A&P 2 Lec 17: GI Secretions

Gallbladder

- Gall bladder will release bile into the duodenum - has similar layers to the GI tract - Neurons and hormones will stimulate the muscularis layer to contract and release bile into the duodenum

Pancreas

Acinar cells vs. Islets of Langerhans cells •Located by duodenum •Shares a common duct (entry point into duodenum) with the gallbladder •99% of the cells of the pancreas secrete digestive juices (acinar cells) •1% of the cells are responsible for secreting insulin/glucagon (cells of Islets of Langerhans) Exocrine vs. Endocrine Composition and Functions of Pancreatic Juices •Release of juices is stimulated by parasympathetic system and CCK and secretin •Contains a mixture of components -Water -Sodium bicarbonate à neutralize stomach acid -Enzymes à help with digestion - •Digestive enzymes -Pancreatic amylase à digest starch -Pancreatic lipase à digest fat -Proteases à digest proteins -Nuclease à to digest nucleic acids

Small Intestine

chyme enters small intestine in a slow, controlled manner - regulated by hormone and nervous system Duodenum vs. ileum vs. jejunum duodenum - 1st, functions in digestions, pancreatic juices/bile enter here ileum & jejunum - has high surface area for absorption of nutrients Circular folds, villi and microvilli - help improve the surface area for absorption of nutrients Intestinal crypts - contain absorptive cells, mucous producing cells, intestinal enteroendocrine cells All secretions and cells they come from* Intestinal enteroendocrine cells that secrete: - Gastric inhibiting peptide (GIP) - inhibit stomach function and promote insulin release - Secretin - stimulate pancreas and liver, inhibit parietal cells - Cholecystokinin (CCK) - stimulate pancreas, liver, gallbladder, inhibits stomach function Accessory Organs pancreas - pancreas, liver, gallbladder

Esophagus

deglutition - swallowing (requires epiglottis) peristalsis - muscle contractions

Describe the action of each hormone: gastrin, cholecystokinin, secretin, histamine, gastrin inhibiting peptide

gastrin - gastric secretion - EE cells - stimulates parietal and chief cell secretion cholecystokinin - intestinal secretion - stimulate pancreas, liver, and gallbladder, inhibits stomach secretin - intestinal secretion - stimulate pancreas and liver, inhibit parietal cells, inhibit stomach histamine - gastric secretion - EE cells - stimulates parietal cell secretion gastrin inhibiting peptide - intestinal secretion - inhibit stomach secretions and contractions - inhibit stomach function, promote insulin release

Pharynx

oro-, naso- and laryngopharynx) Deglutition - swallowing (requires epiglottis) Peristalsis - muscle contractions

Identify the regions of the small intestines, the function of each area, and structures that increase surface area.

regions: duodenum (first) - pancreatic juices/biles nerter here ileum & jejunum (second) - has high surface area for absorption of nutrients increased surface area: - villi and microvilli

Identify the regions of the large intestines, special features that are found along with their function.

regions: look in last ppt

Analyze how the muscularis layer of the GI tract changes through the GI tract (From STOMACH to ANUS) (GI Organizational Chart last three columns)

stomach - extra/third muscularis layer: oblique layer in addition to circular and longitudinal layers (aid mechanical digestion) small intestine - inner circular layer and outer longitudinal layer of smooth muscle colon - regular circular layer and specialized longitudinal layer: teniae coli rectum/anus - skeletal muscle

Analyze how the mucosa layer (mucous membrane) of the GI tract changes through the GI tract (From STOMACH to ANUS) (GI Organizational Chart last three columns)

stomach - simple columnar small intestine - simple columnar colon - simple columnar rectum/anus - stratified squamous

Mouth (oral cavity)

Hard vs. soft palate Hard palate -Palatine bone and maxilla bone Soft palate -Muscles covered in mucous membrane -Stratified epithelial tissue Salivary glands Saliva (salivary amylase) - Salivary glands produce saliva that help with several processes related to digetion - Chemical digestion = Salivary amylase starts carbohydrate digestion Papillae vs. Taste buds vs. taste cells

Stomach

Food storage -Can hold up to 4 liters of ingested material (extreme!) Mechanical digestion -Grinding and pulverizing action Initial chemical digestion -Primarily proteins Sphincters control movement of food into and out of the stomach Sphincters (lower esophageal and pyloric Rugae - muscosa form rugae - function to allow the stomach to expand Oblique layer of muscle Gastric pits, gastric glands •Mucosa layer is covered in small depressions called gastric pits •The base of a pit splits into two or three gastric glands All secretions and cells they come from* •Mucous neck cells secrete mucus •Chief cells secrete pepsinogen -Converted to pepsin by HCL -Functions in protein digestion •Parietal cells secrete hydrochloric acid (HCl) -Help denature (unfold) proteins -Activates pepsinogen -Kills pathogens Chyme - Gastric secretions mix with food and saliva to make chyme

Pancreas: identify major cell types and their secretions

•99% of the cells of the pancreas secrete digestive juices (acinar cells) •1% of the cells are responsible for secreting insulin/glucagon (cells of Islets of Langerhans)

Liver

•Largest gland in the body •Functions -Metabolism of digested nutrients -Detoxifies alcohol/drugs -Produces bile •Bile is secreted by liver cells, transported and stored in the gall bladder Bile •Gall bladder is stimulated by parasympathetic system and CCK and secretin to release bile •Components -Bile salts - DIGESTION •Helps with fat emulsification -Cholesterol - WASTE •Produced in and removed by liver as waste -Bile pigments (bilirubin) from hemoglobin - WASTE •globin = a reuseable protein •heme = broken down into iron and bilirubin •Bilirubin is toxic and must be removed