8.4 Digestion Small Intestine, Pancreas, Liver, Gallbladder, Large Intestine,
DIGESTIVE SYSTEM 2 Intestine LIVER PANCREAS Small intestine Functions: digestion – by enzimes from...
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Transcript of DIGESTIVE SYSTEM 2 Intestine LIVER PANCREAS Small intestine Functions: digestion – by enzimes from...
DIGESTIVE SYSTEM 2
Intestine
LIVER
PANCREAS
Small intestine
Functions:• digestion – by enzimes from liver,
pancreas, and enterocytes (Membrane and luminal digestion)
• absorption – by enterocytes
IleumDuodenum
Villus
lacteal
serosa
Villus
1. Epithelium
Epithelium: simple columnar . Cells:1. Enterocytes -- Columnar absorptive cells --
have microvilli = brush border for absorption of digested food. 2. Goblet cells produce a protective mucus.
Lamina propria: Connective tissue, has fenestrated capillaries and central lacteal
-- lymphatic capillaryLymphocytes and plasma cells are very
numerous.
Epithelium(villus) bb
gc
L
Villus,lacteal
LOOK! The lamina propria (lp), blood-filled capillaries ©, and lacteal (l),smooth muscle cells (sm)GALT - lymphocytes
v
gc
ivs
ivs
llp
csm
GALT
low
== invaginations of epithelium in the lamina propria == intestinal glands
p
g
a
Crypt
1.Goblet and 2.absorptive cells.
3. the granule-containing Paneth cells - produce Lysozyme (. at the bottom
• 4. enteroendocrine cells
• 5. undifferentiated stem cells
Epithelium of crypt
p
g
a
Crypt
3. Paneth cells, 4. enteroendocrine cells (CCK, secretin, GIP),
5. undifferentiated cells
3
4
5
Submucosa filled with Brunner’s mucous glands - alkaline mucus
Duodenum
v
v
m
m
ig
sm
sm
lpmm
bg
me
s
low
med
v
medlow
Jejunum
The jejunum is like the duodenum & ileum
but has no submucosal glands and Peyer’s patches.
Contains bigger amount of goblet cells
v
ig
ig
g
a
P
• The major distinguishing feature is the aggregated lymphatic nodules (ln) called Peyer’s patches in the mucosa or submucosa
Ileum
medlow
v
v cr.
sm sm ln
ln
muscul.mucosa
Large intestine (bowal) - general
• Function = Reabsorbtion of water and electrolytes + Elimination of wastes
• Inner lining - permanent internal folds of its mucosa + submucosa called plicae circulares and crypts.
• Its mucosa lacks of villi.• muscularis externa: The inner circular layer is
uniform but the outer longitudinal layer has 3 thicker bands, the taenia coli.
• where the colon faces the abdominal cavity there is a serosa.
Taenia coli
High.Magn.
Liver & Gall Bladder
Liver has lobulated structure
Liver lobule is hexagonal in shape
① at its center - central
vein
② hepatic plates ( cords of cells – hepatocytes locate radially
③ hepatic sinusoids locate
between plates
Liver lobule
• Hepatic plate (cord) is one or two cells thick
• Between cells the bile canaliculi locate
The bile canaliculus wall is made up of hepatocytes
hepatocyte
sinusoid
Kupffer cell
Bile canaliculus
•Hepatocytes:
Polyhedral (6 surfaces)
!- Vascular and bile surfaces
Organelles - a. RERb. SERc. Golgi complexd. MitochondriaInclusions
The bile canaliculus form a network that eventually empty into bile duct at the periphery of the lobule.
h
h
b
Hepatic sinusoid
Lined by endotheliumandHepatic macrophages(Kupffer cell)
SSpace of Dissepace of Disse
sinusoidsinusoid
Kupffer cellKupffer cell
Look!
Sinusoids (s) are lined by highly fenestrated endothelial cells (e). Between the endothelial cells and hepatocytes (h), is the space of Disse (arrow).
s
e
h
h
RBC
In the Disse space lie Adipose cells - storage vitamin A
Blood circulation of the liver• Hepatic artery interlobular artery• Portal vein interlobular vein• hepatic sinusoid
• central vein• cv• sublobular vein• hepatic veinv
a
d
s
cv
At the lobule coners the portal triads are found:
Pancreas --mixed gland
• Functions:–Exocrine
• Trypsinogen, pepsinogen, peptidase• Amylase• Lipase• Deoxyribonuclease, ribonuclease
–Endocrine
Pancreas – compound acinar serous gland
• Exocrine – 98-99%• Endocrine – 1-2%
• Anatomy:
• Capsule
• Septae (have Interlobular duct)
• Lobules (Serous secretory units + ducts)
low
med
lobule id
lobule
Pancreas. Exocrine secretory units
• Zymogen granules
• Intercalated duct is intercalated into the s. unit =
centroacinar cells
Pancreas. Endocrine
• Islets of Langerhans, - low & med. mag.
Scattered among exocrine secretory units spherical collections of light-staining cords of endocrine cells
.
low, H&E
med, trichrome
Pancreas. Endocrine
• islets of Langerhans:
• 1. B cell
• 2. A cell
• 3. D cell
• 4. minor cells:PP, D1, EC,
Islets of Langerhans• B - insulin blood glucose
70%
• A – glucagon blood glucose
15-20%
• D – somatostatin insulin
5-10% glucagon
• PP – PP,
• D1 – VIP,
• EC – secretin, motilin
Control question
• Group, name
• 1. Compare Duodenum, Ileum and Colon Transversum
• 2. Liver: Blood supply. (What peculiar in the blood supply of the Liver?)