Digestive System Overview

Digestive System Overview

• The digestive system is a disassembly line, breaking down nutrients into usable forms for the body and absorbing them.
• Nutrients are broken down into smaller components like amino acids and monosaccharides.
• These components are universal to all species.

Digestive System Functions

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

The Digestive Tract

• It extends from the mouth to the anus.
• Also known as the alimentary canal or gut.
• Includes the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
• The stomach and intestines comprise the gastrointestinal (GI) tract.

Accessory Organs

• Teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

The Mouth (Oral Cavity)

• Also known as the buccal cavity.
• Ingestion, taste, mastication (chewing), speech, and respiration.
• Oral cavity is lined by the cheeks, lips, palate, and tongue.
• Mechanical digestion by teeth and tongue.
• Chewing, swallowing, and respiration happens here.

Salivary Glands

• Three major pairs: parotid, submandibular, and sublingual.
• Intrinsic salivary glands are numerous, small, and dispersed throughout the oral tissues (lingual, labial, and buccal).
• Secrete saliva at relatively constant rate.
• Keeps the mouth moist and inhibits bacterial growth.

The Pharynx

• Muscular funnel connecting oral and nasal cavities to the esophagus and larynx.
• Junction of digestive and respiratory systems.
• Swallowing occurs here, driven by tongue and palate.

The Esophagus

• Muscular tube (25-30 cm).
• Posterior to the trachea.
• Connects pharynx to the stomach.
• Transports food from pharynx to stomach.

The Stomach

• Muscular sac in the upper left abdominal cavity.
• Primarily for food storage.
• Mechanically breaks down food into smaller particles.
• Liquefies food.
• Begins chemical digestion of proteins and fats.
• Chyme (pasty mixture) is formed.

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

• Coiled mass in the abdominal cavity, mostly beneath the stomach and liver.
• Divided into three regions: duodenum, jejunum, and ileum.
• Primary site of nutrient absorption.
• Extensive surface area for efficiency.
• Nearly all chemical digestion and nutrient absorption occurs here.

The Ileocecal Junction

• Junction of the ileum and cecum (large intestine).
• Ileocecal valve regulates movement of food residue into the large intestine.

The Large Intestine

• Relatively large diameter, not long.
• Four regions: cecum, colon (ascending, transverse, descending, sigmoid), rectum, and anal canal.
• Absorbs water and salts, forming feces.
• Eliminates feces by defecation.

The Liver

• Largest gland.
• Reddish-brown color; below diaphragm.
• Crucial for digestion (bile secretion).
• Detoxifies blood; major metabolic role.
• Bile emulsifies fats.

The Pancreas

• Spongy digestive gland, behind stomach.
• Endocrine and exocrine functions.
• Endocrine part (pancreatic islets) secretes insulin and glucagon.
• Exocrine part secretes pancreatic juice.
• Pancreatic juice is alkaline (bicarbonate).
• Contains various enzymes for digestion.

Explore the intricate functions of the digestive system, from ingestion to defecation. Learn about the digestive tract, its accessory organs, and how nutrients are processed in the body. This quiz covers essential concepts fundamental to understanding human biology.