gastrointestinal system Flashcards
(203 cards)
1
Q
what does the gastro-intestinal tract consist of?
A
- oral cavity
- oesophagus
- stomach
- small intestine
- large intestine
- anal canal
- anus
2
Q
what is associated with the gastrointestinal tract?
A
- liver
- gall bladder
- pancreas
3
Q
what do the mechanisms of the mouth deal with?
A
- digestion
- pathogen defence
4
Q
what are the mouth and tongue covered by?
A
- stratified squamous epithelium
- underlying submucosa containing salivary glands
5
Q
what are the 3 main salivary glands?
A
- parotid
- submandibular (below jawbone)
- sublingual (below tongue)
6
Q
what does the submandibular gland secrete?
A
- serous and mucous saliva
7
Q
what does the parotid gland secrete?
A
- serous saliva
8
Q
what do the sublingual glands secrete?
A
- mucous saliva
9
Q
where is saliva produced?
A
- acini of salvia glands
10
Q
how is saliva produced?
A
- by active filtration of ions from blood
- has similar composition to extracellular fluid
11
Q
where is composition of the salvia modified?
A
- in ducts within gland
12
Q
what does autonomic stimulation of glands do?
A
- changes composition and volume of saliva secreted
13
Q
what does parasympathetic stimulation produce?
A
- large volume of watery saliva
14
Q
what does sympathetic stimulation produce?
A
- small amount of mucous saliva
15
Q
what are the functions of saliva?
A
- lubrication
- digestion (by amylase)
- protection of oral mucosa
- antibacterial
- thirst stimulation
- speech
- absorption in mouth
16
Q
what do buccinator muscles do?
A
- muscles of tongue and cheeks
- aid pulverisation (chewing) and bolus formation
17
Q
what do the muscles of mastication do?
A
- move mandible (lower jaw bone)
- brings teeth into contact with maxilla teeth (upper)
18
Q
what is this joint known as?
A
- temporomandibular joint (TMJ)
19
Q
what are the 4 muscles of mastication?
A
- temporalis
- masseter
- lateral pterygoid
- medial pterygoid
20
Q
what does the temporals do?
A
- major effector
- elevate the jaw closing
- can retract lower jaw is been protruded
21
Q
what does the masseter do?
A
- elevates and protrudes the lower jaw
22
Q
what do the medial and lateral pterygoids do?
A
- help protrude the lower jaw unilaterally
- creates sider to side movement
23
Q
what 2 stages is swallowing divided into?
A
- pharyngeal
- oesophageal
24
Q
what type of control is initiation of swallowing?
A
- voluntary
- pharyngeal stage
25
what happens during swallowing initiation?
- muscles of tongue push bolus posteriorly
- oral cavity opens into oropharynx
26
what happens once bolus of food contacts back of pharynx?
- swallow reflex is triggered
27
what and why is the larynx lifted?
- by muscles of neck (supra hyoid muscles)
- closes off the airway
28
what is the swallow reflex?
- soft palate (palatine muscles covered in mucosa) rises to block off nasopharynx
- elevation of larynx moves the epiglottis over laryngeal opening
29
what do the pharyngeal constrictors do?
- contract sequentially to push food down pharynx and into oesophagus
30
what happens once food has entered oesophagus?
- involuntary control/action
- oesophageal stage
- smooth muscle pushes food towards stomach
31
what is the oesophagus?
- muscular tube
- passes from pharynx to the stomach
- passing through diaphragm at vertebral level of T10
32
what is found at junction between oesophagus and stomach?
- physiological sphincter called lower oesophageal sphincter
33
what does the lower oesophageal sphincter do?
- relaxes when we swallow to allow food to enter stomach
34
what do bands of muscle from diaphragm allow?
- further increase in tension as oesophagus passes through oesophageal hiatus
35
what is the oesophagus lined with?
- stratified squamous epithelium
36
when does a hiatus hernia occur?
- when upper part of stomach squeezes through gap between oesophagus and diaphragm
37
what are the symptoms of hiatus hernia?
- reflux of stomach contents into oesophagus (gastro-oesophageal reflux)
38
what is reflux treated with?
- drugs
- altering lifestyle
39
what do antacids do?
- neutralise the refluxed stomach contents
- reduces pain and damaging effects of acid
40
what can reflux be avoided by?
- eating frequent small meals
- reducing caffeine, alcohol, spicy meals
- rating upper body slightly when sleeping
41
what is optional in severe cases?
- keyhole surgery
42
what happens in keyhole surgery?
- replaces the stomach in the abdomen
- strengthens diaphragm surrounding hiatus
43
what is the common group effected by hiatus hernia?
- overweight middle aged women
- elderly people
- pregnant women
44
what does the stomach act as?
- food blender and reservoir
45
what pH environment is found in stomach?
- low pH
- provided by gastric secretion
46
what does the low pH allow?
- aids digestion
- provides physiological barrier against pathogens
47
where is the stomach located?
- J shaped sac
- lies below diaphragm
48
what does the stomach open into?
- duodenum (proximal part of small intestine) at pyloric orifice
49
what are the different parts of the stomach?
- fundus
- body
- greater curvature
- lesser curvature
- antrum
- pylorus/pyloric part
- pyloric sphincter
50
what are the properties of the stomach mucosa secretions?
- highly acidic
- contain factors influencing digestion
51
what do the funds and body of stomach do?
- secrete acid from parietal cells
- secrete pepsinogen from peptic (chief) cells
52
what does the antral region of stomach produce?
- endocrine secretion which control gastric secretion and gastric motility
53
what are the endocrine secretions produced?
- gastrin
- histamine
- somatostatin
54
what allows distension of stomach?
- oblique layer of smooth muscle that allows distension of stomach
55
what protects the stomach lining from the acid conditions?
- epithelium consists of columnar epithelia
- tight junctions
- mucous cells
56
how do tight junctions protect the stomach?
- prevent damage to underlying tissues from acid secretions
57
how do mucous cells protect the stomach?
- constitutive secretion of alkaline mucus layer
- provides mechanical barrier to acid secretions and pathogens
58
what 3 parts is the small intestine divided into?
- duodenum
- jejunum
- ileum
59
what can the duodenum be split into?
- superior
- descending
- horizontal
- ascending
60
where does the superior part travel?
- slightly superiorly and posteriorly at side of vertebral column (L1)
61
where does the descending part travel?
- inferiorly over part of kidney to L3
62
where does the horizontal part travel?
- medially to left
- crosses aorta at L3
63
where does the ascending part travel?
- superiorly on left of aorta to L2 where becomes jejunum
64
what does the descending duodenum receive?
- further digestive secretions from liver and gallbladder via common bile duct
- from pancreas via main pancreatic duct
65
where does the jejunum begin?
- duodenojejunal junction
- to left of L2 vertebrae
66
what is the jejunum?
- middle part of small intestine
- becomes ileum at an anatomically indistinct junction
67
what are the jejunum and ileum anchored to posterior body wall by?
- mesentery
- primary site of nutrient absorption
68
what is the main function of the large intestine?
- absorption of ions and water
69
what do muscles of the colon do?
- act to move intestinal contents towards anus
70
what are the 3 bands of longitudinal smooth muscle in large intestine known as?
- taeniae coli
71
what regions is the large intestine split into?
- caecum
- ascending colon
- transverses colon
- descending colon
- sigmoid colon
- rectum
- anal canal
72
what is the caecum?
- pouch of large intestine
- contains vermiform appendix
73
where does the ascending colon travel?
- superiorly from right lower to right upper quadrant
- forms 90 degree bend left into transverse colon (colon flexure)
74
where does the transverse colon travel?
- from right upper to left upper quadrant
- forms 90 degree bend into descending colon (left colic flexure)
75
where does the descending colon travel?
- left upper quadrant to left lower quadrant
- becomes sigmoid colon
76
what does the sigmoid colon connect?
- descending colon to rectum
77
where do the rectum and anal canal sit?
- within pelvic cavity posterior to vagina (female) and prostate (male)
78
where is the liver located?
- right upper quadrant of abdomen
- directly beneath diaphragm
79
what are the functions of the liver?
- glucose storage
- protein, lipoprotein and cholesterol synthesis
- digestion (production of bile and bile salts)
- storage of fat soluble vitamins
- toxin and drug metabolism and excretion
80
how does the liver aid glucose storage?
- store glucose and glycogen
- conversion stimulated by insulin
- energy store released when blood sugar levels fall
81
how does the liver help in protein, lipoprotein and cholesterol synthesis?
- synthesis most that act as transporters (mainly albumin)
- synthesises proteins that act as clotting factors in blood
82
what does albumin do?
- acts as transporter for many molecules
- helps maintain reabsorption from tissues into blood
83
what does lack of albumin cause?
- oedema (build up of fluid causing swelling)
84
what does cholesterol do?
- synthesised by liver
- used directly in cell membranes
- converted to sex hormones
85
how does the liver help in digestion?
- produces bile salts
- allows emulsification of intestines to increase SA and allow more absorption
86
how does the liver allow storage of fat soluble vitamins?
- can be stored in fat reserves in liver
- if not present in diet, body can use its stores
87
how does the liver help in toxin and drug metabolism and excretion?
- liver enzymes metabolise drugs
- byproducts exerted into bile
88
what is bilirubin and its function?
- released by spleen from breakdown of RBC
- modified by liver so can be excreted bile
89
what 4 lobes does the liver consist of?
- right
- left
- caudate
- quadrate
90
what is the gallbladder?
- fluid filled sac
91
what does the gallbladder store?
- bile
92
what is the gall bladder made up of?
- fundus
- body
- neck
93
what does the neck lead to?
- cystic duct
- allows transport of bile to and from gallbladder
94
what does the hepatobiliary system look at?
- production and flow of bile
95
what does the bicarbonate content of hepatobiliary system allow?
- alkaline pH
- decreases the acidity of gastric contents released from stomach
- prevents damage to intestines
96
what does decrease in pH facilitate?
- emulsion of fats from stomach by salts contained in bile
97
what does emulsification of fats do?
- increases SA of insoluble nutrients
- increases rate of digestion
98
what do enzymes in the liver breakdown?
- alcohol
- other drugs products toxic waste products
99
what is bile produced by?
- hepatocytes within liver
100
what are hepatocytes?
- epithelial cells
- arranged to form 3d lattice
101
what runs between layers of hepatocytes in liver?
- sinusoids
102
what do sinusoids allow?
- close contact between hepatocytes and portal blood supply
103
how are products of hepatocyte function removed?
- via small channels between cells called canaliculi
104
what do the canaliculi drain into?
- bile ducts
105
what does bile drain from the liver via?
- right and left hepatic ducts which join to form common hepatic duct
106
what is the common hepatic duct joined by?
- cystic duct that drain bile from gall bladder
107
what forms the common bile duct?
- unity of cystic duct and common hepatic duct
108
where can bile from common hepatic duct travel?
- up cystic duct to be stored in gallbladder
- carry on to descending duodenum via common bile duct
109
what happens to stored bile in between meals?
- concentrated by gallbladder
110
what does presence of food in duodenum cause?
- gallbladder contraction
- bile transport down cystic duct to common bile duct
- to duodenum
111
what do all the ducts combine to form?
- biliary tract
112
where does the main pancreatic duct join the common bile duct?
- at hepatopancreatic ampulla which opens into duodenum
113
what happens s with an occlusion at ampulla?
- bile and pancreatic enzyme secretion is blocked
114
what is the pancreas?
- elongated gland
- has endo and exocrine functions
- accessory to GI tract
115
where is the pancreas located?
- lies horizontally across posterior abdominal wall
- posterior to stomach
116
what 5 regions is the pancreas split into?
- uncinate process
- head
- neck
- body
- tail
117
what do exocrine tissues of the pancreas release?
- pancreatic juice
(major digestive secretion containing digestive enzymes)
118
what are the two components of the pancreatic juice?
- alkaline secretion
- enzyme rich secretion
119
what is the composition of the alkaline secretion?
- high bicarbonate and low enzyme content
- helps neutralise acidity of gastric contents
120
what is the composition of enzyme rich secretion?
- contains major enzymes involved in digestion
- secreted as pre-enzymes that are activated in gut so they don't digest the pancreas
121
what control is the pancreas under?
- partially under autonomic control
122
what does sympathetic stimulation do?
- decrease secretions
123
what does parasympathetic stimulation do?
- increase secretions
124
where do the exocrine glands secrete the enzymes?
- acinus
- modified in ducts
125
how is pancreatic juice transported?
- to duodenum via main pancreatic duct
126
how is the hepatopancreatic ampulla formed?
- main pancreatic duct joining to common bile duct
127
what is entrance to descending duodenum controlled by?
- hepatopancreatic sphincter
128
what is the peritoneum?
- layer of connective tissue that covers walls and viscera od abdomen
129
what is the greater omentum?
- reflection or flap of peritoneum tray covers abdominal contents
130
what is the mesentery?
- major reflection of peritoneum from posterior abdominal wall surrounding majority of small intestines
131
what is the peritoneal cavity?
- potential space continuous around all abdominal organs
132
what is the purpose of the peritoneum?
- anchors floppy abdominal organs to posterior body wall so don't move
- carries blood supply to organs
133
what are the different types of epithelium?
- simple squamous
- simple cuboidal
- simple columnar
- stratified squamous
- stratified cuboidal
- stratified columnar
134
what is the different thicknesses of layers?
- simple = 1 layer
- stratified = less than 1 layer
- pseudo stratified = 1 layer pretending to be 2
- squamous = flat cells
- columnar = column like cells
135
what does the wall of the digestive tract consist of?
- mucosa
- submucosa
- muscularis externa
- serosa
136
what 3 components does the mucosa have?
- epithelium
- lamina propria
- muscularis mucosa
137
what is the epithelium layer?
- thin layer
- lines lumen
- can be simple, stratified, squamous, columnar
- forms selective barrier that digestive molecules cross
- contains mucus secreting goblet cells and endocrine cells secreting digestive hormones
138
what is the lamina propria layer?
- layer of loose connective tissue
- has good blood supply
- contains lymphatics and white blood cells
- immunological barrier to pathogens in GI system
139
what is the muscularis mucosa layer?
- consists of thin layer of smooth muscle cells
- causes localised contractions in mucosa
140
what is the submucosa?
- layer of dense connective tissue
- contains submucosal plexus
141
what does the submucosal plexus do?
- control secretion and blood flow
- relays info from gut epithelium and stretch receptors in walls
142
what is the submucosal plexus part of?
- enteric nervous system
143
what is the enteric nervous system?
- branch of autonomic nervous system
- operates independently of CNS
144
what does the enteric nervous system consist of?
- 2 major plexiglass within GI wall (myenteric and submucosal plexiglass)
145
what is the muscularis externa?
- 2 smooth muscle layers (inner circular and outer longitudinal)
146
what happens along these layers?
- waves of contraction and relaxation forces food alone digestive tract
- known as peristalsis
147
where does the myenteric plexus lie?
- between layers of smooth muscle
- involved in control of GI motility
148
what is the serosa layer?
- layer of epithelium that form part of peritoneum
149
what is the purpose of the peritoneum?
- lines abdominal cavity
- cover all abdominal organs, anchoring them to body wall
150
what is the micro anatomy of the oesophagus?
- upper third = skeletal muscle
- lower two thirds = smooth muscle
151
where are mucus secreting glands present?
- in lamina propria and submucosa
152
what are the villi?
- finger like projections present throughout small intestine
153
what is the structure of the epithelial surface of the villi?
- simple columnar
154
what forms a brush border?
- microvilli on surfaces of villi
155
what does each villus contain?
- capillary network that transports absorbed amino acids and monosaccharides
- blind ended lymph vessel that transports absorbed fat
156
where does the capillary network drain?
- portal vein
157
what is the villus considered to be?
- functional unit of absorption
158
what are the 4 specialised cells present within the epithelium of the villi?
- absorptive cells
- goblet cells
- granular cells
- APUD cells
159
where do these specialised cells arise from?
- undifferentiated cells at base of crypts
160
what do the absorptive cells do?
- secrete digestive enzymes
- absorb nutrients
161
what do the goblet cells do?
- produce mucus that lubricates
- protects the epithelium from mechanical damage
162
what do the granular cells do?
- secret enzymes
- protect epithelium from bacteria
163
what do the APUD cells do?
- produce endocrine secretions
- regulate secretion and motility of GI tract and associated glands
164
where do the absorptive and goblet cels ascend the villi?
- from base of crypts
165
where are the mature cells located?
- tip of villus until they are shed
166
where do granular and APUD cells remain?
- base of crypts
167
what is the micro anatomy of the large intestine?
- not villous
- simple columnar epithelium
- contains crypts
168
what cells are present in large intestine?
- goblet
- absorptive
169
does the small or large intestine have more mucus?
- large
- has more goblet cells present so more mucus secreted
170
what features are similar in small and large intestine?
- lamina propria
- muscularis mucosa
- submucosa
171
what is different about the outer smooth muscle layer?
- surrounds large intestine (expect rectum) but is incomplete
- divided into 3 separate bands running length of colon
172
what is the incomplete structure known as?
- taeniae coli
173
what is the function of taeniae coli?
- aids peristalsis
- converge on base of vermiform appendix
174
what is a vermiform appendix?
- surgically useful feature
- used to identify a grossly infected appendix
175
where is taeniae coli not present?
- rectum
- anal canal
- vermiform appendix
176
what is the GI tract supplied by?
- branches of abdominal aorta
177
what is the most superior branch?
- coeliac trunk
- arises at T12 vertebral level
178
what do the branches of coeliac trunk supply?
foregut structures including:
- stomach
- superior duodenum
- liver
- gallbladder
- spleen
- pancreas
179
what does the coeliac trunk split into?
- common hepatic branch
- left gastric branch
- splenic arteries
180
what is the stomach supplied by?
- left and right gastric arteries
- left and right gastroepiploic arteries
181
what is the superior duodenum supplied by?
- superior pancreaticoduodenal artery
182
what is the liver supplied by?
- left and right hepatic arteries
183
what is the gallbladder supplied by?
- cystic artery
184
what is the spleen supplied by?
- splenic artery
185
what is the pancreas supplied by?
- superior pancreaticoduodenal artery
- pancreatic branches of splenic artery
186
what does the superior mesenteric artery supply?
- midgut structures including small and large intestines
187
where does the inferior pancreaticoduodenal artery arise from?
- superior mesenteric artery
188
what does the inferior pancreaticoduodenal artery supply?
- inferior part of duodenum, pancreas and anastomoses
189
what are anastomoses?
- union of parts or branches
- where communication occurs
- network forming
190
what are arcades?
- branches of superior mesenteric artery that form large loops
191
what do the arcades supply?
- jejunum and ileum
192
what does the ileocolic artery supply?
- terminal ileum
- caecum
- vermiform appendix
- proximal ascending colon
193
what does the right colic artery supply?
- distal ascending colon
194
what does the middle colic artery supply?
- distal transverse colon
195
what does the inferior mesenteric artery supply?
- handgun structures
- they include large intestines from proximal transverse colon to rectum
196
what does the left colic artery supply?
- descending colon
197
what is the sigmoid colon supplied by?
- sigmoid arteries
198
what does the superior rectal artery supply?
- proximal rectum
199
what is the distal rectum supplied by?
- branches of internal iliac artery
200
what is the blood flowing through intestines full of?
- amino acids
- monosaccharides
- poisons
- toxins
201
where does the blood from capillaries drain into?
- superior and inferior mesenteric veins
202
what do the mesenteric veins join?
- splenic vein to form hepatic portal vein
203
what does the hepatic vein carry?
- deoxygenated blood full of absorbed molecules from intestines to liver
