GI Flashcards
What are the overall processes involved in GI function?
Initial physical disruption –> Ingestion and transport to storage –> Initial chemic disruption and creation of suspension (chyme) –> Disinfection –> Controlled release of Chyme –> Dilution and neutralisation –> Completion of chemical breakdown –> Absorption of nutrients and electrolytes –> Final absorption of water and electrolytes –> Producing faeces for controlled excretion.
What is the purpose and reasoning for the functions of the GI tract?
Metabolic processes need a specific, range of small molecules. Food has a wide range of mostly large molecules locked into complex structures. It may also be contaminated with pathogens.
Digestion makes food into a sterile, neutral, and isotonic solution of small sugars, amino acids and small peptides, small particles of lipids and other small molecules. This is now ready for absorption and excretion.
What are the broad functions of the mouth and oesophagus?
- Mastication
- Saliva
o Protects mouth
• Wets / Bacteriostatic / Alkaline / High Ca2+
o Lubricates food for mastication and swallowing
• Wet / Mucus
o Starts digestion
• Sugars - amylase - Swallowing
o Formation of bolus
o Rapid oesophageal transport
What are the broad functions of the stomach?
o Storage
- Relaxes to accommodate food
o Initial disruption
- Contracts rhythmically to mix and disrupt
- Secretes acid and Proteolytic enzymes to break down tissues and disinfect
- Now known as Chyme
o Delivers Chyme slowly into the Duodenum
What are the broad functions of the duodenum?
o Dilution and neutralisation of Chyme
- Water drawn in from ECF. Stomach impermeable, Duodenum permeable.
- Alkali (bile) added from Liver and Pancreas
- Enzymes added from pancreas and intestine
What are the broad functions of the small intestine?
o Absorption of nutrients and electrolytes
- Fluid passes very slowly through the small intestine
- Large surface area
- Epithelial cells absorb molecules, some actively some passive
• Often coupled to Na+ absorption
- Pass into hepatic portal circulation (First pass…)
o Absorbs the majority of water (1.5L vs. 0.15L large intestine)
What are the broad functions of the large intestine?
o Final absorption of water (0.15)
o Very slow transit
o Faeces form and accumulate in the descending and sigmoid colon
What are the broad functions of the rectum ?
o Faeces propelled periodically into rectum
o Urge to defecate
o Controlled relaxation of sphincters and expulsion of faeces
What four histological layers does the alimentary canal consist of?
From the oral cavity to the anus the alimentary canal consists of four layers:
o Mucosa
• Epithelial lining and thin layer of smooth muscle
o Submucosa
• Fibroelastic tissue with vessels, nerves, leucocytes and fat cells
o Muscularis Externa
• Inner circular and outer longitudinal layer of smooth muscle with the myenteric plexus lying in between the layers.
o Serosa/Adventitia
• Thin outer covering of connective tissue
A variation in the cellular composition of these layers provides adaptations for specific functions whilst remaining a continuous hollow tube of variable diameter and shape
Describe the fluid balance of the Gut
Each day we ingest about 1kg of food and about a litre of liquids. The food is mixed with 1.5L of Saliva and about 2.5L of gastric secretions to form chyme. Chyme is very hypertonic (has a high osmotic strength) and is very acidic.
When chyme is slowly released from the stomach, around 9L of water (and alkali) moves into it from the ECF via osmosis.
The small intestine then absorbs about 12.5L of the fluid, and the large intestine absorbs about 1.35L.
What are some properties of the enteric system and how is it related to the Autonomic nervous system?
The enteric nervous system is a subdivision of the autonomic nervous system that directly controls the GI system. It is made up of two nerve plexuses in the wall of the gut that may act independently of the CNS (short reflex pathway). This activity may be modified by both branches of the ANS (long reflex pathway). Parasympathetic control however is the most significant. It coordinates both secretion and motility using a range of neurotransmitters, not just Ach as you may expect (parasympathetic).
How are hormones involved in the motility and secretion of the gut?
Endocrine cells in the walls of the gut release a dozen or more peptide hormones. These include both hormones with endocrine action and paracrine action. The hormones comprise two structurally related groups – the Gastrin group and the Secretin group. These hormones are released from one part of the gut to affect the secretions or the motility of other parts.
What is dysphagia?
Difficultly swallowing. May be caused by problems with the oesophagus, e.g. musculature, obstruction by tumour or neurological, e.g. a stroke. Tumours of the oesophagus, high up are Squamous Cell Carcinoma, lower down are Adenocarcinomas.
What is acid reflux?
Sphincter between the oesophagus and the stomach is weak, acid refluxes into the oesophagus and causes irritation and pain (heartburn).
What is Barrett’s oesophagus?
Metaplasia of the lower oesophageal squamous epithelium to gastric columnar. This is to protect against acid reflux.
What are oesophageal varices?
Portal venous system is overloaded due to cirrhosis, blood is diverted to the oesophagus through connecting vessels. This leads to the dilation of sub mucosal veins in the lower part of the oesophagus
What is a peptic ulcer?
Area of damage to the inner mucosa of the stomach or duodenum, usually due to irritation from gastric acid.
What is pancreatitis?
Inflamed pancreas, causes considerable pain. Characterised by the release of amylases into the blood stream.
What is jaundice?
Liver cannot excrete bilirubin, which accumulates in the blood. If build up of bilirubin is due to excess haemoglobin breakdown it is Pre-hepatic Jaundice. If build up of bilirubin is due to bile duct obstruction and back up of bile causing liver damage it is Post-hepatic or Obstructive Jaundice
What are gallstones?
Precipitation of bile acids and cholesterol in the bladder forms gall stones. Often asymptomatic, but may move within the gall bladder causing painful Biliary Colic, or move to obstruct biliary outflow. Tumours of the pancreas may also obstruct outflow
What is malabsorption?
Several conditions affect how well the intestines can absorb things
What is appendicitis?
Inflammation of the appendix, presents as a sharp pain in the side at the same level as T10, which then localises to the right lower quadrant.
What is peritonitis?
Inflammation of the peritoneum
What is IBS?
Inflammatory Bowel Syndrome – E.g. ulcerative colitis and Crohn’s disease
What is acute blockage of the small intestine?
Present with Pain (in their back), vomiting and bloating
What are haemorrhoids?
Vascular structures in the anal canal that aid with stool control. When they become swollen and inflamed they are painful, itchy and blood may be present in stool.
What is a prolapse?
Literally means ‘to fall out of place’. Prolapse is a condition where organs fall down or slip out of place. E.g. the rectum can prolapse.
What is a diverticula?
Pressure is too high in the colon, producing an abnormal ‘outpouching’ to form a hollow. The sigmoid colon is the area most prone as the blood supply causes an area of weakness (?)
What is Meckels’ diverticulum?
A pouch in the lower part of the small intestine, a vestigial remnant of the yolk sac. It can produce ectopic gastric mucosa that may then produce gastric acid, causing irritation.
What is colo rectal cancer?
The large intestine is a common site of malignancies, and colo-rectal cancer is a major cause of mortality.
What is the mouth and it’s purpose?
The mouth is the entrance to the GI tract. It serves to disrupt foodstuffs and mix them with saliva to form boluses to be swallowed.
What is the purpose of the teeth?
The teeth cut (incisors), crush (molars) and mix food with saliva.
What powerful muscles generate the force behind the teeth movement and what innervates these?
The powerful muscles of mastication, the Masseter, generate the force behind teeth. A branch of the trigeminal nerve innervates the Masseter.
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How many muscles make up the tongue? What is the purpose of the tongue?
The tongue is a collection of 8 muscles that work to manipulate food for mastication and form it into a bolus. It also aids in swallowing by pushing the bolus to the back of the mouth
What is the oropharynx? And some of its features? What is the relevance of the glottis
The oropharynx lies behind the oral cavity, and forms the portion of the pharynx below the nasopharynx but above the laryngopharynx.
It extends from the uvula, which is the end of the palate, to the level of the hyoid bone/ epiglottis
Because both food and air pass through the oropharynx, a flap of tissue called the epiglottis closes over the glottis to prevent aspiration.
What is the oesophagus?
The oesophagus is a muscular tube that passes food from the pharynx to the stomach. It is continuous with the lower part of the laryngopharynx.
What are the histological layers of the oesophagus?
The oesophagus has several layers, from inside to out:
o Mucosa composed of non-keratinized stratified squamous epithelium, lamina propria and a layer of smooth muscle (Muscularis Mucosa)
o Submucosa containing the mucous secreting glands
o Mucularis externa. Upper third of oesophagus is striated, skeletal muscle under conscious control for swallowing. The lower two thirds are smooth muscle under autonomic control (peristalsis).
How much saliva is produced every day?
1.5 litres of saliva is produced each day.
What are the functions of saliva?
It has several functions: 1. Lubricates and wets food 2. Starts the digestion of carbohydrates (Amylase) 3. Protects oral environment o Keeps mucosa moist o Washes teeth o Maintains alkaline environment • Neutralises acid produced by bacteria o High Ca2+ concentration
What is zerostomia?
Insufficient Saliva production. You are still able to eat provided food is moist, but teeth and mucosa degrade very quickly.
What are the main constituents of saliva?
o Water
• Hypotonic solution
o Electrolytes
• Na+, Cl-, usually at a lower concentration than plasma
• Ca2+, K+, I- (iodide) usually at a higher concentration than plasma
o Alkali
• HCO3- at a higher concentration than plasma
o Bacteriostats
o Mucus - (Mixture of mucopolysaccharides)
o Enzymes - Salivary amylase (can live without it, relatively minor)
Describe the 3 types of salivary glands and their functions
There are three paired salivary glands. They are all ducted, exocrine glands, but do not all excrete the same thing.
Exocrine glands are made up of blind-ended tubes (Acini), lined with acinar cells. The acini are connected via a system of ducts to a single outlet, lined by duct cells. Acinar cells and duct cells have different functions.
o Parotid Glands
• Watery secretion, rich in enzymes but little mucus
• Serous saliva
• 25% of volume secreted
o Sub-lingual glands
• Viscous secretion, no enzymes but lots of mucus
• Mucus saliva
• 5% of volume secreted
o Sub-maxillary glands
• All components of saliva (mixed serous and mucus)
• Mixture of serous and mucus acini leading to a common duct
• 70% of volume secreted
How is serous saliva secreted?
Saliva is a hypotonic solution, but there is no cellular mechanism to secrete water. Therefore more concentrated solution is secreted, and solute is then reabsorbed from it to leave the final hypotonic solution.
Acinar Cells secrete an isotonic fluid containing enzymes. Duct Cells then remove Na+ and Cl- and add HCO3-. The gaps between duct cells are tight, so water does not follow the resulting osmotic gradient and so saliva remains hypotonic.
At a low flow rate of saliva how hypotonic is saliva?
At a low flow rate, the duct cells have the opportunity to remove most Na+, so saliva is very hypotonic.
At a high flow rate of saliva, how hypotonic is saliva? How is pH affected?
The rate at which duct cells can modify saliva is limited, so at a high flow rate a smaller fraction is removed and the saliva becomes less hypotonic. However, the stimulus for secretion promotes HCO3- secretion, so saliva becomes more alkaline. (At a high flow rate)
How does acinar secretion occur (re: saliva)?
Cl- ions are actively secreted from Acinar cells into the lumen of the duct. Water and other ions (Na+) will then follow passively.
How does ductal modification occur (re: saliva)?
The action of the Na/K-ATPase Antiporter in the Basolateral membrane of duct cells lowers the [Na+] inside the cell. This means there is a concentration gradient, where [Na+] is high in the duct lumen and low in the duct cells. Na+ diffuses passively back into the Duct cells.
The action of the Na/K-ATPase Antiporter also increases the [K+] concentration in side the cell. The resulting concentration gradient drives the expulsion of Cl- from the duct cells into the ECF. Again, a concentration gradient is set up between the duct lumen and cells, with [Cl-] low inside and [Cl-] high outside. This gradient drives the expulsion of HCO3- into the duct lumen.
How is salivary secretion controlled?
Salivary secretion is mostly controlled by the autonomic nervous system.
Parasympathetic
Parasympathetic stimulation increases the production of primary secretion (Acinar cells) and increases the addition of HCO3- (Duct cells)
o Parotid Gland
• Glossopharyngeal Nerve (9th cranial nerve)
• Otic ganglion
o Submandibular and Sublingual Glands
• Facial Nerve (7th cranial nerve)
• Submandibular ganglion
o Muscarinic receptors
• Blocked by atropine like drugs
o Co-transmitters stimulate extra blood flow
Outflow is mediated by: o From centres in the medulla o Afferent information from: • Mouth and tongue o Taste receptors, especially acid • Nose • Conditioned reflexes o Pavlov’s dogs
Sympathetic
Sympathetic stimulation reduces the blood flow to the salivary glands, limiting salivary flow and producing the typical dry mouth of anxiety.
o Superior cervical ganglion
The rate of ductal recovery of Na+ is also increased by the release of aldosterone from the adrenal cortex. ( high ENaC, high Na/K/ATPase), making saliva even more hypotonic.
What are the three phases of swallowing?
Once food has been masticated and mixed with saliva to form a bolus, it must be swallowed. Swallowing is in three phases:
1. Voluntary Phase
- Pharyngeal Phase
- Oesophageal Phase
Describe the voluntary phase of swallowing
o Tongue moves the bolus back onto the pharynx
Describe the pharyngeal phase of swallowing
o Afferent information from pressure receptors in the palate and anterior pharynx reaches the swallowing centre in the brain stem.
o A set of movements is triggered
• Inhibition of breathing
• Raising of the larynx
• Closure of the glottis
• Opening of the upper oesophageal ‘sphincter’
Describe the oesophageal phase of swallowing
o The muscle in the upper third of the oesophagus is voluntary striated muscle under somatic control
o The muscle of the lower two thirds is smooth muscle under control of the parasympathetic nervous system.
o A wave of peristalsis sweeps down the oesophagus, propelling the bolus to the stomach in ~9 seconds.
o Coordinated by extrinsic nerves from the swallowing centre of the brain
o Lower oesophageal ‘sphincter’ opens
What is dysphagia?
Dysphagia – The symptom of difficulty in swallowing
What are some causes of dysphagia?
Dysphagia may result as a consequence of a primary oesophageal disorder, for example motility problems of the smooth muscle preventing peristalsis. The name for this condition is achalasia.
Dysphagia may also result as a secondary consequence of another issue, E.g. obstruction or compression of the oesophagus due to a tumour.
What is odynophagia?
Odynophagia – The symptom of pain whilst swallowing
What is oesophageal dysphagia?
o Dysphagia for Solids
• Investigate with a barium swallow/endoscopy
What is oropharyngeal dysphagia?
o Dysphagia for liquids
• Investigate with a flexible endoscopy evaluation of swallowing. This will allow you to view the entire trachea/oesophagus.
• Most commonly due to a stroke
How is the body adapted to prevent acid reflux from the stomach?
The stomach produces strong acids (HCl) and enzymes (pepsin) to aid in the digestion of food. The mucosa of the stomach provides protection from it’s harmful content, but the mucosa of the oesophagus does not have this protection.
The oesophagus is protected from these acids by a one way valve mechanism at it’s junction with the stomach.
This one way valve is called the lower oesophageal sphincter. This coupled with the angle of His that is formed at this point prevents the contents of the stomach refluxing back into the oesophagus.
The crus of the diaphragm helps with the sphincteric action.
What are some consequences of free gastro-oesophageal reflux?
Barrett’s oesophagus
Gastro-oesophageal Reflux Disease (GORD)
What is Barrett’s oesophagus?
An abnormal change of the epithelial cells of the oesophagus.
This is a metaplasia from non-keratinised stratified squamous epithelia to columnar epithelium and goblet cells. This is in an attempt to better resist the harmful contents of the stomach.
Barrett’s oesophagus is strongly associated with adenocarcinoma, a particularly lethal cancer.
What is GORD?
The reflux of the stomach’s contents into the oesophagus and pharynx causes several symptoms, including a cough, hoarseness and asthma.
All of the symptoms result from the acidic contents of the stomach refluxing back out.
Describe the structure of the abdominal wall and it’s boundaries
Although it is continuous, the abdominal wall is subdivided into the anterior wall, right and left lateral walls and the posterior wall. The boundary between the anterior and the lateral walls is indefinite; therefore the term anterolateral abdominal wall is used.
The anterolateral abdominal wall is bounded superiorly by the cartilages of the 7th-10th ribs, and the xiphoid process of the sternum, and inferiorly by the inguinal ligament and the superior margins of the anterolateral aspects of the pelvic girdle (iliac crests, pubic crests and pubic symphysis).
What does the anterolateral abdominal wall consist of?
The anterolateral abdominal wall consists of skin, subcutaneous tissue (superficial fascia/fat), muscles and their aponeuroses, deep fascia, extraperitoneal fat and parietal peritoneum.
What are the major landmarks of the abdominal wall?
Umbilicus Epigastric Fossa (Pit of the stomach) Linea Alba Pubic Crest and Symphysis Inguinal Groove Semilunar lines Tendinous Intersections of Rectus Abdominis Arcuate Line (aka Douglas’ line)
What is the umbilicus?
Obvious feature of the anterolateral abdominal wall at Spinal Level L3
What is the epigastric fossa? (Pit of the stomach)
Slight depression in the epigastric region, just inferior to the xiphoid process. Particularly noticeable when a person is in the supine position because the abdominal organs spread out. Heartburn is commonly felt at this site.
What is linea alba?
Aponeuroses of abdominal muscles, separating the left and right rectus abdominis. Visible in lean individuals because of the vertical skin groove superficial to it. If the linea alba is lax, when the rectus abdominis contract the muscles spread apart. This is called divarication of recti.
What is the pubic crest and symphysis?
The upper margins of the pubic bones and the cartilaginous joint that unite them. Can be felt at the inferior end of the linea alba.
What is the inguinal groove?
A skin crease that is parallel and just inferior to the inguinal ligament (runs between ASIS and pubic tubercle). Marks the division between the abdominal wall and the thigh.
What are the semilunar lines?
Slightly curved, Tendinous line on either side of the rectus abdominis.
What are the tendinous interjections of rectus abdominis?
Clearly visible in persons with well-developed rectus muscles. The interdigitating bellies of the serratus anterior and external oblique muscles are also visible.
What is the arcuate line (aka Douglas line)?
Where the fibrous sheath stops (inferior limit of the posterior layer of the rectus sheath). 1/3 of the way from the umbilicus to the pubic crest.
Describe the abdominal musculature
There are five (bilaterally paired) muscles in the anterolateral abdominal wall, three flat muscles and two vertical muscles.
Flat Muscles – External Oblique, Internal Oblique and Transversus Abdominis
Vertical Muscles – Rectus Abdominis and Pyramidalis
The three flat muscles’ fibres have varying orientations, with the fibres of the Obliques running diagonally and perpendicular to each other, and the fibres of the Transversus running transversely.
All three flat muscles are continued anteriorly and medially as strong, sheet-like aponeuroses. Between the mid-clavicular line and the midline, the aponeuroses form the tough, aponeurotic, tendinous rectus sheath that encloses the Rectus Abdominis.
The aponeuroses then interweave with their fellows of the opposite side, forming the linea alba, which extends from the xiphoid process to the pubic symphysis. The interweaving is not only between right and left sides, but also between intermediate and deep layers.
The two vertical muscles of the anterolateral abdominal wall are contained within the rectus sheath, the large Rectus Abdominis and small Pyramidalis.
What are the most important features to consider when designing an incision and why?
When designing an incision, we want one that we can close and provide long-lasting strength, thus minimising the incidence of incisional herniae. If we try to sew muscle together, the sutures will ‘cut out’.
What is a midline incision?
Surgeons suture the linea alba together to provide a strong closure.
What is a transverse incision?
Surgeons suture the external oblique aponeuroses together to provide a strong closure
What incision is used for an appendicectomy?
o Incision at McBurney’s point
o 2/3rds of the distance between the umbilicus and ASIS
o Through a ‘gridiron’ muscle-splitting incision
What is a gridiron incision?
Put scissors in and open and close them to separate out the muscle fibres, followed by the next two layers. Have to separate out the fibres of the external and internal oblique’s and the transversalis.
What is a patent Urachus?
Can present at birth or in later life in men when they develop bladder outflow obstruction due to benign prostatic hypertrophy.
What is the Vitelline duct?
Vitelline Duct – omphalomesenteric duct- attaches the yolk sac (via the umbilicus) to the midgut lumen of the developing foetus
Can persist resulting in a number of different abnormalities- Meckel’s diverticulum in particular
What is Meckels’ diverticulum?
Also known as Ilieal Diverticulum, and is the most common GI abnormality. It is a ‘cul-de-sac’ in the ileum. Meckel’s Diverticulum follows a Rule of 2’s: o 2% of the population affected o 2 feet from the ileocecal valve o 2 inches long o Usually detected in under 2’s • Can be asymptomatic o 2:1 Male:Female The diverticulum can contain ectopic gastric or pancreatic tissue. The ectopic tissue will secrete enzymes and acids into tissue not protected from them, causing ulceration. The reason for this is not clear.
What is a Vitelline cyst?
The vitelline duct forms fibrous strands at either end.
What is a Vitelline fistula?
There is direct communication between the umbilicus and the intestinal tract. This results in faecal matter coming out of the umbilicus
What is omphalocoele?
Omphalocoele is the persistence of physiological herniation. A part of the gut tube fails to return to the abdominal cavity following its normal herniation into the umbilical cord. Since the umbilical cord is covered by a reflection of the amnion, this epithelial layer covers the defect.
Compare but DO NOT CONFUSE WITH umbilical hernia.
What is gastroschisis?
Gastroschisis is the failure of closure of the abdominal wall during folding of the embryo, leaving the gut tube and its derivatives outside the body cavity.
There is no covering over the gut tube/derivatives as they herniate through the abdominal wall directly into the amniotic cavity.
What is somatic referred pain?
Pain caused by a noxious stimulus to the proximal part of a somatic nerve that is perceived in the distal dermatome of the nerve.
E.g. Shingles affects nerves; pain is felt distally along the nerves from the problem.
Source - tissues such as skin, muscle, joints, bones, and ligaments - often known as musculo-skeletal pain.
Receptors activated - specific receptors (nociceptors) for heat, cold, vibration, stretch (muscles), inflammation (e.g. cuts and sprains which cause tissue disruption), and oxygen starvation (ischaemic muscle cramps).
Characteristics - often sharp and well localised, and can often be reproduced by touching or moving the area or tissue involved.
What is visceral referred pain?
In the thorax and abdomen, visceral afferent pain fibres follow sympathetic fibres back to the same spinal cord segments that gave rise to the preganglionic sympathetic fibres.
The CNS perceives visceral pain as coming from the somatic portion of the body supplied by the relevant spinal cord segments.
Visceral pain is caused by ischaemia, abnormally strong muscle contraction, inflammation and stretch.
Touch, burning, cutting and crushing does not cause visceral pain.
Source - internal organs of the main body cavities. There are three main cavities - thorax (heart and lungs), abdomen (liver, kidneys, spleen and bowels), pelvis (bladder, womb, and ovaries).
Receptors activated - specific receptors (nociceptors) for stretch, inflammation, and oxygen starvation (ischaemia).
Characteristics - often poorly localised, and may feel like a vague deep ache, sometimes being cramping or colicky in nature. It frequently produces referred pain to the back, with pelvic pain referring pain to the lower back, abdominal pain referring pain to the mid-back, and thoracic pain referring pain to the upper back.
How is visceral referred pain related to the embryological development of the heart?
Foregut Pain – Epigastric region
Midgut pain – Periumbilical region
Hindgut Pain – Suprapubic region
Where do retro peritoneal organs produce pain?
Retroperitoneal structures can cause central back pain, e.g. pancreas and abdominal aorta.
Were are the common sites of pain in acute appendicitis?
In early appendicitis the pain begins at the umbilicus, since the innervation of the appendix enters the spine at that Level (T10).
Later, as the appendix becomes more inflamed it irritates the surrounding bowel wall, localising the pain to the right lower quadrant (irritation to somatic nerve).
Where is pain felt in small/ large bowel colic?
Doubled over in pain.
Small bowel colic Periumbilical (midgut)
Large bowel colic Suprapubic (hindgut)
Where is pain felt in Renal colic?
Patient rolls around on the floor.
Pain is “worse than child birth”.
What are some causes of Referred Diaphragmatic irritation and where is pain felt?
o Ruptured spleen
o Ectopic Pregnancy
o Perforated ulcer
Blood pools in pelvis, giving pain. The patient feels faint due to the loss of blood, so lies down causing the blood to rush up to the diaphragm (C3/4/5). The presence of blood here results in referred pain to the left shoulder (Liver is in the way of the blood at the right diaphragm).
Describe the peritoneal cavity as a potential space
The peritoneal cavity is a potential space of capillary thinness between the parietal and visceral layers of peritoneum. It contains no organs, but contains a thin film of peritoneal fluid. Lymphatic vessels, particularly on the interior surface of the diaphragm absorb the peritoneal fluid.
How does the peritoneal cavity differ in females and males?
In males the peritoneal cavity is completely closed, but in females there is a communication pathway to the exterior of the body through the uterine tubes, cavity and vagina. The communication constitutes a potential pathway of infection from the exterior.
Describe the structure of the peritoneum
The peritoneum is a continuous, two layered membrane - the parietal peritoneum, which lines the internal surface of the abdominal wall and the visceral peritoneum, which invests viscera such as the stomach and intestines.
Both layers of the peritoneum consist of mesothelium, a layer of simple squamous epithelial cells.
Describe some features of the parietal peritoneum
The parietal peritoneum is served by the same blood, lymphatic and somatic nerve supply as the region of the wall it lines. Therefore, like the overlying skin, the interior of the body wall is sensitive to pressure, pain, heat and cold and laceration. Pain is generally well localised, apart from on the inferior surface of the central part of the diaphragm, which is innervated by the phrenic nerve (C3/4/5, referred pain to shoulder). This explains why the pain from appendicitis shifts to over the appendix, as the parietal peritoneum becomes inflamed, localising the pain.
Describe some features of the visceral peritoneum
The visceral peritoneum shares the same blood, lymphatic and visceral nerve supply as the organs it covers. Also, like the organs it covers the visceral peritoneum is insensitive to touch, heat and cold and laceration; it is stimulated primarily by stretching and chemical irritation. The pain produced is poorly localised, being referred to the dermatomes of the spinal ganglia providing the sensory fibres.
What is a mesentery?
A mesentery is a double layer of peritoneum that occurs as a result of the invagination of the peritoneum by an organ and constitutes a continuity of the visceral and parietal peritoneum. A mesentery connects an intraperitoneal organ to the body wall (usually the posterior abdominal wall)
What is an omentum?
An omentum is a double-layered extension or fold of peritoneum that passes from the stomach and proximal part of the duodenum to adjacent organs in the abdominal cavity
What is the greater omentum?
A prominent, four-layered peritoneal fold that hands down like an apron from the greater curve of the stomach. After descending it folds back and attaches to the anterior surface of the transverse colon and its mesentery.
What is the lesser omentum?
A much smaller, double-layered peritoneal fold that connects the lesser curvature of the stomach and the proximal part of the duodenum to the liver. It also connects the stomach to the portal triad.
What is a peritoneal ligament?
A double layer of peritoneum that connects an organ with another organ or to the abdominal wall
Where do peritoneal ligaments connect the liver to?
Peritoneal Ligaments Connect the Liver to:
o Anterior abdominal wall – Falciform Ligament
o Stomach – Hepatogastric Ligament (membranous portion of lesser omentum)
o Duodenum – Hepatoduodenal Ligament (the thickened free edge of the lesser omentum, which conducts the portal triad – portal vein, hepatic artery, bile duct)
Where do peritoneal ligaments connect the stomach to?
Peritoneal Ligaments Connect the Stomach to:
o Inferior surface of the diaphragm – Gastrophrenic Ligament
o Spleen – Gastrosplenic ligament
o Transverse colon – Gastrocolic ligament (greater omentum)
In what 2 ways can structures of the peritoneum be classified?
o Intraperitoneal are completely covered by peritoneum, however not completely enclosed due to the mesentery (think of the concept of a fist in the balloon).
o Retroperitoneal / extraperitoneal are outside the peritoneal cavity and thus are only partially covered by the parietal peritoneum, for example the kidneys lie between parietal peritoneum (only found on the anterior surface) and the posterior abdominal wall.
• Kidneys, ureters, and the bladder
• The aorta and the IVC,
• The oesophagus
• The duodenum (except for the proximal part)
• Most of the pancreas,
• The ascending and descending colon, and the rectum.
What planes divide the abdominal wall and what 9 surface regions are there?
The abdomen is divided by the midclavicular lines vertically and the subcoastal and transtubercular lines horizontally.
Right hypochondriac, epigastric, left hypochondriac
Right lumbar, umbilical, left lumbar
Right iliac, suprapubic, left iliac
Explain the relationship between the transverse mesocolon and the supra and infra colic compartments
The Transverse Mesocolon (mesentery of the transverse colon) divides the abdominal cavity into a Supracolic Compartment, containing the stomach, liver, and spleen, and an Infracolic Compartment, containing the small intestine and ascending and descending colon.
The Infracolic Compartment lies posterior to the greater omentum and is divided into the right and left Infracolic spaces by the mesentery of the small intestine.
By what means does the supra and infra colic compartments communicate?
Free communication occurs between the Supracolic and the Infracolic compartments through the Paracolic Gutters, the groves between the lateral aspect of the ascending or descending colon and the posterolateral abdominal wall.
What is the greater sac?
The Greater Sac is made up of the Supracolic and Infracolic compartments
What is the lesser sac?
The Lesser Sac, or Omental bursa, is an extensive sac-like cavity that lies posterior to the stomach, lesser omentum, and adjacent structures. It has a superior recess, limited superiorly by the diaphragm and the posterior layers of the coronary ligament of the liver, and an inferior recess between the superior parts of the layers of the greater omentum. Most of the inferior recess becomes sealed off from the main part (posterior to the stomach) after adhesion of the anterior and posterior layers of the greater omentum.
The Lesser Sac/Omental bursa permits free movement of the stomach on the structures posterior and inferior to it because it’s anterior and posterior walls slide smoothly over one another.
By what means do the greater and lesser sac communicate with one another?
The Greater and Lesser (omental bursa) Sacs communicate through the omental foramen (epiploic foramen), an opening situated posterior to the free edge of the less omentum (hepatoduodenal ligament – see above). The omental foramen can located by running a finger along the gall bladder to free the edge of the lesser omentum, and usually admits two fingers.
What is the right subphrenic space?
The Right Subphrenic Space lies between the diaphragm and the anterior, superior and right lateral surfaces of the right lobe of the liver.
It is bounded on the left side by the falciform ligament and behind by the upper layer of the coronary ligament. It is a relatively common site for collections of fluid after right-sided abdominal inflammation.
What is the left subphrenic space?
The Left Subphrenic Space lies between the diaphragm, the anterior and superior surfaces of the left lobe of the liver, the anterosuperior surface of the stomach and the diaphragmatic surface of the spleen.
It is bounded to the right by the falciform ligament and behind by the anterior layer of the left triangular ligament. It is much enlarged in the absence of the spleen and is a common site for fluid collection, particularly after a splenectomy.
Which subphrenic space is larger than the other? And why?
The left Subphrenic space is substantially larger than the right (liver is on the right).
What are the Recto-uterine and Vesico-Uterine Pouches?
In females the peritoneum passes from the rectum to the posterior vaginal fornix and then back to the uterine cervix and body as the recto-uterine fold, which descends to form the recto-uterine pouch (of Douglas).
The peritoneum spreads over the uterine fundus to its anterior surface as far as the junction of the body and cervix, from which it is reflected forwards to the upper surface of the bladder, forming a shallow Vesico-uterine pouch.
What is the Recto-vesicle Pouch?
In males the peritoneum leaves the junction of the middle and lower thirds of the rectum, passing forwards to the upper poles of the seminal vesicles and superior aspect of the bladder. Between the rectum and bladder it forms the rectovesical pouch.
Describe the mesentery of the small intestine
A broad, fan shaped fold, connecting the coils of the jejunum and ileum to the posterior abdominal wall. Between the two sheets of peritoneum are blood vessels, lymph vessels are nerves. This allows these part of the intestine to move relatively freely within the abdominal cavity.
The attached, parietal border is the root of the mesentery about 15 cm from the duodenojejunal flexture at the level of left side L2, obliquely (towards inferior right) to the ileocaecal junction.
The root of the mesentery crosses the second and third parts of the duodenum, abdominal aorta, inferior vena cava, right ureter, right psoas major muscle and right gonadal artery.
Describe the sigmoid mesocolon
This is a peritoneal fold attaching the sigmoid colon to the pelvic wall, the attachment being an inverted V with an apex near the division of the left common iliac artery.
The left limb descends medial to the left psoas major and the right passes into the pelvis to end in the midline at the level of the third sacral vertebra. Sigmoid and superior rectal vessels run between its layers and the left ureter descends into the pelvis behind its apex.
Where are the four most common sites of hernia formation?
Inguinal
Femoral
Umbilical
Epigastric
Describe the structure of the inguinal canal
The inguinal canal is an oblique passage that extends in a downward and medial direction. It begins at the deep (internal) inguinal ring and continues for approximately 4cm, ending at the superficial (external) inguinal ring. The canal lies in between the muscles of the anterior abdominal wall and runs parallel and superior to the medial half of the inguinal ligament (the inguinal ligament is the inferior border of the aponeurosis of the external oblique muscle, attached between the ASIS and the pubic tubercle).
The spermatic cord in men and the round ligament of the uterus in women passes through the canal. Additionally, in both sexes the ilioinguinal nerve passes through part of the canal.
What is an inguinal hernia?
An inguinal hernia is a protrusion of the abdominal cavity contents through the inguinal canal. They are very common (Lifetime risk 27% for men, 3% for women).
What is a direct inguinal hernia?
Protrudes into the inguinal canal through a weakened area in the transversalis fascia near the medial inguinal fossa within an anatomical region known as the Inguinal / Hesselbach’s triangle.
What is an indirect inguinal hernia?
Protrudes through the deep inguinal ring, within the diverging arms of the transversalis fascial sling. Most indirect inguinal hernias are the result of the failure of embryonic closure of the deep inguinal ring after the testicle has passed through it.
Describe epigastric hernias
Epigastric Hernias occur in the epigastric region, in the midline between the xiphoid process and the umbilicus, through the linea alba.
The primary risk factors are obesity and pregnancy.
Describe umbilical hernias
Umbilical Hernias occur through the umbilical ring. They are usually small and result from increased intra-abdominal pressure in the presence of weakness and incomplete closure of the anterior abdominal wall after ligation of the umbilical cord at birth.
Acquired umbilical hernias occur in adults, most commonly in women and obese people.
What is a femoral hernia?
Femoral Hernias are a protrusion of abdominal viscera into the femoral canal, occurring through the femoral ring.
What is an umbilical hernia?
A protrusion of the abdominal cavity contents through the umbilical ring
What is an epigastric hernia?
A protrusion of the abdominal cavity contents in the midline between the xiphoid process and the umbilicus- through the linea alba
Describe a femoral hernia
Femoral Hernias are a protrusion of abdominal viscera into the femoral canal, occurring through the femoral ring. A femoral hernia appears as a mass, often tender, in the femoral triangle.
Femoral Hernias are bounded by the femoral vein laterally and the lacunar ligament medially. The hernia compresses the contents of the femoral canal (loose connective tissue, fat and lymphatics) and distends the wall of the canal.
Initially femoral hernias are small, as they are contained within the canal, but they can enlarge by passing inferiorly through the saphenous opening into the subcutaneous tissue of the thigh.
Femoral Hernias are more common in females as they have wider pelves.
Strangulation of femoral hernias may occur because of the sharp, rigid boundaries of the femoral ring.
What is a strangulation of a hernia?
The constriction of blood vessels, preventing the flow of blood to tissue
What is incarceration of a hernia?
Hernia cannot be reduced, or pushed back into place, at least not without very much external effort.
What parasympathetically innervates the parotid gland?
Glossopharangeal nerve (CN9) Otic ganglion
What parasympathetically innervates the submaxillary and sublingual glands?
Facial nerve (CN7) Submandibular ganglion (submaxillary)
What is the sympathetic innervation of the salivary glands?
Superior cervical ganglion
What is released from the adrenal cortex that increases the rate of ductal recovery of Na+? How does it do this?
Aldosterone
Increases activity of ENaC and Na/K ATPase
Makes saliva very very hypotonic
Describe the structure of the oesophagus
Muscular tube connecting pharynx to the stomach
About 8 inches long
Lined by mucosa- non keratinised stratified squamous
Runs posteriorly to trachea and heart
Runs anteriorly to spine
Just before entering the stomach it passes through the diaphragm
Upper 1/3 - voluntary striated muscle
Lower 2/3 - smooth muscle under control of PSNS
What is the function of the oesophagus?
Carries food, liquids, and saliva (bolus) from mouth to stomach
What are the borders of Hesselbachs triangle?
The borders of Hesselbach’s triangle are:
o Inferiorly – Medial half of the inguinal ligament
o Medially – Lower lateral border of rectus abdominis
o Laterally – Inferior epigastric artery
Oesophagus Stomach - function Stomach - anatomy Gastric disease Liver Biliary tree Pancreas Gall bladder Spleen
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How long is the oesophagus?
25cm
What is the average diameter of the oesophagus?
2cm
What are the three constrictions of the oesophagus?
Normally has 3 constrictions where adjacent structures produce impressions
- cervical constriction (upper oesophageal spinchter) - at its beginning at the pharyngo-oesophageal junction; approx. 15cm from incisor teeth; caused by cricopharyngeus muscle
- thoracic (broncho-aortic) constriction- compound constriction where it is first crossed by the arch of the aorta 22.5cm from incisor teeth, and then where it is crossed by the left main bronchus 27.5cm from the incisor teeth
- diaphragmatic constriction- where it passes through oesophageal hiatus of diaphragm, approx. 40cm from incisor teeth
How many layers of muscle does the oesophagus have and how does it vary along the oesophagus?
Has internal circular and external longitudinal layers of muscle
Superior 1/3 - voluntary striated muscle
Middle 1/3 - both
Inferior 1/3 - smooth muscle
What part of the diaphragm does the oesophagus pass through?
Passes through elliptical oesophageal hiatus in the muscular right crus of the diaphragm, just to the left of the median plane at level of T10 vertebra
Where in the stomach does the oesophagus terminate?
Terminates by entering the stomach at the cardial orifice of the stomach to the left of the midline at the level of the 7th left costal cartilage and T11 vertebra
What nerve plexus is the oesophagus encircled by distally?
Oesophageal (nerve) plexus
How does food move rapidly through the oesophagus?
Food passes through rapidly because of the peristaltic action if it’s musculature aided but not dependent on gravity
How is the oesophagus attached to the diaphragm? What does this allow?
Oesophagus attached to margins of oesophageal hiatus in the diaphragm by the phrenico- oesophageal ligament - extension of inferior diaphragmatic fascia
Permits independent movement of the diaphragm and oesophagus during respiration and swallowing
Where is the oesophagus trumpet shaped and why?
Abdominal part of the oesophagus only 1.25cm long passes from oesophageal hiatus pin the right crus of the diaphragm to the cardial orifice of the stomach, widening as it approaches, passing anteriorly and to the left as it descends inferiorly
Describe the peritoneum around the oesophagus
Anterior surface covered with peritoneum of the greater sac, continuous with that covering the anterior surface of the stomach
Posterior part of abdominal part of oesophagus is covered with peritoneum of the omental bursa, continuous with that covering the posterior surface of the stomach
Describe the oesophagus’ location in relation to the stomach
Right border- Continuous with the lesser curvature of the stomach
Left border- separated from fundus of stomach by cardiac notch between oesophagus and fundus
Describe the oesophagus’ location in relation to the liver
Fits into a groove on the posterior surface of the liver
What is the arterial supply to the oesophagus?
Abdominal oesophagus- left gastric artery, (branch of coeliac trunk) and left phrenic artery
Describe the venous drainage of the oesophagus
Submucosal veins - portal venous sytem via left gastric veins
Submucosa veins - systemic venous system via the oesophageal veins entering the azygous system
Describe the lymphatic drainage of the oesophagus
Of abdominal part is to left gastric lymph nodes - efferent lymphatic vessels from these nodes drain mainly to celiac lymph nodes
What are the functions of the stomach?
Stores food
Disinfects food
Breaks food down into chyme- chemical disruption (acid and enzymes) and physical disruption (motility)
Where in the stomach do secretions come from?
From gastric pits (contain neck cells) -indentations in stomach mucosa that are openings to gastric glands (contain parietal, chief and G cells (& smooth muscle cells))
What cells in the stomach produce hydrochloric acid? What’s the importance of HCl?
Parietal cells
Acid keeps the pH<2
What cells in the stomach produce proteolytic enzymes (pepsin)? What’s the importance of these enzymes?
Chief cells
Non specifically breaks down proteins - > peptides
What cells in the stomach produce mucus? What is the importance of this mucus?
Neck cells
Sticky so that it’s not easily removed from the stomach lining and basic, due to amine group on the proteins
What cells in the stomach produce HCO3-? What is the importance of HCO3-?
Neck cells
Secreted by neck cells into the mucus and provide a buffer for H+ ions
What cells in the stomach produce Gastrin? What is the importance of gastrin?
Binds to surface receptor on the parietal cell stimulating acid and intrinsic factor (B12- anaemia)
How is stomach acid produced and secreted into the stomach from the parietal cells?
In mitochondria of parietal cells, water is split into H+ and OH- ions- generating lots of H+ ions
Generated OH- ions combine with CO2 fro metabolism to form HCO3- which is exported to the blood (for every mole of H+ secreted into the stomach, 1 mole of HCO3- enters the blood)
H+ produced at a fast rate as parietal cells have lots of mitochondria - but can’t be allowed to accumulate in the cells
Parietal cells have canaliculi (invaginations of the cell wall) which have proton pumps - expel H+ against a high concentration gradient
As concentration gradient is very high, it’s a very energy intensive process
What are the three main factors that stimulate parietal cells to release acid in the stomach?
Gastrin
Histamine
Acetyl chlorine
What triggers gastrin to be produced in the stomach?
Peptides
Acetyl choline from intrinsic neurones - after they have detected distension (ACh also acts directly in parietal cells)
How does gastrin stimulate acid secretion in the stomach?
Hormone is secreted by G cells in stomach
Polypeptide, main form is 17AAs long
Binds to surface receptor on parietal cell
Stimulates acid and intrinsic factor secretion via second messenger pathway
What inhibits gastrin being produced in the stomach?
Low pH in stomach - negative feedback
What stimulates histamine production in the stomach?
Gastrin and ACh stimulate mast cells to secrete histamine
How does histamine stimulate acid secretion from parietal cells in the stomach?
Released from mast cells
Binds to H2 surface receptors on parietal cells, locally
Acid secretion stimulated via c-amp
Works as an amplifier
How does acetyl choline stimulate acid secretion in the stomach?
Released from postganglionic parasympathetic neurones
Acts on muscarinic receptor in the parietal cell
Stimulates acid secretion by second messenger pathway
What stimulates ACh secretion in the stomach?
Distension
What are the 3 phases of gastric secretion?
Cephalic phase
Gastric phase
Intestinal phase
Describe the cephalic phase of gastric secretion
The ‘brain led’ phase. The sight and smell of food, and the act of swallowing, activates the parasympathetic nervous system, which stimulates the release of Ach. This stimulates parietal cells directly and via histamine (increases Acid).
Describe the gastric phase of gastric secretion
Once food reaches the stomach, it causes distension, further stimulating Ach release, and subsequently parietal cells (increases Acid).
The arrival of food will also buffer the small amount of stomach acid in the stomach in between meals, causing luminal pH to rise. This disinhibits Gastrin (increases Acid).
Acid and enzymes will then act on proteins to produce peptides, further stimulating Gastrin release as the pH falls and the initial disinhibition is removed (increases Acid).
Describe the intestinal phase of gastric secretion
Once chyme leaves the stomach in significant quantities, it stimulates the release of the hormones Cholecystokinin and Gastric Inhibitory Polypeptide from the intestines that antagonise Gastrin (decreases Acid). Coupled with this, the small amount of acid left in the stomach is no longer being buffered by food, and the low pH inhibits Gastrin (decreases Acid).
What drugs affect acid secretion?
Acid secretion may be reduced by inhibition of:
o Histamine at H2 Receptors
E.g. Cimetidine
Removes the amplification of Gastrin/Ach signal
o Proton Pump Inhibitors (PPIs)
E.g. Omeprazole
Prevents H+ ions being pumped into parietal cell canaliculi
o also treat ulcers by eliminTing H pylori with antibiotics
Describe the stomachs defences to acid
The luminal pH of the stomach is usually below 2. Without any protection, this would dissolve mucosa. Neck cells secrete mucus to protect the mucosa.
Mucus is Sticky, so is not easily removed from the stomach lining. It is also Basic, due to Amine groups on the proteins.
The mucus forms a ‘unstirred layer’ that ions cannot move through easily.
H+ ions slowly diffuse in and react with the basic groups on mucus and with HCO3- that is secreted by surface epithelial cells.
Because of the unstirred layer, HCO3- stays close to the surface cells. This means the pH at the surface cells is well above 6.
Mucus and HCO3- secretion from neck cells and surface cells respectively is stimulated by prostaglandins, which are promoted by most factors that stimulate acid secretion.
How are the stomachs defences breached?
o Alcohol
• Dissolves the mucus, allowing the acid to attack the stomach
o H. Pylori
• Surface cells become infected, inhibiting mucus/HCO3- production
o NSAIDS
• Inhibit prostaglandins, therefore reducing defences
• Some, like aspirin are converted to a non-ionised form by stomach acid, allowing them to pass through the mucus layer into cells before they re-ionise.
What are the two mechanisms of stomach motility?
Receptive relaxation
Rhythmic contractions
What is receptive relaxation of the stomach?
As food travels down the oesophagus, a neural reflex carried out by the vagus nerve triggers the relaxation of the muscle in the stomach’s wall, so pressure does not increase. This means that pressure in the stomach does not increase as it fills limiting reflux and allowing us to consume large meals (but not if there is damage to the vagus nerve).
What are the rhythmic contractions of the stomach?
The stomach has longitudinal and circular muscle that is driven by a pacemaker in the cardiac region. The pacemaker fires ~3 times a minute, causing regular, accelerating peristaltic contractions from the Cardia to Pylorus.
This, combined with the stomach’s funnel shape both mixes the contents of the stomach and moves liquid chyme into the pyloric region. This occurs as the accelerating peristaltic wave overtakes larger lumps, driving them back into the fundus. Chyme however is decanted into the pyloric region.
Describe gastric emptying
Accelerating, rhythmic, peristaltic contraction moving solid lumps backwards into the fundus of the stomach whilst letting liquid chyme moving forwards
As chyme enter pyloric region, a small squirt is ejected before the peristaltic wave reaches the Pylorus and shits it - so rest of chyme returns to stomach
How is gastric emptying controlled?
3 peristaltic waves - 3 ejected squirts of chyme a minute
Squirt volume affected by rate of acceleration of peristaltic wave and hormones from the intestine
Gastric emptying slowed by fat, low pH and hypertonicity in the duodenum
What is the stomach?
Expanded part of the GI tract between the oesophagus and duodenum
What is the stomach specialised for?
Specialised for accumulation of ingested food
How much food can the adult stomach hold?
2-3litres
What are the 5 recognisable parts of the stomach?
Cardia Fundus Body Antrum Pylorus
What are the 2 curvatures of the stomach?
Greater and lesser
Which part of the stomach releases HCl and pepsinogen generally?
Upper 2/3
What part of the stomach releases mucus and gastrin generally?
Lower 1/3
What two spinchters are found at the entrance and exit of the stomach?
Inferior oesophageal spinchter
Pyloric spinchter
Describe the inferior oesophageal spinchter
Lies to left of T11 vertebral on horizontal plane through tip of xiphoid process
Immediately superior to Z line diaphragmatic musculature forming the oesophageal hiatus functions as a physiological spinchter that contracts and relaxes
This coupled with the cardiac notch prevents reflux
What is the Z line?
Line where the mucosa abruptly changes from oesophageal to gastric is the Z line
Describe the pyloric spinchter
At pyloric end of stomach, circular muscle coat is thickened to produce the pyloric spinchter
This controls the discharge of stomach contents through the pyloric orifice into the duodenum
What’s the macroscopic structure of the gastric mucosa?
When empty the gastric mucosa is thrown into longitudinal folds called RUGAE
Gastric canal forms temporarily between gastric folds along lesser curvature of stomach to allow saliva and other fluids (and small amounts of chewed food) to pass along to the pylorus
What’s the microscopic structure of the gastric mucosa?
Columnar type epithelia
Cardia- neck cells–> mucus
Fundus and body- neck cells –> mucus ; parietal cells –> acid ; chief cells –> pepsinogen
Pylorus - neck cells–> mucus ; G cells –> gastrin
What are 4 features in the abdomen associated with the stomach?
Greater omentum
Lesser omentum
Epiploic foramen
Coeliac trunk
What is the greater omentum?
A prominent, four-layered peritoneal fold that hands down like an apron from the Greater Curve of the Stomach. After descending it folds back and attaches to the anterior surface of the Transverse Colon and its mesentery
What is the lesser omentum?
A much smaller, double-layered peritoneal fold that connects the Lesser Curvature of the Stomach and the Proximal part of the Duodenum to the Liver. It also connects the stomach to the portal triad.
What is the epiploic foramen?
The Greater and Lesser (omental bursa) Sacs communicate through the omental foramen (epiploic foramen), an opening situated posterior to the free edge of the less omentum (hepatoduodenal ligament – see above). The omental foramen can located by running a finger along the gall bladder to free the edge of the lesser omentum, and usually admits two fingers.
What is the coeliac trunk?
Originates from the abdominal aorta, giving rise to left gastric, splenic and common hepatic arteries
