Digestive System 2 - Accessory Organs Flashcards
Where is the Salivary Glands situated?
Submucosa of Oral Cavity + tongue
What are the Salivary Glands grouped as?
Lingual Labial Buccal Molar Polatine
What are the 3 Large Salivary glands?
Sublingual - beneath tongue
Submandibular - floor of mouth, inner surface of mandible, ducts behind teeth
Parotid - largest empties into mouth
What type of Glands/Cells are the Large salivary glands?
Tubulo-acinar glands
What do the Large Salivary glands close to oral cavity secrete?
Mucus
What do the Large Glands distal to the Oral Cavity secrete?
Serous
Sublingual - mucus acini
Submandibular - serous and mucus acini
Parotid - serous acini
Describe the Liver?
- Largest gland of body ,
- highly vascularised -
- surrounded by connective tissue
- 4 lobes - 2 major L&R, 2 minor caudate + quarate
What does the Liver function as?
Exocrine gland (onto epithelium via duct), Gallbladder (bile storage)
Describe the Vasculature of the Liver?
Recieves blood from 2 vessels
- Hepatic artery (oxygenated, 25%)
- Hepatic portal vein (digestive system, 75%)
Where is the Blood discharged into from the Liver?
Small vascular channels called Sinusoids (capillaries)
What Cells are located in the Liver?
Kupffer cells - sinusoidal macrophages
What does Sinusoidal Macrophages do?
Destroy Bacteria and Degrade worn-out blood cells
Describe the Blood flow of the Liver?
Sinusoids -> central vein -> Hepatic vein -> Inferior Vena Cava
What are the Hepatic Sinusoids lined by?
Discontinuous Sinusoidal Epithelium
Describe the Liver Lobule?
Basic functional unit, composed of -
Terminal Hepatic Venule
Interconnecting Plates of hepatocytes
Peripherally arranged Portal triads
What are the Specialised epithelial cells in the Liver?
Hepatocytes
What is the Liver Lobule delimited by?
Connective tissue called Interlobular Septum
What are the Hepatocytes Zones in the Liver Lobule?
Periportal
Mid-zone
Centriobular
Describe the Periportal Hepatocyte zone of the Liver?
Most oxygenated, highest nutrient + highest toxin conc
Describe the Mid-zone Hepatocyte zone of the Liver?
No sharp Boundaries
Describe the Centriobular Hepatocyte zone of the Liver?
Lowest nutrient component, larger glycogen/fat deposits
Least oxygenated
Describe the Bile Production in the Liver Lobule?
Bile composition is organic (bilirubin) and inorganic (bile salts)
What is the Bile Produced by?
Hepatocytes - passes into bile caniculi (carry bile to bile duct)
What is the Bile duct lined by?
Cholangiocytes
What are the features of Cholangiocytes?
Short microvilli, one Cilium per cell (senses change in flow)
Describe Bile secretion?
Contains; Terminal bile ducts Intrahepatic bile ducts Cystic duct Common bile duct
What is the Terminal Bile duct lined by?
Cuboidal Epithelium
Describe the Intrahepatic bile ducts?
coalesce into L + R hepatic ducts, which then unite to form common hepatic duct
What is the Hepatic Duct lined by?
Columnar Epithelium
Where does the Cystic duct secrete Bile from?
To/From Gallbladder
Where does the Common Bile duct secrete bile to?
Duodenum
Describe Gallbladder?
Ovoid sac with muscular wall - can distend
Concentrates and Stores biles
Describe the how the Gallbladder Concentrates and Stores bile?
H2O+ ions absorbed by mucosa, receives watery bile from hepatic duct and empties thick concentrated bile into common bile duct
Describe the Mucosa of the Gallbladder?
Columnar epithelium with Microvilli, no goblet cells or muscalaris or submucosa, Arranged in Plicae, concentrated bile expelled by contraction of S.Muscle
What hormone is released in the Gallbladder?
Cholecystokinin (CCK) is a peptide hormone, released from inclusion cells in duodenem
What is the Purpose of the CCK hormone in the Gallbladder?
Reduces digestive motility and gastric emptying
Where is the Pancrease?
Behind the Stomach, Retroperitoneal covered by a thin layer of connective tissue
Describe the Function of the Pancrease?
Endocrine and Exocrine functions
What are the Exocrine functions of the Pancreas?
Composed of tubulo-acinar glands which secrete pancreatic juice (alkaline fluid of enzyme precursors)
What forms the Secretory Acini?
Single layer of Epithelial cells
What are the Endocrine functions of the Pancreas?
Contains of Islets of Langerhans (scattered around) that secrete products into Pancreatic ducts which contain variety of neuroendocrine cells
What Cells are contained within the Islets of Langerhans?
Beta Cells Alpha Cells Delta Cells PP Cells e- Cells EC cells D1 Cells
Describe the function of Beta cells of the Islets in the Pancreas?
Secrete insulin + amylin, 60% of cells, stimulates glycogen and protein/fatty acid synthesis
Describe the function of Alpha cells of the Islets in the Pancreas?
Secrete glucagon, 15% of cells, opposite actions of insulin
Describe the function of Delta cells of the Islets in the Pancreas?
Secrete Somatostatin, 5% of cells, locally acting hormone inhibits other endocrine cells
Describe the function of Pancreatic Polypeptide (PP) cells of the Islets in the Pancreas?
Stimulates gastric chief cells and Inhibits bile secretion
Describe the function of Epsilon (e) cells of the Islets in the Pancreas?
Secrete Ghrelin and stimulates Appetite
Describe the function of Enterochromaffin (EC) cells of the Islets in the Pancreas?
Secretes;
secretin : control secretion of hormone
motilin : stimulates gastric activity
substance -p: wide range of functions
Describe the function of D1 cells of the Islets in the Pancreas?
Secrete VIP (vasoactive intestinal peptide) relaxes stomach and gallbladder and reduces arterial blood pressure