The Digestive System

A comprehensive set of flashcards covering terminology and definitions related to the digestive system, as presented in the lecture notes.

Gastroenterology

The study of the gastrointestinal system.

Ingestion

The process of taking in food and liquids.

Digestion

The breakdown of food into smaller, absorbable components.

Absorption

The process of taking digested nutrients into the blood or lymph.

Defecation

The elimination of feces from the digestive tract.

Alimentary Canal

The continuous tube that extends from the mouth to the anus.

Catabolism

The breakdown of larger molecules into smaller ones.

Anabolism

The process where smaller molecules are used to build larger ones.

Hydrolysis

The chemical breakdown of a compound due to reaction with water.

Mucosa

The innermost layer of the gastrointestinal tract, consisting of epithelium and connective tissue.

Submucosa

The layer of loose connective tissue that binds the mucosa to the muscularis. Also contains an extensive network of neurons known as the submucosal plexus of the enteric nervous system. It provides structural support and contains blood vessels, lymphatics, and glands.

Muscularis

The layer of muscle in the GI tract that facilitates the movement of food. The mouth, pharynx, superior and middle parts of the esophagus, and external anal sphincter contain skeletal muscle. The remaining portions, including the internal anal sphincter and throughout the rest of the tract, are arranged in inner circular and outer longitudinal sheets with the myenteric nerve plexus continuing between them, they consist of smooth muscle, allowing involuntary contractions and peristalsis.

Serosa

The outermost layer of the GI tract that includes the visceral peritoneum. If attached to surrounding tissues its call adventitia. If contained in the peritoneal cavity, it is called serose, which has a slippery mesothelium surface layer. The serosa is a smooth membrane that reduces friction between the digestive organs and surrounding structures. It provides a protective layer, supporting the abdominal organs within the peritoneal cavity.

Peritoneum

The body's largest serous membrane wraps around most abdominopelvic organs. The visceral peritoneum forms the “serosa” of the alimentary canal and covers other intra-abdominal organs. If then it continues around the abdominal wall as the parietal peritoneum. It contains supporting tissues, blood vessels, and nerves, serving to stabilize organ position while providing a frictionless environment for organ movement.

Ascites

Abnormal accumulation of fluid in the peritoneal cavity. This condition can lead to abdominal swelling and discomfort, often associated with liver cirrhosis, certain cancers or heart or kidney failure. High pressure in certain veins of the liver and low blood levels of a protein called albumin.

Haustral Churning

The process of mixing and squeezing the contents in the large intestine.

Chyme

The semi-fluid mass of partially digested food in the stomach.

Bolus

A soft mass of chewed food ready to be swallowed.

Intrinsic Factor

A glycoprotein necessary for the absorption of vitamin B12.

Chylomicrons

Transport particles that carry digested fats into the lymphatic system.

Duodenum

The first part of the small intestine, where most chemical digestion occurs.

Segmentation

A form of mechanical digestion in the small intestine that mixes food with digestive juices.

Villi

Finger-like projections in the small intestine that increase surface area for absorption.

Microvilli

Microscopic folds on the surface of the small intestinal epithelial cells that further increase surface area.

Mass Peristalsis

Strong contractions of the colon that move fecal matter towards the rectum.

Gastroesophageal Reflux Disease (GERD)

A chronic digestive condition where stomach acid flows back into the esophagus.

Peristalsis

The wave-like muscle contractions that move food along the digestive tract.

MALT

Mucosa Associated Lymphatic Tissue is lamina propria containing prominent lymphoid tissue. that protect against disease.

Muscularis Mucosae

Underneath MALT, a thin layer of smooth muscle that folds the lining of the stomach and small intestines. It aids in the movement of mucosal layer and helps in the regulation of digestive secretions.

Visceral peritoneum

The visceral peritoneum is a thin membrane that covers and adheres to the outer surface of the abdominal and pelvic organs, providing a protective layer. It is part of the peritoneum, the body's largest serous membrane, which lines the abdominal cavity. The visceral peritoneum plays a critical role in supporting the organs, reducing friction between them, and facilitating the movement of these organs during digestion and other bodily functions. It also contains blood vessels, nerves, and lymphatics that supply the organs it envelops.

Enteric nervous system

A complex network of neurons, interneurons, sensory neurons, chemoreceptors, and stretch receptors that governs the function of the gastrointestinal tract, controlling digestion and gut motility independently of the central nervous system. ~100M neurons extend from the esophagus to the anus. Has two plexuses: the Myenteric plexus (between longitudinal and circular layers of the muscularis muscle) and the Submucosal plexus (in the submucosa), coordinating peristalsis and secretions.

Autonomic nervous system

The autonomic nervous system regulates the neurons of the enteric nervous system (ENS) and is innervated by sympathetic and parasympathetic nerves, playing a crucial role in controlling involuntary bodily functions, including digestion.

GI Reflex Pathways

Made of many neurons of ENS. Regulate GI secretions, motility, and blood flow to the gastrointestinal tract, ensuring efficient digestion and absorption.

5 Folds of Pericardium

1. Greater Omentum

2. Falciform ligament

3. Lesser Omentum

4. Mesentery

5. Mesocolon

Falciform Ligament

A thin fold of peritoneum that attaches the liver to the anterior abdominal wall and diaphragm, helping to stabilize the position of the liver.

Retroperitoneal and organs

Located behind the peritoneum are the kidneys, ureters, most of the pancreas, ascending and descending colons, duodenum, adrenal glands, aorta, and inferior vena cava.

3 Overlapping Phases of GI Tract digestive activities

The three phases are the Cephalic phase, Gastric phase, and Intestinal phase, each controlling different aspects of digestion and absorption in response to food intake. The phases involve complex neural and hormonal regulation to optimize digestive processes, with each phase being triggered by different stimuli.

Oral of Buccal Cavity

The oral or buccal cavity is the initial part of the digestive system where food enters the body, consisting of the lips, cheeks, gums, teeth, tongue, and floor and roof of the mouth. It plays a crucial role in the mechanical digestion of food through mastication and breakdown of food through chewing, and the beginning of digestion through saliva.