BIOL 2457Dr. HenrySI Leader: Madeline PerkinsChapter 4 and 5Cell Junctions (pg 114-116)Name of Junction What does it consist of? FunctionTight Junction Transmembrane proteins fuse together adjacent membranesInhibits the passage of substances between cells & prohibits leaking Adherens Junctions Contain plaque, cadherins, adhesion belts Resists separation of cells during contractile activityDesmosomes Plaque, transmembrane glycoproteinPrevent epidermal cells from separating under tension and cardiac muscles from pulling apart during contractionHemidesmosomes Transmembrane glycoprotein or “Integrins”Anchor cells to the basement membrane (DO NOT link cells to one another)Gap Junctions ConnexINS – membrane proteinsConnexONS – the tunnelsAllow cells in a tissue to communicate and rapidly move nerve impulses; Allow ions and molecules to travel and diffuse from cell to cellSudoriferous and Sebaceous Glands (pg 128 and pg’s164-165)Gland Secretion Function Other FactsMerocrine/eccrine -Watery secretion released by exocytosis-Cool the body-Salivary glands-Most numerous-Works soon after birth Apocrine -Thicker secretion released by exocytosis of a portion of the cell that has been pinched off -Cell repairs itself-Pheremones-Causes B.O.-Mammary glands-Functions after puberty-Mammary glands secrete milk fatHolocrine -Oily and waxy secretion-Whole cell explodes -Causes hair and face toget oily-PimplesSebaceous gland of the skinCeruminous -Waxy secretion (cerumen or ear wax)-Impede entrance of foreign bodies and insects-Waterproofs ear canalFunctions soon after birthSebaceous (oil) -Sebum -Prevents hair from drying out-Prevents water loss from skin-Inhibit bacteria growthRelatively inactive until pubertyEndocrine -Hormones that diffuse into bloodstream-Cell acts like sponge, squeezes to release contents-Maintains homeostasis -Thyroid