Digestive System

Structures

Structures

oral cavity, teeth, tongue

Pharynx

Esophagus

small/large intestine

Accessory Organs

salivary glands, liver, gall bladder, pancreas

Functions

ingestion, mechanical processing, digestion, secretion, absorption, compaction

Major Layers

Mucosa, Submucosa, Musclaris externa, Serosa

Mucosa

inner lining- villi

stratified squamous in mouth, esophagus, pharynx

stratified columnar in stomach and intestines

Muscularis mucosae- within villi that change shape of lumen

Secretory glands

Submucosa

dense irregular connective tissue

Muscularis Externa

2 layers of smooth muscles that move food through system (circular/longitudinal)

Serosa

visceral peritoneum

NOT found in oral cavity, pharynx, esophagus, rectum

Peristalsis

move bolus forward

Segmentation

churn contents (more mechanical)

Oral cavity, teeth, tongue

mechanical breakdown

Pharynx

muscular propulsion to esophagus

Esophagus

transport to stomach

Stomach

chemical breakdown by acid/enzymes(protein absorption); mechanical processing

Small Intestine

enzymatic digestion and absorption

Large Intestine

dehydration and compaction of indigestable material to prepare for elimination

Oral Cavity

tongue, salivary glands, teeth

Superior Boundary of Oral Cavity

hard palate, soft palate

Posterior Boundary of Oral Cavity

uvula, palatine tonsil, root of tongue, lingual tonsil

Amylase

break down of carbs

Lipase

break down of lipids

Teeth

crown, neck, root, dentin, enamel, cementum, periodontal ligament, root canal

Dentin

within tooth, similar to bone

Cementum

enamel for beneath gumline/root not as hard as enamel

Enamel

hardest substance in body, covers crown

Periodontal Ligament

attaches tooth to socket

Incisors

blade shaped

Cuspids

canine teeth, tearing, slashing

Bicuspids

flattened crown, crush, grind

Molars

very large flattened crown

Deciduous Teeth

baby (2-20 teeth)

come in at 6-24 months

Secondary Dentition

permanent

lower central incisors= 6-7 years

3rd molar (wisdom teeth)= 17-21 years

Pharynx

Nasopharynx (back of nasal cavity)

oropharynx

Laryngopharynx

• common passageway

Esophagus

hollow muscular tube, no serosa layer

lumen closed except when swallowing

Deglutition

swallowing 3 phases

Buccal phase

voluntary- bolus compressed against hard palate

Pharyngeal Phase

ivoluntary- tactile receptors on pharyngeal arches and uvula are stimulated (stimulates contraction)

Esophageal Phase

involuntary- contraction of phayngeal muscles force bolus through entrance of esophagus (peristalsis)- stimulates contraction

Stomach Parts

Fundus- upper rounded portion

Cardia- espohagus attaches to stomach

Body

Pylorus- exit into small intestine

Lesser Curvature- smaller superior curve

Great Curvature

Stomach Wall Layers

• Mucosa

• Submucosa

• Muscularis externa (3 layers)

• Serosa

Muscularis Externa of Stomach

• longitudinal muscle layer

• Circular muscle layer

• Oblique muclse layer (angled)

Rugae- prominent but temporary folds that allow gastric lumen to expand

Gastric Glands

secrete gastric juice

• Parietal, Enteroendocrine, Cheif cells

Parietal Cells

secrete intrinsic factor and HCI

Enteroendocrine Cells

produce hormones

Chief Cells

secrete pepsinogen (break down proteins) - gastric glands

Lacteal

lymphatic vessel in small intestine

allows things to get processed a second time (lipids)

Structure of Small Intestine

Duodenum- upper region, neutralization, finish digestive process

Jejunum- absorption

ileum- absorption

Structure of Large Intestine

Ileum empties into—> cecum(pouch), colon, rectum

4 segments of colon

ascending, transverse, descending, sigmoid

Taniae Coli

longitudinal layer of muscularis externa, works as drawstring to compress in colon

Haustra

pouches in colon

Gastrin

increases stomach motility and stimulates production of gastric acid and enzymes

Secretin

released when chyme enters duodenum, increases secretion of bile and buffers

Gastric Inhibitory Peptide (GIP)

secreted when fats and carbohydrates – especially glucose- enter small intestine, stimulation of insulin release

Cholecytokinin (CCK)

secreted when chyme containing lipids and proteins enters duodenum; accelerates

Vasoactive Intestinal Peptide (VIP)

dilates regional capillaries and inhibits acid production in the stomach

Salivary Glands

Sublingual Glands- mucus

Submandibular Glands- amylase

Parotid Glands- large amounts of salivary amylase

4 Lobes of Liver

Right, left, cuadate, quadrate

Round Ligament

divdies right and left lobes in liver

Common Bile Duct

carries bile from liver and gall bladder to duodenum

formed by merger of cystic duct (from gall bladder) and common hepatic duct (from liver)

Functions of Liver

storage of fat soluble vitamins (A, D, E, K)

synthezise/secrete bile

inactivate toxins/ lipid-soluble drugs

store iron

Gall Bladder

stores and concentrates bile

located in posterior surface of right lobe of liver

Pancreas

posterior to stomach

Pancreatic lobules, Pancreatic Enzymes

Pancreatic Duct

delivers exocrine secretions to duodenum

Pancreatic Juice

exocrine secretion and water and ions

Proteolytic Enzymes

break apart proteins