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chapter 2 Tissue Types and Functions Tissues Describe the properties, locations, functions, and varieties of the 4 different tissue types. Tissue - a collection of cells organized for a particular function Mammals have 4 types: epithelial, connective, muscle, nerve. Epithelial Properties & Location collections of cells packed together in sheets lines body surface & openings, blood vessels, and heart epithelial Functions: protection: from...... trauma UV light temperature bacteria epithelial Functions (cont): Produce secretions: tears & saliva moisten mucous traps dust excretions like urine & sweat milk from mammary cells epithelial Functions (cont): Absorbs Materials: cells lining lungs, intestines, & kidneys absorb materials from surrounding fluids cells lining blood vessels absorb from ECF epithelial Varieties: Simple - one layer Stratified - multiple layers Transitional - multiple layers that change shape epithelial Varieties: Squamous - very flat Cuboidal - cube shaped Columnar - more tall than wide Simple cuboidal single layer of cube shaped cells associated with secretion Simple columnar single layer of tall narrow cells associated with absorption Stratified squamous multiple layers of flat cells skin Transitional change shape urinary tract only skin (integument) Protection: 2 way barrier body temperature UV pain, pressure, temperature Overall health first indication! skin layers epidermis - stratified squamous, outermost dermis - connective layer containing blood vessels, nerves, & glands subcutaneous - fatty layer (hypodermis) modifications Hair: provides insulation, protection, sensation originates from follicle in dermis shaft=epithelial cells Arrector pili: when contracted hair stands upright modifications Footpads/Digital pads resists physical trauma acts as a cushion Modifications Claws hardness & durability surround last bone of toe rich blood supply around bone nourishes claw (quick) modifications Hooves made of keratin filled cells (specialized protein) similar anatomy modifications Horns keratinized epithelium that extends from skull connective Properties: several types produces matrix fibrous or smooth connective Functions: Connects, supports, protects connective Functions (cont): connect one organ or tissue to another tendons - muscle to bone ligaments - bone to bone example deep laceration of digital flexor tendon (raised toe) connective Functions (cont): support & protect bone & cartilage support hold muscles together support organs connective Varieties: tendons ligaments bone adipose blood Muscle Properties: 3 types of muscle voluntary & involuntary control muscle Location: All throughout body! muscle Function: skeletal - (voluntary) attaches to skeleton, allows movement muscle Function (cont) smooth - (involuntary) hollow organs & blood vessels movement of organs, pumping of blood muscle Function (cont) cardiac - (involuntary) heart muscle myocardial contractions muscle Varieties: skeletal striated-consists of thousands of muscle cells (myofibers) myofibers have several nuclei and a large number of mitochondria myofilaments-organized system within muscle fibers that control contractions actin/myosin - proteins making up myofilaments contraction during contractions, actin/myosin slide along one another begins with stimulation of nerve cell contractions nerve impulse stimulates Ca release from storage in ER Ca flow causes filaments to slide relaxation- cell actively transports Ca back into ER clinical practice Porcine Stress Syndrome (PSS) Ca is not transported back into ER muscles don’t relax normally clinical practice RIGOR MORTIS stiffness after death no energy supply to pump Ca back into ER muscles remain stiff CLINICAL PRACTICE MILK FEVER calving time causes low Ca (hypocalcemia) causes weakness Cardiac muscle involuntary myofilaments similar to skeletal more mitochondria no nerve impulse required pacemaker cells control rate smooth muscle lacks striations actin/myosin in different arrangement sheets around hollow openings slower contractions longer contractions smooth nervous Properties: communication nerve cells=neurons neuron soma (body) houses nucleus/organelles axon carries impulses to tissues/muscles axon bundles = nerves! dendrites begin impulse NERVOUS Location: Central Nervous System (CNS) = brain/spinal cord Peripheral Nervous System (PNS) = nerves extended throughout body nervous Function: carries electrical impulses nerve impulse resting nerve cells = Na ions are actively transported into ECF K is pumped into cytoplasm ions flow rapidly across membrane after stimulation electrical event nervous Varieties: Sensory neurons Interneurons Motor neurons sensory neurons receptors are stimulated in response to an environmental change light, heat, touch, hearing, balance, taste, smell, internal chemical receptor interneurons stimulated by sensory neurons, found in CNS controls activity motor neurons cause an action to occur stimulated by sensory or interneurons begin in CNS, extend to muscle or gland environment stimulates sensory (outside to in) sensory stimulates interneurons (inside) both stimulate motor neurons (inside to out) clinical practice certain infectious diseases may infect specific tissue types foot & mouth disease highly infectious, rapid spread usually not fatal, serious signs blisters in mouth & tongue epithelium around hooves swell injuries connective tissue damage often results from injuries fights, wildlife encounters, hit by car, abuse skin may be separated from connective tissue tying up muscle tissue damage waste products leak into bloodstream kidney damage may result horners syndrome nerve damage nerve that controls eye function is damaged pupil constriction, drooping eyelid, third eyelid protrudes, sunken eye