Chap 40 Animal Structure and Function. Epithelia are classified by the number of cell layers and the...

Chap 40

Animal Structure and Function

• Epithelia are classified by the number of cell layers and the shape of the cells on the free surface.

• A simple epithelium has a single layer of cells, and a stratified epithelium has multiple tiers of cells.

• The shapes of cells may be cuboidal (like dice), columnar (like bricks on end), or squamous (flat like floor tiles).

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 40.1

• There are three kinds of connective tissue fibers, which are all proteins: collagenous fibers, elastic fibers, and reticular fibers.

1. Collagenous fibers are made of collagen.– Collagenous fibers are nonelastic and do not tear

easily when pulled lengthwise.

2. Elastic fibers are long threads of elastin.– Elastin fiber provide a rubbery quality.

3. Reticular fibers are very thin and branched.– Composed of collagen and continuous with

collagenous fibers, they form a tightly woven fabric that joins connective tissue to adjacent tissues.


CoREl

Six major types of connective tissues in vertebrates are:

1. loose connective tissue, 2. adipose tissue, 3. fibrous connective tissue, 4. cartilage, 5. bone, and 6. blood.

– Each has a structure correlated with its specialized function.

Fig. 40.2Laura finds computers at Best Buy.

Binds epithelia to underlying tisssue

Binds epithelia to underlying tisssue

Pads, insulates, stores fuel

Pads, insulates, stores fuel

Tendons and ligaments

Tendons and ligaments

1

2

3

4

5

6

• Loose connective tissue binds epithelia to underlying tissues and functions as packing materials, holding organs in place.– Loose connective tissue has all three fiber

types.

• Two cell types predominated in the fibrous mesh of loose connective tissue.– Fibroblasts secrete the protein

ingredients of the extracellular fibers.– Macrophages are amoeboid cells that

roam the maze of fibers, engulfing bacteria and the debris of dead cells by phagocytosis.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• Blood functions differently from other connective tissues, but it does have an extensive extracellular matrix.– The matrix is a liquid called plasma, consisting of

water, salts, and a variety of dissolved proteins.– Suspended in the plasma are erythrocytes (red blood

cells), leukocytes (white blood cells) and cell fragments called platelets.• Red cells carry oxygen.

• White cells function in defense against viruses, bacteria, and other invaders.

• Platelets aid in blood clotting.


• Cartilage has an abundance of collagenous fibers embedded in a rubbery matrix made of a substance called chondroitin sulfate, a protein-carbohydrate complex.– Chondrocytes secrete collagen and chondroitin sulfate.

– The composite of collagenous fibers and chondroitin sulfate makes cartilage a strong yet somewhat flexible support material.

– The skeleton of a shark is made of cartilage and the embryonic skeletons of many vertebrates are cartilaginous.

– We retain cartilage as flexible supports in certain locations, such as the nose, ears, and vertebral disks.


• The skeleton supporting most vertebrates is made of bone, a mineralized connective tissue.– Osteoblasts deposit a matrix of collagen.

– Then, calcium, magnesium, and phosphate ions combine and harden within the matrix into the mineral hydroxyapatite.

– The osteoblast becomes an osteocyte in the Lacuna.

– The combination of hard mineral and flexible collagen makes bone harder than cartilage without being brittle.

– The microscopic structure of hard mammalian bones consists of repeating units called osteons (or Haversian systems)..• Each osteon has concentric layers of

mineralized matrix deposited around a

central canal containing blood vessels

and nerves that service the bone.


osteon

–The osteoblast becomes an osteocyte in the Lacuna.

• Nervous tissue senses stimuli and transmits signals from one part of the animal to another.– The functional unit of nervous tissue is the neuron,

or nerve cell.– It consists of a cell body and two or more

extensions, called dendrites and axons.– Dendrites transmit nerve impulses from their tips

toward the rest of the neuron.– Axons transmit impulses toward

another neuron or toward an effector, such as a muscle cell.


Fig. 40.3

• There are three types of muscle tissue in the vertebrate body: skeletal muscle, cardiac muscle, and smooth muscle.


Fig. 40.4

One cell

• Attached to bones by tendons, skeletal muscle is responsible for voluntary movements.– Skeletal muscle is also called striated muscle

because the overlapping filaments give the cells a striped (striated) appearance under the microscope.

• Cardiac muscle forms the contractile wall of the heart.– It is striated like cardiac muscle, but cardiac cells

are branched.– The ends of the cells are joined by intercalated

disks, which relay signals from cell to cell during a heartbeat.


Animals w/o a circulatory system must keep a large SA/Volume ratio

Multi-celled Animals are two layered thick so each cell is in contact with the environment.

• Organisms with more complex body plans– Have highly folded internal surfaces specialized for

exchanging materials

External environment

Food CO2 O2Mouth

Animalbody

Respiratorysystem

Circulatorysystem

Nutrients

Excretorysystem

Digestivesystem

Heart

Blood

Cells

Interstitialfluid

Anus

Unabsorbedmatter (feces)

Metabolic wasteproducts (urine)

The lining of the small intestine, a diges-tive organ, is elaborated with fingerlikeprojections that expand the surface areafor nutrient absorption (cross-section, SEM).

A microscopic view of the lung reveals that it is much more spongelike than balloonlike. This construction provides an expansive wet surface for gas exchange with the environment (SEM).

Inside a kidney is a mass of microscopic tubules that exhange chemicals with blood flowing through a web of tiny vessels called capillaries (SEM).

0.5 cm

10 µm

50 µ

m

Figure 40.4

• The amount of energy an animal uses in a unit of time is called its metabolic rate - the sum of all the energy-requiring biochemical reactions occurring over a given time interval.– Energy is measured in calories (cal) or kilocalories

(kcal).• A kilocalorie is 1,000 calories.

• The term Calorie, with a capital C, as used by many nutritionists, is actually a kilocalorie.


Metabolic rate provides clues to an animal’s bioenergetic “strategy”

• There are two basic bioenergetic “strategies” used by animals.– Birds and mammals are mainly endothermic,

maintaining their body temperature at a certain level with heat generated by metabolism.• Endothermy is a high-energy strategy that permits

intense, long-duration activity of a wide range of environmental temperatures.


– Most fishes, amphibians, reptiles, and invertebrates are ectothermic, meaning they do not produce enough metabolic heat to have much effect on body temperature.• The ectothermic strategy requires much less energy than

is needed by endotherms, because of the energy cost of heating (or cooling) an endothermic body.

• However, ectotherms are generally incapable of intense activity over long periods.


• One of animal biology’s most intriguing, but largely unanswered questions has to do with the relationship between body size and metabolic rate.– Physiologists have shown that the amount of energy it

takes to maintain each gram of body weight is inversely related to body size.

– For example, each gram of a mouse consumes about 20 times more calories than a gram of an elephant.

3. Metabolic rate per gram is inversely related to body size

among similar animals

• One hypothesis for the inverse relationship between metabolic rate and size is that the smaller the size of an endotherm, the greater the energy cost of maintaining a stable body temperature.– The smaller the animal, the greater its surface to

volume ratio, and thus the greater loss of heat to (or gain from) the surroundings.

• However, this hypothesis fails to explain the inverse relationship between metabolism and size in ectotherms.

• Nor is it supported by experimental tests.• Researchers continue to search for causes

underlying this inverse relationship.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• The basal metabolic rate (BMR)– Is the metabolic rate of an endotherm at rest

• The standard metabolic rate (SMR)– Is the metabolic rate of an ectotherm at rest

• For both endotherms and ectotherms– Activity has a large effect on metabolic rate

Activity and Metabolic Rate

Size and Metabolic Rate

• Metabolic rate per gram– Is inversely related to body size among similar

animals

• In general, an animal’s maximum possible metabolic rate– Is inversely related

to the duration of the activity

Figure 40.9

Max

imum

met

abol

ic r

ate

(kca

l/min

; log

sca

le)

500

100

50

10

5

1

0.5

0.1

A H

AH

A

A

A

H

H

H

A = 60-kg alligator

H = 60-kg human

1second

1minute

1hour

Time interval

1day

1week

Key

Existing intracellular ATP

ATP from glycolysis

ATP from aerobic respiration

• The BMR of a human is much higher than the SMR of an alligator.

• Both can reach high levels of maximum potential metabolicrates for short periods, but metabolic rate drops as the duration of the activityincreases and the source of energy shifts toward aerobic respiration.

Fig. 40.12

• Sustained activity depends on the aerobic process of cellular respiration for ATP supply.– An endotherm’s respiration rate is about 10 times

greater than an ectotherm’s.– Only endotherms are capable of long-duration

activities such as distance running.


• An animal’s use of energy– Is partitioned to BMR (or SMR), activity,

homeostasis, growth, and reproductionEndotherms Ectotherm

Ann

ual e

nerg

y ex

pend

iture

(kc

al/y

r)

800,000Basalmetabolicrate

ReproductionTemperatureregulation costs

Growth

Activitycosts

60-kg female humanfrom temperate climate

Total annual energy expenditures (a)

340,000

4-kg male Adélie penguinfrom Antarctica (brooding)

4,000

0.025-kg female deer mousefrom temperateNorth America

8,000

4-kg female pythonfrom Australia

Ene

rgy

expe

nditu

re p

er u

nit

mas

s (k

cal/k

g•da

y)

438

Deer mouse

233

Adélie penguin

36.5

Human

5.5

Python

Energy expenditures per unit mass (kcal/kg•day)(b)

Figure 40.10a, b

• Concept 40.4: Animals regulate their internal environment within relatively narrow limits

• The internal environment of vertebrates– Is called the interstitial fluid, and is very different

from the external environment

• Homeostasis is a balance between external changes– And the animal’s internal control mechanisms that

oppose the changes

• Regulating and conforming– Are two extremes in how animals cope with

environmental fluctuations

Regulating and Conforming

• An animal is said to be a regulator– If it uses internal control mechanisms to moderate

internal change in the face of external, environmental fluctuation

• An animal is said to be a conformer– If it allows its internal condition to vary with certain

external changes

• Mechanisms of homeostasis– Moderate changes in the internal environment

Mechanisms of Homeostasis

• A homeostatic control system has three functional components– A receptor, a control center, and an effector

Figure 40.11

Response

No heatproduced

Roomtemperaturedecreases

Heaterturnedoff

Set point

Toohot

Setpoint

Control center:thermostat

Roomtemperatureincreases

Heaterturnedon

Toocold

Response

Heatproduced

Setpoint

• Most homeostatic control systems function by negative feedback– Where buildup of the end product of the

system shuts the system off

• A second type of homeostatic control system is positive feedback– Which involves a change in some variable that

triggers mechanisms that amplify the change

• Concept 40.5: Thermoregulation contributes to homeostasis and involves anatomy, physiology, and behavior

• Thermoregulation– Is the process by which animals maintain an

internal temperature within a tolerable range

• Ectotherms– Include most invertebrates, fishes, amphibians, and

non-bird reptiles

• Endotherms– Include birds and mammals

Ectotherms and Endotherms

• In general, ectotherms– Tolerate greater

variation in internal temperature than endotherms

Figure 40.12

River otter (endotherm)

Largemouth bass (ectotherm)

Ambient (environmental) temperature (°C)

Bod

y te

mpe

ratu

re (

°C)

40

30

20

10

10 20 30 400

• Endothermy is more energetically expensive than ectothermy– But buffers animals’ internal temperatures

against external fluctuations– And enables the animals to maintain a high

level of aerobic metabolism

Modes of Heat Exchange• Organisms exchange heat by four physical

processesRadiation is the emission of electromagnetic waves by all objects warmer than absolute zero. Radiation can transfer heat between objects that are not in direct contact, as when a lizard absorbs heat radiating from the sun.

Evaporation is the removal of heat from the surface of aliquid that is losing some of its molecules as gas. Evaporation of water from a lizard’s moist surfaces that are exposed to the environment has a strong cooling effect.

Convection is the transfer of heat by the movement of air or liquid past a surface, as when a breeze contributes to heat loss from a lizard’s dry skin, or blood moves heat from the body core to the extremities.

Conduction is the direct transfer of thermal motion (heat) between molecules of objects in direct contact with each other, as when a lizard sits on a hot rock.

Figure 40.13

Balancing Heat Loss and Gain

• Thermoregulation involves physiological and behavioral adjustments– That balance heat gain and loss

Insulation

• Insulation, which is a major thermoregulatory adaptation in mammals and birds– Reduces the flow of heat between an animal

and its environment– May include feathers, fur, or blubber

Hair

Sweatpore

Muscle

Nerve

Sweatgland

Oil glandHair follicle

Blood vessels

Adipose tissue

Hypodermis

Dermis

Epidermis

• In mammals, the integumentary system– Acts as insulating material

Figure 40.14

• Many endotherms and some ectotherms– Can alter the amount of blood flowing between

the body core and the skin

Circulatory Adaptations

• In vasodilation– Blood flow in the skin increases, facilitating heat

loss

• In vasoconstriction– Blood flow in the skin decreases, lowering heat loss

• Many marine mammals and birds– Have

arrangements of blood vessels called countercurrent heat exchangers that are important for reducing heat loss

In the flippers of a dolphin, each artery issurrounded by several veins in acountercurrent arrangement, allowingefficient heat exchange between arterialand venous blood.

Canadagoose

Artery Vein

35°C

Blood flow

VeinArtery

30º

20º

10º

33°

27º

18º

9º

Pacific bottlenose dolphin

2

1

3

2

3

Arteries carrying warm blood down thelegs of a goose or the flippers of a dolphinare in close contact with veins conveyingcool blood in the opposite direction, backtoward the trunk of the body. Thisarrangement facilitates heat transferfrom arteries to veins (blackarrows) along the entire lengthof the blood vessels.

1

Near the end of the leg or flipper, wherearterial blood has been cooled to far below the animal’s core temperature, the artery can still transfer heat to the even colderblood of an adjacent vein. The venous bloodcontinues to absorb heat as it passes warmer and warmer arterial blood traveling in the opposite direction.

2

As the venous blood approaches the center of the body, it is almost as warm as the body core, minimizing the heat lost as a result of supplying blood to body partsimmersed in cold water.

3

Figure 40.15

1 3

• Some specialized bony fishes and sharks– Also possess countercurrent heat exchangers

Figure 40.16a, b

21º25º 23º

27º

29º31º

Body cavity

SkinArtery

Vein

Capillarynetwork withinmuscle

Dorsal aortaArtery andvein underthe skin

Heart

Bloodvesselsin gills

(a) Bluefin tuna. Unlike most fishes, the bluefin tuna maintainstemperatures in its main swimming muscles that are much higherthan the surrounding water (colors indicate swimming muscles cutin transverse section). These temperatures were recorded for a tunain 19°C water.

(b) Great white shark. Like the bluefin tuna, the great white sharkhas a countercurrent heat exchanger in its swimming muscles thatreduces the loss of metabolic heat. All bony fishes and sharks loseheat to the surrounding water when their blood passes through thegills. However, endothermic sharks have a small dorsal aorta, and as a result, relatively little cold blood from the gills goes directly to the core of the body. Instead, most of the blood leaving the gillsis conveyed via large arteries just under the skin, keeping cool bloodaway from the body core. As shown in the enlargement, smallarteries carrying cool blood inward from the large arteries under theskin are paralleled by small veins carrying warm blood outward fromthe inner body. This countercurrent flow retains heat in the muscles.

• Many endothermic insects– Have countercurrent

heat exchangers that help maintain a high temperature in the thorax

Figure 40.17

Cooling by Evaporative Heat Loss

• Many types of animals– Lose heat through the evaporation of water in

sweat– Use panting to cool their bodies

• Bathing moistens the skin– Which helps to cool an animal down

Figure 40.18

• Both endotherms and ectotherms– Use a variety of behavioral responses to control

body temperature

Behavioral Responses

• Some terrestrial invertebrates– Have certain

postures that enable them to minimize or maximize their absorption of heat from the sun

Figure 40.19

Adjusting Metabolic Heat Production

• Some animals can regulate body temperature– By adjusting their rate of metabolic heat

production

• Many species of flying insects– Use shivering

to warm up before taking flight

Figure 40.20

PREFLIGHT PREFLIGHTWARMUP

FLIGHT

Thorax

Abdomen

Tem

per

atur

e (°

C)

Time from onset of warmup (min)

40

35

30

25

0 2 4

• Mammals regulate their body temperature– By a complex negative feedback system that

involves several organ systems

Feedback Mechanisms in Thermoregulation

• In humans, a specific part of the brain, the hypothalamus– Contains a group of

nerve cells that function as a thermostat

Thermostat inhypothalamusactivates coolingmechanisms.

Sweat glands secrete sweat that evaporates, cooling the body.

Blood vesselsin skin dilate:capillaries fillwith warm blood;heat radiates fromskin surface.

Body temperaturedecreases;thermostat

shuts off coolingmechanisms.

Increased bodytemperature (suchas when exercising

or in hotsurroundings)

Homeostasis:Internal body temperatureof approximately 36–38C

Body temperatureincreases;thermostat

shuts off warmingmechanisms.

Decreased bodytemperature

(such as whenin cold

surroundings)

Blood vessels in skinconstrict, diverting bloodfrom skin to deeper tissuesand reducing heat lossfrom skin surface.

Skeletal muscles rapidlycontract, causing shivering,which generates heat.

Thermostat inhypothalamusactivateswarmingmechanisms.

Figure 40.21

HOT

COLD

Adjustment to Changing Temperatures

• In a process known as acclimatization– Many animals can adjust to a new range of

environmental temperatures over a period of days or weeks

• Acclimatization may involve cellular adjustments– Or in the case of birds and mammals,

adjustments of insulation and metabolic heat production

Torpor and Energy Conservation

• Torpor– Is an adaptation that enables animals to save

energy while avoiding difficult and dangerous conditions

– Is a physiological state in which activity is low and metabolism decreases

• Hibernation is long-term torpor– That is an adaptation to winter cold and food scarcity

during which the animal’s body temperature declines

Additional metabolism that would benecessary to stay active in winter

Actualmetabolism

Bodytemperature

Arousals

Outsidetemperature Burrow

temperature

June August October December February April

Tem

pera

ture

(°C

)M

etab

olic

rat

e(k

cal p

er d

ay)

200

100

0

35

30

25

20

15

10

5

0

-5

-10

-15

Figure 40.22

• 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 to be adapted to their feeding patterns

Chap 40 Animal Structure and Function. Epithelia are classified by the number of cell layers and the...

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