16.1.2 Digestive Glands

16.1.2 Digestive Glands
  • The digestive glands associated with the alimentary canal include the salivary glands, the liver and the pancreas. 
Salivary glands: 
  • Saliva is mainly produced by three pairs of salivary glands, the parotids (cheek- Stenson's duct), the sub-maxillary/sub-mandibular (lower jaw- Wharton's duct) and the sublinguals (below the tongue- ducts Rivinus). 
  • These glands situated just outside the buccal cavity secrete salivary juice into the buccal cavity.
Parotid gland
Submandibular submaxillary glands
Sublingual glands
Location
Cheeks
At the Junction of upper and lower jaw
In lower jaw below the tongue
Size
Largest
Medium
Smallest
Ducts
Stenson’s Duct
Wharton’s ducts
Ducts of RIvinus
% of secretion
20-25 %
70-75%
5%
Nerve
IX (glossopharyngial)
VII (facial)
VII (facial)

Lacks mucin, mainly produces Ptylin 
Contain mucin
Mainly mucin

Saliva: 
  • Daily secretion 1500 ml (approx)
  • 99.9% water
  • Salivary amylase (alpha-ptylin), Lysozyme, mucus and thyocynids 
  • electrolytes like Na+, K+, Cl-, HCO3- 
  • Ig-A 
  • A small amount of urea and uric acid
The liver
  • The liver is the largest gland of the body weighing about 1.2 to 1.5 kg in an adult human. 
  • It is situated in the abdominal cavity, just below the diaphragm and has two lobes. 
  • The hepatic lobules are the structural and functional units of the liver containing hepatic cells arranged in the form of cords. 
  • Sinusoids are the venousus network in hepatic lobules and contain Kuffer cells (phagocytic).
  • Portal Triads: portal venue, portal arteriole and bile duct together make portal triads and are 6 in number. 
  • Each lobule is covered by a thin connective tissue sheath called the Glisson’s capsule. 
  • The bile secreted by the hepatic cells passes through the hepatic ducts and is stored and concentrated in a thin muscular sac called the gall bladder. 
  • The duct of the gall bladder (cystic duct) along with the hepatic duct from the liver forms the common bile duct.
Functions of the Liver: 
  • Produces bile: bile contains bile salts (emulsify fats and lipids), cholesterol and bile pigment (bilirubin and biliverdin)
  • Bile prevents decay of food in the gut.
  • Produces various blood clotting factors and plasma proteins.
  • Detoxify the blood and kills blood born pathogen (phagocytosis by Kuffer cells).
  • Stores and hence are source of fat soluble vitamins e.g., vita-K
  • Produces no enzymes

 Lobules of liver - Wikipedia

  • The bile duct and the pancreatic duct open together into the duodenum as the common hepato-pancreatic duct () which is guarded by a sphincter called the sphincter of Oddi. 
  • Duct of Wirsung: pancreatic ducts.
  • Ampulla of Vater: the swollen part of the common hepato-pancreatic duct at the joining of the duodenum.
CHAPTER 16 – DIGESTION AND ABSORPTION | Biology for medical ...

The pancreas:
  • The pancreas is a compound (both exocrine and endocrine) elongated organ situated between the limbs of the ‘U’ shaped duodenum. 
  • The exocrine portion secretes an alkaline pancreatic juice containing enzymes and the endocrine portion secretes hormones, insulin and glucagon.


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