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bio ‘24 > digestive system > Flashcards

digestive system Flashcards

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1
Q

Digestion

A

Digestion is the process that breaks down complex food substances into simple, soluble molecules that are small enough to be absorbed into the body cells

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2
Q

Physical digestion

A

Mechanical breakdown of good into smaller particles to provide a large surface area to volume ratio for faster rate of chemical digestion by digestive enzymes

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3
Q

Chemical digestion

A

Breakdown of large food molecules into small soluble molecules catalysed by digestive enzymes through hydrolytic reactions

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4
Q

Digestion in the mouth

A
  • The act of taking food into the mouth is called ingestion
  • chewing breaks down the food into pieces to increase SA: V for faster rate of chemical digestion by digestive enzymes
  • saliva, produced by the salivary glands in the mouth, would moisten and soften food
  • it also contains the enzyme salivary amylase which digests starch into maltose
  • the throughly chewed food is rolled into a bolus in preparation for swallowing
  • after swallowing, the bolus enters the oesophagus. The digestion of starch continues in the oesophagus
  • the bolus is moved along the oesophagus by peristalsis, a rhythmic, wave like muscular contractions of the wall towards the stomach. Peristalsis occurs throughout the alimentary canal.
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5
Q

Digestion in the stomach

A
  • The stomach is an elastic, muscular bag, with thick muscular walls
  • in the presence of food, gastric glands in the stomach will secrete gastric juice
  • the gastric juice consists of mainly hydrochloric acid and the enzyme pepsin
  • food is churned and mixed with the gastric juice by the peristaltic contractions of the stomach wall for hours
  • the partly digested food becomes liquified, forming chyme, which passes into the duodenum in small amounts
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6
Q

Gastric juice- hydrochloric acid

A
  • Provide an acidic medium suitable for the action of the enzymes in the stomach
  • kills bacteria in food
  • changes inactive forms of enzymes to the active forms: converts pepsinogen to pepsin
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7
Q

Gastric juice- pepsin

A

Pepsin digests proteins to polypeptides by hydrolysis

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8
Q

Digestion in small intestine

A
  • The small intestine consists of the duodenum, jejunum and highly coiled ileum
  • the lining of the walls of the small intestine contains glands which secrete digestive enzymes
  • the duodenum, the first part of the small intestine, receives chyme from the stomach and secretions from the gall bladder and pancreas
  • small intestine secretes intestinal juice which contains digestive enzymes needed to complete the digestion of carbohydrates, proteins and fats
  • at the end of the digestive process, all carbohydrates are digested into monosaccharides such as glucose, fructose and galactose
  • polypeptides are digested into amino acids
  • fats are digested into fatty acids and glycerol
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9
Q

liver - bile

A

liver produces bile
- bile emulsifies fats, physically break down fats into tiny fat droplets to increase SA:V for faster digestion by lipase
- does not contain any digestive enzymes
- creates an alkaline environment for enzymes action and to reduce the acidity of the chyme
- bile enters the duodenum via the bile duct

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10
Q

pancreas

A

pancreas secretes pancreatic juice containing: pancreatic amylase, pancreatic lipase, trypsin
- pancreatic juice is secreted into the duodenum by the pancreas via pancreatic duct

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11
Q

liver, gall bladder and pancreas

A
  • the liver, gall bladder and pancreas are not part of the alimentary canal but are associated with it
  • the pancreas is a gland lying below the stomach which produces several digestive enzymes
  • the liver is the largest gland that produces bile. bile is an alkaline greenish-yellow liquid containing bile salts and bile pigments. bile is stored in the gall bladder
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12
Q

absorption in small intestine

A
  • products of digestion such as monosaccharides, amino acids, fatty acids, glycerol and water are absorbed throughout the small intestine, especially the ileum
  • these products must be transported across the epithelium into the blood stream.
  • glucose and amino acids enter via facilitated diffusion and active transport
  • fatty acids and glycerol diffuse into the epithelial cells and recombine to form minute rat globules, before diffusing into the lacteal
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13
Q

adaptations of the small intestine for absorption - long

A

small intestine is long
- to provide sufficient time for absorption to take place

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14
Q

adaptations of the small intestine for absorption - folds

A

inner walls of the small intestine have many transverse folds bearing many finger-like projections called villi. each villus possesses the numerous microvilli.
- to increase SA:V for faster absorption of digested food substances by diffusion

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15
Q

adaptations of small intestine for absorption- epithelium

A

the epithelium of the villus is one cell thick
- to reduce the distance for digested products to diffuse into the capillaries and lacteal

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16
Q

adaptations of small intestine for absorption - blood capillaries

A

the small intestine consists of a dense network of blood capillaries and lacteal within the villi
- the continuous transport of absorbed food substances by the capillaries and lacteal, away from the small intestine, maintains a steep concentration gradient for faster absorption of digested products by diffusion

17
Q

absorption of digested products and water

A
  • glucose and amino acids are absorbed by facilitated diffusion into the blood capillaries of the villi
  • they are also absorbed by active transport when there is a lower concentration in the intestinal lumen than in the blood capillaries
  • fatty acids and glycerol diffuse into the epithelial cells and recombine to form minute fat globules before diffusing into the lacteal
  • most water and minerals are absorbed in the large intestine
  • blood capillaries of the small intestine join to form venules which then join to form the hepatic portal vein. hepatic portal vein carries mainly glucose and amino acids to the liver to be processed
  • fat globules are transported away from the small intestine by the lacteals
18
Q

Assimilation of absorbed nutrients

A

Assimilation is the utilization of absorbed nutrients and how the body deals with the excess nutrients

19
Q

Assimilation of glucose

A
  • Glucose is a substrate for respiration to release energy for cellular activities
  • excess glucose is converted into glycogen by the liver cells and stored. This is stimulated by insulin, produced by the pancreas
  • glycogen is converted into glucose by the liver cells when blood glucose level is low. This is stimulated by glucagon, produced by the pancreas
20
Q

Assimilation of amino acids

A
  • Required to make new cell materials that is used for growth and repair of worn- out parts of the body
  • required to make enzymes and hormones
  • excess amino acids are deaminated in the liver, their amino group is removed and converted into urea
21
Q

Assimilation of lipids

A
  • required in the production of cell membranes
  • required in the production of steroid hormones
  • fats are required to serve as cushioning to protect vital organs such as the heart and kidneys
  • when there is inadequate supply of glucose, fats will be oxidized in the liver to provide energy
  • excess fats are stored in adipose tissues under the skin: in adipose cells, fat droplets can collect in the cytoplasm and their fat droplets increase in size and number to form one large globule of fat in the middle of cell, pushing the cytoplasm into a thin layer and nucleus to one side. Groups of fat cells form adipose tissue.
22
Q

Large intestine (process after small infective)

A
  • After absorption of the nutrients in the small intestine, the undigested and unabsorbed matter enters the large intestine
  • the undirected and unabsorbed matter consists of a mixture of water, bile pigments, dead cells from intestinal lining, dead and live bacteria and mainly cellulose from plant cells
  • the movement of undigested materials along the large intestine is by peristalsis
  • the large intestine absorbs minerals and any remaining water into the blood stream
  • absorption of water from the undigested remains in the large intestine results in the formation of faeces
  • the walls of the large intestine secrete mucus which helps to bind the faeces along the large intestine
23
Q

Rectum and anus

A
  • Faeces is temporarily stored in the rectum and as it accumulates, pressure in the rectum increases, causing a ‘desire’ to expel the faeces through the anus
  • when the rectum is full, the muscles of the rectal wall contract to egest the faeces
  • the passing out of faeces via the anus from the body is known as defecation/egestion
24
Q

Functions of the liver - bile production

A
  • Liver produces bile
  • bile emulsifies lipids to increase the surface area to volume ratio of the lipids for lipase to act on
  • bile is stored temporarily in the gall bladder before use
25
Q

Functions of the liver- regulation of blood glucose

A
  • after a meal, blood glucose concentration increases
  • insulin stimulates the liver cells to convert excess glucose into glycogen for storage
  • during fasting or after a long time after a meal, blood glucose concentration decreases
  • glucagon stimulates the liver calls to break down glycogen to glucose to be released into the bloodstream
26
Q

Functions of the liver-deamination of excess amino acids

A
  • Excess amino acids cannot be stored by the body and must be deaminated
  • amino groups are removed and converted into urea which will be removed by the kidneys
  • carbon residues of the deaminated amino acids are converted into glucose
27
Q

Functions of the liver-breakdown of hormones

A
  • The liver breaks down hormones when they are no longer required by the body
28
Q

Functions of the liver - detoxification

A
  • Liver cells convert harmful substances into harmless ones-detoxification
  • alcohol is broken down in the liver and then removed from the body system
    -Hydrogen peroxide is a toxic by-product of cellular activities. it is broken down into water and oxygen by the enzyme catalase in the liver cells.

bio ‘24 (8 decks)

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