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Basic Principles of Animal Form and Function

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1 Basic Principles of Animal Form and Function
Chapter 40 Basic Principles of Animal Form and Function

2 Overview: Diverse Forms, Common Challenges
Anatomy is the study of the biological form of an organism Physiology is the study of the biological functions an organism performs The comparative study of animals reveals that form and function are closely correlated Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

3 Fig. 40-1 Figure 40.1 How does a jackrabbit keep from overheating? For the Discovery Video Human Body, go to Animation and Video Files.

4 Size and shape affect the way an animal interacts with its environment
Concept 40.1: Animal form and function are correlated at all levels of organization Size and shape affect the way an animal interacts with its environment Many different animal body plans have evolved and are determined by the genome Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

5 Physical Constraints on Animal Size and Shape
The ability to perform certain actions depends on an animal’s shape, size, and environment Evolutionary convergence reflects different species’ adaptations to a similar environmental challenge Physical laws impose constraints on animal size and shape Video: Shark Eating Seal Video: Galápagos Sea Lion Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

6 (a) Tuna (b) Penguin (c) Seal Fig. 40-2
Figure 40.2 Convergent evolution in fast swimmers (b) Penguin (c) Seal

7 Exchange with the Environment
An animal’s size and shape directly affect how it exchanges energy and materials with its surroundings Exchange occurs as substances dissolved in the aqueous medium diffuse and are transported across the cells’ plasma membranes A single-celled protist living in water has a sufficient surface area of plasma membrane to service its entire volume of cytoplasm Video: Hydra Eating Daphnia Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

8 Mouth Gastrovascular cavity Exchange Exchange Exchange 0.15 mm 1.5 mm
Fig. 40-3 Mouth Gastrovascular cavity Exchange Exchange Exchange Figure 40.3 Contact with the environment 0.15 mm 1.5 mm (a) Single cell (b) Two layers of cells

9 Multicellular organisms with a sac body plan have body walls that are only two cells thick, facilitating diffusion of materials Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

10 More complex organisms have highly folded internal surfaces for exchanging materials
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

11 Figure 40.4 Internal exchange surfaces of complex animals
External environment CO2 Food O2 Mouth Animal body Respiratory system Blood 50 µm 0.5 cm Lung tissue Nutrients Cells Heart Circulatory system 10 µm Interstitial fluid Digestive system Figure 40.4 Internal exchange surfaces of complex animals Lining of small intestine Excretory system Kidney tubules Anus Unabsorbed matter (feces) Metabolic waste products (nitrogenous waste)

12 In vertebrates, the space between cells is filled with interstitial fluid, which allows for the movement of material into and out of cells A complex body plan helps an animal in a variable environment to maintain a relatively stable internal environment Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

13 Hierarchical Organization of Body Plans
Most animals are composed of specialized cells organized into tissues that have different functions Tissues make up organs, which together make up organ systems Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

14 Table 40-1

15 Tissue Structure and Function
Different tissues have different structures that are suited to their functions Tissues are classified into four main categories: epithelial, connective, muscle, and nervous Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

16 It contains cells that are closely joined
Epithelial Tissue Epithelial tissue covers the outside of the body and lines the organs and cavities within the body It contains cells that are closely joined The shape of epithelial cells may be cuboidal (like dice), columnar (like bricks on end), or squamous (like floor tiles) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

17 The arrangement of epithelial cells may be simple (single cell layer), stratified (multiple tiers of cells), or pseudostratified (a single layer of cells of varying length) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

18 Epithelial Tissue Cuboidal epithelium Simple columnar epithelium
Fig. 40-5a Epithelial Tissue Cuboidal epithelium Simple columnar epithelium Pseudostratified ciliated columnar epithelium Stratified squamous epithelium Figure 40.5 Structure and function in animal tissues Simple squamous epithelium

19 Apical surface Basal surface Basal lamina 40 µm Fig. 40-5b
Figure 40.5 Structure and function in animal tissues 40 µm

20 Connective tissue mainly binds and supports other tissues
It contains sparsely packed cells scattered throughout an extracellular matrix The matrix consists of fibers in a liquid, jellylike, or solid foundation Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

21 Connective Tissue Loose connective tissue Cartilage Fibrous connective
Fig. 40-5c Connective Tissue Collagenous fiber Loose connective tissue Chondrocytes Cartilage 120 µm 100 µm Elastic fiber Chondroitin sulfate Nuclei Fat droplets Fibrous connective tissue Adipose tissue 30 µm 150 µm Figure 40.5 Structure and function in animal tissues Osteon White blood cells Bone Blood 700 µm 55 µm Central canal Plasma Red blood cells

22 It is divided in the vertebrate body into three types:
Muscle Tissue Muscle tissue consists of long cells called muscle fibers, which contract in response to nerve signals It is divided in the vertebrate body into three types: Skeletal muscle, or striated muscle, is responsible for voluntary movement Smooth muscle is responsible for involuntary body activities Cardiac muscle is responsible for contraction of the heart Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

23 Muscle Tissue Skeletal muscle Cardiac muscle Smooth muscle Multiple
Fig. 40-5j Muscle Tissue Multiple nuclei Muscle fiber Sarcomere Skeletal muscle Nucleus 100 µm Intercalated disk 50 µm Cardiac muscle Figure 40.5 Structure and function in animal tissues Smooth muscle Nucleus Muscle fibers 25 µm

24 Nervous tissue contains:
Nervous tissue senses stimuli and transmits signals throughout the animal Nervous tissue contains: Neurons, or nerve cells, that transmit nerve impulses Glial cells, or glia, that help nourish, insulate, and replenish neurons Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

25 Nervous Tissue Neuron 40 µm Axons Blood vessel Dendrites Cell body
Fig. 40-5n Nervous Tissue 40 µm Dendrites Cell body Axon Glial cells Neuron Figure 40.5 Structure and function in animal tissues Axons Blood vessel 15 µm

26 Coordination and Control
Control and coordination within a body depend on the endocrine system and the nervous system The endocrine system transmits chemical signals called hormones to receptive cells throughout the body via blood A hormone may affect one or more regions throughout the body Hormones are relatively slow acting, but can have long-lasting effects Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

27 (a) Signaling by hormones (b) Signaling by neurons
Fig. 40-6 Stimulus Stimulus Endocrine cell Neuron Axon Signal Hormone Signal travels along axon to a specific location. Signal travels everywhere via the bloodstream. Blood vessel Signal Axons Figure 40.6 Signaling in the endocrine and nervous systems Response Response (a) Signaling by hormones (b) Signaling by neurons

28 Concept 40.2: Feedback control loops maintain the internal environment in many animals
Animals manage their internal environment by regulating or conforming to the external environment Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

29 Regulating and Conforming
A regulator uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuation A conformer allows its internal condition to vary with certain external changes Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

30 (temperature conformer)
Fig. 40-7 40 River otter (temperature regulator) 30 Body temperature (°C) 20 Largemouth bass (temperature conformer) 10 Figure 40.7 The relationship between body and environmental temperatures in an aquatic temperature regulator and an aquatic temperature conformer 10 20 30 40 Ambient (environmental) temperature (ºC)

31 Homeostasis Organisms use homeostasis to maintain a “steady state” or internal balance regardless of external environment In humans, body temperature, blood pH, and glucose concentration are each maintained at a constant level Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

32 Response: Heater turned off Room temperature decreases Stimulus:
Fig. 40-8 Response: Heater turned off Room temperature decreases Stimulus: Control center (thermostat) reads too hot Set point: 20ºC Figure 40.8 A nonliving example of negative feedback: control of room temperature Stimulus: Control center (thermostat) reads too cold Room temperature increases Response: Heater turned on

33 Feedback Loops in Homeostasis
The dynamic equilibrium of homeostasis is maintained by negative feedback, which helps to return a variable to either a normal range or a set point Most homeostatic control systems function by negative feedback, where buildup of the end product shuts the system off Positive feedback loops occur in animals, but do not usually contribute to homeostasis Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

34 Concept 40.3: Homeostatic processes for thermoregulation involve form, function, and behavior
Thermoregulation is the process by which animals maintain an internal temperature within a tolerable range Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

35 Endothermy and Ectothermy
Endothermic animals generate heat by metabolism; birds and mammals are endotherms Ectothermic animals gain heat from external sources; ectotherms include most invertebrates, fishes, amphibians, and non-avian reptiles Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

36 Endothermy is more energetically expensive than ectothermy
In general, ectotherms tolerate greater variation in internal temperature, while endotherms are active at a greater range of external temperatures Endothermy is more energetically expensive than ectothermy Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

37 (a) A walrus, an endotherm
Fig. 40-9 (a) A walrus, an endotherm Figure 40.9 Endothermy and ectothermy (b) A lizard, an ectotherm

38 Variation in Body Temperature
The body temperature of a poikilotherm varies with its environment, while that of a homeotherm is relatively constant Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

39 Balancing Heat Loss and Gain
Organisms exchange heat by four physical processes: conduction, convection, radiation, and evaporation Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

40 Radiation Evaporation Convection Conduction Fig. 40-10
Figure Heat exchange between an organism and its environment Convection Conduction

41 Heat regulation in mammals often involves the integumentary system: skin, hair, and nails
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

42 Hair Epidermis Sweat pore Dermis Muscle Nerve Sweat gland Hypodermis
Fig Hair Epidermis Sweat pore Dermis Muscle Nerve Sweat gland Figure Mammalian integumentary system Hypodermis Adipose tissue Blood vessels Oil gland Hair follicle

43 Five general adaptations help animals thermoregulate:
Insulation Circulatory adaptations Cooling by evaporative heat loss Behavioral responses Adjusting metabolic heat production Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

44 Insulation is a major thermoregulatory adaptation in mammals and birds
Skin, feathers, fur, and blubber reduce heat flow between an animal and its environment Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

45 Circulatory Adaptations
Regulation of blood flow near the body surface significantly affects thermoregulation Many endotherms and some ectotherms can alter the amount of blood flowing between the body core and the skin In vasodilation, blood flow in the skin increases, facilitating heat loss In vasoconstriction, blood flow in the skin decreases, lowering heat loss Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

46 The arrangement of blood vessels in many marine mammals and birds allows for countercurrent exchange
Countercurrent heat exchangers transfer heat between fluids flowing in opposite directions Countercurrent heat exchangers are an important mechanism for reducing heat loss Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

47 Canada goose Bottlenose dolphin Blood flow Artery Vein Vein Artery
Fig Canada goose Bottlenose dolphin Blood flow Artery Vein Vein Artery 35ºC 33º Figure Countercurrent heat exchangers 30º 27º 20º 18º 10º

48 Some bony fishes and sharks also use countercurrent heat exchanges
Many endothermic insects have countercurrent heat exchangers that help maintain a high temperature in the thorax Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

49 Cooling by Evaporative Heat Loss
Many types of animals lose heat through evaporation of water in sweat Panting increases the cooling effect in birds and many mammals Sweating or bathing moistens the skin, helping to cool an animal down Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

50 Behavioral Responses Both endotherms and ectotherms use behavioral responses to control body temperature Some terrestrial invertebrates have postures that minimize or maximize absorption of solar heat Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

51 Fig Figure Thermoregulatory behavior in a dragonfly

52 Adjusting Metabolic Heat Production
Some animals can regulate body temperature by adjusting their rate of metabolic heat production Heat production is increased by muscle activity such as moving or shivering Some ectotherms can also shiver to increase body temperature Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

53 O2 consumption (mL O2/hr) per kg
Fig RESULTS 120 100 80 O2 consumption (mL O2/hr) per kg 60 40 Figure How does a Burmese python generate heat while incubating eggs? 20 5 10 15 20 25 30 35 Contractions per minute

54 Time from onset of warm-up (min)
Fig PREFLIGHT PREFLIGHT WARM-UP FLIGHT 40 Thorax 35 Temperature (ºC) 30 Abdomen Figure Preflight warm-up in the hawkmoth 25 2 4 Time from onset of warm-up (min)

55 Acclimatization in Thermoregulation
Birds and mammals can vary their insulation to acclimatize to seasonal temperature changes When temperatures are subzero, some ectotherms produce “antifreeze” compounds to prevent ice formation in their cells Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

56 Physiological Thermostats and Fever
Thermoregulation is controlled by a region of the brain called the hypothalamus The hypothalamus triggers heat loss or heat generating mechanisms Fever is the result of a change to the set point for a biological thermostat Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

57 Sweat glands secrete sweat, which evaporates, cooling the body.
Fig Sweat glands secrete sweat, which evaporates, cooling the body. Thermostat in hypothalamus activates cooling mechanisms. Blood vessels in skin dilate: capillaries fill; heat radiates from skin. Body temperature decreases; thermostat shuts off cooling mechanisms. Increased body temperature Homeostasis: Internal temperature of 36–38°C Body temperature increases; thermostat shuts off warming mechanisms. Decreased body temperature Figure The thermostatic function of the hypothalamus in human thermoregulation Blood vessels in skin constrict, reducing heat loss. Thermostat in hypothalamus activates warming mechanisms. Skeletal muscles contract; shivering generates heat.

58 Concept 40.4: Energy requirements are related to animal size, activity, and environment
Bioenergetics is the overall flow and transformation of energy in an animal It determines how much food an animal needs and relates to an animal’s size, activity, and environment Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

59 Energy Allocation and Use
Animals harvest chemical energy from food Energy-containing molecules from food are usually used to make ATP, which powers cellular work After the needs of staying alive are met, remaining food molecules can be used in biosynthesis Biosynthesis includes body growth and repair, synthesis of storage material such as fat, and production of gametes Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

60 Organic molecules in food External environment Animal body
Fig Organic molecules in food External environment Animal body Digestion and absorption Heat Energy lost in feces Nutrient molecules in body cells Energy lost in nitrogenous waste Carbon skeletons Cellular respiration Heat Figure Bioenergetics of an animal: an overview ATP Biosynthesis Cellular work Heat Heat

61 Quantifying Energy Use
Metabolic rate is the amount of energy an animal uses in a unit of time One way to measure it is to determine the amount of oxygen consumed or carbon dioxide produced Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

62 Fig Figure Measuring rate of oxygen consumption in a running pronghorn

63 Minimum Metabolic Rate and Thermoregulation
Basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest at a “comfortable” temperature Standard metabolic rate (SMR) is the metabolic rate of an ectotherm at rest at a specific temperature Both rates assume a nongrowing, fasting, and nonstressed animal Ectotherms have much lower metabolic rates than endotherms of a comparable size Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

64 Size and Metabolic Rate
Metabolic rate per gram is inversely related to body size among similar animals Researchers continue to search for the causes of this relationship The higher metabolic rate of smaller animals leads to a higher oxygen delivery rate, breathing rate, heart rate, and greater (relative) blood volume, compared with a larger animal Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

65 Figure 40.19 The relationship of metabolic rate to body size
103 Elephant 102 Horse Human 10 Sheep BMR (L O2/hr) (Iog scale) Cat Dog 1 Rat 10–1 Ground squirrel Shrew Mouse Harvest mouse 10–2 10–3 10–2 10–1 1 10 102 103 Body mass (kg) (log scale) (a) Relationship of BMR to body size 8 Shrew 7 6 Figure The relationship of metabolic rate to body size 5 BMR (L O2/hr) (per kg) 4 3 Harvest mouse 2 Mouse Sheep Rat Human Elephant 1 Cat Dog Ground squirrel Horse 10–3 10–2 10–1 1 10 102 103 Body mass (kg) (log scale) (b) Relationship of BMR per kilogram of body mass to body size

66 Activity and Metabolic Rate
Activity greatly affects metabolic rate for endotherms and ectotherms In general, the maximum metabolic rate an animal can sustain is inversely related to the duration of the activity Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

67 Energy Budgets Different species use energy and materials in food in different ways, depending on their environment Use of energy is partitioned to BMR (or SMR), activity, thermoregulation, growth, and reproduction Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

68 from temperate climate
Fig Endotherms Ectotherm 800,000 Reproduction Basal (standard) metabolism Thermoregulation Growth Activity Annual energy expenditure (kcal/hr) 340,000 8,000 4,000 Figure Energy budgets for four animals 60-kg female human from temperate climate 4-kg male Adélie penguin from Antarctica (brooding) 0.025-kg female deer mouse from temperate North America 4-kg female eastern indigo snake

69 Torpor and Energy Conservation
Torpor is a physiological state in which activity is low and metabolism decreases Torpor enables animals to save energy while avoiding difficult and dangerous conditions Hibernation is long-term torpor that is an adaptation to winter cold and food scarcity Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

70 Metabolic rate (kcal per day)
Fig Additional metabolism that would be necessary to stay active in winter 200 Actual metabolism Metabolic rate (kcal per day) 100 Arousals 35 Body temperature 30 25 20 Temperature (°C) 15 10 Figure Body temperature and metabolism during hibernation in Belding’s ground squirrels 5 Outside temperature –5 Burrow temperature –10 –15 June August October December February April

71 Estivation, or summer torpor, enables animals to survive long periods of high temperatures and scarce water supplies Daily torpor is exhibited by many small mammals and birds and seems adapted to feeding patterns Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

72 Chapter 41 Animal Nutrition

73 Omnivore, Herbivore, or Carnivore?
Fig. 41-1 Omnivore, Herbivore, or Carnivore? Figure 41.1 How does a lean fish help a bear make fat? For the Discovery Video Nutrition, go to Animation and Video Files.

74 Concept 41.1: An animal’s diet must supply chemical energy, organic molecules, and essential nutrients An animal’s diet provides chemical energy, which is converted into ATP and powers processes in the body Animals need a source of organic carbon and organic nitrogen in order to construct organic molecules Essential nutrients are required by cells and must be obtained from dietary sources

75 There are four classes of essential nutrients:
Essential amino acids Essential fatty acids Vitamins Minerals

76 Essential Amino Acids Animals require 20 amino acids and can synthesize about half from molecules in their diet The remaining amino acids, the essential amino acids, must be obtained from food in preassembled form A diet that provides insufficient essential amino acids causes malnutrition called protein deficiency

77 Meat, eggs, and cheese provide all the essential amino acids and are thus “complete” proteins
Most plant proteins are incomplete in amino acid makeup Individuals who eat only plant proteins need to eat specific plant combinations to get all essential amino acids

78 Essential amino acids for adults
Fig. 41-2 Essential amino acids for adults Methionine Beans and other legumes Valine Threonine Phenylalanine Leucine Corn (maize) and other grains Figure 41.2 Essential amino acids from a vegetarian diet Isoleucine Tryptophan Lysine

79 Essential Fatty Acids Animals can synthesize most of the fatty acids they need The essential fatty acids are certain unsaturated fatty acids that must be obtained from the diet Deficiencies in fatty acids are rare

80 Table 41-1

81 Table 41-2

82 Dietary Deficiencies Undernourishment is the result of a diet that consistently supplies less chemical energy than the body requires Malnourishment is the long-term absence from the diet of one or more essential nutrients

83 Fig. 41-5 Figure 41.5 Can diet influence the frequency of birth defects?

84 Concept 41.2: The main stages of food processing are ingestion, digestion, absorption, and elimination Ingestion is the act of eating

85 Humpback whale, a suspension feeder
Fig. 41-6a Baleen Figure 41.6 Four main feeding mechanisms of animals Humpback whale, a suspension feeder

86 Caterpillar Feces Leaf miner caterpillar, a substrate feeder
Fig. 41-6b Leaf miner caterpillar, a substrate feeder Figure 41.6 Four main feeding mechanisms of animals Caterpillar Feces

87 Mosquito, a fluid feeder
Fig. 41-6c Figure 41.6 Four main feeding mechanisms of animals Mosquito, a fluid feeder

88 Rock python, a bulk feeder
Fig. 41-6d Figure 41.6 Four main feeding mechanisms of animals Rock python, a bulk feeder

89 Absorption is uptake of nutrients by body cells
Digestion is the process of breaking food down into molecules small enough to absorb In chemical digestion, the process of enzymatic hydrolysis splits bonds in molecules with the addition of water Absorption is uptake of nutrients by body cells Elimination is the passage of undigested material out of the digestive compartment

90 Nutrient molecules enter body cells Mechanical digestion
Fig. 41-7 Small molecules Pieces of food Chemical digestion (enzymatic hydrolysis) Nutrient molecules enter body cells Mechanical digestion Food Undigested material Figure 41.7 The four stages of food processing 1 Ingestion 2 Digestion 3 Absorption 4 Elimination

91 Fig. 41-8 Tentacles Food Gastrovascular cavity Mouth Animals with simple body plans have a gastrovascular cavity that functions in both digestion and distribution of nutrients Figure 41.8 Digestion in a hydra Epidermis Gastrodermis

92 More complex animals have a digestive tube with two openings, a mouth and an anus
This digestive tube is called a complete digestive tract or an alimentary canal It can have specialized regions that carry out digestion and absorption in a stepwise fashion

93 Figure 41.9 Variation in alimentary canals
Crop Gizzard Esophagus Intestine Pharynx Anus Mouth Typhlosole Lumen of intestine (a) Earthworm Foregut Midgut Hindgut Esophagus Rectum Anus Crop Mouth Gastric cecae Figure 41.9 Variation in alimentary canals (b) Grasshopper Stomach Gizzard Intestine Mouth Esophagus Crop Anus (c) Bird

94 Concept 41.3: Organs specialized for sequential stages of food processing form the mammalian digestive system The mammalian digestive system consists of an alimentary canal and accessory glands that secrete digestive juices through ducts Mammalian accessory glands are the salivary glands, the pancreas, the liver, and the gallbladder

95 Food is pushed along by peristalsis, rhythmic contractions of muscles in the wall of the canal
Valves called sphincters regulate the movement of material between compartments

96 Fig Tongue Sphincter Salivary glands Oral cavity Salivary glands Pharynx Mouth Esophagus Esophagus Liver Sphincter Stomach Gall- bladder Ascending portion of large intestine Stomach Gall- bladder Duodenum of small intestine Pancreas Small intestine Liver Small intestine Small intestine Figure The human digestive system Pancreas Large intestine Large intestine Rectum Rectum Anus Anus Appendix A schematic diagram of the human digestive system Cecum

97 Duodenum of small intestine
Fig a Tongue Sphincter Oral cavity Salivary glands Pharynx Esophagus Sphincter Liver Stomach Ascending portion of large intestine Gall- bladder Duodenum of small intestine Pancreas Figure The human digestive system Small intestine Small intestine Large intestine Rectum Anus Appendix Cecum

98 A schematic diagram of the human digestive system
Fig b Salivary glands Mouth Esophagus Gall- bladder Stomach Small intestine Liver Figure The human digestive system Pancreas Large intestine Rectum Anus A schematic diagram of the human digestive system

99 The Oral Cavity, Pharynx, and Esophagus
The first stage of digestion is mechanical and takes place in the oral cavity Salivary glands deliver saliva to lubricate food Teeth chew food into smaller particles that are exposed to salivary amylase, initiating breakdown of glucose polymers

100 The tongue shapes food into a bolus and provides help with swallowing
The region we call our throat is the pharynx, a junction that opens to both the esophagus and the trachea (windpipe) The trachea leads to the lungs

101 The esophagus conducts food from the pharynx down to the stomach by peristalsis
Swallowing causes the epiglottis to block entry to the trachea, and the bolus is guided by the larynx, the upper part of the respiratory tract Coughing occurs when the swallowing reflex fails and food or liquids reach the windpipe

102 Esophageal sphincter contracted Epiglottis down Glottis
Fig Food Epiglottis up Tongue Epiglottis up Pharynx Esophageal sphincter contracted Epiglottis down Glottis Glottis down and open Esophageal sphincter contracted Larynx Trachea Esophagus Esophageal sphincter relaxed Glottis up and closed Relaxed muscles To lungs To stomach Contracted muscles Relaxed muscles Sphincter relaxed Figure From mouth to stomach: the swallowing reflex and esophageal peristalsis Stomach

103 Digestion in the Stomach
The stomach stores food and secretes gastric juice, which converts a meal to acid chyme

104 Chemical Digestion in the Stomach
Gastric juice is made up of hydrochloric acid and the enzyme pepsin Parietal cells secrete hydrogen and chloride ions separately Chief cells secrete inactive pepsinogen, which is activated to pepsin when mixed with hydrochloric acid in the stomach Mucus protects the stomach lining from gastric juice

105 Figure 41.12 The stomach and its secretions
Esophagus Sphincter Stomach Sphincter 5 µm Small intestine Folds of epithelial tissue Interior surface of stomach Epithelium 3 1 Pepsinogen and HCl are secreted. Pepsinogen Pepsin 2 Gastric gland HCl 2 HCl converts pepsinogen to pepsin. 1 Figure The stomach and its secretions 3 Pepsin activates more pepsinogen. Mucus cells H+ Cl– Chief cells Chief cell Parietal cells Parietal cell

106 Gastric ulcers, lesions in the lining, are caused mainly by the bacterium Helicobacter pylori

107 Digestion in the Small Intestine
The small intestine is the longest section of the alimentary canal It is the major organ of digestion and absorption

108 Figure 41.13 Enzymatic hydrolysis in the human digestive system
Carbohydrate digestion Protein digestion Nucleic acid digestion Fat digestion Oral cavity, pharynx, esophagus Polysaccharides Disaccharides (starch, glycogen) (sucrose, lactose) Salivary amylase Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intes- tine Polysaccharides Polypeptides DNA, RNA Fat globules Pancreatic amylases Pancreatic trypsin and chymotrypsin Pancreatic nucleases Bile salts Maltose and other disaccharides Fat droplets Nucleotides Smaller polypeptides Pancreatic lipase Pancreatic carboxypeptidase Figure Enzymatic hydrolysis in the human digestive system Glycerol, fatty acids, monoglycerides Amino acids Epithelium of small intestine (brush border) Small peptides Nucleotidases Nucleosides Disaccharidases Dipeptidases, carboxypeptidase, and aminopeptidase Nucleosidases and phosphatases Monosaccharides Amino acids Nitrogenous bases, sugars, phosphates

109 The first portion of the small intestine is the duodenum, where acid chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and the small intestine itself

110 Duodenum of small intestine Secretin +
Fig Liver Gallbladder Bile Stomach Secretin and CCK Gastrin + CCK + Pancreas Figure Hormonal control of digestion Duodenum of small intestine Secretin + Key CCK + Stimulation Inhibition +

111 Pancreatic Secretions
The pancreas produces proteases trypsin and chymotrypsin, protein-digesting enzymes that are activated after entering the duodenum Its solution is alkaline and neutralizes the acidic chyme

112 Bile Production by the Liver
In the small intestine, bile aids in digestion and absorption of fats Bile is made in the liver and stored in the gallbladder

113 Secretions of the Small Intestine
The epithelial lining of the duodenum, called the brush border, produces several digestive enzymes Enzymatic digestion is completed as peristalsis moves the chyme and digestive juices along the small intestine Most digestion occurs in the duodenum; the jejunum and ileum function mainly in absorption of nutrients and water

114 Absorption in the Small Intestine
The small intestine has a huge surface area, due to villi and microvilli that are exposed to the intestinal lumen The enormous microvillar surface greatly increases the rate of nutrient absorption

115 Vein carrying blood to hepatic portal vein
Fig Vein carrying blood to hepatic portal vein Microvilli (brush border) at apical (lumenal) surface Lumen Blood capillaries Epithelial cells Basal surface Muscle layers Large circular folds Epithelial cells Villi Lacteal Figure The structure of the small intestine Key Lymph vessel Nutrient absorption Villi Intestinal wall

116 Each villus contains a network of blood vessels and a small lymphatic vessel called a lacteal
After glycerol and fatty acids are absorbed by epithelial cells, they are recombined into fats within these cells These fats are mixed with cholesterol and coated with protein, forming molecules called chylomicrons, which are transported into lacteals

117 Lumen of small intestine Triglycerides Fatty acids Monoglycerides
Fig Lumen of small intestine Triglycerides Fatty acids Monoglycerides Epithelial cell Triglycerides Phospholipids, cholesterol, and proteins Figure Absorption of fats Chylomicron Lacteal

118 Amino acids and sugars pass through the epithelium of the small intestine and enter the bloodstream
Capillaries and veins from the lacteals converge in the hepatic portal vein and deliver blood to the liver and then on to the heart

119 Absorption in the Large Intestine
The colon of the large intestine is connected to the small intestine The cecum aids in the fermentation of plant material and connects where the small and large intestines meet The human cecum has an extension called the appendix, which plays a very minor role in immunity

120 Fig Figure Digital image of a human colon

121 A major function of the colon is to recover water that has entered the alimentary canal
Wastes of the digestive tract, the feces, become more solid as they move through the colon Feces pass through the rectum and exit via the anus

122 The colon houses strains of the bacterium Escherichia coli, some of which produce vitamins
Feces are stored in the rectum until they can be eliminated Two sphincters between the rectum and anus control bowel movements

123 Concept 41.4: Evolutionary adaptations of vertebrate digestive systems correlate with diet
Digestive systems of vertebrates are variations on a common plan However, there are intriguing adaptations, often related to diet

124 Some Dental Adaptations
Dentition, an animal’s assortment of teeth, is one example of structural variation reflecting diet Mammals have varying dentition that is adapted to their usual diet The teeth of poisonous snakes are modified as fangs for injecting venom All snakes can unhinge their jaws to swallow prey whole

125 Incisors Molars Canines Premolars (a) Carnivore (b) Herbivore
Fig Incisors Molars Canines Premolars (a) Carnivore (b) Herbivore Figure Dentition and diet (c) Omnivore

126 Stomach and Intestinal Adaptations
Herbivores generally have longer alimentary canals than carnivores, reflecting the longer time needed to digest vegetation

127 Colon (large intestine)
Fig Small intestine Stomach Small intestine Cecum Figure The alimentary canals of a carnivore (coyote) and herbivore (koala) Colon (large intestine) Carnivore Herbivore

128 Mutualistic Adaptations
Many herbivores have fermentation chambers, where symbiotic microorganisms digest cellulose The most elaborate adaptations for an herbivorous diet have evolved in the animals called ruminants

129 Rumen Reticulum Intestine Esophagus Abomasum Omasum 1 2 4 3 Fig. 41-20
Figure Ruminant digestion 4 Abomasum 3 Omasum

130 Concept 41.5: Homeostatic mechanisms contribute to an animal’s energy balance
Food energy balances the energy from metabolism, activity, and storage

131 Energy Sources and Stores
Nearly all of an animal’s ATP generation is based on oxidation of energy-rich molecules: carbohydrates, proteins, and fats Animals store excess calories primarily as glycogen in the liver and muscles Energy is secondarily stored as adipose, or fat, cells When fewer calories are taken in than are expended, fuel is taken from storage and oxidized

132 Stimulus: Blood glucose level rises after eating.
Fig Stimulus: Blood glucose level rises after eating. Homeostasis: 90 mg glucose/ 100 mL blood Stimulus: Blood glucose level drops below set point. Figure Homeostatic regulation of cellular fuel


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