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Level 2 Science > Human Digestive System > Flashcards

Human Digestive System Flashcards

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1
Q

what is nutrition?

A

intake of food and the processes that convert food substances into living matter

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2
Q

what does nutrition comprise of? (5 points)

A

ingestion: intake of food into body

digestion: large food molecules broken down/hydrolysed into smaller and soluble molecules

absorption: digested food molecules taken into body cells

assimilation: body cells make use of (assimilate) absorped food molecules

egestion: removal of undigested matter from body

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3
Q

why is digestion necessary? (3 points)

A

food molecules are mostly insoluble in water

food molecules too large to pass through gut wall into bloodstream

helps break down large food molecules into smaller and soluble molecules

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4
Q

why is the digestive system important?

A

enables us to use nutrients in food

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5
Q

what is the physical digestion in the mouth? (2 points)

A

teeth cut and grind food (chewing), making it easier to swallow

increases surface area to volume ratio so enzymes can act on food more efficiently

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6
Q

what is the chemical digestion in the mouth?

A

presence of food in mouth triggers a reflex that causes salivary glands to secrete saliva

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7
Q

what are the constituents of saliva? (3 parts)

A

mucin (protein): protects soft lining of mouth from abrasion or and lubricates food for swallowing

antibacterial agents: kills many of the bacteria that enter the mouth with food

salivary amylase (enzyme): breaks down/digests starch to maltose

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8
Q

what is the purpose of the pharynx?

A

connects buccal cavity to oesophagus and larynx

(also connects to trachea)

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9
Q

what is the oesophagus?

A

long, narrow, muscular tube that extends to the stomach

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10
Q

what is the purpose of the oesophagus?

A

conducts food from pharynx down to the stomach by peristalsis (no digestion occurs in oesophagus)

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11
Q

what is the oesophagus made up of?

A

circular muscles (inner)
longitudinal muscle (outer)

^ antagonistic muscles (when one contracts, the other relaxes)

circular — contract, longitudinal — relax (wall constricts, inwards)
circular — relax, longitudinal — contract (wall dilates, outwards)

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12
Q

what is peristalsis?

A

rhythmic, wave-like contractions (happens throughout alimentary canal)

2 sets of muscles work antagonistically (when one contracts, the other relaxes)

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13
Q

what is the stomach lined with?

A

gastric glands that secrete gastric juices

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14
Q

what is the physical digestion in the stomach?

A

churning action (peristalsis) by smooth muscles of stomach mixes food with gastric juice into chyme

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15
Q

what does gastric juice contain?

A

dilute solution of hydrochloric acid (pH 2) and protease (pepsin)

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16
Q

what happens with the gastric juice and food in the stomach? (4 points)

A

kills most harmful bacteria/microorganisms swallowed with food

provides acidic environment for enzymes (pepsinogen to pepsin) to work (optimum pH 2)

stops (denatures) action of salivary amylase (optimum pH 7)

protease breaks down/digests proteins into polypeptides

17
Q

why is the stomach protected by a layer of mucus?

A

prevents stomach lining from being damaged by acid

18
Q

what is the small intestine? (2 points)

A

consists of U-shaped duodenum and much-coiled ileum

where most digestion of large food molecules occur

19
Q

what is the process of digestion and absorption in the small intestine? (4 points)

A

chyme released from stomach into duodenum

intestinal glands secrete intestinal juice

pancreas secretes pancreatic juice

liver cells produce and secrete bile, stored in gallbladder, flows into duodenum via bile duct

20
Q

what is bile and its purpose?

A

alkaline greenish-yellow liquid produced by liver, an emulsifier (not enzyme, no optimum pH/temperature)

emulsifies fats by breaking up large fat droplets into tiny fat droplets so that surface area to volume ratio of fats increased to speed up digestion by pancreatic and intestinal lipases (emulsification)

(physical digestion)

21
Q

what does pancreatic juice contain? (3 enzymes)

A

pancreatic amylase (remaining starch —> maltose)
pancreatic lipase (lipids —> glycerol + fatty acids)
protease (proteins —> polypeptides)

22
Q

what does intestinal juice contain? (3 enzymes)

A

other carbohydrases (digests double sugars to single sugars), maltase (maltose —> glucose), sucrase (sucrose —> glucose + fructose)
other protease (polypeptides —> amino acids)
intestinal lipase (lipids —> glycerol + fatty acids)

23
Q

what is the fuction of the ileum?

A

absorps nutrients and water

24
Q

what are the functions of the large intestine? (2 points)

A

absorps water and mineral salts into blood

undigested matter temorarily stored in rectum, discharged through anus (egestion/defecation)

25
Q

what are villi? (3 points)

A

small intestine lined with many small finger-like projections to increase surface area for absorption of nutrients

thin walls (1 cell thick)

have many capillaries to transport absorped nutrients away

26
Q

how are absorped nutrients transported?

A

after absorption, blood capillaries rich in simple sugars and amino acids

blood capillaries join into larger blood vessels

larger blood vessels unite into hepatic portal vein (delivers nutrient-rich blood from gut to liver for assimilation)

27
Q

what is the use of glucose? (2 points)

A

substrate for cellular respiration

excess stored as glycogen in liver and muscles of animals

28
Q

what is the use of amino acids? (2 points)

A

used in cells for synthesis of tissue proteins

used in cells for sysnthesis of other substances such as enzymes and hormones

29
Q

what is the use of fats? (3 points)

A

formation of cell membranes

excess stored in adipose tissue under skin or surrounding organs

fats broken down to provide energy in certain conditions (starvation, fasting)

30
Q

why do diabetes occur?

A

body produces insufficient insulin (hormone that keeps blood sugar level balanced), or does not respond properly to insulin, resulting in high amount of sugar in the blood

31
Q

describe the 2 types of diabetes

A

type 1: inherited and cannot be prevented

type 2: most common type, can be prevented

32
Q

how to prevent diabetes? (4 points)

A

eat in moderation (more fruits and vegetables, less sugar and saturated fat)

at least 150min of physical activity weekly

prevent weight gain (exercise regularly, control calorie intake)

avoid smoking and reduce alcohol intake

Level 2 Science (15 decks)

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