The Digestive System Overview

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

The mechanism by which food is moved through the digestive tract.

The first part of the small intestine where most chemical digestion occurs.

The middle section of the small intestine primarily involved in nutrient absorption.

The final section of the small intestine, responsible for absorbing remaining nutrients and bile acids.

Cells lining the small intestine responsible for absorbing nutrients.

Specialized cells in the small intestine that produce mucus to protect the intestinal lining.

Cells located at the base of intestinal crypts that secrete antimicrobial peptides to defend against infections.

Specialized cells in the large intestine that absorb water and electrolytes from the remaining indigestible food matter.

The primary function of the large intestine is to absorb water and electrolytes from the remaining indigestible food matter and form and store feces until defecation.

The pancreas has both endocrine and exocrine functions, producing digestive enzymes (amylase, lipase, proteases) for digestion and bicarbonate to neutralize stomach acid in the duodenum.

Bile is produced by the liver and stored in the gallbladder, released into the duodenum to aid in the digestion and absorption of fats.

Simple sugars (monosaccharides) are absorbed directly into the bloodstream through the enterocytes in the small intestine.

Amino acids and small peptides are absorbed into the bloodstream via active transport mechanisms in the enterocytes.

Fatty acids and monoglycerides are absorbed into the enterocytes, reassembled into triglycerides, packaged into chylomicrons, and transported into the lymphatic system before entering the bloodstream.

Vitamins A, D, E, and K are absorbed with dietary fats in the small intestine. They are stored in the body for longer periods.

Vitamins B and C are absorbed directly into the bloodstream. They are not stored in the body for long and need to be replenished regularly.

Minerals, such as calcium, iron, and zinc, are absorbed through various mechanisms depending on the mineral. They are essential for many bodily functions.

The cephalic phase is initiated by sensory cues (sight, smell, taste, thought) and prepares the digestive system for food intake.

The gastric phase begins when food enters the stomach and involves the secretion of gastric juices (including hydrochloric acid and pepsin) to break down food.

The intestinal phase begins when chyme (partially digested food) enters the small intestine. It involves hormone release to regulate digestion and nutrient absorption.

Leptin signals the brain to decrease appetite and increase energy expenditure, helping to regulate body weight. It is produced by adipose tissue.

Ghrelin stimulates appetite by signaling the brain when the stomach is empty. It is primarily produced by the stomach.

The minimum amount of energy required to maintain basic life functions when at rest in a neutral environment.

A unit of energy. Calories in nutrition represent the amount of energy provided by food and drinks.

A measure of body fat based on height and weight that applies to adult men and women. Calculated by dividing weight in kilograms by the square of height in meters (kg/m²).

A normal BMI falls between 18.5 and 24.9.

A BMI under 18.5 indicates a person is underweight.

A BMI between 25 and 29.9 indicates a person is overweight.

A BMI of 30 or above indicates a person is obese.

The process of breaking down food into smaller molecules that the body can absorb and use.