組織學 Historlogy

台北醫學大學/解剖學科 教授：邱瑞珍 分機號碼：3261 電子郵件信箱：[email protected]

1 Connective Tissue(II)

台北醫學大學/解剖學科 教授：邱瑞珍 分機號碼：3261 電子郵件信箱：[email protected]

2 學習目的

• Cell types • Types of the fibers • Types of the connective tissue

3 參考資料

• Junqueira's Basic Histology, twelfth edition, text and atlas, Anthony L. Mescher, McGraw-Hill Companies

4 Summary

• Cell types • Types of the fibers – fibroblast – Collagen fiber – macrophage – reticular fiber – Mononuclear – elastic fiber phagocyte system • Types of the connective – mast cell tissue – plasma cell – Loose connective – adipose cell tissue – leukocyte – Dense connective tissue – adipose tissue 5 GROUND SUBSTANCE

Highly hydrated, transparent, complex mixture of macromolecules 3 classes: glycosaminoglycans proteoglycans multiadhesive glycoproteins Fill the space between cells & fibers Viscous: a lubricant & a barrier to penetration of invaders

6 GAGs (mucopolysaccharides) liner polysaccharides formed by repeating disaccharide units a uronic acid + a hexosamine hexosamine: glucosamine or galactosamine uronic acid: glucuronic or iduronic acid largest, most unique, most ubiquitous GAGs: hyaluronic acid (hyaluronan) hyaluronic acid: form a dense, viscous network of polymers Æ bind water: important role in allowing diffusion of molecules in connective tissue, lubricating various organs & joints 7 Other GAGs: smaller covalently attached to proteins (part of proteoglycans) 4 main GAGS: dermatan sulfate chondroitin sulfates Different disaccharide keratan sulfate & tissue distribution heparan sulfate intense hydrophilic, highly viscous, polyanions: binding cations by electrostatic bonds

8 Proteoglycans a core protein + sulfated GAGs like glycoprotein: synthesized on rER, mature in Glogi, secrete from cells by exocytosis in cartilage: small binding protein forming larger structure proteoglycan aggregates cell-surface group ECM group

9 One of the most important ECM proteoglycans: aggrecan dominant proteoglycan in cartilage core protein + chondroitin sulfate, keratan sulfate chains link protein Æ hyaluronic acid

10 Cell-surface proteoglycans: syndecan core protein: spans membrane short cytoplasmic extension heparan Æ extracellular extension of core protein

Proteoglycans: bind & sequester certain signaling protein ex. Fibroblast growth factor (FGF) degradation of proteoglycans: release these factors Æ stimulate new cell growth &

ECM synthesis 11 Multiadhesive glycoproteins carbohydrate attached: branched protein: predominant important roles in adhesion of cells to substances Fibronectin: synthesized by fibroblast & epithelial cells binding sites for collagen, GAGs, integrins of cell membrane help to mediate cell adhesion & migration distributed as a network in the intercellular spaces

12 Laminin: larger, trimetric, cross-shaped participate in adhesion of epithelial cells Æ basal lamina binding sites for type IV collagen, GAGs, integrins all basal laminae: rich in laminin

13 Cells : interact with extracellular matrix by cell-surface molecules bind to collagen, fibronectin, laminin these receptors: intergrin transmembrane linker proteins relative low affinity also interact with cytoskeleton actin microfilament with talin, vinculin Interaction: effects in both directions orienting both cells & ECM in tissues 14 In connective tissue: interstitial (tissue) fluid similar to blood plasma contain a small percentage of plasma proteins low molecule weight pass through capillary

15 TYPES OF CONNECTIVE TISSUE

Connective tissue

Embryonic Adult Connective tissue connective tissue Loose Dense Specialized (areolar) mesenchyme mucous Irregular regular reticular adipose

16 Connective Tissue Proper

2 general classes of connective tissue proper: loose dense Loose connective tissue: very common type support many structure: under pressure & low friction support epithelial tissue forms a layer around small blood & lymphatic vessels fills spaces between muscle & nerve fibers

17 Loose connective tissue: Also found in papillary layer of dermis, hypodermis Linings of peritoneal & pleural cavities In glands, in the mucous membranes sometimes called areolar tissue cells, fibers, ground substances: roughly equal most numerous cells: fibroblasts & macrophages collagen, elastic, reticular: appear a moderate amount of ground substance: delicate consistency, flexible, well vascularized, not resistant to stress 18 Mammary gland

Skin Esophagus

19 Dense connective tissue: adapted to offer resistance & protection same components as loose connective tissue fewer cells predominance of collagen fibers less flexible, far more resistance to stress Dense irregular connective tissue: collagen fibers arranged in bundles without a definite orientation form 3-dimensional network providing resistance to stress from all directions often found closely with loose

20 Dense regular connective tissue: collagen bundles arranged in a definite pattern collagen fiber aligned with orientation of fibroblasts stress exerted in same direction offer great resistance to traction forces most common: tendons & ligaments

21 Tendons & ligaments: richness in collagens fibers: white & inextensible parallel, closely packed bundles of collagen very small quantity of ground substance fibrocyte: elongated nuclei parallel to fibers sparse cytoplasmic folds rarely revealed in H&E stain some ligaments: elastic fibers yellow ligament of vertebral column

22 Reticular Tissue reticular fibers form 3-dimentional networks support cells secreted by reticular cells hematopoietic organs & lymphoid organs bone marrow, lymph nodes, spleen reticular cells: dispersed along framework partially cover reticular fibers & ground substance with cytoplasmic process Mononuclear phagocyte system: dispersed also

23 Mucous tissue mainly in umbilical cord & fetal tissues abundance of ground substance chiefly hyalruonic acid jellylike tissue very few collagen fibers scattered fibroblast principal component of umbilical cord Wharton’s jelly also in pulp cavity of young teeth

24 Adipose Tissue a specialized type of connective tissue adipocyte (fat cells) predominate cane be isolated or in groups in loose or irregular connective tissue often in large aggregate located in many areas 15-20% body weight in men 20-25% in women energy stored key regulator of body’s energy metabolism

25 Adipose tissue: largest repository of energy (triglycerides) also liver, skeletal muscle (glycogen) in a state of continuous turnover sensitive to both nervous & hormonal stimuli adipocyte: release hormone & factors endocrine, signaling organ poor heat conductor thermal insulation also fill up space between tissues help organs in place subcutaneous layers of adipose tissue: shape surface of body in sole & palms: pads – shock absorbers 26 2 types of adipose tissue: different locations, structures, colors, pathologic characteristics White adipose tissue: more common type contain one large central droplet of whitish-yellow fat in cytoplasm Brown adipose tissue: multiple lipid droplets Both type: rich blood supply

27 WHITE ADIPOSE TISSUE

Cells: spherical when isolated polyhedral when closely packed Large cell: 50-150μm in diameter one huge droplet of lipid 85% cell’s weight also called unilocular in routine techniques: a thin ring of cytoplasm surrounding empty vacuole referred as signet ring cell eccentric & flattened nuclei 28 White adipose tissue: subdivided into incomplete lobules connective tissue partition rich vascular bed & nerve network fibroblast, macrophages…….. reticular fibers: fine interwoven network support cells & bind them together fresh color: white to bright yellow presence of carotenoids almost all adipose tissue in adults is this type age & gender determine the distribution & density in newborn: more uniform thickness 29 Histogenesis of white Adipose Tissue

30 Adult onset obesity: involve largely increased size or hypertrophy in adipocytes Childhood obesity: both increased adipocyte size & formation of new adipocytes early increase in number of adipocyte: predispose an individual to hyerplastic obesity in later life

31 BROWN ADIPOSE TISSUE

Color: due to numerous mitochondria (colored cytochromes) large number of blood capillaries Contain many small lipid inclusions Called multilocular Principal function: heat production More limited distribution Cells: polygonal, smaller than white Nuclei: spherical & central Connective tissue: partition Æ lobules Receive sympathetic innervation 32 Main function: produce heat by nonshivering thermogenesis best understood in hibernating species: more abundant Hibernating animals or newborn mammals: exposed to a cold environment: nerve Æ norepinephrine Æ brown adipose tissue activate hormone-sensitive lipase Æ hydrolysis of triglycerides Æ fatty acid + glycerol

33 In brown adipose tissue: fatty acids quickly metabolized increase oxygen consumption & heat production Æ elevating temperature & warming blood passing through Mitochondria: thermogenin (uncoupling protein) marker unique to brown fat permit backflow of protons energy dissipated as heat

34 Histogenesis of Brown Adipose Tissue

Also develop from embryonic mesenchyme In humans: maximal amount relative to body weight at birth largely disappears or replaced by white In adults: only in scattered areas: around kidneys, adrenal glands, aorta, mediastinum Number increase again during cold adaption from mesenchymal stem cells Autonomic nerves also: promote brown cells differentiation & prevent apoptosis 35