Loose Connective Tissue (1).docx

Loose Connective Tissue Aerolar – refers to amount of collagen that is present, appears as though the tissue is “empty” Found beneath all epithelia, between muscles, passageways for nerves and blood vessels   Adipose- Any tissue in which adipocytes are predominate - adipocytes occur individually...

Loose Connective Tissue Aerolar – refers to amount of collagen that is present, appears as though the tissue is “empty” Found beneath all epithelia, between muscles, passageways for nerves and blood vessels   Adipose- Any tissue in which adipocytes are predominate - adipocytes occur individually or in small clumps in many other connective tissues but a tissue predominantly composed of adipocytes Specialized for storage of triglycerides, regulate metabolism (endocrine function of adipocytes important in energy homeostasis), thermal insulation, cushioning of organs Lipid washes away in processing and cells appear empty Lipid can be preserved and stained with osmium tetroxide – in which case the lipid will appear black 15-20% of body weight in men and slightly more than that in women White adipose tissue White adipose tissue -is specialized for long term energy storage Large adipocytes with a single large lipid droplet (unilocular) Cells appear empty with a ring of cytoplasm and peripheral nucleus Other organelles are located near the nucleus or throughout the ring of cytoplasm Abundant smooth ER (used for lipid catabolism) Abundant vasculature (microvasculature)   White adipocytes store triglycerides from Dietary fats brought to adipocyte via a chylomicron Chylomicrons are large (1200 nm) absorbed by small intestine Chylomicron contains TG in center surrounded by phospholipids, cholesterol, and apolipoproteins Lipids synthesized by the liver and transported by VLDL (very low density lipoprotein) Smaller (30-80 nm) but similar composition to chylomicrons Amount of VLDL, LDL, and HDL in blood is indicative of cardiovascular health and or disease Free fatty acids and glycerol synthesized by the adipocyte   Brown adipose tissue Brown Adipose Tissue Multilocular, nucleus more centrally located, found adjacent to blood capillaries 2-5% of newborn body weight – concentrated mainly in the neck, back and shoulders Decreases in concentration during childhood Functions to cause heat production and warm the blood without shivering Hibernating animals and newborn humans initiate heat production by stimulation of adipocytes by norepinephrine. TG are broken down to fatty acids and glycerol. Unlike white fat, these fatty acids are not released but are metabolized. Increases in cell metabolism result in increased heat production. Brown adipocytes generate more heat than other metabolic cells because their mitochondria contain more uncoupling protein in the inner mitochondrial membrane (UCP1 or thermogenin). UCP1 allows protons to flow across the inner mitochondrial membrane from the intermembrane space into the matrix without passing through the ATP Synthase protein. Instead of ATP production, the terminal step in cellular respiration now produces primarily heat. This is especially important in newborns because they have a reduced capacity for thermostasis (homeostasis of body temperature).     Reticular Connective Tissue- Specialized CT with Type III collagen – forms fine networks/mesh called reticulin Cells producing reticular fibers are called reticulocytes (modified fibroblasts) Found in stroma of soft hematopoietic and lymphoid organs Do not stain with H&E but stain with silver stain   Dense Connective Tissue Dense Regular Connective Tissue (DRCT)- Consists of same components as DICT but the collagen fibers are arranged parallel to each other Increased resistance to stress in one direction Found in tendons and ligaments Fibroblasts may be inactive fibrocytes – also known as tendinocytes May be difficult to distinguish as they don’t stain much darker than the surrounding collagen   Dense Irregular Connective Tissue (DICT)- Densely packed, seemingly randomly arranged, collagen fibers Fewer cells and less ground substance Withstands unpredictable stresses Found in the deeper layers of skin (dermis); capsules around organs   Elastic Connective Tissue Branching, densely packed elastic fibers Able to stretch and recoil Found in walls of large arteries, trachea, vocal cords