Overview of the Digestive System

Overview of the Digestive System

• Transforms complex foods (polysaccharides, fats, proteins) into simpler macromolecules (monosaccharides, fatty acids, amino acids).
• Composed of both extracellular and intracellular digestion processes.

Types of Digestion

• Extracellular digestion: Involves obtaining nutrients from food outside the body; occurs within the lumen of the alimentary canal.
• Intracellular digestion: A metabolic process that oxidizes fatty acids and glucose extracted from food during extracellular digestion.

The Alimentary Canal

• Also known as the GI tract, it consists of a passage from the mouth to the anus.
• Sphincters, smooth muscles surrounding the canal, allow for compartmentalization of digestive functions.

Breakdown of Food

• Digestion entails breaking down food into organic molecules.
• Starches and carbohydrates → monosaccharides.
• Lipids → free fatty acids.
• Glycerol and proteins → amino acids.

Digestion Mechanisms

• Two subgroups: mechanical (physical breakdown without chemical bond cleavage) and chemical (enzymatic cleavage of bonds like peptide and glycosidic bonds).

Absorption Process

• Involves extracting and transporting final digested products from the digestive tract into the circulatory system for tissue distribution.

Digestive Tract Components

• Oral cavity → pharynx → esophagus → stomach → small intestine → large intestine → rectum.

Accessory Organs

• Salivary glands, pancreas, liver, and gall bladder provide lubrication and enzymes crucial for digestion, collectively known as accessory organs.

Nervous System Regulation

• The enteric nervous system controls digestive function, comprising 100 million neurons within the digestive tract walls.
• Triggers peristalsis, the rhythmic contraction needed to move food through the system.

Peristalsis

• Rhythmic contraction of the gut tube, facilitated by the enteric nervous system.
• Governed by the autonomic nervous system, which can function independently of the brain and spinal cord.
• The parasympathetic division stimulates digestive activities while the sympathetic division inhibits them.