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Chapter 23: The Digestive System - Coggle Diagram

- - - - Mucosa
        
        Innermost layer
        
        Consists of:
        
        Epithelium
        
        Lamina propria
        
        Muscular mucosal
      - Submucosa
        
        External to the mucosa
        
        Contains blood & lymphatic vessels, nerve fibers
      - Muscularis Externa
        
        External to submucosa
        
        2 layers:
        
        Circular muscular: inner layer
        
        Longitudinal muscular: outer layer
        
        Serosa is the outermost layer
        
        This is the visceral peritoneum
    - - Longitudinal Layer
        
        Parallel to long axis of organ
      - Circular Layer
        
        Deeper layer
        
        Fibers run around circumference of organ
    - - Mouth (Oral Cavity)
        
        Mucosa-lined cavity
        
        Boundaries are:
        
        Lips anteriorly
        
        Cheeks laterally
        
        Palate superiorly
        
        Tongue inferiorly
        
        Fauces of oropharynx posteriorly
        
        Lips & Cheeks
        
        Formed by orbicularis oris & buccinator muscles, respectively
        
        Anatomy of Mouth
        
        Labial frenulum
        
        Connects lips to gum
        
        Palate
        
        Forms the roof of the mouth
        
        Mucosal Layer
        
        Stratified squamous epithelium
        
        Lamina propria
      - Pharynx
        
        Oropharynx & laryngopharynx
        
        Passages for air & food
        
        Lined with stratified squamous epithelium
        
        External muscle layer
      - Esophagus
        
        Gross Anatomy
        
        Muscular tube
        
        Begins as continuation of the pharynx
        
        Joins the stomach inferior to the diaphragm
        
        Cardiac sphincter closes lumen to prevent stomach acid from entering esophagus
        
        Microscopic Anatomy
        
        Epithelium is nonkeratinized stratified squamous epithelium
        
        When empty, mucosa & submucosa are in longitudinal folds
        
        Mucous glands
        
        Muscularis Externa
        
        Skeletal muscle
        
        First 1/3 of length
        
        Mix of skeletal + smooth muscle
        
        Middle 1/3 of length
        
        Smooth muscle
        
        Inferior 1/3 of length
        
        Adventitia
        
        Most external layer of esophagus
    - - Stomach
        
        Site where food is churned into chyme
        
        Secretion of pepsin begins protein digestion
        
        Functions under acidic conditions
        
        Food remains in stomach approx. 4 hours
        
        Regions of stomach: cardial part, fungus, body, pyloric part
        
        Microscopic Anatomy
        
        Muscularis has 3 layers
        
        Circular & longitudinal layers and oblique layer
        
        Epithelium is simple columnar epithelium
        
        Mucosa dotted with gastric pits
        
        Gastric glands are deep to gastric pits
        
        Gastric Glands
        
        Gastric glands of fundus & body consist of
        
        Mucous neck cells
        
        Secrete a special mucus
        
        Parietal cells
        
        Secrete HCl & gastric intrinsic factor
        
        Stomach has its own mucus lining to protect itself from the acid it produces/contains
        
        Intrinsic factor is needed for B12 absorption, which is needed for RBC production
        
        Chief cells
        
        Secrete pepsinogen
        
        Pepsinogen is activated to pepsin when it encounters acid in the gastric glands
      - Small Intestine
        
        Gross Anatomy
        
        Longest portion of the alimentary canal
        
        Site of most enzymatic digestion & absorption
        
        3 subdivisions
        
        Duodenum
        
        Jejunum
        
        Ileum
        
        Innervation
        
        Parasympathetic fibers from vagus nerve
        
        Sympathetic from thoracic splanchnic nerves
        
        Duodenum
        
        Receives digestive enzymes & bile
        
        Main pancreatic duct & common bile duct enter duodenum
        
        Sphincter's control entry of bile & pancreatic juices
        
        Microscopic Anatomy
        
        Many modifications for absorption
        
        Circular Folds
        
        Transverse ridges of mucosa & submucosa
        
        In each fold, there are more folds
        
        Villi
        
        Fingerlike projections of the mucosa
        
        Covered with simple columnar epithelium
        
        Further magnify surface area
        
        In each villas, there's a lacteal (lymphatic vessel) & a blood vessel
        
        Fatty content is absorbed into the lacteal
        
        Amino acids are absorbed into the blood
        
        Microvilli
        
        Further increase surface area for absorption
      - Large Intestine
        
        Digested residue contains few nutrients
        
        Small amount of digestion by bacteria
        
        Main functions: absorb water & electrolytes
        
        Mass peristaltic movements force feces toward the rectum
        
        Bacterial fermentation in the gut produces gas
        
        Gross Anatomy
        
        Subdivided into cecum, appendix, colon, rectum, anal canal
        
        Special Features of Large Intestine
        
        Teniae Coli
        
        Thickening of longitudinal muscular externa
        
        Haustra
        
        Puckering created by teniae coli
        
        Epiploic Appendages
        
        Fat-filled pouches of visceral peritoneum
        
        Cecum
        
        Blind pouch
        
        Beginning of large intestine
        
        Appendix
        
        Contains lymphoid tissue
        
        Safe haven for the beneficial bacteria
        
        Colon
        
        Divided into distinct segments
        
        Ascending, transverse, descending & sigmoid colon
        
        Right colic/hepatic flexure
        
        Left colic/splenic flexure
        
        Rectum
        
        Descends along the inferior half of the sacrum
        
        Anal Canal
        
        The last subdivision of the large intestine
        
        Lined with stratified squamous epithelium
        
        Microscopic Anatomy
        
        Villi are absent
        
        Contains numerous goblet cells
        
        Produce mucus to help lubricate the large intestine
        
        Intestinal crypts are simple tubular glands
        
        Lined with simple columnar epithelial tissue
        
        Epithelium changes at anal canal
        
        Becomes stratified squamous epithelium
  - - - Intrinsic Muscles
        
        Within the tongue
      - Extrinsic Muscles
        
        External to the tongue
      - Lingual Frenulum
        
        Secures tongue to floor of mouth
      - Superior Surface of the Tongue
        
        Tongue papillae
        
        Filiform papillae
        
        No taste buds
        
        Fungiform papillae
        
        Vallate papillae
        
        Posterior 1/3 of tongue lies in oropharynx
        
        Lined with lingual tonsil
    - - Parotid Glands
        
        Parotid duct
        
        Parallel to zygomatic arch
      - Submandibular Glands
        
        Lie along medial surface of mandible
      - Sublingual Glands
        
        Lie in floor of oral cavity
        
        Contain primarily mucous cells
    - - Microscopic Anatomy
        
        Hepatocyte
        
        Functional cells of the liver
        
        Functions of hepatocytes:
        
        Rough ER manufactures blood proteins
        
        Smooth ER produces bile salts, detoxifies poisons
        
        Peroxisomes detoxify poisons (alcohol)
        
        Golgi apparatus packages secretory products
        
        Mitochondria provide energy for liver processes
        
        Glycosides store sugar
        
        Great capacity for regeneration
        
        Portal Triad
        
        Composed of:
        
        Bile duct tributary
        
        Branch of hepatic portal vein
        
        Branch of hepatic artery
        
        Hepatic Portal Vein
        
        Takes blood from digestive organs to clean it up before it goes to the heart
        
        Blood from digestive system has nutrients & toxins
        
        Stellate Macrphages
        Kupffer cells
        
        Destroy bacteria
    - - Cholecystokinin
        
        Released from enteroendocrine cells in response to fatty chyme
        
        A hormone that causes the smooth muscle walls of gallbladder to contract to secrete concentrated bile into the major duodenal papilla
    - - Function
        
        Exocrine Function
        
        Produces most enzymes that digest food in the small intestine
        
        Acinar cells make, store & secrete pancreatic enzymes
        
        Enzymes are activated in the duodenum
        
        Contents are secreted on a surface or a lumen
        
        In this case, the secretion (enzymes) is secreted into the lumen of duodenum
        
        Endocrine Function
        
        Produces insulin & glucagon
        
        Regulates blood sugar
      - Main Pancreatic Duct
        
        Extends the length of the pancreas
        
        Joins bile duct to form the hepatopancreatic ampulla
        
        Empties into duodenum
  - - - Peristalsis
        
        Major means of propulsion
        
        Adjacent segments of the alimentary canal relax & contract
        
        Wave-like movement
    - - Segmentation
        
        Rhythmic local constrictions of intestine
        
        Mixes food with digestive juices
- - - - Ventral Mesenteries
        
        Falciform Ligament
        
        Binds anterior part of liver to anterior abdominal wall
        
        Lesser Omentum
        
        Attaches liver to the lesser curvature of stomach
      - Dorsal Mesenteries
        
        Greater Omentum
        
        Connects greater curvature of stomach to posterior abdominal wall
        
        Transverse Mesocolon
        
        Holds transverse colon in place
        
        Sigmoid Mesocolon
        
        Connects the sigmoid colon to posterior pelvic wall