GI System 1 Flashcards
Main role of the GI Tract
to transfer water & nutrients from food into the body
GI Tract Main Organs
- Oral Cavity
- Esophagus
- Small Intestine
- Rectum
- Stomach
- Large Intestine
Oral Cavity Function
Digstion
- only carbs
- salivary amylase & chewing
Esophagus Function
passage to stomach
Stomach Function
continued digestion
- only proteins
- chyme churned & pepsin
Small Intestine Function
- most digestion & absorption
- only chemical, lipids, carbs, proteins
- pancreatic enzymes
Large Intestine Function
- colon absorbs water and electrolytes, produces feces
- rectum houses gut microflora
GI Tract Sphincters
- Upper Esophageal Sphincter
- Lower Esophageal Sphincter
- Pyloric Sphincter
- Ileocecal Sphincter
- Internal/External Anal Sphincters
- internal = smooth muscle & autonomic
- external = skeletal muscle & controlled
Layers of the GI Tract
- Mucosa
- Submucosa
- Muscularis Externa
- Serosa
Mucosa
- Epithelium - single layer epithelial cells with transporting/secretory/stem cells (ions/water/enzymes/mucus)
- Lamina Propria - loose connective tissue (blood supply/nerves)
- Muscularis Mucosae - thin layer of smoorh muscle, can contract for absorption
Submucosa
- loose connective tissue
- submucosal plexus (enteric nervous system)
Muscularis Externa
Inner Circular Muscle Layer - constrict lumen
Outer Longitudinal Muscle Layer - shorten tract
- Myenteric Plexus (located between the 2 muscle layers)
Serosa
outer covering of the entire GI Tract, comprised of secretory epithelium & connective tissue layers
- lubricating/protecting fluid
Secretion
secretes gastric juice/saliva into the lumen
Digestion
chemical (enzymes) & mechanical (chewing) breakdown
Absorption
moving from lumen into ECF/blood (glucose/AA’s)
Motility
movement of material through the GI Tract as a result of muscle contraction
Peristaltic Contractions
- propel contents forward
- circular muscles contract behind bolus to push it forward
Segmental Contractions
- mixing contents to break up food and increase exposure to enzymes
- segments of intestine alternately contract & relax
Enteric Nervous System Function
- self sufficient nervous system containing a complete reflex circuit
- regulates motility and GI tract secretions
Short Reflexes
integrated in the enteric nervous system (entirely in gut wall)
- sensory receptors send info to ENS through interneurons
Long Reflexes
integrated within the CNS
- signals may originate inside the GI tract or from higher centers (brain)
- feedforward & emotional reflexes
GI Peptides
can be hormones, paracrines, neurotransmitters
- alter GI secretions/motility/eating behaviors
