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?)