ILA 5 -GORD Flashcards
Describe the upper GI tract
The pharynx, oesophagus, stomach and duodenum
Describe the anatomy of the pharynx
- sections
- muscles - what innervates?
- The pharynx is a muscular tube common to the GI and respiratory tract
- Naso, oro and laryngopharynx
- Longitudinal and circular muscles
- muscles are innervated by the vagus nerve (expect the stylopharyngeus CNIX)
Describe the anatomy of the oesphagus
- length
- location
- vasculature
- endothelium
- diaphragm entery
- sphincters
- Fibromuscular tube aprox 25cm
- Transports food from pharynx to stomach
- C6 to T11 at cardiac orifice of the stomach T11
- Thoracic (thoracic aorta and inferior thyroid artery) and abdominal parts (L gastric artery and L inferior phrenic artery)
- Stratified squamous
- Enters diaphragm at oesophageal hiatus T10
Has an internal circular muscular layer and external longitudinal layer (in superior 1/3 it is voluntary striated, next 1/3 is mixed and final 1/3 is smooth muscle)
-Food is transport via peristalsis (hardening of the layers can cause dysphagia)
Describe the anatomy of the stomach
- sections
- sphincters
- attachment/ligament
- nerve supply
- vasculature
- name of folds
Sections = Cardia, fundus, body, antrum, pylorus
- The cardiac notch in the acute angle between the L border of the abdominal oesophagus and the fundus of the stomach
- attached by hepatogastric ligament = attaches stomach and duodenum to the liver
- celiac ganglia and vagus nerve
- L and R gastric anastomose, and L and R gastro-ommentum anastomose
- contains RUGAE - mucus, allow stretch
Describe the anatomy of the duodenum
- name sections
- where is cavity
- vasculature
- nervous spply
- First part of duodenum, followed by jejunum and ileum
- Superior, descending, inferior, ascending
- Largely retroperitoneal
- R gastric artery and R gastro-epiploic artery
- Parasym = hepatic and celiac branches of vagi
- Symp = branches pf celiac plexus
Describe the sensory innervation of the pharynx
Oropharynx - maxillary CN V2
Nasopharynx - glossopharyngeal nerve CN IX
Laryngopahrynx - vagus nerve CN X
Describe the vasculature of the pharynx
- Branches of the external carotid, ascending pharyngeal, lingual, facial and maxillary
- pharyngeal venous plexus, drains into internal jugular
What passes through the diaphragm? At what level?
IVC - T8
OESOPHAGUS - T10
AORTA - T12
(I ate, 10 omelettes, at 12)
What does the oesphagus lie close to anatomically?
- Anteriorly - trachea, left recurrent laryngeal nerve, pericardium, left vagus nerve (further down)
- Posteriorly - descending aorta, right vagus nerve (further down)
- R - terminal part of azygous vein
- L - aortic arch
Describe the oesophageal sphincters
Upper - anatomical, striated muscle, produced by cricopharyngeus muscle, normally constricted to prevent entrance of air into oesophagus
Lower - physiological sphincter, located at gastro-esophageal junction (T11), marked by change from oesophageal to gastric mucosa
Describe the vasculature of the oesphagus
Thoracic part = thoracic artery, inferior thyroid artery
azygous vein or inferior thyroid vein
Abdominal part = left gastric and L inferior phrenic artery
mixed drainage either - portal circulation via L gastric vein or systemic circulation via azygous vein
two routes form a porto-systemic anastomosis
What are the stages of gastric acid secretion?
- Cephalic stage, sight/smell/taste and chewing activates the parasympathetic NS (vagus nerve carries)
a) Acetylcholine is released = stimulates HCl release, and gastrin release (G cells)
b) G cells release gastrin = this stimulates enteroendocrine cells to release histamine, this acts on parietal cells to release HCl - Gastric phase - turning on
a) Food stretches walls of the stomach, mechanoreceptors detect this and acid secretion is stimulates
b) Peptides and amino acids in the food stimulate gastrin release from G cells
c) Buffers in the stomach mop up excess H+ so that this stage can continue longer - Gastric phase - turning off
a) As H+ is released Ph drops - this inhibits gastrin which indirectly inhibits enteroendocrine cells and histamine (and therefore parietal cells and HCl release)
b) The low pH stimulates somatostatin release (somatostatin -releasing cell of gastric epithelium)
c) Somatostatin inhibits acid release from parietal cells, and also acts on G cells and enteroendocrine cells - Intestinal phase
a) The presence of amino acids, fatty acids and hypertonic substances in the stomach and duodenual distension and low pH
b) less acetylcoline released - less H+ released
c) stimulates the release of CCK - this inhibits gastric acid release and stimulates the gall bladder to release bile salts :)
d) stimulates the release secretin - inhibits gastrin and gastric emptying, also promotes somatostatin release
What defences does the stomach have against acid?
a) alkaline mucus - surface mucosa cells secrete slightly alkaline mucus
b) tight junctions - this restricts movement of H+ into underlying tissues
c) high replacement of cells - new cells arise from gastric pits
Where are secreting cells of the stomach found?
- Pyloric glands contain G cells that secrete gastrin - these are found in the ANTRUM
- Fundus contains parietal cells - HCl and intrinsic factor
- Cardiac glands contain cardiac glands - secrete protection mucous
enterochromaffin-like cells/enteroendocrine - histamine
Describe the function and type of epithelium in the GI tract
- Oral cavity - protective, stratified squamous - partially keratinised on gums and hard palate SSNKE - SSKE, contains sebaceous glands (fordyce’s spots)
Tongue = SSNKE on ventral/under side, SSKE on dorsal/upper side due to constant abrasion, lymph nodes mostly posterior 1/3 - Oesophagus - protective, stratfied squamous - SSNKE then simple columnar like stomach after passing diaphragm
- Stomach - simple-columnar + mucus, acid, enzyme, RUGAE
- Small intestine (duodenum, jejunum, illeum, caceum)
- absorption of nutrients, simple columnar +absorption cells, gobelet, evaginating viliv, invaginating crypts containing stem cells - Appendix - absorption - simple columnar, more lymphatics
- Colon - absorption - simple columnar - ascending, transverse, descending
Rectum = simple columnar
- Anal canal - protective - SSNKE, then transitions to SSKE
