Transcript Intro Bio Chapter 22-23-24 Fall 2015

Chapter 22
Nutrition and Digestion
PowerPoint® Lectures for
Campbell Essential Biology, Fifth Edition, and
Campbell Essential Biology with Physiology,
Fourth Edition
– Eric J. Simon, Jean L. Dickey, and Jane B. Reece
Lectures by Edward J. Zalisko
© 2013 Pearson Education, Inc.
Biology and Society:
The “Secret” to Shedding Pounds
• About 50 million Americans go on a diet each
year.
– Weight loss is a growing industry.
– Yet only about 5% of dieters are able to reach
their goal weight and maintain it for the long term.
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Biology and Society:
The “Secret” to Shedding Pounds
• There really is no trick to managing your weight.
– Add up the calories from the food you eat.
– Subtract the calories that your body burns.
– If you take in more than you burn, you will gain
weight.
– If you burn more than you take in, you will lose
weight.
OVERVIEW OF ANIMAL NUTRITION
• Food provides the raw materials that animals,
including people, need to
– build tissue and
– fuel cellular work.
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Animal Diets
• Herbivores mainly feed on plants or algae.
• Carnivores mainly eat other animals.
• Omnivores eat
– animals and
– plants or algae.
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Figure 22.1
Herbivore
(mainly eats plants
or algae)
ANIMAL DIETS
Carnivore
(mainly eats animals)
Omnivore
(regularly eats animals as
well as plants or algae)
The Four Stages of Food Processing
• Ingestion is another word for eating.
• Digestion is the breakdown of food into molecules
small enough for the body to absorb.
• Absorption is the uptake of the small nutrient
molecules by cells lining the digestive tract.
• Elimination is the disposal of undigested materials
left over from food.
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Digestion: A Closer Look
• Mechanical digestion
– begins the process and
– involves physical processes like chewing.
• Chemical digestion is the chemical breakdown of
food by digestive enzymes.
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Figure 22.2
Cheese protein
(a polymer of
amino acids in
a specific sequence)
1 Breakdown of protein
by human digestive
system
Amino acid
monomer
Amino acids
2 Absorption of amino acids by cells lining the
small intestine; transport via bloodstream to
other cells
Human protein
3 Cells use amino acids
from the cheese and
other foods to produce
new human proteins
Digestive Compartments
• How do animals digest their food without digesting
themselves?
• In animals, chemical digestion is contained safely
within some kind of compartment.
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Digestive Compartments
• As a cell engulfs food by phagocytosis,
– a food vacuole forms,
– which then fuses with a lysosome filled with
digestive enzymes, and
– as food is digested, small food molecules pass
through the vacuole membrane into the cytoplasm,
which nourishes the cell.
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Digestive Compartments
• Food vacuoles are the simplest of all digestive
compartments.
• Sponges are the only animals that digest food
solely within their cells.
• Gastrovascular cavities
– are digestive compartments surrounded by cells
and
– have only a single opening.
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Digestive Compartments
• A digestive tube, or alimentary canal, has two
separate openings:
– a mouth and
– an anus.
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Figure 22.5
ACCESSORY ORGANS
ALIMENTARY CANAL
Oral cavity (mouth)
Tongue
Pharynx
Salivary glands
Esophagus
Liver
Gallbladder
Pancreas
Stomach
Small intestine
Colon of large intestine
Appendix
Rectum
Anus
The Mouth
• The mouth, or oral cavity, functions in
– ingestion and
– the preliminary steps of digestion.
• Chemical digestion begins in the mouth with the
secretion of saliva from salivary glands.
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Figure 22.6
Incisors
Canine
Premolars
Teeth
Molars
“Wisdom”
tooth
Tongue
Opening of a
salivary gland duct
The Pharynx
• The pharynx
– connects the mouth to the esophagus and
– opens to the trachea, which leads to the lungs.
• During swallowing, a reflex
– moves the opening of the trachea upward and
– tips the epiglottis to close the trachea entrance.
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Figure 22.7
BREATHING
SWALLOWING
Epiglottis
up
Adam’s
apple
Pharynx
Air flowing
into open
trachea
(windpipe)
Epiglottis
down
Esophagus
closed
Trachea
closed
Food flowing
into open
esophagus
The Esophagus
• The esophagus
– is a muscular tube,
– connects the pharynx to the stomach, and
– moves food down by peristalsis, alternating
waves of muscular contraction and relaxation.
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Figure 22.8
Esophageal sphincter
(contracted)
Food ball
Relaxed muscles
Contracted muscles
Relaxed muscles
Stomach
The Stomach
• The stomach
– can store food for several hours and
– churns food into a thick soup called chyme.
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The Stomach
• Fluid in the stomach contains gastric juice,
made of
– strong acid,
– digestive enzymes,
– mucus, and
– the enzyme pepsin, which digests proteins.
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Figure 22.9
Esophagus
Stomach lining secretes
gastric juice (acid, enzyme
molecules, and mucus)
Sphincters control
the flow into and
out of the stomach
Accordion-like
folds allow the
stomach to expand.
Small intestine
Food particle
Stomach Ailments
• Heartburn is caused by backflow of chyme into the
esophagus.
• Gastric ulcers are
– erosions of the stomach lining and
– often caused by the bacterium Helicobacter pylori.
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The Small Intestine
• The small intestine is
– the longest part of the alimentary canal and
– the major organ for chemical digestion and
absorption of nutrients into the bloodstream.
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Chemical Digestion in the Small Intestine
• Most chemical digestion occurs in the duodenum,
the first part of the small intestine.
• In the duodenum, chyme from the stomach mixes
with
– pancreatic juice,
– bile, and
– a digestive juice secreted by the intestinal lining.
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Figure 22.11
Bile
Liver
Stomach
Bile
Gallbladder
Intestinal enzymes
Chyme
Pancreatic juice
Duodenum of
small intestine
Pancreas
Chemical Digestion in the Small Intestine
• The pancreas secretes juice that
– neutralizes stomach acids in the duodenum and
– aids in digestion.
• The liver secretes bile, which
– is stored in the gallbladder and
– helps digest fats.
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Absorption of Nutrients
• In the duodenum, nutrients are
– completely digested and
– ready to be absorbed.
• Nutrients only enter the body if they are absorbed
into the walls of the digestive tract.
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Absorption of Nutrients
• Villi and microvilli on the surface of the small
intestine increase
– the surface area and
– capacity for absorption.
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Figure 22.13
Blood vessels
Muscle
layers
Intestinal wall
Villi
Interior of
intestine
Nutrient
absorption
Interior of
intestine
Nutrient
absorption
Nutrient
absorption
Microvilli
Epithelial
cells
Blood
capillaries
Epithelial cells and
blood capillary
Blood
Lymphatic
vessel
Villi
The Large Intestine
• The large intestine is
– shorter, but wider, than the small intestine and
– about 1.5 meters in length.
• At the junction of the small and large intestine is a
small, finger-like extension called the appendix.
– The appendix contains white blood cells that make
minor contributions to the immune system.
– Appendicitis is a bacterial infection of the
appendix.
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The Large Intestine
• The colon
– forms the main portion of the large intestine,
– absorbs water from the alimentary canal, and
– produces feces, the waste product of food.
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The Large Intestine
• The rectum
– forms the last 15 cm (6 inches) of the large
intestine and
– stores feces until elimination.
• The anus
– consists of two sphincters and
– regulates the opening of the rectum.
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Figure 22.14
Colon of
large
intestine
Small
intestine
Sphincter
End
of small
intestine
Nutrient
flow
Appendix
Rectum
Anus
The Large Intestine
• Food processing takes place along the alimentary
canal.
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HUMAN NUTRITIONAL REQUIREMENTS
• Proper nutrition provides
– fuel for cellular work,
– materials for building molecules, and
– essential nutrients for health.
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Food as Fuel
• Cells use cellular respiration to
– extract energy stored in food molecules and
– generate molecules of ATP to do work.
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Figure 22.16
“Fuel”
(organic molecules
such as glucose)
C6H12O6
O2
Mitochondrion
Cellular
respiration
ATP
Cell
“Exhaust”
CO2 and H2O
(energy for
cellular work)
Calories
• Calories are a measure of the energy
– stored in your food and
– used in daily activities.
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Table 22.1
Decoding Food Labels
• On food labels, the FDA requires
– the list of ingredients and
– key nutrition facts.
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Figure 22.18
Figure 22.UN02
Herbivores eat plants
and/or algae
O2
Omnivores
eat both
Carnivores eat animals
Figure 22.UN03
Inside
body
2 Digestion
1 Ingestion
Food
Food
in mouth
Mechanical
digestion
Chemical
digestion
via enzymes
3 Absorption
Small
molecules
4 Elimination
Undigested
materials
Figure 22.UN04
Alimentary
canal
Accessory
organs
Mouth
(oral cavity)
Salivary glands
Digestion
Absorption
Mechanical
Chemical
Chewing
Salivary
amylase
Churning
Acid and
pepsin (in
gastric juice)
Pharynx and
esophagus
Stomach
Small
intestine
Large
intestine
Anus
Liver,
gallbladder,
pancreas
Other
enzymes
Nutrients
and water
Water
Chapter 23
Circulation and Respiration
Biology and Society:
Avoiding “The Wall”
• Properly functioning circulatory and respiratory
systems are essential to all of us.
• The two systems are such close partners that they
are explored together in this chapter.
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UNIFYING CONCEPTS OF ANIMAL
CIRCULATION
• Every organism must exchange materials with its
environment, relying upon
– diffusion, the spontaneous movement of
molecules from an area of higher concentration to
an area of lower concentration, and
– a circulatory system, which facilitates the
exchange of materials for all but the simplest
animals.
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Open and Closed Circulatory Systems
• Circulatory systems typically consist of a
– central pump,
– vascular system, and
– circulating fluid.
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Open and Closed Circulatory Systems
• In an open circulatory system,
– the heart pumps blood into large open-ended
vessels and
– fluid circulates freely among cells.
• Open circulatory systems are found in many
invertebrates, including
– arthropods and
– most molluscs.
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Open and Closed Circulatory Systems
• In a closed circulatory system, blood
– stays within a set of tubes and
– is distinct from the interstitial fluid, the fluid that
fills the spaces around cells.
• Closed circulatory systems are found in
– many invertebrates, including earthworms and
octopuses, and
– vertebrates.
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Figure 23.1
Vessels
Interstitial fluid
Vessels
Capillaries
Heart
Heart
Circulating fluid
Arteriole Capillaries
Tubular
heart
Artery
(O2-rich
blood)
Venule
Vein
Vessels
(a) Open circulatory system
Atrium
Ventricle
Artery
(O2-poor blood)
(b) Closed circulatory system
Heart
Open and Closed Circulatory Systems
• The cardiovascular system of vertebrates
consists of the
– heart and
– blood vessels.
• In the heart,
– the atrium receives blood and
– the ventricle pumps blood away from the heart.
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Open and Closed Circulatory Systems
• Blood is confined to three main types of blood
vessels:
1. Arteries carry blood away from the heart into
smaller arterioles as they approach the organs.
2. Capillaries are the site of exchange between
blood and interstitial fluid.
3. Venules collect blood from the capillaries and
converge to form veins, which return blood back
to the heart.
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THE HUMAN CARDIOVASCULAR SYSTEM
• In the human cardiovascular system,
– the central pump is the heart,
– the vascular system is the blood vessels, and
– the circulating fluid is the blood.
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The Path of Blood
• Humans and other terrestrial vertebrates have a
double circulation system consisting of
– a pulmonary circuit between the heart and lungs
and
– a systemic circuit between the heart and the rest
of the body.
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Figure 23.2
CO2
O2
CO2
CO2
Lung
Lung
O2
O2
Heart
O2-rich blood
O2
O2-poor blood
CO2
(a) Pulmonary circuit
(b) Systemic circuit
The Path of Blood
• One complete trip through the human
cardiovascular system
– takes about one minute and
– requires two passes through the heart.
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How the Heart Works
• The human heart
– is a muscular organ about the size of a fist,
– is located under the breastbone, and
– has four chambers.
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How the Heart Works
• The path of blood flow through the human heart
functions as two pumps moving blood between
– the heart and lungs and
– the heart and the rest of the body.
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Figure 23.4
To body
O2-rich blood
O2-poor blood
From
body
Right
lung
Left
lung
Right atrium
Left atrium
Valves
Valves
Right
ventricle
From body
Left
ventricle
Blood Vessels
• If the heart is the body’s “pump,” then the
“plumbing” is the system of arteries, veins, and
capillaries.
– Arteries carry blood away from the heart.
– Veins carry blood toward the heart.
– Capillaries allow for exchange between the
bloodstream and tissue cells.
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Blood Vessels
• All blood vessels are lined by a thin layer of tightly
packed epithelial cells.
• Structural differences in the walls of the different
kinds of blood vessels correlate with their different
functions.
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Figure 23.7
From heart
To heart
Epithelium
Valve
Epithelium
Epithelium
Smooth
muscle
Smooth
muscle
Connective
tissue
Connective
tissue
Artery
Venule
Arteriole
Capillary
Vein
Blood Flow through Arteries
• The force that blood exerts against the walls of
blood vessels is blood pressure.
– Blood pressure pushes blood from the heart to the
capillary beds.
– A pulse is the rhythmic stretching of the arteries
caused by the pressure of blood forced into the
arteries during systole.
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Blood Flow through Arteries
• Optimal blood pressure for adults is
– below 120 systolic and
– below 80 diastolic.
• High blood pressure, or hypertension, is
persistent
– systolic blood pressure higher than 140 and/or
– diastolic blood pressure higher than 90.
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Blood Flow through Capillary Beds
• The walls of capillaries are thin and leaky.
– At the arterial end of the capillary, blood pressure
pushes fluid rich in oxygen, nutrients, and other
substances into the interstitial fluid.
– At the venous end of the capillary, CO2 and other
wastes diffuse from tissue cells into the interstitial
fluid, and then into the capillary bloodstream.
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Figure 23.8
Tissue cell
Capillary
Red blood cell
Diffusion
of O2 and
nutrients out
of capillary
and into
tissue cells
Diffusion
of CO2 and
wastes out
of tissue
cells and
into capillary
To vein
LM
Interstitial fluid
(a) Capillaries
(b) Chemical exchange
Blood Return through Veins
• Blood returns to the heart
– after chemicals are exchanged between the blood
and body cells and
– at a pressure that has nearly dropped to zero.
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Blood Return through Veins
• Blood moves back toward the heart because of
– surrounding skeletal muscles that compress the
veins and
– one-way valves that permit blood flow only toward
the heart.
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Figure 23.9
To heart
Valve (open)
Skeletal muscle
Valve (closed)
Figure 23.10
Plasma
(55%)
Water (90%
of plasma)
Cellular
elements (45%)
Red blood cells
(erythrocytes)
Proteins
Dissolved salts
(such as sodium,
potassium, calcium)
Substances being
transported (such
as O2, CO2, nutrients,
wastes, hormones)
White blood cells
(leukocytes)
Blood
Platelets
Blood
• Suspended in plasma are three types of cellular
elements:
1. red blood cells,
2. white blood cells, and
3. platelets.
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Red Blood Cells and Oxygen Transport
• Red blood cells (erythrocytes)
– are the most numerous type of blood cell and
– are shaped like discs with indentations in the
middle.
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Figure 23.12
CELLULAR COMPONENTS OF BLOOD
White Blood Cells
(cells that fight infection)
Colorized SEM
Platelets
(bits of membrane-enclosed
cytoplasm that aid clotting)
Colorized SEM
Red Blood Cells
(cells that carry oxygen)
Colorized SEM
Colorized SEM
Colorized SEM
Fibrin
Red blood cell
Red Blood Cells and Oxygen Transport
• Carbohydrate-containing molecules on the surface
of red blood cells determine the blood type.
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Figure 9.20
Blood
Group
(Phenotype) Genotypes
Red Blood Cells
Carbohydrate
A
Antibodies
Present in
Blood
A
IAIA
or
IAi
B
IBIB
or
IBi
AB
IAIB
—
O
ii
Anti-A
Anti-B
Carbohydrate
B
Anti-B
Anti-A
Reactions When Blood from Groups Below
Is Mixed with Antibodies from Groups at Left
A
O
B
AB
Red Blood Cells and Oxygen Transport
• Each red blood cell contains approximately 250
million molecules of hemoglobin, which
– contains iron and
– transports oxygen throughout the body.
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White Blood Cells and Defense
• White blood cells (leukocytes)
– fight infections,
– are larger than red blood cells,
– lack hemoglobin, and
– are much less abundant than red blood cells
(about 700 times fewer).
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Figure 23.12b
Colorized SEM
White Blood Cells
(cells that fight infection)
Platelets and Blood Clotting
• Blood contains two components that aid in
clotting:
1. platelets, bits of cytoplasm pinched off from
larger cells in the bone marrow, and
2. clotting factors released from platelets that
convert fibrinogen, a protein found in
plasma, into a threadlike protein called fibrin.
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Figure 23.12c
Colorized SEM
Platelets
(bits of membrane-enclosed
cytoplasm that aid clotting)
Colorized SEM
Fibrin
Red blood cell
Platelets and Blood Clotting
• In the inherited disease hemophilia, excessive and
sometimes fatal bleeding can occur from even
minor cuts and bruises.
• Hemophilia is caused by a genetic mutation in one
of several genes that code for clotting factors.
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Stem Cells and the Treatment of Leukemia
• Leukemia
– is cancer of white blood cells and
– may require treatment using
– radiation,
– chemotherapy, and/or
– bone marrow transplantation.
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Cardiovascular Disease
• The cardiovascular system contributes to
homeostasis by
– exchanging nutrients and wastes with the
interstitial fluid,
– controlling the composition of blood by moving it
through the lungs, liver, and kidneys,
– helping to regulate temperature by moving blood
to or away from the skin,
– distributing hormones, and
– defending against foreign invaders.
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Cardiovascular Disease
• Cardiovascular disease
– includes all diseases affecting the heart and blood
vessels,
– accounts for 40% of all deaths in the United
States, and
– kills more than 1 million people each year.
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Cardiovascular Disease
• Atherosclerosis
– is a chronic cardiovascular disease and
– results from fatty deposits called plaque that
develop in the inner walls of arteries, clogging the
passages through which blood can flow.
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Figure 23.14
Passageway
for blood
Connective
tissue
Smooth
tissue
Partially blocked
passageway
Plaque
Epithelium
Normal artery
Artery partially blocked by plaque
UNIFYING CONCEPTS OF ANIMAL
RESPIRATION
• Cellular respiration
– uses oxygen and glucose and
– produces water, carbon dioxide, and energy in the
form of ATP.
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UNIFYING CONCEPTS OF ANIMAL
RESPIRATION
• Cells using cellular respiration
– need a steady supply of oxygen and
– must continuously dispose of CO2.
• The respiratory system promotes this gas
exchange.
Figure 23.UN01
CO2
O2
Environment
Cell
C6H12O6
Glucose
6 O2
Oxygen
Cellular
respiration
6 CO2
6 H2O
ATP
Carbon
dioxide
Water
Energy
The Structure and Function of Respiratory Surfaces
• Gas exchange occurs at the respiratory surface,
which must be
– large enough to take up oxygen for every cell in
the body and
– adapted to the lifestyle of the organism.
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Figure 23.17
RESPIRATORY ORGANS
Skin
(entire body
surface)
Gills
(extensions of the
body surface)
Tracheae
(branching
internal tubes)
Lungs
(localized
internal organs)
Gills
Tracheae
(internal
tubes)
Moist skin of a leech Gills of a sea slug
Tracheae of a silk
moth caterpillar
Model of a pair of
human lungs
THE HUMAN RESPIRATORY SYSTEM
• The human respiratory system has three phases
of gas exchange:
1. breathing, the ventilation of the lungs by alternate
inhalation and exhalation,
2. transport of oxygen from the lungs to the rest of
the body via the circulatory system, and
3. diffusion of oxygen from the blood and release of
CO2 into the blood by cells of the body.
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Figure 23.18-3
O2 1 Breathing
CO2
Lung
2 Transport of gases by
the circulatory system
Circulatory system
3 Exchange of gases
with body cells
Mitochondria
O2
CO2
Capillary
Cell
The Structure and Function of the Human
Respiratory System
• Air moves sequentially from the mouth and
nose to
– the pharynx, where digestive and respiratory
systems meet,
– the larynx (voice box) and trachea (windpipe),
– the bronchi (one bronchus to each lung),
– the bronchioles, the smallest branches of the
tubes within the lungs, and
– the alveoli, the air sacs where gas exchange
primarily occurs.
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Figure 23.19
Pharynx
Nasal cavity
Esophagus
Larynx (voice box)
Left lung
Trachea (windpipe)
Right lung
Bronchus
To
heart
O2-rich
blood
From
heart
O2-poor
blood
Bronchiole
Bronchiole
O2
Diaphragm
Heart
(a) Overview of the human respiratory system
CO2
Alveoli
Blood
capillaries
(b) The structure of alveoli
The Structure and Function of the Human
Respiratory System
• Muscles in the voice box can stretch vocal cords
within the larynx.
• During exhalation, outgoing air can produce vocal
sounds as air passes by the stretched vocal cords.
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Taking a Breath
• Breathing is the alternating process of
– inhalation and
– exhalation.
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Figure 23.20
Rib cage
expands as
rib muscles
contract
Air
inhaled
Rib cage gets
smaller as
rib muscles
relax
Air
exhaled
Lung
Diaphragm
contracts
(moves
down)
Inhalation
(Air pressure is higher in
atmosphere than in lungs.)
Diaphragm
relaxes
(moves up)
Exhalation
(Air pressure is lower in
atmosphere than in lungs.)
The Role of Hemoglobin in Gas Transport
• The human respiratory system
– takes in O2,
– expels CO2, but
– relies on the circulatory system to shuttle these
gases between the lungs and the body’s cells.
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Figure 23.22
O2 in
inhaled air
CO2 in
exhaled air
Air spaces
Alveolus
CO2
O2
Capillaries
of lung
O2-rich,
CO2-poor
blood
CO2-rich,
O2-poor
blood
Heart
Tissue
capillaries
CO2
Interstitial
fluid
O2
Tissue cells throughout body
Figure 23.24
(a) Healthy lung (nonsmoker)
(b) Cancerous lung (smoker)
Figure 23.UN02
CO2
Pulmonary
arteries
O2
Capillaries
Pulmonary circuit
Pulmonary
veins
Heart
Venae
cavae
Veins
Aorta
Systemic circuit
Venules
O2-rich blood
O2-poor blood
Arteries
Arterioles
Capillaries
Figure 23.UN04
Capillary
Epithelium
Valve
Smooth
muscle
Connective
tissue
Artery
Vein
Figure 23.UN05
CELLULAR COMPONENTS OF BLOOD
Red Blood Cells
(transport oxygen)
White Blood Cells
(fight infections)
Platelets
(allow for blood clotting)
Chapter 24
The Body’s Defenses
Biology and Society:
The Elusive Search for an AIDS Vaccine
• A vaccine is a harmless version or piece of a
disease-causing microbe.
• Vaccinations against HIV, the virus that causes
AIDS, have not been successful.
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INNATE DEFENSES
• The immune system is the body’s defense
against infectious disease.
• Our bodies defend us against pathogens,
disease-causing
– viruses and
– microorganisms.
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INNATE DEFENSES
• The human body contains two lines of defense:
1. external barriers and
2. internal defenses.
• Both are innate defenses, fully ready to respond
before an invader has been encountered.
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INNATE DEFENSES
• Adaptive defenses are
– a third line of defense
– activated by exposure to specific invaders.
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Figure 24.1
THE BODY’S DEFENSES
Innate Defenses
(always deployed)
Internal innate defenses
• Skin
• Secretions
• Mucous membranes
• Phagocytic cells
Cilia
Mucusproducing
cells
Colorized SEM
External innate defenses
Adaptive Defenses
(activated by exposure
to specific pathogens)
• Lymphocytes
Invading
microbe
Phagocytic
cell
• Natural killer cells
• Defensive proteins
• Inflammatory response
B cell
T cell
• Antibodies
The Lymphatic System
(involved in internal innate defenses and adaptive
defenses)
Lymph
node
External Innate Defenses
• The body has physical barriers including
– a tough outer skin layer generally impenetrable to
viruses and bacteria,
– mucous membranes covered with sticky mucus,
– wax in the ear canal, which traps particles before
they can get deep inside,
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External Innate Defenses
– secretions (such as tears, sweat, and saliva) with
antimicrobial chemicals, and
– strong stomach acids that kill most pathogens
ingested with food.
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Internal Innate Defenses
• To fight pathogens within the body, an animal’s
immune system must
– detect foreign particles and cells and
– distinguish nonself from self.
• This second line of defense includes
– white blood cells and
– defensive proteins.
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Figure 24.2
INTERNAL INNATE DEFENSES
White Blood Cells
Phagocytic cells
(engulf foreign cells
or substances)
Natural killer cells
(destroy infected and
cancerous body cells)
Defensive Proteins
Interferon
(protect body cells
against viral infection)
Complement proteins
(cause invading
microbial cells to lyse)
The Inflammatory Response
• Another example of an internal innate defense is
the inflammatory response, a coordinated set of
nonspecific defenses in response to injury or
infection.
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Figure 24.4
Skin surface
Blood
clot
Swelling
Splinter
Bacteria
Phagocytic
cells
Phagocytic
cells and
fluid move into
area
Chemical
signals
White blood cell
Blood vessel
1
Tissue injury; release of
chemical signals such as
histamine
2
Dilation and increased
leakiness of local blood
vessels; migration of
phagocytic cells to the area
3
Phagocytic cells engulf
bacteria and cell debris;
tissue heals
The Lymphatic System
• The lymphatic system consists of
– a branching network of vessels,
– numerous lymph nodes, and
– several other organs.
• Lymphatic vessels carry lymph, a fluid that is
similar to interstitial fluid surrounding body cells.
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Figure 24.5
Tonsil
Lymph nodes
Lymphatic vessels
entering veins
Thymus
Appendix
Lymphatic
vessels
Spleen
The Lymphatic System
• The lymphatic system
– returns tissue fluid to the circulatory system and
– fights infection.
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ADAPTIVE DEFENSES
• Adaptive defenses
– are the third line of defense,
– are activated after exposure to specific pathogens,
and
– depend upon lymphocytes that recognize and
respond to specific invading pathogens.
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ADAPTIVE DEFENSES
• There are two types of lymphocytes:
1. B cells, which mature in the bone marrow, and
2. T cells, which mature in the thymus, a gland in the
chest.
• B cells and T cells eventually make their way to
– lymph nodes and
– other lymphatic organs.
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ADAPTIVE DEFENSES
• Antigens
– are molecules on the surfaces of viruses or foreign
cells and
– elicit a response from a lymphocyte.
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Recognizing the Invaders
• When a particular B cell binds to its particular
antigen, it gives rise to other short-lived cells,
which secrete a receptor-like molecule called an
antibody.
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Figure 24.7
Antigen
Antigenbinding
site
Antigen-binding
sites
Computer
model of an
antibody
Antibody
Recognizing the Invaders
• Antibodies
– are Y-shaped molecules,
– enable the immune system to react to just about
any kind of antigen, and
– combine with an antigen to form an antigenantibody complex.
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Responding to the Invaders
• B cells and T cells carry out a coordinated attack
along with the innate defenses.
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Clonal Selection: Multiplying Lymphocytes
• The primary immune response
– is the first response to exposure of lymphocytes to
an antigen and
– takes several days to produce effector cells via
clonal selection.
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Clonal Selection: Multiplying Lymphocytes
• B cells
– produce a peak amount of antibodies about two
weeks after first exposure and
– secrete their antibodies into the blood and lymph.
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Immunological Memory
• Clonal selection also produces memory cells,
which
– are long-lived, lasting decades,
– respond to subsequent exposures to a previously
encountered antigen, and
– give rise to
– effector cells and
– more memory cells.
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Immunological Memory
• In the secondary immune response, memory
cells
– bind to the antigen and
– initiate a faster and strong response.
• Thus, in adaptive defenses, but not innate
defenses, exposure to a particular antigen
enhances future responses to the same antigen.
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Vaccination
• Vaccination confronts the immune system with a
vaccine, which includes a harmless version of a
disease-causing microbe or one of its parts.
• A vaccine stimulates the immune system to mount
defenses against the actual pathogen possessing
the same antigens.
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Vaccination
• In the United States, vaccinations have virtually
eliminated
– polio,
– mumps, and
– smallpox.
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Colorized SEM
Figure 24.10
IMMUNE DISORDERS
• If the interplay of immune cells goes awry,
problems can arise that range from mild irritations
to deadly diseases.
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Allergies
• Allergies are exaggerated sensitivities to harmless
antigens in the environment.
• Allergens are antigens that cause allergies.
• The symptoms of an allergy result from a twostage reaction.
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Allergies
• Anaphylactic shock
– is an especially dangerous type of allergic reaction
and
– can be counteracted with injections of the hormone
epinephrine.
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Figure 24.15
Autoimmune Diseases
• The immune system
– normally reacts only against foreign (nonself)
substances but
– may attack
– our own tissues and
– tissues transplanted into our bodies.
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Autoimmune Diseases
• When the immune system improperly turns against
the body’s own molecules, it can lead to serious
autoimmune diseases such as
– lupus,
– insulin-dependent diabetes,
– multiple sclerosis, and
– rheumatoid arthritis.
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Figure 24.16
AIDS
• AIDS (acquired immunodeficiency syndrome)
– has killed more than 30 million people worldwide
and
– infects millions of new people each year.
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Figure 24.17
HIV
Colorized TEM
Human helper T cell
Figure 24.UN01
INNATE DEFENSES
Internal
External
• Skin
• Mucous
membranes
• Secretions
White blood cells
• Phagocytic cells
• Natural
killer cells
Defensive proteins The inflammatory response
• Interferons
• Complement
proteins
• Involves chemical
signals and
phagocytic cells
Figure 24.UN02
LYMPHOCYTES
(Immune system contains millions of different kinds.)
B cells
(humoral immune response)
• Secrete antibodies,
which mark invaders
T cells
(cell-mediated immune response)
• Attack infected cells
• Help activate B cells
Antigen receptors recognize
one specific kind of antigen.