Digestive System III Flashcards
What is the function of the stomach?
Holding reservoir and mixing chamber
Major secretions: mucus, Gastrin, intrinsic factor, acid, pepsinogen, gastric lipase
What are the 4 main parts of the stomach?
- Cardia
- Fundus
- Body
- Pyloric
Histology has the added layers:
Muscularis mucosae: 2 layers
Muscularis externa: 3 layers
What are the histological layers of the stomach?
- Mucosa:
- simple columnar epithelium
- lamina propria
- muscularis mucosa
- Submucosa
- no glands
3. Muscularis
3 Layers:
-inner oblique
-middle circular
- outer longitudinal
- Serosa
What is what are the gastric pits and gastric glands made up of?
The simple columnar epithelium with mucous cells invaginates into the lamina propria to for, gastric pits and gastric glands
What are the specialized cells of the epithelium of the stomach?
- mucous cells
- parietal cells
- chief cells
- enteroendocrine cells
- regenerative cells
Give a general overview of the small intestines
- Approximately 3m in length
- Divided into 3 parts
- Both retro- and intraperitoneal parts
- major functions - digestion and absorption, secretion
- adaptations- microvilli, villi & plicae circularis (circular folds)
- Lacteals (lymphatic vessels ) are present in the core of the villus- transport of absorbed nutrients
Describe the mucosa of the small intestine
Epithelium- simple columnar with goblet cells
Intestinal glands (crypts of Lieberkuhn)- enterocytes, goblet cells, Paneth cells, enteroendocrine cells and M cells
Lamina propria- loose connective tissue and abundant mucosa-ass9ciated lymphoid tissue
Muscularis mucosa- smooth muscle
Describe the submucosa of the small intestine
- dense connective tissue
- the lymphatic tissue of the lamina propria may extend into the submucosa
Describe the muscularis externa
2 layers of smooth muscles:
Outer—> longitudinal muscle
Inner—> circular
Describe the serosa of the small intestine
The small intestine is covered in serosa except for 2nd, 3rd, 4th part of the duodenum
What are the adaptations of the small intest8bes?
- Circular folds (plicae circulae)-folds of mucosa and submucosa
- Villi-finger like projections of the mucosa—> epithelium with a core of lamina propria
- Microvilli-x> brush border projection of the apical membrane of the absorptive cells
Describe the general characteristics of the duodenum
C shaped tube
-25 cm long
Distinguishing characteristics:
- Appearence of circular folds
- Opening of hepatopancreatic duct
- Brunners glands in submucosa—> alkaline secretion
What are the 4 basic layers of duodenum?
- Mucosa
- Submucosa
- Muscular externa
- Serosa
What makes up the mucosa of the duodenum?
Epithelium- simple columnar
Enterocytes Goblet cells Paneth cells Stem cells Enteroendocrine cells
Describe the submucosa of the duodenum
Brunners glands
How many layers does the muscularis externa of the duodenum have?
2 layers
Describe the serosa of the duodenum
1st part intraperitoneal rest is retroperitoneal
What are the distinguishing characteristics of the jejunum?
Long, branched circular fold
What are the diseases of the jejunum?
Celiac disease
What are the diseasees of the stomach?
Peptic ulcer
What are the distinguishing characteristics of the ileum?
- Blunted circular folds
- Submucosa: Aggregated lymphoid tissue-Peyer’s patches
What valve opens the small intestine into large intestine?
Ileocecal valve open the small intestine into the large intestine
What are the functions of the large intestine?
- completion of digestion
- absorption of water, ions, vitamins
- production of vitamins B & K
- formation and expulsion of waste
Consists of 4 parts
Summarize the characteristics of the ileum
Pale pink color
- 2-3 cm caliber
- thin and light wall
- less vascular it’s than jejunum
- short vasa rectus
- arcades has many short loops
- more fat in mesentery than jejunum
- low and sparse circular folds(plicae circulae); absent in distal parts
- many lymphoid tissue (peyers patches)
Summarize the characteristics of the jejunum
Deep red color
Caliber: 2-4 cm
Thick and heavy wall
Greater vascularity than the ileum
Long vasa recta
Arcades have a few large loops
Less fat in mesentery than the ileum
Large, tall, and closely packed circular folds(plicae circulae)
Few lymphoid tissues(peyers 0atches)
What are the distinguishing characteristics of the large intestines?
Haustra
- tenia coli
- epicolic appendages
- abundance of goblet cells, no villi
Appendix- wormlike structure attached to the cecum, containing large amounts of lymphoid tissue
What are the diseases of the large intestine?
Appendicitis
Diverticula disease
What are the layers of the large int3stine?
Mucosa
Submucosa
Muscularis
Serosa
Describe the mucosa of the large intestine
Epithelium- simple columnar with goblet cells
Intestinal glands/crypts of lieberkuhn
Lymphatic nodules
Describe the submucosa of the large intestine
Dense connective tissue.
Describe the muscularis of the large intestine
Tenia coli, haustra
Describe the serosa of the large intestine
Epiploic appendages
Describe the rectum
Taenia coli at rectosigmoid junction become one continuous layer of muscle instead of three discrete bands.
Rectum is between rectosigmoidd junction (rectum joins large intestine) and pectinate(dentate) line - dentate line is where endoderm meets ectoderm)
What are the features of the rectum/anal canal?
Rectum- transverse rectal folds
Anal canal- anal columns
Epithelium- simple columnar to stratified squamous
Highly vascularized
Internal anal sphincter- smooth muscle
External anal sphincter - skeletal muscle
What are the diseases of the rectum/anal canal?
Colorectal cancer
Hemorrhoids
Describe the liver
Location-right upper quadrant
Second largest organ
-intraperitoneal organ
4 lobes
What are the functions of the liver?
Endocrine/exocrine organ, detoxification, storage, lypolysis
Describe the architecture of the liver
Lobule- the functional unit of the liver
Hepatocytes are arranged in stacked rows
Sinusoids- large endothelium lined spaces containing blood
Portal triad- hepatic artery, bile duct, portal vein
What diseases aff3ct the liver?
Hepatitis
Describe the histology of the liver
Hepatocytes-cuboidal with central nuclei
Mono-or binucldated
Glycogen stores-pale staining
Spaces between cells
Describe the biliary tree
The biliary tree is the pathway for the flow of bile after its secretion from the hepatocytes
Heoatocytes—>. Bile canaculi—>bile ductules—> bile duct—>right and left hepatic ducts—> cystic ducts—> common bile duct—> hepatopancreatic ampulla
What disease affects the biliary tree?
Jaundice
Describe the gall bladder
Pear shaped organ, volume of 30-50 mls
Simple columnar epithelium
Stores and concentrate bile
Smooth muscle contracts under the influence of CCK
Can gall stones be asymptomatic?
Can be asymptomatic (common in fat, fertile, female of forty); or it may produce colic or acute cholecystitis
What causes biliary colic?
Usually caused by spasm of the smooth muscle of the gall bladder in an attempt to expel the gall stones
What is Acute cholecystitis?
Pain in the right upper quadrant—> may cause subdiaphragmatic parietal peritoneum irritation, which is supplied by the phrenic nerves (refferred pain -x> right shoulder)
What can cause of obstruction biliary tree?
Obstruction of biliary tree by gall stone or compression by pancreatic growth —> obstructive jaundice. Impaction of stone in the ampulla can cause passage of infected bile into the pancreatic duct leading to pancreatitis
What are the sources of blood for the liver?
- Hepatic artery-oxygenated
- Hepatic portal veins- dexugenated, nutrient rich
The portal veins collects venous blood with products of digestion from the abdominal parts of the GIT, gallbladder, spleen & pancreas
What is the portal system?
Capillary bed drains into another capillary bed through veins
What disease affects the portal system?
Alcoholic liver disease
Describe the pancreas
- retroperitoneal gland
- division: head, body, tail, uncinate process
- Endocrine/exocrine gland
- secretes - pancreatic digestive juices, glycogen, insulin, etc
- pancreatic duct joins with CBD—> hepatopancreatic ampulla(HPA) , aka Ampulla of vaster of duodenum
Give the functions of pancreas as an exocrine gland
Pancreatic digestive juices cells in clusters called acini
Pancreatic amylase, trypsin, elastase
Give the functions of pancreas as an endocrine gland
Endocrine pancreas secretes: insulin, glucogan, somatostatin, pancreatic polypeptide
Islets of langerhans
