Chapter 20 Animal Structure and Function Structure and Function in Animal Tissue 20 1 An animal s form is not the perfect design Giraffe laryngeal nerve travels all the way down neck and turns around back to almost where it started evolution existing structures arise from previous structures Lengthens when distance is increased rather than breaking and reconnecting Vertebra embryonic development laryngeal nerve connects the brain to rudimentary structure than in fish will become gills and in tetrapods will develop into larynx Not perfect just good enough to function 20 2 Structure fits function at all levels of organization in the animal body Anatomy study of structure Physiology study of functions Emergent properties not present at preceding level of hierarchy of life result from structural and functional organization of each level s component parts Structural Hierarchy 1 Cellular muscle cells of heart function to contract each cell is branched and connected in a way that ensures coordinated contractions of all muscles 2 Tissue integrated group of similar cells that perform a common function cells are specialized and structure enables them to perform a specific task coordinated contraction 3 Organ 2 or more types of tissues that perform together to perform a task heart has nervous epithelial and connective heart pumps blood bc of coordinated contractions prev level 4 Organ System multiple organs that perform a vital body function heart is part of circulatory system w blood and blood vessels 5 Organism integrated and coordinated organ systems circulatory needs respiratory to function and nutrients from digestive system 20 3 Tissues are groups of cells with a common structure and function Tissue weave in Latin several tissues resemble woven cloth of nonliving fibers and living cells Some tissues held together by sticky substance or by special junctions between plasma membranes 20 4 Epithelial tissue covers the body and lines its organs and cavities Tightly knit cells form a protective barrier and sometimes a surface for exchange w fluid or air on the other side One side of epithelium is attached to basal lamina dense mat of extracellular matrix consisting of fibrous proteins and sticky polysaccharides Other side is apical surface faces outside of an organ or the inside of a tube or passageway Named according to of cell layers and shape of cells on apical surface o Simple epithelium single cell layer o Stratified epithelium multiple layers of cells o Squamous flat like a fried egg o Cuboidal like dice o Columnar like bricks on end Simple squamous thin and leaky exchanging materials by diffusion lines capillaries and air sacs of lungs Cuboidal and Columnar large amount of cytoplasm in cells secretion and absorption o Cuboidal tubes in kidney also in glands salivary and thyroid o Simple columnar lines intestines secretes digestive juices and absorbs nutrients o Some columnar cells have microvilli on apical surface increase SA for absorption other have cilia that move materials along surface Stratified Squamous line surfaces subject to abrasion outer skin and linings of mouth and esophagus regenerates rapidly by cell division of cells near basal lamina 20 5 Connective tissue binds and supports other tissues Consists of a sparse population of cells scattered throughout matrix the cells produce and secrete matrix usually consists of web of fibers embedded in a liquid jelly or solid Loose most widespread in the body o Matrix is loose weave of fibers in a watery fluid o Many fibers have collagen strong ropelike protein o Others are more elastic strong and resilient o Bind epithelia to underlying tissues and hold organs in place o Matrix of densely packed collagen fibers arrangement max strength o Forms tendons attach muscle to bone and ligaments connect Fibrous bones at joints Adipose o Stores fat in large closely packed adipose cells held in a very sparse matrix of loose fibers and fluid o Pads and insulates the body and stores energy o Each adipose cell contains large fat droplet that swells when fat is stored and shrinks when fat is used as fuel o Strong but flexible skeletal material o Matrix contains collagen fibers embedded in a rubbery material o Surrounds ends of bones Cartilage Bone o Matrix of collagen fibers embedded in a hard mineral substance made of calcium magnesium and phosphate o Compact region of bone contain repeating circular units of matrix each w central canal w nerves and blood vessels Blood tissues o Transports substances throughout the body functions dif from other o Extensive liquid extracellular matrix plasma water salts dissolved proteins RBCs WBCs and platelets 20 6 Muscle Tissue functions in movement Most abundant tissue in nearly all animals Long cells called muscle fibers each w many contractile proteins Skeletal Muscle o Attached to bones by tendons and is responsible for voluntary movements of animal body o Arrangement of contractile units along the length of skeletal muscle fibers gives the cells a striped or striated appearance Cardiac Muscle o Forms contractile tissue of the heart o Striated skeletal muscle under involuntary control o Muscle fibers are branched interconnecting at specialized junctions that rapidly relay signal to contract from cell to cell during heartbeat Smooth Muscle o Lack striations o In cell walls of digestive tract arteries and other internal organs o Responsible for involuntary body activities move food o Cells are spindle shaped and contract more slowly than skeletal but can sustain contractions for longer time 20 7 Nervous tissue forms a communication network Neuron nerve cell structural and functional unit of nervous tissue Senses stimuli and rapidly transmits info Found in brain and spinal cord specialized to conduct electrical impulses Cell body nucleus and other organelles Dendrites and cell body receive impulses from other neurons Axons bundled together into nerves transmit signals towards other neurons or to effector cell that can respond to stimulus Neurons outnumbered by supporting cells some of these surround and insulate axons promoting faster transmission of neuron signals Others nourish and regulate ones around them