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Histology

1. CONNECTIVE TISSUE AND EPITHELIAL TISSUE

2. SUPPORTING TISSUE/CONNECTIVE TISSUE General structure,mechanical strength , space filling and physical and metabolic support 3 structural properties Tensile strength-collagen Elasticity-elastin Volume-glycoproteins and complex carbohydrates forming wet gel ground substance Fibres+ground substance form extracellular matrix.

3. Micrograph showing components of connective tissue Components of connective tissue from submucosa of bowel wall Main component- bundles of pink stained fibrous proteins Ground substance unstained seen as pale spaces Cells seen are fibroblasts and a blood vessel

4. Mesenchyme Embryological tissue from which all connective tissue are derived . Unspecialised Capable of differentiation Cells-delicate branching extensions which form interlacing network Nuclei-dispersed chromatin,visible nucleoli . Matrix-b l ue staining ground substance without mature fibres facilitating diffusion to and from developing tissue .

5. Fibres of connective tissue COLLAGEN Most abundant protein -provides tensile strength t o organs Type1 collagen- skin,tendon,ligaments,bone Type II collagen-hyaline cartilage Type III collagen-liver, bone marrow, lymphoid organs(delicate branched supporting meshwork known as reticulin ) Type IV collagen-basement membranes Type VII collagen-anchoring fibrils links extracellular matrix to basement membranes

6. Longitudinal and transverse section of fascia from hand( type 1 collagen)

7. Collagen from dermis of skin

8. Reticulin fibres (type III collagen) delicate supporting framework-endocrine glands,lymph nodes bone marrow, liver. Stain poorly in H&E but are able to absorb metallic silver and stains black

9. Fine reticulin scaffolding of the liver framework supports hepatocytes and the sinusoids through which blood flows

10. ELASTIN Arranged as fibres or discontinuous sheets in the extracellular matrix Stretching and elastic recoil Synthesised by fibroblasts Precursor monomer tropoelastin Present in large amount in lung, skin, urinary bladder, wall of blood vessels.

11. Ground substance Amorphous transparent material with physical character of semi solid gel Mixture of glycoprotein and complex carbohydrates Long unbranched polysaccharide chains of repeating units of uronic acid and amino sugars such as n acetyl glucosamine-glycosaminoglycan

12. BASEMENT MEMBRANE Sheet like arrangements of extracellular matrix proteins which act as interface between supporting tissues and epithelial or parenchymal cells main components; Heparan sulphate Type IV collagen Structural glycoproteins- fibronectin,laminin,and nidogen-1 Structural framework is a fine meshwork of type IV collagen

13. ADIPOSE TISSUE Cells specialized for storage of fat-adipocyte. Derived from mesenchyme Precursors to adipocytes- lipoblasts There are 2 main types-white adipose tissue and brown adipose tissue

14. WHITE ADIPOSE TISSUE White adipose tissue is pale staining because all cell is occupied by lipid which is dissolved out in paraffin embedded preparations Cell membrane and a thin rim of cytoplasm gives a chicken wire appearance Nucleus displaced to one side

15. Brown adipose tissue Found particularly in newborns, adults- thigh , nape of neck,around adrenals Rich in mitochondria specialized for generation of heat plays important part in body temperature regulation Microscopy-arranged as lobules separated by fibrous septa Cells at centre are pink stained due to mitochondria periphery-pale stained cytoplasm due to multiple vesicles containing lipid. Involved in non shivering thermogenesis-an increase in metabolic activity to produce heat induced by cold stress

16. Compared to adipocytes nuclei are large and surrounded by strongly eosinophilic cytoplasm

17. EPITHELIAL TISSUE Diverse group of tissue that includes both surface epithelia and solid organs. Classification of epithelia according to: Number of cell layers Type of cell Special features

18. SIMPLE EPITHELIA Surface epithelium consisting of single layer of cells. Cells range in shape from flat to columnar depending on function. Found in air sacs of lung(alveoli),lining of blood vessels(endothelium) and lining of body cavities(mesothelium).

19. Simple squamous epithelium Composed of single layer of flattened polygonal cells forming continuous surface. Functions; Diffusion and filtration Lines blood vessels( endothelium),body cavities( pleural,pericardial,peritoneal )and parietal layer of bowmans capsule.

20. Simple cuboidal epithelim On the surface of epithelium cells are polygonal In shape They appear square shaped in the section drawn perpendicular to surface epithelium Nucleus is round and centrally placed Function- secretion,absorption and excretion Seen in thyroid follicles,small ducts of glands,tubules of kidney and surface of ovaries

21. SIMPLE COLUMNAR EPITHELIUM Cells are taller and appear columnar in sections perpendicular to basement membrane. Nuclei are elongated and are close to base of the cells,centre or occasionally apex of cytoplasm - polarity of nucleus Main function secretion and absorption Lines internal surface of stomach,intestines,uterus and gall bladder.

22. Simple columnar ciliated epithelium Simple columnar epithelia having surface cilia. Cilia are much larger than microvilli Each cilia is a projection of plasma membrane its cytoplasm containing modified microtubules. Waving motion of cilia propels fluid or minute particles over epithelial surface.

23. Pseudostratified columnar epithelium All cells rest on basement membrane but only some of them reach surface. Nuclei are at different levels creating illusion of stratification. Larger airways of respiratory tract are lined by pseudostratified ciliated columnar epithelium-respiratory epithelium

24. STRATIFIED EPITHELIUM Stratified squamous epithelium Keratinised stratified squamous epithelium Cells in the deepest layer are cuboidal or columnar in shape. The superficial cells are polygonal in shape. Polygonal cells gradually flatten and their nuclei becomes flat. Near the surface epithelium cells are keratinised and makes the surface dry These cells are dead and flat in shape without a nucleus.

25. Non keratinising stratified squamous epithelium No superficial layer of dead cells Acts as a barrier and protects against mechanical injuries Lines oral cavity , oesophagus, vagina,anal canal

26. Stratified cuboidal epithelium Two or three layered cuboidal epithelium . seen in ducts of salivary and sweat glands . provide slightly higher protective barrier effect than simple epithelia .

27. TRANSITIONAL EPITHELIUM Stratified epithelium with capacity to stretch Lines most of urinary passage also known as urothelium Basal cells are roughly cuboidal intermediate cells are polygonal and surface cells are large and rounded(umbrella or dome cells) and may contain two nuclei.

28. Intercellular junctions

29. GLANDS Secretory cells derived from epithelia get organised along with supportive connective tissue to form gland. Gland –are subclassified according to their morphology and means of secretion

30. Simple tubular glands Single straight tubular lumen into which secretory products are discharged Secretory cells line entire duct Secretory cells are goblet cells

31. Simple coiled tubular Each has a single tube coiled in 3 dimensions Portion of glands are seen in various planes of section. Eg:Sweat glands

32. SIMPLE BRANCHED TUBULAR Found mainly in stomach Each gland has several tubular secretory portions which converge to a single unbranched duct Mucus cells line the duct but do not have a goblet shape

33. SIMPLE ACINAR GLANDS Occur in the form of pockets in epithelial surface and are lined by secretory cells Mucus secreting glands of penile urethra Secretory cells are pale stained.

34. Simple branched acinar glands Each gland has several secretory acini that empty into single excretory duct. Example sebaceous gland-secretory product accumulate within cells and are discharged by degeneration of cells.

35. Compound branched tubular gland Duct system is branched-glands are compound glands Secretory portion have a tubular form which is branched and coiled Eg-brunners gland of duodenum

36. Compound acinar gland Secretory units are acinar and drain into branched duct system. eg;Pancreatic acini draining into branched excretory ducts.

37. Compound tubulo acinar glands Have three types of secretory units- branched tubular branched acinar branched tubular with acinar end piece called demilunes eg;submandibular salivary gland

38. REVIEW OF EPITHELIUM