ch. 14 | the digestive system, nutrition, & metabolism

functions:

• ingestion: taking food into the mouth
• secretion: releasing water/acid/buffers/enzymes into lumen of GI tract
• mixing & propulsion: churning & pushing food through GI tract
• digestion: physically & chemically breaking down food
• absorption: passing digested products from GI tract into blood & lymph
• defecation: eliminating feces from GI tract

• the digestive system has all the organs while the digestive tract is from the mouth to the anus

layers of the GI tract:

mouth:

we have 32 teeth

3 major salivary glands:

salivary amylase: enzyme that begins digestion of starch
mucus: lubricates food
lysozyme: enzyme that kills bacteria

• deglutition: swallowing
• peristalsis: successive muscular contractions along the wall of a hollow muscular structure 

stomach:

• sphincters:

1. (gastro)esophageal- controls the movement of material from esophagus to stomach
2. pyloric- controls movement of material from stomach to duodenum
3. ileocecal- separates the large & small intestines 

• the fundus is on the left side of the body

small intestines:

• ileum transports material into the cecum of the large intestine 
• liver cells (hepatocytes) make bile
• the liver fills most of the right hypochondriac & epigastric regions
• gallbladder stores bile

digestion: mouth--> pharynx--> esophagus--> gastroesophageal sphincter--> stomach--> pyloric sphincter--> small intestine: duodenum-->jejunum-->ileum--> large intestine: cecum--> ileocecal valve--> colon: ascending--> transverse --> descending--> sigmoid--> rectum--> anal canal--> internal anal sphincter--> external anal sphincter

the large intestine: absorbs water & eliminates waste

• right lumbar region- ascending colon; left lumbar region- descending colon
• the small intestines is located almost entirely in the umbilical & hypogastric regions
• the rectum is in the hypogastric region 

• enzymes secreted by the pancreas:

-pancreatic amylase: breaks down starches
-trypsin, chymotrypsin, carboxypeptidase: break proteins into amino acids

-pancreatic lipase: breaks trigylcerides into fatty acids

-ribonuclease, deoxyribonuclease: breaks down nucleic acids 

-pancreatic juice flows into the duodenum through the pancreatic duct

• diarrhea: frequent defecation of liquid feces, caused by increased motility of the intestines or absence of enzymes to process the food nutrients
• constipation: infrequent or difficult defecation caused by decreased motility of the intestines 

• metabolism: all the chemical reactions in the body
• anabolic reactions (synthesis reactions): molecules combine 
• catabolic reactions (decomposition reactions): molecules are broken down 

• glycolysis: anaerobic process (requires no oxygen)
• aerobic respiration: uses oxygen

• type 1 diabetes: involves lack of insulin bc immune sys. has destroyed pancreatic B cells
• type 2 diabetes: involves decreased sensitivity of target cells to insulin

• obesity: an imbalance btwn energy intake & energy expenditure

• carbs break down into sugars
• proteins break down into amino acids
• lipids break down into fatty acids
• nucleic acids break down into nucleotides