Chapter 40Chapter 40

Introduction to Animal Structure and Function

Overview: Diverse Forms, Common Challenges

• Anatomy is the study of the biological form of an organism

• Physiology is the study of the biological functions an organism performs

(a) Tuna

(b) Penguin

(c) Seal

Exchange with the Environment

• An animal’s size and shape directly affect how it exchanges energy and materials with its surroundings

• Multicellular organisms with a sac body plan have body walls that are only two cells thick, facilitating diffusion of materials

• More complex organisms have highly folded internal surfaces for exchanging materials

• In vertebrates, the space between cells is filled with interstitial fluid, which allows for the movement of material into and out of cells

Exchange

0.15 mm

(a) Single cell

1.5 mm

(b) Two layers of cells

Exchange

Exchange

Mouth

Gastrovascularcavity

0.5 cmNutrients

Digestivesystem

Lining of small intestine

MouthFood

External environment

Animalbody

CO2 O2

Circulatorysystem

Heart

Respiratorysystem

Cells

Interstitialfluid

Excretorysystem

Anus

Unabsorbedmatter (feces)

Metabolic waste products(nitrogenous waste)

Kidney tubules

10 µm

50 µ

m

Lung tissue

• Most animals are composed of specialized cells organized into tissues that have different functions

• Tissues make up organs, which together make up organ systems

Hierarchical Organization of Body Plans

Tissue Structure and Function- Epithelial Tissue

• 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)

Epithelial Tissue

Cuboidalepithelium

Simplecolumnarepithelium

Pseudostratifiedciliatedcolumnarepithelium

Stratifiedsquamousepithelium

Simplesquamousepithelium

Tissue Structure and Function- Connective Tissue

• 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

• Connective tissue contains cells, including

– Fibroblasts that secrete the protein of extracellular fibers

– Macrophages that are involved in the immune system

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

• 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 is composed of blood cells and cell fragments in blood plasma

• Bone is mineralized and forms the skeleton

Connective Tissue

Collagenous fiber

Looseconnectivetissue

Elastic fiber12

0 µ

m

Cartilage

Chondrocytes

10

0 µ

m

Chondroitinsulfate

Adiposetissue

Fat droplets

15

0 µ

m

White blood cells

55

µm

Plasma Red bloodcells

Blood

Nuclei

Fibrousconnectivetissue

30

µm

Osteon

Bone

Central canal

70

0 µ

m

Loose connective tissue

Fibrous connective tissue

Bone

Cartilage

Adipose tissue

Blood

Tissue Structure and Function- 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

Muscle Tissue

50 µmSkeletalmuscle

Multiplenuclei

Muscle fiber

Sarcomere

100 µm

Smoothmuscle

Cardiac muscle

Nucleus

Musclefibers

25 µm

Nucleus Intercalateddisk

Skeletal muscle

Multiplenuclei

Muscle fiber

Sarcomere

100 µm

Smooth muscle

Nucleus

Musclefibers

25 µm

Nucleus Intercalateddisk

Cardiac muscle

50 µm

Tissue Structure and Function- Nervous Tissue

• Nervous tissue senses stimuli and transmits signals throughout the animal

• Nervous tissue contains:

– Neurons, or nerve cells, that transmit nerve impulses

– Glial cells, or glia, that help nourish, insulate, and replenish neurons

Glial cells

Nervous Tissue

15 µm

Dendrites

Cell body

Axon

Neuron

Axons

Blood vessel

40 µm

Dendrites

Cell body

Axon

40 µm

Neuron

Glial cells

Axons

Blood vessel

Glial cells and axons15 µm

Stimulus

Hormone

Endocrinecell

Signal travelseverywherevia the bloodstream.

Bloodvessel

Response

(a) Signaling by hormones

Stimulus

Neuron

AxonSignal

Signal travelsalong axon toa specificlocation.

Signal

Axons

Response

(b) Signaling by neurons

Coordination and Control

Homeostasis

• Organisms use homeostasis to maintain a “steady state” or internal balance regardless of external environment

• In humans, body temperature, blood pH, and glucose concentration are each maintained at a constant level

Response:Heater turnedoff

Stimulus:Control center(thermostat)reads too hot

Roomtemperaturedecreases

Setpoint:20ºC

Roomtemperature

increases

Stimulus:Control center(thermostat)

reads too cold

Response:Heater turnedon

Feedback Loops in Homeostasis

• Negative feedback -returns a variable to either a normal range or a set point, buildup of the end product shuts the system off

• Positive feedback- the end product accelerates the systems further

• Endothermic animals generate heat by metabolism; more active; energy expensive

• Ectothermic animals gain heat from external sources; less active; less energy needed

Endothermy and Ectothermy

(a) A walrus, an endotherm

(b) A lizard, an ectotherm

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 at a “comfortable” temperature

• Standard metabolic rate (SMR) is the metabolic rate of an ectotherm at rest at a specific temperature

• 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 oxygen delivery rate, breathing rate, heart rate, and greater (relative) blood volume, compared with a larger animal

Shrew

Harvest mouseMouse

Ground squirrel

Rat

Cat Dog

Sheep

Human

Horse

Elephant

Body mass (kg) (log scale)

BM

R (

L O

2/h

r) (

log

sc

ale

)

(a) Relationship of BMR to body size

10–3 10–210–2

10–1

10–1

1

1

10 102 103

10

102

103

10310210110–110–210–30

1

2

3

4

5

6

7

8

Body mass (kg) (log scale)

(b) Relationship of BMR per kilogram of body mass to body size

BM

R (

L O

2/h

r) (

pe

r kg

)Shrew

Harvest mouse

Mouse

Rat

Ground squirrel

Cat

Sheep

DogHuman

Horse

Elephant

• Different species use energy and materials in food in different ways, depending on their environment

• Use of energy is partitioned to BMR (or SMR), activity, thermoregulation, growth, and reproduction

Energy Budgets

An

nu

al e

ner

gy

exp

end

itu

re (

kcal

/hr)

60-kg female humanfrom temperate climate

800,000Basal(standard)metabolism

ReproductionThermoregulation

Growth

Activity

340,000

4-kg male Adélie penguinfrom Antarctica (brooding)

4,000

0.025-kg female deer mousefrom temperateNorth America

8,000

4-kg female easternindigo snake

Endotherms Ectotherm

An

nu

al e

ne

rgy

ex

pe

nd

itu

re (

kc

al/h

r)

60-kg female humanfrom temperate climate

800,000Basal(standard)metabolism

ReproductionThermoregulation

Growth

Activity

Reproduction

Thermoregulation

Activity

Basal(standard)metabolism

4-kg male Adélie penguinfrom Antarctica (brooding)

An

nu

al e

ner

gy

exp

end

itu

re (

kcal

/yr)

340,000

Reproduction

Thermoregulation

Basal(standard)metabolism

Activity

4,000

0.025-kg female deer mousefrom temperateNorth America

An

nu

al e

ner

gy

exp

end

itu

re (

kcal

/yr)

Reproduction

Growth

Activity

Basal(standard)metabolism

4-kg female easternindigo snake

8,000

An

nu

al e

ner

gy

exp

end

itu

re (

kcal

/yr)