The Alimentary System

SHANDONG UNIVERSITYLiu Zhiyu

The abdominal regions Nine regionsR. hypochondriac region Epigastric region L. hypochondriac region

R. lateral regions Umbilical region L. lateral regions

R. inguinal regionL. inguinal region

Pubic region

The abdominal regions Four quadrants Left and right upper quadrants Left and right lower quadrants

Composition Alimentary canal Mouth Pharynx Esophagus Stomach

Small intestine

Large intestine

Duodenum Jejunum Ileum Alimentary glands Superior alimentary canal

Inferior alimentary canal

Major salivary glands Liver Pancreas Function: ingestion, digestion, absorption, egesting

Alimentary canal

The Oral Cavity

The Oral Cavity Consists of two partsOral vestibule : between cheeks and lip and teethOral cavity proper : within arch of teeth BoundariesAnterior and lateral: gum and teethPosterior: isthmus of fauces Roof: palate Floor: tongue, muscles and mucous membraneOral vestibule leads, by the space behind the molar teeth, into the oral cavity proper

Palate Two partsHard palate : anterior 2/3 formed by the maxilla and palatine bone Soft palate : posterior 1/3Velum palatinum Uvula Palatoglossal arch Palatopharyngeal arch Isthmus of fauces formed by uvula, free border of velum palatinum, both side of palatoglossal arches, and root of tongue.

Teeth

Teeth General featuresTwo sets: Deciduous Permanent Classification: Incisors Canine Premolars Molars

Deciduous teeth

20 in number, ten teeth in each mandibular and maxillary arch Deciduous central incisor , deciduous lateral incisor , deciduous canine , first deciduous molar second deciduous molar in each quadrant

Upper jaw total 20Lower jaw in. in. can. mol. mol.

Eruption: stars at about 6 mouth of age and continues to beginning of 3rd yearShedding: occurs between 6th and 12th years with replacement by permanent teeth

Deciduous teeth

Deciduous central incisor Deciduous lateral incisor Deciduous canine First deciduous molar Second deciduous molar

Permanent teeth (adult)32 in numbersixteen in each mandibular and maxillary archTwo incisors, one canine, two premolars, and three molars in each quadrant Upper jaw 1 2 3 4 5 6 7 8 total 32 Lower jaw

First permanent molar appears at about 6 yearsThird molars (wisdom teeth)many erupt at any time after 12 years of age or not at all (impaction). 37

Permanent teeth Central incisor Lateral incisor Canine 1st premolar 2nd premolar 1st molar 2nd molar 3rd molar

Teeth Part and structure of the teethEach tooth consists of 3 parts:Crown Neck Root Dental cavity Pulp chamber Root canal transmits the nerves and vessels to and from the dental cavity through the apical foramen

Teeth Calcified tissues Dentine is a yellowish white tissue, that forms the bulk of tooth.Enamel is a hard, brittle white tissue that covers the crown of the toothCement is an unusual form of bone that covers the root of the toothDental pulp formed connective tissue, blood vessels and nerves.

Teeth Periodontal tissue Periodontal membrane Alveolar bone Gum

Teeth

Tongue Two parts: divided two parts by v-shaped terminal sulcus Body of tongue anterior 2/3 Apex of tongue free rounded tipAt the apex of terminal sulcus is a small median pit, the foramen cecum of tongue Root of tongue posterior 1/3

Tongue Lingual mucous membrane Papillae of tongue Filiform papillae Fungiform papillae Foliate papillae Vallate papillae Lingual tonsil masses of submucosal lymphoid tissue on the root of tongue

contain taste buds

Inferior surface of tongueSublingual caruncle small elevationSublingual fold Frenulum of tongue a midline fold of mucous membrane connecting tongue to floor of mouth

Muscles of tongue

Intrinsic muscles of tongue Involved in changing shape of tongue Include longitudinal, transverse and vertical muscles of tongue

Tongue Extrinsic muscles of tongue Genioglossus Arises from mental spine of mandible and inserts into either side of midline of tongueAction: acting together draw tongue forward and downward (depresses and protrudes tongue ); acting along making apex of tongue to opposite sideHyoglossus Tyloglossus Involved in determining shape and position of tongue

Major salivary glands Parotid gland Superficial part: triangular in shape, lies below and in front of the external acoustic meatus, and partially covers the masseter.Deep part: lies deep to medial pterygoid .Parotid duct: arises front anterior border of gland, runs over the masseter a fingers breadth below the zygomatic arch to pierce the buccinator and opens into the mouth cavity, opposite the upper second molar tooth

Major salivary glands Submandibular gland

Position: lies in submandibular triangle, between anterior and posterior bellies of digastricDuct opens on to sublingual caruncle

Major salivary glands Sublingual gland Position: situated beneath the mucous membrane of the floor of mouthDucts Major sublingual ductopens onto the sublingual caruncleMinor sublingual ductsopen onto the sublingual fold

The Pharynx

General featuresA fibromuscular tube, part of digestive and respiratory systemsExtends from base of skull to the inferior border of cricoid cartilage (lower border of C6 level)Three segmentsNasopharynx Oropharynx Laryngopharynx

The Pharynx

Nasopharynx posterior to nasal cavitiesExtends from the base of skull to level of soft palate, belowFeaturesPharyngeal opening of auditory tube Tubal torus Pharyngeal recess Tubal tonsil Pharyngeal tonsil

The Pharynx

Oropharynx posterior to oral cavityLies below soft palate, extends to upper border of epiglottisFeaturesMedian glossoepiglottic fold Epiglottic vallecula Palatine tonsil lies within tonsillar fossa

The Pharynx

Laryngopharynx posterior to larynxExtends from upper border of epiglottis to the level of lower border of C6Piriform recess a deep depression on each side of aperture of larynx, common side for lodgement of foreign bodies (for example, fish bones)

The Pharynx

Lymphatic ring Consists of Pharyngeal tonsiltubal tonsilPalatine tonsillingual tonsilForming a circular band of lymphoid tissue at oropharyngeal isthmus

The Esophagus Three constrictions 1. Where it beginning, 15cm from incisors, lies at level of C6, is the narrowest part of the esophagus 2. Where it is crossed by left principal bronchus, 25cm from incisors, lies at level of intervertebral disc between T4 and T5. 3. Where it passes through the esophageal hiatus of diaphragm, 40cm from incisors, at level of T10

The Esophagus

General features a muscular tuber about 25cm long, connecting the pharynx at level of C6 vertebra, passes through the diaphragm at level of T10 vertebra and after 1~2 cm enters the stomachDivision Cervical part Thoracic partAbdominal part

The Stomach

ShapeTwo surface: anterior and posteriorTwo curvaturesLesser curvature : short, concave and directed to the right and upward, near its lower part is angular incisure Greater curvature : long, convex and directed to the left and downward, at the junction of left margin of esophagus and greater curvature is cardiac incisure Two openingsCardia Pylorus

The Stomach

Four partsCardiac part Fundus of stomach Body of stomach Pyloric part Pyloric antrum Pyloric canal

The Stomach

Structure of stomach wall consists of four usual layersMucous membraneSubmucous ( loose areolar tissue connecting the mucous and muscular layer)Muscular layer contains:The most superficial longitudinal fibersInner circular fibresSphincter of pylorus Pyloric valve Innermost oblique fibresSerous (visceral peritoneum)

The Stomach

Location Mainly parts is situated in the left hypochondriac regionSmall in the epigastric regionThe cardia is situated to the left of T11, the pylorus lies to the right of L1

Variations in position of stomach

The Small IntestineAbout 5-7m long Division: Duodenum Jejunum Ileum DuodenumJejunum Ileum

Duodenum Four parts Superior part Duodenal cap Superior duodednal flexure Descending part Inferior duodenal flexure Horizontal part Ascending part Duodenojejunal flexure

Duodenum Descending part Longitudinal fold of duodenum Major duodenal papilla the common opening of the common bile duct and pancreatic duct, 75cm from incisorsMinor duodenal papilla

Contrast radiographic appearance of the duodenum showing a distended duodenal cap and the remainder of the duodenum up to the duodenojejunal flexure

DuodenumSuspensory muscle of duodenum (ligament of Treitz), a surgical landmark, descends from the right crus of diaphragm to duodenal termination.

Jejunum and ileum

CharacteristicJejunumIleumPositionUpper 2/5, upper left part of abdominal cavity Lower 3/5, lower right part of abdominal cavity DiameterGreaterLessWallThickerThinCircular foldsLarger, numerous and large villiFewersmaller and less abundant villiVascularityGreaterLessVasa recta Long Short Color Deeper redPaler pink Lymphatic folliclesSolitaryAggregatedFat in mesentery LessMore

Jejunum and ileum

Jejunum and ileumMeckels diverticulumPersistence of proximal portion of yolk sac (vitelline duct, omphalomesenteric duct)Common malformation of digestive tract (24%) more prevalent in malesAbout 25cm long and located 30100cm from ileocecal valveUsually asymptomatic but: May become inflamed (mimicking appendcitis) or bleedMay be attached to umbilicus by a fibrous cord (distal end of yolk stalk) and cause intestinal obstruction by compressing adjacent intestinal loops

Large Intestine

Approximately 1.5m long, Five parts: Cecum Vermiform appendix Colon Rectum Canal

Large Intestine FeaturesColic bands Haustra of colon Epiploic appendices

Cecum Position: lies in right iliac fossaShape: Blind sac, first part of large intestine, with largest diameter and thinnest wallThe ileum enters the cecum obliquely, and partially invaginates into it, forming the ileocecal valve Consists of two folds Probably delays flow of ileal contents into large intestine

Vermiform appendix Blind worm-like tube, 68cm long, about 0.5cm in diameter Opens into posteromedial aspect of cecumabout 2 cm below ileoceal orifice The base of the appendix lies at the point of convergence of three colic bands (used as a guide to find the appendix during operation)

Vermiform appendix Surface marking of the base is at the so-called McBurneys point which is at junction of lateral and middle thirds of line joining right anterior superior iliac spine and umbilicus

Vermiform appendix Tip variable in positionPreileal 7%Pelvic41%Retrocecal 29%Retroileal4%Subcecal17%

Vermiform appendix Mesoappendix Triangular mesenteryextends from terminal part of ileum to appendixAppendicular a. runs in free margin of the meseoappendix then along wall of appendix

Colon Ascending colon right colic flexure Transverse colon left colic flexure Descending colon descends almost vertically from left colic flexure to sigmoid colon at left iliac crest.Sigmoid colon extends from descending colon to rectum at level of S3.

Rectum Position: within pelvic cavity, extends from S3 to pelvic diaphragm.CurvesSagittal planeSacral flexure : convex backwardPerineal flexure : convex forward.Coronal planeUpper and lower partconvex to the right.Middle partconvex to the left.Lower part of rectum dilated, to from ampulla of rectum Three transverse folds of rectum

Anal canal Anal columns : 6 11 in numberAnal valves Anal sinuses Anorectal line Dentate line Above line, of endodermal originBelow line, of ectodermal originAnal pecten White line (Hiltons line) Anus Anal sphincters Sphincter ani internus Sphincter ani externus