Histology - Digestive Glands

Front 1

1.What are the salivary glands and how are they divided?

Back 1

1.Parotid: serous units. Adipose tissue accumulates with age.
2.Submandibular: mostly serous and mixed units.
3.Sublingual: mostly mucous, several mixed units.
Minor: (labial, lingual, buccal, palatine, molar glands) mostly mixed. Very small, surrounded by connective tissue.

Front 2

1.What gland makes most of the saliva?

Back 2

70 percent of saliva is made by the submandibular gland

Front 3

1.What is particular of the duct system of the salivary glands?

Back 3

Intralobular ducts: Ducts inside the lobule of the gland
Intercalated ducts: Connect the lumen of the acinus with the striated duct.
Striated ducts: Large intralobular ducts only found in the salivary glands. Many basal infoldings create their striations.

Front 4

1.What are the functions of the saliva?

Back 4

Lubricant: Mucous and water moistens oral cavity and chewed food.
Sensory: Dissolves taste substances.
Digestive: Salivary amylase and maltase.
Defense: Mechanical disposal of debris; lysozyme, lactoferrin, IgA

Front 5

1.What are the salivary corpuscles?

Back 5

Salivary corpuscles: Desquamated epithelial cells plus white blood cells

Front 6

1.What are the exocrine secretions of the pancreas?

Back 6

The exocrine portion secretes 1500 – 3000 ml per day of an isosmotic alkaline (pH > 8.0) fluid, 20% of which is made of about 20 enzymes and zymogens.

Front 7

1.What does the basal basophilia and apical eosinophiia of the acinar cells represent?

Back 7

Each acinus is made by cells (acinar cells) around an irregular, small lumen. Acinar cells have an outstanding basal basophilia (60% of the membrane system is represented by RER) and apical eosinophilia (secretory granules).

Front 8

1.What is the centroacinar cell?

Back 8

The centroacinar cells line the lumina of the acini and represent the beginning of the duct system. They start the alkalinization of the pancreatic juice.

Front 9

1.What is the meaning of the lack of myoepithelial cells in the pancreas?

Back 9

t the secretion flow is slow and can get stagnant at some point, with the risk of intrapancreatic activation of the enzymes, which can target and destroy the pancreatic tissue, as happens in pancreatitis.

Front 10

1.What is unique of the pancreatic duct system?

Back 10

The pancreas is unique because it has intercalated ducts extended into the acini (centroacinar cells). From here, there will be a gradual transition from simple squamous (centroacinar cells) to cuboidal (outside acini – intralobular ducts) and then columnar epithelium (interlobular ducts).

Front 11

1.How is the pancreatic juice divided?

Back 11

Watery and electrolyte secretion: Mainly made of bicarbonate, plus sodium, potassium, chloride, zinc, phosphate and sulfate.

Enzymatic secretion: Secreted as proenzymes. Amylolytic enzymes (carbohydrates), lipolytic enzymes (fat) and proteolytic enzymes (proteins).

Front 12

1.What is particular about the blood flow of the pancreas?

Back 12

The blood flow in the pancreas actually goes first through the Langerhans islets before reaching the exocrine units.

Front 13

1.What is the interaction of insulin with the exocrine secretion of the pancreas?

Back 13

Insulin may be needed locally for secretin and CCK in order to promote the exocrine secretion

Front 14

1.How are the hepatocytes arranged in the liver?

Back 14

The hepatocytes perform the main hepatic functions. They are arranged in a three-dimensional pattern of 1 (adults) or 2 (children) cells thick plates, with sinusoidal capillaries between the plates.

Front 15

1.What are the portal areas and what structures are found there?

Back 15

portal areas have branches of the structures found at the porta hepatis: 1) An artery; 2) A vein; 3) A bile duct; 4) A lymphatic. The confluence of the central veins creates the suprahepatic vein.

Front 16

1.What is the central vein and in what sense it is related with the suprahepatic veins?

Back 16

The confluence of the central veins creates the suprahepatic vein.

Front 17

1.Explain the classic lobule, portal lobule and the hepatic acinus.

Back 17

Classic lobule: One central vein and three to six portal areas in the vertices of a hexagon. It is still used to describe the morphology of many hepatic diseases.

Portal lobule: With a portal area as center and three central veins in the vertices of a triangle. This model focuses in the bile flow.

Hepatic acinus: Two central veins and two portal areas as vertices of a rhombus. To date is the best model to explain both liver diseases and functions.

Front 18

1.How are the functional zones discerned in the hepatic acinus?

Back 18

Zone 1 receives the blood first, rich in oxygen, nutrients and toxins. The zone 3, closer to the central vein, gets the blood with less oxygen and nutrients (so it is more susceptible to oxygen deprivation).

Front 19

1.What is the limiting membrane and the space of Mall?

Back 19

Around portal areas; hepatocytes arranged in one-cell thick sheet (limiting plate)
Space of Mall: Between the limiting plate and connective tissue of portal space.

Front 20

1.What are the hepatic sinusoids and what cells line them?

Back 20

Receive blood from the portal areas and release it into the central vein, as all capillaries these are low pressure systems with a bigger diameter (9 – 12 µm) and two cells in the lining: Endothelial cells and Kupffer cells

Front 21

1.What is the Disse space?

Back 21

Between endothelial and kupffer cells and the hepatocytes the perisinusoidal space (Disse space) exists.

Front 22

1.Explain the liver circulation regarding the blood origin.

Back 22

Blood from the intestines (venous, 65 – 85 % of the total) brings nutrients to be processed, toxins and pathogens. Blood from the aorta (arterial, 15 – 35 % of the total) brings oxygen and nutrients already processed. The blood leaves the liver through the suprahepatic vein.

Front 23

1.Explain the bile flow and the lymph flow in relation with the blood flow.

Back 23

It flows in the opposite direction respect to the blood flow (toward the porta hepatic). The lymph flows in the same direction as the bile.

Front 24

1.Describe the lymph creation and circulation in the liver.

Back 24

Plasma that does not return to the sinusoid from the perisinusoidal space drains into the space of Mall, and afterwards enters the lymphatic vessel of the portal area, which merges with others and leaves the liver at the porta hepatis to join the thoracic duct. 80 % of the liver lymph follows this pathway, and constitutes most of the lymph in the thoracic duct. The remaining 20% drains into the lymphatic vessels that accompany the hepatic veins.

Front 25

1.What are the hepatocytes?

Back 25

Polygonal cells, 20-35 µm in diameter, with round or oval vesicular nuclei, and different sizes (in adults) that may indicate polyploidy (in the adult up to 25% of the hepatocytes could be binucleated)

Front 26

1.How abundant are mitosis in the healthy adult liver?

Back 26

The mitoses are rare (1 per 15000 cells) in a healthy normal adult liver

Front 27

1.How common is polyploidia in the liver?

Back 27

Up to 25% of the hepatocytes in adult liver

Front 28

1.Explain the three surfaces of the hepatocyte.

Back 28

Basal: Face the perisinusoidal spaces or the connective tissue of portal area
Lateral: In contact with the adjacent hepatocytes
Apical: Form one margin of the bile canaliculus

Front 29

1.Describe the endothelial cells of the liver.

Back 29

These endothelial cells are fenestrated, with large fenestrae (~ 100 nm in diameter) that occupy 6-8% of the cell surface. They are a sieve between sinusoidal lumen and the space of Disse. Perform endocytosis, both specific (transferrin, caeruloplasmin transcobalamine II, glucosaminoglucans, HDL, LDL, procallagen) and nonspecific (pinocytosis).

Front 30

1.What are the Kupffer cells and what are their functions?

Back 30

Highly mobile macrophages attached to the endothelium. They are both phagocytes and antigen-presenting cells. Rather active, they secrete many substances important in phagocytosis and chemical mediation of the immune response, accounting for 5 percent of the protein exported by the organ. They represent the largest population of macrophages in the body.

Front 31

1.What are the Ito cells?

Back 31

Also known as Stellate cells, they lie in the perisinusoidal space and have long cytoplasmic processes that extend below the endothelial cells

Front 32

1.What are the functions of the Ito cells?

Back 32

These modified pericytes have the ability to contract and then modify the diameter of the sinusoid, regulating the blood flow. They have cytoplasmic lipid droplets made of vitamin A (they are actually the major depot of vitamin A in the body).

Front 33

1.What is the relation of the Ito cell with hepatic fibrosis?

Back 33

Certain types of liver injury lead to the loss of the lipid droplets, cellular proliferation and change of the normal appearance of these cells to a myofibroblast-like phenotype: They secrete type I and III collagen and laminin (fibrogenesis); hence they underlie hepatic processes that end in hepatic fibrosis.

Front 34

1.What are the pit cells of the liver?

Back 34

Highly mobile natural killer cells at the sinusoidal surface of the endothelial cells.
Short-lived, renewed from circulating lymphocytes that differentiate in the sinusoids, although they can also locally proliferate. As other NK cells, they show spontaneous cytotoxicity against tumor cells and virus infected hepatocytes.

They are the most active and cytotoxic of the naturally occurring NK cells.

Front 35

1.What are the biliary epithelial cells?

Back 35

They include the ductular cells and those that line the bigger biliary ducts; they secrete bicarbonate-rich solution.

Front 36

1.What is the function of the biliary epithelial cells?

Back 36

they secrete bicarbonate-rich solution.

Front 37

1.What are the bile canaliculi?

Back 37

0.5 – 1.5 µm in diameter channel-type structures created between adjacent hepatocytes (apical surfaces), isolated by tight junctions and are the equivalent to the lumen of the acinus; they connect with the bile duct of the portal space through the ductule (canal of Hering).

Front 38

1.What is the canal of Hering?

Back 38

The ductule between the bile duct, equivalent to the lumen of the acinus

Front 39

1.What type of epithelium lines the bile ducts of the portal areas?

Back 39

Bile ducts of the portal areas (15 – 40 µm) are lined with simple cuboidal epithelium that becomes columnar as they get bigger. The cells have well-developed microvilli. As they become bigger, smooth muscle cells appear.

Front 40

1.What is the relation of the Glisson’s capsule with the connective tissue of the portal spaces?

Back 40

Glisson’s capsule surrounds the organ, enters it in the porta hepatis, and continues as the connective tissue of the portal spaces

Front 41

1.What is the importance of the reticular fibres in the hepatic sinusoids?

Back 41

perisinusoidal space is scant, with reticular fibres that supports the liver parenchyma and keeps the sinusoids open.

Front 42

1.What is the sphincter of Boyden?

Back 42

The sphincter of Boyden is a thickening of the muscle at the end of the common bile duct

Front 43

1.What is the sphincter of Oddi?

Back 43

he sphincter of Oddi regulates flow through the ampulla of Vater.

Front 44

1.What is the gallbladder?

Back 44

Blind, pear-shaped 8 x 4 cm (3 x 1.5 in), very elastic diverticulum of the common hepatic duct, connected to it through the cystic duct.

Front 45

1.What type o epithelium lines the gallbladder?

Back 45

lined by simple columnar epithelium with microvilli and basal infoldings.

Front 46

1.What are the Rokitansky-Aschoff sinuses?

Back 46

Deep invaginations of the mucosa of the gallbladder

Front 47

1.What is the spiral valve of Heister?

Back 47

Spiral valve of Heister is a spiral fold of the mucosa inside the neck of the gallbladder.

Front 48

1.What are the functions of the gallbladder?

Back 48

Functions: Storage and concentration of bile (~ 1500 ml of bile secreted every day, and reduced to just 100 ml by the gallbladder); chloride and bicarbonate are actively absorbed by the gallbladder epithelium.