Human Digestive System

 

I.  The peritoneum:

 

            A.  Visceral peritoneum – covers the outer surfaces of the organs

           

            B.  Parietal peritoneum – lines the wall of the abdominal cavity

 

            C.  Peritoneal cavity – contains peritoneal fluid (a serous fluid)

 

            D.  Mesenteries – double-folds of peritoneum attaching organs to the body wall

                       

1.      Mesentery proper – suspends the jejunum and ileum

2.      Mesocolons – suspend the sections of the large intestine

3.      Greater omentum - “apron-like”; extends from the greater curvature of the stomach over the intestines

4.   Lesser omentum – extension between the liver and the lesser curvature of the stomach

5.      Falciform ligament - sheet of parietal peritoneum between the right and left lobes of the liver

6.   Round ligament - remnant of the umbilical vein at the inferior edge of the falciform ligament

 

 

II.  Anatomy of the alimentary canal

 

            A.  Oral cavity

 

1.  Hard palate

2.  Soft palate – the tip of this structure is the uvula

3.  Tongue

                       

            a.  lingual frenulum – anchors the tongue to the floor of the mouth

b.  papillae -  (singular – papilla); “bumps” on the surface of the tongue;  All but the filiform papillae contain microscopic taste buds; Note 4 types of papillae (see page 301 of your lab manual):

           

                                                1.  filiform papillae - “pointed”; lack taste buds

                                                2.  fungiform papillae - “mushroom-like”

                                                3.  foliate papillae - “leaf-like”; on sides of tongue

                                                4.  circumvallate papillae - large papillae arranged in an inverted “V” at posterior aspect of tongue

 

            B.  The pharynx 

*Note that this is a review from the respiratory system checklist.

 

            1.  Nasopharynx – superior portion of the pharynx

 

a.  auditory (Eustachian) tube opening

                              b.  pharyngeal tonsil (adenoid) – single tonsil in the posterior wall of the nasopharynx

           

                        2.  Oropharynx – intermediate portion of the pharynx

 

                              a.  palatine tonsils – paired tonsils found in the lateral walls

                                    b.  lingual tonsils – paired tonsils at the base of the tongue

 

                        3.  Laryngopharynx – inferior portion of the pharynx

 

            C.  Esophagus

 

                        1.  Esophageal hiatus

 

            D.  Stomach

 

                        1.  Cardiac (lower esophageal) sphincter – allows a food bolus to enter the stomach; prevents chyme from entering the esophagus

                        2.  Cardiac region (cardia) – region near junction with the esophagus

                        3.  Fundic region (fundus) – “rounded” upper portion

                        4.  Body of stomach – main region

                        5.  Pyloric region (pylorus) – narrow inferior region

                        6.  Pyloric sphincter – controls the release of chyme into the duodenum

                        7.  Rugae – large “wrinkles” seen in the empty stomach

 

            E.  Small intestine

 

                        1.  Duodenum – note the retroperitoneal position of the duodenum

                        2.  Jejunum

                        3.  Ileum

                        4.  Ileocecal valve

                        5.  Plicae (plicae circulares) – (singular – plica) circular folds

 

            F.  Large intestine

 

                        1.  Cecum

                        2.  (Vermiform) appendix – “worm-like” extension off of the cecum

                        3.  Ascending colon

                        4.  Transverse colon

                        5.  Descending colon

                        6.  Sigmoid colon

                        7.  Rectum

                        8.  Anal canal – extends from where the rectum travels through the urogenital diaphragm (muscular floor of the pelvic cavity) to the anus

 

                                    a.  anal columns – longitudinal folds of the anal canal lining

                                    b.  internal anal sphincter

                                    c.  external anal sphincter

 

                        9.  Urogenital diaphragm

                        10.  Anus

                        11.  Special features of the large intestine:

 

                                    a.  taeniae coli

                                    b.  haustra

                                    c.  fatty appendices (epiploic appendages)

 

           

III.  Accessory structures associated with the oral cavity

 

            A.  Tongue (review previous structures studied)

            B.  Hyoid bone

            C.  Mandible

            D.  Masseter muscle

            E.  Maxilla (maxillary bones)

            F.  Alveolar processes – bony “sockets” of the mandible and maxillary bones

            G.  Types of teeth:

 

                        1.  Central incisors

                        2.  Lateral incisors

                        3.  Canines (cuspids) – tear/shred food

                        4.  Premolars (bicuspids) – crush/grind food

                        5.  Molars – crush/grind food

 

            H.  Gingiva – “gums”

            I.   Gingival sulcus (gingival margin; gum line)

                        J.  Periodontal ligament – fibrous tissue that anchors the tooth in the alveolus (tooth socket)

            K.  Parts of a tooth:

 

                        1.  Crown

                        2.  Neck – region at the gum line where crown and root meet

                        3.  Root

                        4.  Enamel

                        5.  Dentin

                        6.  Pulp (central) cavity

                        7.  Root canal – narrow extension(s) of the pulp cavity within the root

                        8.  Cementum – bone-like substance that covers the root and attaches to the periodontal ligament

 

            L.  Dental formulae to know:

 

                        1.  Human deciduous (primary) teeth: I2/2, C1/1, P0/0, M2/2 = 10

                        2.  Human adult teeth: I2/2, C1/1, P2/2, M3/3 = 16

                        3.  Cat (FYI only): I3/3, C1/1, P3/2, M1/1 = 15

 

            M.  Salivary glands and ducts

 

                        1.  Parotid gland

                        2.  Parotid duct – empties saliva near the upper second molar

                        3.  Submandibular gland

                        4.  Submandibular duct - opens behind lower central incisors

                        5.  Sublingual glands

                        6.  Sublingual ducts

 

IV.  Accessory organs associated with the small intestine

 

            A.  Liver - produces bile

 

                        1.  right and left hepatic ducts – carry bile from the right and left lobes

                        2.  common hepatic duct

 

            B.  Gallbladder - stores bile

 

                        1.  cystic duct

 

            C.  Common bile duct – formed by the common hepatic and cystic ducts

 

            E.  Hepatopancreatic ampulla (duodenal ampulla; ampulla of Vater) – formed by the joining of the pancreatic duct and the common bile duct

 

            F.  Hepatopancreatic sphincter (sphincter of Oddi) – surrounds the hepatopancreatic ampulla

 

            G.  (Major) duodenal papilla - small, finger-like projection into the lumen of the duodenum; made up of the hepatopancreatic ampulla and sphincter

 

            H.  Pancreas – note the retoperitoneal location; lies posterior to the greater curvature of the stomach and along the curve of the duodenum

 

            I.  Pancreatic duct – the main duct of the pancreas; ends at the (major) duodenal papilla

 

            J.  Accessory pancreatic duct – ends at the minor duodenal papilla (proximal to the major duodenal papilla)

 

Last Updated:  12/31/2006