Lecture DIGESTIVE SYSTEM part 2

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LectureDIGESTIVE SYSTEM part 2

• INTESTINE
• LIVER
• PANCREAS

Department of histology, cytology and embryology
KhNMU
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Small intestine

• Functions
• digestion liver, pancreas,
  enterocytes
• absorption enterocytes
• STRUCTURE 4 membranes

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Intestinal lining

• 1) plicae circularis mucosa submucosa
• 2) villi - consist of
• epithelium, lamina propria, mm
• 3) crypts invaginations of epithelium in the
  lamina propria

simple columnar epithelium absorptive
enterocytes, goblet, endocrine, Paneth cells and
stem cells
fenestrated capillaries and central lacteal
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Duodenum
Ileum
lacteal
Villus
serosa
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Epithelium(villus)
a
bb
gc
L

• high mag.
• 1). Enterocytes Columnar absorptive cells (a)
  have microvilli brush border (bb) for
  absorption of digested food.
• Membrane and luminal digestion
• 2). Mucus-secreting goblet cells (gc) produce a
  protective mucus. Lymphocytes and plasma cells
  (L) are numerous in the lamina propria of the
  villus.

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Epithelium (crypt)
p
g
a

• high mag
• At the bottom of intestinal glands (crypts) are
• 3). the granule-containing Paneth cells (p).
  Lysozyme.
• Goblet (g) and absorptive (a) cells.

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3. Paneth cells, 4. enteroendocrine cells (CCK,
secretin, GIP), 5.undifferentiated
cellsstem, at the bottom of crypt
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5
3
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Villus,lacteal
ivs
lp
l
v
sm
ivs
c
gc
GALT
low

• The lamina propria (lp) contains blood-filled
  capillaries c, and lacteal lymphatic capillary
  l,
• smooth muscle cells (sm),(krok villus
  shortens) GALT

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Duodenum
v
low
m
lp
ig
v
mm
sm
v
m
me
sm
med
bg
s

• Mm 2 layers of sm.m.
• Submucosa is usual. Only in the duodenum it is
• filled with Brunners mucous glands (bg), around
  which - 2 layers of smooth muscle of the
  muscularis externa (me) surrounded by the serosa
  (s).

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Duodenum
c
villi
d
intestinal glands
mm
mm
Bg
low
s
med

• low med mag.
• Ducts (d) from Brunners glands (Bg) (s) pass
  through the muscularis mucosa (mm) to empty their
  alkaline mucus in or between the crypts (c).

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Duodenum
m
Brunners glands
high
s
med
crypts
submucosa
muscularis externa
muscul. mucosa
high

• nerve supply - submucosal (s) and myenteric (m)
  nerve plexuses.

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Jejunum
v
a
ig
g
ig
P
med
low

• low med. mag.
• The jejunum is like the duodenum ileum
• but has no submucosal glands and Peyers patches.
• Contains bigger amount of goblet cells

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Ileum
cr.
v
muscul. mucosa
v
sm
sm
ln
med
low
ln

• low med. mag.
• The major distinguishing feature is the
  aggregated lymphatic nodules (ln) called Peyers
  patches in the mucosa or submucosa

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Duodenum
Ileum
lacteal
Villus
COMPARE !
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Large intestine (bowel) - general

• Reabsorption of water, electrolytes, cellulous
• Elimination of wastes
• Inner lining - permanent internal folds of its
  mucosa submucosa called plicae circulares and
  crypts.
• Its mucosa lacks of villi.
• The submucosa is usual
• Circular longitudinal smooth muscle form the
  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.

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Taenia coli
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Colon
cr
muscularis mucosa
pc
med
submucosa
low
musc. ext.

• low med mag.
• Plicae circulares (pc) . Unlike the small
  intestine there are no mucosal villi.
• There are straight intestinal glands crypts
  (cr) composed mainly of
• 1. Goblet cells the most numerous .
• 2. Columnar absorptive cells
• 3. Enteroendocrine cells
• 4. Undifferentiated cells

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High.Magn.
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Large intestine COMPARE !

• Appendix

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Anal canal
ss
g
L
v
ig
mm
v
a
v
low
gc
high

• low high mag.
• Anal columns
• Brunched tubular glands (g)
• Stratified squmous epithelium (ss)

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Liver Gall Bladder

• Liver has specific location on the way of
  absorbed material, that is why has very original
  vasculature and functions

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Functions

• Bile synthesis and secretion (emulsification)
• Excretion of bilirubin
• Protein synthesis
• Gluconeogenesis
• Storage
• Detoxification
• Protective
• Hemopoietic organ
• Endocrine

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Liver has lobulated structure
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Liver lobule is hexagonal in shape

• ? at its center - central vein
• ? hepatic plates(cords of cells -
  hepatocytes)locate radially
• ? hepatic sinusoids locate between plates

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Liver lobule
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cv
pt
sv

• Connective tissue poor develops
• Central veins (cv) drain to a sublobular vein
  (sv).
• The portal triads (pt) locate at lobule coners.

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• Hepatic plate(cord)is one or two cells thick
• Inside the plate between cells the bile
  canaliculi locate

Bile canaliculus
hepatocyte
sinusoid
Kupffer cell
The bile canaliculus wall is made up of
hepatocytes
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• Hepatocytes
• Polyhedral
• 6 surfaces
• Vascular and bile surfaces
• a. RER
• b. SER
• c. Golgi complex
• d. Mitochondria
• e. Inclusions
• Jaundice
• ?High regeneration

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EM of Liver

• Liver
• Two hepatocytes (h) are seen.
• The bile canaliculus form a network that
  eventually empty into bile duct at the periphery
  of the lobule.
• Ultimately ducts will empty into the gall
  bladder.

h
h
b
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• Hepatic sinusoid
• Lined by endothelium
• Hepatic macrophages
• (Kupffer cell)
• 
  

• 
  
  
  
• Space of Disse
• sinusoid
• Kupffer cell

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e
d
s

• high mag.
• Liver had been injected with carbon particles
• Kupffer cells containing carbon (red arrows)
• Sinusoids (s)
• A flattened endothelial cell (e)
• Space of Disse (d) between it and the hepatocytes

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Adipose cells storage vit. A
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Blood circulation of the liver

• Hepatic artery interlobular artery
• Portal vein interlobular vein
• 
  hepatic sinusoid
• 
  central vein
• cv
• 
  sublobular vein
• 
  hepatic vein
• The way of bile draining

s
d
cv
v
a
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At the lobule coners the portal triads are found
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cv
hs
pt

• Liver, injected
• with red gelatin to demonstrate the abundant
  vasculature.
• central vein (cv), the portal triad (pt)
• hepatic sinusoids (hs).

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Liver lobules 3 types
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Gall bladder
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Pancreas. Mixed gland

• Functions
• Exocrine
• Trypsinogen, pepsinogen, peptidase
• Amylase
• Lipase
• Deoxyribonuclease, ribonuclease
• Endocrine

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Pancreas compound acinar serous gland
low
lobule

• Exocrine 98-99
• Endocrine 1-2
• Capsule
• Septa
• Lobules
• Interlobular duct
• Serous secretory units

lobule
id
med
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• Septa (c.t.)
• Lobules
• Interlobular duct
• Serous secretory units

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Pancreas. Exocrine secretory units

• Zymogen granules
• Intercalated duct is intercalated into the s.unit
  
• centroacinar cells

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• Exocrine part
• Structural features of the acinus
• ? Purely serous.
• ? the presence of centroacinar cells in the
  center of the acinus

Intercalated duct
Serous cells
Centroacinar cells
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Pancreas. Endocrine

• Islets of Langerhans, - low med. mag.
• Scattered among exocrine secretory units
  spherical collections of light-staining cords of
  endocrine cells
• .

low, HE
med, trichrome
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Pancreas. Endocrine

• islets of Langerhans
• 1. B cell
• 2. A cell
• 3. D cell
• 4. minor cells
• PP, D1, EC,

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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