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 :rueijen@tmu.edu.tw 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 :rueijen@tmu.edu.tw 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 fibroblast macrophage Mononuclear phagocyte system mast cell plasma cell adipose cell leukocyte Types of the fibers Collagen fiber reticular fiber elastic fiber Types of the connective tissue Loose connective tissue 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 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 keratan sulfate heparan sulfate intense hydrophilic, highly viscous, Different disaccharide & tissue distribution 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 hyaluronic acid 10
Cell-surface proteoglycans: syndecan core protein: spans membrane short cytoplasmic extension heparan extracellular extension of core protein Proteoglycans: bind & sequester certain signaling protein ex. Fibroblast growth factor (FGF) degradation of proteoglycans: release these factors 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 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 connective tissue Loose (areolar) Adult Connective tissue Dense Specialized 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 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 norepinephrine brown adipose tissue activate hormone-sensitive lipase hydrolysis of triglycerides fatty acid + glycerol 33
In brown adipose tissue: fatty acids quickly metabolized increase oxygen consumption & heat production 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