Lecture 21: Digestive System 2 Flashcards
Saliva contains
Water, salts, mucin, enzymes (amylase, maltase, lipase), IgA, lysosome, lactoferrin, and suspended cells (desquamated epithelial cells, leukocytes, bacteria)
4 functions of saliva
- Digestion
- Provide moisture and lube
- Participates in local immunity
- Provides evaporative cooling
Major salivary glands
- Parotid
- Sublingual
- Submandibular
Minor salivary glands
- Lingual
- Palatal
- Labial
- Buccal
- Zygomatic (carnivores)
- Molar (cats)
Three types of secretions in salivary glands
- Serous
- Mucus
- Mixed
Stroma (large salivary glands)
- Connective tissue capsule and trabeculae
- Blood vessels and lymph vessels
- Nerves and intramural ganglion
Parenchyma (large salivary glands)
- Adenomeres as secretory units
- Ducts (intercalated, intralobular/striated, interlobular)
Largest visceral organ, weighing 1-4% body weight
liver
Dual blood supply of the liver sinusoids
- 70% to 80% of blood comes from the portal vein
- Smaller amount supplied by the hepatic artery, blood rich in O2
Each lobe of the liver is covered by
mesothelium located over a CT layer known as the capsule of glisson
Hepatocytes
Parenchymal cells arranged in plates with adjacent sinusoids
Plates in liver are organized into
hepatic lobules
Chylomicrons are mainly transported by
lymph vessels
Exocrine secretion of the liver that is important for the digestion of lipids
Bile
Two poles of hepatocytes
Bile pole
Vascular
Hepatic sinusoid
fenestrated capillary (without diaphragms, do not have basal lamina).
Lipids and carbs are stored on the liver in the form of
triglycerides and glycogen
Hepatocyte function
Supplies body with energy between meals
What are seen at the edges of the hepatic lobule
Portal tract with a branch of the hepatic artery, branch of the portal vein, and bile ductules
Blood from portal area enters _____ and…
sinusoids and flows towards central vein
Blood leaves liver via
hepatic vein to the caudal vena cava
Where are Kupffer cells (macrophages) located in the liver
adjacent to the sinusoids
Bile in cannuli flows
in opposite direction to the blood to reach bile ductules within the portal triads
Structural unit of classical liver lobule
hepatic lobule
Shape of hepatic lobule
Hexagonal (polyhedral)
What is the axis of the hepatic lobule
central vein
Blood flows towards what in the hepatic lobule
towards axis
Physiological unit of liver
Portal lobule
Shape of portal lobule
triangular
Axis of portal lobule
Portal area (triad)
Bile flows towards where in portal lobule
axis
Hepatic acinus
The vascular flow pattern between lobules
Hepatic acinus pattern
Begins at triad, flows towards central veins via sinusoidal capillaries
Hepatocytes nearest to central vein receive blood ____ in O2, ____ to be damaged if vascular compromise exists
lowest
first
Zone 1 of hepatic acinus
- High O2
- High nutrients
- High pathogen exposure
Zone 2 of hepatic acinus
- Moderate O2
- Moderate nutrients
- Moderate pathogen exposure
Zone 3 of hepatic acinus
-Low O2, nutrients, and pathogen exposure
Gallbladder accepts
bile from cystic duct for storage
When gallbladder is empty, what is seen?
Abundant mucosal folds
Gallbladder structure
Simple columnar epithelium that has microvilli, tight junctions, mitochondria, and secretory vesicles
Epithelial cells in the gallbladder are capable of modifying bile by
concentrate it by absorption of H2O and inorganic salt
Does the gallbladder have a lamina muscularis mucosae?
Nope
What surrounds almost the entirety of the gallbladder
Tunica serosa
Exocrine pancreas is composed of
tubuloacinar secretory units
Tubuloacinar units of the pancreas drain into
intercalated ducts lined by cuboidal cells
Pancreas resembles a serous salivary parotid gland, from which it differs in that
- Pancreas has no striated ducts
- The duct system in pancreas is less developed
- Pancreas has endocrine pancreatic islets of Langerhans
Two parts of the pancreas
- Stroma
2. Parenchyma
Stroma of pancreas
Thin CT capsule + trabeculae with blood vessels, lymph vessels, and nerves (pacinian corpuscles)
Endocrine and exocrine percentages of parenchyma in pancreas
5% endocrine
95% exocrine
Secretory part of pancreas
Acinar cells
Centroacinar cells