DIgestive System

Honors Anatomy

Basic functions:

EADISM

• Elimination of wastes

• Absorption of nutrients

• Digestion (chemical/mechanical)

• Ingestion

• Secretion

• Mixing/propulsion

GI tract organs:

mouth → Pharynx → Esophagus → Stomach → Small intestine (duodenum, jejunum, ileum -DJI) → large intestine (Cecum, Colon, Rectum - CCR)

Accessory Organs:

“Little Parts Give Support”

Salivary glands, Pancreas, Liver, Gall bladder

2 forms of digestion:

1. Chemical - enzymes secreted in GI tract break chemical bonds to make smaller molecules that can be absorbed into the blood

2. Mechanical - grinding/mixing of food (ex: bile breaks large fat molecules into smaller ones)

Organ of GI tract:

what takes place. . .

1. chemical digestion

2. mechanical digestion

mouth:

1. chem: amylase breaks down carbs

2. mech: teeth grind food

Esophagus:

1. chem: none

2. mech: none

stomach:

1. chem: pepsin breaks down proteins, gastric lipase BEGINS breakdown of fats

2. mech: churning/mixing due to muscular contractions

small intestine:

1. chem: pancreatic juice (several enzymes) breaks down proteins, carbs, fats, + nucleic acids, intestinal juice (several enzymes) completes chem. digestion

2. mech: BILE aids in breakdown of fats (emulsification)

large intestine:

1. none

2. none

3 steps to digestion:

1. buccal (mouth)

2. gastric (stomach)

3. intestinal (duodenum)

proteins and carbs: (polymer → monomer)

polypeptides → oligopeptides → dipeptides → amino acid

polysaccharides → oligosaccharides → disaccharides → monosaccharides

lipids: (polymer → monomer)

lipids → fatty acids/Glycerol

nucleic acids: (polymer → monomer)

nucleic acids → nucleosides/nucleotides

membrane that lines cavities open to environment:

mucosal membrane

Mouth (oral cavity): (structure)

• hard palate - bones in roof of mouth

• soft palate - muscles in roof of mouth

• uvula - protects soft palate + prevents food from entering nasal cavity

• tongue

The 5 tastes:

1. Salty

2. Sweet

3. Sour

4. Bitter

5. Umami

what anchors the tongue to the roof of the mouth?

lingual frenulum (fold in mucosal membrane)

papilla:

“bumps” - projections of lamina propria found on surface of tongue; some contain chemoreceptors

chemoreceptors:

taste buds (gustatory sense receptors)

fungiform papillae: (location)

tip + lateral margins

foliate papillae: (location)

side of base of tongue

circumvallete papillae: (location)

largest (8-12 total)

filiform papillae: (location)

most numerous, no “taste”, used for grip

periodontal ligament:

connective tissue; anchors tooth to socket

cementum:

bone-like; attaches root to periodontal ligament

crown:

portion visible above gingivae

roots:

portion embedded w/in socket

dentin:

calcifies connective tissue, similar to bone; gives teeth shape/rigidity

pulp cavity:

space enclosed by dentin; contains nerves + blood vessels

enamel:

covers dentin of crown; extremely hard, resistant to wear + acidity

dentitions:

sets of teeth

• ppl have 2:

1. deciduous teeth (baby teeth)

2. permanent teeth (adult teeth)

incisors:

chisel/shaped; cut food

canines/cuspid:

pointed; tear + shred

deciduous molars:

crushing/grinding (BECOME the bicuspids)

premolars (bicuspids)

replace deciduous molars

permanent molars

do NOT replace any teeth

how many total teeth in adulthood:

32 total

Pharynx:

back of the oral cavity; divides into trachea + esophagus

epiglottis:

cartilage; covers opening to trachea

• three sections: NOL

  • Nasopharynx (superior)

  • Oropharynx

  • Laryngopharynx/Hypopharynx (inferior)

Esophageal hiatus:

opening in the diaphragm

peristalsis:

contractions/relaxations by smooth muscles lining walls

• mucus secreted by esophageal glands lubricates bolus/reduces friction

Lower Esophageal Sphincter:

separates stomach from esophagus

Stomach: (know circled/ numbered parts)

• serves as mixing vat + holding reservoir

• semi-solid bolus - to → soupy liquid chyme

mucus epithelial cells:

secrete mucus

parietal cells:

secrete hydrochloric acid

Chief cells:

secrete pepsinogen(inactive form)/pepsin(active form) + gastric lipase

pepsinogen/pepsin:

begins digestion of proteins in stomachand is activated by hydrochloric acid.

gastric lipase:

breaks down specific types of large fats

gastric juice:

combo of secretions from each of these cells

enteroendocrine cells:

produce + release hormones responsible for regulating digestion in stomach

Duodenum:

• 1st part of small intestine

• receives secretions from pancreas + gallbladder

• digestion completed here

Jejunum:

• middle part

• most absorption occurs here

Ileum:

• final portion

• regulates movement of chyme into colon

Intestinal glands:

(crypts of lieberkuhn)

• deep crevices w/in the mucosa line w/ glandular epithelium

• secrete intestinal juices (peptidase, nucleases, and nucleotidases)

paneth cells:

secrete bactericidal enzyme; helps regulate microbial pop. in gut

Brunner’s glands:

• secrete alkaline mucus

• helps neutralize gastric acid in chyme and provides an optimal pH for intestinal enzymes

Peyer’s Patches:

clusters of lymphatic nodules that provide a defensive barrier vs bacteria

enterocytes:

absorptive cells lining intestinal tract

final products of digestion:

• simple sugars

• amino acids

• fatty acids, glycerol

• nitrogenous bases

• vitamins + electrolytes

what structures increase absorption in the small intestine?

villi + microvilli

3 hormones that control digestive enzyme production/release:

1. gastrin

2. secretin

3. cholecystokinin

4 major regions of the large intestine:

CCRA

1. cecum - blind pouch found at junction of ileum + colon; appendix is attached to cecum

2. colon - ascending, transverse, descending and sigmoid portions

3. rectum - final portion of GI tract

4. anus - terminal end of rectum; contains sphincter

feces

waste material left over after water absorption

diarrhea

• movement of materials through GI tract TOO quickly

• not enough absorption = water inblalance/dehydration

constipation

• OPP of diarrhea

• caused by excessive water absorption

Pancreas connected to duodenum thru ____

pancreatic duct

pancreatic juice:

mix of water, salts, several enzymes and bicarbonate

pancreatic duct + common bile duct = ____

hepatopancreatic ampulla

acini

secrete pancreatic juice into pancreatic ducts

pancreatic amylase breaks down:

carbs

trypsin, chymotrypsin, carboxypeptidase, elastase break down:

proteins

pancreatic lipase breaks down:

triglycerides (lipids)

ribonuclease, deoxyribonuclease break down:

nucleic acids

cells w/in liver that produce bile:

hepatocytes

bile

digestive enzyme that emulsifies fats

common hepatic duct (liver) + cystic duct (gallbladder) = ___

common bile duct (empties into duodenum)

gallbladder:

• temporarily stores bile from liver

• stimulated by hormone cholecystokinin to release bile

saliva:

• mostly water + some solutes (mucus, amylase, salts)

  • mucus: lubricates food

  • amylase: starts digestion of carbs