Digestion of Proteins: Protein digestion begins in the stomach with pepsin breaking down proteins into peptides, which are further digested into amino acids by enzymes like trypsin and peptidases in the small intestine.
The Pancreas: The pancreas has exocrine functions (digestive enzyme secretion) and endocrine functions (insulin and glucagon release), regulating both digestion and blood glucose levels.
Protein Digesting Enzymes: Enzymes like pepsin in the stomach and trypsin, chymotrypsin, and carboxypeptidase in the small intestine break proteins into peptides and amino acids for absorption.
Small Intestine: The small intestine, composed of the duodenum, jejunum, and ileum, is the primary site for digestion and nutrient absorption, featuring villi and microvilli to increase surface area.
The Esophagus: The esophagus is a muscular tube that transports food from the pharynx to the stomach via peristalsis, with its lining adapted to withstand friction and acidic reflux.
Tongue: The tongue is a muscular organ involved in taste, speech, and food manipulation, covered in papillae that contain taste buds and controlled by intrinsic and extrinsic muscles.
Accessory Organs: Accessory digestive organs include the liver, pancreas, gallbladder, and salivary glands, which secrete enzymes and other substances aiding digestion but are not part of the GI tract itself.
Stomach: The stomach is a muscular, J-shaped organ that secretes acid and enzymes to digest food mechanically and chemically, preparing it for absorption in the small intestine.
Histology of the Large Intestine: The large intestine’s histology includes a smooth mucosa with numerous goblet cells for mucus secretion, arranged in straight tubular glands and lacking villi.
Salivary Glands: The major salivary glands—parotid, submandibular, and sublingual—secrete saliva containing enzymes like amylase to begin starch digestion and lubricate food for swallowing.
Layers of the Gastrointestinal Tract: The GI tract consists of four layers: mucosa (innermost), submucosa, muscularis externa (smooth muscle), and serosa or adventitia (outer layer), each playing a role in digestion and motility.
Gallbladder: The gallbladder stores and concentrates bile produced by the liver, releasing it into the small intestine to aid in the digestion and absorption of fats.
Peristalsis: Peristalsis is the wave-like contraction of smooth muscles in the digestive tract that moves food through the esophagus, intestines, and other hollow organs.
Histology of Stomach: Stomach histology includes mucosal layers with gastric pits and glands containing cells that secrete acid, enzymes, and mucus, supported by muscularis layers for churning.
