chapter 25.txt

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ginita
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chapter 25.txt
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2012-11-12 02:22:12
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digestive anatomy
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digestive anatomy
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  1. wall of the GI Tract
    Layers—GI tract is made of four layers of tissues: mucosa, submucosa, muscularis, and serosa.
  2. Lips
    covered externally by skin and internally by mucous membrane; are the junction between skin and mucous membrane is highly sensitive; when lips are closed, line of contact is oral fissure
  3. Cheeks
    lateral boundaries of oral cavity, continuous with lips and lined by mucous membrane; formed in large part by buccinator muscle covered by adipose tissue; contain mucus-secreting glands
  4. Hard Palate
    Hard palate consists of portions of four bones: two maxillae and two palatines
  5. Soft palate
    forms partition between the mouth and the nasopharynx and is made of muscle arranged in an arch. Suspended from midpoint of posterior border of the arch is the uvula (it helps prevent liquid & food from entering nasal cavity)
  6. Tongue
    • solid mass of skeletal muscle covered by a mucous membrane; extremely maneuverable (Figure 25-4)
    • •Important for mastication and deglutition
    • •Has three parts: root, tip, and body
    • •Papillae located on dorsal surface of tongue (roughness of the dorsal surface of the tongue is due to filiform Papillae)
    • •Lingual frenulum anchors tongue to floor of mouth
  7. Salivary glands
    • three pairs of compound tubuloalveolar glands (Figure 25-6) secrete approximately 1 liter of saliva each day; buccal glands contribute less than 5% of total salivary volume but provide for hygiene and comfort of oral tissues
    • –Parotid glands —largest of the paired salivary glands; produce watery saliva containing enzymes
    • –Submandibular glands —compound glands that contain enzyme and mucus-producing elements
    • –Sublingual glands —smallest of the salivary glands; produce a mucous type of saliva
  8. Crown
    —exposed portion of a tooth, covered by enamel; ideally suited to withstand abrasion during mastication
  9. Neck
    narrow portion that joins the crown to the root; surrounded by the gingivae
  10. Root
    fits into socket of alveolar process and is suspended by fibrous periodontal membrane
  11. Outer shell contains two additional tissues: dentin and cementum
    • -Dentin makes up the greatest portion of the tooth shell; at crown, covered by enamel, and at neck and root, covered by cementum
    • –Pulp cavity—located in dentin, contains connective tissue, blood, and lymphatic vessels and sensory nerves
  12. Teeth
    • - Deciduous teeth —20 baby teeth, which appear early in life
    • - Permanent teeth —32 teeth, which replace the deciduous teeth
  13. Pharynx
    Tube through which a bolus passes when moved from the mouth to the esophagus by the process of deglutition
  14. Esophagus
    • •Tube that extends from the pharynx to the stomach
    • •First segment of digestive tube
  15. Cardiac opening
    junction between the esophagus and the stomach
  16. Fundus
    enlarged portion to the left and above the opening of the esophagus into the stomach
  17. Body
    central portion of the stomach
  18. Pylorus
    lower part of the stomach
  19. lesser curvature
    upper right curve of stomach
  20. greater curvature
    lower left curve of stomach
  21. sphincter muscles
    • circular muscle fibers arranged so that there is an opening in the center when relaxed and no opening when contracted
    • -lower esophageal sphincter (LES) or cardiac sphincter controls opening of esophagus into stomach
    • - pyloric sphincter controls outlet of pyloric portion of stomach into duodenum
  22. gastric mucosa
    • •Epithelial lining has rugae marked by gastric pits (Figures 25-11 and 25-12)
    • •Gastric glands —found below level of the pits; secrete most of gastric juice
  23. Chief cells
    secretory cells found in gastric glands; secrete the enzymes of gastric juice (pepsinogen)
  24. Parietal( Oxyntic) cells
    secretory cells found in gastric glands; secrete Gastric acid (hydrochloric acid); thought to produce intrinsic factor needed for vitamin B12 absorption
  25. Endocrine cells
    secrete gastrin and ghrelin
  26. gastric muscularis
    thick layer of muscle with three distinct sublayers of smooth muscle tissue arranged in a crisscrossing pattern; this pattern allows stomach to contract strongly at many angles
  27. Functions of the stomach
    • –Reservoir for food until it is partially digested and moved further along GI tract
    • –Secretes gastric juice to aid in digestion of food
    • –Breaks food into small particles and mixes them with gastric juice
    • –Secretes intrinsic factor
    • –Limited absorption
    • –Produces gastrin and ghrelin
    • –Helps protect body from pathogenic bacteria swallowed with food
  28. small intestine
    Size and position of the small intestine—tube approximately 2.5 cm in diameter and 6 m in length; coiled loops fill most of abdominal cavity
  29. Divisions of the small intestine
    • –Duodenum —uppermost division; approximately 25 cm long, shaped roughly like the letter C
    • –Jejunum —approximately 2.5 m long
    • –Ileum —approximately 3.5 m long
  30. Wall of the small intestine
    • –Intestinal lining has plicae with villi
    • –Villi—important modifications of mucosal layer
    • •Each villus contains an arteriole, venule, and lacteal
    • •Covered by a brush border made up of 1,700 ultrafine microvilli per cell
    • •Villi and microvilli increase surface area of small intestine hundreds of times for absorption
  31. Large Intestine
    • Cecum
    • Colon
  32. Cecum
    first 5 to 8 cm of large intestine, blind pouch located in lower right quadrant of abdomen
  33. Colon
    • •Ascending colon —vertical position on right side of abdomen; ileocecal valve prevents material passing from large intestine into ileum
    • •Transverse colon passes horizontally across abdomen, above small intestine; extends from hepatic flexure to splenic flexure
    • •Descending colon —vertical position on left side of abdomen
    • •Sigmoid colon joins descending colon to rectum
    • •Rectum —last 7 or 8 inches of intestinal tube; terminal inch is anal canal with opening called the anus (Figure 25-17)
  34. Vermiform Appendix
    Accessory organ of digestive system; 8 to 10cm in length; communicates with cecum
  35. Peritoneum
    • •Large, continuous sheet of serous membrane (Figure 25-20)
    • •Made up of parietal and visceral layers
  36. Tranverse mesocolon
    —extension of peritoneum that supports transverse colon
  37. Mesentery
    A fan-shaped projection of parietal peritoneum; allows free movement of each coil of the intestine and helps prevent strangulation of the long tube (Figure 25-21)
  38. Liver
    • Location and size of the liver (Figure 25-22)— largest gland in body, weighs approximately 1.5 kg; lies under diaphragm; occupies most of right hypochondrium and part of epigastrium
    • •Liver lobes and lobules—two lobes separated by falciform ligament
  39. Left lobe
    forms about 1/6 of of liver
  40. right lobe
    forms about 5/6 of liver; divides into right proper, caudate lobe, and quadrate lobe
  41. hepatic lobules
    —anatomical units of liver; small branch of hepatic vein extends through the center of each lobule (Figure 25-23) Slide
  42. Common hepatic duct
    Right and left hepatic ducts immediately join to form one hepatic duct
  43. common bile duct
    Common hepatic duct merges with cystic duct to form common bile duct, which opens into 2nd part of the duodenum (greater doudenal papilla)
  44. Functions of the liver
    • Detoxification by liver cells—ingested toxic substances and toxic substances formed in intestines may be changed to nontoxic substances
    • –Bile secretion by liver—bile salts are formed in liver from cholesterol and are the most essential part of bile; liver cells secrete approximately 1 pint of bile per day
    • –Liver metabolism carries out numerous important steps in the metabolizing of proteins, fats, and carbohydrates
    • –Storage of substances such as iron and some vitamins
    • –Production of important plasma proteins
  45. Gallbladder
    • Size and location of the gallbladder—pear-shaped sac from 7 to 10 cm long and 3 cm wide at its broadest point; holds 30 to 50 ml of bile; lies on undersurface of liver
    • •Structure of gallbladder—serous, muscular, and mucous layers compose the gallbladder wall; mucosal lining has rugae
  46. Functions of gallbladder:
    • –Storage of bile
    • –Concentration of bile fivefold to tenfold
    • –Ejection of the concentrated bile into duodenum
  47. Pancreas
    • •Size and location of the pancreas—grayish pink–colored gland; 12 to 15 cm long; weighs approximately 60 g; runs from duodenum and behind stomach to spleen
    • •Structure of the pancreas (Figure 25-27) —composed of endocrine and exocrine glandular tissue
    • –Exocrine portion makes up majority of pancreas; has a compound acinar arrangement; tiny ducts unite to form main pancreatic duct, which empties into duodenum
    • –Endocrine portion—embedded between exocrine units; called pancreatic islets; constitute only 2% of total mass of pancreas; made up of alpha cells and beta cells; pass secretions into capillaries
  48. Functions of the pancreas
    • •As an exocrine gland:
    • –Acinar units secrete digestive enzymes
    • •As an endocrine gland:
    • –Beta cells secrete insulin (it ↓ blood glucose level)
    • –Alpha cells secrete glucagon (it ↑ blood glucose level)

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