near anal aperture, and also in in iris of eye. Protects from UV irradiation.
31. General morphofunctional characteristic of cartilage tissues. Cellular composition of cartilage tissue. Structure of hyaline, elastic and fibrous cartilaginous tissue. Perichondrium. Chondrogenesis and ageOranIted changes of cartilage.
Consists of cartilage cells (chondrocytes and chondroblasts) and a great number of hydrophilic intercellular substance.
70-80% of water, 10-15 of organic substances, 4-7 of mineral salts are present in fresh cartilage.
Cartilage tissue doesn’t contain blood vessels, its nutrition is realized at the expense of perichondrium. Perichondrium is layer of CT which covers surface of cartilage.
Cartilage cells
• Are chondrocytes and chondroblasts
• Mature cartilage cells maintain integrity of the cartilage matrix.
• Chaondrocytes are localized singly or as groups
• Groups of cells which lie in common lacunae are called isogenous groups
Chondrohistogenesis
Is development of cartilage, is derived from mesenchyme, is realized both in embryo and in postembryonic period during regeneration. Stages: formation of chondrogenic islet, formation of primary cartilage tissue, differentiation of ct
Classification
1. hyaline is the most common form of cartilage. Is located in the parcels of junctions of ribs with sternum, in throat, trachea, large bronchi, on joint surfaces of bones.
Perichondrium is absent; nutrition is realized mainly from synovial fluid of cavity of articulation; is undergone to calcification
2. elastic is located in cartilages of nose and ear shell; is yellowish; is able to stretching; contains elastic and collagen fibers; it doesn’t undergo to calcification (deposit of salts of Ca)
3. fibrocartiage forms intervertebral discs, symphysis of pubic bones
Age-related changes:
With aging amount of proteoglycans is decreased; this leads to destruction of collagen fibers.
32. Bone tissues. Morphofunctional characteristic and classification. Cellular composition of bone tissue. Intercellular substance of bone tissue. Reticulofibrous and lamellar bone tissue. Age-related changes.
It is special type of CT with calcified intercellular substance. It contains about 70 % of inorganic combinations, among them salts of Ca phosphate are predominant. The basic role is mechanical-supporting. Bones protect internal organs from mechanical injures, promote moving of body in space.
Cells of BT:
1. osteocytes. Basic cells of bt, function – providing of exchange of water, proteins and ions in bt, supporting of haemopoiesis in bt.
2. osteoblasts. Young cells; function-synthesis and srcretion of organic matrix of bone
3. osteoclasts.
Intercellular substance occupies 90% of its volume, other part are cells, lymphatic vessels. It consists of 20% of organic compounds (proteins), 65% mineral components (salts), 10 % water.
Classification
1. reticulofibrous
Is present mainly in embryo, in adults they are located on olaces of stitches of cranial bones, place of junction of tendons with bones.
2. lamellar
Is more spread type of bt in adult organism. Its structural component is bone lamina. It’s formed by bone cells and mineralized bone substances. From this tissue compact and spongy substance of number of flat and tubular bones are built
Age related changes
In young adults the rates of bone deposition and resorption are about the same. In women after menopause a decrease in bone mass occurs because bone resoption by osteoclasts outpaces bone deposition by osteoblasts. Because of women’s bone are smaller and less massive it leads to osteoporosis.
33. Bone as organ. Microscopic structure of bone. Periosteum, its structure and significance. Direct and indirect osteohistogenesis. Factors influencing to bone structure.
Bone as organ - is a complex structural formation, in which, along with the specific bone periosteum include, bone marrow, blood and lymph vessels, nerves, and in some cases cartilage.
Structural unit of bone is the osteon, ie the system of bony plates, concentrically arranged around a central channel containing blood vessels and nerves.
Periosteum. From outside bone is overed by periosteum.
Layers:
1. external (fibrous) formed by FCT
2. internal (cellular) containing osteoblasts and preosteoblasts
Through the periosteum nutritive vessels and nerves pass.
Osteohistogenesis
In embryo bt is developed from mesenchyme by 2 ways:
1. immediately from mesenchyme (direct)
2. from mesenchyme on the place of developing cartilage (indirect)
Direct ohg is typical for development of immature bt during formation of flat bones, e.g. tectorial bones of cranium
Stages: formation of skeletogenic islet in mesenchyme; differentiation of cells of skeletogenic islet; calcification of intercellular substance and formation of reticulofibrous tissue; transformation of reticulofibrous bone tissue into lamellar.
Indirect ohg. During this accumulation of cells of skeletogenic mesenchyme models of bones are formed. They consist of cartilage tissue, then these cartilage models are replaced by bone tissue at first in diaphysis, further in epiphysis.
34. General morphofunctional characteristic of muscle tissues. Morphofunctional and histogenetic classification of muscle tissues. Muscle tissues of epidermal and neural origin.
They are group of tissues having different origin and structure, but united on functional sign – contractility. They provide moving of whole organism in space and moving of different its parts and of organs inside of organism (heart, tongue, intestine)
For all groups of mt typical:
Elongated shape of their structural components; presence of longitudinally located myofibrils – special organelles providing contractility; location of mitochondria near contractile elements; presence of inclusions of glycogens, lipids.
Classification
1. morphofunctional – is based on structure of organelles of contraction:
a) striated – in which contractile organelles (myofibrils) have transversal striations. To this type of tissue skeletal and cardiac mt are related.
b) smooth mt - contractile organelles (myofibrils) doesn’t have transversal striation
2. histogenetic is based on source of development of mt:
a) mesenchyme mt – are derived from mesenchyme
b) epidermal – from skin ectoderm
c) neural – from nerve tube
d) celomic – from myoepicardial lamina of splanchnotom (ventral mesoderm)
e) somatic – from dorsal mesoderm
Epidermal origin
Source of development – skin ectoderm; localization – termialsection of sweat, mammary, salivary, lacrimal glands. The structural unit is star-shaped myoepitheliocyte. Contractile apparatus is localized in process of cell. Contraction of processes leads to excretion of secretion from gland
N eural origin: source – neuroectoderm; localization – 2 muscles of eye (dilator pupil, sphincter pupil). Structural unit is myoneurocyte.
35. Skeletal muscle tissue. Source of development. Muscle fiber as structural unit of tissue. Structure of muscle fiber. Sarcomere as structural unit of myofibril. Mechanisms of muscle contraction.
Skeletal mt is derived from myotomes of sommites. It is related to somatic type. Skeletal mt complete 35-40% from body weight. It is basic tissue of skeletal muscles. It has symplastic type of structure.
Muscle fiber consists of 2 components: myosattelites (are slightly differentiated one nuclear cell; they are located between basement membrane and plasmalemma of muscle fiber; they contain common organelles not special), myosymplast (it has number of oblong nuclei located at the periphery, immediately under the sarcolemma).
Myofibrils
It consists of thick myofilaments contatining protein myosin. Parcel of myofibril containing just thin actin myofilaments is called I-disk (light isotropic). Through the middle of I-disk Z-line passes telofragm. During contraction I-disk is decreased or disappears. Parcel of myofibril cotaining thick myosin myofilaments form A-disk (dark anisotropic) = H-line passes mesofragm.
Sarcomere
The parcel between 2 Z-lines. It is structural functional unit of myofibril.
Formula: ½ I-disk + A-disk + ½ I-disk
36. Regeneration of skeletal muscle tissue. Muscle as organ. Changes of muscle with aging and depending on life style.
Muscle as organ
Each human muscle consist of muscle fiber. Each fiber is surrounded by thin layer of LFCT called endomysium. It contains hemo and lymph vessels, nerve fibers finished as motor plate.
A few muscle fibers form bundles surrounded by more thick layer of LFCT called perimysium. Whole muscle is covered by marked layer of CT called epimysium.
Age-related changes of skeletal mt.
With aging human undergo a slow progressive loss of skeletal muscle mass that is replaced largerly by fibrous CT and adipose tissue. Volume of sarcoplasmic net is increased. Some myofibrils loose transversal striation are fragmented and myofilaments are disorganized. In myofibrils brown pigment – lipotucsin is accumulated. As a result of growth CT resiliency and elasticity are decreased. All these changes make muscle quickly tired.
37. Cardiac muscle tissue. Source of development. Classification of cardiomyocytes. Features of structure of contractile and conducting cardiomyocytes. Possibilities of regeneration of cardiac muscle tissue.
It is derived from visceral layer of mesoderm (myoepicardial lamina) – celomic type of tissue. Its structural-functional unit is cardiomyocyte. Cardiomyocytes are connected with each other by intercalated disks and form functional mt. elongated cardiomyocyte contains nucleus in the center and longitudinal striated myofibrils at the periphery. Striated myofibrils has same structure as in skeletal mt.
Types of cardiomyocyte: 1. working (contractile) 2. sinus 3. transitional 4. conducting
5. secretory
During long work (for instance, in conditions of constant arterial pressure of blood) working hypertrophy of cardiomyocytes occur.
Stem cells of cells predessors of cardiomyocytes are absent in mt so dead cardiomyocytes (in fact of myocardium are not regenerated).
38. Muscle tissue of mesenchymal origin. Smooth myocyte as structural unit of tissue. Organization of contractile apparatus. Regeneration. Age-related changes.
Smooth myocyte.
Cytoplasm of myocyte contains slightly developed common organelles place in poles o
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