Nutrition Flashcards
Fat-soluble vitamins
ADEK (can be stored)
Water-soluble vitamins
B1,2,3,6,9,12, C. Co-enzymes/co-factors.
Vitamin A
Retinoic acid. Binds to proteins in the retina so that visual pigments can be formed. Can bind to nuclear DNA and affect gene expression and processed like differentiation e.g. the formation of immune cells.
Deficiency = night blindness (mild) or metaplasia and keratinised conjunctive epithelium so a thicker cornea, and weak immune system.
Vitamin D
Active forms are D2, D3. Regulates plasma calcium, calcitonin and parathyroid hormone. Promotes bone turnover and mineralisation.
Deficiency = weak bones, rickets, osteomalacia
Vitamin E
Antioxidant and cell signalling. Other antioxidants in the body so deficiency isn’t a problem.
Vitamin K
Needed for vitamin K dependent coagulation factors. Modifies proteins after they’ve been made e.g. it carboxylates glutamate.
Deficiency = Haemorraghic diseases. Many drugs e.g. warfarin are vitamin K antagonists.
Vitamin B1
Thiamine. Involved in ATP synthesis pathway, Myelin, acetylcholine neurotransmitter, Cl- channels, glycolysis pathway.
Deficiency = weakness and stiffness.
Vitamin B2
Riboflavin e.g. FAD. e- /H+ carrier in the electron transport chain/for oxidation and reduction. Synthesised by a bacteria in the body and recycled so deficiency is uncommon.
Vitamin B3
Niacin. NAD precursor. Synthesised from a dietary aas so if deficient in this then deficient in B3.
Vitamin B6
Involved in transamination and aas regulation.
Vitamin B9 / B12
Folate and B12. Carbon carrier co-enzymes, needed for many pathways e.g. making ATP or myelin.
Deficiency = anaemia (macrocytic). Babies v sensitive to B9 deficiency so pregnant women given supplements.
Vitamin C
Ascorbic acid. Antioxidant and reducing sugar. Needed for iron uptake and absorption, collagen maintenance and synthesis of neurotransmitters.
Oral signs of vitamin deficiencies
Vitamin B2,3,6 = angular chelitis
B2 = magenta tounge
B3,6,9,12 = glottitis
C = spongy, bleeding gums.
Control mechanisms for the GI tracts
ANS - parasympathetic
Enteric nervous system
Gut peptide - eteroendocrine cells
ENS
a separate nervous system for GI tract, inner is the submucosal plexus and outer is myenteric. Short fibres (local circuits) detect intrinsic stimuli e.g. chyme in the stomach, extrinsic stimuli e.g. smell detected by long fibres (NAS, ENS).
A gut peptide control mechanism for the GI tract
Eteroendocrine cells release paracrine hormones and neurotransmitters that are stimulated by internal stimuli e.g. pH, and act via negative feedback mechanisms e.g. are released in response to a stimulus but act to reduce that stimulus and therefore aren’t stimulated as much.
Phases of deglutination
oral phase, pharyngeal phase, oesophageal phase
The 4 regions of the stomach and the openings
Openings = oesophageal and duodenum Regions = cardia, fungus, body, pylorus
Gastric functions
Motility - alternative relaxing and tensing of longitudinal and circular muscles. Compartmentalising so processing have time to completely finish. Trituration so food can be broken down and dissolve and mix.
Digest food
Absorb alcohol and fat-soluble drugs
Protect against bacteria via the lining and HCL and mechanisms (lining also protects against self-digestion)
Trituration
Motility of the stomach to allow the food to be mixed, ground down and dissolved.
Constituents of gastric juice
HCL, water, mucus
Pepsin and pepsinogen to make it (enzyme)
Intrinsic factor and glycoproteins (B12 digestion)
Gastric Glands
Cardiac, pyloric, oxyntic.
Cells that release the constituents of gastric juice
Duct neck cells = water and mucus
Parietal cells = HCL and intrinsic factor
Chief cells = pepsinogen
Endocrine cells = regulate acid secretion e.g. G cells release gastrin which stimulates acid secretion. D-cells release somatostatin which inhibits acid secretion.
The role of gastrin
Stimulates/increases acid secretion.
Somatostatin’s role
Inhibits secretion of acid from parietal cells.
How does food move through the stomach
Food presence stimulates fungus and body to relax to make more space. Contraction of the middle of body forces chyle down to the atrium and pylorus. Contractions in the atrium (systole) push chyle back up to mix and grind food. Some chyle moves to the duodenum and this inhibits motility in the stomach so that it starts to relax.
Phases of gastric mobility
Cephalic phase - Parasympathetic CNS reacts to smell/sight/etc = increased stomach motility and mucus and HCL and enzymes.
Gastric phase - food triggers peristalsis and release of gastrin which increases motility and secretions.
Intestinal phase - chyle in duodenum inhibits motility in the stomach to slow it down.
What is peristalsis
Contraction of muscles
Retropulsion in the stomach
Atrial systole pushed chyle back into the stomach so it can be broken up more.
Retropulsion in the stomach
Atrial systole pushed chyle back into the stomach so it can be broken up more.
Pancreas secretions
Acinar cells secrete enzymes that digest lipids, proteins, sugars, etc and then intercalated duct cells add water and ions (carboxylates/alkaline)
Duodenal feedback
Nutrients in food –> CCK –> more enzymes secreted
HCL in chyme –> Secretin –> more ions and water
(from pancreas)
Gallbladder functions
Concentrate the bile.
Neutralise the alkaline by adding H+ ions.
Store the bile
Secrete it in a controlled way.
The liver synthesises and functions
Liver secretions contain bile, bilirubin, proteins to protect against infection and alkaline ions.
Functions are to remove waste e.g. cholesterol, to maintain a pH and aid digestion of lipids via emulsification.
CCK actions
Causes more enzymes to be secreted from the pancreas in response to nutrients being detected in the chyme. It contracts the gallbladder and relaxes the sphincter of Oddi so that bile can be secreted.
Secretin actions
Makes the pancreas secrete more alkaline ions in response to HCL in the chyme. Stimulates the gallbladder to secrete bile.
How is bile delivery from the gall bladder controlled
Secretin stimulates the gallbladder to secrete bile and CCK relaxes the sphincter of Oddi and starts contractions so bile can be secreted.
Gallstones
When the balance of components and regulatory systems are off, calcified cholesterol, calcium and bilirubin in the gallbladder. V painful and can cause inflammation and infections.
Regions of the small intestines
Duodenum, jejunum, ilium.
What is the unstirred layer
Glycocalyx layer, where substances can sit so they can be absorbed.
How are carbs absorbed into the small intestines
Glucose and galactose move into the cells by co-transport, carried by a Na+ ion that moves in due to a concentration gradient, created by Na+ ions being actively transported out of the cells. Fructose moves in by facilitated diffusion, and all move into the blood by facilitated diffusion.
How are proteins absorbed into the small intestines
Large peptides are broken down by peptidase into aas and small peptides, and then actively transported into the cells. Small peptides get broken down by intracellular protease, into aas. The aas move into the blood by diffusion.
Lipid absorption out of the intestine lumen
Lipids are broken down by enzymes and bile salts, then combined with micelles so they can be transported across the glycocalyx/unstirred layer. The monoglycerides diffuse through the cells’ membranes. When in the cell, they combine with proteins, glycoproteins and cholesterol to form chylomicrons and then move into the lymph/lacteal system.
The structure of the larger intestines
No microvilli but lots of mucus-secreting goblet cells to compact and help move the chyme.
No carrier-mediated absorption e.g. just diffusion.
Absorption of water, ions, vitamins, sugars and salts remaining.
Pockets allow the chyme to move slower so max absorption of substances (Haustra).
Lymphoid tissue protects the large intestines from bacteria.
Sphincters regulate exits.
The benefits of gut flora
Complex carb and fibre fermentation.
Produces some vitamins (B9, K) and helps absorb B12.
Regulates the gut’s immune response.
Benefits of dietary fibre
Holds water and slows down the absorption of enzymes and nutrients.
Slows down the emptying of the gut and controls the motility of the chyme by adding bulk.
Prevents and treats constipation and haemorrhage.
Increases motility of the gut.
Types/causes of malabsorption
. Infection of the intestines changes the way they react to substances e.g. immune response to gluten caused by coeliacs disease.
. Problems with the digestive system e.g. the enzymes
. Damaged carriers/problems with the absorption of the nutrients.
Causes of diarrhoea
. Changes in osmotic gradient - nutrients not digested properly/lots of solute in chyme means more water moves into lumen than out.
. Changes in cells lining the intestines - e.g. cholera makes more Cl- ions move into lumen so water gets moved in too bc of the changes in osmotic gradient.
. More water released than absorbed.
. Infection/inflammation of the epithelium alters absorption/secretion.
. Changes in motility - irritable bowel syndrome mean chyme moves too fast for water absorption.
Colon motility and controls
Normally segmented contractions allow the chyme to be mixed and give time to water absorption. When defecating, mass movement into rectum activates stretch receptors which send afferent signals to the spinal cord.
Voluntary control of external anal sphincter.
Parasymp and symp control internal anal sphincter
Control of storage and emptying of the colon
Storage = relaxation of rectum/colon and sphincters closing. Emptying = contractions in colon/rectum and raised abdominal pressure. Relaxation/opening of sphincters. Doesn't work if obstruction or spinal cord damage.
Different stages of toxic detection
Pre-ingestion (sight, smell, taste)
Pre-absorption (mechano- and chemoreceptors in lumen detects toxins and chemicals and cause emesis to stop absorption)
Post-absorption (chemoreceptive centre outside blood-brain barrier stimulates vomiting centres to stop chemicals and toxins going through blood-brain barrier)
Nausea function and symptoms
To stop further ingestion of food. Causes sweating, salvation, palor, changed breathing and heart rate.
Steps to vomiting
Duodenum contracts so food goes into the stomach (which relaxes to accommodate this).
Antral mobility inhibited to stop gastric emptying.
Slow and deep breathing to close the glottis and reduce oesophageal pressure.
Air and saliva are drawn into the oesophagus to protect it and decrease pressure.
Expiration against a closed glottis and abdominal contractions increase abdominal pressure.
External and inner oesophageal sphincters open.
Contraction of stomach and abdomen and diaphragm.
How is the respiratory tract protected during emesis (vomiting)
- Glottis closed
- Soft palate elevated to close the nasopharynx
- To protect the respiratory tract from acidic contents.
What triggers emesis
. Chemoreceptor centre in the blood-brain barrier - drugs, toxins.
. Chemical and mechanical receptors
. Irritation to back of the throat
. Stimulation of hypothalamus - pain, sight, smell
. Vestibular apparatus
. Distention of the stomach or duodenum
Emetic pathway
5-HT molecules released which bind to nerves or via blood go to the chemoreceptive centre and stimulate vomiting centre directly or indirectly.
Chemotherapy’s affect on the emetic pathway
Causes release of 5-HT receptors
Anti-emetic drugs
Block 5-HT/are antagonists and stop them from acting on the vomiting centre. Anti-histamines can act in the same way to stop travel sickness as histamine stimulates the release of 5-HT too.
Nutritional excess’ effects on oral health and examples
Excess fluoride = fluorosis
Some drugs e.g. tetracycline (fibrosis drug) can cause intrinsic enamel staining during enamel formation
Nutritional (Vitamin/mineral) deficiencies that affect oral health
Vit K, A, C, D, B9/12
Protein
Calcium and phosphate
How does a deficiency of Vit D affect oral health
Delayed dental development/eruption Enlarged pulp horns and pulp chambers Clefts or grooves in the enamel/dentine Enamel hypoplasia Spontaneous abscesses and more problems with the teeth.
How does a deficiency of Vit C affect oral health
Affects collagen formation so caused inflamed, bleeding gums, and lack of PDL so wobbly teeth.
How does a deficiency of Vit B9/B12 affect oral health
Affects DNA synthesis (Carbon Carriers). Leads to glossitis, ulcers, angular chelitits and poor gum health.
How does a deficiency of Calcium/phosphate affect oral health
Enamel hypoplasia
How does a deficiency of Vit K affect oral health
Bleeding (coagulation problems)
How does a deficiency of protein affect oral health
Pale ulcers
Main oral signs of malnutrition
Ulcers, glossitis, angular chelitis,
the effects of PEG feeding on oral health
No bacteria or sugar = no caries but no saliva stimulation so build up of calculus which can chip off and be inhaled.
Orofacial granulomatitis
Hypersensitivity to certain substances e.g. benzoates, some essential oils, cinnamon, preservatives.
Causes inflamed lips and gums, ulcers, angular chelitits in while GI tract.
Treat by having a restricted diet and steroids to dampen the immune response
Triglyceride structure
Glycerol attached to 3 fatty acids via ester bonds.
Digestion of lipids
Broken down by lipases and micelles into triglycerides and then enter intestine epithelial cells where they are combined with proteins and cholesterol to form chylomicrons which enter the lymphatic system.
Structure of chylomicrons
A casing of phospholipids so they can diffuse into cells.
Apoproteins can be detected by receptors.
Cholesterol
Triglycerides in middle
How are chylomicrons digested after they are in blood
Broken down into fatty acids and glycerol by lipoprotein lipases, released by cells that need the fatty acids e.g. adipose tissue. This is controlled by insulin which detects the apoproteins. Fatty acids are taken into the cells and glycerol and remnants recycled.
VLDL and digestion
Similar structure to chylomicrons. Made by the liver - fatty acid + glycerol and then other lipids and proteins added.
Fatty acid oxidation
Beta oxidation. Fatty acids diffuse into cells and stimulate acyl CoA to go to mitochondria (via ATP) where it is converted into acetyl CoA (releases e- for e- transport chain) and enters TCA cycle. Stimulated by high glucagon or low insulin levels.
What is cholesterol needed for and how does the body regulate it
Needed for bile (biliary salts), cell membranes, steroids hormones, VLDL, Vit D. Absorbed by gut epithelium but can’t be completed metabolised so some gets returned to the lumen and excreted. Can be synthesised and recycled
How is cholesterol synthesised by the body
Synthesised in the liver. Acetyl CoA converted into a precursor via enzyme reductase (target for Statins).
How do bile salts act
Negative charge (e-) breaks up the lipids. Get modified by bacteria so can’t always be recycled. Can be converted to cholesterol esters and added to VLDL.