Digestion Flashcards

Vocabulary flashcards for the digestion lecture.

Digestion

The process of breaking down food into smaller molecules that can be absorbed by the body.

Absorption

The process by which digested nutrients move from the digestive tract into the bloodstream or lymphatic system.

Elimination

The removal of undigested waste materials from the body.

Mechanical Digestion

The physical breakdown of food into smaller pieces, increasing its surface area.

Chemical Digestion

The enzymatic breakdown of food molecules into smaller chemical components.

Enzymatic Hydrolysis

A chemical process in which enzymes catalyze the breakdown of biomolecules by adding water.

Active Transport

The movement of molecules across a cell membrane against their concentration gradient, requiring energy.

Passive Diffusion

The movement of molecules across a cell membrane from an area of high concentration to an area of low concentration, without energy.

Facilitated Diffusion

The movement of molecules across a cell membrane with the help of a carrier protein, without energy.

Co-transport

The movement of two or more molecules across a cell membrane together, using a single carrier protein.

Endocytosis

The process by which cells engulf substances from their surroundings by forming vesicles.

Monomers

Small, repeating units that make up larger biomolecules.

Alimentary Canal

The continuous tube in the digestive system through which food passes.

Accessory Digestive Organs

teeth, tongue, gallbladder, and digestive glands.

How is smooth muscle different from skeletal and cardiac muscle?

Smooth muscle has no striations (no sarcomeres), are spindle-shaped, cell-to-cell attachments

How is smooth muscle similar to cardiac muscle?

single, central nucleus, autorhythmic, involuntary

Interstitial Cells of Cajal

Non-neural cells found in circular muscle that produce slow waves to coordinate contractions in the gut.

Calmodulin

A calcium-binding protein involved in smooth muscle contraction.

Myosin Light Chain Kinase (MLCK)

An enzyme that phosphorylates myosin, enabling it to form cross-bridges with actin in smooth muscle.

Dense Bodies

Structures in smooth muscle that hold actin in place and act as attachment points to adjacent cells.

Bolus

A ball-like mixture of food and saliva that is formed in the mouth during chewing.

Chyme

The acidic, semi-liquid mixture of partially digested food and gastric juices that passes from the stomach to the small intestine.

Ingestion

The act of taking food or drink into the body through the mouth.

Propulsion

The movement of food through the digestive tract.

Peristalsis

Wave-like muscle contractions that propel food through the digestive tract.

Mechanical Breakdown

The physical breakdown of food into smaller pieces to increase surface area for digestion.

Digestion

The chemical breakdown of food into smaller molecules that can be absorbed.

Absorption

The process by which digested nutrients are taken into the bloodstream or lymphatic system.

Defecation

The elimination of undigested waste material from the body.

Peritoneum

The serous membrane lining the abdominal cavity and covering the abdominal organs.

Mesentery

A double layer of peritoneum that supports and suspends the abdominal organs.

Mucosa

The innermost layer of the GI tract, composed of epithelium, lamina propria, and muscularis mucosae.

Epithelium

The layer of cells lining the surfaces of the body, including the GI tract, involved in secretion and absorption.

Lamina Propria

A layer of loose connective tissue in the mucosa that supports the epithelium and contains lymphoid follicles.

Muscularis Mucosae

A thin layer of smooth muscle in the mucosa that contributes to movement and folding of the GI lining.

Submucosa

A layer of connective tissue in the GI tract containing blood vessels, lymphatic vessels, and nerve plexuses.

Muscularis Externa

The layer of smooth muscle in the GI tract responsible for peristalsis and segmentation. Two layers include the circular and longt

Serosa

The outermost layer of the GI tract, composed of connective tissue.

Simple Columnar Epithelium

Type of epithelial tissue found lining the GI tract, mucus protects digestive enzymes and eases passage of food. 

What is the lamina propria of the mucosa layer? What does it contain and what is its connection to other systems of the body like the lymphatic and nervous system? 

Loose areolar connective tissue supports epithelium. Contains lymphoid follicles and serves as defense against pathogens 

Elastin

A protein that allows the gut to expand and retract.

Collagen

A protein that provides structural support.

Myenteric Plexus

An intrinsic nerve plexus located between the longitudinal and circular smooth muscle layers of the GI tract.

Submucosal Plexus

An intrinsic nerve plexus located within the submucosa of the GI tract.

Enteric Nervous System

The intrinsic nervous system of the GI tract.

Splanchnic Circulation

The blood flow to the abdominal organs, including the liver, spleen, stomach, and intestines.

Celiac Artery

A major artery that branches from the aorta and supplies blood to the liver, spleen, and stomach.

Hepatic Portal Vein

A vessel that carries blood from the GI tract, gallbladder, pancreas, and spleen to the liver.

What role does pH play in the GI?

Plays a role in the breaking down of food and absorption of nutrients

Uvula and epiglottis

Work together to prevent food from entering nasal cavity

Tongue

Grips/mixes food, forms bolus, initiates swallowing.

Intrinsic Nerve Plexi

The nerve networks within the walls of the digestive tract that control motility and secretion.

Extrinsic Nerve Plexi

Nerve networks outside the digestive tract that influence digestive functions.

Slow Wave Potentials

Rhythmic electrical oscillations in smooth muscle cells that can trigger muscle contractions.

Salivary Amylase

An enzyme in saliva that breaks down carbohydrates.

Lingual Lipase

An enzyme in saliva that breaks down fats.

Lysozyme

An antimicrobial enzyme found in saliva.

Gastric Secretions

Secretions from the stomach that create an acidic environment for digestion.

What are gastric sections? What stimulates/inhibits them?

Gastric secretions inhibit salivary amylase and lingual lipase. Stimulation: gastrin, histamine, and acetylcholine. Inhibited by: somatostatin, secretin, and lower stomach pH.

Parietal Cells

Cells in the stomach that secrete hydrochloric acid (HCl).

Chief Cells

Cells in the stomach that secrete pepsinogen.

Pepsinogen

The inactive precursor of pepsin, a protein-digesting enzyme.

Goblet Cells

Cells that secrete mucus.

Enteroendocrine Cells

Endocrine cells that secrete gastrin.

Cephalic Phase

The phase of gastric secretion and motility that is triggered by the senses of food.

Gastric Phase

The phase of gastric secretion and motility that is triggered by the entry of food into the stomach.

Intestinal Phase

The phase of gastric secretion and motility that is triggered by the entry of chyme into the small intestine.

CCK (Cholecystokinin)

A hormone secreted by the small intestine that stimulates the release of bile.

Liver

The functions are to produce and secrete bile, metabolize carbs, lipids, proteins, removal of drugs and hormones, storage, phagocytosis, activation of vitamins.

Gallbladder

Stores and concentrates bile until needed in small intestines.

Pancreas

Secretes pancreatic juice.

Pancreatic Juice

Contains bicarbonate ions and digestive enzymes.

Where does the most absorption take place?

Small intestine

Major organs of GI tract

Mouth, esophagus, stomach, small intestine, large intestine 

How many layers of smooth muscle are found throughout the gut?

2 layers: circular and longitudinal

How many layers of smooth muscle in the stomach?

3: inner oblique, middle circular, and outer longitudinal

What is the manner of cross bridge formation in smooth muscle?

1. Ca2+ enters cell from ECF or SR. 2. Ca2+ binds to and activates calmodulin. 3. Calmodulin activates myosin light chain kinase (MLCK). 4. MLCK phosphorylates (activates) myosin. 5. Myosin forms cross-bridges to actin and shortens muscle 

What is the difference between propulsion and peristalsis? How does digested materials only move in one direction for most of the GI (unless there is a problem)? 

Propulsion is the movement of food while peristalsis is the contraction and relaxation of food. The canal contracts behind the food 

What are the three major actions of mechanical breakdown of food and where does each occur?

Chewing (in the mouth), churning (in the stomach), segmentation (small intestine) 

How is segmentation different from peristalsis? 

It moves food in both directions