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.
List three ways food is mechanically broken down.
- Movements: Chewing
- Dissolution: Saliva, taste
- Emulsification: Breakdown of fats.
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.
Explain the difference between exocrine and endocrine glands.
- Exocrine: Glands with ducts that secrete to a surface
- Endocrine: Secretes a hormone into the blood
List examples of Exocrine glands.
- -Salivary glands
- -Gastric glands
- -Intestinal glands
- -Mucus glands
List examples of Endocrine glands and the hormones each secretes
- Pancreas: Insulin
- Stomach: Gastrin
- Small Inestine: Secretin, Cholecystokinin (CCK), Gastric Inhibitory Peptide (GIP)
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
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
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.
List the components of Saliva. What is the function of each component.
- Water(99%)-Dissolution, taste
- Amylase-Begins starch digestion
- Lysozyme- Kills bacteria
- IgA antibodies- Immune defense
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
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
The stomach also produces a hormone. Name it and it's function.
- a. From endocrine cells found in gastric pits
- b. Secreted into blood
- c. Function: Stimulate secretion of Gastric acid (HCl), and stimulates stomach activity.
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
Motor function of the stomach is primarily controlled by what type of "waves"?
Mixing waves: 80% of movement, gentle waves
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.
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.
List the functions of the small intestine.
- -Mixes and propels chyme
- -Chemical Digestion
- -Absorption- from intestine into the blood
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
List the 3 exocrine glands in the small intestine
- 1. Mucous goblet cells
- 2. Duodenal glands- secrete alkaline mucous
- 3. Intestinal glands- secrete enzymes
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.
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)
List 2 hormones that stimulate intestinal juice.
CCK and secretin
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
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.
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
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
What is the function of bile?
To neutralize acid chyme and emulsify fats
Rate of bile secretion is controlled by both hormonal and neural control. What nerve and hormone is involved?
- Nerve: Vagus
- Hormone: Secretin
List the functions of the gall bladder
- 1. Bile storage
- 2. Concentration of bile
- 3. Ejection: Contraction of muscularis; relaxation of Hepatopancreatic sphincter
List the nerve and hormone that controls the gall bladder secretions
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
List the nerve and hormones that controls the exocrine secretions of the pancreas.
- Nerve: Vagus
- Hormone: Secretin and CCK
What is the endocrine secretion of the pancreas?
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)
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
What transport method is used by the small intestine to absorb ions?
What ion requires vitamin D for proper absorption?
Ca++, requires D for transport into blood
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
List the fat soluble vitamins and describe how they are absorbed.
D, E, A, K- Absorbed from Micelles into the lacteal.
Vitamins B and C are absorbed into the small intestine by what process?
By Diffusion into the blood.
How is the mucosa of the large intestine different from the small intestine?
It is smooth, No Villi
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.
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
What is the major function of the large intestine?
List the components of feces.
- 30%- Bacteria
- other molecules
Where are the feces typically stored along the GI tract?
Transverse colon to rectum
What stimulates mass movements?
Movement from stomach to duodenum, duodenum distention=Local reflexes stimulated=mass movements
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