Digestive Sys tem Digestive Glan ds
Jan 13, 2016
Digestive System
Digestive Glands
Components of Digestive Glands
• Small digestive glands:
found in the wall of digestive tract
• Accessory glands (large digestive glands)
Salivary glands
Pancreas
Liver
General structure of Digestive Glands
• Parenchyma:(functional portion of an organ)
acini/gland cells
ducts
• Stroma: (non-functional portion of an organ)
capsule
CT inside the organ
Salivary Glands
Salivary GlandsGeneral structure of the large salivary glands
Parenchyma
acinus
duct
Serous acinus
Mucous acinus
Seromucous/mixed acinus
Intercalated duct
Striated/secretory duct
Interlobular duct
Excretory duct
Model (structure of the large salivary glands)
Salivary GlandsStructural characteristic of gland cell:
Serous acinus: comprised by serous cells.
﹡zymogen granules in apical cytoplasm.
Mucous acinus: comprised by mucous cells.
﹡mucinogen granules in cytoplasm.
Seromucous acinus: comprised by both cells.
/mixed acinus demilume ﹡
Serous acinus ﹡zymogen granules in apical cytoplasm.
Serous cell:
Basal lamina(bl);
Connective tissue (ct);
Desmosome (d);
Endothelium (en);
Golgi comples (g);
Intercellular space (is);
Lumen (l);
Microvilli (mi);
Mitochondria (m);
Nucleus (nu);
RER (re);
Secretion granule (sg).
10.000x
Mucous acinus: ﹡mucinogen granules in cytoplasm.
Detail of mucous cells:
mucous cell (sc);
Golgi complex (gc);
Intercellular space (is);
Secretion granule (sg);
Lumen (l);
Nucleus (n);
RER (re).
10000x.
Seromucous acinus
/mixed acinus
demilume
Salivary GlandsAcinus
Duct
Intercalated duct:
Simple squamous/cuboidal epith.
Striated/secretory ducts:
simple tall columnar epith.
Interlobular duct:
pseudostratified columnar epith.
Excretory ducts:
stratified squamous epith.
Salivary Glands
Intercalated duct:
Simple squamous
or cuboidal epith.
Salivary GlandsIntercalated duct: simple squamous or cuboidal epith.
Detail of intercalated duct cell
Basal laminar (bl);
Desmosome (d);
Nerve fibers (nf);
Golgi complex (g);
Intercellular space (is);
Mitochondria (m);
Nucleus (nu);
RER (re).
13.000x
Salivary Glands
Striated/secretory duct: simple tall columnar epith.
Salivary GlandsStriated /secretory duct
Salivary Glands
Striated/secretory duct
The secretory ducts, which are continuous with intercalated ducts, are wider and lined with a simple columnar epithelium. As the secretion from the acini passed through the secretory ducts, the epithlium can re-absorb sodium (Na+) and water from the lumen to the interstitium and transport potassium (K+) into the saliva, thus changing the consistency of the saliva. The secretory ducts drain into interlobar ducts which run between lobules.
Salivary GlandsInterlobular duct: excretory duct:
Pseudostratified columnar epith. Stratified squamous epith.
Salivary glands
Include
﹡Parotid G.
﹡Submandibular G.
﹡Sublingual G.
Function:
﹡Moistening food.
﹡Carbohydrate digestion.
﹡Secrete IgA.
Pancreas
The pancreas is a lobular organ.
The pancreas has both exocrine functions (releases digestive enzyme secretions into the intestines) and endocrine functions (releases hormones into the blood).
Pancreas
Parenchyma
exocrine gland endocrine gland
produces produces
pancreatic juice hormones
Parenchyma
Parenchyma
Pancreas
Exocrine pancreas
Acini Ducts
Wholly consists of serous acini.
Small centroacinar cells in the lumen
Intercalated ducts
Interlobular ducts
Main pancreatic ducts
Major duodenal papilla
Exocrine Pancreas
Exocrine Pancreas
It releases the pancreatic juice.
Pancreatic juice contain many kinds of enzyme:
﹡amylase: hydrolyses starch & glycogen.
﹡lipase: hydrolyzes triglycerides
into fatty acids and mono-glycerides
﹡cholesterol esterase: breaks down
﹡trypsin and chymotrypsin:
hydrolyze proteins.
﹡ribonuclease & deoxyribonuclease:
split nucleic acids.
PancreasEndocrine pancreas
﹡Islets of Langerhans
Scatter throughout the exocrine pancreas.
﹡Three types of cells:
A-cells (20%) glucagon (glycogen→ glucose)
B-cells (75%) insulin
D-cells (5%) somatostatin
﹡Capillaries: each islet is richly supplied with blood vessels.
PancreasEndocrine pancreas
GlucagonPurpose: Assist insulin in regulating blood glucose (sugar) in the normal rangeAction: Forces many cells of the body to release (or produce) glucose (increasing blood sugar)Secreted in response to: Low blood glucoseSecretion inhibited by: High blood glucoseDisease due to deficient action: Some times nothing, sometimes hypoglycemiaDisease due to excess action: HyperglycemiaTumor called: Glucagonoma
InsulinPurpose: Regulate blood glucose (sugar) in the normal range Action: Forces many cells of the body to absorb and use glucose thereby decreasing blood sugar levelsSecreted in response to: High blood glucoseSecretion inhibited by: Low blood glucoseDisease due to deficient action: Diabetes Disease due to excess action: HypoglycemiaTumor called: Insulinoma.
Liver
Liver
General Introduction
﹡The largest gland (--2% of body weight in adult).
﹡respectively receives both venous & arterial blood through the portal v. (--75%) & hepatic A (--25%).
﹡CT of capsule extended into the parenchyma, forming “classical” liver lobules.
﹡Functions as an exocrine gland (secreting bile) and other very important roles.
Liver
LiverStructrues of Liver lobule
LiverStructures of Liver lobule
Model of Liver Lobule
LiverStructures of Liver lobule
﹡six-sided prism
with a central V. at its center.
﹡sheets of hepatocytes (or hepatic plates)
extend radially from the central V.
﹡sinusoids between hepatic plates.
Portal triads (or portal area):
In the corner of lobules.
Structures of Liver lobule
Liver
Portal Triads (or Portal Area)
Liver
﹡Definition:
The area of CT found in the angles where adjacent hepatic lobules meet.
﹡Components:
CT.+portal triad
interlobular A
interlobular V
interlobular bile duct
Portal Triads (or Portal Area)
Liver
Portal Triads (or Portal Area)
Liver
Sinusoids
Liver
﹡Dilated anastomosing venules between the hepatic plates.
﹡Blood pathway: periphery→central V.
﹡Kupffer cells line in the wall of sinusoids.
﹡EM (endothelium of sinusoid)
significant gaps;
numerous fenestration;
incomplete basal lamina.
Sinusoids
Liver
TEM
Sinusoids
Sinusoids
HepatocyteLiver
﹡typically large polyhedral cells with large round centrally located nucleus.
﹡abundance of organelles relates to its functions:
Mitochondria: provide energy
RER: protein synthesis
SER: bile formation/ metabolism of lipids and hormones/detoxification.
Lysosome: defence
Microbody: detoxification
Inclusions: glcogen particles, lipid droplets and pigments.
Hepatocyte
Liver
Functions of Hepatocyte
Liver
﹡Produce bile.
﹡Degrade glycogen to glucose under regulation of hormones.
﹡Involve the blood lipid metabolism.
﹡Synthesize the blood plasma proteins: albumin;fibrinogen, and so on
﹡Detoxification
Bile Canaliculus
Liver
Definition:
the tubular space limited by plasma membrane of two adjacent hepatocytes.
Structure:
LM: network-like structures are seen by silver impregnation.
EM: plasma membrane of adjacent ﹡hepatocytes
forms the wall of bile canaliculi.
﹡tight junctions form seals.
Bile Canaliculus
Bile Canaliculus
Perisinusoidal space (Disse’s Spaces)
Liver
A space between endothelium & hepatocyte.
﹡Be visible under EM.
﹡Occupy by numerous microvilli of hepatocytes.
﹡Fill with blood plasma.
﹡have fat-storing cells (storing fat & vitamin A)
﹡A site for substance exchange
Between the blood & the hepatocytes.
Perisinusoidal space (Disse’s Space)
Perisinusoidal space (Disse’s Space)
Sinusoids
LiverThree functional surface on the surface of hepatocyte
LiverBlood Supply
Liver
Liver
Liver
Liver