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L3 Nutrition > digestive system > Flashcards

digestive system Flashcards

1
Q

digestion

A

the process by which foods are broken down into smaller molecules or nutrients

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2
Q

absorption

A

the uptake of these nutrients and how the body utilises these nutrients to perform a wide range of bodily functions

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3
Q

excretion

A

the way in which the body removes unwanted, unnecessary or harmful substances from the body once it has extracted what it needs

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4
Q

fibrous foods

A
  • cannot be digested or absorbed
  • provide bulk and roughage
  • facilitate the movement of through the digestive tract
  • diets that lack this bulky constituent, increase the risk of constipation and is linked with higher risk of serious things like bowel cancer
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5
Q

mechanical digestion

A
  • first stage of digestive process
  • begins as soon as food enters mouth
  • physical process of chewing = primer for chemical digestion
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6
Q

mechanical digestion relies on the effective action of the following teeth

A
  • incisors = teeth at front of the mouth and are required for biting, scraping and cutting food. healthy human teeth = 8 incisors
  • canines = longest and most stable teeth. more important for piercing and tearing foods
    found in carnivorous animals. healthy human = 4 canines
  • molars = located at back of mouth and are needed to grind larger particles of food into smaller before swallowing
    healthy adults = 12 molars
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7
Q

peristalsis

A
  • a process involved in mechanical digestion
  • accomplished by the action of the smooth muscle tissue found throughout digestive system
  • involuntary action of the smooth muscle tissue that occurs through progressive, wave-like contractions
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8
Q

peristaltic waves

A

occur in oesophagus, stomach and intestines and are essential to ensure the ingested food continues to move through digestive tract

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9
Q

chemical digestion

A
  • initiated by the action of enzymes and starts as soon as food enters the mouth
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10
Q

enzymes in chemical digestion

A
  • enzymes are protein molecules that are produced within the body and are used as catalysts for chemical reactions
  • enzymes accelerate the rate at which reactions
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11
Q

primary enzymes active within the digestive tract

A
  • amylase = responsible for breakdown of carbs
    largely present in saliva but also released in pancreas into small intestine to digest more complex carbs
  • pepsin =
    degrades proteins
    produced by stomach
    trypsin also secreted into pancreas to help this process
  • lipase = breakdowns fats into fatty acids entering the intestines
    water soluble enzyme that is produced in the pancreas but also in smaller quantities in mouth and stomach
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12
Q

the digestive tract

A
  • also called alimentary tract, alimentary canal or gastrointestinal tract
  • describes the internal passage through which ingested food passes from the moment it enters mouth to point it is excreted via anus
  • average human tract is 9 metres long
  • comprised of a series of hollow organs that are joined together by a long, twisting-like tube
  • each of the structures and organs perform a specific digestive role
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13
Q

transit time

A
  • the time it takes for food to pass through the digestive tract
  • in a healthy adult the average transit time is between 24 and 72 hours
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14
Q

3 functions of saliva

A

1) moistens food so tongue can roll it into manageable sized balls in prep for swallowing = bolus
2) starts carb digestion (contains amylase)
3) mixes antibodies into the foods to kill bacteria that may be present in the food consumed

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15
Q

the tongue

A
  • responsible for churning and mixing food in mouth
  • this actions stimulates the release of saliva and chemical breakdown of foods
  • has taste buds at back of tongue
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16
Q

time food takes in mouth

A

each mouthful takes about 30-60 seconds to chew and swallow depending on the type of food and the speed it is chewed

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17
Q

pharynx

A
  • throat
  • has both respiratory and digestive functions
  • forms the passageway connecting the mouth and nose to the oesophagus and larynx
  • consists of 3 different muscles
  • primary structure for swallowing
  • swallowing action = reflex ~ lasts 1-3 seconds
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18
Q

oesophagus

A
  • about 10 inches long
  • connects throat to stomach
  • runs parallel to trachea
  • protected at the top by a small flap of cartilage called ‘epiglottis’
  • food moves down oesophagus into stomach using peristalsis to prevent any reflux in mouth
  • with a medium sized bolus, it takes 5-8 seconds to deliver food to stomach
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19
Q

stomach

A
  • J shaped organ
  • can expand up to 8 times its size after food
  • located just left to the centre of the chest area, immediately below sternum
  • internal structure has 3 different layers of tissue that are arranged into deep muscular folds
  • these folds enable the stomach to blend and churn the ingested food
  • food is digested both mechanically and chemically here
20
Q

chyme

A

a thick liquid created by the peristaltic action of the stomach’s lining mixing gastric juices into the food

21
Q

hydrochloric acid

A
  • contained in the gastric juices
  • helps to kill bacteria
  • so potent it can dissolve metal so the stomach is lined with thick layer of mucus to stop it from digesting itseld
22
Q

pepsin (enzyme)

A
  • contained in gastric juices
  • breaks down any protein in food
  • can only work in very acidic conditions
23
Q

alcohol and the stomach

A
  • alcohol is absorbed in the stomach
  • which is why it enters bloodstream very quickly
  • it is the only substance that is directly absorbed in the stomach
24
Q

emptying of stomach

A
  • takes about 3-4 hours depending on types of foods consumed, hydration status and physical activity levels
25
Q

pancreas

A
  • long flattened gland
  • located deep in the abdomen
  • adjacent to stomach and small intestine
26
Q

functions of the pancreas

A
  • producing and releasing enzymes responsible for digestion ~ e.g. trypsin and lipase
  • create and release blood regulating hormones
  • produces large quantities of bicarbonate which neutralises high acidic contents of stomach
27
Q

gall bladder

A
  • 4 inch pear shaped organ
  • located below the liver in upper-right section of abdomen
  • stores the bile produced by the liver
  • delivers bile to the small intestine via bile ducts
28
Q

bile

A
  • largely made from acids, salts, cholesterol and water
  • emulsifies and disperses fats as they move from stomach to small intestine ~ this allows fat-soluble vitamins and other nutrients to be easily absorbed into bloodstream
29
Q

liver

A
  • largest glandular organ
  • located to the right of the abdominal cavity and just beneath diaphragm
  • weighs about 3lbs
  • not directly involved in digestion of specific nutrients
  • first organ to be nourished and replenished with nutrients, but also means any toxins like alcohol/drugs, the liver has to detoxify to prevent cellular damage
30
Q

functions of the liver

A
  • storage of carbs in form of glycogen
  • hormone production
  • blending and emulsification of fats
  • excretion of old blood cells
  • production of bile for storage in the gall bladder
  • production of cholesterol
  • filters and neutralisers toxins
  • storage of some vitamins and iron
31
Q

small intestine

A
  • longest of the intestinal tracts
  • about 5-6 metres
  • sometimes called small bowel
  • takes about 3-4 hours for food to pass through
32
Q

small intestine can be divided into 3 sections

A
  • duodenum
  • jejunum
  • ileum
33
Q

duodenum

A
  • first section of small intestine
  • about 10 inches long
  • adjacent to pancreas
  • here the pancreas secretes enzyme trypsin to further digest protein
34
Q

jejunum

A
  • second and longest section of the small intestine
  • between 2-3 metres in length
  • where most of the absorption of nutrients takes place
  • the internal structure is a series of hair like structures called cilia
35
Q

cilia

A
  • provide a large surface area that enables absorption to occur at a much greater rate
  • nourished with a rich blood supply from capillaries, and from lymphatic structures called lacteals
36
Q

lacteals vs capillaries

A

lacteals are more permeable than capillaries so they enable larger molecules, particularly fats to pass through their walls = facilitates absorption of fats in jejunum

37
Q

ileum

A
  • final stage of small intestine
  • about 3-4 cm
  • here any remaining nutrients are absorbed, particularly bile salts and vitamins
38
Q

large intestine

A
  • final stage of digestive journey
  • where waste is excreted
  • about 1.5 metres
39
Q

functions of large intestine

A
  • reabsorb water from remaining matter

- manufacture vitamins B and K and start the process of excretion

40
Q

the 3 sections of the large intestine

A
  • caecum
  • colon
  • rectum
41
Q

caecum

A
  • first stage of large intestine
  • receives chyme from ileum of small intestine
  • ascends from lower right hip region where it joins colon
  • primary function is to absorb fluid and salts from remaining matter and to help solidify it before excretion
42
Q

appendix

A
  • immediately below the caecum
  • hollow, sac-like structure
  • connected to lower portion of the caecum
  • exact function is unclear
  • called the redundant organ
43
Q

colon

A
  • largest section of the large intestine
  • has 3 sections which are named according to the direction they carry waste = ascending colon, transverse colon, descending colon
  • primary function is to reabsorb water and to store the waste before it is excreted
44
Q

rectum

A
  • final section of large intestine
  • about 8 inches
  • serves as a place for storing waste before excreted as faeces
  • also compresses waste into solid form
  • when faecal matter starts to accumulate, the rectum wall is stretched and initiates the sensation of needing to go to the toilet
  • waste is passed through the anus
  • residence time for waste in colon ranges from 4-72 hours - av. time being 36 hours before it is excreted
45
Q

summarised journey of digestive tract

A

1) mouth
2) oesophagus
3) stomach
4) duodenum
5) jejunum
6) ileum
7) colon
8) rectum
9) anus

L3 Nutrition (14 decks)

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