Tissues

1. Tissues -four primary tissue types: 1. Epithelial 2. Connective 3. Muscle 4. Neural -however: all tissues in the body develop from three germ layers 1. ectoderm - epithelial + neural 2. mesoderm - connective + muscle + some epithelial 3. endoderm – organs + some epithelial

2. Epithelial Tissue • = lining epithelium & glands • multiple functions of epithelial tissue: • 1. protection - from dehydration, pathogens • 2. synthesis • 3. regulation - e.g. body temperature • 4. excretion - e.g. waste • 5. immune response • lining epithelium = line body surfaces and cavities • glandular epithelium = secretion

3. Lining Epithelium Functions 1. Physical protection: are found on exposed surfaces of the body -protection from abrasion, dehydration, and entrance by toxins 2. Control permeability: every substance that enters the body must cross an epithelial tissue first -permeability varies from location to location -contain pores, channels, transporters and other machinery required for selective permeability -function can be modified by stimuli e.g. hormones can increase ion transport e.g. stress can alter the physical structure and thus permeability 3. Sensitivity: innervated by sensory nerves -many epithelial tissues can detect differences in the environment (e.g. heat, pressure) -convey these changes to the nervous system -one type of specialized sensory epithelium = neuroepithelium -found in special sense organs (ear, eyes, tongue)

4. Epithelial characteristics • Cellularity • Polarity • Attachment • to each other • to connective tissue • Avascularity • Regeneration

5. Epithelial characteristics 1. Cellularity: composed almost entirely of cells held together by cell junctions -very little extracellular matrix 2. Polarity: possesses an exposed surface the faces the exterior of the body - apical face -also has an attached base which is anchored to other tissues - basal face -the organelles are not uniformly distributed

6. -the BM is comprised of two layers a. closest to epithelial cell = basal lamina (glycoproteins, laminin and actin) -acts as a barrier to transport b. furthest from the epithelial cell = reticular lamina -collagen IV bundles produced by the underlying connective tissue cells -provides strength Epithelial characteristics Epithelial characteristics 3. Attachment: attached to underlying tissues via the basement membrane -BM is produced by the basal surface of the cells & connective tissue - comprised of collagen type IV and laminin

7. 1. Tight junctions: lipid portions of PMs are bound together by interlocking membrane proteins -very tight union - prevents passage of water and solutes between the two cells Epithelial characteristics Epithelial characteristics 3. Attachment: also form extensive connections between each other

8. 2. Gap junctions: two cells held together by proteins called connexons -connexons are channel proteins -materials can freely move between the two cells -passage of materials helps to coordinate the activities of the two cells e. g beating rhythm of cilia Epithelial characteristics Epithelial characteristics

9. 3. Desmosomes: comprised of cellular adhesion proteins/CAMs and proteoglycans -also form plaques and contain cadherins -the plaque attaches to the intermediate filaments of the cytoskeleton (keratin) -several types known: belt, hemi, button -hemidesmosome: attaches the cell to the basement membrane of the tissue -link to a basement membrane protein = laminin

10. Epithelial characteristics 4. Avascularity: do not contain blood vessels -must obtain nutrients via diffusion or absorption 5. Regeneration: damaged cells are replaced through differentiation of stem cells located deep within the tissue -rate of renewal depends on rate of cell death -stem cells = germinative cells -these cells are found closest to the basement membrane -migrate towards the surface and differentiate

11. Classification of Epithelia • catagorizing epithelial tissue types A. # of layers simple = 1 layer stratified = multiple **pseudo = 1 layer B. Cell shape columnar cuboidal squamous

12. Simple Epithelium Stratified Epithelium -relatively thin -cells have the same polarity - nuclei are generally aligned -very fragile - cannot provide mechanical/physical protection -line internal compartments -relatively permeable - absorptive surfaces, secretion, filtration -thicker due to multiple layers -found in areas subject to mechanical and chemical stress e.g. skin, mouth -tougher than simple epi.-organelles do not align

13. Pseudostratified Epithelium -appears to be stratified -yet the basal surface of every cell contacts basement membrane -apical surface of the cells may possess cilia (ciliated epithelium) -often has glandular epithelial cells embedded in it - cells secrete mucus -found lining absorptive organs e.g. respiratory epithelium

14. Squamous Epithelium -tile-like cells - cells are thin, flat and irregular in shape -cells interlock like tiles -simple squamous - most delicate tissue in the body -found in protected regions -many types: mesothelium - lines ventral body cavity (i.e. peritoneum of the abdomen) endothelium - lines heart and vessels

15. Squamous Epithelium -stratified squamous - where mechanical stresses are severe -cells on exposed surfaces (exposed to air) contain keratin - an intermediate filament protein that reduces water loss and provides strength = keratinized epithelium -non-keratinized epithelium is tough but must be kept moist e.g. lining of mouth

16. Transitional Epithelium -permits stretching -located in walls of the bladder, renal pelvis and the ureters e.g. bladder wall - when empty the epi. looks as if it has several layers -actual number of layers can be seen upon distension

17. Cuboidal Epithelium -cells are cubes -nucleus is in the center of the cell – very round -simple cuboidal: regions of secretion and absorption e.g. kidney tubules pancreas & salivary glands – secretion of buffers & enzymes thyroid follicles – secretion of thyroid hormones

18. Cuboidal Epithelium -stratified cuboidal: relatively rare -ducts of sweat glands and mammary glands NOT ON PRACTICAL

19. Columnar Epithelium -height is greater than their width -nuclei is close to the BM -simple columnar: provides some protection -also in areas of absorption and secretion

20. Simple columnar epithelium microvilli wandering lymphocytes -usually lines organs involved in secretion and absorption -located in the gallbladder, larger ducts of exocrine glands, gastric pits of stomach, lining of the small intestine -basally located nuclei aligned with one another -frequently the apical face is modified with cellular extensions e.g. microvilli – intestinal lining = brush border -short-lived cells – replaced every 4 to 5 days -frequently found with Goblet cells (intestine and stomach)

21. Columnar Epithelium -stratified columnar: relatively rare -two to multiple layers -only outer layer contains truly columnar cells -protection role NOT ON PRACTICAL

22. Stratified columnar epithelium

23. Columnar Epithelium -pseudostratified columnar: only a single layer -every cell contacts the BM -nuclei are at varying levels - appearance of multiple layers -exposed apical surface typically bears cilia e.g. respiratory epithelium

24. Pseudostratified -these tissues are generally ciliated

25. Function: filtration, diffusion, osmosis secretion, absorption protection, secretion, absorption protection, secretion, movement of mucus protection protection protection, secretion Location: lungs,linings of blood vessels ovaries, kidneys, certain glands linings of uterus, stomach and intestines linings of respiratory passages and reproductive outer layer of skin, oral cavity, throat larger ducts of sweat glands salivary glands and pancreas vas deferens, parts of pharynx Type: Simple squamous Simple cuboidal Simple columnar Pseudostratified columnar Stratified squamous Stratified cuboidal Stratified columnar Description: single layer, flattened cells single layer, cube-shaped cells single layer, elongated cells single layer, elongated cells multiple layers, flattened cells multiple layers, cube-shaped cells multiple layers, elongated cells

26. Glandular Epithelium • epithelial cells specialized to produce and secrete substances • gland = single epithelial cell OR multiple cells • two types of glands: 1) exocrine = secrete into ducts • e.g. sweat glands 2) endocrine = secrete directly into bloodstream e.g. thyroid, pituitary ** one gland is mixed - e.g. pancreas

27. exocrine gland structure: • Unicellular: single-celled glands • e.g. goblet cells • Multicellular glands – multiple cells grouped together • Can be classified based on: • 1. Mode of secretion • Merocrine • Apocrine • Holocrine • 2. Consistency of secretion • Serous • Mucus • Mixed • 3. Structure • shape of the secretory portion • branching pattern of the duct • simplest multi-cellular gland is a secretory sheet • e.g. gastric epithelium

28. SIMPLE COLUMNAR with GOBLET CELLS -goblet cells = unicellular exocrine glands that secrete mucus

29. exocrine gland types • 1. serous - watery fluid that contains enzymes • e.g. saliva – parotid salivary gland

30. exocrine gland types • 2. mucous - glycoproteins called mucinsthat absorb water to form a • slippery mucus

31. exocrine gland types • 3. mixed - more than one type of gland cell • -produces different types of secretions - mucus and serous • e.g. submandibular salivary gland

32. provides support • binds structures together • fills cavities • produces blood • protects organs • components: matrix + cells Connective Tissue -matrix: non-cellular support material -comprised of extracellular protein fibers – mainly collagens e.g. 1. collagen fibers (white) – type I 2. elastic fibers (yellow) 3. reticular fibers – collagen type III 4. fibronectin -plus a ground substance = water + hyaluronan (sugar), proteoglycans and glycoproteins -cells: secrete the matrix -some have become very specialized and make a very specialized matrix

33. Connective Tissues -cell types found in connective tissues: A. fibroblasts: immature cell type found in basic connective tissues -secrete the extracellular matrix -secrete main component of matrix = collagens -also produce hyaluronan = glycosaminoglycan (sugar) that gives the ground substance a viscous quality -also produces the other components of the ground substance e.g. proteoglycans • adipocytes:mature cell type of adipose tissue • -more specialized type of fibroblast – fat storage • -fill with lipid upon maturation C. melanocytes: synthesize and secrete melanin -dark, brown pigment that absorb light

34. Connective Tissues D. Macrophages (Fixed): engulf damaged and dead cells by phagocytosis -immune cell -derived from monocytes E. free macrophages: wander rapidly through the connective tissue -called monocytes when circulating in blood F. mast cells: another immune cell -synthesize and secrete histamine - inflammation response -synthesize and secrete heparin - inflammation response G. lymphocytes - immune cells (T and B cells) -differentiate into plasma cells (type of B cells) - antibodies -differentiate into T cell subtypes - assist B cells

35. Connective tissue Matrix fibers: collagen, reticular and elastic 1. Collagen fibers: long, straight and unbranched fibers made of CN type I -very concentrated and dense in tendons and ligaments -long chains of collagen protein subunits forming a triple helix -these helices are wound together - “rope” or a bundle = fibril -fibrils are then stacked together = collagen fiber -triple helix – three subunits = 2 alpha 1 chains + 1 alpha 2 chain e.g. CNI - 2 chains of CNIa1 and one chain of CNIa2 -there are nineteen types of collagen in the body = 80-90% are CNI, CNII, CNIII & CIV

36. Connective tissue: fibers 2. Reticular: made of collagen type III -2 collagen III a1+ 1 collagen III a2subunits = reticular fiber -reticular fibers interact in a different way – 3D network rather than bundles -thinner than collagen type I fibers - more flexible -abundant in the walls of hollow organs -form a supportive stroma (3D network) that supports the functional cells of these organs 3. Elastic: primarily made up of the proteins fibrillin & elastin -branching and wavy in appearance

37. Classification Embryonic: first to appear = mesenchyme -derived from mesoderm germ layer -cells are star-shaped -matrix - fine protein filaments -Mucus connective tissue - jelly-like, many regions of embryo

38. The way I organize Connective tissues • Loose – areolar CT, fat & reticular • Dense – dense (regular, irregular), elastic • Supportive – bone & cartilage • Fluid – blood (& lymph)

39. Type: Loose connective Adipose Reticular Dense Elastic Hyaline cartilage Elastic cartilage Bone Blood Description: Cells in fluid-gel matrix Cells in fluid-gel matrix Cells in fluid-gel matrix Cells in fluid-gel matrix Cells in fluid-gel matrix Cells in solid-gel matrix Cells in solid-gel matrix Cells in solid matrix Cells in fluid matrix Function: Binds organs together, holds tissues, fluids Protects, insulates and stores Supports Binds organs together Provides elastic quality Supports, protects, provides framework Supports, protects, provides flexible framework Supports, protects, provides framework Transports gases, defends against disease, clotting Types: 1. Loose 2. Dense 3. Adipose 4. Reticular 5. Elastic 6. Cartilage 7. Bone 8. Blood 9. Lymph

40. Loose connective tissues: types 1. Loose Areolar tissue -cells: are mainly fibroblasts, spaced far apart -matrix: sparse collagen I fibers, elastic fibers, mostly ground substance -cushions and can be distorted due to loose organization e.g. beneath the dermis

42. 2. Adipose tissue = fat -cells: adipocytes (fat storing fibroblasts) -matrix: small amounts in between the adipocytes (mainly CNIV) -cushions joints and organs -stores energy -insulates liposuction: suction assisted lipoplasty -removal of SQ fat

44. 3. Reticular tissue: -matrix: thin collagen III/reticular fibers woven into a 3D network – fibers are secreted by reticular cells (specialized fibroblasts) -supports walls of certain organs – e.g. liver, spleen, lymph nodes e.g. liver, spleen NOT ON PRACTICAL

45. Dense connective tissues: types -most of the tissue is densely packed extracellular matrix fibers of collagen type I -often called fibrous or collagenous tissue -type types: 1) dense regular – densely packed collagen I and elastic fibers e.g. tendons, ligaments 2) dense irregular - interwoven meshwork of fibers of CNI and elastic -e.g. dermis of skin, perichondrium of joints and periosteum of bone

46. 1. Dense Regular: -cells: few fibroblasts - matrix: multiple, closely packed collagen fibers – collagen type I -PLUS - fine network of elastic fibers – harder to see e.g. tendons, ligaments

47. 1. Dense Irregular: -cells: few fibroblasts - matrix: similar to dense regular but with little to no organization -gives the tissue strength and flexibility in multiple directions e.g. dermis of the skin

48. Dense irregular tissue • Found in the deepest layers of the dermis = also called the reticular layer (don’t confuse it with reticular tissue)

49. 2. Elastic: -yellow, elastic fibers in parallel or branching networks -walls of larger vessels, airways, hollow organs NOT ON PRACTICAL

50. Supportive Connective tissues: types -cartilage & bone 1. Cartilage: -cells = chondrocytes -matrix = collagen fibers embedded in a gel-like ground-substance -collagen type II -ground substance - water + proteoglycans -proteoglycans - protein + sugars e.g. chondroitin sulfate glucosamine -functions in support, attachment, protection -in developing child - model for future bone (endochondral bone) -avascular tissue - produces anti-angiogenic chemicals (inhibits growth of blood vessels) -therefore diffusion is the main mode of transport Proteoglycan