2. Accessory organs of the digestive system:
Salivary Glands
Liver
Pancreas
3. Parotid – lateral side of face, anterior to ear, drain by
parotid duct to vestibule near 2nd upper molar
Submandibular – medial surface of mandible – drain near
lingual frenulum drain posterior to lower molars
Sublingual – in floor of mouth - drain near frenulum
1-1.5 l / day for
digestion
lubrication (swallowing)
moistening (tasting)
4. General structure of tubuloalveolar secretory glands associated with
the digestive tract, for example, the salivary glands and the pancreas.
9. Saliva - a mixed hypotonic watery secretion
derived from numerous large and small salivary
glands that all open into the oral cavity.
Contents (variable amounts of):
mucus
enzymes (principally amylase and the
antibacterial enzyme lysozyme)
antibodies - rich in IgA (secretory Ig)
inorganic ions
13. Largest ducts of salivary glands:
- Stratified Columnar epithelium (rare).
14. Xerostomia - or dry mouth is a common condition
associated with difficulties in chewing, swallowing,
tasting, and speaking, dental caries, and atrophy of the
oral mucosa.
The most common causes are: use of certain systemic
medications (mostly in the elderly), high doses of
radiation, and Sjögren's syndrome.
◦ Sjögren’s syndrome - chronic autoimmune disorder
characterized by lymphocytic infiltration of the exocrine glands,
particularly dryness of salivary and lacrimal glands (skin,
eyes, oral cavity, and salivary glands, nervous,
musculoskeletal, genitourinary, and vascular systems)
15. The largest gland of the body
◦ about 2% of the body weight in an adult).
Receives both venous blood and arterial blood
◦ ~75% of the blood supply (Venous via portal vein)
◦ ~25% of the blood supply (arterial blood via hepatic
artery)
16.
17. − Vascular functions, including formation of lymph
and the hepatic phagocytic system.
− Metabolic achievements in control of synthesis
and utilization of carbohydrates, lipids and
proteins.
− Secretory and excretory functions, particularly
with respect to the synthesis of secretion of bile.
18. Surrounded by Glisson’s capsule (thin capsule of
connective tissue)
The CT extends into the liver parenchyma and
divides it into the basic structural units of the liver, the
"classical" liver lobules.
19. The lobule is filled by cords of hepatic parenchymal
cells, hepatocytes, which radiate from the central vein
and are separated by vascular sinusoids.
Portal triads
◦ Portal triads are a key feature of the organization of the
liver
◦ Portal triads are embedded in interlobular connective
tissue.
◦ a branch of the portal vein, a branch of the hepatic artery
and a branch of the bile duct
20.
21. • Hepatocytes are separated from the bloodstream
by a thin discontinuous simple squamous
epithelium, which lines the sinusoids.
• Between the hepatocytes and the epithelial cells
is a narrow perisinusoidal space (of Disse).
• Contents of the blood plasma can freely enter the
perisinusoidal space through the openings in the
epithelium lining the sinusoids.
• Fixed macrophages, Kupffer cells, are attached to
the epithelium
22.
23. Space of Disse – a narrow
perisinusoidal space between the
hepatocytes and the sinusoids.
Contents of the blood plasma can
freely enter the perisinusoidal
space via sinusoids.
Fixed macrophages and
von Kupffer cells, are attached
to the epithelium (endothelial
cell).
24. • Drains the liver lobule
which open into the
intercalated or
sublobular veins of the
liver.
• These in turn coalesce
to form the hepatic
veins.
• Eventually empty into
the inferior vena cava.
25. Adjoining liver cells form the walls of the bile
canaliculi , which form a three dimensional
network within the sheets of hepatocytes.
Bile canaliculi connect via very short canals to
terminal bile ducts (cholangioles) which empty into
the interlobular bile ducts found in the portal
triads.
26.
27. • make up about 80% of the cells in the liver.
• are typically large polyhedral cells, with large
round centrally located nuclei. Hepatocytes are
frequently polyploid.
• function in the storage of glucose in the form of
glycogen (SER), vitamin A (possibly in specialized
adipocytes), vitamin B12, folic acid and iron.
28. participate in the turnover and transport of lipids.
The synthesis of plasmalipoproteins takes place
almost exclusively in the liver (RER/SER).
synthesize some of the plasma proteins (albumin, α
and β globulins, prothrombin, fibrinogen; RER).
metabolize/detoxify fat soluble compounds (drugs,
insecticides; SER).
participate in the turnover of steroid hormones.
secrete bile (up to 1 liter per day).
29. The portal vein, hepatic artery and bile duct enter the
liver through the porta hepatis.
If one of these vessels gives off a branch it is usually
accompanied by branches of the other two vessels.
Terminal branches of one of the vessels will
consequently be accompanied by terminal branches of
the other two vessels.
These groups of three tubes - a branch of the portal
vein, a branch of the hepatic artery and a branch of the
bile duct - are called portal triads.
30.
31.
32.
33.
34.
35. Bile contains both
◦ organic components (e.g. lecithin, cholesterol and
bilirubin - the latter is a breakdown product of
haemoglobin and accumulates in the blood in jaundice)
◦ and inorganic components (bile salts). The bile salts
facilitate the digestion and absorption of fat in the small
intestine.
36. Terminal bile ducts merge to form
◦ interlobular, intrahepatic bile ducts, which eventually
coalesce to form first the
◦ left and right hepatic ducts and then the common hepatic
duct, which connects to the cystic duct and the bile duct
(ductus choledochus).
◦ The bile duct carries the bile to the duodenum. The cystic
duct leads to the gall bladder.
37. Retroperitoneally
positioned on the
posterior wall of the
abdominal cavity at the
level of the second and
third lumbar vertebrae.
Lies behind stomach
Has no distinct
capsule, but is covered
by a thin layer of loose
connective tissue.
38. 99% of pancreas = exocrine organ
• produces digestive enzymes and buffers
• delivered to duodenum (small intestine) by the
pancreatic duct
1% of pancreas = endocrine organ
• produce glucagon and insulin
• regulate blood glucose levels
39. Exocrine – associated to ducts; pancreatic lipases
◦ Centroacinar cells – zymogen granules (protein-secreting
vesicles)
◦ Zymogen – proenzymes (Ex: Trypsinogen,
Chymotrypsinogen) that further developed depending on
the need.
Proenzymes are activated by enterokinases.
Major duct: Wirsung’s duct
Minor duct: Duct of Santorini
40. • Pancreatic juice is a clear alkaline fluid which
contains the precursors of enzymes of all classes
necessary to break down the main components of the
diet:
− trypsin, chymotrypsin and carboxypeptidase
hydrolyse proteins into smaller peptides or amino
acids;
− ribonuclease and deoxyribonuclease split the
corresponding nucleic acids;
− pancreatic amylase hydrolyses starch and glycogen
to glucose and small saccharides;
− pancreatic lipase hydrolyses triglycerides into fatty
acids and monoglycerides;
− cholesterol esterase breaks down cholesterol esters
into cholesterol and a fatty acid.
45. Alpha (acidophilic)
cells – glucagon
Beta (basophilic) cells
– insulin
D cells – somatostatin
(inhibits both A and B
cells)
F cells – pancreatic
polypeptide (control
gastric secretion and
exocrine pancreas)
Endocrine portion Exocrine portion
46.
47. • Lutz Slomianka (Content Ed.). Blue Histology. School of Anatomy and Human Biology -
The University of Western Australia. Content and page updated:last : 6/08/09;
http://www.lab.anhb.uwa.edu.au/mb140/corepages/oral/oral.htm
• Antonio RL Teixeira, Rubens J Nascimento, Nancy R Sturm. Evolution and pathology in
Chagas disease - A Review. Memorias do Instituto Oswaldo Cruz. August 2006 Vol.
101(5): 463-491.
• Junquiera et al. 2005. Basic Histology: Text and Atlas. 11th
Ed. McGraw-Hill
• Netter F. 2006. Atlas of Human Anatomy
• http://legacy.owensboro.kctcs.edu/gcaplan/anat2/histology/histo%20J%20digestive
%20system.htm
• Young et al. 2006. Wheater’s Functional Histology. 5th
Ed. Churchill-Livingstone Elsevier
Editor's Notes
Stratified cuboidal epithelium is a thin, stratified epithelium that usually consists of only two or three layers of cuboidal cells. This type of epithelium is usually confined to the lining of the larger excretory ducts of exocrine glands such as the salivary glands. Stratified cuboidal epithelium is probably not involved in significant absorptive or secretory activity but merely provides a more robust lining than would be afforded by a simple epithelium.
