W8- Lecture 39- Digestive system

Question 1

what are the components of the digestive system ?

Answer 1

Mouth
Pharynx
Oesophagus
Stomach
Intestines
Anus

Question 2

what are the accessory organs that are not in the digestive tract, but help in digestion?
+ function

Answer 2

Liver-Bile production; storage
Gall bladder-Stores & concentrates bile
Pancreas-Exocrine cells (fluid & enzymes), endocrine cells (hormones)
Salivary glands-Lubricating fluid & enzymes

Question 3

describe the function related to structure of the mouth in the digestive system

Answer 3

Secretion of salivary amylase (breaks down carbohydrates)
Lingual lipase begins the breakdown of fat into smaller fat molecules.
Highly muscular tongue
Manipulates food for mastication (bolus)
Surface of tongue covered with lingual papillae:
Filiform (most numerous)
Fungiform
Circumvallate
Foliate

Question 4

the surface of tongue covered with lingual papillae name the 4 types

Answer 4

Filiform (most numerous)
Fungiform
Circumvallate
Foliate

Question 5

which three transport passages make up the digestive system

Answer 5

Pharynx
Oesophagus
Anal canal

Question 6

what cells line the digestive transport passages ?

Answer 6

Lined with stratified squamous epithelium

Some mucous glands for lubrication

Question 7

describe the structure of the oesophagus

Answer 7

Approximately 25cm long
Lined with mucosa
Stratified squamous epithelium Columnar epithelium
Well defined lamina propria + muscularised mucosae.
Peristalsis propels food and water into stomach

Tough stratified epithelium without keratin
Squamous mucosa
Submucuosal glands secrete fluid into the difestive tract where they serve a variety of protective functions.
Circular layer and muscularis externa provides peristaltic contractions
Longitudinal layer plays a role in the physiology of motor function

Question 8

what are the 4 layers of the alimentary tract

Answer 8

mucosa
submucosa
muscularis externa
serosa/adventitia (most lateral)

Question 9

describe the mucosa layer of the alimentary tract

Answer 9

contains both epithelia and lamina propria
Epithelium
Mainly columnar epithelial cells
Glandular secretions moisten surface

Lamina propria
Composed of loose connective tissue
Contains small blood vessels, lymphatics, nerve fibres
Other specialist cells (macrophages and lymphocytes)

Question 10

describe the submuscosa layer of the alimentary tract

Answer 10

Separates mucosa from underlying muscle layers

Regulates contractions + glandular secretions

Submucosal plexus (meissnr’s plexus)

Question 11

describe the MUSCUALRIS EXTERNA layer of the alimentary tract

Answer 11

Smooth muscle (two layers
Inner: circular layer
Outer: longitudinal 

Layers allow peristaltic contractions

Second nerve plexus located between muscular layers – myenteric (Auerbach’s) plexus

Question 12

describe the outermost layer: ADVENTITIA layer of the alimentary tract

Answer 12

Made of fibrous connective tissue

layers structure determined by the surrounding tissues

Question 13

describe the structure of the stomach

+ 4 anatomical regions

Answer 13

Digestive organ + reservoir.
Inner folds (rugae) increase surface area)
Food is mixed with gastric juices, hydrochloric acid and enzymes (pepsin)

Mucosa
Muscularis mucosae – circular and longitudinal muscle fibres

Muscularis externa
Three layers (oblique, circular, longitudinal)

Four anatomical regions:
Cardia
Fundus
Corpus (body)
Pylorus

Question 14

if pepsin breaks down proteins and the stomach is made out of protein why is it not broken down?

Answer 14

Mucus secreted by stomach cells (foveolar cells) protects the stomach lining.

Question 15

label the stomach

Answer 15

did you find
1- Cardia
2- Cardiac notch
3- Fundus
4- Body
5- Pylorus
6- 1st part of duodenum

Question 16

what are the three subdivisions of the small intestine

Answer 16

Duodenum
Jejunum
Ileum

Question 17

describe the mucosa in the small intestine

Answer 17

Plicae and villi
Increase surface area approximately 3x
Permanent structures (don’t change with distension
Absent from start of duodenum

Intestinal villi – entire intestinal mucosa
Increase surface area approx. 10x
Main cell type: enterocytes (have absorptive function

Microvilli on enterocytes
Increase surface area approx. 20x

Question 18

what is absorbed in the large intestine ?

+ three main sections

Answer 18

Reabsorption of water and inorganic salts

Three main sections
Caecum (inc appendix)
Colon (ascending, transverse, descending, sigmoid)
Rectum (inc anal canal)

Question 19

describe the mucosa layer of the large intestine ?

Answer 19

Smooth surface
Neither plicae nor villi
Goblet cells-More numerous than in small intestine

Question 20

what are the two types of waste excreted by the digestive system

Answer 20

Two types of waste:
Solid waste – from the digestive system in the form of faeces.
Metabolic wastes – produced by chemical reactions like respiration, hydrolysis, synthesis and neutralization:

Question 21

what is a Hiatal hernia?

Answer 21

Protrusion of stomach into the mediastinum through the oesophageal hiatus of the diaphragm.
Caused by weakened muscle tissue or excessive pressure
Can cause heartburn
Chest pain
Shortness of breath

Question 22

what are Gastric ulcers?

+main cause

Answer 22

Lesions in stomach lining

Caused mainly by the bacterium helicobacter pylori

Question 23

name the 5 types of salivary glands

Answer 23

Lingual
Labial
Buccal
Molar
Palatine

Question 24

where are salivary glands situated ?

Answer 24

Situated in submucosa of oral cavity + tongue

Question 25

name three of the large salivary glands | +Location

Answer 25

Sublingual Beneath tongue Many ducts Submandibular Floor of mouth Along inner surface of mandible Ducts behind teeth Parotid Largest, empties into mouth at the second molar

Question 26

what are the functions of The liver?

Answer 26

Filter the blood coming from the digestive tract before passing it to the rest of the body. Detoxifies chemicals and metabolizes drugs. The liver makes bile and removes toxin.

Question 27

describe the surface anatomy of the | lover

Answer 27

The liver is the largest internal organ (1.2-1.5kg) and is situated in the right hypochondrium. The liver lies mainly in the right upper quadrant of the abdomen. It is protected by the thoracic ribs (7-11) and the diaphragm.

Question 28

describe the divisions of the liver

Answer 28

A functional division into the larger right lobe (containing caudate and quadrate lobes) and the left lobe is made by the middle hepatic vein. The liver is further divided into 8 segments, by divisions of the right, middle, and left hepatic veins. Each segment has its own portal pedicle, permitting individual segment resection at surgery. functional lobules separated to each other by a septum.

Question 29

describe the flow of bile in the liver

Answer 29

Bile canaliculi collects the bile produced by hepatocytes and drains it into the bile duct. Bile passes from the liver via the biliary ducts – right and left – that join to form the common hepatic duct which unites with the cystic duct to form the common bile duct. Bile aids in the digestion of lipids.

Question 30

describe movement of blood in the liver

Answer 30

The hepatic blood supply constitutes 25% of resting cardiac output and is delivered via two main vessels, entering via the liver hilum (porta hepatis): The hepatic artery, a branch of the coeliac axis. The portal vein, drains most of the GI tract and spleen.

Question 31

explain the actions of each of these functions of the liver 1digestion 2metabolic & synthesis 3detoxification

Answer 31

1Synthesis of bile salts Conjugation and excretion of bile pigment (bilirubin) Glucose metabolism (regulation of blood sugar) Conversion of blood glucose to glycogen and fat Production of glucose from glycogen and other molecules by gluconeogenesis Secretion of glucose into blood 2Fat metabolism Synthesis of triglycerides and cholesterol, excretion of cholesterol in bile, and production of ketone bodies from fatty acids. 3Protein metabolism Production of albumin, plasma transport proteins, clotting factors. Phagocytosis by Kupffer cells Chemical alteration of biologically active molecules (hormones and drugs) Production of urea, uric acid and other compounds that are less toxic than the parent compound.

Question 32

what is the composition of bile? produced by ? + exporting

Answer 32

Bile composition Organic: bilirubin Inorganic: bile salts Produced by hepatocytes Passes into bile canaliculi Canaliculi carry bile to bile duct Over production may result in Jaundice.

Question 33

what is jaundice ? | causes?

Answer 33

Skin, eyes and mucous membranes turn yellow due to high level of bilirubin, a yellow-orange bile pigment. Many causes: Hepatitis, liver disease, pancreatitis, gallstones and tumors, sickle cell disease.

Question 34

how is bile secreted ?

Answer 34

Terminal bile ducts Lined with cuboidal epithelium Intrahepatic bile ducts Coalesce into left + right hepatic ducts Unite to form common hepatic duct Columnar epithelium ``` Cystic duct (to/from gallbladder) Common bile duct (to duodenum) ```

Question 35

describe the function of the gall bladder

Answer 35

Concentrates and stores bile H2O and ions absorbed by mucosa Receives watery bile from hepatic duct Contraction of muscularis layer empties thick, concentrated bile into common bile duct and into small intestine. When small intestine is empty, sphincter of Oddi closes.

Question 36

what are gall stones ?

Answer 36

Gallstones are cholesterol that have crystallised within the gall bladder.

Question 37

what is the impact of Cholecystokinin(CCK) on bile

Answer 37

CCK from the duodenum triggers dilation of the hepatopancreatic sphincter and contraction of the gallbladder bile is ejected into the duodenum through the duodenal ampulla

Question 38

describe the endo and exocrine functions of the pancreas

Answer 38

Exocrine: Acini cells are clusters surrounding ducts responsible for secreting digestive enzymes. Endocrine: Islets of Langerhans There are 3 major types of cells in an islet: Alpha cells make glucagon, which raises the level of glucose (sugar) in the blood Beta cells make insulin delta cells make somatostatin which inhibits the release of numerous other hormones in the body

Question 39

what is gastritis? main cause what else gastritis can lead to

Answer 39

Gastritis indicates inflammation associated with mucosal injury of the stomach Helicobacter pylori (H. Pylori) infection is the most common cause of gastritis. Chronic inflammation can lad to gastric intestinal metaplasia, a precursor to gastric cancer.

Question 40

how does H. Pylori infection lead to cancer ?

Answer 40

H. Pylori infection causes chronic gastritis, which eventually leads to atrophic gastritis and pre-malignant intestinal metaplasia

Question 41

what are the two major types of gastric cancer ?

Answer 41

Intestinal (type 1) – Intestinal metaplasia is seen in the surrounding mucosa, often with H. pylori. This type is more likely to involve the distal stomach and occur in patients with atrophic gastritis. Diffuse (type 2) – It may involve any part of the stomach, especially the cardia, and has a worse prognosis than intestinal type. Loss of expression of the cell adhesion molecule, E-cadherin, is the key event in the carcinogenesis of diffuse gastric cancers.

Question 42

what are the two major types of Inflammatory bowel disease

Answer 42

``` Two major forms of IBD are recognised: Crohn’s disease (CD) which can affect any part of the gastrointestinal tract. Ulcerative colitis (UC) which affects only the colon. ``` There is a degree of overlap between these two conditions and in 10% of cases of IBD it is termed colitis of undetermined type.

Question 43

what are the clinical feastures of crohn's disease

Answer 43

Major symptoms are diarrhoea, abdominal pain and weight loss. Approximately 50% of patients will require an intestinal resection within 5 years of diagnosis. CD can also present as an emergency with acute right iliac fossa pain mimicking appendicitis.

Question 44

how can you investigate crohn's disease ?

Answer 44

Stool test: including Clostridium difficile (c. dofficile) toxin assay should be performed. Blood tests: Anaemia Raised ESR and CRP Hypoalbuminaemia: present in severe disease as part of an acute phase response to inflammation associated with raise CRP.

Question 45

how can you manage crohn's disease ?

Answer 45

Oral prednisolone used to induce remission of CD. Antibiotics are used for treating secondary complications of CD (abscess and perianal disease). Anti-TNF agents are used for maintenance of remission.

Question 46

what are the clinical features of Ulcerative colitis (UC)?

Answer 46

The major symptom in UC is diarrhoea with blood and mucus, accompanied by lower abdominal discomfort. General features are malaise, lethargy and anorexia. Toxic megacolon is a serious complication associated with acute severe colitis. The X-ray shows a dilated, thin walled colon with a diameter of >6cm.

Question 47

how can you investigate Ulcerative colitis (UC)?

Answer 47

Colonoscopy Blood tests: White cell and platelet counts are raised in moderate to severe attacks. ESR and CRP are often raised. pANCA* may be positive (this is in contrast to CD where pANCA is usually negative.

Question 48

how can you manage Ulcerative colitis (UC)?

Answer 48

Main treatment is aminosalicylate. | Aminosalicylate delivers 5-ASA (aminosalicyclic acid), which is absorbed in the small intestine.

Question 49

what is Gastroesophageal reflux disease

Answer 49

GERD happens when the oesophagus does not close properly. Thus allows stomach contents to reflux into the oesophagus. GERD is a chronic condition of mucosal damage caused by stomach acid coming up from the stomach into the oesophagus

Question 50

what are the causes for Gastroesophageal reflux disease?

Answer 50

Caused by changes in the abnormal relaxation of the lower oesophageal sphincter due to oesophagitis, oesophageal spasm or a hiatal hernia.

Question 51

what is Splenomegaly?

Answer 51

``` enlargement of the spleen Granulocytic leukaemia (high leukocyte and white blood cell count) may enlarge spleen 10x. ``` Spleen (which is not normally palpable) can be palpated below the left costal margin when it is enlarged >3x. Splenectomy (removal of spleen) may be lifesaving.