Digestive System Flashcards
1
Q
What is the alimentary tract?
A
Tube extending from mouth to anus
2
Q
Describe structure of alimentary tract
A
Muscular tube lined internally with epithelium
3
Q
What is the function of alimentary tract
A
Ingestion, processing, digestion, absorption + excretion
4
Q
What is the sequence of the digestive system?
A
Mouth —> pharynx —> oesophagus —> stomach —> small intestine —> large intestine —> anus
5
Q
What is the pathway that food takes?
A
Oral cavity –> pharynx –> epiglottis –> oesophagus –> stomach –> duodenum –> jejunum –> ileum –> caecum –> ascending colon –> transverse colon –> descending colon –> sigmoid colon –> rectum –> anus
6
Q
What is mucosa?
A
Type of epithelium
Moistened by glandular secretion
7
Q
Describe structure of lamina propria
Mucosa
A
Loose connective tissue
Small blood vessels, lymphatics + nerve fibres
Immune cells
8
Q
Describe structure of muscularis mucosa
A
Thin muscle layer
9
Q
What is the submucosa?
A
2nd layer of loose connective tissue
Between mucosa + main muscle layers
10
Q
Describe structure of submucosa
A
Blood vessels, lymphatic vessels
Neural tissue - submucosa plexus
11
Q
What does the submucosa plexus do?
A
Regulates contractions + glandular secretions
12
Q
What is the muscularis externa?
A
Smooth muscle typically divided into 2 layers
13
Q
What are the 2 layers of the muscularis externa?
A
Inner = circular layer Outer = longitudinal layer
14
Q
Why is it significant the muscularis externa have different layers?
A
Orientate in different directions
= contractions propel materials along tract
15
Q
What is located between muscle layers in muscularis externa?
A
2nd nerve plexus
= myenteric plexus
16
Q
What is the adventitia/serosa?
A
Covers muscularis externa
17
Q
Describe alimentary canal position
A
Suspended in peritoneal cavity, covered in serosa
18
Q
What are retroperitoneal organs covered in?
A
Adventitia NOT serosa
19
Q
What is the oral cavity lined with?
A
Stratified squamous epithelium
20
Q
What is function of oral cavity?
A
Ingestion + fragmentation of food
21
Q
What is found in the oral cavity?
A
Salivary glands
22
Q
Where are the salivary glands within the oral cavity?
A
Submucosa
23
Q
What are the three salivary glands?
A
Sublingual
Submandibular
Parotid
24
Q
What is the sublingual salivary gland?
A
Beneath tongue, many ducts
25
What is the submandibular salivary gland?
Floor of mouth, inner surface of mandible, ducts behind teeth
26
What is the parotid salivary gland?
Largest, empties at the molar
27
What is oral drug administration?
Given by mouth + swallowed
| Easiest + safest BUT slow absorption
28
What is sublingual drug adminstration?
Placed under tongue - dissolves in saliva
| Rapid absorption, high circulating levels
29
What is sublingual drug administration not used for?
Bad-tasting or irritating medications
30
What is buccal drug administration?
Placed in mouth next to cheek
| Rapid absorption, high circulating levels
31
What is disadvantage of buccal drug administration?
Swallow pill
32
Describe mucosa in oesophagus
Above diaphragm = stratified squamous epithelium
| Below = columnar epithelium
33
What is the mucosa in oesophagus?
Define lamina propria + muscularis
34
Describe muscularis externa in oesophagus
Striated muscle in upper 1/3
| Smooth lower 1/3
35
What does muscle do in oesophagus?
Contract rhythmically towards stomach
36
What does the lower oesophagus sphincter prevent?
Reflux, emesis + regurgitation
37
What is involved in the lower digestive tract?
Stomach
Small intestine
Large intestine
38
How is the efficiency of absorption improved?
By increasing SA between epithelium + lumen
39
How is the SA increased?
Intrusions/folding
Inversions
Formation complex glands
40
What is the function of the stomach?
Reservoir + digestion
41
What does the stomach do?
Mixes food with gastric juices to form semifluid mass called chyme
42
How does stomach initiate protein breakdown + absorption of vitamin B12?
Release of intrinsic factor
43
What are the 4 anatomical regions of the stomach?
Cardia (closest to heart)
Fundus (upper area)
Body (middle portion)
Pylorus (narrow bottom)
44
Describe structure of gastric mucosa?
Columnar epithelium
Mucosa folded
Shallow depression on surface
Entire mucosa has simple tubular gastric glands
45
What do the cardiac gland do?
Mucus producing gland
| Provide alkaline layer
46
What are the 4 cell types of corpus-fundic gland?
Chief cells
Parietal cells
Mucous neck cells
Endocrine cells
47
What do chief cells produce?
Pepsinogen
Gastric lipase
Chymosin
48
What do parietal cells produce?
Gastric acid
| Intrinsic factor
49
What do endocrine cells do?
Stimulate secretion of other cell types
50
What do pyloric glands contain?
Endocrine cells, NO chief cells
51
What are the gastric glands?
Cardiac gland
Corpus-fundic gland
Pyloric gland
52
What are the disorders of the stomach?
```
Achlorhydria
Dyspepsia
Gastritis
Gastroenteritis
Haematemesis
Hiatal hernia
```
53
What is achlorhydria ?
Lack of gastric acid in the stomach
54
What is dyspepsia?
Difficulty digesting food
55
What is gastritis?
Stomach inflammation
56
What is gastroenteritis ?
Inflammation of stomach + small intestine
57
What is haematemesis?
Vomiting of blood
58
What is hiatal hernia?
Protrusion of stomach through opening in diaphragm
59
What is the small intestine made up of?
Duodenum
Jejunum
Ileum
60
What does the pancreatic + bile duct empty into?
Duodenum
61
What is present in mucosa of small intestine?
```
Plicae
Microvilli
Tubular glands
Goblet cells
Intestinal villi
```
62
What does the plicae do?
Folds mucosa + submucosa
63
Describe plicae in small intestine
Permanent structures
| Absent from start of duodenum + distal ileum
64
What is the intestinal villi?
Entire intestine mucosa
65
What does the intestinal villi do?
Increase SA by x10
66
What is the main cell type for intestinal villi + why?
Enterocyte
| = absorptive function
67
What cells are the microvilli?
Enterocytes
68
What does the microvilli do?
Increase SA by x20
69
Where are the tubular glands in small intestine?
From base of villi through lamina propria to muscularis mucosa
70
What do tubular glands do?
Secrete intestinal juices
71
What cells in tubular glands + why?
Paneth cells at base of crypt
| = secretion + control of infection
72
Describe small intestine
Rich blood supply
| Large absorption SA
73
Describe absorption in small intestine
Secretin released upon appearance of chyme in small intestine, stimulates release of bicarbonate to neutralise chyme
74
Describe what happens in duodenum
Carbohydrates broken down into simple sugars
Proteins broken down
Fats emulsified by bile salts = fatty acids + monoglycerides by pancreatic lipase
Form micelles
75
Describe what happens in jejunum
Monosaccharides, amino acids absorbed
| H2O soluble vitamins, fat soluble vitamins
76
Describe what happens in ileum
Bile salts reabsorbed
| Vitamin B12 absorbed
77
What is the main sections of the large intestine?
Caecum (including appendix)
Colon
Rectum
78
What are the external + internal sphincter of large intestine under?
Voluntary control
79
What is the large intestine primarily involved in?
Absorption of fluids + electrolytes
Secretion of electrolytes
Formation, storage + periodic elimination of faeces
80
Describe structure of the large intestine
```
Columnar epithelium
Mucosal layer thicker
Surface relatively smooth
Crypts of Lieberkühn
Goblet cells more numerous
```
81
Why is large intestine surface relatively smooth?
No plicae or villi
82
Why is there bacteria in large intestine?
Synthesise vitamin K + B
83
Describe what happens in defecation
```
Faeces enters rectum
Rectum dilates, stimulating mass peristalsis
Levator ani muscle relaxes
Internal + external sphincter relax
Anus pulled up over faecal mass
Faecal mass expelled
```
84
Describe absorption of H2O in GI tract
Passive process driven by transport of solutes
| H2O ingested + secreted in balance with H2O absorbed
85
What does an antacid do?
Neutralise stomach acid
86
What does an antidiarrheal do?
Control loose stool
87
What does an antipasmodic do?
Calms GI spasms
88
What does an antiemetic do?
Prevents regurgitation
89
What does an cathartic do?
Causes vomiting or relieves constipation
90
What does an laxative do?
Relieves constipation
91
Describe the pancreas
Retroperitoneal
92
What is the functionality of the pancreas?
Exocrine + endocrine
93
What does the endocrine function of the pancreas do?
Islets produce insulin + glucagon
94
What does the exocrine function of the pancreas do?
Glandular secretion of digestive enzymes
95
What digestive enzymes are secreted by the pancreas?
```
Trypsin
Chymotrypsin
Carboxypeptidase
Pancreatic amylase
Pancreatic lipase
```
96
What is the endocrine pancreas?
Islets of Langerhans
97
What are 4 main cell types in endocrine pancreas?
β-cells - secrete insulin
Alpha-cells secrete glucagon
Other - secrete somatostatin
PP/F cells - secrete pancreatic polypeptides
98
What do β-cells do?
Stimulate glycogen, protein + fatty acid synthesis
| Facilitate glucose uptake, lower blood glucose
99
What is somatostatin?
Locally actin hormone, inhibits other endocrine cells
100
What do PP/F cells do?
Stimulate gastric chief cells, inhibit bile secretion
| Inhibit pancreatic exocrine function
101
What does the exocrine pancreas do?
Pancreatic juice secreted by acini
102
What is pancreatic juice?
Clear isosmotic alkaline fluid containing digestive enzyme precursors
103
What does cholecystokinin (CCK) induce?
Enzyme-rich secretion from acini
104
What does secretin cause?
HCO3- rich ductal cell secretion
105
What are the pancreatic enzymes?
Amylase
Lipase
Proteases
106
What is the max activity of amylase + what does it require?
pH 7
| Require bicarbonate acid neutralisation
107
What does amylase do?
Hydrolyse complex carbohydrates
108
What is the max activity of lipase?
pH 7-9
109
What does lipase do?
Emulsify + hydrolyse fats in presence of bile salts
110
What are proteases secreted as?
Proenzymes
111
What are proteases activated within?
Activated in proteolytic cascade within duodenum
112
What does the secretion of somatostatin do?
Increase blood glucose
Increase blood amino acids
Increase blood fatty acids
Increase conc of upper GI hormones
113
Where does somatostatin act?
Acts locally within endocrine pancreas to depress insulin + glucagon secretion
114
What is glucagon produced by?
Alpha cells of endocrine pancreas
115
What do glucagon prevent?
Hypoglycaemia by elevating blood glucose levels
116
What is glucagon stimulated by?
Cholinergic system, beta-sympathetic fibres
117
What is glucagon inhibited by?
Glucose, insulin somatostatin + alpha-sympathetic fibres
118
What does insulin have a direct effect on?
Carbohydrates, fats + protein metabolism
119
What is insulin degraded by?
Insulinase in liver
120
What is cellular activity of insulin controlled by?
Insulin receptors
121
What do the majority of cells respond to insulin for?
Glucose uptake
122
What happens if there is a low glucose level?
Decreases brain activity
123
What happens if there is a high glucose level?
Osmotic H2O loss, damaged blood vessels, organ disfunction
124
What are the effects of insulin?
Alters phosphorylation of metabolic enzymes
| Alter protein synthesis + gene transcription
125
What effect does insulin have on the muscle?
Inhibition of glycogenolysis + stimulation of glycogenesis
| Uptake of glucose + immediate use of storage as glycogen
126
What effect does insulin have on the liver?
Inhibition of glycogenolysis, stimulation of glycogenesis, activation glycogen synthase
Decease gluconeogenesis, stimulation of phosphofructokinase
Inhibition of hepatic ketone formation
Stimulation of amino acid uptake + protein synthesis
Inhibition of protein degradation
Uptake of glucose + storage of glycogen
127
What effect does insulin have on adipose tissue?
Promotes glucose uptake + conversion to glycerol for fat production
Stimulation of fat deposits + inhibition of lipolysis in adipose tissue
