Gastrointestinal System
College: First year, College: Second year
The four layers of the GI Tract (from inside to outside)
Mucosa, submucosa, muscularis, and serosa
Characteristics of the mucosa?
Contains MALT(mucosa-associated lymph tissue), blood vessels, and lymph. Also contains the muscularis mucosae
What is the muscularis mucosae?
A thin layer that throws it in folds to increase the surface area
Characteristics of the submucosa?
What plexus does it contain?
Connective tissue that binds mucosa to muscularis.
Contains the Plexus of Meissner
What is the Plexus of Meissner?
Also known as the submucosal plexus; contains neurons of the enteric nervous system (sensory, motor, and ANS)
Characteristics of the muscularis?
What plexus does it contain?
Skeletal muscle for swallowing and defecation, smooth muscle for peristalsis, contains the myenteric plexus
What is the Plexus of Auerbach?
Also known as the myenteric plexus. Found between longitudinal and circular muscles (think M for myenteric and M for muscles!). Controls GI motility
Characteristics of the serosa?
Tough, most fibrous, superficial covering, the mesentary suspends the GI tract in the abdomen
Difference between mucosa and serosa?
Mucosa is exposed to the external environment, while serosa is exclusively internal.
What nerve is involved with neural innervation of the gastrointestinal nerve? (hint: it's on a vacation from the brain)
CN(10):Vagus nerve. (think all girls who are a perfect 10 take a vacation down to "vagus")
What is the peritoneum?
Largest serous membrane in the body,it is a thick, protective, tarp-like covering ENTIRE abdominopelvic cavity
Major parts of the peritoneum? (must-know)
Greater omentum: "beer belly" appearance
Falciform ligament: attaches liver to back wall
The three names food is called in the GI system and where they are called these names?
Bolus: mouth to stomach
Chyme: stomach to small intestine
Fecal: small intestine to exit
What are the three types of salivary glands?
What is saliva controlled by?
Parotid (contains amylase), sublingual, and submandibular
Controlled by the ANS
The "666" of teeth:
6 months: baby teeth come in
6 years: start getting permanent teeth
16 years: start getting sensation of wisdom teeth
Another word for swallowing is?
Deglutition
Gastric juice is composed of?
HCl acid and enzymes
Bile formation and storage?
Liver MAKES bile, gall bladder STORES bile
Another word for vomiting?
Where is the vomiting center located?
Emesis
Medulla Oblongata
THREE major digestive hormones:
1. Gastrin (chief cells): gastric secretion, releases/contricts esophageal, pyloric, and ileocecal sphincters
2. Secretic: secretion of pancreatic juices and bile from liver, inhibits gastric juice secretion
3. Cholecystokinin: ejection of bile, pancreatic juice secretion, relaxes SPHINCTER OF ODDI, induces feeling of fullness
Liver:
Heaviest gland in the body (3 lbs), L is smaller than R lobe, falciform ligament, round ligament
Liver bile emulsifies lipids
Liver cells?
Hepatocytes: functional cells
Lobule: functional unit of liver
Two main blood sources in liver:
Hepatic artery: oxygenated blood from aorta
Hepatic portal vein: blood from GI tract w/ nutrients
Hepatic acinus:
(know how the zones relate to fatty liver disease)
oval and has branches of PORTAL TRIAD and is divided into 3 ZONES
Zone #1 is healthiest with best O2 blood supply, Zone #3 is closest to portal vein
Fatty liver disease pushes fat from Zones 1 and 2 all the way to clog zone #3 (this is how doctors can stage fatty liver disease)
SPHINCTER OF ODDI
(has two other names)
closes the exit to the duodenum
other names: Hepatopancreatic ampulla, Duct of Santorini
Liver functions:
Metabolism, breaks down glycogen, activates vitamin D
What is so special about the pancreas?
It has both exocrine and endocrine functions
Pancreas cells and their percentages?
Acini - clusters of cells, exocrine, 99%
Islets of Langerhans - endocrine, 1%
Peristalsis versus Segmentation?
Peristalsis (a) moves food along, segmentation (b) is small contractions that sorts the chyme into "segments"
Plicae circulares versus Villi?
Plicae are the FOLDS that enhance surface area and helps chyme spiral.
Villi are FINGER-LIKE PROJECTIONS that increase surface area
What is a lacteal?
Lymphatic vessel within the villi
Parts of small intestine, shortest to longest?
Duodenum, jejunum, and ileum
What are the lymph nodes that are scattered throughout the small intestine called?
Peyer's patches
SMALL INTESTINE CELLS:
Goblet cells (mucous), Paneth cells (antibacterial, capable of phagocytosis), and Brunner's glands (mucous located in duodenum)
THREE types of enteroendocrine cells
S cells --> secretin (s for s!)
C cells --> CCK cholecystokinin (c for c!)
K cells --> glucose-dependant insulinotropic {-tropic means it's controlled by pituitary gland} think of a hard "K" in gluKose!
Large intestine:
characterized by its "globular chunk" appearance, no villi, contains haustra (which are tonic contractions), has tenae coli (longitudinal muscles), the R side is lower than L side, "defecation reflex" is self explanatory :p