- in the exocrine portion of the pancreas, these cells are organized into acini like the parotid gland

Serous cells

- inside acini these cells mark the beginning of the duct system

Pale centroacinar cells

- follow the centroacinar cells and drain exocrine acini a short distance to join intralobular ducts

- from simple squamous to cuboidal

Intercalated ducts

- follow intercalated ducts

- lined by cuboidal to columnar mucus-secreting cells

Intralobular ducts

- come from intralobular ducts

- their thick connective tissue walls provide primary support for the pancreatic duct system

Interlobular ducts

-inactive lipases, amylases, proteases, and nucleases which are activated by enterokinases on the intestinal brush border glycocalyx

- stored in zymogen granules until stimulated to release

Proenzymes (zymogens)

- produces fluid and bicarbonate by way of apical Cl-HCO3 exchanger that uses the cystic fibrosis transmembrane conductance regulator (leads to CF pancreatitis)

Pancreatic duct cells

- secrete constitutively at a low level but can increase secretion by way of CCK and Ach receptors

- other receptors also present

- also produces watery bicarb-rich secretion

Pancreatic acinar cells

- primary stimulus of pancreatic acinar cells for production of the bicarb-rich watery secretion

Secretin

- appear as single cells and in identifiable unencapsulated clusters (islets of Langerhans)

- islets have a core of B cells and a mantle of A

- more numerous in tail than in the head

Endocrine cells of Pancrease

- produce glucagon (raises blood glucose level)

- generally peripheral in the islet

- produce insulin (lowers blood glucose)

- most common of the islet cells

- located centrally in the islet

B (beta) cells

- produce somatostatin

- 3rd most common of the islet cells

- scattered but generally peripheral in the islet

D (delta) cells

- produce pancreatic polypeptide

- scattered throughout islet

F cells (PP)

- these facilitate communication between islet cells following neural (para & sympathetic) or hormonal stimuli

Gap junctions

- these perfuse A & D cells before reaching B cells

- after leaving the islets the blood perfuses adjacent acinar cells (mini-portal system)

Fenestrated capillaries

- has many irregular folds

- spiral valves at neck control bile

- mucus-secreting simple columnar epithelium

- no true muscularis mucosa or submucosa

- thin, irregular muscularis

- adventitia covered by serosa or liver

- concentrates bile about 10 times, adds mucus, storage

Gallbladder

- hormone that controls Gallbladder secretion/contraction

cholecystokinin

- capsule of the liver

- thin CT layer w/ mesothelium covers all but bare area

Glisson's capsule

- CT follows portal vein, hepatic artery, bile duct triad

- reticular fibers form network of support fo parenchymal cells

Liver Stroma

- composed primarily of hepatocytes arranges in plates called sinusoids

- has perisinusoidal space of Disse

- Kupffer and stellate cells present

- blood via portal vein/hepatic artery --> terminal hepatic venule

- bile exits via canaliculi into canals

Parenchyma of Liver

- the space found between sinusoidal endothelial cells and hepatocytes

perisinusoidal space of Disse

- route of this substance

- parenchyma --> canaliculi --> canals of Hering --> bile ducts in portal areas

Bile

- bile canaliculi formed by these and are sealed by tight junctions

hepatocytes

- simple cuboidal epithelium

- becomes simple columnar in larger ducts and resembles gallbladder epithelium

Biliary system epithelium

- portal areas surrounding a terminal hepatic venule (central vein)

Classic lobule

- connect the portal areas between the hepatocytes to the central veins

- lined with a discontinuous endothelium and local areas of fenestrations termed sieve plates

sinusoids

- in contrast to the classic lobule and based on zones of relative oxygenation of blood in sinusoids

Liver acinus

- hepatocytes closest to the portal triad structures are the best oxygenated and have the most products of digestion

- found in this zone

Zone 1

- zone closest to the terminal hepatic venule

- has the least oxygenation

Zone 3

- polygonal shape reflects position in sheets or plates with sinusoids on either side

- apical = facing canaliculus (where bile is secreted)

- basolateral = facing sinusoid (uptake of materials from blood)

- Rough ER present

- large volume of smooth ER

- Prominent Golgi

- Numerous mitochondria

- microvilli on basolateral side

Hepatocytes

- organelle in charge of bilirubin conjugation

- also does Phase I (cytochrome p450 system) and Phase II detox

Hepatocyte smooth ER

- normally small, inconspicuous and difficult to see with stain

- store fat, Vit A and function as (myo)fibroblasts when stimulated by cytokines (usually pathologic)

- found in perisinusoidal space

Hepatic stellate cells (Cells of Ito)

- members of monocyte/macrophage family

- help from sinusoidal lining

- filter blood and act as antigen-presenting cells

Kupffer cells

- hematopoiesis in embryo

- blood destruction (salvage iron)

- degrade/detox drug, toxins & waste

- excretion of wastes

- exocrine secretion (bile salts, etc)

- endocrine (modification of hormones)

- productions of blood proteins & lipoproteins

- manage glucose levels (gluconeogenesis)

- stores fat, carbs and other materials

Functions of liver