Digestive anatomy : structure and function Flashcards
The salivary glands The liver The small intestine The stomach The large intestine and colonic motility (99 cards)
1
Q
What are the three major salivary glands?
A
The parotid glands, the submandibular glands, and the sublingual glands
2
Q
What is the function of the salivary glands?
A
To produce saliva (crucial for start of digestion)
3
Q
Where are the parotid glands located?
A
In the front of the ears, beneath the skin, (thorugh the cheek muscle opposite the crown of the 2nd molar teeth)
4
Q
What is the saliva of the parotid glands like?
A
A watery saliva that has enzymes that breakdown carbs
5
Q
What enzyme do parotid glands produce?
A
Amylase
6
Q
What does amylase do?
A
Its an enzyme that breaks down starch into smaller molecules for digestion
7
Q
Where are the submandibular glands located?
A
Under the tongue, they are hook shaped, the duct opens on the sublingual papilla
8
Q
What is the saliva of the submandibular glands like?
A
Thicker saliva that has both enzymes and mucus (mucus= lubricate food and easier swallow)
9
Q
What enzymes do the submandibular glands secrete?
A
Amylase and lipase
10
Q
A
11
Q
What does lipase do?
A
Helps to breakdown fats
12
Q
What are the sublingual glands located?
A
Under the tongue, lateral to the submandibular
13
Q
What is the saliva of the sublingual glands like?
A
Thin, watery saliva with high concentraction of mucus
14
Q
What enzymes do sublingual glands produce?
A
Lingual lipase
15
Q
What causes salivary gland secretion?
A
Nerve-mediated reflex based on the intentsity and type of stimulation
16
Q
What type of stimulation activates salivary glands?
A
Chemosensory, masticatory or tactile
17
Q
What is the reflex modulated by and what is an example of that?
A
Nerve signals from other centres in the CNS, this can be seen through hyposalivation at times of anxiety
18
Q
What 2 reflexes increased salivary secretion?
A
the simple reflex and the conditioned reflex
19
Q
What is the 4 functions of salivia
A
- lubrication and binding
- Solubilization of dry food
- Oral hygiene
- Initiation of starch digestion
20
Q
What is a brief summary of the function of the liver?
A
Regulates most chemical levels in the blood and excrets bile, which helps carry away waste products, and blood in stomach passes through the liver to ‘reset it’, also metabolises drugs
21
Q
How does bile functions
A
By-products of broken down subtances are excreted into bile or blood, Bile enters the intestine and goes into faeces, blood by-products go through the kidney into urine
22
Q
Where is the liver located?
A
Upper right portion of the abdominal cavity, beneath the diaphragm and on top of the stomachs, right kidney and intestines
23
Q
What supplys blood to the liver (2)?
A
- Oxygenated blood flows from hepatic artery
- Nutrient rich blood flows from the hepatic portal vein
(liver holds around 1 pint (13%) of bodys blood supply)
24
Q
What is an overview of the liver anatomy?
A
It consists of 2 main lobes, made up of 8 segments each. With in the segments are lobules that are connected to small ducts that all connect to form the hepatic duct
25
What is the common hepatic duct?
This transports the bile to the gallbladder and the duodenum via the common bile duct
26
What is the hepatic artery?
The main blood vessel that supplies the liver with oxygenated blood
27
What is the hepatic Portal vein?
The blood vessel that carries bloods from the GI tract, gallbadder, pancres, and spleen to the liver
28
What is the structure of hepatocytes?
All hepatocytes are bordering on sinusoid on one side and a bile canaliculi on the other side.
29
Where is the small intestine located?
In the GI tract between the stomach and large intestine
30
What are the 3 parts of the small intestine?
The duodenum, jejunum and ileum
31
What is the small intestines function?
The digestion and absorption of nutrients
32
What are the 4 main layers of the small intestine?
Mucoas, submucosa, muscularis externa, adventitia
33
What does the mucosa layer of the small intestine contain?
The epithelium, lamina propria and muscularis mucosae
34
WhWhat does the submucosa layer of the small intestine contain?
Connective tissue layer (blood vessels, lymphatics, and submucosal plexus)
35
What does the muscularis externa layer of the small intestine contain?
2 smooth muscle layers: The outer longitudinal layer and inner circular layer - the myenteric plexus lies between
36
What does the adventitia layer of the small intestine contain?
Loosely arranged firboblasts and collagen w vessels and nerves through it
37
What are some modifications the small intestine has to aid its functions?
Muscose and submucosa form folds (plicae) in a circular fashion in lumen, plicae also contain microvilli to increase surface area = increasing absorption
38
What are the cells of the epithelium in the small intestine?
Enterocytes, Goblet cells, crypts of lieberkuhn
39
What roles do enterocytes play in the small intestine?
they are tall columnar cells which have absorptive functions, containing brush border enzymes on the surface
40
What roles do goblet cells play in the small intestine?
Exocrine glands which secrete mucin
41
What roles do Crypts of lieberkuhn play in the small intestine?
Glands in the eptielial lining that contain numerous cells like stem cells and enteroendocrine cells
42
What are Paneth cells in the small intestine?
secrete protective agents to protect against pathogens (defensins and lysosomes)
43
What are Peyer's patches in the small intestine?
(protective) only found in the ileum they contain mucosa associated lympathatic tissue (MALT) to hold WBCs and lymphocytes
44
What are the four main classes of enteroendocrine cells in the small intestine?
I cells, S cells, K cells, Enterochromaffin cells
45
What is the function of I cells (enteroendocrine) in the small intestine ?
Cholecystokinin (CCK) is secreted when fat is in the small intestine. CCK stimulates contraction of gallbladder (push bile) and release of pancreatic enzymes.
46
What is the function of S cells (enteroendocrine) in the small intestine ?
Secrete Secretin when low pH of chyme in small intestine. Secretin -> inhibts gastric emptying
47
What is the function of K cells (enteroendocrine) in the small intestine ?
Secrete Gastric-Inhibitory peptide (GIP) in response to chyme -> it stimulates insulin release
48
What is the function of Enterochromaffin cells (enteroendocrine) in the small intestine ?
mechanically stimulated by chyme. Release serotonin to activated cystic fibrosis transmembrane regulators -> secretes Cl-, NA+ ions and H2O
49
What three main substances the small intestine receives?
Bile
Pancreatic enzymes
Alkaline juice (HCO3-)
50
What is the Hepatopancreatic ampulla (ampulla of vater)
Common bile duct and pancreatic combine to form this which opens into the duodenum, regulated by the sphincter of Oddi
51
How can you tell when the duodenum becomes 'midgut'
The presence of major duodenal papilla
52
What is the stomach responsible for?
formation of chyme, synthesis of proteins necessary for vit absorption, microbial defences, and propages the peristaltic reflex
NOT ABSORPTION OF NUTRIENTS
53
What controls the physiological functions of the stomach?
Integration of enteric nervous system, parasympathetic nervous system, and secretion of various neurohormonal molecules
54
What are the 4 regions of the stomach?
Fundus, cardia, body, and pylorus
55
what do the walls of the stomach consist of?
4 tissue layers, same as small intestine, (mucosal layer, submucosa; muscularis externa; and adventitia/serosa)
56
What is the purpose of the gastric wall in the stomach?
To aid in the formation of a transient acidic environment (make food into chyme)
57
What can the gastric mucosal layer of the stomach further divide into (3)?
The surface epithelium, lamina propria, and muscularis mucosa
forms gastric pits and glands
58
What 6 cells line the gastric glands of the stomach?
Surface mucus cells, Parietal cells, Cheif cells, ECL like cells, G cells, D cells
59
What is the function of surface mucus cells in the gastric glands of the stomach?
mucus producing cells to act as a barrier against the gastric acid
60
What is the function of parietal cells in the gastric glands of the stomach?
Secrete gastric acid into the lumen of stomach through gastric pits , also secrete instrinsic factor
61
What is the function of chief cells in the gastric glands of the stomach?
Secrete pepsinogen (inactive until gastric acid) - pepsin digests proteins
Stimulated by cholinergic activity + by Gastrin
62
What is the function of ECL like cells in the gastric glands of the stomach?
secrete Histamine when stimulated by gastrin, indirectly increases HCL production bc of histamines direct actions on parietal cells
63
What is the function of G cells in the gastric glands of the stomach?
produce gastrin
gastrin increases HCL production
64
How does gastrin increase HCL production
2 ways:
- Stimulation of the ECL like cells to release histamine -> potentiates parietal cells
- Direct stimulation of parietal cells
65
What is the function of D cells in the gastric glands of the stomach?
secrete inhibitory molecule somatostatin (suppresses release of gastrin)
activated when lumen reaches level of acidity
66
What is the alimentary canal?
This long tube of organs makes a pathway for food to travel through the body. It runs from the mouth to the anus
67
What are the 3 movements associated with gastric motility?
Peristalic wave
Segmentation
Ancillary movements
68
What layer of the stomach containcs smooth muscle cells?
muscularis externa
69
How does the stomach turn bolus into chyme?
Though back and forth churning motions by inner oblique layer of muscularis externa
70
What controls when chyme can leave the stomach?
The pyloric sphincter
71
What is the peristalic wave of the stomach?
Contraction of the longitudinal smooth muscle layer rhythmically
only occurs in a forward motion with relaxation
72
What is the segmentation of the stomach?
Contraction of the circular muscle layer rhythmically
"waxing and meaning" pattern of electrical amplitudes -> can slow the speed of chyme progression
73
What is the ancillary movements of the stomach?
Stomach relaxation, needed to allow for accumulation of food
occurs thorugh parasympathetic activation of the vagus nerve which inhibits contraction of gastric muscle layer
74
What are the colons main roles?
Water absorption and immunity
75
What is absorption in the colon regulated by?
Neuroendocrine mechanisms:
Aldosterone + Glucocorticoids and somatostatin
76
What does aldosterone do in the colon?
Increased net absorption of water through stimulation of basolateral sodium potassium ATPase.
77
what does glucocorticoids and somatostatin do in the colon?
Increased net absorption of water through stimulation of basolateral sodium potassium ATPase.
78
What 5 ions/substances facilitate the colon in asborbing water?
Sodium, Cholride, Water, Potassium, Vitamins and fats
79
What are the Crypts of Lieberkuhn in the Colon?
Contain glands and mucus-porducing goblet cells, protecting the intestinal wall from bacteria + pressure on the walls
80
What are the 2 ways a colon protects itself?
Crypts of Lieberkuhn and gastrointestinal lymphoid tissue (GALT)
81
How is water absorbed in the colon?
Osmosis
Water diffuses in response to an osmotic gradient established by the absorption of electrolytes. Sodium is actively absorbed in the colon by sodium channels. Potassium is either absorbed or secreted depending on the concentration in the lumen. The electrochemical gradient created by the active absorption of sodium allows for this. Chloride ions are exchanged for bicarbonate ions across an electrochemical gradient.
82
What are the 2 types of movement in the colon?
Haustral shuttling and Mass movement
83
What is Haustral shuttling in the colon ?
the continous movement of food through the colon by regular contraction
84
What are the pacemaker cells of the colon?
they line the walls and send signals to the smooth muscle cells causing them to contract
85
what are haustra?
Segements of the large intestine
86
What is mass movement in the large intestine?
Occur 1-2 times a day, unifrom perstalic contraction of smooth muscle rapidly moving faeces into rectum -> feeling the urge to defecate
called the gastro-colic reflex
87
Name 2 diseases that related to issues in the GI tract?
Ulcerative Colitis and Crohn's disease
88
What is Ulcerative Colitis?
Inflammation of the large bowel, symptoms include bloody diarrhoea, tenesmus, pain and fatigue
(Can only usally occur in colon/rectum)
89
what is Crohn's Disease?
Type of IBD, symptoms include diarrhoea, abdominal pain, fever, and weight loss
(Can occur anywhere in GI tract)
90
What is the function of the rectum?
Temporary storage of faeces before defecation
91
What triggers the urge to defecate?
Stretch recepotrs from the rectum becoming full
contraction of rectal muscles, relation of internal anal sphincter and an initial contraction of the external anal spincter all contribute to defecation
92
What are the 2 main anal spincheters?
Internal and external
93
What is the internal anal spinchtor controlled by?
parasympathic fibres which relax involuntarily
94
What is the external anal spincter controlled by?
Is is skeletal muscle controled by somatic nerve supply from inferior anal branch of the pudendal nerve (controllable)
95
What is the rectosphicteric reflex?
A relaxation of the internal sphincter occuring when the rectum is distended
can be delayed by contration of external spincter
96
What is the process of defecation?
Relaxation of external anal sphincter, contraction of abdominal wall muscles, relaxation of pelvic wall muscles
Peristaltic waves then facilitate the movement of faeces through the anal cala
97
What are the 2 main types of laxative?
Bulk and stimulant
98
How does a bulk laxative work?
Adds fibre to the contents of the intenstine -> increases mass -> stimulates wall to cause peristalsis increasing movement of walls
99
How does stimulant laxatives work?
On sensory receptors in the wall of intestine to increase the amount of water and electrolytes being retained in the gut -> causes peristalsis helping to empty bowels
