Lecture 1 - GI Intro Flashcards
List the 17 parts of the digestive tract and the sphincters in between.
- Mouth
- Upper esophageal sphincter
- Esophagus
- Lower esophageal sphincter
- Stomach
- Pyloric sphincter
- Duodenum
- Jejunum
- Ileum
- Ileocecal sphincter
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
- Rectum
- Anus
- Internal and external anal sphincters
Where does the food become chyme?
In the stomach when it mixes with gastric secretions
3 parts of the small intestine?
- Duodenum
- Jejunum
- Ileum
Length of duodenum? Function?
Very short (1 foot) and serves as the junction between stomach and rest of GIT where pancreas, gallbladder, and liver secrete contents to insure the chyme is not too acidic after coming out of the stomach
Where does the bulk of the reabsorption happen in the GIT?
Mid-jejunum
How long is the jejunum?
10 feet
How long is the ileum?
12-13 feet
Only portion of GIT with villi? Purpose?
Small intestine
Purpose = increase surface area for absorption
How many cells between lumen of small intestine and absorption area (blood or lymph)? What are these called?
1 cell
Enterocytes
Which portions of the GIT do not have smooth muscle?
- Mouth
- Upper esophagus
- External anal sphincter
How many days do enterocytes last?
Less than a week
Describe the 2 layers of smooth muscle in the GIT? What are they called together?
- Longitudinal muscle
- Circular muscle
=> muscularis external
What is the myenteric plexus? Where is it?
Nerve net between the longitudinal and circular smooth muscle layers of the GIT stimulating their contraction
What is the submucosal plexus? Where is it?
Nerve net between the submucosa and the circular smooth muscle layer of the GIT stimulating glands to secrete
What is the enteric NS?
- Submucosal plexus
2. Myenteric plexus
What controls the GIT?
- ANS (para and sympa)
- Hormones
- Enteric NS
- CNS
- Lumenal chemo, mechano, and osmoreceptors
Can the enteric NS work without any ANS input?
Yes, because it has chemoreceptors, osmoreceptors, and mechanoreceptors to respond to the luminal environment and regulate the enteric NS without ANS input, BUT not as efficient
How can the GIT act independently of other systems?
Because of the enteric NS
Type of muscle in upper esophagus?
Skeletal muscle
Circulation of GIT? Describe it. What is this called?
Splanchnic circulation: blood flows from the intestines through the portal vein to the liver = first pass effect
8 functions of the GIT?
- Digestion
- Endocrine
- Elimination
- Protection
- Motility
- Absorption
- Secretion
- Storage