Small intestine Flashcards
What three substances are secreted into the duodenum and where do they come from?
Chyme - stomach
Bile - gall bladder
Pancreatic juice - Pancreas
What three things increase the surface area of the small intestine?
Circular folds
Villi
Microvilli
What juice is secreted by the small intestine itself?
Succus entericus
What hormones are released from the small intestine and where are they released into
Systemic Circulation: CCK Gastrin GLP-1 GIP Secretin Motilin Ghrelin
What is included in the succus entericus and where are they released from?
Mucous - goblet cells at top of villi
Aqueous salt - dips between villi
Where is chlorine excreted from and to and which ion channel is involved in the second part of this?
From the lumen of the GI tract across the mucosa and into systemic circulation - through CTFR ion channel (CF)
What is segmentation for and how does it occur?
Mixing of food in the small intestine by contraction of smooth muscle
What are the two types of peristalsis that occur between meals?
Localised peristaltic contractions
Migrating motor complex (MMC) - sweeps from top to bottom of GI tract
How is segmentation affected by feeding?
It increases
What are the two parts of the pancreas and what do they each secrete?
Exocrine - digestive enzymes + alkaline fluid
Endocrine - insulin + glucagon
What is secreted in the pancreatic juice?
Digestive enzymes
Bicarbonate rich solution (neutralises acidic chyme from stomach)
What are the three types of digestive enzyme released from the pancreas and what do they each digest?
Proteases - protein (not activated until in small intestine as would auto digest the pancreas)
Amylases - carbohydrates
Lipases - fat
What are the 3 phases of pancreatic secretion?
Cephalic
Gastric
Intestinal
What are the two types of digestion and where are the enzymes from?
Luminal digestion - enzymes from pancreas
Membrane digestion - enzymes on brush border of membrane
What is the overall process of absorption and digestion called?
Assimilation
What is the process of digestion of carbohydrates (luminal/membrane digestion)?
Starch –> oligosaccharides (luminal digestion)
Oligosaccharides –> monosaccharides (membrane digestion)
Why is lactase so important?
Is is the only enzyme that can break down lactose into glucose
What form must carbohydrates be in to be absorbed?
Monomers
Where does absorption of carbohydrates occur?
Duodenum + jejeunum
What are the three types of intestinal failure?
Type 1: self-limiting
Type 2: prolonged with complications
Type 3: long term, stable
What is enteral and parenteral nutrition?
Enteral: Feeding directly into the small intestine
Parenteral: feeding directly into systemic circulation
What are the four parts of the duodenum?
Superior (with duodenal cap),
Descending,
Horizontal,
Ascending
Where does the duodenum start and end and what are these parts?
Starts: pyloric sprinter - anatomical sphincter controlling release of chyme into the stomach (parasympathetic)
Ends: duodenaljejunal flexure - change in the small intestine
Describe + name the parts and path of the biliary tree?
Left + right hepatic duct
==> common hepatic duct
common hepatic duct + cystic duct
==> common bile duct
What is the name of the blood supply to the gall bladder?
Cystic artery
Name the 4 parts of the pancreas
Head,
Neck,
Body,
Tail
What types of cell are in the pancreas?
Acinar cells
Is the pancreas parasympathetic or sympathetic?
All glands = parasympathetic
What drains the cells of the pancreas and what ‘hole’ does it pass through at the end?
The main pancreatic duct
Major duodenal papilla
What do the main pancreatic duct and the common bile duct pass through into the duodenum and what sphincter is associated with this?
Hepatopancreatic ampulla (of Vater) Sphincter of Oddi
Which hormone stimulates opening of the sphincter and release of digestive enzymes and bile into the duodenum?
CCK
Which arteries supply the pancreas and how do they join?
Superior pancreaticduodenal artery and inferior pancreaticduodenal artery
Anastomose
Does the pancreas have foregut or midgut blood supply
Both
The superior pancreaticduodenal artery is foregut (from the coeliac trunk) and the inferior pancreaticduodenal is midgut (off the superior mesenteric artery)
Which parts of the small intestine are fore or midgut organs?
Foregut: duodenum
Midgut: jejunum + ileum
(DJ ileum)
What are the differences between the jejunum and the ileum?
Jejunum = thicker Jejunum = more vasculature Jejunum = more circular folds Jejunum = more red Ileum = more fat (responsible for fat absorption)
Which arteries supply the jejunum and ileum?
Superior mesenteric artery via jejunal and ill arteries
What is the venous drainage of the jejunum and ileum?
Jejunal and Ileal veins into the superior mesenteric vein and the hepatic portal vein
At which vertebrae does the superior mesenteric artery leave the aorta?
L1
What does pepsin do?
Cleave protein to peptides
How do di-, tri- + tetra- peptides enter the cell?
PepT1 transporter - uses the proton gradient due to acidic microenvironment at brush border
What is the issue to digestion caused by fats?
They are insoluble/very limited solubility so must be emulsified to break into smaller particles for lipase action
What lipases are active where?
Gastric lipase in the stomach (stimulated by gastrin release - denatured by higher pH in the duodenum)
Pancreatic lipase in the duodenum (stimulated by CCK release - aided by bile salts from gall bladder)
What prevents lipid salts coalescing?
Bile salts (have -ve charges which repel each other) Hydrophobic/hydrophilic coat
How are free fatty acids absorbed?
Passive diffusion
Which circulation are short and long chain fatty acids transferred into?
Short = systemic Long = lymphatic
How is cholesterol absorbed?
Invagination of the apical membrane when bound to a specific protein
Describe the foregut blood supply
Screenshot on desktop
