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Anatomy and Physiology 2 > Gastrointestinal System > Flashcards

Gastrointestinal System Flashcards

1
Q

What is digestion important for?

A

Digestion is important for breaking down food into nutrients, which the body uses for energy, growth and cell repair.

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2
Q

How are nutrients absorbed?

A

Nutrients are absorbed by the blood which carries them to cells in the body.

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3
Q

Describe the digestive process:

A
  • Chewing in the mouth breaks down food
  • Food mixes with digestive juices breaking down molecules
  • Small molecules absorbed through wall of small intestine into bloodstream
  • Bloodstream delivers molecules to the body
  • Waste passes through large intestine and out of the body as solid matter
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4
Q

How do hormones regulate digestion?

A

Cells in the lining of the stomach and intestine produce and release hormones that stimulate production of digestive juices and regulate appetite.

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5
Q

How do extrinsic nerves regulate digestion?

A

Extrinsic (outside) nerves connect the digestive organs to the brain and spinal cord causing the gastrointestinal system to contract or relax depending on if there is food to digest.

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6
Q

How do intrinsic nerves regulate digestion?

A

Intrinsic (inside) nerves are triggered when food stretches the walls of the gastrointestinal tract which releases different substances that speed up or slow down the digestive process.

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7
Q

Functions of the mouth:

A

Food enters the mouth and is ground by the teeth (mechanical digestion) and mixed with saliva, containing salivary amylase before being swallowed.

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8
Q

What are the three phases of swallowing?

A 
Oral phase (voluntary)
Pharyngeal phase (involuntary)
Esophageal phase (involuntary)
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9
Q

Functions of saliva:

A
  • Aids digestion
  • Breaks down food
  • Keeps the mouth clean by washing away bacteria and food particles
  • Lack of saliva increases dental cavities, causes mouth soreness and reduces ability to taste.
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10
Q

Where is saliva produced?

A
  • parotid gland
  • sublingual gland
  • submandibular gland
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11
Q

Describe the pharynx:

A
  • Extends from the back of the mouth to oesophagus
  • Food passes from oropharynx to laryngopharynx
  • Muscles in the pharynx wall contract during swallowing
  • The epiglottis closes the larynx protecting the trachea from obstruction
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12
Q

What is the oesophagus?

A

The oesophagus is a muscular tube from the mouth to the stomach (25cm long)

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13
Q

In the oesophagus, what is transport of food supported by?

A

Transport of food is supported by involuntary muscles and two sphincter’s. As food approaches the sphincter, it relaxes allowing food to pass.

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14
Q

Name the two sphincter’s:

A

Oesophageal and cardiac

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15
Q

How does food pass down the oesophagus?

A

By peristalsis and mucus is secreted lubricating the food.

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16
Q

What is peristalsis?

A

Waves of muscular contraction and relaxation in the walls of the gastrointestinal tract which squeezes food along and mixes it.

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17
Q

What is the role of the stomach?

A
  • Stores swallowed food and liquids

- Digested food is slowly emptied into the small intestine

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18
Q

Name the two openings of the stomach:

A

Oesophageal and duodenal

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19
Q

Name the four regions of the stomach:

A
  • Cardia: produces digestive juices
  • Fundus: collects digestive gases
  • Body: secretes pepsinogen and hydrochloric acid
  • Pylorus: produces gastrin, pepsinogen and mucus
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20
Q

Five functions of the stomach?

A
  • temporary storage of food
  • controls rate of food entering the duodenum
  • acid secretion and antibacterial action
  • fluidisation of stomach contents
  • preparing for digestion with pepsin and lipase
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21
Q

What are the three muscle layers to mix and breakdown food?

A
  • Longitudinal layer
  • Circular layer
  • Oblique layer
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22
Q

Features of the stomach:

A
  • The mucosa membrane lining of the stomach has folds called rugae, enabling expansion when full
  • 2-3 litres of gastric juice is produced daily (reabsorped in intestine)
  • pH of gastric juice - 1.5-2, very acidic, kills most pathogens
  • Intrinsic factors enable B12 to be absorbed by intestine
  • Food in the stomach is broken down mechanically (muscular activity) and chemically (enzyme activity)
  • The food is converted to chyme which is delivered to the duodenum via the pyloric sphincter
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23
Q

What are enzymes?

A

Catalysts that speed up a chemical reaction without undergoing alteration

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24
Q

What enzymes are in the stomach?

A

Pepsin - starts the breakdown of protein, released as pepsinogen
Gastric lipase - starts the breakdown of fat
Rennin - acts of milk products in children

25
Q

Role of the small intestine:

A

Muscles mix food with digestive juice from pancreas, liver and intestine and push food further to aid digestion.

26
Q

How are nutrients absorbed through the small intestine?

A

Walls absorb the digested nutrients into the bloodstream. Blood delivers these nutrients to the rest of the body.

27
Q

Three parts of the small intestine:

A

Duodenum
Jujunum
Ileum

28
Q

Features of the small intestine:

A
  • the site where most chemical and mechanical digestion takes place
  • lined with absorptive mucosa
  • smooth muscle wall for peristalsis
29
Q

Functions of the small intestine:

A
  • Completion of chemical digestion
  • Bile emulsifies fat
  • Duodenum receives pancreatic enzymes from pancreas and bile from the liver and gall bladder. These break down molecules.
  • Major site of absorption of nutrients into blood due to large surface
  • Onward movement of non-digested or absorbed contents to the large intestine via the ileocecal valve
  • Absorption aided by villi, tiny protrusions in small intestine wall that have a large surface area to allow easier absorption by diffusion
30
Q

Describe the duodenum:

A
  • First section of the small intestine (25cm long)
  • A duct enters the duodenum delivering bile from the liver and pancreatic juice from the pancreas: the hepatopancreatic ampulla
31
Q

Accessory organs of the duodenum:

A

Liver, gall bladder and pancreas

32
Q

Role of the jujunum and ileum:

A
  • Chyme continues to move through the small intestine through peristalsis then moves into the large intestine through the ileocecal valve
33
Q

Features of the small intestine:

A
  • 90% of nutrients absorbed in small intestine
  • Villi increase surface area for absorption
  • Glands between villi release brush border enzymes
34
Q

Function of the liver:

A

Produces bile

35
Q

Function of the gall bladder:

A

Stores bile

36
Q

When does the gall bladder release bile?

A

When fatty chyme enters the duodenum

37
Q

What is the function of bile?

A

Bile emulsifies fat into smaller molecules which increases surface area for digestive enzymes to work on

38
Q

What is the pH of bile?

A

Bile is alkaline as it is rich in bicarbonate enzymes

39
Q

Describe the role of the pancreas:

A

Consists of exocrine glands that secrete digestive enzymes such as lipase, peptidase and amylase.

40
Q

How are pancreatic enzymes secreted?

A

Pancreatic enzymes are secreted into the duodenum via the duodenal ampulla.

41
Q

How is pancreatic excretion controlled?

A

By hormones (cholecystokinin)

42
Q

Role of pancreatic juice and bile:

A

Pancreatic juice and bile neutralise acidic chyme due to their alkaline nature so that amylase and lipase can function more effectively.

43
Q

Features of the large intestine:

A
  • 1.5m long
  • No villi or digestive enzymes as nutrients have already been absorbed in the small intestine
  • Bacteria colonise the colon, ferment indigestible carbs and synthesise vitamin B and K
  • Mostly water, some electrolytes and Vitamin B and K absorbed into the bloodstream
44
Q

What are mass movements?

A

A long, slow moving peristalsis occurring 3-4 times a day to move food into the rectum

45
Q

What does faeces contain?

A

Faeces contains undigested food residues, mucus, sloughed off epithelial cells, millions of bacteria and enough water to allow smooth passage.

46
Q

Describe the process of defaecation:

A
  • Stretch receptors in the rectal wall sense the distention of the rectal walls
  • Information is sent to spinal nerves which is then sent back to the rectal walls to allow them to contract and the anal sphincter to relax
  • Faeces is forced into the anal canal through the internal sphincter then voluntary control of the external sphincter allows for defaecation via the anus
47
Q

Where in your diet can you get carbohydrates from?

A
  • Mostly from plants
  • Lactose from milk
  • Small amount of glycogen form milk
  • Sugar from fruits, sugar and milk
48
Q

Describe the breakdown process of carbohydrates:

A
  • Salivary amylase: polysaccharides (starch) to disaccharides (sucrose, maltose, lactose)
  • No breakdown in the stomach due to low pH
  • Pancreatic amylase in small intestine: further breakdown of polysaccharides to disaccharides
  • Brush border enzymes (maltase, lactase, sucrase) in the small intestine breakdown disaccharides to monosaccharides (glucose, fructose, galactose)
49
Q

Where in your diet can you get lipids from?

A
  • Saturated fat: animal fat
  • Unsaturated fat: seeds, nuts and vegetable oil
  • Cholesterol: egg yolks and milk products
50
Q

Describe the breakdown process of lipids:

A
  • Limited breakdown in the stomach, however, lipase in stomach starts digestion of triglycerides (optimum pH 5-6)
  • Bile emulsifies fats to increase surface area allowing pancreatic lipase to breakdown triglycerides to fatty acids and glycerol.
51
Q

How many minerals does the body require?

A

7 - calcium, potassium, phosphorus, sulphur, sodium, chloride and magnesium

52
Q

Where in your diet can you get minerals from?

A

Veg, meat and milk

53
Q

Function of vitamins in the body:

A

Most vitamins function as co-enzymes and work with an enzyme to produce a reaction

54
Q

Types of proteins:

A
  • Complete proteins: provide all the bodies amino acid requirements for tissue growth and maintenance
  • Incomplete proteins: lack one or more type of amino acid (provide all essential amino acids when combined)
55
Q

Where in your diet can you get proteins from?

A
  • Complete proteins: egg, meat, milk

- Incomplete proteins legumes, nuts, cereals

56
Q

Describe the breakdown process of proteins:

A
  • Pepsin in stomach breaks down larger polypeptides
  • Chymotrypsin/trypsin in pancreatic juice breaks down smaller polypeptides in the small intestine
  • Brush border enzymes (peptidases) break down smaller peptides into amino acids
57
Q

Describe the absorption of nutrients:

A
  • Nutrients, once broken down, can be absorbed through the walls of villi and enter the blood
58
Q

How are the different food groups absorbed as nutrients?

A
  • Proteins as amino acids
  • Carbohydrates as simple sugars (glucose, fructose, galactose)
  • Fats as glycerol: absorbed into lymphatic capillaries as fatty acids
59
Q

Once absorbed, where are nutrients carried?

A
  • The bloodstream carries simple sugars, amino acids, glycerol, some vitamins and salts to the liver
  • The lymphatic system absorbs fatty acids and vitamins

Anatomy and Physiology 2 (5 decks)

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