Biology 112 - Final Exam Study Guide/Biology 112 - Final Exam Study Guide

What are the primary functions of the digestive system? • Ingestion, Secretion, Mixing and Propulsion (motility), Digestion, Absorption, Defecation. 2. What is the alimentary canal? • It is a continuous tube that extends from mouth to anus through the thoracic and abdominopelvic cavities. 3. What are the accessory organs of the digestive system? • Teeth, tongue, salivary glands, liver, gallbladder, and pancreas. 4. Describe, in detail, all the layers of the gastrointestinal system. You should be as specific as possible with respect to tissue types found, functions, etc. This is a very likely exam question, although I may ask you to refer more specifically to how this paradigm is modified in some subregions of the GI tract. Four layers of GI tract: Mucosa: It is the innermost layer of the GI tract, and is a mucous membrane. Subregions of Mucosa: 1. Layer of Epithelium: The epithelium in the mouth, pharynx, esophagus, and anal canal is nonkeratinized stratified squamous epithelium which serves as a protection. The epithelium that lines the stomach and small intestine is simple columnar epithelium which functions in secretion and absorption. 2. Lamina Propria: is areolar connective tissue, and containing many blood vessels and lymphatic vessels. Nutrients reach other tissues via these blood vessels. This layer supports the epithelium and binds it to muscularis mucosae. The lamina propria also contains Mucosa Associated Lymphatic Tissue (MALT). These specialized lymphatic tissues contain immune system cells that protect against disease. 3. Muscularis Mucosae: Thin layer of smooth muscle fibers throws the mucous membrane of the stomach and small intestine into many small folds, which increase the surface area for digestion and absorption. • Submucosa: It consists of areolar connective tissue that binds the mucosa to the muscularis. It contains many blood vessels that receive absorbed food particles. Submucosa is an extensive network of neurons known as the submucosal plexus. • Muscularis: Muscularis of mouth, pharynx, and superior part of the esophagus means upper respiratory system contains skeletal muscles that produce voluntary swallowing. o Throughout the rest of the tract, muscularis consists of smooth muscles that are generally found in two layers: circular fibers and longitudinal fibers. Involuntary contraction of the smooth muscles helps break down the food, and mix it with digestive secretion. o Between the two layers of muscularis is a second plexus of neurons called Myenteric Plexus. • Serosa: It is serous membrane composed of areolar connective tissues and simple squamous epithelium. The serosa is also called the visceral peritoneum because it forms a portion of the peritoneum. The esophagus has adventitia as its outer layer instead of serosa. 5. What is the brain guy axis? • The continuous feedback loop between sensory neurons in the gastrointestinal tract and motor response generated in the central nervous system. Hypersensitivity in the brain-gut axis contributes to functional GI disorders, including irritable bowel syndrome. 6. Describe the short reflex and long reflex pathways of the enteric nervous system. • Short reflex: reflexes from the gut to prevertebral sympathetic ganglia and then back to GI tract. These reflexes transmit signals long distance to other areas of the GI tract. • Long Reflexes: reflexes from the gut to spinal cord or brain stem and then back to GI tract. 7. Describe, in detail, the peritoneal cavity. This should include a detailed analysis of the 5 ‘folds’ of the cavity and their respective functions. • The slim space containing lubricating serous fluid that is between the parietal and visceral portions of the peritoneum is called the peritoneal cavity.