Nutrition, Digestion + Absorption Flashcards
What is the jaw opening muscle?
Lateral pterygoid
What are the three pairs of jaw opening muscles?
Masseter
Temporalis
Medial pterygoid
What nerve are the jaw opening/closing muscles supplied by and where does it leave the skull?
CN V3
Pons via foramen ovale
What nerve supplies both the general and taste sensation for the posterior third of the tongue?
CN IX
What nerve supplies the anterior two thirds of the tongue for;
- General sensation
- Taste?
- CN V3
2. CN VII
What nerve supplies the superior gingiva and palate?
CN V2 (general sensation)
What nerve supplies the inferior gingiva and floor of the mouth?
CN V3
What nerves are involved in the gag reflex?
Sensory - CN IX
Motor - CN IX + CN X
What is the name of the branch of CN VII that supplies taste to the anterior two thirds of the tongue?
Chorda tympani
What nerve supplies the parotid glands and what fibres does it carry?
CN IX
Parasympathetic secretomotor
What is the only voluntary part of swallowing?
Tongue pushing food to oropharynx
What are the four extrinsic skeletal tongue muscles?
Palatoglossus
Styloglossus
Hyoglossus
Genioglossus
What is the role of the;
- Extrinsic tongue muscles
- Intrinsic tongue muscles?
- Suspend tongue and move it
2. Modify tongue shape
Where are the four pairs of intrinsic tongue muscle located?
Dorsally
Posterior lay
What nerve supplies all but one tongue muscle? What is the muscle not supplied by this nerve?
CN XII
Palatoglossus
What nerves supply the inner longitudinal pharyngeal muscles?
CN IX
CN X
What is the role of the inner longitudinal pharyngeal muscles?
Contract to shorten pharynx
Raise larynx
What are the three parts of the outer circular constrictor pharyngeal muscles?
Superior
Middle
Inferior
What nerve supplies the outer pharyngeal muscles?
CN X
At what vertebral level is the upper oesophageal sphincter?
C6
Where does the oesophageal plexus run, what does it supply and what does it do?
Along the surface of the Oesophagus
Supplies smooth muscle distally
Has PNS and SNS fibres - Influences peristalsis
Where are the oesophageal constrictions?
Cricopharyngeus muscle - Cervical
Aortic arch and left main bronchus - Thoracic
Diaphragm
The contraction of the diaphragm, higher intra-abdominal pressure than intragastric and oblique oesophageal entry create what?
Physiological lower oesophageal sphincter
What organs form the foregut?
Oesophagus to mid-duodenum Liver Gallbladder Spleen Half of pancreas
What are the midgut organs?
Mid-duodenum to proximal 2/3 of transverse colon
Remaining half of pancreas
What are the foregut organs?
Distal 1/3 of transverse colon to proximal half of anal canal
What causes peritonitis?
Peritoneum filling with
- Blood
- Puss
- Faeces
Where does the portal triad lie?
Free edge of the lesser omentum
Where is the needle inserted in abdominocentesis and why is it inserted there?
Lateral to rectus sheath
To avoid inferior epigastric artery
Where do the abdominal sympathetic nerves leave the spinal cord?
T5-L2
What is the route of the sympathetic nerves from the spinal cord?
Enter bilateral sympathetic chains
Do not synapse
Leave in abdominopelvic splanchnic nerves
Synapse at prevertebral ganglia - anterior to aorta
Where are the prevertebral ganglia located?
At major aortic branches
How do the sympathetic fibres reach the organs?
In periarterial plexuses
Where do the sympathetic nerves supplying the adrenal gland leave the spinal cord?
T10-L1
How do parasympathetic fibres reach the gut organs?
Vagus nerve travels on Oesophagus
Travels into periarterial plexuses
Synapses on ganglia in the organs walls
Pelvic splanchnic nerves
- S2, S3 + S4 - supply hind gut
Where do visceral afferent signals from organs enter the spinal cord?
Alongside SNS fibres
Foregut - T6-T9
Midgut - T8-T12
Hindgut - T10-L2
Where and how is bilirubin formed?
Spleen
Haemolysis
What is the gallbladders role with bile?
Storage
Concentration
What is the role of bile?
Fat absorption
At what vertebral level does the coeliac trunk arise?
T12
What are the three branches of the coeliac trunk?
Splenic artery
Hepatic artery
Left gastric artery
Which ribs protect the spleen?
9-11
What is the blood supply to the stomach?
Along lesser curvature
- Right gastric artery (branch of hepatic artery)
- Left gastric artery
Along greater curvature
- Right gastro-omental artery (branch of gastroduodenal which is a branch of common hepatic artery)
- Left gastro-omental artery (branch of splenic artery)
What is the blood supply to the liver?
Hepatic artery branches into right and left hepatic arteries - 20-25%
Hepatic portal vein - 80% of blood supply
What ribs protect the liver?
7-11
What are the four anatomical segments of the liver?
Right lobe
Left lobe
Caudate lobe
Quad rate lobe
What is the venous drainage of the liver via?
Three main hepatic veins
What two recesses are created by the liver?
Hepatorenal - Lowest cavity when supine (pus collection)
Subphrenic
What is the venous drainage of the GI tract?
Foregut - Splenic vein to HPV Hindgut - Inferior mesenteric vein to splenic vein Midgut - Superior mesenteric vein to HPV
What does the neck of the gallbladder narrow to become?
Cystic duct
What is the blood supply of the gallbladder?
Cystic artery - branch of right hepatic artery
What are the four main layers of the GI tract wall?
Mucosa
Submucosa
Muscularis externa
Serosa
What are the three components of the mucosa?
Epithelium - With exocrine cells - Endocrine glands Lamina propria Muscularis mucosa
What are the roles of the muscle layers in the GI tract wall?
Muscularis externa - Circular - narrows and lengthens lumen - Longitudinal - shortens and widens lumen Muscularis mucosa - Changes absorptive and secretory areas
What are the names of the pacemaker cells in the ENS?
Interstitial cells of Cajal
Why does the frequency of slow waves and hence smooth muscle contractions increase as we move distally along the tract?
Favours retention of contents
What effect does PNS stimulation have on the gut?
Increased secretions
Increased GI blood flow
Increased peristalsis
Sphincter relaxation
What effect does SNS stimulation have on the gut?
Decreased motility
Decreased secretions
Decreased blood flow
What happens if food sticks in the Oesophagus?
A second peristaltic wave is triggered
- Stronger
- Locally triggered
Increased saliva production
Each of these statements describes a polymer of glucose. Name the polymer they describe.
- Straight chain with alpha-1,4 links only
- Branched chain every 24-30 monomers with alpha-1,4 and alpha-1,6 linkages
- Branched chain every 8-12 monomers with alpha-1,4 and alpha-1,6 linkages with a protein core
- Amylose
- Amylopectin
- Glycogen (core is glycogenin)
What links and monomers are present in sucrose and lactose?
Sucrose - Alpha-1,2 - Glucose and fructose Lactose - Beta-1,4 - Glucose and galactose
This enzyme can break alpha-1,4 links but not
- Terminal links
- Links adjacent to alpha-1,6 links
Amylase
What oligomers does amylase produce?
Maltotriose
Maltose
Alpha-limit dextrins
What is the role of maltase?
Degrades terminal alpha-1,4 links
What is the role of isomaltase?
Splits alpha-1,6 branches
Why are the symptoms of lactose intolerance/lactase insufficiency?
Bloating
Abdominal pain
Flatulence
What are three examples of endopeptidases?
Trypsin
Chymotrypsin
Elastase
What do endopeptidases produce?
Oligopeptides
What are some examples of exopeptidases?
Procarboxypeptidase A
Procarboxypeptidase B
What do exopeptidases produce?
Single amino acids
What is the role of bile salts in fat digestion?
Emulsify large droplets to smaller droplets
Increases surface area for lipase action
What is steatorrhoea?
Fat in faeces
Due to lipid malabsorption
What problem arises due to bile salt action and how is it overcome?
Bile salts block enzyme access to lipid core
Colipase - Amphipathic - Binds to bile salts and lipase for access to core
What happens to absorbed fats?
Short and medium chains - Diffuse through - Exit basolateral membrane - Enter villus capillaries Long chains and monoglycerides - Resynthesised into triglycerides - Incorporated into chylomicrons
How are amino acids absorbed?
Brush border - 5 Sodium-dependent co-transporters - 2 Sodium-independent Basolateral membrane - 3 efflux - Na-independent - 2 influx - for enterocyte nutrition - Na-dependent
How are glucose and galactose absorbed?
SGLT1 mediated
- Hexose in D-conformation
- Able to form a pyranose ring
- Requires 2Na+ binding
How is fructose absorbed?
GLUT5
How do monosaccharides exit the basolateral membrane?
GLUT2 - facilitated diffusion
What vitamins are water soluble?
B vitamins (not B12)
Vitamin C
Vitamin H
What cancers does obesity increase the risk of?
Uterus (endometrial) Breast (post-menopausal) Prostate Colon Oesophageal Kidney Gallbladder
What satiation signals exists to reduce our food intake?
Cholecystokinin (CCK) Peptide YY Glucagon-like Peptide 1 Oxyntomodulim Obestatin
What is the role of Ghrelin?
A hunger signal
Increases food intake via the hypothalamus
Decreases fat use
What is the only currently used drug for obesity?
Orlistat
What treatment for obesity is associated with a high level of type 2 diabetes resolution?
Bariatric surgery - gastric bypass
What patient features suggest they are in need of nutritional support?
BMI 5% weight loss
No eating for >5 days
Poor absorption/high nutrient loss
What are the three salivary glands?
Parotid
Submandibular
Sublingual
What are the two stages of saliva secretion?
Primary secretion
- By the acinus
Secondary modification
- By duct cells
What affect does PNS stimulation have on the composition of saliva?
Large volume
Watery
Enzyme rich
(M3 mediated)
What effect does SNS stimulation have on the composition of saliva?
Small volume
Thick
Mucus rich
(B1 mediated)
What cells are present in the pyloric gland area and what do they secrete?
D cells - somatostatin
G cells - gastrin
What cells are present in the oxyntic mucosa (fundus and body) and what do they secrete?
Chief cells - pepsinogen
Enterochromaffin-like cells - histamine
Parietal cells - HCl and intrinsic factor
What is the role of HCl in the stomach?
Activates pepsinogen to pepsin
Denatures protein
What is the role of intrinsic factor?
Binds Vit B12
Allows its absorption in terminal ileum
Lack of intrinsic factor - pernicious anaemia
What is the purpose of histamine in the gut?
Stimulates HCl secretion
What are the roles of gastrin and somatostatin?
Gastrin - stimulates HCl release
Somatostatin - inhibits HCl release
How is histamine release stimulated from the ECL cells?
Via gastrin
Via ACh from postganglionic PNS
How does somatostatin work?
Inhibits gastrin release between meals
What receptors are present on the parietal cell?
M3 ACh receptor - stimulates HCl release
Gastrin receptor - stimulates HCl release
H2 receptor - stimulates HCl release
PGE2 receptor - inhibits all three of the above - inhibits HCl release
What drug classes influence acid secretion (give examples)?
Muscarinic receptor antagonists - Pirenzepine
Proton pump inhibitors - Omeprazole
H2 receptor antagonist - Ranitidine
NSAIDs - Block COX-1 - Inhibits PGE2 production
What are sucralfate and bismuth chelate examples of?
Mucosal strengtheners
Bind to ulcer base
Increase mucus, bicarbonate and PGE2 production
Why are aluminium hydroxide and magnesium hydroxide used together as antacids?
Aluminium - constipation
Magnesium - diarrhoea
What are side effects of sodium hydroxide and calcium hydroxide?
Sodium - Hypertension
Calcium - Gastrin release
What are the cutaneous stigma of liver disease?
Spider naevi Palmar erythema Clubbing Hair loss Jaundice
What other symptoms are present in liver disease?
Gross gut oedema and ascites
CCF
What receptors are expressed more in alcoholics and why is this a problem?
CYP2E1
Once paracetamol is given, it is rapidly metabolised to N-Acetyl-p-benzoquinonamine (NAPQI)
This is toxic
What is the role of peyers patches in the gut?
Antigen capture
Initiation of immune response
What are the two methods of antigen capture in the gut?
Via Peyer’s patches
Across epithelium - dendritic cells extend processes
What part of the mucosa is the immune response effector?
Lamina propria
What special cells are contained in Peyer’s patches and what is their function?
M cells
- Take up antigen
- Release it at basal surface for dendritic cells
What is the main immunoglobulin involved in GALT?
IgA
What can IgA do in the mucosa?
Bind and neutralise pathogens and toxins
Bind and neutralise antigens in the epithelium
Transport antigens from lamina propria during secretion
What process occurs in a non-inflammatory gut?
Commensals produce
- PGE2
- TGFbeta
- TSLP
- —-Inhibits dendritic cell maturation - Regulatory Th3 cells form
What T cells form in an inflammatory gut?
Effector Th1 and Th2 cells
What are the extra intestinal features of Ulcerative Colitis?
Arthritis Uveitis Skin lesions Mouth ulcers Erythema nodosum Clubbing
How can Crohn’s disease and UC be treated?
Steroids
Azathioprine
Cyclosporin
Methotrexate
How can intestinal failure be caused?
Obstruction Dysmotility Resection Congenital defect Disease
How can the three types of intestinal failure be described?
- Self limiting, short term post-op
- Prolonged, sepsis
- Chronic and stable
What is the treatment of choice for Type 3 IF?
Home Parenteral Nutrition
What is the definition of a hernia?
Abnormal protrusion of a viscus outwith its normal cavity
A thin elderly woman notes a lump in her groin. She has complained of a decrease in defecation. She has no history of abdominal surgery. What type of hernia is this most likely to be?
Femoral
A 45 year old man comes in with a lump than has increased his groin crease. The lump is more prominent when he stands and when he coughs. The man has a chronic cough and is obese. The lump is above the pubic tubercle. What type of hernia is this?
Inguinal hernia
Congenital linea alba weakness predisposes to which type of hernia?
Epigastric hernia
A patient with a lump in his groin presents. You apply pressure over the deep inguinal ring and ask the patient to cough. You find that the lump is reduced. Is it direct or indirect?
Indirect
