Digestion and Absorption 1 Flashcards
(112 cards)
1
Q
What are the General Functions of the GI Tract
A
Digestion- physical and Chemical Secretion Expulsion Protection (immune system) Motility Storage Absorption- the ultimate goal as needed for growth and repair
2
Q
Physical Processes of Digestion
A
Chewing, peristalsis, segmentation
3
Q
What is Peristalsis
A
The wavelike, rhythimic muscular contractions of the GI tract that move chyme down its tract
4
Q
Which muscles are involved in peristalsis
A
Circular muscles which give alternating waves of contraction
5
Q
What is segmentation
A
Periodic squeezing and partitioning of the SI which mixes the chyme and promotes close contact with digestive juices and absorbing cells
6
Q
Which muscles are involved in segmentation
A
Longitudinal muscles which move materials back and forth to aid in mixing
7
Q
Extrinsic control of GI tract
A
Sympathetic and parasympathetic nerves (vagus nerve in PS which is stimulated by smell, sight and taste of food)
8
Q
Intrinsic control of GI tract
A
The enteric nervous system made up of the myenteric plexus and submucosal plexus
9
Q
Role of the myenteric plexus
A
Largely motor in fucntion
10
Q
Role of the submucosal plexus
A
Largely sensory in function
11
Q
What is chemical digestion aided by
A
Digestive enzymes
12
Q
What is chemical digestion regulated by
A
Hormones
13
Q
What substances make up intestinal secretion
A
Enzymes, acid, base, bile, mucus
14
Q
What are enzymes
A
Protein compounds which catalyse hydrolysis but are not altered in the process. They are compatible with a specific compound or nutrient, each has an optimal pH range and each has an optimal temperature
15
Q
What type of acid is found where
A
HCl is found in the stomach
16
Q
What type of base is found where
A
Bicarbonate is found in the small intestine
17
Q
Where is bile produced
A
Liver
18
Q
Where is bile stored
A
Gall bladder
19
Q
What is hydrolysis
A
The cleavage of chemical bonds by the addition of water
20
Q
What are proteins broken down into
A
Amino acids
21
Q
What are carbohydrates broken down into
A
Monosaccharides
22
Q
What are fats broken down into
A
Monoglycerides and free fatty acids
23
Q
What is pH
A
The concentration of hydrogen ions in solution. The more H+ ions the more acidic, conversely the more OH- ions the more basic. Each enzyme functions best within a certain pH range.
24
Q
Where does digestion occur
A
Mouth, stomach, small intestine, large intestine.
25
What is the role of teeth
Physical digestion
26
What is the role of saliva
Chemical digestion
27
What is the role of amylase
To break down starch into small sugar molecules (5%)
28
What is the role of lingual lipase
To break down fats, however this only happens in minuscule amounts
29
Where is lingual lipase secreted
von Ebner's glands
30
Which enzymes are secreted in the mouth
Amylase and lingual lipase
31
What is found in gastric juice
Water, HCl, enzymes, hormones, intrinsic factor (B12) and rennin.
32
Which cells secrete HCl and where are they found
Parietal cells in the gastric pit
33
Where is mucus secreted and what is its function
Secreted near the cells and is an alkaline substance and so protects the stomach wall
34
Which enzymes are present in the stomach?
Pepsin and gastric lipase
35
Which cells secrete the stomach enyzmes
Chief cells
36
What is pepsinogen
An inactive form of the enzyme pepsin
37
What are the 3 roles of hydrochloric acid
To break down the connective tissue or muscles in meat.
To activate pepsinogen to form pepsin.
To act as a defence mechanism in killing micro-organisms
38
What is the role of rennin
To coagulate milk enabling the access of nutrients
39
Rennin is found in adults- true or false
False, it is important in newborns and isn't found in adults
40
What substances are absorbed in the stomach
Only some lipid-soluble compounds and weak acids such as alcohol and asprin
41
What is found in the stomach
Gastric juice, mucus
42
What enters the small intestine
Chyme
43
What are the three parts of the small intestine
Duodenum, jejunum and ileum
44
How long is the duodenum
10-12 inches
45
How long is the jejunum
~4 feet
46
How long is the ileum
~5 feet
47
What features of the small intestine increase surface area
Circular folds -> villi -> microvilli
48
What cells in the small intestine secrete fluid, and how much is secreted each day
Intestinal crypst cells secrete 1-2L of fluid each day
49
What stimulates the intestinal crypst cells
Distension, chyme, vagal nerve activity, hormones
50
What does the brunners glad in the SI secrete and what is the purpose of the secretion
The brunners glad secrete a bicarbonate rich fluid which neutralises chyme
51
What do goblet cells in the SI do
Secrete mucus
52
Which accessory organs does the SI need for digestion
Liver and pancreas
53
Which three substances are digested in the SI
Protein, fat and carbohydrate
54
What is role of bile
To emulsify fats and so break down fats into smaller fat goblets, increasing the surface area of fats. The increased surface area enhances enzyme breakdown of fats
55
What is the function of bile salts
To attach to fat goblets making them hydrophilic (water soluble).
56
What is bile made up of
Bile salts, bile pigment, cholesterol, phospholipids,, electrolytes.
57
Which part of the SI is the site of pancreatic secretion
The duodenum
58
Which pancreatic enzymes are secreted in the SI
```
Pancreatic amylases (carbohydrates).
Pancreatic lipase (fats).
Trypsin, chymoptrypsin and carboxypeptidase (proteins).
```
59
What is present in pancreatic secretions secreted in the SI
Pancreatic enzymes and bicarbonate
60
What is the role of bicarbonate in the SI
To neutralise HCl from the stomach
61
What does the conversion (joining) of the common bile duct and pancreatic duct result in
The release of pancreatic zymogens
62
What are zymogens
Inactive forms of enyzmes
63
Where are brush border enzymes secreted from
Enterocytes
64
What is the function of brush border enzymes
To break the double bonds in sugars to form simple sugars
65
Name 3 brush border enzymes found in adults
Sucrase, isomaltase, lactase
66
Name a brush border enzyme only found in people less than 4 years old
Lactase
67
Which two types of enzymes are present in the SI
Pancreatic and intestinal enzymes
68
What substances are absorbed unchanged in the SI
Minerals, vitamins and cholesterol
69
How much (%) absorption occurs in the SI
90%
70
How is nutrients absorbed in the SI
Nutrients is trapped in the folds of the intestinal wall and absorbed through the microvilli
71
What substances are absorbed in the duodenum and upper jejunum
Carbohydrates, amino acids, water-soluble vitamins and most minerals (except Na+, Cl-, K2+)
72
What substances are absorbed in the jejunum
Lipids and fat-soluble vitamins
73
What substances are absorbed in the terminal ileum
Vitamin B12
74
Which two process are involved in the absorption of substances in the SI
Active transport and passive diffusion
75
What is passive diffusion
When nutrients move from high to low concentration , no energy is required
76
How is fat absorbed in the SI
Passive diffusion
77
What is (secondary) active transport
When nutrients move from low to high concentration with the help of a carrier protien
78
How are amino acids and monosaccharides absorbed in the SI
(Secondary) active transport
79
In which vessels are substances from the SI transported to the liver
Hepatic portal vein or lymph
80
Which nutrients are absorbed directly into the blood stream
Water-soluble nutrients
81
How are fat-soluble compounds transported and why
In the lymph as they are too big to directly enter the blood
82
Which two vessels does each villus contain
Blood vessels and lymph
83
How do monosaccharides, amino acids and nucleotides cross the gut lining and where do they enter
Cross the gut lining by active transport and enter the bloodstream heading to the liver
84
How do fatty acids and monoglycerides cross the gut lining and where do they enter
They diffuse into the gut epithelium before reforming and entering the lymphatic system
85
How long is the large intestine
~5 feet long
86
What is the LI comprised of
Cecum, colon, rectum and anal canal
87
What is the function of bacteria in the LI
To digest small amounts of fibre
88
What does the bacterial activity in the LI form
Vitamin K, vitamin B12, thiamin, riboflavin, biotin and gases
89
What is absorbed in the LI
Water, sodium, potassium chloride, some vitamin K
90
What happens to vitamin B12 in the LI
It is utilised by colonocytes
91
What happens to the remaining materials that aren't absorbed in the LI
They are eliminated via faeces
92
What are the 4 GI hormones
1. Gastrin
2. Secretin
3. Cholesytokinin (CCK)
4. Gastric inhibitory peptide (GIP)
93
What do the GI hormones influence
GI motility, stomach emptying, gall bladder contraction, intestinal absorption, hunger
94
What is the release of GI hormones stimulated by
Passing of food through the digestive tract
95
What does vagal stimulation (sight, smell, taste, distension of the stomach) stimulate
Gastrin secretion by the G cells of the stomach
96
What does gastrin stimulate
Causes stomach cells to produce peptidases and HCl
97
What and where is gastrin secreted
By the G cells in the stomach
98
What and where is secretin secreted
By the S cells of the duodenal muscosa
99
What causes the secretion of secretin
In response to acid
100
What is the function of secretin
It inhibits the release of gastrin
101
Which two hormones are released in response to the presence of the products of fat digestion
CCK and GIP
102
What is the function of CCK and GIP
To inhibit the release of gastrin and gastric acid
103
Describe the sequence of hormonal events stimulated regarding the secretion and entering the bloodstream of secretin and CCK
1. Chyme enters the duodenum causing the duodenal mucosal cells to release secretin and CCK
2. CCK and secretin enter the blood stream
4. Upon reaching the pancrease CCK induces the secretion of pancreatic juice and secretin causes the secretion of bicarbonate-rich pancreatic juice
4. Secretin causes the liver to secrete more bile, CCK stimulates the gall bladder to release stored bile
104
Features of the stomach
Starts process of fat and protein digestion, little absorption, gastrin stimulates release of HCl and pesinogen
105
Features of SI
site of most digestion and absorption, pancreatic and brush border enzymes, bile aids fat digestion, CCK secretin and GIP are released, absorption via diffusion/ active transport into circulation or lymph
106
Features of LI
Little digestion (bacteria), little absorption (absorbs water, sodium, potassium chloride and some vit K)
107
Name 4 GI disorders
1. Gastrooesophageal reflux disease (GERD)
2. Lactose intolerance
3. Diarrhoea
4. Constipation
108
Gastrooesophageal reflux disease (GERD)
Incompetence of the lower oesophageal sphincter, allows reflux of gastric contents into oesophagus
109
Lactose intolerance
Inability to digest lactose, deficiency of the enzyme lactase which leads to diarrhoea and cramping
110
Diarrhoea
Even small reductions (1%) in intestinal water absorption/ increases in secretions can increase water content enough to cause diarrohea
111
Constipation
Too much intestinal water absorption results in slow. reduced peristalsis.
112
Which 2 GI disorders are related to water absorption
Diarrohea and constipation
