Week 4 The digestive system I Flashcards by Caitlin Norwood

What is digestive physiology?

All tissues that contribute to physical and chemical breakdown of food.

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What is included in an overview of digestive physiology?

Sensory system - neurosensory machinery
-locates food ( eyes,nostrils,antennae)
Physical structures- specialised structures
-mechanically disrupt food (tongue,teeth,madible)
Chemical processes
-break down food/digest it (enzymatic-outside animal)
Undigested food expelled by egestion

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What is assimilation?

Sequential process of nutrient acquisition and absorption.

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What cell types accomplish assimilation?

Absorptive - take up nutrients
Glands (endocrine and exocrine) - secrete chemicals e.g. mucus,acid,ions,enzymes
Muscles- control GIT shape and motility
Nerves- regulate GIT function

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How do animals sense food?

Using chemical,thermal and electrical cues.

They link a receptor to a signalling pathway which determines the behavioural response that alters feeding.

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What does an olfactory receptor detect?

Smell

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What chemical signals are used by cestodes?

Cestodes (tapeworms), e.g. Hymenolepis diminuta

-diurnal migrations up/down GIT of host following nutrients (the chemicals) released from meal.

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What chemical signals are used by Cnidarians?

Cnidarians, e.g. Hydra

-chemicals tells them prey is nearby (proline, reduced glutathione)

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What chemical signals are used by Complex Animals?

Complex animals, (herbivorous insects) e.g. aphids
• use gustatory & olfactory receptors
(taste-gustatory / smell-olfactory)
• some chemicals stimulate feeding (phagostimulant)
• some chemicals deter feeding (phagodeterrent)

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What chemical signals are used by vertebrates?

Vertebrates

-carrion eaters detect chemicals in rotting flesh

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What chemical signals are used by sharks?

Sharks
• gustatory signal
• chemicals found in vertebrate blood
• frenzied feeding behaviour – amplification cascade
• sharks feed
- more blood
- ↑ gustatory signal
- more sharks arrive to feed

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How do Energetic Signals work?

Predator senses energy emitted/reflected from animal

• light, sound, heat, electricity

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What are some examples of energetic signals?

Bird of prey (golden eagle)
• uses visual system to locate field mouse

Insects
• detect infrared light emission from warm bodies

Firefly, Photuris
• predatory species produce light pattern that mimics mating signal

Bat-eared fox, Otocyon megalotis
• Detects prey using audible sounds

Bats
• Detect ultrasonic signals
• Emit signals & detect return of signal
- echolocation

Snakes
• Detect thermal energy emitted from live prey
• Thermal detection on both sides of head
- When signals are equal? - middle route-

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Which animals use echolocation to determine prey?

Bats and Dolphins

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What are energetic signals?

visual system
infrared light emission
light pattern
audible sounds
ultrasonic signals (echolocation)
thermal energy

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What does GIT stand for?

Gastrointestinal tract

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How did the digestive system evolve?

• increasing anatomical and functional specialisation
2-way gut
1-way gut

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What is a two-way gut?

Simple digestive sacs - food enters & leaves through a single opening

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Give an example of a two-way gut.

Platyhelminths
• Simple sac (small flatworms)
• Complex sac with many side branches, diverticula (larger flatworms)

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How does digestion in a two-way gut work?

Study These Flashcards

Digestion – begins in lumen
Proteases secreted from sac wall – digest food > small particles
Cells lining sac phagoctose partially digested particles
NB. cells have subtly different functions > regional specialisation

What is a one-way gut?

Study These Flashcards

Food ingested at one end, egested at other end
Specialised regions more developed
• vary widely among animals
• increase efficiency of digestion (important)

What are some specialised regions of GIT?

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Specialised regions - aid digestion
-General plan of GIT is common in vertebrates
-Many animal taxa differ in terms of modified regions
• Oesophagus of birds includes crop
• Stomach of birds includes gizzard
• Modified digastric stomach in ruminants
• Ceca in birds and bony fish (commensal bacteria)

What are the regions of mammalian GIT?

Study These Flashcards

• Mouth
• Pharynx
• Oesophagus
• Stomach(s)
• Small intestine
(duodenum, jejunum &amp; ileum)
• Large intestine
(cecum &amp; colon)
• Rectum
• Anus

What is the upper region of a mammalian GIT and what does it do?

Study These Flashcards

• Mouth
• Pharynx
• Oesophagus
- all of these are responsible for mechanical breakdown of food

What is the gastric region of a mammalian GIT?

-Stomach(s) | in most animals is acidic

What is the upper intestine of a mammalian GIT and what does it do?

-Small intestine (duodenum, jejunum & ileum) Neutralises acidic solution Carries out digestion Carries out nutrient absorption

What is the lower intestine of a mammalian GIT and what does it do?

-Large intestine (cecum & colon) | Reabsorbs water & electrolytes

What does the rest of a mammalian GIT do?

-Rectum & Anus Package & release of indigestible material

What parts are not included in the mammalian GIT yet regulate digestion as well?

-Side chambers that branch out from main GIT -Muscular valves (sphincters) that regulate passage through different compartments e.g. cardiac and pyloric sphincters

How do different species differ in their GIT?

-Different species evolved different regions to manage different diets -Most mammals are monogastric -Ruminants are polygastric e.g. cattle, sheep, deer • rumen • reticulum • omasum • abomasum

What does a polygastric GIT include?

* rumen * reticulum * omasum * abomasum

What is the first pair of compartments of a polygastric GIT and what does it do?

``` rumen & reticulum - contain fermentative bacteria • digests cellulose • produces volatile fatty acids & gases (CO2 & methane) ```

What is the second division of compartments of a polygastric GIT and what does it do?

omasum & abomasum -obomasum = glandular stomach • secretes digestive enzymes

What developmental GIT variations exist within species?

Mammalian fetus & infant • maternal blood borne nutrients (placenta) • mammary gland secretions • solid food Insects e.g. larval lepidopterans (catapillars) & butterflies • plant leafy material vs nectar

What other inter-species GIT variation exists?

-Sexual variation Male & female mosquitos • nectar vs blood

What are all inter-species GIT variations?

- monogastric vs polygastric variation - developmental variation - sexual variation

What is Ingestion?

primary route to gain chemicals from environment

How are nutrients obtained and what is done with them?

-MOST animals – absorb nutrients across epithelium of GIT -Aquatic animals – obtain some essential ions across external epithelial surface e.g. skin, gills -Absorbed nutrients may be catabolised (to yield energy) OR anabolised (used to create new molecules)

What are essential nutrients? Give examples

Nutrients that can only be obtained from the diet • cannot be made de novo – Vitamins (e.g. VitC humans) – Minerals (e.g. Na, K, Ca) – Amino acids (typically 8 essential AA)- isoleucine, leucine, lysine, methionine, phenylalanine,threonine, tryptophan & valine – Essential fatty acids (omega-3 & omega-6)

What is protein quality?

Protein is the dietary source of AA | Protein quality – profile of AA in dietary protein

Is Plant protein higher quality dietary protein than animal protein? Explain your answer

No, that is false. -Animal protein – higher-quality dietary protein • AA profile more closely matched to the needs of animal -Plant protein – often deficient in 1/more essential AA • E.g. maize protein lacks lysine, wheat protein lacks tryptophan • Significance = herbivore must eat range of plants to ensure it gets ALL essential AA

What are non-essential nutrients?

Nutrients that animals can produce from other molecules • can be made de novo • metabolise essential nutrients using enzymes

What/Which are digestive enzymes and what is their function?

-most animals use same family of digestive enzymes • convert complex macromolecules into form that is readily absorbed by animal – Lipases – Proteases – Amylases – Nucleases

What are lipases/ what do they do?

Lipases – Release FA from triglycerides & phospholipids – E.g.Triglyceride lipase & phospholipase

What are proteases/ what do they do?

-Break down proteins into shorter polypeptides (e.g. trypsin) Different types attack protein at different points – E.g. Peptidases, aminopeptidases, carboxypeptidases, dipeptidases

What are amylases/ what do they do?

-Break down polysaccharides into oligosaccharides (e.g. dextrinase) Disaccharidases break down specific disaccharides – e.g. maltase hydrolyses maltose into glucose

What are Nucleases/ what do they do?

- Break down DNA into nucleotides - Nucleotides broken down into nucleosides & nitrogenous bases - no example

Is a oneway or twoway gut more efficient?

One-way gut, allows for better absorption of nutrients.

Week 4 The digestive system I Flashcards

(48 cards)