Accessory organs of the GI tract

Question 1

what are the three main digestive glands and what are their properties

Answer 1

Have lubricating , protective, digestive, and absorptive functions mediated by their secretory products

Major salivary glands: associated with the oral cavity through independent excretory ducts

Exocrine pancreas: secretes its alkaline aqueous and enzymatic product into the duodenum

Liver: endocrine and exocrine gland with extensive access to the blood circulation

Question 2

Histology of the salivary gland and its characteristics

Answer 2

CT capsule with septa dividing the gland into lobes and smaller lobules
-route for neurovasculature

secretory cells organized in an acinus produce saliva via ANS control

released via ducts: acinus to the intercalated duct and through striated duct and finally out the excretory duct

Question 3

differences histology between the mucous, serous, and mucoserous acini

Answer 3

Mucous acini are cloudier looking cytoplasm that produce thick glycoprotein rich product

Serous acini: clear staining cytoplasm that produce a water based product

Mucoserous: contain a core of mucous (black) cells surrounded by a serous demilune (yellow)

Question 4

what are myoepithelial cells?

Answer 4

located between epithelial cells and basal lamina that assist in moving secretory products toward the excretory duct

Question 5

what is the pathway flow of saliva?

Answer 5

Acinus

intercalated duct
-low cuboidal epithelium

striated duct
-simple cuboidal to columnar epithelium

excretory duct
-simple cuboidal to pseudostratified columnar or stratified cuboidal

Question 6

which glands have the longest/shortest: intercalated duct, striated duct, and exretory duct

Answer 6

parotid: longest intercalated duct but shortest excretory duct
submandibular: longgest striated duct, shortest intercalated duct
sublingual: longest excretory and shortest striated duct

Question 7

characteristics of the parotid gland

Answer 7

Largest salivary gland, adipocytes may be present

Acini consist primarily of serous secretory cells

• pyramidal cells with a basally located nucei
• prominent RER in basal region
• secretory granules visible in apical region

can sometimes see the CN VII pass through

Question 8

Characteristics of the sublingual gland

Answer 8

Branched tubule-alveolar gland with both serous and mucous cells
-mixed gland but predominatly mucous

lacks defined capsule, but is divided by CT into small lobes
Interca;ated and striated ducts poorly developed

Question 9

Characteristics of the Submandibular gland

Answer 9

Serous cells are predominant but mucous cells are present

mucous cell containing acini are capped by serous demilunes
-intercalated ducts are shorter and striated ducts are longer than in the parotid gland

Question 10

what are the two components of the pancreas and what are some of its main features

Answer 10

Large gland with endocrine and exocrine functions but bulk gland is exocrine

THin layer of loose CT forms capsule

Divides gland into ill defined lobules, neurovasculature and ducts extend within the septa

Exocrine component: synthesizes/secretes enzymes that are essential for digestion in the intestine

endocrine component: synthesizes/secretes hormones into the blood that regulate the glucose, lipid, and protein metabolism

Question 11

Characteristics of the exocrine pancreas

Answer 11

Serous acinus = functional unit of exocrine pancreas and structurally unique
-contains pancreatic acinar cells

intercalated duct begins within the acinus centroacinar cells, duct cells inside the acinus

• continuous with the low cuboidal epithelium of intercalated duct
• cells secrete HCO3-, Na+ and H20 and alkalinizes secretions

acinar cells stain intensely, centroacinar cells stin lightly

Question 12

function and characterization of the Pancreatic acinar cell

Answer 12

Characterization:

• well developed RER
• prominent golgi apparatus
• apical domain of zymogen granules

Granules contain 20 different pancreatic enzymes

• trypsinogen, chymotrypsinogen digest proteins
• amylolytic enzyme a-amylase digest carbohydrates
• deoxyribonuclease, ribonuclease digest Nucleic acids

increase synthesis of proteases with protein rich diet

increase of amylases and decrease of proteases with a carbohydrate rich diet

Question 13

Characteristics of the Endocrine pancreas and the 4 cell types

Answer 13

Spherical masses of endocrine cells surrounded by thin reticular capsule

Most islets contain several hundred cells, pancreas hs more than 1 million islets

islets arise from endodermal epithelial outgrowths

Islet cells:

• alpha cells = glucagon
• beta cells = insulin
• delta cells = spmatostatin
• PP cells - pancreatic peptide

Question 14

Characteristics and the cells that make up the liver

Answer 14

Enclosed in thin CT capsule lined with mesotheilum of visceral peritoneum

lacking where directly adheres to the diaphragm or other organs

Hepatocytes: function in metabolism, storage, bile, production (exocrine)
-arranged in cellular cords

liver structure varies in regard to its functional unit:

• hepatic lobule
• portal lobule
• liver acinus

Question 15

Characteristics of hepatocytes and bile

Answer 15

Large polygonal cells with eosinophillic cytoplasm and microvilli
Large spherical nuclei, many cells are binucleate, most are tetraploid
Numerous perioxisomes, lysosomes, extensive sER, large golgi

Hepatocytes secrete bile, mixture of H2O, bile salts and pigments, phospholipids, electrolytes
-drains into bile canaliculus which is a canal lined with cholangiocytes, located btwn adjacent hepatocytes

canaliculi join to eventually contribute to biliary tree

Bile functions in fat absorption and excretion of cholesterol, bilirubin, iron and copper

Question 16

what make up the hepatic lobules and what is apart of the portal triad?

Answer 16

Liver parenchyma are organixed as hepatic lobules

• hepatocytes from irregular plates radiating from a central vein
• plates are supported by a stroma or reticular fubers
• plates separated by sunusoids

Blood flows toward the central vein

Peripheral angles of each lobe contain a portal triad”

• Venule branch of the portal vein (high in nutrients and low in O2)
• arteriole branch of the hepatic artery supplies O2
• Bile ductules (1-2) branches of the bile conducting system

blood and bile flow in opposite directions

Question 17

what are the hepatic sinusoids and what are the two cell types found among them

Answer 17

Anastomosing capillaries that perfuse hepatocytes with portal and arterial blood

Kupffer cell:

• stellate macrophages within the endothelium of the sinusoid
• larger than the endothelial cells
• detect and phagocytose effete erythrocytes
• distinguishes the hepatic sinusoids

Hepatic stellate cells: Ito cells, cells with small lipid droplets that store vitamin A and other fat soluble vitamins

Question 18

what is the perisinusoidal space of Disse

Answer 18

Located between the hepatocytes and sinusoidal endothelium (discontinuous capillaries)

Creates a potential space for exchange of materials between blood and hepatocytes

• microvilli project into this space
• plasma fills the space and directly bathes microvilli
• increase SA available for material exchange

Facilitates uptake/release of nutrients proteins and potential toxins

Question 19

what are the bile canaliculi and how does bile flow

Answer 19

Anastomosing network of channels formed by the hepatocyte plates
-end near the portal triads

Bile flow occurs from center of the lobule to the periphery
-bile canliculi drain into canals of hering, composed of cuboidal epithelial cells caled cholangiocytes

bile flow:

• baile canaliculi
• canals of hering
• bile ductiles
• merge and enlarge
• right and left hepatic ducts

Question 20

what is a portal lobule

Answer 20

Central axis is the bile duct (portal triad)

ID portal triad and draw imaginary lines btwn 3 central veins

• triangular block of tissue
• outlines bile drainage pathway from adjacent lobules into the same bile duct

Provides a description comparable to that of other exocrine glands

Question 21

What is the liver acinus

Answer 21

Diamond shaped and occupies parts of adjacent classic lobules

Hepatocytes are arranged in concentric zones around short axiis

Based on O2 concentration gradient along sinusoids of adjacent lobules

Cells within each zone have different metabolic functions and distribution of hepatic enzymes
-explains distribution of liver damage resulting of ischemia and or exposure to toxic substances

level 1: most nutrients and and O2
level 3 = least

Question 22

what is the structure and function releastionship of the 3 different lobules

Answer 22

Classic lobule: emphasizes endocrine function of hepatocytes as blood flows toward central vein

Portal lobule: emphasizes hepatocytes exocrine function and flow of bile from the classic lobules toward bile duct in portal triad
-triangular

Hepatic acinus: emphasizes different ozygen content and nutrient content of blood at different distances along the sinusoid

• activity determined by nutrient concentration
• level 1 = most nutrients
• level 3 = least nutrients

Question 23

characteristics of the gall bladder

Answer 23

Sac like structure that stores and concentrates bile

Releases it into the duodenum after a meal

Highly folded mucosa with a simple columnar epithelium with microvilli overlying the lamina propria

muscularis with bundles of muscle fibers orientated in al directions to facilitate emptying of the organ

External adventitia is where it is against the liver but serosa where it is supposed to the peritoneal cavity

Question 24

What are Rotikansky-Aschoff sinuses?

Answer 24

deep diverticua of the mucosa that may extend through the muscuaris externa

develop as the result of hyperplasia and herniation of epithelial cells through the muscuaris externa

Bacteria may accumulate causing chronic inflammation and increased risk for gallstones