the digestive system part 1 Flashcards

Question

What are the Salivary glands?

Answer 1

• There are 3 bilateral pairs of glands which release saliva into the mouth through ducts • Parotid • Submandibular • Sub-lingual Saliva- lubricate, helps with diesting food, has antibiprobagents. Helps wash food particles to prevent damage to teeth.

Answer 2

• This is a muscular tube • It begins distal to the pharynx at around the level of C6 • The procimal cricopharyngeal sphincter prevents air entering the oesophagus at respiration and aspiration of food • Approximately 25cm long and 2cm in diameter • Lies in the midline posterior to the trachea and anterior to the spine • Passes through the diaphragm at the level of T10 (oesophageal hiatus) • At the inferior part • It curves sharply (this helps prevent regurgitation) and superiorly into the stomach at the level of T11 • The cardiac sphincter prevents reflux of stomach contents

Answer 3

• Outer layer is fibrous and attaches to the surrounding structures • There is a muscle layer for peristalsis • There are no digestive enzymes in the mucosal layer – no absorption • The arterial supply • Thorax – branches off the thoracic aorta – oesophageal arteries • Abdomen – inferior phrenic and left gastric artery • The venous drainage • Thorax – azygous vein • Abdomen – left gastric vein

Answer 4

Food is mixed with saliva which contains enzymes. • The enzymes are only activated in liquid and help to dissolve chemicals in food to aid taste • Saliva contains • 99.5% water – dissolves food • 0.5% solutes – sodium, potassium etc. • Mucous lubricates food • Immunoglobulin A –prevents attachments of microbes • Enzymes – inhibit the grown of oral bacteria • Salivation is controlled by the autonomic nervous system. • Parasympathetic – continuous secretion • Sympathetic – works during stress or dehydration – dry mouth / thirst • Chemicals in food stimulate the receptors in taste buds which result in secretion • After eating there is a flow of saliva for cleaning and diluting any remaining chemicals

Answer 5

• 3 stages according to location of bolus; takes around 4-8 seconds (1 for fluid) • Oral Stage • Mouth closed, bolus forced posteriorly by voluntary muscles of tongue / cheeks • Pharyngeal Stage • When bolus reaches oropharynx, reflex action by swallowing centre in medulla • Involuntary contraction of muscles to propel bolus into oesophagus • Other routes closed: • Soft palate elevates to close nasopharynx • Tongue/pharyngeal folds close off mouth • Larynx elevates and moves anteriorly to occlude trachea through epiglottis • Oesophageal Stage • Peristalsis only starts when stimulated when food in pharynx • Propels food to stomach, lubrication by mucous • Cardiac sphincter relaxes on peristalsis

Answer 6

X-rays • AXR (abdominal x-rays) MRI • MR enterography Fluroscopy • Barium swallows • Barium meals / follow throughs • Defaecating proctograms Ultrasound • Abdominal ultrasound • Small bowel ultrasound for inflammatory bowel disease CT • Abdominal / pelvis CT with / without contrast • CT colonography Nuclear medicine • Gastric emptying scans • Meckel scan

Answer 7

How do we look at bowel on a AXR? • Remember the 3,6,9 rule • It can be really hard to differentiate between large and small bowel on an AXR • Look for valvular conniventes and the teniae coli • Small bowel is normally more central • Large bowel often has a mottled appearance due to gas within faeces • Marsh P Normal abdominal radiograph - annotated x-ray.

Answer 8

• The stomach may be visible if it contains gas. However, if it is completely empty or completely fluid filled you may not see it. • Generally, lies at around T10 level

Answer 9

• Liver – the liver lies in the right upper quadrant and is a generally homogenous grey density • The superior edge forms the contour of the right hemidiaphragm • Sometimes breast shadow can overlie and make it difficult to see • You will generally only see the gallbladder if its abnormal or absent! • The liver doesn’t normally extend lower than the lower pole of the kidney

Answer 10

Common anatomical variant of the liver • Can be mistaken for a mass • It is where the right lobe of the liver is larger than normal and extends caudally in the abdomen • Seen in up to 31% of patients, with a female predominance

Answer 11

• Screening test for colorectal cancer • After failed or unsuitable endoscopy or patient choice • Shows the colon in much more detail than a normal CT • Patient drinks contrast – generally gastrografin • Gas is inserted to inflate the bowel

Answer 12

• Generally done as a triple phase scan • Looks for liver lesions and metastases • 3 phase • Late arterial • Portal venous phase • Delayed phase • There can also be an additional non contrast scan • The liver gets approximately 25% of its blood supply from the hepatic artery and 75% from the portal vein so needs many phases for accurate assessment • It can be hard to work out what a liver lesion is, but this helps. • Late arterial • Will see the portal vein, not the hepatic vein • Good to look for hepatocellular cancer • Portal venous • Will see portal veins and the hepatic vein • Will see if the liver is fatty • Good to look for very vascular liver tumours • Delayed phase • Some tumours may enhance compared to the rest of the liver in this late stage

Answer 13

• Non invasive technique for assessing the small bowel • Why is this good for patients with inflammatory bowel diseases? • It can demonstrate acute inflammation from disease exacerbation and complications • Patients have to drink mannitol

Answer 14

• Barium swallow • Dedicated test of the pharynx, oesophagus and proximal stomach • Patient drinks barium when instructed • Dynamic so good for functional disorders • Can be used to help patients rehabilitating after stroke or with neuro or muscular degenerative disorders • Small bowel follow through • Evaluates the small bowel dynamically • Patient drinks barium and water • Sometimes ant sickness medication is given • Is being less utilised in favour of CT or MRI • Defecating proctograms • Evaluates the pelvic floor in patients with difficulties in defaecation or with constipation

Answer 15

• Reidel’s lobe • Surgery- gallbladder removed. • Cholecystectomy • Weight loss procedures

Answer 16

• Nearly all laparoscopic • Gallbladder removed due to stones or polyps

Answer 17

Size and shape • C/J shaped • 15 – 25cm long • Volume depends on the contents – up to 4L capacity • When empty the rugae collapse and fold in, shrinking the stomach • Position • Inferior to the diaphragm • In the upper left quadrant / left epigastric and hypochondriac region

Answer 18

• Cardia • Surrounds the cardio-oesophageal sphincter • Fundus • The section lateral to the cardia • Body • Mid portion • Narrows inferiorly • Pylorus • Consists of the antrum and canal • Contains the pyloric sphincter which is continuous with the small intestine

Answer 19

• Serosa • Serosa is continuous with the visceral peritoneum • 3 muscle layers which allow churning and mixing • Mucosa • Made up of simple columnar epithelium • Contains mucus cells • Has a protective alkaline layer to protect from acids and enzymes • Gastric juices are secreted from gastric glands – up to 2-3l a day

Answer 20

There are peristaltic waves every 15-20 seconds Food is macerated It is mixed with secretions to form chyme The fundus section is mainly for storage- less movement The rugae allow for expansion and increase the surface area

Answer 21

The food may be in the fundus for more than an hour before churning begins but the salivary amylase continues to work. Food is mixed with acidic gastric juices • HCI acid • Kills microbes • Denatures proteins • Promotes flow of bile • Gastrin • Increases mobility of stomach • Relaxes the pyloric sphincter • Pepsin • Starts digestion of protein • Breaks peptide bonds making smaller chains Very small amounts of nutrients are absorbed. The epithelial cells are impermeable to most materials. Some water is absorbed. Some drugs are absorbed • Aspirin • Alcohol • The stomach empties 2-4 hours after eating • Carbohydrate rich food is the quickest • Fatty food is the slowest • Each wave moves approximately 3mm of chyme through the sphincter into the duodenum

Answer 22

• Food is prepared in the small intestine so it can enter the cells of the body • The small intestine is a muscular tube approx. 7m long from the pyloric sphincter to the ileocaecal sphincter • Longest segment of digestive tract • Parts • Duodenum – 5cm peritoneal • Rest of duodenum, jejunum, ileum are retroperitoneal • Suspended form the posterior abdominal wall by the mesentery • Surrounded by the large intestine

Answer 23

• Duodenum • 25cm long (5%) • Jejunum • 2.5m long (40%) • Ileum • 3m long (55%)

Answer 24

• C shaped • Extends from the pyloric sphincter to the jejunum • Has 4 sections • 1st – superior • 2nd – descending • 3rd – horizontal • 4th - ascending • Surrounds the head of the pancreas • Receives • Gastric chyme from the stomach • Digestive juices from the pancreas • Bile from the liver The mucosa has villi to increase the surface area. Its function is to breakdown food using enzymes. It uses hormones to regulate the rate of stomach emptying

Answer 25

• There is localised mixing contractions • The chyme mixes with digestive juices • Food comes into contact with the mucosa • Contents are not moved along •Contraction of circular muscle into segments •Muscle fibres in middle of each segment contract –dividing segment further •First fibres relax -> large segment again •Repeats – chyme sloshed back and forth •Most rapid in duodenum – 12 x per minute 8 x per minute in ileum •After most of food absorbed segmentation stops and peristalsis begins •Peristalsis migration reaches end of ileum in 90 – 120 minutes •Chyme remains in small intestines 3 – 5 hours

Answer 26

• Has villi • Has large circular folds to increase surface area of mucosa • Main function is to absorb previously digested food from the duodenum

Answer 27

• There isn’t an obvious junction between the jejunum and ileum • Has smaller and thinnerwalls than the jejunum • Function • Absorb B12 and bile salts • Absorb remaining products not absorbed in the jejunum

Answer 28

• Large because it has a larger diameter • 1.5m long • Differing diameters – 6-9cm • Runs from the ileocaecal valve to the anus • No villi on the mucus membrane as there is no chemical digestion • There are no structural alterations to increase surface area • There are goblet cells with produce mucus to ease the passage of faeces • Teniae coli • 2 bands of smooth muscle • Runs from the caecum to the rectosigmoid junction • These contact lengthwise to produce haustra • This helps to move faeces through the large bowel • Do not have them in the rectum and anus

Answer 29

• Caecum – 6cm long • Receives chyme from the ileum • Has the appendix hanging from it

Answer 30

• Ascending • 20cm long • Has the hepatic flexure at distal end • Transverse • Has hepatic and splenic flexure at either end • Descending • Left side of pelvis • Sigmoid • S shaped. Projects medially

Answer 31

•Chyme enters cecum via ileo-caecal sphincter (Usually slowly) •Gastro-colic reflex: • Food entering stomach stimulates release of Gastrin into blood •Gastrin plays a part in ileo-caecal sphincter relaxation •Allows chyme to enter caecum from ileum •Faeces in caecum triggers mass movement

Answer 32

When caecum becomes distended the contraction of the ileocaecal sphincter increases. Chyme fills caecum and accumulates in ascending colon. Haustral churning –distended by contents, walls contract moving contents to next haustrum. Peristalsis also occurs but slower 2 – 3 contractions per minute Mass peristalsis – strong peristaltic wave from mid transverse colon Drives faeces into rectum Occurs after meals – 3 – 4 times per day

Answer 33

No enzymes secreted Final stage of digestion – activity of bacteria in lumen Bacteria: Ferment any remaining carbohydrate Releases hydrogen, CO2 and methane gas Flatus – which becomes flatulence if excessive Breakdown remaining proteins and amino acids Decompose bilirubin to simpler pigments results in brown colour

Answer 34

• Water • Most water is absorbed in the large bowel • The large bowel is important in maintaining homeostasis • Bacterial products • Including vitamins – B and K

Answer 35

•Elimination of indigestible residue •When faeces into rectum by mass movement defecation reflex initiated •Spinal reflex: • Causes walls of sigmoid colon and rectum to contract • Anal sphincters relax • Faeces in anal canal messages to brain • Voluntary decision to open external sphincter • If not contraction ends and walls relax • Next mass movement initiates new reflex

Answer 36

Digestive Haematological Metabolismof nutrients Detoxification Mineral and vitamin storage Bileproduction

Answer 37

• Irregular wedge-shaped organ • The liver is the largest gland in the body • 10-12cm craniocaudally • 20-23cm transverse • It is situated under the diaphragm in the right upper quadrant extending into the left upper quadrant • It is largely protected by the ribs and overlies the stomach • It is divided into 4 lobes • Left lobe • Right lobe • Subdivided into the caudate and quadrate lobes • The 2 main lobes are divided by the falciform ligament • The falciform ligament attached the liver to the anterior abdominal wall • The liver is covered by a fibroelastic capsule made up of • Visceral peritoneum • A Glisson capsule underneath which contains blood and lymph vessels and nerves

Answer 38

A large amount of blood is needed for metabolic functions Hepatic artery – 400-500 ml/min Hepatic portal vein 1000- 1200 ml/min hepatic veins return blood to the IVC

Answer 39

Liver cells are capable of regeneration – damaged or resected liver can regrow

Answer 40

• Sac like organ • Situated on the inferior surface of the liver • It stores and concentrates bile (approximately 90mls) • Bile passes from the liver to the gallbladder via the right and left hepatic ducts into the common hepatic duct • There is resistance at the sphincter of Oddi – this controls flow into the duodenum and precents reflux • The bile passes into the gallbladder via the cystic duct

Answer 41

Approx. 30 minutes after eating the gallbladder contracts • This forces bile through the cystic duct into the common bile duct • The sphincter of Oddi relaxes • Bile passes into the duodenum via the major duodenal papilla

Answer 42

• Approx. 20cm long • It has a head, neck, body and tail • The head, neck and body are retroperitoneal • The head sits in the curve of the duodenum, the tail touches the spleen • The body sits behind the stomach

Answer 43

Exocrine function • Has cells that secrete enzymes and alkaline pancreatic juices • These cause the gallbladder to contract and release bile into the duodenum • Endocrine function • There is secretion of • Insulin –lowers blood glucose • Glucagon – raises blood glucose

the digestive system part 1 Flashcards

(67 cards)