Name the different organs of digestive system
Answers
Explanation:
stomach,small and large intestine
THE DIGESTIVE SYSTEM
Overview
Esophagus and Stomach
Small Intestine
Large Intestine
Liver, Gallbladder and Pancreas
Regulation of the Digestive System
Overview
The major parts of the digestive system:
Salivary glands
Pharynx
Esophagus
Stomach
Small Intestine
Large Intestine
Rectum
Accessory digestive organs: liver, gallbladder, pancreas
The major layers of the gastrointestinal tract:
Mucosa:
inner layer
lines the gastrointestinal tract
simple columnar epithelilium
Submucosa:
blood vessels
glands
nerve plexuses (Meissner’s plexus)
Muscularis:
peristalsis
nerve plexus (Myenteric plexus)
Serosa:
Outer layer of connective tissue
Functions of the GI system
Motility: movement through the GI tract
Digestion: breakdown of food or chyme
Secretion and absorption: across and epithelial layer either into the GI tract (secretion) or into blood (absorption)
Storage and elimination:
Esophagus and Stomach
Esophagus
From pharynx to stomach
Salivary glands release mucus for lubrication, antimicrobial agents, and amylase to digest starch.
epiglottis covers respiratory tract during swallowing
At end of esophagus is the lower esophageal sphincter (LES)
Propulsion of food occurs through peristalsis: contraction occurs behind the bolus of food and relaxation occurs ahead of the bolus of food.
Stomach
Functions:
store food
initiate digestion of proteins
kill bacteria with the strong acidity (low pH of the gastric juice)
make chyme
Parts of the stomach:
Fundus
body
pyloric region (pyloric sphincter)
material passed from the stomach to the small intestine is called the chyme.
The gastric glands of the stomach contain several types of cells:
Cell Type
Secretions
Parietal cells
HCl; intrinsic factor
Chief cells
pepsinogen
Goblet cells
mucus
Enterochromaffin-like (ECL) cells
histamine;serotonin
D cells
Somatostatin
G cells
Gastrin
pH of gastric juice is 2. The low pH of gastric juice:
denatures ingested proteins
optimum pH for pepsin activity is 2.0
at pH 2.0, weak pepsinogen enzymes digest each other to form pepsin
The stomach digests only proteins, but not fats and carbohydrates
There is basically no absoprtion in the stomach
Acid secretion by parietal cell:
H+ transport
H+ is converted to CO2 (blood)
CO2 diffused into parietal cell
CO2 is converted back to H+
H+ is transported into the GI lumen by a H+-K+-ATpase
Cl- transport
Cl- is transported into the parietal by a Cl-/HCO3- transporter
Cl- diffused into the GI lumen via a Cl- channel
Small Intestine
small intestine is from the pyloric sphincter to the ileocecal valve
12ft in length, small in diameter compared to large intestine
regions of the small intestine
duodenum: absoprtion of carbohydrates, lipids, amino acids, Ca2+, iron
jejuneum: absopriton of carbohydrates, lipids, amino acids, Ca2+, iron
ileum: absorption of bile salts, vitamin B12, water electrolytes.
Columnar epithelial cells
Villi/ microvilli: increases surface area for absorption
Core of villus
blood capillaries: absorption of monosaccharides, amino acids
lymphatic vessels (central lacteal): absorption of fats
Brush border enzymes: dissacharidase, peptidase, phosphatase.
Absorption in the Small Intestine
Caloric content of food is derived mainly from:
carbohydrates (50%)
proteins (11-14%)
lipids (36%-39%)