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Explain the difference between ingestion and absorbtion.
- Ingestion: The process of taking foods into the body.
- Absorbtion: The chemical breakdown of food molecules to be absorbed.
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List three ways food is mechanically broken down.
- Movements: Chewing
- Dissolution: Saliva, taste
- Emulsification: Breakdown of fats.
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List the 4 layers of the GI tract.
- Mucosa: Innermost, surrounds lumen. From esophagus to stomach is stratified squamous epi, from stomach to anus is simple columnar epi.
- Submucosa: Loose connective tissue
- Muscularis: 2 or 3 layers of smooth muscle
- Serosa or Adventitia: Serous membrane, surrounds outermost peritoneum.
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Explain the difference between exocrine and endocrine glands.
- Exocrine: Glands with ducts that secrete to a surface
- Endocrine: Secretes a hormone into the blood
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List examples of Exocrine glands.
- -Salivary glands
- -Pancreas
- -Liver
- -Gastric glands
- -Intestinal glands
- -Mucus glands
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List examples of Endocrine glands and the hormones each secretes
- Pancreas: Insulin
- Stomach: Gastrin
- Small Inestine: Secretin, Cholecystokinin (CCK), Gastric Inhibitory Peptide (GIP)
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Describe Visceral smooth muscle and why is it important in the GI tract.
- 1. Structure:
- a. Small cells
- b. Cell to cell spread of action potentials
- -Function of action potentials: Sheets of smooth muscle function as a unit and creates a wave of contraction.
- c. Slow contraction and relaxation
- 2. Location: Midesophagus to anus and made of muscularis
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Explain the difference between Peristalsis and Segmental Movements. What is the function of each.
- Perstalsis: Wave of relaxation followed by a wave of contraction
- Function: To move chyme forward
- Segmental: Alternating segments of mixing and breaking down food
- Function: Break chyme into smaller pieces
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Explain the differences in functions of each innevation of the GI tract
- Extrinsic: Autonomic Nervous System
- a. Parasympathetic: Rest/Repose and housekeeping
- 1. Nerves: Vagus and Sacral
- 2. Function: Stimulates secretions and movements
- Intrinsic: Enteric Plexus
- a. Myenteric plexus
- 1. Location: Between layers of muscularis
- 2. Function: Stimulates movement
- b. Submucosal plexus
- 1. Location: Submucosa
- 2. Function: Stimulate secretion from glands.
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List the components of Saliva. What is the function of each component.
- Water(99%)-Dissolution, taste
- Mucus-Lubrication
- Amylase-Begins starch digestion
- Lysozyme- Kills bacteria
- IgA antibodies- Immune defense
ie. enzyme
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List and describe the three phases of swallowing
- 1. Voluntary Stage: Oral, from mouth to oropharynx, being pushed by the tongue
- 2. Pharyngeal Stage: Pharynx
- a. Soft Palate: Lifts and closes off nasopharynx
- b. Epiglottis: Pushes down over larynx, closes off air tube
- c. Larynx: Sealed
- d. True Vocal Folds: Within the larynx, help seal
- e. Pharyngeal muscle: Costrict, pushing bolus of food toward the esophagus
- 3. Esophageal Stage: Involuntary, moves food from pharynx to stomach
- a. Peristaltic waves
- b. Relaxation of upper and lower esophageal sphincters
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List the secretions of the stomach. What is the function of each secretion?
- Hydrochloric Acid (HCl): Kills bacteria, activates Pepsin
- Intrinsic Factor: Binds with Vitamin B12 for later absorbtion in the ileum (for DNA synthesis)
- Pepsinogen: Activated by Pepsin, which begins protein digestion
- Mucus: Protects stomach wall from acid
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The stomach also produces a hormone. Name it and it's function.
- Gastrin:
- a. From endocrine cells found in gastric pits
- b. Secreted into blood
- c. Function: Stimulate secretion of Gastric acid (HCl), and stimulates stomach activity.
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Name the 3 phases controlling stomach secretions. Describe each.
- 1. Cephalic: Taste, smell, thought of food-->medulla oblongata-->Vagus nerves-->increases stomach secretion
- 2. Gastric: Distention, chemicals in stomach-->Vagal stimulation/Gastrin produced-->increases stomach secretion
- 3. Intestinal: Chyme in small intestine (esp. acid or fatty chyme), reflexly decrease stomach secretions and movements
- a. Small intestine hormones: CCK, Secretin, and GIP all decrease stomach secretions
- b. Local reflexes: Decrease stomach secretions
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Motor function of the stomach is primarily controlled by what type of "waves"?
Mixing waves: 80% of movement, gentle waves
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Stomach activity is controlled by both the nervous system and the endocrine system. What nerve and hormone is involved?
- Nerve: Vagus, which increases secretion, movements, and emptying.
- Hormone: Gastrin, increases lower esophageal sphincter tone, decreases pyloric sphincter tone, increases secretion, movements and emptying.
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List several stomach disorders and explain the cause of each.
- Peptic Ulcers: Damage to mucosa by bacteria.
- Hiatal Hernia: Widening of esophageal opening at diaphragm, may cause reflux.
- Pyloric Stenosis: Thickening of pyloric region interferes with stomach emptying.
- Belching: Gas pushed thru cardiac spincter.
- Hunger pangs: Contractions due to low blood glucose levels.
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List the functions of the small intestine.
- -Mixes and propels chyme
- -Chemical Digestion
- -Absorption- from intestine into the blood
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List structural features of the small intestine which help increase surface area. Why is it important that the small intestine has a large surface area?
- 1. Length and circular folds
- 2. Mucosa
- a. Villi
- b. Microvilli-Hairs
- c. Lacteals: Lymph capillaries which begin within villi; absorb fat.
- Promotes absorbtion by increasing surface area
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List the 3 exocrine glands in the small intestine
- 1. Mucous goblet cells
- 2. Duodenal glands- secrete alkaline mucous
- 3. Intestinal glands- secrete enzymes
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List the 3 endocrine secretions of the small intestine
- 1. Secretin
- 2. Cholecystokinin (CCK)
- 3. Gastric Inhibitory Peptide (GIP)
Stimulate small intestine, pancreas, and gall bladder.
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List the major enzymes found in intestinal juice and their functions
- 1. Maltase- Digests maltose--> 2 glucose
- 2. Sucrase-Digests sucrose--> 1 glucose + 1 fructose (table sugar)
- 3. Lactase-Digests lactose--> 1 glucose + 1 galactose (milk sugar)
- 4. Peptidases-Digests peptides--> amino acids
- 5. Enterokinase- Activates trypsinogen --> trypsin (trypsinogen= inactive, trypsin= active)
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List 2 hormones that stimulate intestinal juice.
CCK and secretin
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Explain the function of the ileocecal sphincter and how the opening and closing of the valve is controlled.
Function: To regulate how fast chyme moves into the Large intestine.
- Peristalsis of ileum decreases tone and increases emptying
- Distention of cecum increases tone and decreases emptying
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Why is the blood supply to the liver unusual?
Usual- Hepatic artery supplies liver with O2 and nutrients
Unusual- Hepatic portal vein transports nutrient laden blood from the digestive organs directly to the liver, where they are taken up and processed.
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List 6 functions of the liver cells; include both ordinary cells and phagocytic cells
- Hepatocytes (liver cells)
- 1. Produce bile which dilutes and neutralizes stomach acid, emulsifies fat
- 2. Short term storage of Vit. D, E, A, K, B12 minerals, copper, and iron
- 3. Interconvert nutrients by changing fructose & galactose to glucose, and ingested fats into phospholipids
- 4. Detoxify wastes and drugs (alcohol, ammonia) to urea.
- 5. Synthesize blood proteins- clotting proteins
- Phagocytic (Kupffer) cells-macrophages
- 6. These function for phagocytosis of blood cells and bacteria
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List the components of bile. What is the function of each component?
- Water- Dilute
- Bile salts- Emulsify fats
- Lecithin- Emulsify fats
- Cholesterol- For cell membrane fluidity
- Bilirubin- Excretory product of Heme
- Bicarbonate- Neutralizes acid chyme
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What is the function of bile?
To neutralize acid chyme and emulsify fats
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Rate of bile secretion is controlled by both hormonal and neural control. What nerve and hormone is involved?
- Nerve: Vagus
- Hormone: Secretin
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List the functions of the gall bladder
- 1. Bile storage
- 2. Concentration of bile
- 3. Ejection: Contraction of muscularis; relaxation of Hepatopancreatic sphincter
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List the nerve and hormone that controls the gall bladder secretions
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List the components of pancreatic juice. List the functions of each enzyme.
- Trypsin- Begins protein digestion
- Chymotrypsin- Begins protein digestion
- (pro) Carboxypeptidase- Completes protein digestion
- Amylase- Digests starch into glucose
- Lipase- Triglyceride lipids that turn into 3 fatty acids + glycerol
- Nucleases- Digest DNA and RNA
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List the nerve and hormones that controls the exocrine secretions of the pancreas.
- Nerve: Vagus
- Hormone: Secretin and CCK
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What is the endocrine secretion of the pancreas?
Insulin
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List the 3 major classes of carbohydrates and how each is absorbed by the small intestine.
- 1. Glucose: Active transport into the blood (REQUIRES CARRIER)
- 2. Galactose: Active transport into the blood
- 3. Fructose: Facilitated diffusion into the blood (Helped diffusion)
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List the 2 major classes of proteins and how each is absorbed by the small intestine.
- 1.Amino Acids: Active transport into blood.
- 2. Dipeptides, Tripeptides may also be absorbed: Active transport into blood
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What transport method is used by the small intestine to absorb ions?
Active Transport
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What ion requires vitamin D for proper absorption?
Ca++, requires D for transport into blood
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Describe Lipid absorption within the villus.
- A. Micelle
- B. Lipids metabolites(Fatty acids+glycerol-->Triglycerides)-->(Simply diffused) being coated with protein inside of epithelial cell
- C. Cholymicrons use exocytosis to move into lacteal
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List the fat soluble vitamins and describe how they are absorbed.
D, E, A, K- Absorbed from Micelles into the lacteal.
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Vitamins B and C are absorbed into the small intestine by what process?
By Diffusion into the blood.
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How is the mucosa of the large intestine different from the small intestine?
It is smooth, No Villi
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List the secretions of the large intestine. Functions?
- 1. Mucus: To lubricate colon wall; helps fecal matter stick together
- 2. Bicarbonate ions: Neutralize acid made by intestinal bacteria.
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Why are bacteria important in the large intestine?
- Produces vitamin K then synthesizes it.
- Produces B vitamins that are anti yeast and fight bad bacteria
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What is the major function of the large intestine?
Storage
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List the components of feces.
- 70%-Water
- 30%- Bacteria
- Fiber
- Mucus
- other molecules
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Where are the feces typically stored along the GI tract?
Transverse colon to rectum
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What stimulates mass movements?
Movement from stomach to duodenum, duodenum distention=Local reflexes stimulated=mass movements
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How does the defecation reflex differ between an infant and an adult?
- Infant-->rectal distention-->sacral sensory neurons-->spinal cord-->sacral parasympathetic neurons-->smooth muscle contraction of sigmoid and rectum-->relax of internal anal sphincter-->Defecation
- Adult-->rectal distention-->sacral sensory neurons-->spinal cord-->brain-->voluntary components-->straining-->relaxation of external anal sphincter-->Defecationn
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