GI Tract Theme 1
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- Created by: Splodge97
- Created on: 22-05-17 10:04
Why is the diaphragm double domed? What does this mean?
Because its central tendon is attached lower then its right and left domes; this causes the costo-diaphragmatic and costo-mediastinal recesses to be formed
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Where is the diaphragm attached?
Sternal attachment = xiphoid process. Costal attachment = 6 lower cartilages of the costal margin. Vertebral attachment = left and right crurae and medial and lateral lumbocostal arches.
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What are the apertures of the diaphragm? What do they transmit?
Caval (T8) = inferior vena cava and (right) phrenic. Oesophageal (T10) = oesophagus and vagus. Aortic (T12) = descending arota and sympathetic chain.
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What are the functions of the diaphragm?
Relaxes in expiration/contracts in inspiration (larger resting role in men) and aids defaeceation, micturation, lifting objects and parturition.
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What is the fuunction of the crurae and cardio-oesophageal sphincter?
Prevent acid reflux into the oesophagus (fails in hiatus hernia/pregnancy to increase risk of oesophageal carcinoma)
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What is the innervation of the diaphragm?
Motor = phrenic. Sensory = phrenic (central), lower 5 intercostals (lateral)
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What are the functions of the anterior abdominal wall?
Enable trunk movements, aid abdominal pressure regulation and aid forced expiration
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What are the attachments of rectus abdominis (central abdominal muscle)? What is its function?
Between the rib cage and pubic bone, segmented by the linea alba with a curved posterior connective tissue attachment to the linea semilunaris. Functions to pull up the abdomen.
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What are the attachments of the external oblique (lateral abdominal muscle)? What is its function?
Most external, attached to the lower 8 ribs, linea alba, pubic bone, inguinal ligament and iliac crest. Fibres run anterio-inferiorly, extends anteriorly as the external aponeurosis. Moves abdomen downwards and forwards.
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What are the attachments of the internal oblique (lateral abdominal muscle)? What is its function?
Middle layer, attaches to the pelvis, iliac crest, lumbar fascia, costal margin and linea alba. Fibres run anterio-superiorly, extends as the internal aponeurosis. Moves abdomen upwards and outwards.
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What are the attachments of transversus abbdominis (lateral abdominal muscle)? What is its function?
Innermost layer, attaches to the lower 6 ribs, lumbar fascia, iliac crest, inguinal ligament and rectus sheath. Fibres run horizontally, extends anteriorly as an aponeurosis. Acts to abstruct (narrow) the abdomen.
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What is the role of the lumbar fascia?
An attachment for internal oblique and transversus abdominis, present posteriorly between the ribs and pelvis, thick to protect the lumbar spine
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What is the transversalis (transverse) fascia?
Thin layer between the transversus abdominis and parietal peritoneum
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How is the peritoneum arranged?
Has a parietal layer in communication with the transverslis fascia and visceral layer in communication with the abdominal organs (encapsulating them to form mesenteries). Peritoneal fluid is present between them.
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Describe the innervation of the anterior abdominal wall
Originates from the intercostal nerves (run between the internal oblique and transversus abdominis) T7-T10
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What is the function of the mesenteries?
Isolate peristaltic movements from the rest of the abdominal cavity, supply blood to (via the abdominal aorta) and drain it (via the hepatic portal system) from the gut contents, protect from pathogens (contain lymphatic tissue)
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What are retroperitoneal organs?
Folds formed by the vsceral pleura behind the mesentaries (have same functions)
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What are peritoneal ligaments? Give an example
Thick parts of the mesentaries. Example is the omentum (split into a lesser omentum and greater omentum)
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Describe the lesser omentum
Separates the liver and stomach
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Describe the grater omentum
Hangs inferiorly over the abdominal contents, containing adipose. Divides the anterior abdomen into a greater sac (containing the liver and stomach) and a lesser sac (omental bursa, contains the coils fo the small intestine)
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What are the greater sac and omental bursa sub-divided into?
Greater sac = supracolic and infracolic cavities. Omental bursa = superior and inferior recess.
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Wht are the greater sac and omental bursa prone to infection?
Because they are blind ending sites which are prone to fluid accumulation
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Describe the anatomy of the stomach
Fundus originates from oesophageal opening; then main body, antrum, pylorus and pyloric sphincter leading into the duodenum. Adops a curved shape to form the greater and lesser curvatures.
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Describe the anatomy of the pancreas
In the loop of the duodenum beneath the greater curvature of the stomach. Is retoperitoneal (behind the peritoneum). Divided into a head, body and tail. Duct drains laterally into the common opening of the pancreatic duct (leads into the duodenum).
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What is the course of the biliary system?
Originates as left and right bile ducts from the liver, fuse to form the common hepatic duct. Gall bladder drains into this to form the common bile duct. Travels behind the pancreas to join the pancreatic duct (leads into the duodenum).
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Where is the spleen? What is its function?
Present anterior to the right kidney. Functions in erythropoiesis, so immense bleeding upon damage to it.
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Describe the course of the intestine
Small = duodenum (25cm), jejunum, ileum (7m). Ilio-ceacal junction. Large = ascending, transverse, descending and sigmoid colon, then rectum.
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Describe the arterial supply to the abdomen
Given by abdominal aorta via coeliac trunk (gives hepatic, splenic and left gastric), superior mesenteric (duodenum to 2/3 transverse colon and pancreas), inferior mesenteric (rest of intestine and rectum), renal and gondal. Terminates as iliac.
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Describe venous drainage of the abdomen
Given by the inferior vena cava. Branches into the renal, gonadal (on left coming off renal, on right from main trunk) and iliac. Recieves blood which has been collected by heptic portal system and processsed by liver via hepatic vein.
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Which veins darin into the hepatic portal vein?
The inferior mesenteric, splenic and superior mesenteric
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What can result from portal hypertension?
Increase in hepatic portal system pressure causing sclerosis (hardening of the tissues) and then oesophageal vavices (verrucous veins, burst)
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What are the attachments and function of psoas major?
Attached to vertebra T12-T5 and inferiorly to the femur. Flexes the hip, also brings ribcage down in respiration.
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What are the attachments and function of iliacus?
Attaches to the internal surface of the pelvic bone and femur. Flexes the hip. Lies between psoas major and quadrus lumborum.
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What are the attachments and function of quadrus lumborum?
Attached to the 12th rib, transverse processes of the L1-L5 vertebra, iliolumbar ligament and iliac crest. Acts as layeral rotator and flexor of the hip, also fixes the 12th rib (so it can act as a stable point in inspiration and expiration).
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What is the parasymapthetic innervation of the gut?
Vagus nerve - gives intramural branches (preganglionic) which pass to ganglia in the walls of the viscera. Colon, rectum and pelvic organs supplied by the pelvic parasympathetic nerves (S2-S4).
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What is the sympathetic innervation of the gut?
Supplied by T5-T12 intercostal nerves; originate from small part of sympathetic chain in the gut. Spanchnic nerves (also from sympathetic chain) or branches from the coeliac/superior mesenteric ganglia give the postgangionic sympathetic fibres.
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What are the functions of the gut?
Digestion (chemical and mechanical), absorption, excretion of endogenous and exogenous (dead epithelia) waste and defence. Communication via hormones/lymphatics/ENS also occurs.
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Describe digestion
Hydrolysis of large food particles for absorption. Takes 24-72 hours, fastest for carbs and slowest for fats. Majority in the oral cavity, oesophagus and stomach (small amount in proximal SI).
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What is the mucosa?
Innermost layer of the GI tract; comprised of an epithelium (contacts lumen), lamina propira (contains glands/lymphatics/capillaries) and muscularis mucosa (muscle, holds layers of mucosa)
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What types of epithelia may be present in the mucosa?
Stratified squamous (flat, scale like, several layers thick, protective, possibly keratinised) or columnar (absorptive, single layer, possible brush border, may secrete mucous, HCO3- or enzymes)
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What is the submucosa?
Layer of GI tract beneath the mucosa; may contain glands, the ENS (messiner's plexus) or lymphatics
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What tis the musclularis externa?
Layer of GI tract after the submucosa. Has a thickened (compared to muscularis mucosa) smooth muscle layer with inner circular fibres and outer longitudinal fibres. ENS may be between its layers.
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What is the serosa?
Most external layer of the GI trat which holds all the others together, present as connective tissue or mesothelium
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Describe oesophageal histology
Epithelium is stratifed squamous (non-keratinised). Submucosa may contain seromucous glands which lubricatte it for peristalsis. Muscularis externa has two layera. Serosa present as mesothelium.
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Describe the histology of the stomach
Epithelia is columnar and indented to form gastric pits, gastic glands lying at the bottom of these. No submucous seromucous glands. Has three layers of muscularis externa (to support mechanical digestion).
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What is present in gastric glands?
Parietal cells (secrete HCL and KCL and intrinsic factor), mucous glands, chief cells (secrete renin, pepsinogen and gastric lipase) and APUD cells (secrete polypeptide hormones, activate the other cells of gastric glands)
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Describe the histology of the small intestine
Epithelium is columnar, interspersed with goblet cells and folded to form villi (with a micro-villi brush border). Crypts of Liberkuhn at base of troughs formed by villi. Brunner's glands in submucosa. Two layers of muscularis externa, ENS between.
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What occurs in the Crypts of Liberkuhn?
New columnar epithelia formed - migrate and differentiate in 3-5 days to account for high proliferation rate. Paneth cells (20 day life) at the base secrete antimicrobial peptides (cryptins, lysozymes and phospholipase A2) when exposed to bacteria.
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Describe the histology of the large intestine
Epithelia is calumnar, with more interspersed goblet cells to move against resistance. Mucosa has lesser folding so crypts of Lieberkuhn but no villi. Lamina propira contains lymphoid tissue. Larger muscularis externa (still 2 layers), ENS between.
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Other cards in this set
Card 2
Front
Where is the diaphragm attached?
Back
Sternal attachment = xiphoid process. Costal attachment = 6 lower cartilages of the costal margin. Vertebral attachment = left and right crurae and medial and lateral lumbocostal arches.
Card 3
Front
What are the apertures of the diaphragm? What do they transmit?
Back
Card 4
Front
What are the functions of the diaphragm?
Back
Card 5
Front
What is the fuunction of the crurae and cardio-oesophageal sphincter?
Back
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