The Digestive System

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  1. The Digestive System
    • ingestion-selective intake of food
    • digestion-mechanical and chemical breakdown of food into a form usable by the body
    • absorption-uptake of nutrients into the blood and lymph
    • compatction-absorbing water and consolidating the indigestible residue into feces
    • defecation- elimination of feces
  2. digestive tract
    • muscular tube from mouth to anus
    • includes mouth, pharynx, esophagus, stomach, small intestine, and large intestine
  3. basic structural plan of the digestive tract
    • Mucosa
    • epithelium
    • lamina propria
    • muscularis mucosae
    • Submucosa
    • Muscularis externa
    • Circular Layer
    • Longitudinal layer
    • Serosa
    • Areolar Tissue
    • Mesothelium
  4. Acessory Organs
    • teeth
    • tongue
    • salivary glands
    • liver
    • gallbladder
    • pancreas
  5. Mucosa
    • Aka Mucous membrane
    • inner lining of digestive tract
    • consists of epithelium, thing layer of smooth muscle (lamina propria), and thin layer of smooth muscle (muscularis mucosae)
  6. submucosa
    thicker layer of loose conjnective tissue containing blood vessels, lymphatic vessels, a nerve plexus, and in some places mucous glands
  7. Muscularis mucosae
    • tenses the mucosa, creating grooves and ridges that enhance its surface area and contact with food
    • improves efficiency of the digestion and nutrient absorption
  8. muscularis externa
    • usually two layers of smooth muscle near the outer surface of DT
    • responsible for paristalsis and other forms of motility that mix food and digestive enzymes and propel material through the tract
  9. serosa
    • composed of a thin layer of areolar tissue topped by simple squamous mesothelium
    • esophagus-right before rectum
  10. adventitia
    • fibrous connective tissue that surround mosth of esophagus, pharyx and rectum
    • substitute for serosa
  11. enteric nervous system
    • snesory neaurons that monitor tension in the gut wall; interneurons; and motor neurons that activate such effectors as smooth muscle and gland cells of the gut
    • esophagus, stomach and intestines own nervous network
    • can function independently from extensive innervation from CNS
  12. submucosal (Meissner) plexus
    • in submucosa
    • controls movements of the muscularis mucosae and glandular secretion of the mucosa
  13. myenteric plexus
    • between layers of the muscularis externa
    • innervate the muscularis externa and pass through its inner circular layer and contribute to the submucosal plexus
  14. short (myenteric) reflex arcs
    fibers that carry signals to region of the gastrointestinal tract contained int e myenteric plexus
  15. long (vagovagal) reflex arcs
    fibers carry signals to the central nervous system predominantly the vagus nerves
  16. foregut
    mouth, pharynx, esophagus, stomach, and beginning of the duodenum
  17. esophageal arteries
    • arteries that go to esophagus
    • coming from thoracic aorta
  18. celiac trunk
    delivers blood to the foregut
  19. midgut
    begins at the opening of the bule duct and includes rest of duodenum, jejunum and ileum and the large intestine as far ass the first 2/3s of the transverse colon
  20. superior mesenteric artery
    delivers blood to midgut
  21. hindgut
    last third of large intestine, from end of the transverse colon through the anal canal
  22. inferior mesenteric artery
    supplies blood to hindgut
  23. hepatic portal vein
    • blood from entire tract below the diaphragm drians into here
    • then enters liver
  24. hepatic portal system
    • routes all blood from the stomach and intestines as well as from some other abdominal viscera, through the liver before returning it to the general circultion
    • has two capillary networks in series
  25. mesenteries
    • hold the abdominal viscera in their proper relationhip to each other and prevent the small intestine, especially, from becoming twisted and tangled by changes in body position
    • provide passage for blood vessels and nerves
  26. posterior mesentery
    translucent 2-layered membrane extending to the digestive tract
  27. anterior mesentery
    two layers of posterior mesentery seprate and pass around opposite sides of organ and come together again on far side of organ
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The Digestive System
The Digestive System
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