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Gastrointestinal system And Digestion Flashcards

1
Q

What is the other name for the GI tract?

A

Alimentary tract

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2
Q

What is the GI tract composed of?

A

Mouth and pharynx
Oesophagus
Stomach
Small intestine
Large intestine

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3
Q

What are the accessory organs of the GI tract?

A

Teeth
Tongue
Salivary glands
Liver
Gall bladder
Pancreas

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4
Q

What are the two different types of digestion?

A
  1. Mechanical digestion - chewing mixing and propulsion.
  2. Chemical digestion - large molecules > small molecules. An example - large carbohydrates are broken down by enzymes into glucose.
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5
Q

Give a brief description of how absorption of food occurs.

A
  1. Products of digestion.
  2. Absorbed by epithelial cells in the wall of the gut
  3. Nutrients are transferred to blood vessels.
  4. Nutrients are delivered to tissues.
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6
Q

What are the three different layers in mucosa?

A

Inner layer of epithelium - absorb and secretes function
Lamina propria - made up of connective tissue, blood vessels, supportive.
Muscularis mucosae - inner muscular layer

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7
Q

What are the features of submucosa?

A

It is formed of connective tissue, blood vessels, and some glands.

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8
Q

What type of muscle does the muscularis have? And what is its function?

A

It is a smooth muscle layer

It’s the inner circular layer where the contraction narrows the gut .

The outer longitude layer where contraction shortens the gut .

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9
Q

What is the serosa?

A

Outer layer of the gut

It forms mesentry which is where nerves and blood vessels enter and leave the gut.

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10
Q

Name each layer.

A
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11
Q

What is the function of the mouth (oral or buccal cavity)

A
  1. Food is grounded by the teeth.
  2. Food is mixed with saliva.
  3. Tasting of food.
  4. Food is formed into a bolus for swallowing.
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12
Q

What is the name for when food is being grounded by the teeth?

A

Mastication, which is a form of mechanical digestion.

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13
Q

What is saliva composed of?

A

99.5% water

Digestive enzymes - Amylase and lipase

Mucus , ions, etc.

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14
Q

Define the pharynx

A

The pharynx is found at the back of the mouth and it is a common passage for food and air.

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15
Q

What is deglutition?

A

Swallowing

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16
Q

What is the oesophagus?

A

A collapsible muscular tube about 25 cm

It transports food to the stomach .

It secretes mucus which lubricates and protects.

Food is propelled by the process of peristalsis

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17
Q

What digestive enzymes are found in the oesophagus?

A

None

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18
Q

Does absorption take place in the oesophagus?

A

No

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19
Q

What is peristalsis?

A

The contraction and relaxation of smooth muscle.

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20
Q

What is the role of circular smooth muscle?

A

It contracts behind the bolus and relaxes in front.

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21
Q

What is the role of longitudinal smooth muscle?

A

It contracts in front of the bolus. This shortens the oesophagus.

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22
Q

What is the wave of contraction and how long does it take?

A

It’s propels food

Takes 4 to 8 seconds

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23
Q

What is the role of the lower oesophagus sphincter?

A

It controls the entrance to the stomach

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24
Q

How does the lower oesophagus sphincter control the entrance to the stomach?

A

The ring of smooth muscle tissue is normally contracted but it relaxes during swallowing.

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25
What can sphincter contraction prevent?
Reflux of stomach acid into the oesophagus.
26
What is Gastro oesophageal reflux?
Heartburn
27
What are the four functions of the stomach?
1. Stores food. 2. Mechanical digestion. 3. Chemical digestion. 4. Peristalsis.
28
How does the stomach store food?
Mucosa is arranged in folds called rugae. This allows for the expansion of the stomach.
29
How does mechanical digestion occur in the stomach?
Through waves of smooth muscle contraction. It breaks down food and mixes with digestive juices .
30
How does chemical digestion work in the stomach?
The stomach cells secrete enzymes and hydrochloric acid - gastric juice.
31
How do mechanical and chemical digestion Work in the stomach together?
By breaking down food into a liquid called chyme.
32
What is the role of peristalsis in the stomach?
It pushes chyme into the duodenum.
33
What contains many mucus glands in the stomach?
Cardia
34
What secretes HCL and enzymes in the stomach?
Body and fundus
35
What controls exit from the stomach?
The plyoric sphincter.
36
What is the role of mucous surface cells and mucous neck cells?
They both secrete mucus to protect.
37
What is the role of the parietal cell?
It’s secrete hydrochloric acid and intrinsic factors. This produces an acidic environment.
38
What is the role of a chief cell (zymogenic)?
It secretes pepsinogen and gastric lipase (digestive enzymes)
39
What is the role of the enteroendocrine cell (G cell)
It secretes gastrin. Gastrin stimulates HCl production.
40
Fill in the blanks
41
Describe the pancreas
The pancreas secrete pancreatic juice It is alkaline with a pH of 7.1 to 8.2 This is due to the presence of bicarbonate ions. This buffers acidic chyme
42
What digestive enzymes are found in the pancreas?
Amylase - Digests CHO Trypsin and Chymotrypsin - Digests Proteins Lipase - Digests fats
43
What hormones control the release of the enzymes in the pancreas?
Secretin and Cholecystokinin (CCK)
44
Describe the biliary system
It produces bile. Produced in the liver and stored in the gallbladder .
45
What does bile consist of?
Water Bile salts Bile pigments (bilirubin)
46
What control is the biliary system under?
It is under hormonal control
47
Describe the hormonal control of the biliary system
CCK causes the gallbladder to contract and empty bile into the small intestine. Stimulus is in the duodenum .
48
What is chyme rich in the biliary system.
It is lipid rich as bile assists in the digestion of lipids.
49
What is the function of the small intestine?
It digests and absorbs products and water. Mostly occurring in the first 20%.
50
What is the function of the duodenum?
It mixes chyme with pancreatic and liver secretions.
51
What is the function of the jejunum?
Most digestion and absorption of nutrients takes place here
52
What is the function of the ileum.
It is specialised and absorbs vitamin B12. Spare capacity for absorption of any remaining substances .
53
What are four features of the small intestine?
1. It has a large surface area. 2. It is long - 4.5 to 6.5 m 3. Contains villi - this increases surface area therefore increases absorption. 4. Microvilli (brush border) - microscopic foldings of the surface membrane of the epithelial cells lining the small intestines. This increases surface area even more.
54
What is segmentation?
Mechanical digestion in the small intestine
55
Summarise segmentation
1. It is localised, nonpropulsive movements 2. It mixes chyme with enzymes. 3. Products of digestion are brought into contact with the mucosa.
56
What does the large intestine consist of?
1. Caecum 2. Colon (ascending, transverse, descending, sigmoid) 3. rectum 4. Anus
57
What is the function of the large intestine?
It completes food and water absorption It forms and expel faeces It contains bacteria in the large intestine which produces CO2 , H2, CH4.
58
What is the basic layout of absorption?
Products of digestion > epithelial cells > blood or lymph > tissues
59
Give an example of a polysaccharide breaking down to a di or trisaccharide
Starch > broken down by amylase > sucrose
60
What do di and trisaccharides breakdown to?
Monosaccharides
61
What monosaccharides make maltose?
Glucose + glucose
62
What monosaccharides is sucrose made of?
Glucose + fructose
63
What monosaccharides is lactose made of?
Glucose + galactose
64
What brush border enzyme breaks down maltose?
Maltase
65
What brush border enzyme breaks down sucrose?
Sucrase
66
What brush border enzyme breaks down lactose?
Lactase
67
How are glucose and galactose absorbed?
Absorbed by secondary active transport with sodium ions. BOTH sugar and sodium must bind to the transport protein. REQUIRES ATP
68
How is fructose absorbed?
It is absorbed by carrier mediated, facilitated diffusion. Moves down the concentration gradient (NO ATP)
69
What are proteins broken down into?
Peptides
70
What breaks proteins into peptides?
Pepsin
71
What do peptides break down into?
Amino acids
72
Which pancreatic enzymes breakdown peptides?
Trypsin and chymotrypsin
73
Which brush border enzyme breaks down peptides?
Aminopeptidase
74
How are proteins absorbed?
Amino acids are absorbed by secondary active transport along with sodium ions or hydrogen ions. Some amino acids share the same transport proteins
75
What do triglycerides breakdown into?
Monoglyceride and fatty acids
76
What breaks down triglycerides?
Lipases
77
What type of molecule is a lipid?
Hydrophobic
78
What digestive issues can lipids cause?
Lipids form large droplets which have a small surface area. This results in slow digestion and slow absorption
79
How can digestion and absorption be sped up for lipids?
Bile salts
80
What happens when bile salts react with fat droplets?
Bile salts + gut movement cause emulsification to form smaller droplets. Emulsifying fat droplets give a larger surface area and speeds up digestion .
81
What are the products after lipase has acted on the fat droplets?
Short chain fatty acids (less than 12 carbons) These are absorbed by diffusion
82
How are micelles formed?
Long chain fatty acids and monoglycerides combined with bile salts
83
What property do bile salts have?
They are amphipathic
84
Why are bile salts amphipathic?
This helps them surround the fatty acids and monoglycerides to keep them soluble. This then solubilise fats for digestion.
85
What happens once micelles are formed?
1. Moved to the brush border of the intestinal epithelium. 2. Long chain fatty acids and the mono glycerides diffuse out of the micelle and into the gut epithelial cell. 3. Without bile salts lipid absorption is severely compromised
86
What happens to lipids inside the epithelial cell?
1. The fatty acids and monoglycerides are reformed into triglycerides. 2. Triglycerides combine with cholesterol (apolipoproteins) and proteins to form chylomicrons. 3. Chylomicrons are expelled from the cell by exocytosis and the enter lacteal vessels in the villi.
87
What are lacteals?
Lacteals are lymphatic vessels as associated with the villus which eventually drains back into the blood circulation.
88
Name the structures

Human Physiology (8 decks)

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