Digestive System Overview and Functions

Digestive System Overview

• The digestive system is an assembly line, breaking down nutrients for the body to use.
• Nutrients are broken down to smaller components like amino acids & monosaccharides.
• Food is processed through ingestion, digestion, absorption, compaction, and defecation.

Digestive System Functions

• Ingestion: The selective intake of food.
• Digestion: Mechanical and chemical breakdown of food into usable forms.
• Absorption: Uptake of nutrients into the bloodstream and lymph.
• Compaction: Absorbing water and consolidating indigestible material into feces.
• Defecation: Elimination of feces.

Digestive Tract

• The digestive tract is a muscular tube extending from the mouth to the anus.
• It includes the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
• The gastrointestinal tract (GI tract) comprises the stomach and intestines.
• Accessory organs to the digestive tract are teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

The Mouth (Oral Cavity)

• The mouth is also known as the oral or buccal cavity.
• Functions: ingestion, taste, sensory responses to food, mastication (chewing), speech, and respiration.
• Mechanical digestion begins in the mouth with chewing.

Salivary Glands

• 3 pairs of salivary glands outside the mucosa
• Intrinsic salivary glands are numerous and dispersed in oral tissues (e.g., lingual, buccal glands).
• Extrinsic salivary glands (parotid, submandibular, sublingual): secrete saliva constantly or in response to food.
• Saliva keeps the mouth moist & inhibits bacterial growth.

The Pharynx

• A muscular funnel connecting the oral cavity to the esophagus and nasal cavity to the larynx.
• Connects the digestive and respiratory tracts.
• Swallowing begins with the tongue and palate.

The Esophagus

• A muscular tube (~25-30 cm) posterior to the trachea.
• Connects the pharynx to the stomach.
• Carries swallowed food from pharynx to stomach.
• Controlled by nerves and brain stem.

The Stomach

• Located in the upper left abdominal cavity, inferior to the diaphragm.
• Primarily a food storage organ.
• Mechanically mixes and breaks down food.
• Liquefies food into chyme and begins chemical digestion of proteins & fats.
• Controlled by smooth muscles.

The Pylorus

• The end of the stomach.
• Surrounded by a thick ring of smooth muscle (pyloric sphincter).
• Regulates the passage of chyme into the duodenum.

The Small Intestine

• A coiled tube filling most of the abdominal cavity inferior to the stomach and liver.
• Three regions: duodenum, jejunum, and ileum (absorption primarily occurs here).
• Large surface area due to extensive folding and length.
• Nearly all chemical digestion and nutrient absorption happen here.
• Receives secretions from the liver and pancreas.

The Ileocecal Junction

• Where the ileum (small intestine) joins the cecum (large intestine).
• Ileocecal valve regulates the passage of food residue into the large intestine, preventing leakage back to the small intestine.

The Large Intestine

• Relatively large diameter, not its length.
• Receives about 500 mL of indigestible food residue.
• Absorbs water and salts.
• Eliminates feces (through defecation).
• Four regions: cecum, colon, rectum, anal canal.

The Liver

• Large, reddish-brown gland, inferior to the diaphragm.
• Largest gland in body.
• Important role in digestion (bile production).
• Detoxifies blood.

The Pancreas

• Located posterior to the stomach.
• Endocrine (hormones) and exocrine (enzymes) gland.
• Secretes pancreatic juice (digestive enzymes, bicarbonate).
• Empties into duodenum (small intestine).
• Aids in digestion of carbohydrates, proteins, and fats.

Explore the intricate workings of the digestive system, from ingestion to defecation. This quiz covers the essential functions and components of the digestive tract, including the roles of accessory organs. Test your knowledge on how nutrients are processed and absorbed by the body.