Digestive Glands Lecture (Test 1)

Question 1

Digestive Glands

Answer 1

• Have LUBRICATIVE, PROTECTIVE, DIGESTIVE

Question 2

Classifications of Exocrine Glands

Answer 2

A) Structure of the Excretory Duct:
- Divided into SIMPLE (Unbraced Duct) and BRANCHED or COMPOUND (Branched Duct)

B) Structure of the Secretory Units:
- Classified as TUBULAR or ALVEOLAR (Acinar)

C) Secretory Product:
- MUCOUS or SEROUS (Watery fluid with Zymogen or Proenzyme Granules)

D) Secretory Mechanism:

• MEROCRINE (Exocytosis)
• HOLOCRINE (Whole Cell)
• APOCRINE (Gland releases its products together with a Small Amount of the Apical Cytoplasm of the Secretory Cell

Question 3

Major Salivary Glands

Answer 3

• The Parotid, Submandibular (or Submaxillary), and Sublingual Glands are classified as Branched TUBULOALVEOLAR Glands
• Their Excretory Ducts open into the ORAL Cavity
• SALIVA

Question 4

Functions fo Saliva

Answer 4

• The mucus and Water is Saliva LUBRICATE the Mucosa of the Tongue, Cheeks, and Lips during Speech and Swallowing, dissolve food for the function of the Taste Buds, and MOISTEN FOOD for easy Swallowing
• The PROTECTIVE FUNCTION of the Saliva depends on the Antibacterial Function of three constituents of Saliva:
  1) LYSOZYME
• Attack the Walls of Bacteria

2) LACTOFERRIN
- Chelates Iron necessary for Bacterial Growth

3) IgA
- Neutralizes Bacteria and Viruses

• The DIGESTIVE FUNCTION of Saliva relies on:
  1) Amylase
• Initiates the Digestion of Carbohydrates in the Oral Cavity

2) Lingual Lipase
- Participates in the Hydrolysis of Dietary Lipids

Question 5

Multifunctional Enzymes

Answer 5

1) Antibacterial
- Amylases
- Cystitis
- Histamines
- Mucins
- Peroxidases

2) AntiViral
- Cystatins
- Mucins

3) AntiFungal
- Histamines

4) Tissue Coating
- Amylases
- Cystitis
- Mucins
- Proline-rich Proteins
- STATHERINS

5) Lubrication and Viscoelasticity
- Mucins
- STATHERINS

6) Mineralization
- Cystatins
- Histatins
- Proline rich Proteins
- STATHERINS

7) Digestion
- Amylases
- Mucins
- Lipases

8) Buffering
- Carbonic Anhydrases
- Histatins

Question 6

Salivary Glands

Answer 6

PAROTID:
- Exclusively SEROUS ACINI

SUBMANDIBULAR GLAND:

• Mixed Serous and Mucus
• SEROUS DEMILUNES
• Pure Mucus ACINI RARE!!!!!!!

SUBLINGUAL GLAND:

• Mixed SERUOS and MUCUS
• Mucus ACINI Predominate

Question 7

Parotid Glands

Answer 7

A) Enzymes:

• Amylase
• Peroxidase
• Lysozyme

B) Antimicrobial proteins including Proline-rich Proteins, Histamines, Cystitis, and STATHERIN have Important implications for Bacterial Clearance, Selective Bacterial Aggregation on the Tooth Surface, and Control of Mineralization and Demineralization

Question 8

Clinical Significant: Mumps, Rabies, and Tumors

Answer 8

• The Parotid Gland is the PRIMARY TARGET of the Rabies and Mumps virus transmitted in Saliva containing the Virus
• The Mumps virus causes TRANSIETNT Swelling of the Parotid Gland and confers Immunity.
• Two Complications of Mumps are ORCHITIS and MENINGITIS
• Bilateral ORCHITIS caused by the Mumps Virus can result in STERILITY
• The Parotid Gland is the most frequent site for Slow-Growing BENIGN SALIVARY GLAND TUMORS. Surgical removal is complicated y the need to protect the FACIAL NERVE

Question 9

Submandibular Gland

Answer 9

• Mucous Cells secrete MUCIN which aids in the LUBRICATION of the Food Bolus as it travels through the Esophagus
• In addition, the Serous Cells produce SALIVARY AMYLASE

Question 10

Sublingual Gland

Answer 10

• The Sublingual Gland is a Branched Tubuloalveolar Gland with BOTH SERUOS and MUCOUS Cells
• Most SECRETORY Units are MUCOUS
• Exit DIRECTLY from 8 to 20 Excretory Ducts

Question 11

Exocrine Pancreas

Answer 11

• The Pancreas is a combine ENDOCRINE and EXOCRINE Gland
• The Endocrine component is the ISLET OF LANGERHANS and represents about 2% of the Pancreas Volume
• The MAIN FUNCTION of the Endocrine Pancreas is the REGULATION OF GLUCOSE METABOLISM by HORMONES SECRETED INTO THE BLOODSTREAM!!!!
• The Functional Unit of the Exocrine Pancreas is the ACINUS!!!!!
• the Lumen of the Acinus is the INITIATION of the Secretory- Excretory Duct System and contains CENTROACINAR Cells the are unique to the PANCREAS
• CENTROACINAR Cells are continuous with the Low Cuboidal Epithelial lining of the Intercalated Duct
• The EXOCRINE PANCREAS lacks STRIATED Ducts and MYOEPITHELIAL Cells
• INTERCALATED Ducts converge to form INTERLOBULAR DUCTS lined by a Columnar Epithelium with a few GOBLET CELLS and occasional ENTEROENDOCRINE Cells

Question 12

Exocrine Pancreas Cont

Answer 12

• ZYMOGEN GRANULES are present at the Apical portion of the PANCREATIC ACINAR Cell!!!
• CENTROACINAR Cells are SPINDLE-SHAPED Cells in the Pancreas. They are also knowns as Duct Cells and secrete AQUEOUS BICARBONATE Solution under simulation by the Hormone SECRETIN. They also Secrete MUCIN!!!!

Question 13

Pancreatic Secretinos

Answer 13

• The Gastrointestinal Hormones CHOLECYSTOKININ (CCK) and SECRETIN Increases the flow of Pancreatic Fluid (About 1.5 to 3.0 L/ day)
• CCK, produced in ENTEROENDOCRINE Cells of the DUODENAL Mucosa, binds to SPECIFIC RECEPTORS of ACINAR Cells and stimulate the RELEASE of ZYMOGENS

Question 14

Enteroendocrine Cells

Answer 14

A) ACINAR PANCREATIC CELLS:
- Secrete the INACTIVE FORMS of the Enzymes Trypsin, Chymotrypsin, and Carboylpeptidases. Active Amylase, Lipase, Cholesterol Esterase, and Phospholipase are also secreted

• Acinar Pancreatic Cells secrete TRYPSIN Inhibitor, which prevents the Activation of Trypsin and other Proteolytic enzymes within the Acinar Lumen and Ducts

B) VAGAL STIMUALTION:
- Vagal Stimulation results in the release of ACETYLCHOLINE which, in turn, triggers the release of Enzymes into the Acinar Lumen

C) SECRETIN FUNCTION (On Duct Cells):
- Causes the Release of HCO3- ions and the Alkaline Secretion of Brunner’s Glands, present in the Submucosa of the Duodenum, Neutralize the Acidic Gastric Chyme in the Duodenal Lumen and Activate the Pancreatic Digestive Enzymes

Question 15

Pancreatic Secretions

Answer 15

• The concentration of about 20 different Pancreatic Enzymes in the Zymogen Granules varies with the dietary intake
• Increase in the SYNTHESIS of PROTEASES is associated with a Protein-Rich Diet
• A Carbohydrate rich diet results in the SELECTIVE Synthesis of Amylases and DECREASES in the Synthesis of PROTEASES
• AMYLASE Gene Expression is regulated by Insulin, so the Internal Circulation within the Pancreas (Insuloacinar Portal System) in functionally VERY IMPORTANT

Question 16

Acute Pancreatitis

Answer 16

• Zymogen Granules contain INACTIVE PROENZYMES that are activated within the Duodenal Environment
• A Premature Activation of Pancreatic Enzymes (trypsinogen to Trypsin) and the Inactivation of Trypsin Inhibitor result in the AUTODIGESTION of PANCREATIC ACINI
• This condition usually follows Heacy Meals or Excessive Alcohol Ingestion
• The Clinical features of Acute Pancreatitis are SEVERE Abdominal Pain, Nausea, Vomiting, and Rapid Elevation of AMYLASE and LIPASE in Serum (Within 24 to 72 Hours)

Question 17

Liver

Answer 17

• Largest Gland in the Body
• Blood is supplied to the Liver by:
  1) PORTAL VEIN (75 to 80% of Afferent Blood Volumes)
  a) Transport Blood from GI Tract, Spleen, and Pancreas

2) HEPATIC ARTERY ( 20 to 25% of Oxygenated Blood ) to Liver via Interlobar and Interlobular Arteries
- Blood from branches of the Portal Vein and the hepatic Aftery mixes in the Sinusoids of the Liver Lobules and converges at the Central Venule of the Liver Lobule
- Central Venues converge to form the Sublobular Veins, and Blood return to the INFERIOR VENA CAVA following the Collecting Veins and Hepatic Veins pathway

Question 18

Hepatic Lobule

Answer 18

• the Structural and Fuctional unit of the Liver is the HEPATIC LOBULE
• The Hepatic Lobule consists o fAnastomosing plates of HEPATOCYTES limiting Blood Sinusoidal Spaces
• A CENTRAL VENULE (or Vein) in the core of the Hepatic Lobule collects the Sinusoidal Blood containing a mixture of Blood supplied by branches of the Portal Vein and the Hepatic Artery

Question 19

” Functional” Units

Answer 19

• The Liver lobule can be conceptualized as:
  1) The CLASSIC HEPATIC LOBULE
  2) The PORTAL LOBULE (Based on the Bile Drainage Pathway; the Portal Triad is at the CENTER of the Portal Lobule)
  3) The LIVER ACINUS (Based on the Zone Gradient Distribution of Hepatic Artery- derived Oxygenated Blood along the Sinusoidal Spaces)

Question 20

Classic Hepatic Lobule

Answer 20

• Hexagonal lobule
• Surrounding a CENTRAL VEIN
• Portal Triads at the ANGLES

Question 21

Portal Lobule

Answer 21

• Triangular Arrangement
• Center of the Triangle is Bile Duct Collecting from THREE HEPATIC LOBULES
• Angles are the CENTRAL VEINS of THREE Hepatic Lobules

Question 22

Liver Acinus

Answer 22

• Based on the Oxygen Gradient of VENOUS SINUSOIDS of Adjacent Lobules
• Divided into 3 zones based on the blood Supply to the Hepatocytes from the Branch of the Hepatic Artery

Question 23

Microscopic Structure of Lobule

Answer 23

• made mostly of HEPATOCYTES arranged in Thin Layers that Radiate from the CENTRAL CANAL VEIN to the PERIPHERY of the LOBULE
• between the Radiating Rows of Hepatocytes are small Blood Vessels called SINUSOIDS
• These receive Oxygen-rich Blood from the HEPATIC Artery and nutrients from the Intestines via the PORTAL VEIN
• The Oxygen and Nutrients DIFFUSE through the Capillary Walls into the Liver Cells

Question 24

Microscopic Structure of Lobule Cont

Answer 24

• Within the SINUSOIDS are Specialized Macrophages (KUPFFER CELLS) involved in the Recycling of Old Red Blood Cells
• At the corner of each Lobule is the POTAL TRIAD, Composed of Branches of the Hepatic Portal Vein, Hepatic Artery, Bile Duct, and nerve
• BILE drains from the Hepatocytes by the many small Bile Ducts that UNITE to form the MAIN Bile Duct of the Liver, the HEPTIC DUCT!!!
• this joins the CYSTIC DUCT, which leads from the Gallbladder, to form the Common Bile Duct, which drains into the DUODENUM

Question 25

Space of Disse

Answer 25

- The Endothelium which lines Liver Sinusoids is FENSRATED and LACKS a CONTINUOUS Basement Membrane (Discontinuous Capillaries) - The Space between the FENESTRATED Endothelium and the cords is names the SPACE OF DISSE - The Fenestrations permit blood Plasma to Wash freely over the EXPOSED Surfaces of the Hepatocytes through the Space of Disse - Microvilli of Hepatocytes extend into this space. allowing protein and other Plasma components from the Sinusoids to be absorbed by the Hepatocytes Space of Disse: - Space between Basement Membrane of Endothelial Cells and Hepatocytes Sinusoid: - Contains blood with erythrocytes Bile Canaliculus: - Hepatocytes Secrete Bile

Question 26

Ito Cells (Hepatic Stellate Cells)

Answer 26

- Ito Cells are STELLATE CELLS of the Liver, located at Intervals within the Space of Disse - These cells function as storage sites for FAT and VITAMIN A

Question 27

Bile

Answer 27

- Produced by Hapetocytes - Flows in the OPPOSITE Direction to the Blood - Blood is Transported through BILE CANALICULI into the CANAL OF HERING (or Cholangiole), and then into the Bile Duct in the PORTAL TRIAD SPACE

Question 28

Hepatocytes

Answer 28

- Functional ENDOCRINE and EXOCRINE Cell of the Liver - Has a Basolateral Domain with ABUNDANT MICROVILLI extending into the SPACE OF DISSE - The BASOLATERAL DOMAIN participates in the ABSORPTION of Blood-Borne substances (For Ex, Bilirubin, Peptide and Steroid Hormones, Vitamin B12, and substances to be Detoxified), and the SECRETION of Plasma Proteins (For Ex, Albumin, Fibrinogen, Prothrombin, Coagulation Factors, and Complement Proteins) * **BASOLATERAL DOMAIN: - Towards the SPACE of DISSE!!!

Question 29

Hepatocytes Cont

Answer 29

- Hepatocytes contain SMOOTH ENDOPLASMIC RETICULUM (SER) associated with Glycogen inclusions Function of SER Include: 1) Synthesis of Cholesterol and Bile Slats 2) Glucuronide conjugation of Bilirubin, Steroids, and Drugs 3) The Breakdown of Glycogen into Glucose 4) The DETOXIFICATION of Lipid-soluble Drugs (Ex, Phenobarbital) 5) - The Rough Endoplasmic Reticulum and Golgi Apparatus participate in the Synthesis and Glycosylation of the SECRETORY Proteins indicated above - PEROXISOMES are PROMINENT in Hepatocytes (Gener

Question 30

Bile Cont

Answer 30

- Bile is a mixture of Organic and Inorganic Substances produces by the Hepatocyte - Bile participates in the EXCRETION of Cholesterol, Phospholipids, Bile Salts, Conjugated Bilirubin, and Electrolytes - FAT Absorption in the Intestinal lumen depends on the Fat-Emulsifying Function of Bole Salts - Bile Transports IgA to the Intestinal Mucosa (Enterohepatic Circulation), and inhibits Bacterial Growth in the Small Intestine - The Secretion of Bile into the BILE CANALICULUS is an ATP- mediated process involving MULTIDRUG RESISTANCE 1 and 2 Transporters (MDR1 and MDR2), multi specific Organ Anionic Transporter (MOAT), and Biliary Acid Transporter (BAT)

Question 31

Metabolism of Bilirubin

Answer 31

- Bilirubin is the end product of HEME CATABOLISM - About 85% of Bilirubin originates from SENESCENT Red Blood Cells destroyed in the SPLEEN by Macrophages - Macrophages convert Heme into Biliverdin, which is transformed into UNCONJUGATED Bilirubin released into the Blood Circulation - In the Blood Circulation, Bilirubin forms a Complex with ALBUMIN - When the Bilirubin-Albumin Complex reaches the HEPATIC SINUSOIDS, Albumin detaches and Bilirubin is Internalized by the Hepatocyte

Question 32

Alcoholism and Fatty Liver

Answer 32

- Hepatocytes participate in the Metabolism of Ethanol - Long term consumption of Ethanol results in FATTY LIVER - This is a REVERSIBLE Process is Alcohol ingestion is DISCONTINUED a) Cirrhosis: Collagen proliferation of Fibrosis of the Liver b) Hepatocellular Carcinoma: Malignant transformation of the Hepatocytes

Question 33

Gallbladder

Answer 33

- The Main Function of the Gallbladder are: 1) Storage 2) Concentration 3) Release of Bile - Dilute Bile from the Hepatic Ducts in transported through the Cystic Duct into the Gallbladder - After Concentration, Bile is discharged into the COMMON BILE DUCT ***The Mucosa displayed MULTIPLE Folds lined by SIMPLE COLUMNAR EPITHELIUM supported by a LAMINA PROPRIA with VASCULAR-LYMPHATIC PLEXUS. The Mucosa creates Deep Clefts known as RKITANSKY-ASCHOFF CRYPTS or Sinuses!!!!!!!