Mouth → pharynx → esophagus → stomach → small intestine (duodenum, jejunum, ileum) → large intestine (cecum/colon) → rectum → anal canal. Accessory organs include teeth/tongue, salivary glands, liver, gallbladder and pancreas.
Ingestion · propulsion/swallowing/peristalsis · mechanical digestion · chemical digestion · absorption · defecation. Segmentation mixes intestinal contents; peristalsis propels them.
Stores and mechanically mixes food. Gastric secretions include hydrochloric acid, pepsinogen and intrinsic factor. Protein digestion begins substantially here, but most nutrient absorption occurs later in the small intestine.
The small intestine is the major site of digestion and nutrient absorption. Circular folds, villi and microvilli greatly increase absorptive surface area.
Liver: produces bile and performs many metabolic/detoxification/storage functions. Gallbladder: stores/concentrates bile. Pancreas: exocrine enzymes/bicarbonate enter duodenum; endocrine islets regulate glucose.
Absorbs water/electrolytes, houses extensive microbiota and compacts/stores fecal material. It is not the primary site of nutrient absorption.
Abdominal work requires specific consent, comfortable positioning and awareness of organs, aorta and symptoms. Severe unexplained abdominal pain, acute inflammatory/infectious conditions, recent surgery or suspected emergency are not invitations for deeper abdominal massage.