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Anatomy of the Digestive System

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1 Anatomy of the Digestive System
Chapter 25 Target Test Date (Chapters 25 & 26): Block Days 4/6-4/7

2 Gastrointestinal (GI) Tract

3 Walls of the GI Tract 1. Mucosa inner lining of tract secretes mucous
Highly folded – increased surface area for absorption Microvilli Composed of 3 layers Mucous epithelium, lamina propria, muscularis mucosae

4 Walls of the GI Tract 2. Submucosa Mainly connective tissue Contains:
Exocrine glands Secretes acids & enzymes Parasympathetic nerves form the submucosal plexus

5 Walls of the GI Tract Muscularis Smooth muscle
2 layers Longitudinal (outer) Circular (inner) Move particles by peristalsis Myenteric plexus: found between 2 layers of smooth muscle

6 Walls of the GI Tract Serosa Outermost layer
Connective tissue and peritoneum (visceral layer) Mesentery connects the parietal & visceral portions of the peritoneum Serous membrane – two components (inner visceral layer; outer parietal layer) Mesentery contains nerves and blood vessels


8 Walls of the GI Tract – Cell Modifications
Although the layers remain the same throughout the GI tract, the cell types may change Ex: Mucosa layer of the esophagus is composed of stratified squamous cells to resist abrasion, but transitions to simple columnar cells for absorption and secretion

9 Mouth Also called the oral or buccal cavity Composed of:
Lips, cheeks, tongue, hard palate, soft palate

10 Tongue Skeletal muscle covered by mucous membrane
Helps in chewing (mastication), swallowing (deglutition) and speech Papillae cover upper portion of the tongue Vallate: posterior portion of tongue; contain taste buds Fungiform: sides and tip of tongue; contain taste buds Filiform: anterior 2/3 of tongue; do not contain taste buds

11 Tongue Frenulum – anchors tongue to floor of the mouth
Ankyloglossia: frenulum is too short; results in speech problems; “tongue-tied” Floor of mouth and underside of tongue are very vascular Sublingual drugs (nitroglycerin, morphine)


13 Salivary Glands Parotid Sublingual Submandibular
Upper jaw; anterior & inferior to external ear watery saliva containing enzymes Sublingual floor of the mouth Mostly mucous saliva Submandibular Opens on either side of the frenulum Mixture of watery (enzymes) and mucous secretions

14 Teeth Organs of mastication
Increase surface area that digestive enzymes can work on food 3 main sections: Crown: exposed portion; covered by enamel Neck: surrounded by the gingivae (gums) Root: fits into the alveolar process of the jaw (gomphosis)

15 Teeth Children - 20 teeth 16 teeth per jaw - 32 total (adult)
deciduous or primary 16 teeth per jaw - 32 total (adult) Incisors (4) blade shaped - used to tear food Canines (Cuspids) (2) Pointed teeth - used to tear food Premolars (Bicuspids) (4) 2 points - used to tear and grind food Molars (6) 4 points - used for grinding Last set called wisdom teeth


17 Esophagus Collapsible, muscular, mucous-lined tube
25cm; extends from pharynx to stomach Posterior to trachea Upper esophageal sphincter (UES) – prevents air from entering during respiration Lower esophageal sphincter or cardiac sphincter

18 Esophagus Esophageal hiatus – hole in the diaphragm through which the esophagus enters the abdominal cavity Enlargement results in lower portion of esophagus and stomach bulging upward into the chest  hiatal hernia Gastroesophageal reflux disease (GERD) – backward flow of stomach acid through the cardiac sphincter into the lower esophagus

19 Warm Up 3/9-10/11 Announcements: Make up test ASAP
No tutoring/make ups today after school Progress Report grades due this Friday Bring book & packet on Friday Warm Up: Name the 4 layers of the GI tract (inner to outer). List one fact about each layer. Name the 3 salivary glands. What type of saliva is produced from each? What is a hiatal hernia? On what areas of the tongue are taste buds found?

20 Warm Up 3/11/11 Announcements:
You need your book and packet – go get it. Warm Up: True/False: The layers of the GI tract and cell types are consistent from mouth to anus. Name 3 functions of the tongue. True/False: The tongue is poorly vascular. How does the number of teeth differ between children and adults?

21 3/21/11 Announcements: Welcome Back!! No warm up today
Packet due block day Quiz block day (covers chapter 25 notes through tomorrow) Practical Friday (cat digestive organs and labeling)

22 Stomach Elongated, pouch-like structure Mostly in LUQ
After eating the stomach walls distend; when empty size of large sausage In adults holds liters

23 Stomach Landmarks (fig 25-10)
Fundus – enlarged upper left portion Body – central portion Pylorus – lower portion Lower esophageal sphincter (also cardiac sphincter) Pyloric sphincter Lesser curvature Greater curvature


25 Modifications of the Stomach Wall
Gastric Muscosa Arranged into folds which allow for distention (Rugae) Contains gastric glands which are surrounded by gastric pits Gastric glands secrete gastric juice 3 major secretory cells: Chief cells: secrete enzyme of gastric juice Parietal cells: secrete hydrochloric acid (HCl) Endocrine cells: secrete ghrelin (stimulate hypothalamus to increase appetite) and gastrin (influences digestive functions)


27 Modifications of the Stomach Wall
Gastric Muscle Muscularis layer is composed of 3 smooth muscle layers Superficial to deep Longitudinal Circular Oblique Allows stomach to contract at many different angles


29 Modifications of the Stomach Wall
Serosa Layer Visceral layer forms the greater omentum (over intestines) and lesser omentum (connects stomach to liver)

30 Small Intestine 1 inch in diameter; 20 feet in length 3 divisions:
Duodenum 10 inches C shaped Jejunum 8 feet Begins where the sm. intestine turns forward and downward Ileum 12 feet

31 Walls of the Small Intestine
Mucosa lining has circular folds  plicae Small projections called villi (singular – villus) cover plicae 1 mm in height Contain an arteriole, venule and lymph vessel Epithelial cells on the surface of villi contain approx 1700 microvilli per cell Villi and microvilli increase surface area for absorption

32 Walls of the Small Intestine
Goblet cells are located on villi and in crypts Secrete mucus Secretory cells in each crypt produce an enzyme that prevents bacterial growth in the small intestine



35 Large Intestine 2.5 inches in diameter; 5-6 feet in length Divisions
Cecum Colon rectum

36 Divisions of the Large Intestine
Cecum First 2-3 inches of the large intestine Blind pouch in right quadrant

37 Divisions of the Large Intestine
Colon (4 divisions) Ascending Vertical position in right quadrant Ileum joins superior to cecum Ileocecal valve allows material to pass into the large intestine Transverse Horizontal position below liver, stomach & spleen Extends from the hepatic flexure to the splenic flexure

38 Divisions of the Large Intestine
Descending Vertical position in the left quadrant Extends to the level of the iliac crest Sigmoid colon Below iliac crest Means “s-shaped” Bends from L to R


40 Divisions of the Large Intestine
Rectum Last 7-8 inches of the large intestine Anal canal is the last inch Mucous lined vertical folds  anal columns Opening = anus


42 Walls of the Large Intestine
Intestinal mucous glands Secrete mucous that coats feces Longitudinal muscles are grouped into tape-like strips called taeniae coli Circular muscles are grouped into rings which form pouches  haustra Circular muscles in the rectum form rectal valves


44 3/22/11 Announcements: Packet due block day Quiz block day
Practical (identification & labeling) Friday Warm Up: The folds in the stomach which allow for distention are called: Name 3 modifications of the stomach wall. List the divisions of the small intestine from superior to inferior. The transverse colon extends from the _________ to the ___________. Name the 3 modifications in the small intestine which increase surface area (from largest to smallest).

45 Vermiform Appendix Attached to the cecum in the RLQ
3-4 inches in length “breeding ground” for intestinal or normal flora Nonpathogenic bacteria Aids in digestion and absorption

46 Appendicitis Mucous lining becomes inflamed
Fecal matter or food becomes trapped causing irritation and inflammation Rupturing of the appendix results in infectious materials in the abdominal cavity May cause infection of the peritoneum and/or other abdominal organs

47 Appendicitis S/S Nausea/vomiting RLQ pain (McBurney’s Point) Rebound tenderness An enlarged appendix can be removed through a laparoscopic surgical procedure

48 Peritoneum Continuous sheet of serous membrane
Lines walls of abdominal cavity (parietal layer) Outer layer of abdominal organs (visceral layer) Binds abdominal organs together Mesentery: projection of the parietal layer Attached to small intestine Allows free movement without becoming tangled (volvulus) Greater omentum: continuation of the stomach’s serosa layer Covers small intestines Lesser omentum Attaches from the liver to the stomach

49 Liver Largest gland in the body Weighs 3-4 pounds RUQ

50 Anatomy of the Liver Two lobes connected by the falciform ligament
Left lobe 1/6 the size of the right lobe 3 divisions of the right lobe Right lobe proper, caudate lobe and quadrate lobe (seen inferiorly) (fig 25-22)

51 Anatomy of the Liver

52 Anatomy of the Liver Hepatic lobules – anatomical units of the liver
Pentagon-shaped cylinders Blood enters the lobules from the hepatic artery & hepatic portal vein Arterial blood oxygenates Venous blood passes for inspection Kupffer cells remove bacteria, old RBCs, dissolved toxins Venous blood continues to the inferior vena cava Bile formed by hepatic cells passes though the canaliculi to the bile ducts

53 Fig 25-23, page 758

54 Bile Ducts Small bile ducts merge to form R and L hepatic ducts
R and L hepatic ducts form common hepatic duct Cystic duct and common hepatic duct form common bile duct Common bile duct opens into the duodenum Fig 25-25

55 Bile Ducts

56 Liver Functions Detoxification
Bile secretion (aids in the absorption of fats) Protein, fat and carbohydrate metabolism Hematopoisesis (blood cell production)

57 Gallbladder Pear-shaped sac 3-4 inches long Can hold 30-50mL of bile
Located on inferior surface of the liver Rugae (similar to stomach) Functions: Stores and concentrates bile Contracts and ejects bile into duodenum during digestion

58 Cholecystitis Inflammation of the gallbladder
Often caused by gallstones (cholelithiasis) Solid precipitants; mostly cholesterol High incidence in obese individuals and those undergoing rapid weight loss Treatment: Laparoscopic cholecystectomy Ultrasound lithotripsy Oral medications (Actigall)


60 Pancreas 6-9 inches long LUQ; behind stomach extending to the spleen
Endocrine & Exocrine tissue Exocrine tissue arranged in a compound acinar formation (grapelike) Release digestive enzymes into microscopic ducts which join to the main pancreatic duct Pancreatic duct empties into the duodenum


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