Digestive System 2 Flashcards
Where is the stomach located and shape?
J-shaped left superior side of abdomen, hollow and elastic
What does the elasticity of stomach allow?
Increase in diameter and volume of stomach
What are the functions of the stomach?
Store food, continue digesting carbs, initiate fats, and proteins digestion
Where does the majority of chemical and mechanical digestion occur?
Stomach
What happens during stomach peristalsis?
The chyme is pushed towards the pyloric sphincter in waves which then are retropulsed towards the stomach, breaking down the food into tiny particles suitable for the small intestine
How does food enter stomach?
Cardiac/lower esophageal sphincter
What is the pyloric sphincter?
valve which leads chyme into small intestine
What are the 4 regions of the stomach?
Cardia, fundus - storage, body and pylorus which regulates the emptying of chyme into small intestine
What is the mucosa layer of the stomach?
Simple cuboidal layer surface mucous cell layer to protect the lining of the stomach, which is filled with acidic and gastric juices, lamina propria (areolar connective tissue) and muscularis mucosae (smooth muscle)
What 4 cell types do gastric glands contain?
Mucous neck, parietal, chief & G cells
What are gastric glands?
epithelium columns of mucus cells that extend into the lamina propria and at bottom are gastric pits
What do parietal cells secrete?
Intrinsic factor & HCL
What do chief cell secrete?
Digestive enzymes (lipase, pepsin)
What do G cells secrete?
Hormones such as gastrin
What is special of the gastric muscularis membrane?
Muscularis is made of three layers; oblique (diagonal), circular, and longitudinal (bottom) which help with stomach contractions.
What are the 7 gastric secretions?
HCL, pepsinogen, renin, lipase, intrinsic factor, hormones & mucus
What are the functions of HCL?
Kill bacteria & parasites, activate pepsin & lingual lipase secretion, digest plant products & cell walls, break protein bonds, change bolus into chyme, convert ferrous ions into ferric ions
What are the functions of pepsinogen?
Is the inactive form of pepsin, activated by HCL which breaks it into polypeptides and peptides and removes peptides to form pepsin which digests proteins
What are the functions of lipase?
Digestive enzyme that breaks fats into glycerol and fatty acids
What are the functions of renin?
Only found in the gastric glands of babies and curdle milk, and slow digestion of proteins to maximize nutrition
What are the function of Intrinsic Factor?
Needed for the absorption of B12 in small intestine
What is the function of mucus in stomach?
Protect gastric lining from acids, abrasions and enzymes
What are the hormones & their functions?
Gastrin & histamine regulate HCL, serotonin & somatostatin regulate stomach motility
What are the 3 regions of the small intestine?
Duodenum, jejunum & ileum from shortest to longest
What is the main function of small intestine?
Absorb 90% of nurtrients
What is the function of the duodenum?
Receives bile & pancreatic juices
What is the structure of the jejunum?
Encased by serosa and suspended by mesentry
What is the structure of the ileum?
Same as jejunum and connect with large intestine at ileocecal valve
What occurs during segmentation?
Alternating ring-like localized contractions occur in regions of the small intestine filled with chyme by the circular muscle fibers, and inner middle muscle fibers forming small segments which mix around the chyme with gastric juices, bile and secretion and exposure to the mucosa for nutrient absorption
What occurs during peristalsis?
During Peristalsis or migrating motility complex, food from the lower end of the stomach is slowly propelled into the ileum between 90 – 120 minutes.
Where is peristalsis the strongest & weakest?
Strongest in esophagus & stomach, weakest in small intestine
What is small intestine glandular epithelium lined with?
Lined with intestinal glands or Crypts of Lieberkühn which secrete intestinal juice
What 4 types of cells does Crypts of Lieberkühn contain?
Absorptive - contain microvilli, goblet - mucus, Paneth - lysozyme enteroendocrine - secretes hormones
What else do the SI lamina propria contain (tonsils)?
MALT & Peyers Patches
What 3 special structures do SI contain for absorption?
Circular folds, Micro villi and villi
What is the role of circular folds?
force chyme to slowly spiral through the lumen, allowing more time for nutrient absorption
What is the role of Villi?
Finger-like projections from the mucosa increase surface area for digestion and absorption and embedded into its core are a network of blood capillaries and lymphatic capillaries called lacteal which absorb nutrients.
What is the role of Microvilli?
Small projections from absorptive cells towards the lumen and form a fuzzy brush border enzymes that complete carbs and protein digestion
What are the 4 functions of the SI?
Segementation, peristalsis, Fully digest carbs & fats, and initiate & complete proteins & absorb 90% nutrients
What is the function of liver?
Produces bile which emulsifies and breaks up fat molecules
Function of Gall bladder?
Store & concentrate bile
Functions of pancreas?
Produce digestive enzymes and bicarbonate to neutralize stomach
Where is the liver located?
Upper right quadrant of abdominal cavity
What is the structure of the liver?
Made of 4 lobes, divided into thousands of lobules
What components are made of the liver?
Hepatocytes, bile canaliculi, hepatic sinusoids
What are Hepatocytes?
Liver cells that make up 80% of liver, arranged in three dimensional arrangements called hepatic laminae which line along hepatic sinusoids.
What are bile canaliculi?
Tubes that collect secreted bile from hepatocytes
How does bile pass?
Bile canaliculi + bile ducts + common hepatic duct + common bile duct into duodenum
How does bile exist lobules?
Bile duct
How does bile exit liver?
Hepatic ducts
How does bile enter duodenum?
Common bile duct
What are Hepatic sinusoids?
Permeable vascular capillaries located between columns of hepatocytes that inputs oxygenated blood from hepatic arteries, and nutritious de oxygenated blood from hepatic portal veins
What are the liver’s two blood supply?
Hepatic artery & hepatic portal vein
Function of hepatic artery?
Provides the liver with oxygenated blood
Function of hepatic portal vein?
Provides the liver with deoxygenated nutrient-dense, and possibly toxic blood containing bacteria and microbes from the GI
Function of hepatic vein?
Returns blood from the liver to heart
Functions of liver?
Secrete bile, carb, protein & fat metabolism, excretion of bilirubin, store glycogen and Vitamins
What are bile salts?
Bilic acids containing sodium and potassium and emulsification agents to digest & absorb fats in SI
Pathway of bile salts?
95% recycled, 5% new, 95% reabsorbed in duodenum by through hepatic portal vein (enterohepatic circulation), 5% excreted
What does bile contain?
Bile salts, cholesterol, bile pigments, phospholipids and electrolytes.
How is bilirubin produced?
From the destruction of RBCS, and decomposition of hemoglobin
List steps of Bilirubin formation?
Haem & globin separated, Haem converted into bilirubin enters bloodstream and collected and excreted by liver into duodenum converted into urobilinogen by bacteria, some urobilinogen sent to kidney as urobilin, rest converted into stercobilin and give feces brown
