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Chapter 40 Introduction to Animal Structure & Function Tissue a) epithelial – cover exterior & lines organs & cavities (barrier- tightly packed) b) connective – bind & support other tissues ex: loose, adipose, fibrous, cartilage, bone, blood c) nervous – transmit electrical impulses d) muscle – long, excitable cells with parallel microfilaments *most abundant in animals Homeostasis • maintaining internal balance • negative feedback – reaction to shifts in variations that reverse mechanisms • positive feedback – triggers mechanisms to amplify rather than reverse the change Bioenergetics -exchange of energy with the environment -minimum metabolic rates for endotherms are generally higher than for ectotherms -rate is inversely related to body size Chapter 41 Animal Nutrition •Heterotrophic by a variety of methods Stages of food processing: a) ingestion – 1st stage; act of eating b) digestion – enzymatic breakdown of food into monomers for absorption *must occur in specialized compartment where hydrolytic enzymes can attack food molecules without damaging the animal’s own cells c) absorption – uptake of nutrients by body cells d) elimination – passage of undigested materials out of the body in feces Intracellular digestion Food particles engulfed & digested in vacuoles Extracellular digestion In gastrovascular cavity or alimentary canal alimentary canal • complete with two openings mouth pharynx – esophagus crop gizzard intestine anus Mammalian digestive system • 1-way tract; separated by sphincters • peristalsis moves material through • accessory glands that add to tract via ducts: salivary glands pancreas liver (stores bile in gall bladder) 1) oral cavity –site of mechanical digestion & start of chemical digestion • >1L of saliva secreted each day • Contains mucin (glycoprotein) & amylase (hydrolytic enzyme) • bolus – ball of food; pushed to pharynx to be swallowed 2) esophagus – carries by peristalsis to stomach -cardiac sphincter 3) stomach – stores food & grinds; secretes gastric juice (~3L per day) 4) small intestine - >6m in humans; most digestion & almost all absorption *1st 25cm duodenum, jejunum, ileum – absorb; great surface area due to villi & microvilli with blood vessels *liver – secretes bile to emulsify fats *pancreas – secretes digestive enzymes (zymogens) – breakdown proteins -Ileocecal valve 5) large intestine (colon) – reabsorbs water; cecum with appendix 6) rectum – terminal part of colon -2 anal sphincters – 1 voluntary & 1 involuntary Vertebrate digestive system • dentition dictates diet • herbivores – longer alimentary canals with specialized chambers where symbionts digest cellulose • diet – carbohydrates –stored as glycogen, fats (in adipose tissue) are fuel • vitamins & minerals necessary cofactors for enzyme action Chapter 42 Circulation & Gas Exchange • O2, CO2, nutrients & metabolic waste exchange across fluid bathed membranes • diffusion is too slow to all cells, so transport system is necessary • Invertebrates: gastrovascular cavity (Cnidarians,flatworms) *circulatory system (open or closed) • Vertebrates: closed system with blood vessels & 2-4 chambered heart *capillaries connect arterioles & venules *veins – carry blood back to heart *arteries – carry blood away from heart -1 way flow with valves **pulmonary circulation – to/from lungs **cardiac – through heart **systemic – to/from body • heart rate (pulse) determines cardiac output – volume of blood pumped into systemic circulation per minute, which determines pressure • coordinated by conduction system in sinoatrial (SA) node (pacemaker) – initiates wave of contraction that spreads to both atria,hesitates at atrioventricular (AV) node, then to both ventricles • capillary exchange – substances traverse epithelium by diffusion or are dissolved in fluids & forced out by blood pressure at atrial end Blood • • • • Suspension of cells in plasma (~90% water) ~4-6L of blood on avg. pH of ~7.4 RBC (erythrocytes) ~25 trillion in blood -transport O2 (RBC & WBC produced in red bone marrow) • WBC (leukocytes) 5 types -phagocytize bacteria & debris & produce antibodies • platelets – fibrinogen allows clotting Respiration • gills – aquatic • tracheae – insects • lungs – most terrestrial vertebrates – enclosed in double walled sac • nose/mouth – inhale air to pharynx • trachea – transports air to lungs; branches into bronchi bronchioles alveoli • epiglottis covers opening to trachea (glottis) • negative pressure breathing in mammals Weddell seal Chapter 43 The Body’s Defenses Lymphatic system • Returns fluid to blood & aids in body defense; nodes help fight infection Nonspecific defense (general) 1) skin/mucus membranes – 1st line 2) phagocytes (macrophages) – 2nd line complement (group of ~20 proteins) • Inflammatory response: *prostaglandin – increases blood flow *histamines – cause vasodilation Specific defense • Humoral immunity – cells (lymphocytes) stimulated to secrete antibodies B cells – proliferate in bone marrow T cells – mature in the thymus *both come from stem cells in the bone marrow & recognize specific pathogens antigens – foreign molecules that elicit a response by lymphocytes & are recognized by B & T cells antibodies – soluble proteins secreted by B cells during an immune response Specific defense B or T cell activation occurs when an antigen binds to a B or T cell The lymphocyte forms 2 clones of cells in a process called clonal selection,resulting in thousands of cells, all specific to this antigen. effector cells combat the antigen memory cells (long-lived) bear receptors for the same antigen allowing them to quickly mount an immune response in subsequent infections Specific defense T-cell receptors bind antigens that are displayed by antigen-presenting cells (APCs) on their MHCs (major histocompatibility complex)proteins that are the product of a group of genes Specificity of B & T cells is a result of shuffling & recombination of several gene segments & results in >1million different B cells & 10 million different T cells, ea. responding to only 1 antigen Specific defense Cytotoxic T cells destroy body cells that are infected by a pathogen or cancer cells Helper T cells activate both B and T cells Chapter 44 Regulating the Internal Environment Adaptations 1) body insulation 2) vasodilation/vasoconstriction 3) countercurrent heat exchangers 4) panting, sweating, bathing 5) liver has multiple functions in homeostasis Torpor • Physiological state characterized by decrease in metabolism, heart, respiratory rates; enables temperatures withstanding varying unbearable temperatures or absences of food/water • ex: aestivation (summer torpor) & hibernation Osmoregulatory mechanisms 1) transport epithelia – single sheet of cells facing ext. env. or some channel that leads to exterior through an opening on body’s surface; transports salt followed by osmotic flow of water Osmoregulation • Balance is essential • Requires mechanisms of osmoregulation 2 basic: 1) osmoconformers (most marine inverts.) – marine animals that are isotonic with their SW environments; do no actively adjust 2) osmoregulators (most marine verts.) – animals whose body fluids are not isotonic with ext. env.; either discharge or take in water in hypertonic env. Adaptations • FW organisms: -take in H2O from hypotonic env. by contractile vacuoles (in Protozoa); excrete lots of dilute urine • Terrestrial animals: -protect against desiccation by drinking & eating high content water foods & by hormonal & nervous control of thirst, behavioral adaptations & excretory organs that conserve water Osmoregulatory mechanisms tubular systems – a) protonephridia (in flatworms) - network of closed tubes lacking internal openings & capped by flame bulbs – excrete dilute fluid b) metanephridia – internal openings that collect body fluids (in most annelids) – pump out salt for reabsorption & dilute urine is excreted c) Malpighian tubules – remove nitrogenous waste from hemolymph – produce dry waste matter Kidney • compact organ with many excretory tubules • consisting of nephrons & collecting ducts associated blood vessels Nephron a) Bowman’s capsule – surrounds ball of capillaries called glomerulus b) Proximal tubule c) Loop of Henle d) Distal tubule *collecting duct gets fluid from several nephrons & passes urine to kidney’s central receptacle (renal pelvis); urine carried by ureter to urinary bladder • Kidney’s transport epithelia regulate blood composition • Nephrons control is through: a) filtration - blood pressure nonselectively filters water & small solutes from glomerulus into lumen of nephron tubule b) secretion – additional substances destined for excretion are directly secreted from interstitial fluid into tubule by active & passive transport c) reabsorption – filtered substances that must be returned to blood, such as vital nutrients & water are reabsorbed from filtrate at various points along nephron • Most salt & water filtered from blood is reabsorbed by proximal tubule; NH3, drugs, H+ are selectively secreted into filtrate; glucose & AA’s actively transported out of filtrate; K+ reabsorbed Mammalian kidney • terrestrial adaptation • water-conserving • collecting duct carries filtrate through medulla; water exits by osmosis • urea diffuses out of tubule, joining salt in forming osmotic gradient enabling kidney to produce urine hypertonic to blood • regulation varies as it moves through nephron • produces 2 solute gradients making hypertonic urine • body’s hydration needs determine osmoregularity of urine • ADH (antidiuretic hormone) – released in response to rise in blood osmolarity signaled by osmoreceptor cells in hypothalamus, triggering increased water reabsorption by tubule • JGA (juxtaglomerular apparatus) – responds to decreased blood pressure or blood volume by releasing renin triggering formation of angiotensin II (peptide) causes vasoconstriction & releases aldosterone stimulating reabsorption of Na+ & passive flow of H2O from filtrate Adaptations • Excretion of N wastes are secondary function of kidney through evolution • NH3 excreted as: 1) NH3 in most aquatic animals through gills or ext. surfaces 2) urea (less toxic) – converted by liver in mammals & amphibians, excreted in conc. forms with minimal water loss 3) uric acid – insoluble precipitate, excreted in pastelike urine of land snails, insects, birds, reptiles *reproductive mode of terr. animals is related to Nwaste form