small intestine and accessory organs Flashcards
how long is the small intestine
6m
explain the sections and their lengths, that the small intestine is divided into
- duodenum (25cm) with 2 major accessory gland: liver and pancreas
- then, jejunum (2.5m)
- then, ileum (3.5m)
where does the small intestine go from and to in the body
from stomach to the cecum of large intestine
explain the duodenum
Head of pancreas lies in arc of duodenum
2 small mounds inside:
- lesser duodenal papilla *
- Major duodenal papilla = Greater duodenal papilla. Blue arrow indicates: leads in to the (Major duodenal papilla).
common bile duct &
pancreatic duct
- end in hepatopancreatic ampulla + sphincter
Accessory pancreatic duct opens into lesser duodenal papilla *
why does duodenum have a modified surface
to Increase surface area ~600-fold
- Aid digestion & absorption
what are the 3 modifications to the duodenum surface
- Circular folds (plicae circulares) of mucosa (a) & submucosa (b) at right angles to long axis of GI
- Villi of mucosa
(tiny, finger-like projections 0.5-1.5mm length) containing blood capillary network & lymph capillary (lacteal) - Microvilli
(1mm long cytoplasmic extensions of cells at surface of villi); combined microvilli form brush border
describe the mucosa of the duodenum
Is simple columnar
epithelium with 4
major cell types
name the 4 types of major cell types in the duodenum
absorptive cells
goblet cells
granular cells
enteroendocrine cells
explain the absorptive cells of the duodenum mucosa
- with microvilli
- produce digestive enzymes
- absorb digested food
explain the goblet cells of the duodenum mucosa
- produce protective mucus
explain the granular cells of the duodenum mucosa
help protect epithelium from bacteria
explain the enteroendocrine cells of the duodenum mucosa
secrete:
- Cholecystokinin (CCK) to stimulate contraction of gallbladder & enzyme secretion by pancreas, inhibit stomach emptying
- Secretin, inhibits gastric activity but stimulates secretion of pancreatic juice & gallbladder
- Gastrin, to stimulate acid & enzyme secretions of stomach, increase stomach motility.
explain the duodenum cells and their function in the duodenum
Base of duodenal villi have tubular invaginations called intestinal glands (=crypts of Lieberkuhn) where epithelial cells produced
Absorptive & goblet cells migrate from intestinal glands to cover surface of villi (& eventually shed from tip)
Granular & endocrine cells stay at base of glands
Into base of intestinal glands open duodenal glands (=Brunner’s) = coiled tubular mucous glands of submucosa
what happens to the structure As we progress through
small intestine
becommed the Jejenum & Ileum structure, which is where there’s a gradual decrease in:
- diameter,
- thickness of wall,
- No. of circular folds,
- Number of villi.
Duodenum & jejunum are major sites of what
nutrient absorption (some in ileum)
Ileum has numerous what nodes
numerous lymph nodes
- Peyer’s patches (blue arrows) in mucosa & submucosa
describe the Ileocecal junction
between ileum & large intestine, with ring of smooth muscle (ileocecal sphincter) & 1-way ileocecal valve
what is the largest internal organ
liver
explain the structure of the liver
- 2 major lobes (L&R)
- 2 minor lobes (caudate & quadrate)
Porta(gate)on inferior surface for entrance & exit of:
- Vessels (e.g., hepatic portal vein, hepatic artery, lymphatic vessels)
- Ducts
- Nerves (small hepatic nerve plexus)
what does the hepatic duct do and form
1 hepatic duct, from each L & R lobe of liver, transport bile out
when combine to form common hepatic duct
which joined by cystic duct from gallbladder (stores bile)
to form common bile duct
describe the histology (structure) of the liver
At the porta, connective tissue sends branching network of septa (walls), dividing liver into hexagon-shaped lobules
At each corner of lobule (Portal Triad), there is what
Hepatic portal vein
Hepatic artery
Hepatic (bile) duct
(& hepatic nerves & lymph vessels)
explain the Veins in liver lobule
A central vein in centre of each lobule
They unite to form hepatic veins, which
exit on posterior & superior surface of liver &
empty into inferior vena cava.
where do hepatic cords radiate out from
from central vein of each lobule like spokes of a wheel
what are Hepatic Sinusoids
are spaces between hepatic cords = blood channels
Hepatic Sinusoids are lined with what cells
lined with v.thin irregular squamous endothelium consisting of:
- very thin, sparse endothelial cells
- hepatic phagocytic cells (Kupffer cells).
Cords composed of hepatocytes are what
functional cells of liver
what are the 4 major functions of the cells of the liver
Synthesis of bile
Storage (e.g., glycogen)
Biotransformation (e.g., synthesize urea, metabolise cholesterol & fat, detoxify drugs & poisons, process several steroid hormones & Vit D)
Synthesis of blood components.
the hepatocyte cell is often used to represent what
a typical human epithelial cell.
where are bile canaliculi found
Lie between hepatocytes within each cord
what do bile canaliculi do
Takes bile to bile duct (which will end up in gall bladder).
what does bile contain
Bile salts
Cholesterol
Biliverdin & bilirubin
Mucus, fat, lecithin
Cells & cell debris
what do bile salts do
emulsify fats (so lipases can act on them)
help solubilise end products &
make them available for absorption by intestinal mucosa
aid peristalsis
- Most other bile contents are waste products for disposal.
describe the gall bladder structure
Sac-like, 8x4cm, inferior liver surface
3 tunics form gallbladder wall
which are Connected to common bile duct by cystic duct.
name the 3 tunics form gallbladder wall
Inner mucosa with rugae (expand)
SMC muscularis (contract)
Outer covering of serosa
- Connected to common bile duct by cystic duct.
the pancreas is a complex organ of what tissues
both endocrine & exocrine tissues
- Endocrine = Islets of Langerhans
what do Exocrine (acini) produce
digestive enzymes
what do Endocrine Islets of Langerhans produce
hormones.
describe the cells of the pancreatic ducts
lined with simple cuboidal epithelium; epithelial cells of acini are pyramid-shaped
explain pancreatic ducts connection
clusters of acini connected by small intercalated ducts
to
intralobular ducts
to
interlobular ducts
to
main pancreatic duct
to
common bile duct
explain pancreatic secretions
For digestion
trypsin, chymotrypsin, carboxypeptidase
- Protein
pancreatic amylase
- Carbohydrates
pancreatic lipase
- Fats
ribonuclease
- RNA
deoxyribonuclease
- DNA
cholesterol esterase
- cholesterol
bicarbonate ions
- (provides appropriate pH for pancreatic enzymes)
explain Bariatric Surgery
Weight loss surgery types:
- Gastric banding
- Sleeve gastrectomy
- Gastric bypass
give pros and cons of gastric band, Bariatric Surgery
pros:
- the band can be adjusted or removed
- no change to intestines
- short hospital stay
- lowest risk of vit and nut shortage
cons:
- might loose less weight than other surgery
- follow up visits to adjust bad happen frequently
- chance ur body wont adapt to band
might have to eventually replace or remove band
give pros and cons of gastric sleeve, Bariatric Surgery
pro:
- lose more than gastric band
- no change to intestines
- no bands or foreign objects in body
- short hospital stay
con:
- cant be reversed
- high risk of surgery-related problems than gastric band
- chance of vit shortage
give pros and cons of gastric bypass, Bariatric Surgery
pro:
- more weight loss than gastric band
- no foreign objects in body
con:
- difficult to reverse
- highest chance of vit shortage
- higher rick of surgery-related problems than gastric band
