Flashcards
Intro to the GI System
Cards in this deck (32)
- 1Describe the passage of food through the GI systemMouth --> Oesophagus --> Stomach --> Duodenum --> Intestines --> Rectum --> Anus
- 2What are the functions of the GI system?Absorption
• Optimised by secretion
Digestion
Storage
Excretion - 3Define: AbsorptionThe process of transporting dietary contents across the GI barrier into the body
- 4How are the nutrients prepared for absorption?Mechanical breakdown - involving smooth & skeletal muscle contraction
Chemical breakdown - Digestion - 5Define: Secretion in the GI systemThe act of transporting molecules or fluid from the body to the GI lumen
• facilitates digestion by delivering enzymes + water & protects the endothelial surface by secreting HCO3- + mucus - 6Name the layers of the GI lime from inner to outer-mostMucosa -- Submucosa -- Muscularis Externa (Circular - Longitudinal muscle) -- Serosa
- 7Composition of the mucosal layerEpithelium -
• cells shed every 2-3 days
• extend of villi & crypts vary along the tube
• apical side = GI lumen, basolateral side = interstitium & vasculature
Lamina propria -
• loose connective tissue - elastin & collagen fibres
• contains sensory nevre, blood + lymph vessels & secretory glands
Muscularis mucosa -
• smooth muscle layer w/ folds & ridges - 8Composition of the submucosal layerThick layer similar to lamina propria
• incorporates blood vessels & nerve bundles that form the submucosal or meissner plexus (an integral part of the Enteric NS) - 9Composition of the muscularis externaCircular muscle + Myenteric plexus (Aurebach plexus) + Longitudinal muscle
• ENS coordinates contraction
• Sphincters regulate flow between compartments - 10Composition of serosaOutermost layer of connective tissue + a layer of squamous epithelial cells
NOTE --> some sections of the GI system don't have a serosa layer but instead connect directly to adventitia - 11What 3 divisions of the ANS regulate GI function?Parasympathetic NS - facilitates secretion & motility
Sympathetic NS - decreases secretion & motility
Enteric NS - operate autonomously, via intrinsic regulation & sensory reflexes - 12What nerves supply Parasympathetic innervation to the GI tract?Vagus nerve & Pelvic-splanichnic nerves
• Have sensory & motor components which respond to; stretch, pressure, temperature + osmolarity - 13Where do the nerves of the sympathetic NS originate & where do they synapse?Originate in the thoracic + lumbar regions & synapse in:
• celiac ganglia
• superior or inferior mesenteric ganglia - 14Into what are ENS nerves organised?Myenteric & Submucosal plexuses
- 15Role of the myenteric plexusRegulates intestinal smooth muscle & participates in tonic + rhythmic contractions
- 16Role of the submucosal plexusRegulates intestinal secretions & local absorptive environment
- 17How are GI reflex actions regulated?Neural circuits involving mechanoreceptor or chemoreceptor stimulation in the mucosa
- 18Name 7 GI neurotransmitters & neuromoderators• ACh - PSNS
• Vasoactive Intestinal Peptide -PSNS
• Norepinephrine - SNS
• Neuropeptide Y - SNS
• Gastric-releasing peptide - PSNS
• Substance P - PSNS
• Enkephalins - ENS - 19GI hormones• Cholecystokinin - I cells, ↑ pancreatic & biliary secretions
• Gastrin - G cells, ↑H+ secretions
• Glucose-dependant insulinotropic peptide - K cells, ↑ insulin release & ↑ H+ release
• Motilin - M cells, ↑ motility
• Secretin - S cells, ↑ water + HCO3- secretion & ↓ H+ - 20GI Paracrines• Histamine - released from enterochromaffin-like cells + mass cells , ↑H+ production
• Prostaglandins - ↓ H+ & maintain GI barrier properties
• Somatostatin - D cells, ↓GI secretions - 21What are the 3 Digestive Phases1. Cephalic phase
2. Gastric phase
3. Intestintal phase - 22Describe the Cephalic phaseTriggered by the thought or association of food
• primarily neural & causes the secretion of ACh + VIP by salivary glands, stomach, pancreas + intestines - 23Describe the Gastric phaseTrigged when food & oral secretions reach the stomach
• elicits neural, hormonal & paracrine GI response - 24Describe the Intestinal phaseTriggered when the stomach content reach the duodenum
• primarily initiates a hormonal, but also paracrine & neural, response - 25Function of: The mouthMastication - mechanical & chemical breakdown
• teeth - cut, tear & pierce / grind & crush
• jaw muscles - provide force & motion
• tongue - repositions food - 26Function of: Salivary glandsRelease watery fluid which lubricates the mouth & begins food digestion
NOTE --> the fluid is hypotonic to plasma & its commotion is determined by ductal modifications of primary secretion - 27What are the 2 functions of the oesophagus?Swallowing -
• initiated voluntarily
• PS process - afferent feedback to swallowing centres & efferent response tough other nuclei
Peristalsis -
• a series of co-ordinated muscle contractions & relaxations
• commences after upper oesophageal sphincter - 28Functions of: The Stomach• Accepts & stores food
• Mixes food w/ secretions
• Digests food
• Delivers food to the small intestine - 29Where do secretions come from?Pit, gastric invaginations, containing multiple cells types
- 30What are the 3 sections of the small intestine?Duodenum
Jejunum
Ileum - 31Name the regions of the large intestine from where it joins the small intestine to the anusCaecum
Ascending - Transverse - Descending - Sigmoid Colon
Rectum
Anus - 32What are the functions of the intestines?Small - absorption of macronutrients, vitamins & minerals
Large - water & ion absorption
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- MD2001 Flashcards on Intro to the GI System, created by Lareyna Mcmenemy on 01/08/2018.
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- Lareyna Mcmenemy
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