What are the two categories of the organs in the digestive system. What is the funtion of each?
1. Digestive organs
-makes a continuous tube from where food enters the mouth until it leaves as waste through anus
2. Accessory 0rgans
-not part of the tract/tube but assists with digestion
How long is the distance from the mouth to anus? What are the organs digestion? And accessory?
1. gastrointestinal tract is 30ft long
2. Organs of digestion: mouth - pharynx - esophagus - stomach - small intestine - large intestine - anus
3. Acessory organs: teeth, tongue salivary glands, liver, gallbladder, pancreas
What is the function of mouth and pharynx and salivary glands? What are the exocrine secretions?
a. Mouth and pharynx: chewing begins and intitiation of swallowing
b. Salivary glands: moisten food, lubrication, polysacharide-digesting enzyme
-Salivary glands: salt water, mucus, amylase
What is the function and secretion of the esophagus?
1. Function: move food to stomach by peristatic waves, lubrication
2. Secretion: mucus
What are the functions and secretions of the stomach?
a. store, mix, dissolve and continue digestion of food
b. regulate emptying dissolved food into small intestine
c. solubilization of food particles
d. kill microbes and activate pepsinogen to pepsins
e. protein digesting enzymes
f. lubricate and protect epithelial surface
2. Secretion: HCI, pepsins, mucus
What is the function and secretion of the pancreas?
a. secretion of enzymes and bicarbonate
b. digest carbohydrates, fats, proteins, and nucleic acids
c. neutralize HCI entering small intestine from stomach
2. Secretion: enzymes and bicarbonate
What is the function and secretion of the liver?
a. secretion of bile
b. solubilize water-insoluble fats
c. neutralize HCI entering small intestine from stomach
elimination in feces
2. Secretion: bile salts, bicarbonate, organic waste products and trace metals
What is the function of the gallbladder?
Function: store and concentrate bile between meals
What are the functions and secretions of the small intestine?
a. digestion and reabsorption of most substances
b. mixing and propulsion of contents
c. food digestion
d. maintain fluidity of luminal contents
2. Secretion: Enzymes, salt and water, mucus
What is the function and secretion of the large intestine
a. storage and concentration of undigested matter
b. absorption of salt and water
c. mixing and propulsion of contents
2. Secretion: mucus
Where does digestion take place? And absorption? What about secretion and motility?
1. Digestion: takes place in the digestive tube which is outside of the body and open at both ends
2. Absorption: occurs along the tube
2. Secretion and motility: take place as food travels through tube
What are the 4 processes of the digestive system?
Food enters the lumen of the digestive tract
1. Digestion occurs in the lumen
2. Motility occurs and keeps food traveling through digestive tract
3. Absorption occurs which takes substances through lumen, pass the wall, and through interstitial fluid to the blood
3. Secretion occurs from the cell wall into the lumen of the tract, neighboring cells or the blood.
What happens to food during digestion? What are the two types of digestion? How are they different?
1. Food is broken down into simple organic molecules to make ATP, build tissues, and enzymes
-physically breaks down nutrients into smaller pieces
-chemical breakdown of nutrient polymers into smaller building blocsk using digestive enzymes
What happens to polymers during digestion?
Polymers are broken down into simple monomers through hydrolysis which are simple building blocks that can be absorbed by the blood stream
Memorize how these polymers are broken down!
What is Motility? What are the methods?
1. Movement through the GI tract as muscles push digesting material along
2. a. mastication
What is secreted via endocrine and exocrine? WHat do secretions regulate?
1. Exocrine digestive enzymes, acids, and mucus are secreted
2. Endocrine hormones to regulate digestion are secreted
3. Daily mass fluid balance is the digestive system is regulated
How are the input and output of fluid balanced?
-2.0L food and drink
-2.0L gastric secretions
-1.5L pancreatic secretions
-1.5L intestinal secretions
Total = 9.0L in lumen
-7.5L absorbed by small intestine
-1.4L absorbed by large intestine
-0.1L excreted in feces
Total = 9.0L removed from lumen
What occurs in the oral cavity? What are the functions in the oral cavity?
1. Ingestion of food occurs
a. Mastication breaks apart and mixes food with saliva
b. Saliva coats and lubricates food to aid swallowing
c. Salivary amylase begins digestion of carbohydrates
How long is the esophagus? How many muscles are needed for deglutition? What action forces the bolus to travel to the stomach?
1. *Hungs Voice* "Six inches.hehehehe.."
-10 inches long after the transiition from skeletal muscle at the top to the smooth muscle at the bottom
2. 25 muscles are needed to coordinate swallowing
3. Peristalsis moves a bolus down to the stomach
How long is food usually stored in the stomach? What happens in the stomach?
1. 2-4 hours
2. a. HCI acid and enzymes are secreted
b. protein digestion begins
What are the three cells of the stomach?
1. Chief cell: secretes and synthesizes protease, the precurser pepsinogen
2. Parietal cell: synthesizes and secretes HCI which makes pH acidic
3. Mucous cells: secretory cells which produce the acid containing protein mucin
What effect does acid have on protease?
Acid in the stomach converts protease precurser pepsinogen to pepsin
Why is the small intestine 20ft long? What is digested in the small intestine? What role do microvili have in the small intestine?
1. It consists of the duodenum, jejunum, and ileum
1. Digestion of carbohydrates, proteins, fats and nucleic acids occurs
3. Microvili absorb most nutrients and secreted fluids
What is the purpose of ducts in the duodenum?
Exocrine secretions from the liver and pancreas can enter from ducts into the duodenum
How are carbohydrates and sugars broken down?
How are proteins digested?
Proteins are broken down into peptides.
Peptides that are larger than di/tripeptides but not much larger are carried intact across the cell by transcytosis an into the liver
Di and tripeptides
How are lipids digested and absorbed? What are the stages and where does it take place?
1. In the lumen of the small intestinal tract
a.a fat droplet is broken down into small droplets of fat by bile salt phospholipids
-bile salts enhcance the digestive action of lipase
-when a large fat droplet is broken down its called emulsification
*The purpose of breaking down droplets into smaller ones is to create more surface area for lipase to work
b. pancreatic lipase breaks the droplet further into small groups called micelles
c. by breaking the bonds of the micelles, free fattty acids and monoglycerides can be absorbed
2. In the epithelial cell
a. Fatty acids and monoglycerides enter the cell through simple diffusion
b. Inside the smooth ER enzymes reasemble it into chylomicron
-chylomicron are transporters
3. In lacteals
c. chylomicron then absorbs into lacteals
-lacteals are lympthatic capillaries
How are nucleic acids digested and absorbed?
Nucleic acids are digested by nucleases into nitrogen bases and monosaccharides
How are vitamins and minerals digested and absorbed?
Fat soluble vitamins like A, D, E, K are absorbed with fats in the small intestin
Water soluble vitamins C and B's are transported into cells by membrane proteins
Minerals are moslty absorbed by active transport
How long is the large intestine? How long does it take to pass through the colon?
1. 5ft in length
What are the three functions of the large intestine?
- In the colon watery chyme is converted to semisolid feces
- Some absoroption of water, electrolytes and vitamins
-microbes help to synthesize vitmaines K and B's
Storage of feces until it exits the GI tract through anus
-microbes help to synthesize vitmaines K and B's
What are the two types of glands of the pancreas? What is each function?
1. Exocrine: pancreatic acini make up the exocrine glands.
a. Makes pancreatic juice digestive enzymes
b. also makes buffers which enters the duodenum
2. Endocrine: islets of langerhans produce hormones
a. glucagon and insulin
What are the five functions of the Liver?
1. Detoxification: removes toxins, drugs
2. Protein synthesis
3. Carbohydrate and lipid metabolism
4. Storage of excess nutrients
5. Synthesize bile: aids in lipid digestion
What is the purpose of the gallbladder?
Stores and concentrates bile from liver
What is the Motility, Secretion, digestion and absorption for the esophagus and oral cavity?
M: swallowing and chewing
S: saliva and lipase
D: carbohydrates and fats (minimal)
What is the M,S,D,A for the stomach?
M: peristaltic mixing and propulsion
S: HCI (from parietal cells)
pepsinogen and gastric lipase (from chief cells)
mucus and HCO3- (from mucous cell)
D: proetins and fats
A: Lipid soluble substances (alchohol and aspirin)
What is the M,S,D,A of the small intestine?
M: mixing and proplusion by segmentation
HCO3- and enzymes (from pancrease)
mucus (goblet cell)
A: peptides (active transport)
glucose and fructose (secondary transport)
fats (simple diffusion)
ions and minerals
vitamins (active transport)
M,S,D,A of large intestine?
M: segmental mixing
mass movement for propulsion
S: mucus (goblet cell)
D: none (except bacteria)
small organic molecules produced by bacteria
What happens during metabolism? What are the different types? WHat are the different states?
1. Extracts energy from nutrients
a. usess energy for work and synthesis
b. stores excess energy
2. anabolic versus catabolic
3. fed versus fasted state
What controls food intake? What are the two theories behind feeling full?
1. The brain has two centers in the hypothalamus
-feeding and satiety center
2. glucostatic and lipostatic theory
What are carbohydrates primarily absorbed as? What are the fates of carbohydrates?
2. a. used immediately for energy
b. used for lipoprotein synthesis in the liver
c.stored as glycogen in the liver and muscle
d. excess converted to fat and stored in adipose tissue
- glucose > pyruvate > acetyl CoA > fatty acids
What are proteins primarily absrobed as? What are its fates?
1. amino acids
2. a. most go to tissue for protein synthesis
b. convert in liver to substitute for aerobic metabolism if energy is needed
c. excess converted to fat and stored in adipose tissue
amino acids > acetyl CoA > fatty acids
What are fats absorbed as? What are there fates?
2. stored as fats in liver and adipose tissue
What is the push pull control of metabolism?
1. enzyme activity is regulated so that the pathway cycles back and forth
What hormone is the fed state influenced by? What is the net synthesis?
*insulin stiumulates glycogen synthesis*
2. net glycogen synthesis
What hormone is the fasted state influenced by? What is the net synthesis?
2. net glucose synthesis
What is the role of insulin? What does insulin raise? What effect deos it have on glucose levels?
1. Insulin promotes anabolism and increases glucose transport into insulin sensitive cells
-glusose oxidation and synthesis
*During fed state insulin dominates*
What does glucagon promote? Whats the effesct on glucose levels? What does glucagon raise?
1. Idk, check your notes and tell me
*In fasted state glucagon dominates*
What is the fasted state of adipose and skeltal muscle? What is the fed state of adipose and skeltal muscle?
1. Fasted: Insulin is absent. Because of this there are no GLUT4 transporters in the membrane so glucose cannot enter the cell
2. Fed: Insulin binds to receptors and signals GLUT4 transporters to take in glucose
What is the fasted and fed state for liver hypatocytes?
1. Fasted: hepatocytes make glucose (glycogen stores and gluconeogenesis) and transports it into the blood using GLUT2
-insulin is low
2. Fed: glucose concentration gradient is highest in the blood. GLUT2 now reverses and takes in glucose. Insulin signals glucose conversion
Why is is necessary to maintain fasted state metabolism? how does this happen?
*check chart to see better idea*
1. To maintain plasma glucose homestasis for the brain
2. a. Liver glycogen is converted to glucose
b. adipose lipids become free fatty acids and glycerol that enter blood
c. muscle glycogen can be used for energy.
-muscles also use fatty acids and break down their proteins to amino acids that enter the blood
d. brain can use only glucose and ketones for energy