Gastrointestinal system 2 Flashcards
Describe the stomach
J-shaped organ at the base of the esophagus
What are the parts of the stomach (top to bottom)
Cardia
Fundus
Body
Pylorus
What connects the stomach to other organs
Lesser omentum - connects to liver
Greater omentum - connects to transverse colon
What are the three modified layers of the muscularis
Oblique
Circular
Longitudinal
Describe the internal surface of the stomach
Rugae - temporary folds allow for expansion (1.5L) - storage
Describe rugae
Folded core of submucosa with overlying mucosa
Describe the mucosa in the stomach
Simple columnar epithelium
In folding to increase surface area for secretion (3L) - permanent glands.
What is needed in the stomach
Acid and enzymes (digestion)
Mucous (protection)
Hormones (regulation)
What cells make up a gastric gland
Parietal cells
G cells
Chief cells
(mucous cells - surface)
What do parietal cells secrete
Acid and intrinsic factor (Vit B12 absorption)
What do G cells secrete
Hormones - gastrin (regulate secretion and motility)
What do chief cells secrete
Enzymes - Pepsinogen - inactive precursor of pepsin (digests proteins)
Describe the structure of chief cells
Abundant RER
Apical zymogen granules - containing enzymes
Basal nucleus (due to granules)
Describe the structure of parietal cells
Central nucleus
Folded structure to increase surface area for ion pumps (H+)
Abundant mitochondria to pump H+ against conc. gradient
Describe the endocrine control in the stomach
Endocrine cells in mucosa
Gastrin and Ghrelin secreted into bloodstream
Describe neural control in the stomach
Enteric nervous system (ENS) - local reflexes
CNS modulates ENS function - long neural reflexes
What is chyme
Partially digested food material - acidic
What is the function of the pyloric sphincter (PS)
To control the release of chyme into the small intestine
What needs to be done to chyme when entering the small intestine
Further digestion (enzynmes produced by pancreas) Protection from acidity - Mucous - neutralize acid (bicarbonate)
Describe the pancreas
Head in C -shaped duodenum Tail to spleen Posterior to stomach Duct in duodenal lumen Retroperitoneal (doesn't move)
How does the pancreas secrete things
Bile duct meets pancreatic duct at entrance to hepatopancreatic ampulla
Duodenal papilla projects into duodenal lumin
Release controlled by hepatopanreatic sphincter
What are the endocrine functions of the pancreas
Pancreatic islet alpha cells - glucose
Pancreatic islet beta cells - insulin
What are the exocrine functions of the pancreas
Acinar cells - digestive enzymes
Duct cells - bicarbonate
Describe acinar cells
Secrete enzymes Apical zymogen granules Basal nucleus Abundant RER (like chief cells in stomach)
