The Alimentary System SHANDONG UNIVERSITY Liu Zhiyu

The abdominal regions —— Nine regions R. hypochondriac region Epigastric region L. hypochondriac region R. lateral regions Umbilical region L. lateral regions R. inguinal region L. 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

Mouth Pharynx Esophagus Stomach Duodenum Jejunum Ileum Large intestine Liver Pancreas Major salivary glands

Alimentary canal

The Oral Cavity

Consists of two parts  Oral vestibule : between cheeks and lip and teeth  Oral cavity proper : within arch of teeth Boundaries  Anterior and lateral: gum and teeth  Posterior: isthmus of fauces  Roof: palate  Floor: tongue, muscles and mucous membrane Oral vestibule leads, by the space behind the molar teeth, into the oral cavity proper

Palate Two parts  Hard palate : anterior 2/3 ， formed by the maxilla and palatine bone Soft palate : posterior 1/3 Velum 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

General features Two 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 Ⅰ Ⅱ Ⅲ Ⅳ Ⅴ total 20 Lower jaw in. in. can. mol. mol. Eruption: stars at about 6 mouth of age and continues to beginning of 3rd year Shedding: occurs between 6th and 12th years with replacement by permanent teeth Ⅱ Ⅳ

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

Permanent teeth (adult) 32 in number ， sixteen in each mandibular and maxillary arch Two incisors, one canine, two premolars, and three molars in each quadrant Upper jaw total 32 Lower jaw First permanent molar － appears at about 6 years Third molars (wisdom teeth) － many erupt at any time after 12 years of age or not at all (impaction). 3 7

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

Teeth Part and structure of the teeth Each 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 tooth  Cement － is an unusual form of bone that covers the root of the tooth  Dental pulp formed connective tissue, blood vessels and nerves.

Teeth 牙 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 tip  At the apex of terminal sulcus is a small median pit, the foramen cecum of tongue Root of tongue － posterior 1/3

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 Tongue contain taste buds

Inferior surface of tongue Sublingual caruncle － small elevation Sublingual 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 tongue Action: acting together draw tongue forward and downward (depresses and protrudes tongue ); acting along making apex of tongue to opposite side  Hyoglossus  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 finger’s 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 digastric Duct opens on to sublingual caruncle

Major salivary glands Sublingual gland Position: situated beneath the mucous membrane of the floor of mouth Ducts  Major sublingual duct － opens onto the sublingual caruncle  Minor sublingual ducts － open onto the sublingual fold

The Pharynx General features A –fibromuscular tube, part of digestive and respiratory systems Extends from base of skull to the inferior border of cricoid cartilage (lower border of C6 level) Three segments Nasopharynx Oropharynx Laryngopharynx

The Pharynx Nasopharynx —posterior to nasal cavities Extends from the base of skull to level of soft palate, below Features  Pharyngeal opening of auditory tube  Tubal torus  Pharyngeal recess  Tubal tonsil  Pharyngeal tonsil

The Pharynx Oropharynx － posterior to oral cavity Lies below soft palate, extends to upper border of epiglottis Features  Median glossoepiglottic fold  Epiglottic vallecula  Palatine tonsil － lies within tonsillar fossa

The Pharynx Laryngopharynx － posterior to larynx Extends from upper border of epiglottis to the level of lower border of C6 Piriform 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 tonsil  tubal tonsil  Palatine tonsil  lingual tonsil Forming a circular band of lymphoid tissue at oropharyngeal isthmus

The Esophagus 食管 ★ 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 stomach Division  Cervical part  Thoracic part  Abdominal part

The Stomach Shape Two surface: anterior and posterior Two curvatures  Lesser 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 openings  Cardia  Pylorus

The Stomach Four parts  Cardiac part  Fundus of stomach  Body of stomach  Pyloric part Pyloric antrum Pyloric canal

Cardiac part Fundus of stomach Body of stomach Pyloric antrum Pyloric canal Pyloric part

The Stomach Structure of stomach wall － consists of four usual layers Mucous membrane Submucous ( loose areolar tissue connecting the mucous and muscular layer) Muscular layer contains:  The most superficial longitudinal fibers  Inner circular fibres Sphincter of pylorus Pyloric valve  Innermost oblique fibres Serous (visceral peritoneum)

The Stomach Location Mainly parts is situated in the left hypochondriac region Small in the epigastric region The cardia is situated to the left of T11, the pylorus lies to the right of L1

Variations in position of stomach

The Small Intestine About 5-7m long Division:  Duodenum  Jejunum  Ileum Duodenum Jejunum 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 incisors Minor duodenal papilla

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

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

Jejunum and ileum CharacteristicJejunumIleum PositionUpper 2/5, upper left part of abdominal cavity Lower 3/5, lower right part of abdominal cavity DiameterGreaterLess WallThickerThin Circular foldsLarger, numerous and large villi Fewer ， smaller and less abundant villi VascularityGreaterLess Vasa recta Long Short ColorDeeper redPaler pink Lymphatic folliclesSolitaryAggregated Fat in mesentery LessMore

Jejunum and ileum

Meckel’s diverticulum Persistence of proximal portion of yolk sac (vitelline duct, omphalomesenteric duct) Common malformation of digestive tract (2 － 4%) － more prevalent in males About 2 － 5cm long and located 30 － 100cm from ileocecal valve Usually asymptomatic but:  May become inflamed (mimicking appendcitis) or bleed  May 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 Features Colic bands Haustra of colon Epiploic appendices

Cecum Position : lies in right iliac fossa Shape :  Blind sac, first part of large intestine, with largest diameter and thinnest wall  The 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, 6 － 8cm long, about 0.5cm in diameter Opens into posteromedial aspect of cecum ， about 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 McBurney’s 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 position Preileal － 7% Pelvic － 41% Retrocecal － 29% Retroileal － 4% Subcecal － 17%

Vermiform appendix Mesoappendix Triangular mesentery － extends from terminal part of ileum to appendix Appendicular a. runs in free margin of the meseoappendix then along wall of appendix

Colon 结肠 Ascending colon 升结肠  right colic flexure 结肠右曲 Transverse colon 横结肠  left colic flexure 结肠左曲 Descending colon 降结肠 descends almost vertically from left colic flexure to sigmoid colon at left iliac crest. Sigmoid colon 乙状结肠 － extends from descending colon to rectum at level of S3.

Rectum Position : within pelvic cavity, extends from S3 to pelvic diaphragm. Curves  Sagittal plane Sacral flexure : convex backward Perineal flexure : convex forward.  Coronal plane Upper and lower part － convex to the right. Middle part － convex 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 number Anal valves Anal sinuses Anorectal line Dentate line  Above line, of endodermal origin  Below line, of ectodermal origin Anal pecten White line (Hilton’s line) Anus Anal sphincters  Sphincter ani internus  Sphincter ani externus