lecture digestive system part 2
DESCRIPTION
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:. - PowerPoint PPT PresentationTRANSCRIPT
Lecture
DIGESTIVE SYSTEM part 2
INTESTINE
LIVER
PANCREAS
Department of histology, cytology andembryology KhNMU
Small intestine
• Functions:
• digestion – liver, pancreas, enterocytes
• absorption – enterocytes
• STRUCTURE: 4 membranes
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
Epithelium(villus)
• 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.
a
bb
gc
L
• 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
Epithelium(crypt)
3. Paneth cells, 4. enteroendocrine cells (CCK, secretin, GIP),
5.undifferentiated cells=stem, at the bottom of crypt
3
4
5
Villus,lacteal
The lamina propria (lp) contains blood-filled capillaries c, and lacteal –lymphatic capillary l,smooth muscle cells (sm),(krok – villus shortens); GALT
v
gc
ivs
ivs
llp
csm
GALT
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).
Duodenum
v
v
m
m
ig
sm
sm
lpmm
bg
me
s
low
med
v
Duodenum
• 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
sBg
mm mm
c
med
low
villi
intestinalglands
Duodenum
• nerve supply - submucosal (s) and myenteric (m) nerve plexuses.
med
high
high
s
m
crypts
muscul.mucosa
submucosa muscularisexterna
Brunner’s glands
medlow
Jejunum
• 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
v
ig
ig
g
a
P
• low & med. mag. 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 (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.
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
pc
cr
low
med
muscularismucosa
submucosa
musc. ext.
Anal canal
• low & high mag.Anal columns
Brunched tubular glands (g)
Stratified squmous epithelium (ss)
ig
gss
gca v
v
v
lowhigh
L
mm
Liver & Gall Bladder
Liver has specific location – on the way of absorbed material, that is why has
very original vasculature and 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
① at its center - central
vein
② hepatic plates ( cords of cells - hepatocytes ) locate radially
③ hepatic sinusoids locate
between plates
• Connective tissue poor develops
Central veins (cv) drain to a sublobular vein (sv). The portal triads (pt) locate at lobule coners.
pt
cv
sv
• Hepatic plate(cord)is one or two cells thick
• Inside the plate between cells the bile canaliculi locate
The bile canaliculus wall is made up of hepatocytes
hepatocyte
sinusoid
Kupffer cell
Bile canaliculus
• Hepatocytes:
Polyhedral6 surfaces
Vascular and bile surfaces
a. RERb. SERc. Golgi complexd. Mitochondriae. Inclusions
• Jaundice
• ①High regeneration
EM of Liver
LiverTwo 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
Hepatic sinusoid
Lined by endothelium
Hepatic macrophages(Kupffer cell)
SSpace of Dissepace of Disse
sinusoidsinusoid
Kupffer cellKupffer cell
• 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
e d
s
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
v
a
d
s
cv
• Liver, injectedwith red gelatin to demonstrate the abundant vasculature.
central vein (cv), the portal triad (pt)
hepatic sinusoids (hs).
cv
pt
hs
Pancreas. Mixed gland
• Functions:–Exocrine
• Trypsinogen, pepsinogen, peptidase• Amylase• Lipase• Deoxyribonuclease, ribonuclease
–Endocrine
Pancreas – compound acinar serous gland
• Exocrine – 98-99%• Endocrine – 1-2%
• Capsule
• Septa
• Lobules
• Interlobular duct
• Serous secretory units
low
med
lobule id
lobule
Pancreas. Exocrine secretory units
• Zymogen granules
• Intercalated duct is intercalated into the s.unit =
centroacinar cells
• Exocrine partStructural features of the acinus:
① Purely serous.
② the presence of centroacinar cells in the center of the acinus
Centroacinar cells
Serous cells
Intercalated duct
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,