6. macromolecule of tropocollage occurrence: in all types of connective and suppurting tissue 280x1,5 nm thickness 1- 20  m structure of fiber: structure of fiber: FIB RE S are of three kinds : collagen or white, reticular, and elastic White or collagen fib re s are the most common , posses little elasticity, but offer great resistance to pulling force (several hundred kg/cm 2 ) , w hite fibers are dissolved by weak acids, and yield gelatin when boiled

7. synthesis of collagenous fibers: fibroblasts, chodroblasts, osteoblasts, odontoblasts procollagen /enzyme procollagen peptidase tropocollagen

13. fibroblasts a fibrocytes

14. Reticular cells are branching cells the processes of which are generally in contact with each othe r . t wo type s of reticular cells are known nonphagocytic and phagocytic cells t he former produce reticular fibres, the latter take part in breakdown of the erythrocytes ( eg., in the spleen).

15. Fat (adipose) cells or adipocytes relatively large cells (diameter 40 to 50 mm) of oval shape t wo types of adipose cells are described: univacuolar fat cells (white) with one single large lipid droplet , the cytoplasm is reduced to only a thin rim, the nucleus is flat multivacuolar fat cells (brown) that contain numerous small droplets of oil, their nucleus is located always centrally in histological sections the lipid content of adipocytes is dissolved during dehydration and cells seem to be vacuolated.

17. mastocyte

19. M esenchyme unspecialized connective tissue from where all connective tissues derive composed of mesenchymal cells whose processes are in contact and of a ground substance that is fluid and usually without fibrils it occurs during first weeks of embryonic life

21. Loose (areolar) connective tissue consists of cells, fibers and ground substance MOBILE CELLS C ells - f ibroblasts and (histiocytes , plasma cells, mast cells, and leukocytes Fibers - c ollagen fibers very prominent and run in different directions; elastic fibers and small number of reticular fibers are present too, a ground substance is relatively fluid like it occurs within parenchymal organs (kidney, epididymis, glands etc.) a n d in tubular organs as a part of the mucosa and submucosa )

23. Dense irregullar collagenous tissue distribution: capsules, reticular layer of the dermis

24. D ense regular connective tissue fibers show an orderly parallel arrangement (tensions subject only in one direction) it forms tendons, ligaments and aponeuroses i n tendons, the collagenous fibers are only present and run parallel , few cells (fibroblasts) that are usually aligned in rows between the fibers ( on cross sections, the cells appear stellate in shape with long cytoplasmic processes extending between the collagenous bundles ) a morphous ground substance is present only in a small amount

25. a tendon (longitudinal sections)

26. Mucous tissue cells are stellate fibroblasts with anastomosing processes that lie in a mucoid jelly-like mass, the fibers are of only collagen type as Wharton' s jelly in the umbilical cord and as dental pulp of the deciduous teeth

27. Reticular tissue composed of reticular cells and reticular fibers , amorphous ground substance is negligible Cells are stellate with long cytoplasmic extensions , large and pale nucle us and abundant basophilic cytoplasm Fibers are in close appositions to cells and form more or less complicated network D istribution : forms the framework of lymphatic organs and bone marrow

28. Elastic tissue cells, fibers and not great amount of the ground substance C ells are typical fibroblasts, sparsely scattered with nuclei markedly flattened F ibers are mostly elastic and parallel oriented; a small number of reticular fibers was also described is occurred as the ligamenta flava, the true vocal cords, the ligamentum nuchae

29. Adipose tissue white adipose tissue (univacuolar) brown adipose tissue (multivacuolar) Cell; aggregated fat cells + scarsely fibroblasts, eosinophils, and mast cells Fibers; c ell s are surrounded by a web of fine reticular fibers t he closely packed fat cells form lobules in and between the m there is a rich network of blood capillaries

32. f ibrous component is represented by very fine collagenous fibers that form a feltwork Semitransparent opalescent cartilage that forms most of the fetal skeleton and that consists of cells that synthesize a surrounding matrix of hyaluronic acid, collagen, and protein; in the adult, it is found in the trachea, larynx, and joint surfaces . several isogeneous groups may unite in complexes termed as territoria between territoria the matrix stains slightly and is called as interterritorial matrix perichondrium

33. Elastic cartilage is usually yellowish in colour and opa que and more flexible than hyaline c hondrocytes are numerous and scattered singly or in small isogenous groups of two or three cells that are surrounded by capsules of the intercellular substance , fibers: elastic and collagenous th e matrix (intercellular substance) shows characteristic fibrillar appearance in H.E. preparations this is caused by presence of elastic fibers that are never totally masked by amorphous ground substance elastic fibers may be visualized by special dyes as orcein or resorcin- fuchsin

34. Elastic cartilage stained with orcein

35. White (fibrous) cartilage or fibrocartilage – NO PERICHONDRIUM is a transitional t issue between hyaline cartilage and dense fibrous connective tissue of tendons and ligaments the intercellular substance is composed of thick bundles of collagenous fibers running parallel with one another , c hondrocytes are not numerous, rounded and are arranged singly or in pairs in rows between bundles of collagenous fibers t he amorphous ground substance is inconspicuous and found only in the immediate vicinity of the chondrocytes f ibrocartilage has no true perichondrium

42. osteocytes with processes (HE)

44. diaphysis a model an osteon Haversian and Volkmans canals

45. diaphysis transversally (HE)

46. diaphysis transversally (HE)

47. diaphysis transversally (staining after Schmorl)

48. diaphysis transversally (staining after Schmorl)

50. OSSIFICATION Bones first appear as condensation of mesenchymal cells that form bone models. Most flat bones develop in mesenchyme within pre-existing membranosus sheaths; this type of osteogenesis is called intramembranous bone formation. Mesenchymal models of most limb bones are transformed into cartilage bone models which later become ossified by endochondral bone formation. Bone develops in 2 types of connective tissue; MESENCHYME & CARTILAGE INTRAMEMBRANOUS OSSIFICATION This type of bone formation occurs in the mesenchyme that has formed a membranous sheath. The mesenchyme condense and become highly vascular, some cells differentiate into OSTEOBLAST and begins to deposit intercellular substances – osteoid tissue or prebone. Calcium-phosphate is then deposited and the osteoblast are trapped in the matrix and become OSTEOCYTES , in contact by long cytoplasmic processes. The bone is developed around bloodvessels forming osteons, haversian sys. Some osteoblast remains on the surface to continue to lay down layers. Between the plates the bone remains spongy. In the spongy bone OSTEOCLASTS remove bone.

51. diaphysis transverally

52. INTRACARTILAGINOUS OSSIFICATION This type of bone formation occurs in the preexisting cartilaginous models. In a long bone the primary center of ossification occurs in the diaphysis. Here the cartilage cells increase in size, the matrix becomes calcified and the cells die. Pericondrium ---- Periosteum. Invasion of vascular connective tissue from the periosteum breaks up the cartilage. Some invading cells differentiate into hemiopoietic cells other cells differentiate into OSTEOBLASTS. About the time of birth, a secondary ossification center appears,(epiphysis) of long bones. Periosteal buds carry mesenchyme and blood vessels in and the process is similar to that occurring in a primary ossification center. The cartilage between the primary and secondary ossification centers is called the epiphyseal plate , and it continues to form new cartilage, which is replaced by bone, a process that results in an increase in length of the bone. Growth continues until the individual is about 21 years old or until the cartilage in the plate is replaced by bone. The point of union of the primary and secondary ossification centers is called the epiphyseal line.

54. diaphysis transversally (staining after Schmorl)