Digestive System Chapter 23.1 Quiz

Digestive System Overview

• The digestive system, also known as the alimentary canal or gastrointestinal (GI) tract, is about 25 ft long from mouth to anus.
• It has 4 layers: mucosa, submucosa, muscularis, and serosa.
• The system includes the mouth, pharynx, esophagus, stomach, small and large intestines, and accessory digestive organs like teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

Nerve Supply

• The enteric nervous system runs from the esophagus to the anus and is separated into two plexuses: myenteric and submucosal.
• The autonomic nervous system (sympathetic and parasympathetic nerves) extrinsically innervates the alimentary canal.

Blood Supply

• The hepatic portal system transports proteins and carbohydrates to the liver.
• The system delivers nutrients and oxygen to organs of the alimentary canal.
• While resting and digesting, 25% of blood pumped enters arteries serving the intestines.

The Peritoneum

• The peritoneum holds digestive organs in place and has two different regions: parietal peritoneum (lines the abdominal wall) and visceral peritoneum (envelops abdominal organs).
• The peritoneal cavity is the space between the parietal and visceral peritoneum.

Digestive System Processes and Regulation

• The mouth ingests, chews, and mixes food, begins chemical breakdown of carbs and lipids, and moves food to the pharynx.
• The pharynx propels food to the esophagus and lubricates food and passage.
• The esophagus propels food to the stomach and is attached to the mandible, styloid processes, and hyoid bone.

Salivary Glands

• Salivary glands secrete 1-1.5 L of saliva per day, even while sleeping, and produce more while eating.
• Saliva is 95.5% water, 4.5% ions, glycoproteins, enzymes, growth factors, and waste, with a pH of 6.35-6.85.
• Saliva contains IgA and is regulated by the autonomic nervous system.

Teeth

• There are two sets of teeth: 20 deciduous (baby) teeth and 32 permanent teeth.
• Teeth include 8 incisors, 4 cuspids (canines), 8 premolars, and 12 molars, with the third molars (wisdom teeth) erupting toward early adulthood.

Tooth Anatomy

• Gingivae (gums) and the periodontal ligament hold teeth in the socket.
• The tooth consists of the crown, root, pulp cavity, and cementum.
• A cavity is a colony of bacteria feeding on sugar that degrades the enamel.

The Pharynx (Throat)

• The pharynx handles food and air by involuntary muscle contraction and consists of three parts: nasopharynx, oropharynx, and laryngopharynx.
• The epiglottis is pulled over the larynx during swallowing to prevent food from entering the trachea.

The Esophagus

• The esophagus is a muscular tube connecting the pharynx to the stomach, measuring 10 inches in length.
• The esophagus secretes mucous and does not secrete digestive enzymes, with any digestion due to bacteria.

Feces

• Feces consist of undigested food residue, unabsorbed substances, bacteria, old cells from the GI mucosa, inorganic salts, and some water.
• The Valsalva maneuver is a voluntary procedure to remove feces, increasing intra-abdominal pressure.

Accessory Organs

Liver

• The liver receives nutrients from the small intestine through the hepatic portal vein.
• Hepatocytes produce bile, which moves to the common hepatic duct and joins with the common bile duct into the small intestine.
• Bile is essential for emulsification (breakdown) of lipids in the small intestine, and its salts are reabsorbed in the ileum.
• Bilirubin is the main bile pigment, giving stool its color after encountering intestinal bacteria.

The Pancreas

• The pancreas has both exocrine and endocrine functions.
• The pancreas secrets digestive enzymes and hormones like gastrin.