Final answer:
The human digestive system includes various organs that orchestrate the digestion and absorption of nutrients. The enteric nervous system regulates the digestive processes, and the mucosal layer provides immunological protection. Experiencing the smell of food can activate a digestive reflex that primes the body for food intake.
Step-by-step explanation:
The human digestive system is composed of several major anatomical features, each with a specific function that contributes to the breakdown and absorption of nutrients. After ingestion, the process of propulsion moves the food along the alimentary canal, where mechanical and chemical digestion occurs. The major components of the digestive system include the mouth, pharynx, esophagus, stomach, small intestine, and large intestine, along with the accessory organs such as the liver, pancreas, and gallbladder. The absorptive process allows nutrients to enter the bloodstream and reach the body's cells.
Enteric Nervous System and Digestion
The enteric nervous system (ENS) supports digestion by regulating the gastrointestinal environment, managing digestive reflexes, and coordinating muscle contractions. Disruption of the autonomic nervous system, through stress for example, can negatively impact digestive functions, such as altering gastric secretions and motility.
Immunological Protection in the Digestive System
The mucosal layer of the alimentary canal contains immune cells that can protect against disease by identifying and responding to pathogens that enter with ingested food. This protective mechanism is an example of the gut's role in immune response.
Segmentation and Peristalsis
Segmentation in the small intestine improves nutrient absorption by mixing food with digestive juices, whereas peristalsis, the rhythmic contractions that move food along, slows down to allow more time for nutrient uptake.
Digestive Reflex Triggered by Smell
Encountering the aroma of freshly baked bread can stimulate a digestive reflex known as the cephalic phase response where the body prepares for the intake of food by increasing saliva production and stomach secretions, thus enhancing digestive efficiency.