4.1 Upper GIT Flashcards
What is the GIT?
Gastrointestinal Tract (GIT) is a series of tubes from the mouth to the anal cavity
Functions of the GIT?
Ingestion & absorption of nutrients and excretion of waste
Blood supply of the digestive system?
Celiac artery, superior, and inferior mesenteric arteries and tributaries
- Celiac artery
- artery of FOREGUT
- supplies GIT from lower β of esophagus -> middle of 2nd part of duodenum - Superior mesenteric a.
- a. of FOREGUT
- supplies GIT from middle of 2nd part of duodenum -> distal β of transverse colon - Inferior mesenteric a.
- a. of HINDGUT
- supplies large intestines from distal β of transverse colon -> halfway down the anal canal
Layers of the GIT
Mucosa
- epithelium
- lamina propria
- muscularis mucosa
Submucosa
-Submucosal/Meissnerβs Plexus
Muscularis Propria
-Myenteric/Auerbachβs Plexus
-w/ circular and longitudinal ms
>When the circular ms is stimulated, it decreases the diameter or the GIT lumen
>When the longitudinal ms contracts, it shortens the length of the digestive system
Serosa or adventitia
Neural Control of the GIT
- Intrinsic control -ENS
- Extrinsic control - ANS
>Parasympathetic - excitatory (both motor and sensory); mainly stimulates ACh
>Sympathetic - inhibitory of the GIT activity
2nd brain in the GIT and different types of neurons found in its ganglion?
Enteric Nervous System
βDiff types of neurons found in enteric ganglia:
>Afferent neurons - sensory
>Interneurons - sensory neuron impulses go here for processing on information. They have a program library (there sets of activities suited for the inputs coming from the sensory neurons).
>Motor neurons - response of diff cells
Type of smooth ms in GIT?
Unitary
Micropits in the GIT smooth ms that increases SA
Caveolae (for absorption)
2 types of channels in the GIT smooth ms
- Electromechanical channels
- works as transducers
- composed of slow leaking Ca2+ channel, Na voltage gated channels, and ligand gated channels - Pharmacomechanical channels
- employs 2nd messengers and it will produce muscular contractility without any change in electrical potential
2 types of waves in the GIT smooth muscle
- Slow waves
2. Spikes
Smooth muscle contraction review
Ca2+ from ECF/environment & SR -> bind and activate Calmodulin -> activate MLCK which transfer phosphate to myosin heads = phosphorylation -> cross-bridge cycling -> contraction
What is xerostomia
Due to a decrease in salivary flow or decrease in production of saliva which may be 2ndary to the medication you have taken in/dehydration 2ndary to whatever (severe gastroenteritis, etc, and old age; Older = decrease in production of saliva)
3 phases of swallowing
- Oral Phase
-contraction of tongue and striated muscles of mastication
>Bolus is positioned on the center of the tongue - Pharyngeal Phase
-Closure of oropharynx
-Closure of larynx
-Elevation of hyoid
>Bolus transmitted to pharynx - Esophageal Phase
>Bolus is transported to the stomach
Intricacies in the GIT histology
Oral and pharyngeal phase are both voluntary (you can still remove food)
Innervation
Pharyngeal wall and upper β
of the esophagus
>CN IX and X
Lower β
of the esophagus
>By CN X