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BIO125 Physiology > Week 4 The digestive system I > Flashcards

Week 4 The digestive system I Flashcards

1
Q

What is digestive physiology?

A

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

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2
Q

What is included in an overview of digestive physiology?

A

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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3
Q

What is assimilation?

A

Sequential process of nutrient acquisition and absorption.

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4
Q

What cell types accomplish assimilation?

A

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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5
Q

How do animals sense food?

A

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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6
Q

What does an olfactory receptor detect?

A

Smell

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7
Q

What chemical signals are used by cestodes?

A

Cestodes (tapeworms), e.g. Hymenolepis diminuta

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

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8
Q

What chemical signals are used by Cnidarians?

A

Cnidarians, e.g. Hydra

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

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9
Q

What chemical signals are used by Complex Animals?

A

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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10
Q

What chemical signals are used by vertebrates?

A

Vertebrates

-carrion eaters detect chemicals in rotting flesh

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11
Q

What chemical signals are used by sharks?

A 
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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12
Q

How do Energetic Signals work?

A

Predator senses energy emitted/reflected from animal

• light, sound, heat, electricity

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13
Q

What are some examples of energetic signals?

A

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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14
Q

Which animals use echolocation to determine prey?

A

Bats and Dolphins

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15
Q

What are energetic signals?

A
  • visual system
  • infrared light emission
  • light pattern
  • audible sounds
  • ultrasonic signals (echolocation)
  • thermal energy
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16
Q

What does GIT stand for?

A

Gastrointestinal tract

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17
Q

How did the digestive system evolve?

A

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

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18
Q

What is a two-way gut?

A

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

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19
Q

Give an example of a two-way gut.

A

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

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20
Q

How does digestion in a two-way gut work?

A

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

21
Q

What is a one-way gut?

A

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

22
Q

What are some specialised regions of GIT?

A

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)

23
Q

What are the regions of mammalian GIT?

A 
• Mouth
• Pharynx
• Oesophagus
• Stomach(s)
• Small intestine
(duodenum, jejunum & ileum)
• Large intestine
(cecum & colon)
• Rectum
• Anus
24
Q

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

A

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

25
Q

What is the gastric region of a mammalian GIT?

A

-Stomach(s)

in most animals is acidic

26
Q

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

A

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

27
Q

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

A

-Large intestine (cecum & colon)

Reabsorbs water & electrolytes

28
Q

What does the rest of a mammalian GIT do?

A

-Rectum & Anus
Package & release of
indigestible material

29
Q

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

A

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

30
Q

How do different species differ in their GIT?

A

-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

31
Q

What does a polygastric GIT include?

A
  • rumen
  • reticulum
  • omasum
  • abomasum
32
Q

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

A 
rumen & reticulum
- contain fermentative bacteria
• digests cellulose
• produces volatile fatty acids & gases
(CO2 & methane)
33
Q

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

A

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

34
Q

What developmental GIT variations exist within species?

A

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

35
Q

What other inter-species GIT variation exists?

A

-Sexual variation
Male & female mosquitos
• nectar vs blood

36
Q

What are all inter-species GIT variations?

A
  • monogastric vs polygastric variation
  • developmental variation
  • sexual variation
37
Q

What is Ingestion?

A

primary route to gain chemicals from environment

38
Q

How are nutrients obtained and what is done with them?

A

-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)

39
Q

What are essential nutrients? Give examples

A

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)

40
Q

What is protein quality?

A

Protein is the dietary source of AA

Protein quality – profile of AA in dietary protein

41
Q

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

A

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

42
Q

What are non-essential nutrients?

A

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

43
Q

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

A

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

44
Q

What are lipases/ what do they do?

A

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

45
Q

What are proteases/ what do they do?

A

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

46
Q

What are amylases/ what do they do?

A

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

47
Q

What are Nucleases/ what do they do?

A
  • Break down DNA into nucleotides
  • Nucleotides broken down into nucleosides & nitrogenous bases
  • no example
48
Q

Is a oneway or twoway gut more efficient?

A

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

BIO125 Physiology (17 decks)

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