CHP18- digestion

What are the functions of the digestive system?

Ingestion (taking food in)

Motility (moving food)

Secretion (enzymes, acid, hormones)

Digestion (breaking food down)

Absorption (nutrients into blood)

Storage & elimination (waste removal)

Immune protection

Real-life: When you eat rice and egusi, your body breaks it down → absorbs nutrients → uses it for energy.

What is a polymer, monomer, and hydrolysis?

Polymer = large molecule (carbs, proteins, fats)

Monomer = small building blocks (glucose, amino acids, fatty acids)

Hydrolysis = breaking polymers into monomers using water

Example: Rice (starch polymer) → broken into glucose (monomer)

What are endocrine vs exocrine secretions in the GI system?

Exocrine (exits body)= released into GI tract (enzymes, HCl, mucus)

Endocrine = hormones into blood (gastrin, CCK, secretin)

Example: Stomach acid = exocrine Hormones controlling digestion = endocrine

What is peristalsis vs segmentation?

Peristalsis = wave-like movement pushing food forward

Segmentation = mixing/churning food Example: Peristalsis = food moving down esophagus & Segmentation = mixing food in intestines

What is part of digestive tract vs accessory organs?

Digestive tract: mouth → esophagus → stomach → intestines → anus

Accessory organs: liver, pancreas, gallbladder

Example: Liver helps digestion but food doesn’t pass through it

What are the phases of swallowing (deglutition)?

Oral (voluntary) – chewing + forming bolus

Pharyngeal /throat(involuntary) – airway closes

Esophageal (automatic) – peristalsis moves food

What is mastication?

Chewing food and mixing with saliva

what saliva?

contains mucus, an antimicrobial agent, and salivary amylase to start digestion of starch.

Lower esophageal sphincter (LES)

opens to allow food to pass into stomach. It stays closed to prevent regurgitation.

What is Barrett’s esophagus and why is it important?

Barrett’s esophagus is when the normal squamous cells in the esophagus are replaced by columnar cells due to damage from GERD. This change (metaplasia) increases the risk of esophageal cancer.

What is deglutition?

Swallowing food

What is the function of the uvula?

Closes off nasal cavity during swallowing Example: Prevents food from going into your nose

Function of parietal cells?

Secrete HCl (acid) → kills bacteria, activates enzymes

Secrete intrinsic factor → helps absorb vitamin B12

Function of chief cells?

Secrete pepsinogen (inactive enzyme)

Pepsinogen( chief cell) is converted to active pepsin (digests proteins).

What is the function of pepsin?

Breaks down proteins into smaller peptides

What is acute gastritis and what causes it?

Acute gastritis is inflammation of the stomach lining. It can be caused by excess acid, alcohol, or NSAIDs. These irritate or weaken the stomach’s protective lining, making inflammation worse.

What are peptic ulcers and how are they treated?

Peptic ulcers are erosions in the lining of the stomach or duodenum caused by acid damage, often linked to Helicobacter pylori infection which weakens the mucosal barrier. Treatment usually includes proton pump inhibitors (like Prilosec) to reduce acid and antibiotics to kill the bacteria.

What are gallstones and what problems can they cause?

Gallstones are hard clumps (mostly cholesterol) that form in the gallbladder when bile has too much cholesterol. They can block bile ducts and cause pain and nausea.

What do pancreatic acinar cells do?

Acinar cells make pancreatic juice, which is released into the duodenum through the pancreatic duct.

What is the function of amylase? (starts in mouth)

Breaks starch into sugars

Example: Starts in mouth when eating rice

Function of G cells?

Secrete gastrin → increases acid production

Function of intrinsic factor?

Helps absorb vitamin B12 in small intestine

What is chyme?

Semi-liquid mixture of food + gastric juices

What are the three parts of the small intestine?

the duodenum (first section)

the jejunum (middle)

ileum (last section).

Stomach

Stores food & begins protein digestion

Churns food to mix with gastric secretions

Kills bacteria in the food (acid)

Moves food into small intestine in the form of chyme liquid

Function of CCK and secretin?

CCK → released when fats/proteins present in chyme → stimulates bile & enzymes

Secretin → released when acidic chyme enters → stimulates bicarbonate (responds to drop in ph)

Example: Eating fatty food → CCK helps digest it

What forms protective barrier in stomach?

Mucus + bicarbonate layer Tight junctions Rapid cell replacement

secrete mucus to help protect stomach lining from acid(mucus neck cells)

What is absorption and where does it mostly occur?

Movement of nutrients into blood Mostly occurs in small intestine

How does the stomach protect itself from acid damage?

The stomach is protected by a mucus layer with bicarbonate that neutralizes acid, tight junctions between cells that prevent leakage, and fast cell replacement that renews the lining every few days.

What is GERD and what can it cause/treat?

GERD happens when stomach acid flows back into the esophagus, causing heartburn, cough, and sore throat. Over time it can lead to complications like strictures and Barrett’s esophagus. Risk factors include obesity, pregnancy, and hiatal hernia. It’s treated with H2 blockers or proton pump inhibitors (PPIs)

How is the small intestine adapted for absorption?

It has folds (plicae circulares), villi, and microvilli that greatly increase surface area, helping absorb more nutrients.

Function of plicae, villi, microvilli?

Increase surface area → maximize absorption

Example: Like folds in a towel → more area to soak water

Functions of large intestine?

Absorb water & electrolytes Produce vitamins (K, B) & Store feces

What is lactose intolerance?

Lactose intolerance is the inability to digest lactose due to low lactase enzyme. It causes bloating, gas, diarrhea, and nausea when dairy is consumed.

Valsalva's maneuver

It's when you hold your breath and strain, like when you're trying to poop. This makes the pressure in your chest go up.

Where is bile produced and stored?

Produced in liver Stored in gallbladder

What are large capillary spaces in liver?

Sinusoids → very permeable capillaries

What are phagocytic cells of liver?

Kupffer cells → destroy bacteria & debris

What is the hepatic portal system?

Blood from GI → liver → then circulation Example: Nutrients from food go to liver first before rest of body

Formation of bile – main components?

Bile salts (main functional part) Bilirubin Cholesterol Phospholipids

What is bilirubin?

Waste from breakdown of red blood cells

Gives feces brown color

Gives urine yellow color

Function of bile?

Emulsifies fats (breaks into small droplets) Example: Helps digest oily foods

Functions of liver?

Detoxifies blood

Stores glucose (glycogen)

Produces bile

Makes proteins (albumin, clotting factors)

Metabolizes fats & carbs

Function of gastrin?

Stimulates acid (HCl) secretion

Function of mouth?

Ingestion Chewing Starts carb digestion (amylase)

Function of microbiota in large intestine?

Produce vitamin K & B

Help digestion

Protect against harmful bacteria

Example: Antibiotics can kill good bacteria → diarrhea

One-way transport

allows for specialization of function along the tract

Reverse peristalsis

vomiting