3What is FoodFood is any substance consumed to provide nutritional support for the body.It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals.The substance is ingested by an organism and assimilated by the organism's cells in an effort to produce energy, maintain life, or stimulate growth.
4Digestionis the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream.Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones.Proteins are hydrolyzed to Amino-acidsPolysaccharides into mono-saccharaides / hexoses like glucose/fructose/galactose
5Lipids into fatty acids, mono and diglycerides and even glycerol. Is brought by GI juices like saliva, gastric, pancreatic, intestinal juices and the bile.GI also produce hormones regulating activity of secretion of juices.Gastrin, cholecystokinin, secretin, glicentin, pancreatic polypeptides,
6Digestion may beMechanicalChewing : mouth teethChurrning : stomachSegmentation: intstinesChemicalBy various secretions/ enzymes present in various part of GIT.
7Absorption:normal assimilation by the tissues of the products of digestion.Absorption starts in the proximal portion of the small intestine(jejunum):butVitamin B12 and bile salts are absorbed in the distal part of the small intestine (ileum). Water , uncombined vitamins and minerals do not go undergo digestion and are absorbed as such.
8Purpose of digestion/absorption under nutritioni- Impaired growthii-Defective immune mechanismiii-Reduced work capacityOver nutritioni- Obesityii-CV diseasesiii-Cancers
20Ebner's glands, also Von Ebner's glands are exocrine glands found in the mouth. More specifically, they are serous salivary glands which reside adjacent to the moats surrounding the circumvallate papillae in the posterior one-third of the tongue, anterior to the terminal sulcus They secrete lingual lipase
22Histological typesSerous glandsMucus glandsMixed serous and mucus glandssecretion varies according to gland Parotid: watery, rich in amylase Sublingual: viscous, rich in mucin and glycoprotein Submandibular : mixed gland serous and mucous glands
23Glands are acini lined by serous or mucus cells. Acini pour secretion via intercellular canalculi into intercalated ducts which drain into striated duct ending into excretory ducts opening into oral cavity
26Composition :varies at different timeWater 99.5%Inorganic constituents :1/3 of solids –Na+ ,K+, Ca++, Mg++ , Cl- ,HCO3- , sulfate , phosphate, nitrate, iodide and thiocynate (smoker).at normal flow rateNa+,Cl- concentration is less , more K+
27With increased secretion rate : K+ falls, Na+ Cl-, HCO3 increased greatlyNa+ absorption is carried out through Na+ K+ ATPase pump.Excess of aldosterone decreases absorption of Na, Cl- but reverse for K+
28Volume: at rest 20 ml /hour, increased at meal time 1000-1500 ml/day Specific gravity: (hypotonic) , osmolality increased in dehydrationReaction : resting glands- acidic 6.4 – 6.9 , pH determined by HCO3 content. In mouth ,it loses CO2 and becomes alkaline,
29Salivary amylase(ptylin) Lingual lipase (Ebner,s glands) Organic constituents:Salivary amylase(ptylin)Lingual lipase (Ebner,s glands)mucins (mucoproteins)Small amount of lactic acid, ascorbic acid, choline, phenol, urea, cholesterol,Blood group substances (secretors)Kallikerin in saliva acts on kininogen to liberate bradykinin (vasodilator)Ig A (defense factor)
30Salivary Amylase (ptyalin) pH is around neutrality(6.9)it is α-amylase (endoamylase)Action of this enzyme only lasts for a short time.Hydrolyses polysaccharides at α(1—4) linkages not 1—6 linkages,terminal α (1—4) and 1—4 α linkages next to branching points.Activity of amylase is increased by Cl-
31Ptylin has no β-(1—4) glucosidase and hence cellulose is not digested in man and passes as such. End products are:oligosacharides,disach (maltose)trisach (maltotriose),some larger polymers with 1—4 linkages.glucose formation is almost negligible.
32Resultant product is limit dextrins (short branched and un-branched oilgosaccharides) Saliva moistens the food and even dissolve it partially.Teeth and tongue helps in chewing (mechanical digestion) and moistened and masticated food is converted into semi-sold mass “bolus”
36alkaline favor tartar deposition in gums (CaCO3 or calcium phosphate)
37Salivary and gastric LIPASES are acid lipases (pH 4-6). TAGs of short and medium chain length (as in milk fat) are the primary target.Thus this salivary/ gastric lipase play a role in neonatal lipid digestion, which is primary source of energy.They(both salivary and gastric lipases) are important in disease of pancreas like cystic fibrosis when strong pancreatic lipase is not available
38Lipases act on position 3 of TAG liberating 1,2-diglycerol(DAG) and free FA. Lingual lipase is active in stomach and brings about 30% hydrolysis.
40Functions of Saliva:1. Lubrication /moistening: due to content of mucin-food moistened, chewing facilitate mixing of mucin and swallowing is made easy.2. Solvent action:-by dissolution of food it stimulate taste buds, increases appetite , and further saliva secretion
413.Cleansing action: Continuous flow of saliva maintains good oral hygeine, by inhibiting bacterial growth. Lysozyme enzyme present is natural anti-bactrial agent. 4. Secretary functions: saliva contains haptocorrin (glyco-protein) aids vitamin B12 absorption.
425. Digestive function:salivary amylase and lingual lipase present in saliva exert digestive function. Catalyzes hydrolysis of polysaccharides (α-1-4 linkages)(not of 1-6 linkages).End productsoligosaccharides, disaccharides (maltose) tri-saccharides (maltotriose).Glucose formation negligible.
437.Regulation of water metabolism: 6. Excretory function:antibiotics, metals-(Pb,Hg),drugs (iodides), alkaloids(morphine) viruses(polio-rabies-hepatitis-HIV-mumps), urea in chronic cases7.Regulation of water metabolism:in dehydration secretion is decreased-dryness of mouth –produce sensation of thirst and forcing to drink water.
448. Esophageal clearing: 9. Deiodination : of thyroid hormones and take part in regulation of hormone.
45Salivary glands supplied by Parasympathetic cholinergic : primarily concerned with secretion of saliva, stimulation result vasodilatation and secretion by acinar cells (acetylcholine-blocked by atropine), vasodilatation is due to bradykinin and VIP. Vasoactive intestinal peptides
46Sympathetic adrenergic: when stimulated ,vasoconstriction, contraction of myo-epithelial cells secretion is quite small amount of saliva
47Regulation of saliva:Spontaneous secretion-resting : continuous without any factor (continuous release of acetylcholine), keep mouth-pharynx moistUnconditioned reflexes:material placed in mouth, movement of tongue, neural mechano-chemical receptors stimulated by dryness of mucosa ,chewing, chemical in food
48Reflexes stimulate salivation center in medulla, near to it lie respiratory-vomiting centers. Conditioned reflexes :occur in empty mouthimpulses arise in special senses organs like sight and smell, salivation center present in brain nausea/vomiting associated with salivation.
50Xerostomia (also termed dry mouth as a symptom or dry mouth syndrome as a syndrome) is dryness in the mouth (xero- +stom- + -ia), which may be associated with a change in the composition of saliva, or reduced salivary flow (hyposalivation), or have no identifiable cause.
51Causes: 1. Medication-older person use excess medicine for various diseases 2. Mouth breathing 3. Dehydration 4. Radiation to salivary glands 5. Psychogenic
53Chewing is the most efficient way to stimulate salivary flow by causing muscles to compress the salivary glands and release saliva. Through internal feedback mechanisms the taste and consistency of food also affect the quantity of saliva produced. It is difficult to exhaust the salivary glands, so chewing throughout the day to maintain stimulated salivary flow is possible.
54Measure of Saliva normal resting state stimulated state
55The person chews a piece of paraffin until it becomes soft The person chews a piece of paraffin until it becomes soft. Before the collection is started the first portion of saliva is swallowed. Start timer and the chewing is continued for another 5 minutes (for subjects with high secretion rate, 3 minutes may be enough).
56The person sits in an upright position with his head inclined forward so that the production of saliva is collected in the floor of the mouth and then flows out over the lip.Saliva formed is let to drip into the graduated test tube or a measure-cup for 15 minutes.The result of this collection is expressed as milliliters per minute.
57The saliva is spat out at short intervals in a graduated test tube or a measure-cup during the collection period. The collected saliva is then measured. The measurement should not include the foam which is formed during the collection. The result is expressed as mililiters per minute.