Digestion Key Terms

PSIO 202

Absorption

Uptake of a substance

Desiccation

Removing water

Secretion

Release of a substance

Mechanical Digestion

Breakdown of food into smaller bits of the same food with no molecular alteration

Ingestion

Consumption via mouth

Mastication

Chewing

Deglutition

Swallowing

Propulsion

Pushing/moving forward

Peristalsis

Waves of SM contraction that cause propulsion

Defecation

Expelling feces (anything not absorbed/broken down) from the GI tract

Churning

Method of mechanical breakdown

Segmentation

Mechanical breakdown in intestines, breaking food into "segments and mixing (moving in both directions)

Bolus

rounded mushy lump of food (esophagus)

Chyme

Liquefied food (stomach/small intestines)

Feces

Found in colon

Layers of the Digestive Tract

Mucosa- Epithelium, lamina propria, muscularis mucosae

Submucosa

Muscularis Externa- Inner circular, Outer Longitudinal

Serosa

Enteric Nerves of the GI tract

Myenteric Plexus - controls peristalsis and other contractions of muscularis externa

Submucosal Plexus- controls muscularis mucosae and glandular excretions of the mucosa

Peritoneum Layers?

Visceral and Parietal

Retroperitoneal organs?

Duodenum, part of the pancreas, part of the large intestines

Mesentery

holds SI to posterior abdominal wall

Mesocolon

Holds LI to posterior abdominal wall

Falciform ligament

Holds liver to anterior abdominal wall

Greater Omentum

Fat layer over transverse colon and SI

Lesser Omenteum

Connects stomach (medial curve) to liver

Esophageal Sphincters? Function?

Upper Esophageal Sphincter- regulates swallowing and keeps excess air out of the esophagus

Lower Esophageal Sphincter- prevents reflux of stomach contents

Layers of the stomach- muscularis

Oblique (inner)

Circular muscle

Longitudinal muscle (outer)

Secretions of the Stomach? Functions? What is the rugae?

HCl (acid), enzymes, and mucous

Churns and liquifies foods

Rugae- layer of mucosa = wrinkly, most superficial (holds more food and + size)

Regions of the stomach?

Cardia, Fundus, Pyloric antrum, Pyloric canal, body, Pylorus, Pyloric Sphincter

Stomach Histology- Gastric Pits & Glands: Cell types?

Chief cells (pepsinogen/gastric lipase), mucous cells, parietal cells (HCl), regenerative SC, enteroendocrine cells (G cells, gastrin…)

Small Intestines functions? Regions? Sphincter?

Absorption, secretion, mixing, propulsion, segmentation, and chemical/mechanical digestion

Duodenum, Jejunum, and Ileum → Ileocecal Sphincter (small/large)

Small Intestines Circular Folds has…. and function?

Villi and microvilli to increase the SA for absorption.

Small Intestines histology anatomy? A Villus has…

Brush border of microvilli, Goblet cell, Lacteal, blood capillary, chylomicrons, & intestinal crypts

Chylomicrons is…

lymph containing triglycerides, coming from the lacteal. Travels to Thoracic duct (lymph flow) and the venous blood goes to the hepatic portal vein to be cleaned in sinusoids

Large Intestines: Functions, regions, and Sphincters?

Absorbs remaining water (desiccation) and segments bolus

R: Cecum, Vermiform appendix, ascending/transverse/descending colon/sigmoid colon, rectum, anal canal, and anus

Sphincters: Internal (SM) and External (Skel. M)

Large Intestines hisology?

Microvilli, absorptive cell (water), goblet cell (mucus secretion), intestinal gland, and openings

Mouth Anatomy:

Hard palate, soft palate, uvula, gingivae, superior labial frenulum, inferior labial frenulum, lingual frenulum, molar (grind), premolars (grind + crush), canines (tear), and incisors (Cut)

Tooth Anatomy

Enamel (protection), Dentin (calcified CT), Pulp cavity (BVs and nerves), Cementum (root to periodontal ligament), Periodontal ligament (anchor tooth to bone), Apical Foramen (opening for nerves, LVs, and BVs)

Crown, Neck, Root

Salivary Glands: Minor/Major

Intrinsic: scattered = saliva to moisten

Extrinsic: 3 pairs, outside of oral mucosa (Parotid, submandibular, and sublingual)

Salivary Glands Histology

Secretory cells: acini and mucous cells

Duct cells: form ducts → oral cavity

Liver Lobule Components:

Central vein, Hepatic triad (Branch of Hepatic vein/artery and bile ductule), Hepatocytes, Bile canaliculi, and hepatic sinusoid

Liver & Gallbladder Flow

Right/Left hepatic duct → Common Hepatic duct from the liver (Cystic Duct from Gallbladder) → Common Bile Duct (Pancreatic duct from pancreas) → Duodenum

Pancreas: Functions and anatomy

F: Secrete digestive enzymes & bicarbonate into the duodenum through the main pancreatic duct, hepatopancreatic ampulla, and Major Duodenal papilla w/ Hepatopancreatic Sphincter

Pancreas Histology:

Islets of Langerhans (endocrine- alpha = glucagon and beta- insulin) and acini (exocrine)

Negative Feedback: Blood sugar (practice

Insulin from beta cells decrease blood sugar by making glucose into glycogen. Glucagon from alpha cells bring blood sugar up by breaking glycogen into glucose.

Protein Digestion

Stomach: Chief cells release pepsin and HCl by parietal cells (Polypeptides → smaller)

SI: Pancreas- trypsin (smaller → dipeptides and aas), Brush Border: Aminopeptidase (smaller peptides → aas + smaller polypeptide) & Dipeptidase (dipeptides → aas)

Carb Digestion

Mouth:

polysaccharides → smaller by salivary amylase by salivary glands

SI:

smaller → disaccharides & monosaccharides, by pancreatic amylase by pancreas

By Brush Border:

alpha-dextrins → monosaccharides by alpha-dextrinase

Sucrose → glucose & fructose, by sucrase

Lactose → glucose & galactose, by lactase

Maltose → 2 glucose, by maltase

Lipid Digestion

Stomach:

lipids → glycerol & fatty acids, by lingual lipase by salivary glands

by gastric lipase by chief cells

SI:

Pancreatic lipase, by pancreas

Parietal cells: Secretions and Their Functions

HCl (kill bacteria, denature protein, activate pepsin) and Intrinsic factor (absorb vitamin B12)

Experiment 1: Enzymes and pH/temp- What was the point? What effect digestion more?

Decrease in pH seems to affect digestion more than decreases in temperature.

Experiment 2: Role of saliva in CARB digestion-

• The cracker softens → becomes sweet with time

• With time, complex carbs → smaller polysaccharides with salivary amylase

• Digestion of carbs begins in the mouth

Experiment 3: Saliva in gustation

• Takes longer to taste sweetness on a dry tongue

• Sugar from packets (sucrose) can easily dissolve → glucose and fructose ONLY in presence of saliva where receptors can detect it on the tongue

Experiment 4: Influence of Smell on Gustation

Olfactory neurons respond thousands of times more strongly to smell than gustatory receptors do to “taste”

Experiment 5: Role of Bile in Lipid Digestion

Bile emulsifies lipids- mechanically separating oil → smaller droplets

Lingual Papillae: Structures containing tastebuds- Name the 4 and their functions/where they’re found

• Vallate- LARGEST, = V shape on posterior surface of the tongue

• Fungiform- ALL OVER, mushroom shaped

• Foliate- SIDES of tongue,

• Filiform- MOST NUMEROUS, small/cone shaped. Sense texture BUT are the ONLY papillae that do not contain taste buds.

What is a taste bud? Anatomy?

Taste pore, gustatory microvilli, gustatory receptors (form taste bud…)

What are the 5 taste sensations?

Umami, sweet, savory, bitter, and sour (SSUSB)