Section 25 The Digestive System

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Section 25 The Digestive Framework. General life structures and digestive procedures Mouth through throat Stomach Liver, gallbladder and pancreas Small digestive tract Substance processing and assimilation Internal organ. Digestive Capacities. Ingestion = admission of sustenance Assimilation = breakdown of particles

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Section 25 The Digestive System General life structures & stomach related procedures Mouth through throat Stomach Liver, gallbladder & pancreas Small digestive system Chemical assimilation & retention Large digestive system

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Digestive Functions Ingestion = admission of sustenance Digestion = breakdown of atoms Absorption = take-up supplements into blood/lymph Defecation = end of undigested material

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Stages of Digestion Mechanical assimilation is physical breakdown of nourishment into littler particles teeth & beating activity of stomach & digestion tracts Chemical absorption is arrangement of hydrolysis responses that break macromolecules into their monomers catalysts from spit, stomach, pancreas & digestion tracts comes about polysaccharides into monosaccharides proteins into amino acids fats into glycerol and unsaturated fats

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Digestive Processes Motility = solid withdrawals that separate sustenance, blend it with chemicals & move it along Secretion = stomach related proteins & hormones Membrane transport = assimilation of supplements

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Subdivisions of the Digestive System Digestive tract (GI tract) 30 foot long tube stretching out from mouth to rear-end Accessory organs teeth, tongue, liver, gallbladder, pancreas, salivary organs

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Tissue Layers of the GI Tract Mucosa epithelium lamina propria muscularis mucosae Submucosa Muscularis externa inward roundabout layer external longitudinal layer Adventitia or Serosa areolar tissue or mesothelium

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Tissue Layers of the GI Tract

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Enteric Nervous Control Submucosal & myenteric plexuses control motility & emission in light of boosts to the mucosa

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Relationship to the Peritoneum Only duodenum, pancreas & parts of digestive organ are retroperitoneal Dorsal mesentery suspends GI tract & frames serosa (instinctive peritoneum) of stomach & digestion tracts Ventral mesentery frames lesser & more noteworthy omentum elegant layer of connective tissue contains lymph hubs, lymphatic vessels and veins

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Lesser & Greater Omentum Lesser appends stomach to liver Greater covers small digestive organs like a cook's garment

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Mesentery and Mesocolon Mesentery of small digestion tracts holds many veins Mesocolon grapples the colon to the back body divider

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Regulation of Digestive Tract Neural control short myenteric reflexes (gulping) long vagovagal reflexes (parasympathetic incitement of stomach related motility and discharge) Hormones dispatchers diffuse into circulatory system, removed targets Paracrine emissions flag-bearers diffuse to close-by target cells

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The Mouth or Oral Cavity

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Features of the Oral Cavity Cheeks and lips keep nourishment between teeth for biting, are basic for discourse & suckling in babies vestibule is space between teeth & cheeks cutaneous range versus red or vermilion zone Tongue is delicate, strong controller of sustenance papillae & taste buds on dorsal surface lingual organs emit spit, tonsils in root Hard & delicate sense of taste permit breathing & gnawing at same time palatoglossal & palatopharyngeal curves

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Permanent & Baby Teeth Baby teeth (20) by 2 years; Adult (32) in the vicinity of 6 and 25 Occlusal surfaces and cusp numbers vary

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Permanent & Deciduous Teeth in Child's Skull

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Tooth Structure Periodontal tendon is altered periosteum stays into alveolus Cementum & dentin are living tissue Enamel is noncellular emission framed amid improvement Root waterway leads into mash cavity nerves & veins Gingiva or gums

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Mastication or Chewing Breaks nourishment into littler pieces to be gulped  surface territory presented to stomach related proteins Contact of sustenance with tactile receptors triggers biting reflex tongue, buccinator & orbicularis oris control nourishment masseter & temporalis hoist the teeth to squash nourishment average & parallel pterygoids swing teeth in side-to-side pounding activity of molars

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Saliva Functions of spit dampen, start starch & fat absorption, rinse teeth, repress microscopic organisms, tie sustenance together into bolus Hypotonic arrangements of 99.5% water and solutes: amylase = starts starch processing lingual lipase = digests fat after achieves the stomach bodily fluid = helps in gulping lysozyme = compound that eliminates microorganisms immunoglobulin A = restrains bacterial development electrolytes = Na + , K + , Cl - , phosphate & bicarbonate pH of 6.8 to 7.0

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Salivary Glands Small inborn organs found under mucous film of mouth, lips, cheeks and tongue - emit at consistent rate 3 sets outward organs associated with oral pit by conduits parotid, submandibular and sublingual

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Histology of Salivary Glands Compound tubuloacinar organs Mucous cells emit bodily fluid Serous cells discharge thin liquid rich in amylase Mixed acinus is conceivable

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Salivation Total of 1 to 1.5 L of spit for every day Cells channel water from blood & include different substances Food invigorates receptors that flag salivatory cores in the medulla & pons parasympathetic incitement  salivary organs create thin spit, rich in chemicals thoughtful incitement  deliver less plentiful, thicker salivation, with more bodily fluid Higher mind focuses empower salivatory cores so locate, smell & considered sustenance cause salivation

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Pharynx Skeletal muscle profound layer – longitudinal introduction shallow layer – roundabout introduction predominant, center and sub-par pharyngeal constrictors

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The Esophagus Straight solid tube 25-30 cm since quite a while ago nonkeratinized stratified squamous epithelium esophageal organs in submucosa skeletal muscle in upper part & smooth in base Extends from pharynx to cardiovascular stomach going through esophageal rest in the stomach substandard pharyngeal constrictor rejects air from it Lower esophageal sphincter closes hole to reflux

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Swallowing or Deglutition Series of solid compressions facilitated by gulping focus in medulla & pons engine signals from cranial nerves V, VII, IX and XII Buccal stage tongue gathers nourishment & pushes it again into oropharynx Pharyngeal-esophageal stage delicate sense of taste rises & squares nasopharynx infrahyoid muscles lift larynx & epiglottis is collapsed back pharyngeal constrictors push bolus down throat fluids in 2 seconds - nourishment bolus may take 8 seconds bring down esophageal sphincter unwinds

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X beam of Swallowing in Esophagus

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Introduction to the Stomach Mechanically separates nourishment particles, liquifies the nourishment & starts synthetic absorption of protein & fat coming about soupy blend is called chyme Stomach does not retain any huge measure of supplements absorbs headache medicine & some lipid-dissolvable medications

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Gross Anatomy of the Stomach Muscular sac (interior volume from 50ml to 4L, FULL) J - molded organ with lesser & more prominent ebbs and flows provincial contrasts cardiovascular area simply inside cardiovascular hole fundus is domed segment better than esophageal opening body is primary bit of organ pyloric locale is restricted mediocre end antrum & pyloric trench Pylorus is opening to duodenum thick ring of smooth muscle shapes a sphincter

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Innervation and Circulation Innervation by parasympathetic filaments from vagus & thoughtful strands from the celiac plexus All blood depleted from stomach is sifted through the liver before coming back to heart

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Gross Anatomy of Stomach Notice: lump of fundus, narrowing of pyloric district, thickness of pyloric sphincter and more prominent & lesser bends

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Gross Anatomy of the Stomach

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Unique Features of Stomach Wall Mucosa basic columnar glandular epithelium lamina propria is loaded with tubular organs (gastric pits) Muscularis externa has 3 layers external longitudinal, center round & internal sideways layers

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Gastric Pit and Gastric Gland

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Cells of the Gastric Glands Mucous cells discharge bodily fluid Regenerative cells partition quickly to create new cells that relocate upwards towards surface Parietal cells discharge HCl corrosive & inherent component Chief cells discharge chymosin & lipase in earliest stages & pepsinogen all through life Enteroendocrine cells discharge hormones & paracrine envoys

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Opening of Gastric Pit

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Gastric Secretions 2 to 3 L of gastric juice/day (H 2 O, HCl & pepsin) Parietal cells contain carbonic anhydrase (CAH) CAH CO 2 + H 2 O  H 2 CO 3  HCO 3 - + H + H + is pumped into stomach lumen by H + K + ATPase antiporter utilizes ATP to pump H + out & K + in HCO 3 - traded for Cl - (chloride move) Cl - pumped out to join H + shaping HCl  HCO 3 - in blood causes basic tide (blood pH )

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Functions of Hydrochloric Acid Activates chemicals pepsin & lingual lipase Breaks up connective tissues & plant cell dividers liquifying nourishment to frame chyme Converts ingested ferric particles (Fe +3 ) to ferrous particles (Fe +2 ) that can be consumed & used for hemoglobin amalgamation Destroys ingested microbes & pathogens

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Gastric Enzymes & Intrinsic Factor Intrinsic variable (parietal cells ) fundamental for retention of B 12 by small digestive system essential for RBC generation (malevolent paleness) Pepsin - (boss cell) protein absorption emitted as pepsinogen (an idle zymogen) HCl changes over it to pepsin (dynamic frame) pepsin then initiates more pepsinogen Gastric lipase & chymosin (boss cell) lipase digests butterfat of drain in newborn child chymosin turns sour drain by coagulating its proteins

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Production & Action of Pepsin

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Chemical Messengers Many delivered by enteroendocrine cells hormones enter blood  far off cells paracrine discharges  neighboring cells Gut-cerebrum peptides flagging particles delivered in stomach related tract