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Lecture DIGESTIVE SYSTEM part 2. INTESTINE LIVER PANCREAS. Department of histology, cytology and embryology KhNMU. Small intestine. Functions: digestion – liver, pancreas, enterocytes absorption – enterocytes STRUCTURE: 4 membranes. Intestinal lining:.

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lecture digestive system part 2
LectureDIGESTIVE SYSTEM part 2

INTESTINE

LIVER

PANCREAS

Department of histology, cytology and

embryology KhNMU

small intestine
Small intestine
  • Functions:
  • digestion – liver, pancreas, enterocytes
  • absorption – enterocytes
  • STRUCTURE: 4 membranes
intestinal lining
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

slide4

Duodenum

Ileum

lacteal

Villus

serosa

epithelium villus

a

Epithelium(villus)

bb

  • 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.

gc

L

slide6

Epithelium

(crypt)

  • high mag

At the bottom of intestinal glands (crypts) are

3). the granule-containing Paneth cells (p). Lysozyme.

Goblet (g) and absorptive (a) cells.

p

g

a

slide7

3. Paneth cells, 4. enteroendocrine cells (CCK, secretin, GIP),

5.undifferentiated cells=stem, at the bottom of crypt

4

5

3

villus lacteal

ivs

Villus,lacteal

lp

l

v

sm

The lamina propria (lp)contains blood-filledcapillariesc, and lacteal –lymphatic capillaryl,

smooth muscle cells (sm),(krok – villus shortens); GALT

ivs

c

gc

GALT

low

duodenum

v

Duodenum

low

  • Mm – 2 layers of sm.m.
  • Submucosa is usual. Only in the duodenum it is

filled with Brunner’s mucous glands (bg), around which - 2 layers of smooth muscle of the muscularis externa (me)surrounded by the serosa(s).

m

lp

ig

v

mm

sm

v

m

me

sm

med

s

bg

duodenum1
Duodenum

c

villi

  • low & med mag.

Ducts (d) from Brunner’s glands (Bg) (s) pass through the muscularis mucosa (mm) to empty their alkaline mucus in or between the crypts (c).

d

intestinal

glands

mm

mm

Bg

low

s

med

duodenum2
Duodenum

m

Brunner’s glands

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

high

s

med

crypts

submucosa

muscularis

externa

muscul.

mucosa

high

jejunum
Jejunum

v

a

ig

  • low & med. mag.

The jejunum is like the duodenum & ileum

but has no submucosal glands and Peyer’s patches.

Contains bigger amount of goblet cells

g

ig

P

med

low

ileum
Ileum

cr.

v

muscul.

mucosa

  • low & med. mag.

The major distinguishing feature is the aggregated lymphatic nodules (ln) called Peyer’s patchesin the mucosa or submucosa

v

sm

sm

ln

med

low

ln

slide14

Duodenum

Ileum

lacteal

Villus

COMPARE !

large intestine bowel general
Large intestine (bowel) - general
  • Reabsorption of water, electrolytes, cellulous
  • Elimination of wastes
  • Inner lining - permanent internalfoldsof 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.
colon

cr

Colon
  • 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

muscularis

mucosa

pc

med

submucosa

low

musc. ext.

anal canal

ss

g

Anal canal

L

  • low & high mag.

Anal columns

Brunched tubular glands (g)

Stratified squmous epithelium (ss)

v

ig

mm

v

a

v

low

gc

high

liver gall bladder

Liver & Gall Bladder

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

functions
Functions:
  • Bile synthesis and secretion (emulsification)
  • Excretion of bilirubin
  • Protein synthesis
  • Gluconeogenesis
  • Storage
  • Detoxification
  • Protective
  • Hemopoietic organ
  • Endocrine
liver lobule is hexagonal in shape
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

slide26
Connective tissue poor develops

Central veins (cv) drainto a sublobular vein (sv).

The portal triads (pt) locate at lobule coners.

cv

sv

pt

slide27
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

slide28
Hepatocytes:

Polyhedral

6 surfaces

Vascular and bile surfaces

a. RER

b. SER

c. Golgi complex

d. Mitochondria

e. Inclusions

  • Jaundice
  • ①High regeneration
em of liver
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

slide30
Hepatic sinusoid

Lined by endothelium

Hepatic macrophages

(Kupffer cell)

  • Space of Disse
        • sinusoid
          • Kupffer cell
slide31

e

d

  • 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

s

blood circulation of the liver
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

slide35

cv

  • Liver, injected

with red gelatin to demonstrate the abundant vasculature.

central vein (cv), the portal triad (pt)

hepatic sinusoids (hs).

hs

pt

pancreas mixed gland
Pancreas. Mixed gland
  • Functions:
        • Exocrine
  • Trypsinogen, pepsinogen, peptidase
  • Amylase
  • Lipase
  • Deoxyribonuclease, ribonuclease
        • Endocrine
pancreas compound acinar serous gland
Pancreas – compound acinar serous gland

low

lobule

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

lobule

id

med

slide40
Septa (c.t.)
  • Lobules
  • Interlobular duct
  • Serous secretory units
pancreas exocrine secretory units
Pancreas. Exocrine secretory units
  • Zymogen granules
  • Intercalated duct is intercalated into the s.unit =

centroacinar cells

slide42
Exocrine part

Structural features of the acinus:

① Purely serous.

② the presence of centroacinar cells in the center of the acinus

Intercalated duct

Serous cells

Centroacinar cells

pancreas endocrine
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 endocrine1
Pancreas. Endocrine
  • islets of Langerhans:
  • 1. B cell
  • 2. A cell
  • 3. D cell
  • 4. minor cells:

PP, D1, EC,

i slets of langerhans
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