9 - animal nutrition and digestion, before

8/6/2019 9 - Animal Nutrition and Digestion, Before

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Lecture #9 Animal Nutrition and

Digestion


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Key Concepts:

Animals are heterotrophic!

Nutritional needs what animals get from

food Food processing

The human digestive system


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Critical Thinking

Is this animal approaching the fruit or the

flower???

Why???


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Critical Thinking

Is this animal approaching the fruit or the

flower???

Why???


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Animals are always consumers

Only photosynthesis can convert solar

energy to usable chemical energy

Plants store chemical energy Animals eat plants (or other animals)

.of course this is somewhat simplified.

but NO animals are autotrophic


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Critical Thinking

Why do we eat??? Specifically, what do

we get from food???


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Critical Thinking

Why do we eat??? Specifically, what do

we get from food???


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Why we eat energy

Animals generate ATP by aerobic

respiration

Main substrate is carbohydratesFats are also used

Proteins are used as a last resort

Digestion converts consumed polymers tothe monomers used in respiration


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Diagram

bioenergetics and

the fate of food

Remember bioenergetics

Managing the energybudget is essential tomaintaining animal

function ATP powers basal

metabolism, other

activities; maintainshomeostasis; etc

Animals must eat tomake ATP


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Why we eat carbon skeletons

Animals need organic carbon scaffolds to

build our own organic molecules such

as???


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Why we eat essential nutrients

Molecules that animals cannot make at all

Do not have the right biosynthetic pathways

Must be eaten in pre-assembled form Some common to all animals; some

specialized

Essential amino acids

Essential fatty acids

Vitamins

Minerals


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Essential Amino Acids

Most animals use the same 20 amino acids

to make what???


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Essential Amino Acids

Most animals use the same 20 amino acids

to make

Most animals can only synthesize abouthalf

Remaining amino acids must be consumed

All animal proteins are complete contain all

the essential amino acids

All plant proteins are incomplete missing

some of the essential amino acids


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Chart essential amino acids; overlap between grains and legumes

Human vegetarian diets must mix plant

groups to obtain all essential amino acids

Grains and legumes mixed provide all essential amino acids cultural traditions prevent protein deficiencies


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Essential Fatty Acids

Some unsaturated fatty acids cannot be

synthesized

Most animals (especially humans!) get

adequate essential fatty acids from their

diet

We use fatty acids for????


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Essential Fatty Acids

Some unsaturated fatty acids cannot be

synthesized

Most animals (especially humans!) getadequate essential fatty acids from their

diet

We use fatty acids for


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Vitamins

Organic molecules used in small quantities

Water soluble vitamins usually function as

coenzymes

Fat soluble vitamins function in nutrient

absorption, as antioxidants, etc..

Deficiencies are rare with an adequate,

balanced diet


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Critical Thinking

Which category of vitamin is more likely to

accumulate and become toxic water

soluble or fat soluble??? Why???


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Critical Thinking

Which category of vitamin is more likely to

accumulate and become toxic water

soluble or fat soluble??? Why???


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Table essential vitamins; sources and functions

Study

table intext

for a

general

under-standing


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Minerals

Inorganic elements

Some required in small amounts; some in

larger

Requirements vary by taxon

Many different functions

Some metabolic; some structural

Know top 8 minerals and their main

functions


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Mineral Functions???

Calcium

Phosphorous

Sulfur Potassium

Chlorine

Sodium Magnesium

Iron


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Mineral Functions???

Calcium

Phosphorous

Sulfur Potassium

Chlorine

Sodium Magnesium

Iron


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Diagram food procession in a small mammal

Food Processing

Ingestion

Digestion

Absorption

Elimination


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Evolution of Compartmentalization

Food digestion must be contained

Earliest containment structures are food

vacuoles

Sponges digest entirely intra-cellularly

Most animals digest at least partly outside the

cells

Simplest body plans have a digestive sac with one

opening

More complex animals have a digestive tube with an

opening for ingestion and one for elimination


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vacuolesSponges digest entirely intra-cellularly


cells


opening




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Diagram sponges and their choanocytes

Sponges digest food in vacuoles that fuse with

lysosomes containing hydrolytic enzymes


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Avoids digestion of body cells and tissues




cells


opening




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Images a jellyfish and a flatwormDiagram two cell

layers in cnidarians

Jellies and flatworms start digestion in

gastrovascular cavities; finish in food vacuoles


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Jellies and flatworms start digestion in

gastrovascular cavities; finish in food vacuoles


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cells

Simplest body plans have a digestive sac with oneopening




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cells

Simplest body plans have a digestive sac with oneopening




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Critical Thinking

The 2-hole tube body plan processes food

sequentially no mixing of incoming food

and outgoing waste

Can you think of another advantage for the

2-hole tube plan???


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Critical Thinking

The 2-hole tube body plan processes food

sequentially no mixing of incoming food

and outgoing waste

Can you think of another advantage for the

2-hole tube plan???


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Diagram developmentof specialization in 2-hole

tubular digestive tracts in

earthworms, insects and

birds

Tubular system allows

for specialization andefficiency

Specialization based on

habitat and diet Both divergent and

convergent patterns haveemerged

All mammals have a cecum

Both earthworms and birdshave developed crops


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Schematic diagram

the human

digestive system

The Human Digestive System

Relatively straightforwardadaptations to an omnivorousdiet

Tube running from mouth toanus with specialized regions forfood processing, absorption, andelimination of wastes

Accessory glands supplylubrication, digestive enzymesand other secretions


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Diagram the human digestive tract


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Diagram the oral cavity, pharynx

and esophagus; same diagram onnext two slides

Oral cavity, pharynx and esophagus

allow for chewing and swallowing food

Teeth cut and grind

Tongue mixes and

pushes bolus to back

Saliva lubricates

food, protects the

mouth lining, bufferspH, kills bacteria, and

begins the digestion

of carbohydrates


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Diagram specifically the function of the epiglottis



Epiglottis tips down to direct food frompharynx to esophagus (so you dont breathe your food)


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Peristaltic contractions inesophagus push food to

stomach Food does not fall by

gravity remember ourquadruped ancestors

Sphincter (ring) musclesalso control passage offood


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Stomach continues the action

Stores food (very folded and stretchy)

Muscle contractions mix food

Lining secretes gastric juice

Very acidic (pH ~2) hydrochloric acid dissolvescell matrices and denatures proteins inswallowed food; also kills many ingested bacteria

Pepsin begins protein hydrolysis

Stomach lining protected from self-digestion bythick mucus and secretion of inactive pepsinprecursor

Controls passage of food into small intestine


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Diagram the somach lining and secreting cells


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Ulcers.. Stomach lining replaces itself by mitosis

about every 3 days

Lesions still sometimes occur Ulcer risk factors???


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Ulcers.. Stomach lining replaces itself by mitosis

about every 3 days

Lesions still sometimes occur

Ulcer risk factors

Helicobacter pylori

Tobacco

AlcoholCaffeine

Aspirin

Chocolate!

Ouch!!


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Other animals can get ulcers, too

From a students extra credit

Causes include stress, diet, genetic

abnormalities, microbial infections, veryfinely ground grains, heredity, bile reflux

that destroys stomach lining


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Stomach continues the action

Stores food (very folded and stretchy)

Muscle contractions mix food

Lining secretes gastric juice

Very acidic (pH ~2) hydrochloric acid dissolvescell matrices and denatures proteins inswallowed food; also kills many ingested bacteria

Pepsin begins protein hydrolysis

Stomach lining protected from self-digestion bythick mucus and secretion of inactive pepsinprecursor

Controls passage of food into small intestine


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Diagram the cells lining the stomach, secretion

of digestive juices


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The Small Intestine

Completes digestion andabsorbs monomersSome absorption occurs in other parts of the

digestive tract, but most in the SI

More than 6m long

Multiple levels of folding increase SA

Surface area about 600m2!!

Most digestion occurs in the first 25cm of the

small intestineEnzymatic hydrolysis

Most absorption occurs in the latter5.75m ofthe small intestine


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Diagram the human small intestine


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Diagram levels of folding in the human small intestine

Four levels of folding function to

increase surface area tube,interior folds, villi, microvilli


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The Small Intestine



More than 6m long







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Diagram the pancreas, liver and gall bladder; structure and function

Pancreas secretes enzymes and

bicarbonate; liver secretes bile


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Chart digestive enzymes; point of secretion and substrate; same

on next slide

Digestive enzymes and substrates


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Most digestion in duodenum (1st 25cm)


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The Small Intestine



More than 6m long







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Diagram fat digestion

process; same next

slideFat Digestion

Fats are hydrophobic

Bile salts emulsify large fatdroplets into smaller

droplets more surfacearea

Lipase digestion produces

fatty acids and mono-glycerides

These monomers forminto micelles


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Diagram how blood vessels absorb nutrients; same next slide

Intestinal blood vessels drain

directly into the hepatic portal vein

Nutrients get sent straight to the liver for

metabolic processing


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Intestinal blood vessels drain

directly into the hepatic portal vein

From the liver, the blood goes straight to the

heart for distribution throughout the body


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Diagram circulation

patterns in humans

showing relationship

between circulation andmajor organs

Critical Thinking

Where will the levels of

blood sugar and other

nutrients vary the most???


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Critical Thinking

Where will the levels of

blood sugar and other

nutrients vary the most???


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The large intestine, AKA the colon

Connected to SI at T junction

Dead-end of T is the cecum

Appendix extends off cecumCecum functions as fermentation chamber in

many animals, especially herbivores

Human cecum is small, relatively functionless

Appendix contributes to immune function, but

is dispensable

Appendix may function to repopulate intestines with

beneficial bacteria after intestinal infections


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Diagrams the cecum in omnivores

(humans) vs. specialized herbivores

(koalas)


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The large intestine, AKA the colon

Remainder of LI is ~ 1.5m

Main function is to absorb water

7l of fluid is secreted into intestinal lumen

Additional water is consumed in dietSI and LI together absorb ~ 90%

Inflammation of LI reduces water absorption diarrhea

LI also houses both commensal and mutualistic

bacteriaLive on undigested or unabsorbed materials

Produce important vitamins (K, Bs, folic acid, biotin)

Some produce stinky gasses as a byproduct of metabolism


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Diagram the human digestive tract with the large intestine highlighted


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Diet is a selection pressure

Dentition

Different tooth shapes for ripping and grinding

Length of small intestine

Herbivores typically have much longer SI Other compartments and symbioses

Fermentation chambers that house micro-organisms that can digest cellulose (animals

lack cellulases)Enlarged ceca (first feces are re-eaten)

Esophageal pouches (crops in some birds, thestomachs of ruminants)


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Critical Thinking

How might diet affect tooth evolution?

Carnivores

Herbivores Omnivores


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Critical Thinking

How might diet affect tooth evolution?

Carnivores

Herbivores Omnivores


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Diagram differences in tooth structure

Ripping, crushing and

shredding teeth

Biting and grinding teeth

Combo of teeth for

biting, tearing, grinding

and crushing


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Dentition








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Diagram differences in the digestive tract of

carnivore vs. herbivore

Most plant

material is

tough andfibrous the

longer

digestive tract

in herbivoresallows more

time and

space for

digestion andabsorption of

both nutrients

and water


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Dentition







E t t t h bi ti


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Diagram the digestive system of a cow

Extra compartments house symbiotic

micro-organisms food is often

regurgitated and / or re-consumed


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Review Key Concepts:

Animals are heterotrophic!

Nutritional needs

Energy

Carbon skeletons

Essential nutrients

Food processing

The human digestive system

Diet as a selection pressure

9 - animal nutrition and digestion, before

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