Human Anatomy: Digestive System Quiz

Digestive System Overview

• The digestive system is a disassembly line, breaking down nutrients into usable forms for the body.
• It absorbs these nutrients, distributing them to the tissues.
• Most food cannot be directly used; it needs to be broken down into smaller components (e.g., amino acids, monosaccharides).
• These smaller components are universal to all species.

Digestive System Functions

• Ingestion: Intake of food.
• Digestion: Mechanical and chemical breakdown of food to absorbable forms.
• Absorption: Uptake of nutrients into the blood and lymph.
• Compaction: Absorbing water to form feces.
• Defecation: Elimination of feces.

Digestive Tract Anatomy

• Includes the mouth, pharynx, esophagus, stomach, small intestine, and large intestine; also known as the alimentary canal/gut.
• The stomach and intestines are part of the gastrointestinal (GI) tract.
• Accessory organs include teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

The Mouth (Oral Cavity)

• Also known as the buccal cavity.
• Functions include ingestion, tasting, chewing (mastication), swallowing, speech, and respiration.
• Lined by the cheeks, palate, and tongue.
• Mechanical digestion begins with teeth.

Salivary Glands

• Three pairs of larger, discrete organs outside the oral mucosa.
• Communicate with the oral cavity through ducts.
• Parotid glands are located anterior to the earlobe; their duct pierces the buccinator and opens opposite the second upper molar tooth.
• Submandibular glands are located along the body of the mandible, just deep to the mylohyoid muscle; their duct empties into the mouth near the lower central incisors.
• Sublingual glands sit in the floor of the mouth; they have multiple ducts that lead into the mouth posterior to the submandibular duct papilla.
• Intrinsic salivary glands, like lingual, labial, and buccal glands, are smaller and dispersed within the oral tissues.
• Saliva helps moisten the mouth and inhibit bacterial growth.

The Pharynx

• A muscular funnel connecting the oral cavity to the esophagus and the nasal cavity to the larynx.
• Connects the digestive and respiratory tracts.
• Swallowing action is initiated by tongue and palate.

The Esophagus

• A straight muscular tube (25-30cm).
• Located posterior to the trachea.
• Connects the pharynx to the stomach.
• Passes through the esophageal hiatus in the diaphragm.

The Stomach

• A muscular sac primarily for food storage.
• Mechanically breaks up food, liquefies it, and initiates the chemical digestion of proteins and fats.
• Produces chyme (pasty mixture of digested food).
• Empties partially digested food into the duodenum, the first part of the small intestine.
• Controlled by the pyloric sphincter, a thick ring of smooth muscle.

The Small Intestine

• A coiled mass filling most of the abdominal cavity interior to the stomach and liver.
• Divided into duodenum, jejunum, and ileum.
• Absorption of nutrients occurs here, through extensive folding of the mucosa and its length.
• Chyme from the stomach enters the duodenum.

The Ileocecal Valve

• Located at the junction of the ileum (small intestine) and the cecum (large intestine).
• The thickened ileum muscle at this junction.
• Controls the flow of undigested material into the large intestine, preventing backflow.

The Large Intestine

• Receives undigested material from the small intestine.
• Absorbs water and salts, forming feces.
• Eliminates undigested waste (defecation).
• Consists of cecum, colon, rectum, and anal canal.
• Absorbs water and salts to compact feces and aid in the excretion process

The Liver

• The body's largest gland.
• Produces bile, which aids in fat emulsification.
• Breaks down dietary fats into smaller particles.
• Helps with detoxifying the blood by processing and removing toxins.
• Contributes to metabolism and numerous other metabolic processes.

The Pancreas

• A spongy digestive gland posterior to the stomach's greater curvature.
• Has both exocrine and endocrine functions.
• Secretes pancreatic juice (alkaline mixture water, sodium bicarbonate, other electrolytes, and enzymes) into the duodenum, aiding in digestion.
• Endocrine structures (pancreatic islets) produce hormones like insulin and glucagon that regulate blood sugar levels.