Final: Nutrition, Digestion, and Absorption Slides Flashcards
Functions of digestive system (2)
-Chemically breaks down food we eat
-Absorbs the food to transfer it to cells
(making nutrients in food accessible to cells)
Processes of digestive system (4)
Motility, secretion, digestion, absorption (in that order)
What happens during motility?
Food moves through organs at appropriate speed (propulsive), and food is mixed
Purpose of mixing food during motility
Promotes digestion and mixing with enzymes, and facilitates absorption
What are proteins, carbohydrates, and lipids broken down into?
Proteins: amino acids
Carbs: glucose, fructose, galactose (monomers)
Lipids: fatty acids
What happens during secretion in the digestive system?
Digestive organs release many substances (enzymes, lubricants, etc.)
What happens during process of digestion?
Food broken down into smaller pieces so it can be absorbed
What are the main organs of the digestive system? (7)
Mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus
What are the accessory organs of the digestive system? (4)
Salivary glands (3), liver, gall bladder, pancreas
Difference between main and accessory organs of the digestive system
Food only physically passes through the main organs, while accessory organs release substances into the main organs
Types of salivary glands and location (3)
- Sublingual (under tongue)
- Submandibular (under jaw)
- Parotid (by ears)
What enzymes does saliva contain? What are their functions?
Salivary amylase: starts digestion of carbs
Lingual lipase: starts lipid breakdown (mostly insignificant effect)
Functions of saliva in the mouth (5)
- Facilitates swallowing by lubricating food particles
- Provides antibacterial action by releasing lysozymes (break down bacteria)
- Saliva dissolves food particles to stimulate taste buds
- Aids in speech
- Neutralizes ingested acid (saliva usually basic)
Function of esophagus (and how it moves food)
Muscular tube (smooth muscle) that connects pharynx and stomach; peristaltic waves push food down (no actual digestion occurs)
Structure of esophagus
- Upper esophageal sphincter is located proximally (beginning)
- Lower esophageal sphincter is located distally (end)
Functions of stomach (3)
- Starts digestion of proteins
- Gastric mixing and gastric emptying
- Temporary hold for food that is consumed
Structure of stomach
- Gastroesophageal sphincter: opening from esophagus
- Pyloric sphincter: gateway to small intestine
- Rugae: folds that increase surface area
What happens during gastric emptying?
Pyloric sphincter open: peristaltic contractions move food into duodenum
What happens during gastric mixing?
Pyloric sphincter closed: food mixed inside stomach, cannot enter duodenum
What does the rugae of the stomach contain?
Gastric mucosa (has gastric pits, comprised of many different cell types)
What types of cells comprise the gastric mucosa? (3)
Mucosa cells, chief cells, pareital cells
Function of mucosa cells
Release mucous for lubrication
Function of chief cells
Release pepsinogen (inactive enzyme)
Function of parietal cells
Release HCl and intrinsic factor (helps absorption of Vitamin B12, needed for red blood cell synthesis)
How is pepsinogen activated and what is its function? What is the active form called?
Activated by HCl; active form is pepsin
-Function of pepsin is to break down dietary proteins we consume into smaller peptide fragments
What happens in the duodenum?
Food broken down into final digestible form (amino acids, fatty acids, etc.)
From where does the duodenum receive input?
Pancreas, liver and gall bladder, stomach
Structure of pancreas
- Dual organ that contains endocrine (release hormones) and exocrine (release enzymes) tissue
- Exocrine tissue contains acinar cells and duct cells
Function of acinar cells of pancreas
Release pancreatic juice (mix of pancreatic enzymes)
What classes of enzymes do acinar cells release into the duodenal lumen?
- Proteolytic enzymes: trypsinogen, chymotrypsinogen, procarboxypeptidase
- Pancreatic amylase
- Pancreatic lipase
Function of proteolytic enzymes released by pancreas
Break down proteins
Function of pancreatic amylase and pancreatic lipase
- Pancreatic amylase digests polysaccharides into disaccharides
- Pancreatic lipase digests triglycerides into glycerol and fatty acids (requires bile from liver to do this)
Function of pancreatic duct cells
Release bicarbonate (HCO3-), which neutralizes acidic food mixture coming from stomach
What triggers the pancreas to release its contents?
Small intestine (duodenum) releases two hormones: secretin acts on duct cells, and cholecystokinin (CCK) acts on acinar cells
Function of liver
Hepatocytes release bile salts that function in fat emulsification
Function of gall bladder
Storage of bile salts
Function of bile
Emulsification: break down large fat globules into smaller fat droplets (increased solubility)
Pathway of food through digestive system main organs
Mouth - esophagus - stomach - small intestine - large intestine - anus
Parts of small intestine (3)
Duodenum, jejunum, ileum
How does the small intestine increase its surface area?
Has circular folds that contain villi (fingerlike projections), and each villus has many epithelial cells that have their own folds (microvilli, or brush border)
What are the brush border enzymes?
Additional enzymes in the small intestine: enterokinase (activate trypsinogen), disaccharidases (break down disaccharides), and aminopeptidases (hydrolyze peptide fragments to amino acids)
Overview of carbohydrate digestion
Dietary carbohydrates - SALIVARY AMYLASE - smaller polysaccharides - (no digestion in stomach) - PANCREATIC AMYLASE - disaccharides - DISACCHARIDASES - monosaccharides
How are monosaccharides and amino acids absorbed into the blood?
Enter duodenal lining through secondary active transport and leave through facilitated diffusion
Overview of protein digestion
Dietary proteins - PEPSIN (in stomach) - small polypeptides - PANCREATIC TRYPSINOGEN AND CHYMOTRYPSINOGEN - very small peptides and amino acids - AMINOPEPTIDASES - amino acids
Overview of lipid digestion
Dietary lipids - LINGUAL LIPASE - fat globules - BILE SALTS - fat droplets - PANCREATIC LIPASE - glycerol, fatty acids, monoglycerides
How are lipids absorbed into the blood?
Glycerol and fatty acids contained in micelles (vesicles) enter epithelial cell lining through diffusion, are resynthesized into triglycerides, packaged, and exocytose in chylomicrons (vesicles) to enter lymphatic vessels
Parts of large intestine
Cecum, colon (ascending, transverse, descending, sigmoid), rectum
What goes to the large intestine? (3)
- Stuff that’s indigestible; these waste products are excreted from the body as feces
- Houses helpful bacteria in colon (intestinal flora)
- Some absorption of water and electrolytes
Function of intestinal flora
Symbiotic relationship: they help us produce Vitamin K, we give them an unlimited food source (but they must stay contained in the large intestine)
