Lecture 7 - Anatomy of GI Flashcards
3 saliva glands
parotoid, submandibular and sublingual
Where is water, amylase filled saliva secreted from?
parotoid and submandibular saliva glands
Where is thick saliva and mucus secreted from in mouth?
Sublingual saliva gland
How food travels down GI tract
mouth, then to pharynx and down oesophagus into stomach, then from stomach into s. intestine. Food travels on to large intestine and then rectum and excreted.
Accessory Organs
Liver, gallbladder and pancreas
What’s the gut?
GI tract as a whole
Well fed/absorptive state
glucose levels increase, resulting in storage of fuels and protein synthesis and glycogen synthesis. INSULIN secreted from pancreas to enhance glucose uptake and metabolism in cells, reducing blood glucose
Glucose levels in Post-absorptive state
decrease in glucose causes an increase in glucagon (glycogen is broken down) and gluconeogenesis (production of glucose from e.g amino acids). Body tries to save glucose using fats (lipolysis) and ketones are produces as a source of energy during prolonged fasting
Hunger
decrease in glucose, fat, protein and an INCREASE in GHRELIN affects appetite centre in LATERAL Hypothalamus and makes us feel hungry
Satiety Signals
increase in glucose, fat, protein and leptin targets satiety centre in MEDIAL hypothalamus telling us to stop eating.
What effects gastric emptying?
meal size (more food=larger digestive phase), calories control gastric emptying. FAT DELAYS GASTRIC EMPTYING. It also lowers intragastric pressure. Feel fuller for longer after high fat meal. It prolongs elevation of pH in stomach.
Structure of GI (inside out)
lumen, mucosa (villi if small intestine and always epithelium) , submucosa (contains glands and SUBMUCOUS PLEXUS), circular muscle, MYENTERIC PLEXUS, longitudinal muscle.
Other name for myenteric plexus
Auerbach’s plexus
Other name for Meissner’s plexus
Submucosal plexus
Parts of CNS
brain and spinal cord
What does PNS do?
connect CNS to limbs and organs, ANS is a division of PNS
What does the autonomic nervous system do?
influences the function of organs
What is the enteric nervous system?
Myenteric plexus and submucosal plexus, the intrinsic nervous system of GI Tract
how are CNS and ENS connected
via vagus nerve, 10th cranial nerve that runs from brain stem down to abdomen.
Vagus nerve
primary route gut bacteria use to transmit info to brain
Afferent neurons
otherwise known as sensory receptor neurons, carry nerve impulses away from receptors or sense organs towards the central nervous system
Efferent nerves
otherwise known as motor or effector neurons, carry nerve impulses away from the central nervous system to effectors such as muscles or glands
Myenteric Plexus
largely motor in function, influencing muscle activity.
Submucosal plexus
largely sensory, receiving signals from epithelium and stretch receptors influencing secretory activity
How are myenteric and submucosal plexuses regulated?
via ANS (sympathetic and parasympathetic) since fibres from both can synapse with neurons in ENS. Allows CNS to influence GI activity.
Segmentation
facilitates mixing of food, circular muscle
Peristalsis
propulsion of food along tract, longitudinal muscle
Gut transit time
12 to 24hrs
Drugs that can cause constipation
Antacids, anticholinergics (reduce muscle spasms) and Antihypertensives (reduce blood pressure)
loperamide
targets opioid receptors (suppress motility through action on myenteric plexus - decreased peristalsis, increased tone of anal sphincter (Ca2+ channel blocker
Tegaserod
target serotonin receptors in ENS, motility stimulants
Antibiotics
can have negative effects on gut microbiome and can result in antibiotic-resistant organisms, which can lead to antibiotic-associated bacteria
inhibits gastric secretions
-fat in duodenum, secretin, decreased para. input and somatostatin
