Chapter 40 Intro to Animal Structure and Function
Anatomy is the study of the biological form of an organism
Physiology is the study of the biological functions an organism performs
Exchange with the Environment
• Size and shape directly affect energy and material exchanges
• Organisms with a sac body plan (two cells thick), facilitates diffusion of materials
• More complex organisms have highly folded internal surfaces for exchanging materials
• Vertebrates- space between cells is filled with interstitial fluid, allows for movement of materials into and
out of cells
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
Tissue Structure and Function
Epithelial Tissue- covers the outside of the body and lines the organs and cavities within the body
• Shape: cuboidal (like dice), columnar (like bricks on end), or squamous (like floor tiles)
• Arrangement: simple (single cell layer), stratified (multiple tiers of cells), or pseudostratified (a single layer
of cells of varying length)
Connective Tissue- mainly binds and supports other tissues
• Collagenous fibers provide strength and flexibility
• Elastic fibers stretch and snap back to their original length
• Reticular fibers join connective tissue to adjacent tissues
 Loose connective tissue binds epithelia to underlying tissues and holds organs in place
 Cartilage is a strong and flexible support material
 Fibrous connective tissue is found in tendons (attach muscles to bones) and ligaments (connect
bones at joints)
 Adipose tissue stores fat for insulation and fuel
 Blood and Bone
Muscle Tissue
– 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
Nervous Tissue- senses stimuli and transmits signals throughout the animal
– Neurons, or nerve cells, that transmit nerve impulses
– Glial cells, or glia, that help nourish, insulate, and replenish neurons
Homeostasis -Organisms use homeostasis to maintain a “steady state” or internal balance regardless of external
environment. Ex: body temperature, blood pH, and glucose concentration
Feedback Loops in Homeostasis
• Negative feedback - buildup of the end product shuts the system off, returns to a normal range
• Positive feedback- the end product accelerates the systems further
Endothermy and Ectothermy
• Endothermic animals generate heat by metabolism; more active; energy expensive
• Ectothermic animals gain heat from external sources; less active; less energy needed
Quantifying Energy Use
• Metabolic rate is the amount of energy an animal uses in a unit of time
• Basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest
• Standard metabolic rate (SMR) is the metabolic rate of an ectotherm at rest
• Ectotherms have much lower metabolic rates than endotherms of a comparable size
Size and Metabolic Rate- Metabolic rate per gram is inversely related to body size among similar animals
• The higher metabolic rate of smaller animals leads to a higher breathing rate and heart rate
Energy Budgets- Use of energy is partitioned to BMR (or SMR), activity, thermoregulation, growth, and
reproduction
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Chapter 41 Animal Nutrition
Essential Nutrients
Essential Amino Acids
• Animals require 20 amino acids and can synthesize about half
• Essential amino acids- must be obtained from food in preassembled form
• “Complete” proteins- provides all the essential amino acids (meat, eggs, and cheese)
• Most plant proteins are incomplete in amino acid makeup
Essential Fatty Acids
• Animals can synthesize most of the fatty acids they need
• The essential fatty acids are certain unsaturated fatty acids
Vitamins
• Vitamins are organic molecules required in the diet in small amounts, 13 essential vitamins
• Two categories: fat-soluble and water-soluble
Minerals
• Minerals are simple inorganic nutrients, usually required in small amounts
Dietary Deficiencies
• Undernourishment- diet with less chemical energy than the body requires
• Use up stored fat and carbohydrates; break down own proteins; lose muscle mass;
suffer protein deficiency in the brain; die or suffer irreversible damage
• Malnourishment- absence from the diet of one or more essential nutrients
• Deformities, disease, and death
The main stages of food processing are ingestion, digestion, absorption, and elimination
Ingestion is the act of eating
Suspension Feeders- sift small food particles from the water
Substrate Feeders- animals that live in or on their food source
Fluid Feeders- suck nutrient-rich fluid from a living host
Bulk Feeders- eat relatively large pieces of food
Digestion is the process of breaking food down into molecules small enough to absorb
• 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
Digestive Compartments
Intracellular Digestion- food is engulfed by endocytosis and digested within food vacuoles
Extracellular Digestion- food particles are broken down outside of cells
• Gastrovascular cavity- functions in both digestion and distribution of nutrients
• Complete digestive tract (alimentary canal)- digestive tube with a mouth and an anus
Organs of the mammalian digestive system
• Peristalsis- rhythmic contractions of muscles to push along food
• Sphincters regulate the movement of material between compartments
The Oral Cavity, Pharynx, and Esophagus
• Oral cavity- mechanical digestion takes place
• Salivary glands deliver saliva to lubricate food
•
Amylase- initiates breakdown of glucose polymers
• The tongue shapes food into a bolus and provides help with swallowing
• Pharynx (throat)- opens to both the esophagus and the trachea (windpipe)
• Esophagus conducts food from the pharynx down to the stomach by peristalsis
• Swallowing causes the epiglottis to block entry to the trachea
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Digestion in the Stomach
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, it is activated to pepsin when mixed with HCl
• Mucus protects the stomach lining from gastric juice
Stomach Dynamics
• Contraction and relaxation of stomach muscle churn the stomach’s contents
Digestion in the Small Intestine
• Major organ of digestion and absorption
• Duodenum (first part of small intestine)- acid chyme from the stomach mixes with digestive
juices from the pancreas, liver, gallbladder, and the small intestine itself
Pancreatic Secretions
• The pancreas produces proteases trypsin and chymotrypsin, protein-digesting enzymes that are
activated after entering the duodenum
• Its solution neutralizes the acidic chyme
Bile Production by the Liver
• Aids in digestion and absorption of fats
• Bile is made in the liver and stored in the gallbladder
Secretions of the Small Intestine
• The epithelial lining of the duodenum produces several digestive enzymes
• Most digestion occurs in the duodenum; the jejunum and ileum function mainly in absorption of
nutrients and water
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
Absorption in the Large Intestine
• Colon of the large intestine is connected to the small intestine
• Cecum aids in the fermentation of plant material and connects where the small and large
intestines meet
• Appendix- an extension off the cecum, which plays a very minor role in immunity
• The colon recover waters that has entered the alimentary canal and houses E. coli strains, some
of which produce vitamins
Dental Adaptations- diet is correlated to teeth shape
• The teeth of poisonous snakes are modified as fangs for injecting venom
Stomach and Intestinal Adaptations- Herbivores have longer alimentary canals than carnivores, they
need more time to digest vegetation
Mutualistic Adaptations- Many herbivores have fermentation chambers, where symbiotic
microorganisms digest cellulose (ruminants)
Energy Sources and Stores
• Animals store excess calories primarily as glycogen in the liver and muscles
• Energy is secondarily stored as adipose, or fat, cells
Overnourishment and Obesity
• Overnourishment causes obesity and contributes to diabetes (type 2), colon and breast cancer,
heart attacks, and strokes
• The problem of maintaining weight partly stems from our evolutionary past, when fat hoarding
was a means of survival
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Chapter 42 Circulation and Gas Exchange
Open and Closed Circulatory Systems
• Open circulatory system- (insects, arthropods, and mollusks) blood bathes the organs
directly. Fluid is called hemolymph.
• Closed circulatory system- blood is confined to vessels and is distinct from the
interstitial fluid
Organization of Vertebrate Circulatory Systems
• Arteries branch into arterioles and carry blood to capillaries
• Networks of capillaries (capillary beds) are the sites of chemical exchange between the
blood and interstitial fluid
• Venules converge into veins and return blood from capillaries to the heart
• Blood enters through an atrium and is pumped out through a ventricle
Single Circulation- blood leaving the heart passes through two capillary beds before returning
• Bony fishes, rays, and sharks have single circulation with a two-chambered heart
Double Circulation- Oxygen-poor and oxygen-rich blood are pumped separately from the right
and left sides of the heart (Amphibian, reptiles, and mammals)
Amphibians
• Frogs and other amphibians have a three-chambered heart: two atria and one ventricle
Reptiles (Except Birds)
• Turtles, snakes, and lizards have a three-chambered heart: two atria and one ventricle
• In alligators, caimans, and other crocodilians a septum divides the ventricle
Mammals and Birds
• Mammals and birds have a four-chambered heart with two atria and two ventricles
Mammalian Circulation
Superior
vena cava
Capillaries of
head and
forelimbs
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Pulmonary
artery
Pulmonary
artery
Capillaries
of right lung
Aorta
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3
Capillaries
of left lung
3
2
4
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Pulmonary
vein
Right atrium
Pulmonary
vein
5
1
Left atrium
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Right ventricle
Left ventricle
Inferior
vena cava
Aorta
8
4
Capillaries of
abdominal organs
and hind limbs
The Mammalian Heart
• Cardiac cycle- the rhythmic cycle of contracting and relaxing
• Systole- the contraction, or pumping, phase
• Diastole- the relaxation, or filling, phase
• Four valves prevent backflow of blood in the heart
• Atrioventricular (AV) valves separate each atrium and ventricle
• Semilunar valves control blood flow to the aorta and the pulmonary artery
Maintaining the Heart’s Rhythmic Beat- recorded as an electrocardiogram (ECG or EKG
• Sinoatrial (SA) node, or pacemaker, sets the rate and timing when cardiac cells contract
• Impulses from the SA node travel to the atrioventricular (AV) node
• At the AV node, the impulses are delayed and then travel to the Purkinje fibers that make the
ventricles contract
Blood Flow Velocity- Blood flow in capillaries is slow for the exchange of materials
Blood Pressure
Changes in Blood Pressure During the Cardiac Cycle
• Systolic pressure- pressure in the arteries during ventricular systole; it is the highest pressure in
the arteries
• Diastolic pressure- pressure in the arteries during diastole; it is lower than systolic pressure
Regulation of Blood Pressure
• Vasoconstriction is the contraction of smooth muscle in arteriole walls; it increases blood
pressure
• Vasodilation is the relaxation of smooth muscles in the arterioles; it causes blood pressure to
fall
Blood Pressure and Gravity
• Blood is moved through veins by smooth muscle contraction, skeletal muscle contraction, and
expansion of the vena cava with inhalation.
• One-way valves in veins prevent backflow of blood
Capillary Function
• The critical exchange of substances between the blood and interstitial fluid takes place across
the thin endothelial walls of the capillaries
Fluid Return by the Lymphatic System
• The lymphatic system returns fluid that leaks out in the capillary beds
• Fluid, called lymph, reenters the circulation directly at the venous end of the capillary bed and
indirectly through the lymphatic system
• The lymphatic system drains into veins in the neck
Blood components function in exchange, transport, and defense
• In invertebrates with open circulation, blood (hemolymph) is not different from interstitial fluid
Blood Composition and Function
Plasma- 90% water, inorganic salts (electrolytes), plasma proteins (influence blood pH, osmotic
pressure, and viscosity also lipid transport, immunity, and blood clotting)
Erythrocytes- red blood cells, transport oxygen with hemoglobin
Leukocytes- white blood cells
Platelets- fragments of cells and function in blood clotting
Blood Clotting
• A cascade of complex reactions converts fibrinogen to fibrin, forming a clot
• A blood clot formed within a blood vessel is called a thrombus and can block blood flow
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Cardiovascular Disease
Arteriosclerosis- hardening of the arteries- can include atherosclerosis
Atherosclerosis- caused by the buildup of plaque deposits within arteries
Heart Attacks- the death of cardiac muscle tissue from blockage of coronary arteries
Stroke- the death of tissue in the brain, from rupture/blockage of arteries in the head
Treatment and Diagnosis of Cardiovascular Disease
• Low-density lipoproteins (LDLs) cause plaque formation; “bad cholesterol”
• High-density lipoproteins (HDLs) reduce the deposition of cholesterol; “good
cholesterol”
• Hypertension, high blood pressure, increases the risk of heart attack and stroke
Gas exchange occurs across specialized respiratory surfaces
• Gas exchange across respiratory surfaces takes place by diffusion
Gills in Aquatic Animals
• Fish gills use a countercurrent exchange system, where blood flows in the opposite
direction to water passing over the gills; blood is always less saturated with O2 than the
water it meets
Tracheal Systems in Insects
• The tracheal system of insects consists of tiny branching tubes that penetrate the body
• The tracheal tubes supply O2 directly to body cells
• The respiratory and circulatory systems are separate
Mammalian Respiratory Systems
• Air inhaled through the nostrils passes through the pharynx via the larynx, trachea,
bronchi, bronchioles, and alveoli, where gas exchange occurs
Control of Breathing in Humans
• The medulla oblongata regulates the rate and depth of breathing in response to pH
changes in the cerebrospinal fluid.
• The pons regulates the tempo
• Sensors in the aorta and carotid arteries (secondary control) monitor O2 and CO2
concentrations in the blood
Coordination of Circulation and Gas Exchange
• In the alveoli, O2 diffuses into the blood and CO2 diffuses into the air
• In tissue capillaries, partial pressure gradients favor diffusion of O2 into the interstitial
fluids and CO2 into the blood
Respiratory Pigments
• Arthropods and many molluscs have hemocyanin with copper as the oxygen-binding
component
• Most vertebrates and some invertebrates use hemoglobin
• A single hemoglobin molecule can carry four molecules of O2
• CO2 produced during cellular respiration lowers blood pH and decreases the affinity
of hemoglobin for O2; this is called the Bohr shift
Carbon Dioxide Transport
• Hemoglobin also helps transport CO2 and assists in buffering
• CO2 from respiring cells diffuses into the blood and is transported either in blood plasma,
bound to hemoglobin, or as bicarbonate ions (HCO3–)
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Chapter 43 The Body’s Defenses (The Immune System)
The immune system recognizes foreign bodies and responds with the production of immune
cells and proteins
Innate Immunity (nonspecific)
• Innate defenses include barrier defenses, phagocytosis, antimicrobial peptides
Barrier Defenses
• Skin and mucous membranes of the respiratory, urinary, and reproductive tracts
• Mucus traps and allows for the removal of microbes
• The low pH of skin and the digestive system prevents growth of microbes
Cellular Innate Defenses
• White blood cells (leukocytes) engulf pathogens in the body
• A white blood cell engulfs a microbe, then fuses with a lysosome to destroy the microbe
• Macrophages are part of the lymphatic system and are found throughout the body
Antimicrobial Proteins
• Attack microbes directly or impede their reproduction
• Interferon proteins provide defense against viruses and helps activate macrophages
Inflammatory Responses
• Following an injury, mast cells release histamine which increases local blood supply and
allow more phagocytes and antimicrobial proteins to enter tissues
• Pus- a fluid rich in white blood cells, dead microbes, and cell debris, accumulates at the
site of inflammation
Natural Killer Cells
• All cells in the body (except red blood cells) have a class 1 MHC (major
histocompatibility) protein on their surface
• Cancerous or infected cells no longer express this protein; natural killer (NK) cells attack
these damaged cells, causing them to lyse
Innate Immune System Evasion by Pathogens
• Some pathogens avoid destruction by modifying their surface to prevent recognition or
by resisting breakdown following phagocytosis
• Example: Tuberculosis (TB), kills more than a million people a year
Acquired immunity (specific), lymphocyte receptors provide pathogen-specific recognition
• Lymphocytes (a type of white blood cell) recognize and respond to antigens, foreign
molecules
• Lymphocytes that mature in the thymus are called T cells, and those that mature in
bone marrow are called B cells
• Lymphocytes have an enhanced response to antigens encountered previously
• B cells and T cells have receptor proteins that are specialized to bind to a specific
antigen
• Cytokines are secreted by macrophages and dendritic cells to recruit and activate
lymphocytes
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Antigen Recognition by Lymphocytes
• A single B cell or T cell has about 100,000 identical antigen receptors
• All antigen receptors on a lymphocyte recognize the same epitope, or antigenic
determinant, on an antigen
• B cells give rise to plasma cells, which secrete proteins called antibodies or
immunoglobulins
The Antigen Receptors of B Cells and T Cells
• B cell receptors bind to specific, intact antigens
• Secreted antibodies (immunoglobulins) are free floating B cell receptors
• T cells can bind to an antigen that is free or on the surface of a pathogen
• T cells bind to antigen fragments presented on a host cell-surface proteins- MHC
molecules
The Role of the MHC
• In infected cells, MHC molecules bind and transport antigen fragments to the cell
surface, a process called antigen presentation
• A nearby T cell can then detect the antigen fragment displayed on the cell’s surface
• Class I MHC molecules- display peptide antigens to cytotoxic T cells
• Class II MHC molecules- located on dendritic cells, macrophages, and B cells. These are
antigen-presenting cells that display antigens to cytotoxic T cells and helper T cells
Lymphocyte Development
Origin of Self-Tolerance
• As lymphocytes mature in bone marrow or the thymus, they are tested for selfreactivity and destroyed if they test positive
Amplifying Lymphocytes by Clonal Selection
• The binding of a lymphocyte to an antigen induces the lymphocyte to divide rapidlyclonal selection
• Two types of clones are produced: short-lived activated effector cells and long-lived
memory cells
Primary vs Secondary immune response
• The first exposure to a specific antigen represents the primary immune response
• During this time, effector B cells called plasma cells are generated, and T cells are
activated to their effector forms
• In the secondary immune response, memory cells facilitate a faster response
Acquired immunity defends against infection of body cells and fluids
• Humoral immune response (extracellular pathogens) involves activation and clonal
selection of B cells, resulting in production of secreted antibodies
• Cell-mediated immune response (intercellular pathogens and cancer) involves
activation and clonal selection of cytotoxic T cells
• Helper T cells aid both responses
Helper T Cells: A Response to Nearly All Antigens
• A surface protein called CD4 binds the class II MHC molecule
• This binding keeps the helper T cell joined to the antigen-presenting cell while activation
occurs.
• Activated helper T cells secrete cytokines that stimulate other lymphocytes
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Cytotoxic T Cells: A Response to Infected Cells
• Cytotoxic T cells are the effector cells in cell-mediated immune response
• Binding to a class I MHC complex on an infected cell activates a cytotoxic T cell and
makes it an active killer
• The activated cytotoxic T cell secretes proteins that destroy the infected target cell
B Cells: A Response to Extracellular Pathogens
• The humoral response is characterized by secretion of antibodies by B cells
• Activation of B cells is aided by cytokines and antigen binding to helper T cells
• Clonal selection of B cells generates antibody-secreting plasma cells, the effector cells of
humoral immunity
5 Antibody Classes
• Polyclonal antibodies are the products of many different clones of B cells following
exposure to a microbial antigen
• Monoclonal antibodies are prepared from a single clone of B cells grown in culture
• IgM, IgG (crosses placenta- gives passive immunity to fetus), IgA (breast milk- passive
immunity to infant), IgE, IgD
The Role of Antibodies in Immunity
• Neutralization- a pathogen can no longer infect a host because it is bound to an
antibody
• Agglutination- clumping of bound antibodies to antigens increase phagocytosis
• Complement system- antibodies and proteins generate a membrane attack to lyse a cell
Active and Passive Immunization
• Active immunity- develops in response to an infection or immunization (vaccination)
• Immunization- a nonpathogenic form or part of a microbe elicits an immune response
to an immunological memory
• Passive immunity provides immediate, short-term protection
• It is conferred naturally when IgG crosses the placenta from mother to fetus or when
IgA passes from mother to infant in breast milk
• It can be conferred artificially by injecting antibodies into a nonimmune person
Immune Rejection
• Cells transferred from one person to another can be attacked by immune defenses
Blood Groups
• Antigens on red blood cells determine whether a person has blood type A (A antigen), B
(B antigen), AB (both A and B antigens), or O (neither antigen)
• Antibodies to nonself blood types exist in the body
• Transfusion with incompatible blood leads to destruction of the transfused cells
Tissue and Organ Transplants
• MHC molecules are different among people
• Differences in MHC molecules stimulate rejection of tissue grafts and organ transplants
• Chances of successful transplantation increase if donor and recipient MHC tissue types
are well matched
• Immunosuppressive drugs facilitate transplantation
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Exaggerated, Self-Directed, and Diminished Immune Responses
Allergies
• Allergies are exaggerated (hypersensitive) responses to antigens called allergens
• Allergies such as hay fever, IgE antibodies produced after first exposure to an allergen
attach to receptors on mast cells
• The next time the allergen enters the body mast cells release histamine leading to
typical allergy symptoms
• An acute allergic response can lead to anaphylactic shock within seconds of allergen
exposure
Autoimmune Diseases
• The immune system loses tolerance for self and turns against certain molecules of the
body
• Examples: systemic lupus erythematosus, rheumatoid arthritis, insulin-dependent
diabetes mellitus, and multiple sclerosis
Exertion, Stress, and the Immune System
• Moderate exercise improves immune system function
• Psychological stress has been shown to disrupt hormonal, nervous, and immune
systems
Immunodeficiency Diseases
• Inborn immunodeficiency results from hereditary or developmental defects that
prevent proper functioning of innate, humoral, and/or cell-mediated defenses
• Acquired immunodeficiency results from exposure to chemical and biological agents
• Acquired immunodeficiency syndrome (AIDS) is caused by a virus
Acquired Immune System Evasion by Pathogens
• Pathogens have evolved mechanisms to attack immune responses
Antigenic Variation
• Pathogens are able to change epitope expression and prevent recognition
• The human influenza virus mutates rapidly, and new flu vaccines must be made each
year
Latency
• Some viruses may remain in a host in an inactive state
• Herpes simplex viruses can be present in a human host without causing symptoms
Attack on the Immune System: HIV
• Human immunodeficiency virus (HIV) infects helper T cells
• The loss of helper T cells impairs both the humoral and cell-mediated immune responses
and leads to AIDS
• HIV uses antigenic variation and latency while integrated into host DNA
Cancer and Immunity
• The frequency of certain cancers increases when the immune response is impaired
• Two suggested explanations are
– Immune system normally suppresses cancerous cells
– Increased inflammation increases the risk of cancer
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Chapter 44 Regulating the Internal Environment
Osmoregulation balances the uptake and loss of water and solutes
• Osmoconformers- isoosmotic with their surroundings do not regulate their osmolarity
• Osmoregulators- control water gain/loss in hyperosmotic or hypoosmotic environment
Marine Animals
• Bony fishes in sea water lose water by osmosis and gain salt by diffusion and from food
• They balance water loss by drinking seawater and excreting salts
Freshwater Animals
• Constantly take in water by osmosis and lose salts by diffusion
• Maintain water balance by excreting large amounts of dilute urine
• Salts lost by diffusion are replaced in foods and by uptake across the gills
Animals That Live in Temporary Waters
• Anhydrobiosis- Some aquatic invertebrates that lose almost all their body water and
survive in a dormant state
Land Animals
• Manage water budgets by drinking and eating moist foods and using metabolic water
Transport Epithelia in Osmoregulation
• Animals regulate the composition of body fluid that bathes their cells
• Transport epithelia are specialized epithelial cells that regulate solute movement
• They are essential components of osmotic regulation and metabolic waste disposal
• They are arranged in complex tubular networks
• An example is in salt glands of marine birds, which remove excess sodium chloride from
the blood
An animal’s nitrogenous wastes reflect its phylogeny and habitat
• Nitrogenous wastes result from the breakdown of proteins and nucleic acids
• Some animals convert toxic ammonia (NH3) to less toxic compounds prior to excretion
Forms of Nitrogenous Wastes
Ammonia- Needs lots of water to excrete. No energy needed.
Urea- The liver converts ammonia to less toxic urea. Excreted from the kidneys. Energy
required.
Uric Acid- Insects, land snails, and reptiles, including birds, excrete uric acid. Lots of energy
needed. Uric acid is insoluble in water and is secreted as a paste with little water loss.
Key functions of most excretory systems:
– Filtration: pressure-filtering of body fluids
– Reabsorption: reclaiming valuable solutes
– Secretion: adding toxins and other solutes from the body fluids to the filtrate
– Excretion: removing the filtrate from the system
Survey of Excretory Systems:
Protonephridia- a network of dead-end tubules connected to external openings (planarian)
Metanephridia- tubules that collect coelomic fluid and produce dilute urine (earthworm)
Malpighian Tubules- remove nitrogenous wastes from hemolymph (insects and arthropods)
Kidneys-the excretory organs of vertebrates
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Structure of the Mammalian Excretory System
• Each kidney is supplied with blood by a renal artery and drained by a renal vein
• Urine exits each kidney through a duct called the ureter
• Both ureters drain into a urinary bladder, and urine is expelled through a urethra
• The kidney has two distinct regions: an outer renal cortex and an inner renal medulla
• The nephron, the functional unit of the kidney, consists of a single long tubule and a ball
of capillaries called the glomerulus
• Bowman’s capsule surrounds and receives filtrate from the glomerulus
Filtration of the Blood
• Blood pressure forces fluid from the blood in the glomerulus into the Bowman’s capsule
• The filtrate contains salts, glucose, amino acids, vitamins, and nitrogenous wastes
Pathway of the Filtrate
• From Bowman’s capsule, the filtrate passes through three regions of the nephron: the
proximal tubule, the loop of Henle, and the distal tubule
• Fluid from nephrons flows into a collecting duct, which lead to the renal pelvis
From Blood Filtrate to Urine
Proximal Tubule- Reabsorption of ions, water, and nutrients takes place
Descending Limb of the Loop of Henle- Reabsorption of water continues through
channels formed by aquaporin proteins. The filtrate becomes increasingly concentrated
Ascending Limb of the Loop of Henle- Salt but not water is able to diffuse from the
tubule into the interstitial fluid. The filtrate becomes increasingly dilute
Distal Tubule- Regulates the K+ and NaCl concentrations of body fluids
Collecting Duct- Carries filtrate through the medulla to the renal pelvis
Adaptations of the Vertebrate Kidney to Diverse Environments
Mammals- Mammals that inhabit dry environments have long loops of Henle, while those in
fresh water have relatively short loops
Birds and Other Reptiles- Birds have shorter loops of Henle but conserve water by excreting
uric acid instead of urea
Freshwater Fishes and Amphibians- Freshwater fishes conserve salt in their distal tubules and
excrete large volumes of dilute urine. Amphibians conserve water on land by reabsorbing water
from the urinary bladder
Marine Bony Fishes- are hypoosmotic compared to their environment and excrete very little
urine
Antidiuretic Hormone (ADH)- Increases water reabsorption in the distal tubules and collecting ducts of
the kidney. Helps to conserve water. Alcohol is a diuretic as it inhibits the release of ADH
The Renin-Angiotensin-Aldosterone System (RAAS)
• A drop in blood pressure near the glomerulus causes the juxtaglomerular apparatus (JGA) to
release the enzyme rennin. Renin triggers the formation of the peptide angiotensin II.
Angiotensin II Raises blood pressure and decreases blood flow to the kidneys. Stimulates the
release of the hormone aldosterone, which increases blood volume and pressure
ADH and RAAS both increase water reabsorption, but only RAAS will respond to a decrease in blood
volume
Atrial natriuretic factor (ANF), opposes the RAAS. ANP is released in response to an increase in blood
volume and pressure and inhibits the release of renin
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Chapter 45 Chemical Signals in Animals
Hormones- chemical signals that are secreted into the circulatory system and communicate regulatory
messages within the body
Endocrine system- secretes hormones that coordinate slower but longer-acting responses including
reproduction, development, energy metabolism, growth, and behavior
Nervous system conveys high-speed electrical signals along specialized cells called neurons; these
signals regulate other cells
Types of Secreted Signaling Molecules
Hormones- secreted into extracellular fluids and travel via the bloodstream
Mediate responses to environmental stimuli and regulate growth, development, and
reproduction
Local Regulators- chemical signals that travel over short distances by diffusion
Help regulate blood pressure, nervous system function, and reproduction
Neurotransmitters- diffuse short distances between nerve synapses
Play a role in sensation, memory, cognition, and movement
Neurohormones- originate from neurons in the brain and diffuse through the bloodstream
Pheromones- chemical signals that are used to communicate with other individuals
Mark trails to food sources, warn of predators, and attract potential mates
Three major classes of molecules function as hormones in vertebrates:
– Polypeptides (proteins and peptides)
– Amines derived from amino acids
– Steroid hormones
• Lipid-soluble hormones (steroid hormones) pass easily through cell membranes, while watersoluble hormones (polypeptides and amines) do not
Pathway for Water-Soluble Hormones
• Binding of a hormone to its receptor initiates a signal transduction pathway leading to 1)
responses in the cytoplasm, 2) enzyme activation, or 3) a change in gene expression
Pathway for Lipid-Soluble Hormones
• The response to a lipid-soluble hormone is usually a change in gene expression
Multiple Effects of Hormones- The same hormone may have different effects on target cells
Insulin and Glucagon: Control of Blood Glucose
• Pancreas- has endocrine cells called islets of Langerhans
• alpha cells produce glucagon and beta cells produce insulin
• Insulin reduces blood glucose levels by
– Promoting the cellular uptake of glucose
– Slowing glycogen breakdown in the liver
– Promoting fat storage
• Glucagon increases blood glucose levels by
– Stimulating conversion of glycogen to glucose in the liver
– Stimulating breakdown of fat and protein into glucose
Diabetes Mellitus
• Type I diabetes mellitus (insulin-dependent) is an autoimmune disorder in which the immune
system destroys pancreatic beta cells
• Type II diabetes mellitus (non-insulin-dependent) involves insulin deficiency or reduced
response of target cells due to change in insulin receptors
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Coordination of Endocrine and Nervous Systems in Vertebrates
• Hypothalamus- receives information from the nervous system and initiates responses through
the endocrine system
• Pituitary gland- attached to the hypothalamus
• Posterior pituitary- stores and secretes hormones made in the hypothalamus
Oxytocin induces uterine contractions and the release of milk (pos. feedback)
Antidiuretic hormone (ADH) enhances water reabsorption in the kidneys
• Anterior pituitary makes and releases hormones under regulation of the hypothalamus.
• Ex: production of TRH in the hypothalamus stimulates secretion of TSH
Tropic Hormones- regulates the function of endocrine cells or glands
Thyroid-stimulating hormone (TSH), Follicle-stimulating hormone (FSH), Luteinizing hormone
(LH), Adrenocorticotropic hormone (ACTH)
Nontropic Hormones- target nonendocrine tissues
– Prolactin (PRL)- stimulates lactation in mammals
– Melanocyte-stimulating hormone (MSH)- skin pigmentation and fat metabolism
Growth Hormone- secreted by the anterior pituitary gland, has tropic and nontropic actions
• An excess of GH can cause gigantism, while a lack of GH can cause dwarfism
Thyroid Hormone: Control of Metabolism and Development
• Stimulate metabolism and influence development and maturation
• Hyperthyroidism- high body temp., weight loss, irritability, and high blood pressure
• Graves’ disease is a form of hyperthyroidism in humans
• Hypothyroidism- weight gain, lethargy, and intolerance to cold
• Proper thyroid function requires dietary iodine for hormone production
Parathyroid Hormone and Vitamin D: Control of Blood Calcium
• Parathyroid hormone (PTH) increases the level of blood Ca2+
– It releases Ca2+ from bone and stimulates reabsorption of Ca2+ in the kidneys
– Stimulates kidneys to activate vitamin D-promotes uptake of Ca2+ from food
• Calcitonin decreases the level of blood Ca2+
– It stimulates Ca2+ deposition in bones and secretion by kidneys
Adrenal Hormones: Response to Stress
Adrenal Medulla- Catecholamines
• Secretes epinephrine (adrenaline) and norepinephrine (noradrenaline)
• They mediate various fight-or-flight responses
• Trigger the release of glucose and fatty acids into the blood
• Increase oxygen delivery to body cells
• Direct blood toward heart, brain, and skeletal muscles, and away from skin, digestive
system, and kidneys
Adrenal Cortex- Steroid Hormones
• Glucocorticoids, such as cortisol, influence glucose metabolism and the immune system
• Mineralocorticoids, such as aldosterone, affect salt and water balance
Gonadal Sex Hormones (testes and ovaries)
• All three sex hormones are found in both males and females, but in different amounts
• Testes- synthesize androgens (ex: testosterone)- male reproductive system
• Testosterone causes an increase in muscle and bone mass
• Estrogens (ex: estradiol)- female reproductive system and secondary sex characteristics
• Progestins (ex: progesterone)- preparing and maintaining the uterus
Melatonin and Biorhythms
• Pineal gland- located in the brain, secretes melatonin, controlled by light/dark cycles
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