L18 Ch25 Digestive System

Comprehensive flashcards covering the components, functions, microscopic structure, and aging effects of the digestive system based on the lecture transcript.

What are the two main categories that the digestive system can be broadly divided into?

The digestive tract (elementary canal) and the accessory organs.

Which organs are part of the continuous tube known as the digestive tract or elementary canal?

The oral cavity, the pharynx, the esophagus, the stomach, the small intestine, and the large intestine.

Which organ is the primary site of nutrient absorption?

The small intestine.

What are the three pairs of major salivary glands?

The parotid gland, the sublingual gland, and the submandibular gland.

What are the basic building blocks that carbohydrates, lipids, and proteins are broken down into during digestion?

Carbohydrates into monosaccharides, lipids into fatty acids and glycerols, and proteins into amino acids.

What are the four main layers of the digestive tract from the lumen inward?

The mucosa, the submucosa, the muscular layer (muscularis externa), and the serosa or adventitia.

What type of epithelium is found in areas exposed to abrasion, such as the oral cavity, pharynx, and esophagus?

Stratified squamous epithelium.

What type of epithelium is specialized for secretion and absorption in the stomach and small intestine?

Simple columnar epithelium.

What are the two sublayers of smooth muscle in the muscularis externa?

The circular muscle layer and the longitudinal muscle layer.

What specialized cells in the digestive tract can initiate muscle contraction without a signal from the nervous system?

Pace setter cells.

What is the primary difference between peristalsis and segmentation?

Peristalsis involves coordinated contractions that propel a bolus forward through the tract, while segmentation involves localized contractions that mix and churn food with enzymes.

What are mesenteries?

Double layers of peritoneum that stabilize the position of digestive organs and provide pathways for blood vessels, nerves, and lymphatic vessels.

What is the function of the mesentery proper?

It suspends most of the small intestine, specifically the jejunum and the ileum, anchoring it to the posterior abdominal wall.

What substance covers the crown of the tooth and is considered the hardest substance in the body?

Enamel, which is made of calcium phosphate crystals.

What are the four types of teeth found in adults?

Incisors, canines (cuspids), premolars (bicuspids), and molars.

What is the total number of permanent teeth in a full adult set?

$32$.

What are the three distinctive phases of swallowing (deglutition)?

The buccal phase, the pharyngeal phase, and the esophageal phase.

What are the four regions of the stomach?

The fundus, the cardia, the body, and the pyloric part.

What are the rugae (gastric folds) in the stomach?

Folds in the mucosal layer that allow the stomach to expand significantly when filled with food.

What are the three regions of the small intestine and their approximate lengths?

The duodenum ($10\,\text{in}$), the jejunum ($8\,\text{ft}$), and the ileum ($12\,\text{ft}$).

What three features work together to increase the surface area for absorption in the small intestine?

Plicae circulares (circular folds), villi, and microvilli.

Which structure controls the flow of chyme from the ileum to the cecum?

The ileocecal valve.

What are the three distinct bands of longitudinal muscle in the large intestine that create hostra?

Teniae coli.

Compare the internal and external anal sphincters.

The internal anal sphincter is composed of smooth muscle and is involuntary; the external anal sphincter is composed of skeletal muscle and is voluntary.

From which two sources does the liver receive blood?

The hepatic artery proper (oxygenated blood) and the hepatic portal vein (nutrient-rich blood).

What are the two main types of cells in the pancreas and their functions?

Pancreatic acinar cells (exocrine function, secreting digestive enzymes) and pancreatic islet cells (endocrine function, secreting insulin and glucagon).

How does aging affect the digestive system's stem cell reproduction and motility?

Declining stem cell reproduction leads to decreased tissue repair and increased fragility, while decreased smooth muscle tone reduces motility (peristalsis and segmentation) leading to constipation.