1.2.3 GI Histology II

Question 1

Liver – largest gland in the body, performing multiple complex exocrine and endocrine functions
- Functions include secretion of bile, synthesis of plasma proteins, storage of various substances and detoxification of toxins and drugs

• Consists mainly of sheets and trabeculae of hepatocytes – normally one cell thick separated by _______
  o Interspersed portal tracts (structures invested by connective tissues) contain a triad of portal venules, hepatic arteriole and a small bile duct
  o Blood flows from these vascular structures in the portal tracts through the sinusoids into an efferent vessel called the ________ (terminal hepatic venule)
• Scattered lymphocytes and macrophages within the portal tracts but _______________ are usually not seen
• Limiting plate – hepatocytes surrounding border of portal tract
• Afferent blood vessels – portal venule and the ________ in the portal tract
• Efferent blood vessel – central vein (terminal hepatic venule)

o Direction of blood flow is from the portal tract to the central vein via the sinusoids

o Bile flows in the opposite direction from the hepatocytes to the bile ductile in the portal tract

Answer 1

sinusoids;
central vein;
plasma cells and neutrophils ;
hepatic arteriole

Question 2

Liver parenchyma
- Hepatic parenchyma is composed mainly of hepatocytes – polygonal cells with _______ cytoplasm and central round nucleus

• Sinusoids – spaces which run between the cords of hepatocytes, connecting the ________ to the central vein
  o Capillary bed of the liver where supply of nutrients and removal of metabolic products take place
  o Sinusoids are lined by sinusoidal lining cells – endothelial cells with __________, lacking a basement membrane, which help in the exchange of material between the blood and the hepatocytes
  o _______ are present on the inner aspects – part of the monocytic macrophage system derived from the bone marrow, ingesting dead red blood cells and bacteria

Answer 2

eosinophilic;
portal vessels;
fenestrae;
Kupffer cells;

Question 3

• Sinusoids lie adjacent to the hepatocytes but are not in direct contact – separated by a perisinusoidal space, _____________.
  o Site for rapid intercellular exchange, also housing ______________ (which stores Vitamin A) and ______ (NK T lymphocytes)
  o Fine reticulin fibres running in this space – supports hepatic architecture

Answer 3

the space of Disse;
stellate cells of Ito;
pit cells

Question 4

Hepatocytes – show specific surface modifications reflecting its functional activity
- Sinusoidal surface (surface of the hepatocyte facing the sinusoid) shows plentiful __________– important for the absorption of nutrients

• ______ surface – formed when focal depressions on 2 adjacent hepatocytes appose one another, allowing for passage of bile formed within the hepatocyte
• Contain plentiful organelles such as mitochondria, sER, rER, Golgi apparatus and lysosomal bodies and chief inclusions (glycogen and _____)
• These organelles and inclusions reflect the high metabolic function of the hepatocytes, such as glycogenolysis, cholesterol/bile salts synthesis and esterification of fatty acids
  § sER in particular is involved in detoxification of drugs
• Bile is formed in the hepatocytes and exit in the canaliculi to reach the portal tracts via the _______ into the bile ductule

Bile plugs – bile pigments are not normally seen in sections of the liver
o May be seen in jaundice or cholestasis (decrease in bile flow due to impaired secretion by hepatocytes or to obstruction of bile flow through intra or extrahepatic bile ducts)
o Expansion of canaliculi with bile plugs – brown pigmented substance

Answer 4

microvilli; Canalicular; lipid; canal of Herring

Question 5

Stellate cells of Ito – normally contain fat and store ____________

• Activated during liver injury – become proliferative, contractile myofibroblasts that can produce collagen and lead to fibrosis
• After healing – loss of hepatocyte microvilli and ________ affecting the liver function
• The activation of stellate cells in injury is the central event in hepatic fibrosis

Answer 5

Vitamin A; fenestrae

Question 6

Liver cells in the acinus are divided into 3 zones- acinus represents metabolic heterogenity from zone 1 to 3:

• Proximity to vessels: Zone 1 is closer to _____ while zone 3 is closer to _____
• oxygen and nutrient supply is highest in _____
• abundant organelles found in zone 1 is ______ while that found in zone 3 are ______
• zone 1 undergoes oxidative metabolism while Zone 3 undergoes anaerobic metabolism and drug metabolism

Answer 6

afferent vessels; central vein;

zone 1;

Mitochondria; SER and CYP450

Question 7

Gallbladder – inner mucosa lining but no muscularis mucosae and villi
- The function of the gallbladder is to store and concentrate bile with the absorption of water

o Mucosa – __________ epithelium with striated microvilli border, no goblet cells or _________

o Submucosa is absent

o _________ coat – underlying smooth muscle coat consists of loosely arranged bundles of circular, longitudinal and oblique muscles (absence of proper muscularis propria)

o Outer serosa – surrounds other layers

Answer 7

columnar; muscularis mucosae and villi; Fibromuscular

Question 8

Pancreas – lobules in the pancreas are composed of highly cellular glandular tissues, comprised of pancreatic acini, pancreatic ducts and scattered islets of Langerhans

• Acinar cells are the main component of the pancreas and the secretory component of the exocrine pancreas – secreting digestive enzymes into ducts
  o Arranged in acini and tubular configurations with minimal fibrous tissues in lobules
  o Abundant granular pink cytoplasm (especially apically where the _____________ are concentrated), basophilic basal cytoplasm with numerous rER and basal nucleus
  o Stacks of ______ with mitochondria situated around the nuclei basally and zymogen granules apically
  o Various enzymes in the proenzyme forms are present – trypsin, chymotrypsin, lipase, amylase and elastase
• Pancreatic ducts transport the pancreatic acinar secretions to the duodenum
  o Ductal epithelial cells secrete water, chloride and bicarbonate to buffer the acidic pancreatic secretions and stabilise the proenzymes until activation
  within the duodenum
  o The ductal system has 5 divisions – centroacinal cells (centre of acini), __________ (smallest ducts outside acini), intralobular ducts, ________ and the main ducts
  § Larger ducts are surrounded by a thick coat of _________.

Answer 8

zymogen granules; rER; intercalated ducts; interlobular ducts; collagen