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 ⅓ of esophagus -> middle of 2nd part of duodenum - Superior mesenteric a.
- a. of FOREGUT
- supplies GIT from middle of 2nd part of duodenum -> distal ⅓ of transverse colon - Inferior mesenteric a.
- a. of HINDGUT
- supplies large intestines from distal ⅓ of transverse colon -> halfway down the anal canal
Layers of the GIT
Mucosa
- epithelium
- lamina propria
- muscularis mucosa
Submucosa
-Submucosal/Meissner’s Plexus
Muscularis Propria
-Myenteric/Auerbach’s 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
–Diff 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 ⅔ of the esophagus
>CN IX and X
Lower ⅔ of the esophagus
>By CN X
What happens in a person’s swallowing if there is paralysis in the brain stem?
Eradicated!!!
Primary vs secondary peristaltic movements of esophageal muscles
Primary - normal peristalsis
Secondary - if you’re not able to clear esophagus of the food you have taken in
What is Barrett’s esophagus?
Sphincters must remain closed; otherwise, if open/di tama pagkakasara, there will be a reflux of food from stomach back to your esophagus. But esophagus does not have the capability to withstand the acidic contents of stomach so there’ll be erosion of that part of the esophagus because of reflux of food particles called Barrett’s esophagus (a precancerous lesion)
Both are tonically contracted.
Vomiting
Forceful expulsion of the stomach contents usually proximal to the small intestines which maybe not GI in origin
Reverse peristalsis
Last of the 3 events
3 events before you vomit
- Nausea
- increased tone and reverse peristalsis of the small intestines
- decreased gastric motility - Retching
- spasmodic respiratory movements with a closed glottis and antrum contraction
- fundus and cardia of stomach relax - Emesis
- gastric contents are propelled out of the mouth
Chemoreceptor trigger zone
Visceral afferents are received from the GIT, outside the GIT, extramedullary centers in the brain (vomiting center).
Food in the stomach
- Cardia
When food enters here, food goes to the fundus
Muscles relax (receptive relaxation) ready to receive food you have taken in
- Fundus
- Can distend due to the plasticity of smooth muscles
- Then, there is peristaltic movement in the body of the stomach
- Note: Certain feature of the stomach not found in other parts of the GIT: Presence of extra muscles (Circular, longitudinal, oblique, etc to strengthen contractions also kasi dami kinakain) - Body
- Peristaltic movement until it reaches pylorum - Antrum
- Peristalsis + segmentations (mixing movement) - Pyloric canal
- Pylorus
- Duodenum
- Has retropulsive movement
3 parts and functions of the stomach
- Pressure pump - in the fundic area
- Propulsive pump - has peristaltic movement and some segmentation
- Grinder - in the antrum
Stomach secretions
- HCl from parietal cells
2. Bicarbonate which will go to your bloodstream in echange for Cl-
What is an alkaline tide?
High amt of bicarbonate in the blood
Stimulated by the increase in activity of parietal cell through the presence of Ach, Histamine, Gastrin
