Liver Functions

Liver Functions

• Detoxification: The liver filters and removes toxins, chemicals, and waste products from the blood, including alcohol, drugs, and harmful byproducts.
• Detoxification importance: It keeps the body clean and healthy by removing harmful substances.
• Bile Production: The liver produces bile, which aids in the digestion of fats in food.
• Bile Production importance: Without bile, the body would have difficulty digesting and absorbing fats and fat-soluble vitamins (A, D, E, K).
• Storing Energy (as Glycogen): The liver stores glucose from food as glycogen.
• Storing Energy Importance: When blood sugar is low, the liver converts glycogen back into glucose to provide energy.
• Regulating Blood Sugar: The liver helps maintain stable blood sugar levels by storing and releasing glucose.
• Regulating Blood Sugar importance: Balanced blood sugar levels are key for energy and overall health.
• Protein Production: The liver produces important proteins such as albumin, which helps maintain fluid balance in blood vessels, and proteins for blood clotting.
• Protein Production importance: These proteins help blood clot when injured and maintain fluid balance.
• Cholesterol Regulation: The liver manages cholesterol levels by making and breaking down cholesterol.
• Cholesterol Regulation importance: Proper cholesterol levels protect the heart and blood vessels.
• Nutrient Processing: After food is digested, the liver processes nutrients like proteins, fats, and vitamins for the body's use.
• Nutrient Processing importance: This ensures the body gets the nutrients needed for energy and growth.
• Liver as cleaner, energy manager, and nutrient processor.

GI Tract Layers

• Mucosa: The innermost layer protects, secretes, and absorbs.
• Submucosa: It lies beneath the mucosa and provides support with blood vessels, lymphatic vessels, and nerves that support the mucosa, and transports nutrients. It also helps with expansion during digestion.
• Muscularis: It lies beneath the submucosa and is responsible for moving and churning food through muscle contractions (peristalsis), mixing food with digestive enzymes and acids (like in the stomach).
• Serosa: The outermost layer, protects and reduces friction through lubrication.
• The layers work together aiding in the digestion and absorption of food, while ensuring an efficient food movement.

Pancreas Functions

• Pancreas location: The pancreas is located behind the stomach.
• Pancreas functions: Exocrine and Endocrine.

Exocrine Function (related to digestion)

• The pancreas produces digestive enzymes and bicarbonate to help break down food in the small intestine.
• Digestive enzymes like amylase, lipase, and proteases are released into the duodenum through a duct. These help digest carbohydrates, fats, and proteins.
• Bicarbonate is secreted to neutralize stomach acid, creating an optimal environment for enzyme action.

Endocrine Function (related to blood sugar regulation)

• The pancreas has hormone-producing cells called islets of Langerhans.
  • Key hormones:
    • Insulin: lowers blood sugar levels by helping cells absorb glucose for energy, thus lowering blood sugar levels.
    • Glucagon: raises blood sugar levels by signaling the liver to release stored glucose into the bloodstream, thus raising blood sugar levels.
• The pancreas aids in digestion and blood sugar regulation

Summary of Pancreas Functions:

• Exocrine
  • Produces digestive enzymes (amylase, lipase, proteases) to break down food.
  • Produces bicarbonate to neutralize stomach acid.
• Endocrine
  • Produces insulin to lower blood sugar.
  • Produces glucagon to raise blood sugar.

Small Intestine Parts

• Duodenum: the first part of the small intestine, right after the stomach
  • Digestion occurs here. Digestive enzymes and bile from the pancreas break down food.
  • Neutralizes stomach acid using bicarbonate.
  • Chemical digestion - enzymes break down fats, proteins, and carbs into smaller molecules for absorption
• Jejunum: middle part of the small intestine - located between the duodenum and ileum. It is the main site of nutrient absorption (proteins, carbs, fats).
  • Nutrients from food (proteins, carbs, fats, vitamins, minerals) are absorbed into the bloodstream through the walls of the jejunum.
  • Tiny villi and microvilli increase surface area for absorption.
• Ileum: last part of the small intestine.
  • Absorbs remaining nutrients (vitamins, B12, bile salts).
• The small intestine as a whole is where most of the digestion and absorption of food takes place.

Summary of Mesenteries:

• Mesenteries functions: support and hold organs, supply blood and nerves, and aid in immune functions.
  • Types:
    • Mesentery Proper: Supports the small intestines.
    • Mesocolon: Supports the large intestine.
    • Lesser Omentum: Connects stomach and liver.
    • Greater Omentum: Provides protection and padding to intestines.
• Mesenteries are essential for keeping your organs in place, supplying nutrients, and helping with immunity.

Peristalsis

• Peristalsis definition: Wave-like muscle movement that pushes food in one direction through the digestive tract.
• Peristalsis location: Occurs throughout the entire digestive system, including the esophagus, stomach, and intestines.
• Peristalsis function: move food from one part of the digestive tract to the next.

Segmentation

• Segmentation definition: Muscle contraction that mixes food and digestive juices. It does not move the food forward
• Segmentation Location: occurs mainly in the small intestine.
• Segmentation function: Mixes food with digestive enzymes and helps it break down, but does not push the food along.

Differences between Peristalsis and Segmentation

• Peristalsis moves food forward; while Segmentation mixes food but does not move it forward
• Peristalsis occurs throughout the digestive tract; segmentation mainly happens in the small intestine
• Peristalsis is a wave-like motion; segmentation is localized contractions focusing on mixing food.

Summary of Digestion Locations:

• Mouth: Mechanical and chemical digestion of carbohydrates.
• Esophagus: No digestion, just transport.
• Stomach: Mechanical digestion (churning) and chemical digestion (proteins).
• Small Intestine: Major site for digestion and nutrient absorption (fats, carbs, proteins, vitamins).
• Large Intestine: Water absorption and waste elimination.

Mechanical Digestion

• Definition: The physical breakdown of food into smaller pieces.
• How it works: - Chewing: teeth crush and grind food into smaller pieces - Churning: stomach muscles mix food and break it down into smaller bits. - Movement: peristalsis moves food through the digestive tract
• Goal: Break food into smaller parts to make it easier for enzymes to work during chemical digestion.

Chemical Digestion

• Definition: the breakdown of food into smaller molecules (nutrients) by enzymes and acids.
• How it works:
  • In the mouth: Saliva's amylase breaks down carbohydrates into sugars
  • In the stomach: Pepsin and hydrochloric acid break down proteins into smaller peptides.
  • In the small intestine: Enzymes from the pancreas (amylase, lipase, proteases) break down carbs, fats, and proteins, and bile helps break down fats. Goal: Chemically break down food into simple molecules (sugars, amino acids, fatty acids) for body absorption.

Differences Between Mechanical and Chemical Digestion

• Mechanical Digestion is the physical breakdown of food (chewing, churning). Chemical Digestion is breakdown of food using enzymes and acids.
• Mechanical doesn't change chemical structure; chemical breaks food down into simpler molecules (sugars, amino acids, fatty acids).
• Mechanical makes food smaller for enzymes; chemical makes food usable for the body for absorption action.

Catabolic Reactions

• Catabolic reactions definition: reactions that break down larger molecules into smaller ones.
• Catabolic reactions process: These reactions release energy because breaking down molecules releases energy stored in their bonds.
• Examples of catabolic reactions:
  • Digestion - breaking down food into nutrients.
  • Cellular Respiration - breaking down glucose to release energy (ATP).

Anabolic Reactions

• Anabolic reactions definition: reactions that build up smaller molecules into larger ones.
• Anabolic reactions process: These reactions require energy to create complex molecules from simpler ones.
• Examples of anabolic reactions:
  • Protein Synthesis - building proteins from amino acids.
  • Photosynthesis - Plants build glucose from carbon dioxide and water (requires energy).

Differences Between Catabolic (Breaking Down) and Anabolic (Building Up)

• Catabolic reactions break down large molecules into smaller ones and release energy.
• Anabolic reactions build larger molecules from smaller ones and require energy. - Example: - Catabolic: breaking down cellular respiration glucose - Anabolic: protein synthesis

Overview of the Large Intestine

• The large intestine is the final part of the digestive system
• The large intestine is responsible for absorbing water, storing waste, and eliminating it from the body.

Main Structures of the Large Intestine:

• Cecum: the beginning of the large intestine where the small intestine meets the large intestine. It receives waste from the small intestine and starts absorbing water.
• Appendix: A small pouch attached to the Cecum; thought to play an immune role.
• Colon: divided into four sections:
  • Ascending Colon: Goes up on the right side
  • Transverse Colon: Runs across
  • Descending Colon: Goes down the left side
  • Sigmoid Colon: S-section that connects to Rectum
  • Function: Absorb water, salts, and some vitamins to turn waste into more solids.
• Rectum: last part of the large intestine before the anus
• Anus: last part of the digestive tract that allows for elimination of feces.

Exothermic Reactions

• Definition: Releases energy in the form of heat or light.
• Energy is released to the surroundings.
• Examples: Burning wood and cell respiration.
  • Exo = Exit (Energy exits)

Endothermic Reactions

• Definition: Absorbs energy from surroundings in heat.
• Energy is absorbed into the system
  • i.e Sun absorption by plants or melting ice.
  • Endo = Enter (Energy enters)

Functions of the Stomach

• Storage: Stores food temporarily releasing it bit by bit into the small intestine.
• Mechanical Digestion: The churning with digestive juices of muscles for food mixture.
• Chemical Digestion: The production of gastric juices with hydrochloric acid and Pepsi that breaks down proteins.
• Protection: The lining of the stomach stores mucus to protect acidic components.

Stomach Structures

• Cardia: Where food from the esophagus enters to the stomach prevent acid reflux.
• Fundus: Rounded part that stores food and gas.
• Body: Mixes and churns central part of the digestive acids.
• Pylorus: Connects lower part with duodenum to small intestines that releases digested portions.
• Pyloric Sphincter: Ringed muscle that controls food openings.

Stomach Key Functions

• It stores, digests, protects what is from acid.

Summary of GI Structure Muscles

• Mouth & Esophagus Skeletal and smooth that have chewing, swallowing, and peristalsis functions.
• Stomach smooth muscles with churning and mixing from gastric juice function
• Small Intestine as smooth muscles with peristalsis and segmentation.
• Large intestine absorbs water and has smooth muscles with peristalsis and haustral components.
• Rectum and Anus: stores smooth rectum and skeletal anus muscles with storage and defecation capabilities
• Key Tip: Areas involving voluntary (chewing and defecation) have skeletal control. Smooth areas are automatic (digestion).

Parts of the Small Intestine

• Duodenum: First part where it has digestion and receives enzymes and components of the liver/pancreas.
• Jejunum: Middle part with primary absorption sites of carbs, proteins, fats.
• Ileum: Ends the small intestine where vitamins, acid and liquid are absorbed. It then proceeds to large intestine.
• Quick tip: Duodenum digests, Jejunum absorbs nutrients only, Ileum inputs what is remaining to the body.

Absorption of Water and Salts

• Large intestine helps with the water and salts absorption from liquid undigested material turning it into (feces).

Digestion Waste Storage

• Undigested material is stored until elimination.

Production of vitamins

• Large Intestine bacteria produces Vitamin B and K.

Feces Eliminations

• Large Intenstine forms stool by absorbing and is stored in rectums to be eliminated.

Reabsorption of the Large Intestine

• Large intestine helps reabsorb what water is with the most reabsorption in large intestine and the re-entering as liquids.
• Normal process large intestine 90% and creates solid
• Diarrhea where less is absorbed and stool is liquid. “Body cannot reclaim”

Plicae Circulares

• Circular folds are in lining small intestine and increases nutrients absorbed by reducing the movements.

Stomach Acidity

• pH is very acidic with usually 1.5 to 3.5.

Activation of Energy

• Enzymes lowers which speeds up chemicals.

Glucagon, Insulin, Somatostatin

• Glucagon raises sugar with liver absorption.
• Insulin helps cells that take in glucose, dropping sugars.
• Somatostatin balances blood by limiting glucagon and insulin.

Bile Details

• Digestive fluid that breaks down the liver fluids in small intensities.
• It gathers at the gal bladder until the time for digestion.

Sphincters

• Lower (LES) prevents acid and its esophagus.
• Pyloric Sphincter Controls food flow.
• Ileocecal Sphincter. Regulates flow to large intestine
• Anal Sphincters controls (releasing)

Stomach and Protections

• Protects with mucus that has cellular regeneration.

Mnemonics to Remember

• “Mucus makes barriers, HCI breaks down, (it protects with mucus and digestion of HCI with low level
• “Pepsin = Pfor proton, is acid” P in Chief is for food"

Segmentation

• Type of location is digestion where pattern of breaking down to move is present in intestine.

Pepsinogen

• The Pepsinogen is inactive form that breaks stomach proteins.
• Activated within acidic hydrochloric acid and the stomach can break down.
• Large intestine has less segmentation with movement with water, while small has more movement.