week 10 - gastrointestinal system

Question 1

what is metabolism

Answer 1

sum of all chemical reactions in which energy is made available and consumed in the body

Question 2

what does the body need energy for

Answer 2

Contraction of muscles for all movement
Accumulation of ions and other molecules against concentration gradients (nerve impulse transmission)
Biosynthesis and hence for the building of tissues
Waste disposal and hence for getting rid of the end products of bodily function
Generation of heat and hence maintenance of body temp

Question 3

what is gibbs free energy and when is it positive and negative

Answer 3

it is usable energy or energy that is available to do work
deltaG = negative when the reaction gives out energy and is positive when the product contains more energy than the substrate

Question 4

describe the structure of ATP

Answer 4

adenosine tri-phosphate is composed of adenine, ribose and three phosphate groups
ADP is only two phosphate groups

Question 5

how is acetyl coenzyme A produced

Answer 5

glycolysis of glucose
beta-oxidation of fatty acids
transamination and oxidative deamination of amino acids
all of these reactions produce acetyl coA
vitamins and minerals play essential roles in these reactions

Question 6

what kind of process is the TCA cycle

Answer 6

amphibolic meaning it has anabolic and catabolic components

Question 7

steps of the TCA cycle

Answer 7

acetyl coA enters and condenses with oxaloacetate to produce citrate
decarboxylation phase - citrate is metabolised into succinyl coA (CO2 released)
reductive phase - succinyl coA to oxaloacetate
1 GTP produced
1 acetyl coA lead to 3 NADH and 1 FADH2 being produced

Question 8

steps of the electron transport chain

Answer 8

NADH and FADH2 donate two electrons and one proton
electrons are passed along RADOX centres which have an increasing affinity for electrons - electrons moving along produces ATP
ATP used to pump protons against conc gradient from matrix through the inner mitochondrial membrane to the intermembrane space
protons return to matrix through ATP synthase as IMM is impermeable
as protons are driven through, ATP synthase rotates and ATP is produced
electrons at end of complex 4 are donated to molecular O2 with a proton to produce water

Question 9

how are electrons passed between complexes in the ETC

Answer 9

As electrons reach end of RADOX centres in complex 1, they are passed via coenzyme Q to the next complex and so on… but from complex 3 to 4, cytochrome C passes electrons between complex

Question 10

why is complex 2 different (in ETC)

Answer 10

it is not pump proteins

FADH2 joins at this complex

Question 11

describe glycolysis

Answer 11

glucose is broken down to 2 pyruvate molecules in two phases
phase 1 - endergonic (2 ATP in) - glucose to glyceraldehyde-3-phosphate
phase 2 - exergonic - G-3-P is metabolised to pyruvate producing 4 ATP giving a net gain of 2 ATP
occurs in the cytosol

Question 12

how is pyruvate converted into acetyl coA

Answer 12

Pyruvate undergoes further metabolism in the mitochondria where, on entry, the 3C pyruvate loses a carbon atom with the production of CO2 to form acetyl CoA by the action of pyruvate dehydrogenase - A molecule of NADH is also formed in this process and that can be fed into the electron transport chain
Acetyl CoA is then able to enter the TCA cycle

Question 13

how is excess glucose stored in the body

Answer 13

in the form of glycogen mainly within the liver and also in muscle

Question 14

what are lipids

Answer 14

highly efficient energy storage molecules and are important to the body’s ability to adapt to periods of fasting
examples - fats, oils, waxes, certain vitamins (such as A, D, E and K), hormones and most of the cell membrane that is not made up of protein

Question 15

what are triglycerides and how can they be broken down

Answer 15

Fats are stored as triglycerides - triglycerides are three fatty acids attached to a glycerol backbone, these triglycerides can be broken down into their component parts of fatty acids and glycerol by an enzyme called lipase

Question 16

how are fatty acids transported in the blood

Answer 16

Fatty acids are released and transported in the blood as a complex with albumin and are taken up by other cells for oxidation
they are hydrophobic so are transported within albumin which protects them from water
All enzymes required for fatty acid catabolism are within matrix of mitochondria but fatty acids need to be modified by the addition of acetyl coA molecule in order to enter the mitochondria
beta-oxidation occurs once they enter they matrix

Question 17

describe fatty acid transportation into the mitochondrial matrix

Answer 17

addition of coA allows fatty acids to enter the mitochondria - forms fatty acyl coA
carnitine replaces coA to form fatty acyl carnitine - allowing it across the outer mitochondrial membrane
carnitine shuttle allows fatty acids to cross impermeable IMM into matrix
coA replaces carnitine to from fatty acyl coA and fatty acids can be degraded

Question 18

describe fatty acid degradation

Answer 18

once in the matrix, beta-oxidation can occur
this process cleaves carbon backbone between alpha and beta carbons making the fatty acid smaller and smaller
each cleavage produces acetyl coA, 1 NADH and 1 FADH2 which can be fed into ETC

Question 19

describe protein metabolism

Answer 19

transamination - removes amine group from AA and transfers it to an alpha ketoacid - when it accepts the amine group it transfers the keto group to the original AA
deamination - amine group removed from AA releasing the carbon backbone of the AA which can be regenerated into glucose, fatty acids or various TCA cycle intermediates - produces a side product of ammonium (toxic so kidneys exclude it)

Question 20

describe glucogenic and ketogenic amino acids

Answer 20

glucogenic - breakdown products ultimately form glucose by conversion to pyruvate, or intermediates of TCA cycle
ketogenic - breakdown products form fatty acids via the intermediates of acetyl coA or acetoacetyl coA

Question 21

sources of metabolic fuel in prolonged periods of starvation

Answer 21

fat - triglycerides in adipose tissue - sufficient to prolong life for 3 months
protein - provides approx. 14 days worth of energy but is spared for as long as possible to permit mobility

Question 22

why is the BMI not always a good representation of an individual

Answer 22

does not take into account muscle mass or cardiovascular condition

Question 23

factors influencing energy expenditure

Answer 23

menstruation, age, last three months of pregnancy and also lactation cause increase in expenditure

Question 24

components of a balanced diet and their functions

Answer 24

carbohydrate - energy source
protein - repair and growth
fat - long term energy store, insulation
vitamins - A: vision C: antioxidant D: Ca absorption
minerals - Ca: bone mineralisation Fe: oxygen transport
fibre - effective bowel function
water - hydration

Question 25

structure of triglycerides

Answer 25

glycerol and three fatty acids

Question 26

where is cholesterol found

Answer 26

present in plasma membrane of cells but also serves as a precursor for the synthesis of a number of other molecules such as sex hormones, oestrogen and testosterone as well as bile salts and phospholipids

Question 27

dietary sources for the components of a balanced diet

Answer 27

``` C - bread rice pasta potatoes p - meat fish dairy nuts fat - meat cheese cream fish v - A: sweet potato B: veg C: citrus D: oily fish m - Ca: milk Fe: red meat K: bananas f - plants ```

Question 28

essential amino acids

Answer 28

9 AAs that cannot be produced by the body and must be obtained by the diet

Question 29

types of carbohydrates and examples

Answer 29

monosaccharides - glucose, fructose, galactose disaccharides - sucrose, maltose, lactose polysaccharides - starch

Question 30

bonds between monosaccharides in poly and disaccharides

Answer 30

glycosidic bonds

Question 31

glands secreting saliva

Answer 31

parotid, submandibular and sublingual salivary glands

Question 32

function of saliva in digestion

Answer 32

starts the digestion of carbohydrates by producing an enzyme called alpha-amylase

Question 33

how alpha-amylase starts to digest carbohydrates

Answer 33

cleaves the 1-4 glycosidic bonds to produce maltose, a disaccharide, maltotriose, a trisaccharide and alpha limit dextrin

Question 34

digestion in the mouth

Answer 34

alpha amylase starts carb digestion Lingual lipase which breaks down triglycerides into fatty acids and glycerol is also present in saliva but most fat digestion takes place later in the small intestine

Question 35

digestion in the stomach

Answer 35

start of protein digestion

Question 36

secretion and activation going on in the stomach during digestion

Answer 36

chief cells secrete pepsinogen parietal cells secrete HCl acid which denatures proteins and activates pepsin pepsin then cleaves peptide bonds within the polypeptide chain to produce many smaller oligo peptides

Question 37

what is a zymogen

Answer 37

some enzymes are synthesised as inactive precursors - these inactive precursors are called zymogens

Question 38

exocrine function of the pancreas

Answer 38

pancreatic juice and alkali secretion | alkali secretions buffer any acid from the stomach and provide an optimal pH for. digestive enzymes in the duodenum

Question 39

endocrine function of the pancreas

Answer 39

secretion of insulin and glucagon

Question 40

function of the pancreatic secretions into the duodenum

Answer 40

Pancreatic secretions into the duodenum include a number of proteases such as trypsin and chymotrypsin and carboxypeptidase as well as other enzymes to digest elastin

Question 41

function of liver in digestion

Answer 41

production and secretion of bile

Question 42

role of bile in digestion

Answer 42

Stored in gallbladder and released into the duodenum after a meal Important in the emulsification of fat particles so that fats are accessible for enzymes Bile salts aid absorption of fats by forming complexes called micelles

Question 43

properties of bile that allows it to help emulsify fats

Answer 43

Cholesterol derived potion of bile acid is hydrophobic and the amino acid conjugate is hydrophilic - bile acids are amphipathic Due to these properties, bile salts have a detergent action of particles of dietary fat causing fat globules to break down or be emulsified into tiny droplets

Question 44

why fats are emulsified

Answer 44

greatly increases the surface area of fat making it available for the digestion by lipases

Question 45

what are enterocytes

Answer 45

cells of the intestinal lining

Question 46

digestive enzymes provided by the duodenum

Answer 46

first is enterokinase which activates trypsin which then goes and activates all the other proteolytic zymogens produced from pancreas Second group of enzymes are the brush border enzymes – digest disaccharides to monosaccharides

Question 47

describe the different types of absorption

Answer 47

passive absorption - from a high to low concentration facilitated transport - down concentration gradient - involves a membrane carrier active transport - uses energy and a membrane carrier - low to high

Question 48

what are micelles in digestion and how are they formed

Answer 48

mix of bile acids and lipids Products of lipid digestion are solubilised in the intestinal lumen in mixed micelles with the aid of bile salts except glycerol which is water-soluble

Question 49

describe how fatty acids are released into the bloodstream

Answer 49

Micelles diffuse to the apical brush border where the lipids are released from the micelle and diffuse down the concentration gradient into the cell Inside the cells, if the fatty acid chains are short they will move directly into bloodstream if larger, triglycerides are packaged into lipid structured called a chylomicron – secreted into lymphatics via lacteals – lymphatic circulation carries these chylomicrons to thoracic duct to enter the bloodstream

Question 50

absorption of monosaccharides

Answer 50

glucose and galactose absorbed by mechanisms involving sodium dependent co-transport – they move from the intestinal lumen into the cell on the sodium glucose transporter called SGLT1 Sodium is rapidly shuttled out in exchange for potassium by sodium pumps on the basolateral membrane Fructose is transported separately across both the apical and basolateral membranes by facilitated diffusion all three monosaccharides are transported across the basolateral membrane into the bloodstream by the GLUT2 transporter

Question 51

absorption of amino acids

Answer 51

Luminal plasma membrane of the absorptive cell has a number of sodium dependent amino acid transporters Di- and tri- Peptides in the small intestine are absorbed by Co-transport with hydrogen ions, then further digested into amino acids once inside the cell All the amino acids are then transported across the basolateral membrane into the blood by facilitated diffusion

Question 52

final products of protein digestion

Answer 52

amino acids, dipeptides and some tripeptides

Question 53

describe normal eating behaviour

Answer 53

normal eating is flexible it varies in response to your hunger, your schedule, your proximity to food and your feelings Usually having 3 meals a day Overeating and undereating at times

Question 54

common eating disorders

Answer 54

anorexia nervosa bulimia nervosa binge eating disorder avoidant/restrictive food intake disorder (ARFID) other feeding or eating disorders that do not fit into these categories

Question 55

presentation of bulimia

Answer 55

recurrent episodes of overeating binge eating accompanied by repeated inappropriate compensatory behaviours aimed at preventing weight gain individual is preoccupied with body shape or weight which strongly influences self evaluation not significantly underweight so does not meet AN criteria

Question 56

management of bulimia nervosa in adults

Answer 56

if self-help programme does not work, try CBT - involve significant others in CBT if appropriate

Question 57

management of bulimia nervosa in children and young people

Answer 57

family therapy or CBT if FT-BN does not work

Question 58

what is cognitive behavioural therapy

Answer 58

evidence based treatment for a range of mental health diagnoses talking therapy changes the way the patient thinks and behaves which is turn changes they way they feel

Question 59

presentation of binge eating disorder

Answer 59

``` Characterised by frequent recurrent episodes of binge eating (eg once a week or more over a period of several months) with compensatory behaviours Eating more quickly than usual Eating until uncomfortably full Eating a lot when not hungry Eating alone because of embarrassment Feeling very bad or guilty after eating ```

Question 60

management of binge eating disorder

Answer 60

guided self help with therapy sessions | if unsuccessful or unacceptable offer group eating disorder focused CBT-ED

Question 61

presentation of anorexia nervosa

Answer 61

A significantly low body weight for the individuals height, age and developmental stage (BMI less than 18.5, BMI under 5th percentile in children and adolescents) Low body weight is accompanied by a persistent pattern of behaviours to prevent the restoration of normal weight Low body weight is central to the person’s self-evaluation or is inaccurately perceived to be normal or excessive

Question 62

management of anorexia nervosa in adults

Answer 62

consider CBT-ED If CBT-ED, MANTRA or SSCM is unacceptable try one of the others or eating disorder focused focal psychodynamic therapy Individual CBT-ED should consist of up to 40 sessions over 40 weeks

Question 63

management of anorexia nervosa in children

Answer 63

Family therapy Give patient the option to have single and family sessions If FT-AN is unacceptable, contraindicated or ineffective consider CBT-ED or adolescent focused psychotherapy

Question 64

presentation of ARFID

Answer 64

Characterised by abnormal eating or feeling behaviours that result in the intake of insufficient quantity or variety of food - extreme picky eating Causes significant weight loss/failure to gain weight/nutritional deficiencies/ dependence on nutritional supplements or tube feeding/ negatively affects health/ significantly impairs functioning The pattern of eating does not reflect concerns about body shape or weight

Question 65

role of a psychiatrist in the MDT

Answer 65

works with the MDT in the following: Assessment and diagnosis Supporting psychologically informed formulation and treatment – finding the reason behind the ED Physical monitoring Risk assessment and management Treating comorbidities Developing services, improving quality, facilitating teaching and learning

Question 66

complications of anorexia

Answer 66

impaired concentration, dry skin, brittle hair, hair loss, low bp, cardiomyopathy, anaemia, osteoporosis, amenorrhoea, infertility

Question 67

2 groups of organs within the digestive system

Answer 67

gastrointestinal tract | accessory organs - salivary glands, gallbladder, liver, pancreas

Question 68

function of gall bladder in the digestive system

Answer 68

helps store and concentrate bile

Question 69

components of the GI tract

Answer 69

``` oral cavity pharynx oesophagus stomach small intestine large intestine ```

Question 70

parts of the small intestine

Answer 70

duodenum jejunum ileum as you move from the duodenum to the ileum you progress from more digestion to more absorption

Question 71

large intestine components

Answer 71

Caecum, ascending, transverse and descending colon, sigmoid colon, rectum and anus

Question 72

were is mucosa or mucous membrane found

Answer 72

lining the cavities of the body and surface of the internal organs

Question 73

what is lamina propria

Answer 73

thin layer of loose connective tissue which lies beneath the epithelium - it contains inflammatory cells and provides support and nutrients to the overlying epithelium

Question 74

what is muscularis mucosae

Answer 74

next layer deep to the lamina propria and is composed of smooth muscle and is continuous all the way through the entire length of the gastrointestinal tract

Question 75

describe the submucosa

Answer 75

is deep to the muscularis mucosae - composed of dense irregular connective tissue and contains many blood vessels, nerves and also lymphatic vessels (which collects additional fluid around the body outside the vasculature)

Question 76

describe the muscularis propria - also called the muscularis externa

Answer 76

comprised of inner circular muscle and outer longitudinal muscle - this muscle is smooth muscle and is responsible for peristalsis (movement of food and products of digestion)

Question 77

describe the adventitia

Answer 77

outer layer of fibrous connective tissue surrounding an organ

Question 78

describe the histology of the GI tract from deep to superior

Answer 78

``` Mucosa (mucous membrane) epithelium lamina propria muscularis mucosae submucosa muscularis propria (muscularis externa) adventita serosa ```

Question 79

epithelium in the GI tract

Answer 79

Oesophagus epithelium is stratified, squamous | Change of epithelium at stomach which continues for the rest of the GI tract – simple columnar

Question 80

function of brunners glands

Answer 80

secretes bicarbonate ions to neutralise acid from stomach

Question 81

what are peyers patches

Answer 81

lymphoid follicles and form part of the immune function preventing the growth of dangerous bacteria

Question 82

describe the pharynx and its three parts

Answer 82

conducts air muscles direct food to oesophagus made of the nasopharynx, oropharynx and laryngopharynx

Question 83

9 sections of the abdomen

Answer 83

``` 1 = Right hypochondrium 2 = Epigastric 3 = Left hypochondrium 4 = Right lumbar 5 = Umbilical 6 = Left lumbar 7 = Right iliac fossa 8 = Suprapubic 9 = Left iliac fossa ```

Question 84

organs in Right hypochondrium

Answer 84

liver

Question 85

organs in epigastric

Answer 85

Duodenum, liver, gall bladder, pancreas, stomach

Question 86

organs in the left hypochondrium

Answer 86

spleen and stomach

Question 87

organs in the right lumbar

Answer 87

ascending colon | kidney

Question 88

organs in the umbilical

Answer 88

Stomach, Head of pancreas, Small intestine (duodenum), transverse colon, lower aspects of right and left kidneys

Question 89

left lumbar organs

Answer 89

descending colon | left kidney

Question 90

right iliac fossa organs

Answer 90

caecum, appendix, part of ascending colon

Question 91

suprapubic organs

Answer 91

bladder, uterus, parts of small intestine

Question 92

left iliac fossa organs

Answer 92

sigmoid colon, descending colon

Question 93

where is the pyloric sphincter found and what is its function

Answer 93

in the pylorus of stomach | controls secretions to duodenum from stomach

Question 94

what is anterior/superior to stomach

Answer 94

diaphragm and liver

Question 95

posterior/inferior to stomach

Answer 95

Diaphragm, spleen, kidney (L.), adrenal gland, pancreas

Question 96

three layers of muscle in stomach wall

Answer 96

longitudinal, circular, oblique

Question 97

describe the histology of the stomach

Answer 97

Endocrine cells produce gastrin This stimulates the parietal cells to produce hydrochloric acid The hydrochloric acid then breaks down pepsinogen to become pepsin produced from the chief cells Mucous and surface mucous cells protect the mucosa

Question 98

what are villi

Answer 98

These are finger like projections and are well designed to increase surface area, and therefore aid in the digestion and absorption which typically happens in the small intestine, namely the duodenum, jejunum and ileum

Question 99

role of duodenum in digestion

Answer 99

receives chyme contains brunners glands bile and pancreatic secretions enter ends at duodenojejunal junction

Question 100

functions of the pancreas

Answer 100

exocrine - Primarily produces many digestive enzymes but also Bicarbonate ions - These digestive enzymes help break down carbohydrates, proteins and fats endocrine - islets of langerhans secrete insulin, glucagon and somatostatin

Question 101

functions of the hormones secreted by endocrine portion of pancreas

Answer 101

Insulin – promotes glucose absorption from blood into liver, skeletal muscle and fat cells - enables the conversion to glycogen (storage of glucose in this form) Glucagon – this does the opposite and results in the conversion of the stored glycogen into glucose for release into the bloodstream when levels are low Somatostatin – this helps to reduce acid secretion and helps to slow down the digestive process - has a variety of other functions in the body

Question 102

how many lobes does the liver have

Answer 102

four

Question 103

functions of liver

Answer 103

It detoxifies and processes everything absorbed from the gastrointestinal tract (GIT), and regulates glucose in the blood The liver synthesizes proteins including the clotting factors and platelet regulations It inactivates hormones and drugs, as well as insulin and many waste products and is heavily involved in drug metabolism, and sometimes this can be of detriment when the product of metabolism is more toxic than the initial compound e.g. paracetamol

Question 104

describe the blood supply for the liver

Answer 104

receives a dual supply of blood – the hepatic portal vein from the gut, spleen and related organs (approximately 75%) The hepatic arteries account for 25% of blood flow, and this artery provides the oxygenated blood for the liver

Question 105

functions of common hepatic duct and the cystic duct

Answer 105

duct that leaves gall bladder for bile secretions to pass out is called the cystic duct Common hepatic duct comes from the left and right hepatic ducts which carry bile to the gall bladder

Question 106

function of caecum

Answer 106

acts as a reservoir for chyme when it receives from the ileum

Question 107

four parts of the colon

Answer 107

ascending, transverse, descending and sigmoid

Question 108

where are the hepatic and splenic flexures

Answer 108

when colon meets the right lobe of the liver and turns 90 degrees = hepatic when colon turns another 90 degrees to point inferiorly = splenic flexure

Question 109

function of goblet cells

Answer 109

produce mucous as the role of the large intestine is to absorb fluid from the GI tract

Question 110

3 main vessels that all arise from the abdominal aorta and the areas they supply

Answer 110

Coeliac trunk (foregut) Superior mesenteric artery (midgut) Inferior mesenteric artery (hind gut) Foregut – supplies the oesophagus (lower portion), stomach, liver, spleen and first half of the duodenum Midgut – supplies the last half of the duodenum, jejunum, ileum, caecum, appendix, ascending colon and first half to first 2/3 of the transverse colon Hindgut – supplies last 1/3 of the transverse colon, descending colon, sigmoid colon and rectum

Question 111

describe the venous drainage of GI tract

Answer 111

Portal venous drainage is for the unpaired abdominal organs i.e. the gut and spleen Femoral veins drain the lower limb Internal iliac veins drain the pelvis Renal veins drain the kidneys Hepatic vein is the main vein draining the liver