small intestine and accessory organs Flashcards
(45 cards)
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
