1. Lecture DIGESTIVE SYSTEM part 2
INTESTINE
LIVER
PANCREAS
Department of histology, cytology and
embryology KhNMU

2. Small intestine STRUCTURE: 4 membranes Functions:
digestion – liver, pancreas, enterocytes
absorption – enterocytes
STRUCTURE: 4 membranes

3. 1) plicae circularis: mucosa + submucosa 2) villi - consist of:
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

4. Duodenum
Ileum
lacteal
Villus
serosa

5. 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.

6. Epithelium p (crypt) 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.

7. 5.undifferentiated cells=stem, at the bottom of crypt
3. Paneth cells, 4. enteroendocrine cells (CCK, secretin, GIP),
5.undifferentiated cells=stem, at the bottom of crypt 4 5 3

8. 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

9. Duodenum v m lp ig v mm sm m s bg Mm – 2 layers of sm.m.
low m lp ig v mm v sm m me sm s bg
med
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).

10. s low & med mag. Duodenum Bg c d mm
villi d
intestinal
glands mm mm Bg
low s
med
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).

11. Duodenum m s high med high
Brunner’s glands m
high s
med
crypts
submucosa
muscularis
externa
muscul.
mucosa
high
nerve supply - submucosal (s) and myenteric (m) nerve plexuses.

12. Jejunum low & med. mag. v a ig g ig P med low
The jejunum is like the duodenum & ileum
but has no submucosal glands and Peyer’s patches.
Contains bigger amount of goblet cells
low

13. Ileum cr. v v sm ln ln low & med. mag. sm med low
muscul.
mucosa v sm sm ln
med
low ln
low & med. mag.
The major distinguishing feature is the aggregated lymphatic nodules (ln) called Peyer’s patches in the mucosa or submucosa

14. Duodenum
Ileum
lacteal
Villus
COMPARE !

15. 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.

16. Taenia coli

17. Colon low & med mag. cr pc med low muscularis mucosa submucosa
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

18. High. Magn.

19. Large intestine COMPARE !
Appendix

20. Anal canal low & high mag. ss g L v ig v a v gc low mm high
Anal columns
Brunched tubular glands (g)
Stratified squmous epithelium (ss)

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

22. Functions: Bile synthesis and secretion (emulsification)
Excretion of bilirubin
Protein synthesis
Gluconeogenesis
Storage
Detoxification
Protective
Hemopoietic organ
Endocrine

23. Liver has lobulated structure

24. 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

25. Liver lobule

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

27. The bile canaliculus wall is made
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

28. Hepatocytes： Vascular and bile surfaces Polyhedral 6 surfaces a. RER
b. SER
c. Golgi complex
d. Mitochondria
e. Inclusions
Jaundice
①High regeneration

29. b h h 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

30. Hepatic sinusoid Hepatic macrophages (Kupffer cell)
Lined by endothelium
Hepatic macrophages
(Kupffer cell)
Space of Disse
sinusoid
Kupffer cell

31. 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

32. Adipose cells storage vit. A

33. 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

34. At the lobule coners the portal triads are found:

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

36. Liver lobules – 3 types

37. Gall bladder

38. Pancreas. Mixed gland Functions: Exocrine Endocrine
Trypsinogen, pepsinogen, peptidase
Amylase
Lipase
Deoxyribonuclease, ribonuclease
Endocrine

39. Pancreas – compound acinar serous gland
low
lobule
Exocrine – 98-99%
Endocrine – 1-2%
Capsule
Septa
Lobules
Interlobular duct
Serous secretory units
lobule id
med

40. Septa (c.t.)
Lobules
Interlobular duct
Serous secretory units

41. Pancreas. Exocrine secretory units
Zymogen granules
Intercalated duct is intercalated into the s.unit =
centroacinar cells

42. 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

43. Islets of Langerhans, - low & med. mag.
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

44. Pancreas. Endocrine islets of Langerhans: 1. B cell 2. A cell
3. D cell
4. minor cells:
PP, D1, EC,

45. 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