GI 1 Flashcards
Mouth to anus
Lumen Contents considered outside body
30 feet in length
Alimentary Canal (GI Tract)
Not part of GI tract Produce substances secreted into tract –Salivary glands –Exocrine pancreas –Liver and Gall Bladder
Accessory organs
Function of GI: Breakdown ingested molecules into building blocks Two Types A. Mechanical B. Chemical
Digestion
Function of GI:
Digestive enzymes
Acid/Base
Bile
Secretion
Function of GI:
Passive and Active transport processes
Moves substances from lumen of gut to blood
Absorption
Function of GI:
Mixing
Mechanical Digestion
Move material through tract
Motility
Function of GI:
Removal of Metabolic waste
Very little true waste in Feces (Bile pigments)
Excretion
Function of GI:
Gut Associated Lymphoid Tissue
Defense
What are the 4 layers of structure of GI tract wall from outermost to innermost?
Mucosa
Submucosa
Muscularis externa
Serosa
Simple Columnar Epithelium
Lamina Propria
Muscularis Mucosa
-Movement of Villi
Mucosa
CT Layer
Blood and lymph vessels
Submucosal Plexus
-Network of neurons-Projections to luminal surface cells, muscularis mucosa, and to Myenteric plexus
Submucosa
-Network of neurons-Projections to luminal surface cells, muscularis mucosa, and to Myenteric plexus
Submucosal Plexus
Circular Muscle-Contraction narrows lumen
Longitudinal muscle-Contraction shortens tube
Myenteric Plexus
-Network of neurons-Input from Autonomic NS-
Projections to Submucosal Plexus, Circular, and
Longitudinal muscle
Muscularis Externa
- Network of neurons
- Input from Autonomic NS
- Projections to Submucosal Plexus, Circular, and Longitudinal muscle
Myenteric Plexus
CT covering
Support GI tract in abdominal cavity
Serosa
What 2 things make up the enteric NS?
Submucosal and Myenteric Plexus
\_\_\_\_\_\_ layer: Simple Columnar (microvilli) Goblet Cells Enteroendocrine cells (base of villi) Stem cells
Epithelial
Tremendous surface area available for absorption of materials from lumen via what 3 things?
- Circular Folds
- Villi
- Microvilli (Brush Border)
Circular Folds, Villi, and Microvilli (Brush Border)Increases SA ____ times over flat surface
600x
The following are Inside the ______:
Lacteals (lymph vessels)
Capillary network
Villus
Control Systems regulate conditions in ____ of tract
lumen
Control mechanisms are governed by ______ and ______ of luminal contents
volume and composition
ECL cells in the GI system secrete ______
histamine
D cells in the GI system secrete ______
Somatostatin
_____ innervation:
Responds to stretch, inflammation, nutrients, endocrine factors.
Synapses in enteric nervous system, prevertebral ganglia, spinal cord, brainstem.
Vagal nerves mainly afferent to brainstem.
Afferent (sensory)
_____ innervation– CN XII (tongue), V (chewing), IX, X (swallowing); Pudendal n. – ext. anal sphincter
Somatic
_____innervation post-ganglionicfibers (NEpi) to enteric nervous system, vasculature, ducts, parenchyma; usually inhibitory.
Sympathetic –
_____ innervation: ENS functions as post-ganglionic fibers, actions are stimulatory or inhibitory, depending on final neurotransmitter receptor.
Parasympathetic (vagus, pelvic)
____ is the neurotransmitter that is released from symp postganglionic neurons
NE
____ is the neurotransmitter that is released from parasymp preganglionic neurons
ACh
Linear chain of neurons that extend the entire length of GI Tract
Control muscle of muscularis externa
When stimulated
1.Increase tone of gut wall
2.Increase intensity of rhythmic contractions
3.Slight increase in rate of rhythmic contractions
4.Increase conduction velocity of electrical waves along gut wall
5.Inhibition of sphincter contraction
Enteric nervous system (ENS)
\_\_\_\_\_\_\_: Controls function of each minute segment of tract Local control of -Intestinal secretions -Absorption -Contraction of mucosal muscle
Enteric Nervous System (ENS)
What are the 3 receptors that respond to GI lumen stimulus?
Chemoreceptors, osmoreceptors, and mechanoreceptors
Are there long or short feedback loops in GI?
Both
____ cells are scattered in gut mucosa
Endocrine cells
Specialized cells: one cell – one hormone (mostly).
Specific cell types localized to regions of gut.
Cells “taste” luminal contents.
Endocrine regulation of digestive function
Cells similar to endocrine.
Released into interstitial fluid, diffuses to target (may “overflow” into the circulation).
Two established gut paracrine factors: histamine (ECL cell), somatostatin (D cell).
Paracrine factors
____ is mainly released by gastrin
Histamine
_____ is mainly released by luminal H+
Somatostatin
Patterns of \_\_\_\_\_\_ include: Chewing Swallowing Esophageal transport Gastric storage, trituration, emptying Vomiting Gallbladder storage, emptying Small intestinal mixing & transport Colonic storage, defecation
Motility
_____ muscle of the GI tract:
-mouth, oropharynx, upper esophageal sphincter, upper 1/3 of esophagus, external anal sphincter.
Skeletal (voluntary, striated) –
_____ muscle of the GI tract:
- lower 2/3 of esophagus, stomach, small intestine, large intestine, gallbladder, biliary and pancreatic ducts.
Smooth (involuntary)