1. Ingestion: Food is taken into the body through the mouth or other specialized structures.
2. Digestion: The ingested food is broken down into simpler, soluble molecules through mechanical and chemical processes. Mechanical digestion involves physical breakdown of food into smaller particles through chewing (in animals with teeth) or muscular contractions of the digestive tract. Chemical digestion involves the action of enzymes to break down complex molecules into simpler forms that can be absorbed.
3. Absorption: The digested food molecules are absorbed through the walls of the digestive tract into the bloodstream or lymphatic system, where they can be transported to cells throughout the body.
4. Assimilation: Once absorbed, the nutrients are utilized by cells for energy, growth, and repair.
5. Egestion: Undigested food residues, along with waste products, are expelled from the body through the anus.
Humans and many other animals exhibit holozoic nutrition, where they consume complex organic matter (such as plants or other animals), digest it internally, and absorb the resulting nutrients for energy and growth.
