Anatomy

• Ingestion: The process of taking foods into the body.
• Absorbtion: The chemical breakdown of food molecules to be absorbed.

• Movements: Chewing
• Dissolution: Saliva, taste
• Emulsification: Breakdown of fats.

• 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.

• Exocrine: Glands with ducts that secrete to a surface
• Endocrine: Secretes a hormone into the blood

• -Salivary glands
• -Pancreas
• -Liver
• -Gastric glands
• -Intestinal glands
• -Mucus glands

• Pancreas: Insulin
• Stomach: Gastrin
• Small Inestine: Secretin, Cholecystokinin (CCK), Gastric Inhibitory Peptide (GIP)

• 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

• 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

• 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.

• Water(99%)-Dissolution, taste
• Mucus-Lubrication
• Amylase-Begins starch digestion
• Lysozyme- Kills bacteria
• IgA antibodies- Immune defense

ie. enzyme

• 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

• 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

• 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.

• 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

Mixing waves: 80% of movement, gentle waves

• Nerve: Vagus, which increases secretion, movements, and emptying.
• Hormone: Gastrin, increases lower esophageal sphincter tone, decreases pyloric sphincter tone, increases secretion, movements and emptying.

• 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.

• -Mixes and propels chyme
• -Chemical Digestion
• -Absorption- from intestine into the blood

• 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

• 1. Mucous goblet cells
• 2. Duodenal glands- secrete alkaline mucous
• 3. Intestinal glands- secrete enzymes

• 1. Secretin
• 2. Cholecystokinin (CCK)
• 3. Gastric Inhibitory Peptide (GIP)

Stimulate small intestine, pancreas, and gall bladder.

• 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)

CCK and secretin

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

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.

• 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

• Water- Dilute
• Bile salts- Emulsify fats
• Lecithin- Emulsify fats
• Cholesterol- For cell membrane fluidity
• Bilirubin- Excretory product of Heme
• Bicarbonate- Neutralizes acid chyme

To neutralize acid chyme and emulsify fats

• Nerve: Vagus
• Hormone: Secretin

• 1. Bile storage
• 2. Concentration of bile
• 3. Ejection: Contraction of muscularis; relaxation of Hepatopancreatic sphincter

• Nerve: Vagus
• Hormone: CCK

• 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

• Nerve: Vagus
• Hormone: Secretin and CCK

Insulin

• 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)

• 1.Amino Acids: Active transport into blood.
• 2. Dipeptides, Tripeptides may also be absorbed: Active transport into blood

Active Transport

Ca++, requires D for transport into blood

• 
• 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

D, E, A, K- Absorbed from Micelles into the lacteal.

By Diffusion into the blood.

It is smooth, No Villi

• 1. Mucus: To lubricate colon wall; helps fecal matter stick together
• 2. Bicarbonate ions: Neutralize acid made by intestinal bacteria.

• Produces vitamin K then synthesizes it.
• Produces B vitamins that are anti yeast and fight bad bacteria

Storage

• 70%-Water
• 30%- Bacteria
• Fiber
• Mucus
• other molecules

Transverse colon to rectum

Movement from stomach to duodenum, duodenum distention=Local reflexes stimulated=mass movements

• 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