Introduction to GI Physiology: General Organisation of the GI Tract

Practice flashcards covering the functional anatomy, motility, electrical activity, and hormones of the gastrointestinal tract based on Lecture 1.

What components make up the digestive system?

The gastrointestinal tract (GIT) and accessory organs of digestion, including teeth, tongue, salivary glands, liver, and the exocrine part of the pancreas.

What is the approximate length of the gastrointestinal tract?

About $10\,m$ ($30\,ft$).

What are the two subdivisions of the oral cavity?

The vestibule (lying between the lips/cheeks and gums/teeth) and the oral cavity proper (lying within the alveolar arches, gums, and teeth).

How long is the esophagus, and what sphincters are located at its junctions?

It is about $25\,cm$ long, with the upper esophageal sphincter at the pharynx junction and the lower esophageal sphincter at the stomach junction.

What are the four parts of the stomach?

Cardia, fundus, corpus/body, and antrum.

What are the three parts of the small intestine and their respective lengths according to the transcript?

Duodenum ($~25\,cm$), Jejunum ($~25\,m$), and Ileum ($3.5\,m$).

What structures are included in the large intestine?

Caecum, Appendix, Ascending colon, transverse colon, descending colon, sigmoid colon, Rectum, and anal canal.

What are the four major processes of the digestive function?

1. Ingestion, 2. Digestion, 3. Absorption, and 4. Egestion (defecation).

What constitutes the immune role of the gastrointestinal system?

Lymphoid tissue in the tonsils, adenoids, and Peyer's patches, providing humoral and cellular immunity.

Why does gastrointestinal smooth muscle function as a syncytium?

Smooth muscle fibers are electrically connected through gap junctions, allowing ions to move from one cell to the next so the muscle contracts as a whole mass.

What is the range for the resting membrane potential (RMP) of gut smooth muscle?

Between $-50$ and $-60\,mV$.

What are the frequencies of slow waves in the stomach, duodenum, and terminal ileum?

Stomach: $3/min$; Duodenum: $12/min$; Terminal ileum: $8-9/min$.

At what electrical threshold do spike potentials occur in GIT smooth muscle?

When the resting membrane potential becomes more positive than about $-40\,mV$.

Which channels are primarily responsible for the action potentials in GIT smooth muscle?

Calcium-sodium channels.

What are the two functional types of gastrointestinal movements?

1. Propulsive movements (peristalsis) and 2. mixing movements.

What is the usual stimulus for intestinal peristalsis?

Distention of the gut.

Provide an example of a gastrointestinal reflex integrated entirely within the gut wall.

Reflexes that control gastrointestinal secretion, peristalsis, and mixing contractions.

What is the gastrocolic reflex?

A reflex from the stomach to the prevertebral sympathetic ganglia and back to the GIT that causes evacuation of the colon.

Which hormones are included in the Gastrin family?

Gastrin and Cholecystokinin ($CCK-PZ$).

Which cells secrete Secretin and what are the stimuli for its secretion?

S cells of the duodenum; stimulated by acid and fatty acids.

Which hormone is secreted by G cells of the gastric antrum?

Gastrin.