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BIOL 1410 (94)

Digestive System

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University of Manitoba
Biological Sciences
BIOL 1410
Jennifer Mcleese

Digestive System May-16-13 10:54 AM Gastrointestinal GI Tract  Tube from mouth to anus Accessory Organs  Teeth, tongue, salivary glands, pancreas, liver, gall bladder Functions:  Ingestion  Digestion Digestion 1. Mechanical/ Motility o Chewing 2. Chemical o Enzymes o Acid / secretions 3. Absorption o End products of digestion enter blood or lymph 4. Defecation o Undigested material and waste Know: Quadrants figure 1.11 Abdominal and Pelvic Regions 1.12 Enteric Nervous System  Nerve network within the wall of the tube  Little brain Muscularis = muscularis externa Submucosal Plexus  Regulates function of mucosal glands and muscle Myenteric Plexus  Regulates motility of muscularis externa  Communicates with central nervous system Peritoneum  Serous membrane (largest) abdominal  Visceral (on organ wall) and parietal (lines abdominal cavity wall) Peritoneal Cavity: Contains serous fluid Serosa Between Organs  Sheet of 2 fused layers of visceral peritoneum  Contains blood and lymph vessels, nerves  Provides stability to hold organs in place  Allows movement  Binds organs to cavity wall, each other 1. Greater Omentum o Fatty apron o Over transverse colon, small intestine (protection, insulation, energy reserve) 2. Lesser Omentum o Suspends stomach from liver 3. Mesentery (Parietal) o Binds intestines to abdominal wall Histology of the Gastrointestinal Tract  4 layers (esophagus to anal canal)  Similar layers in hollow organs of urinary respiratory reproductive systems 1. Serosa/Adventitia o Serosa on stomach, lower small intestine, liver, gall bladder, most of large intestine o Organs covered on anterior surface by peritoneum (retro peritoneum) pancreas, duodenum o Posterior surface is CT only o No epithelium = adventitia o Adventitia (tunica externa) only - esophagus through mediastinum 2. Muscularis Externa o Visceral smooth muscle o Non striated (no myofibrils or sarcomere) o Spindle shaped cells with central nucleus o Occurs in sheets and functions as unit o Gap junctions between cells o Contractions of smooth muscle responsible for motility (movement of food and mixing) o Inner circular and outer longitudinal layer o Myenteric plexus between those layers 3. Submucosa o CT (Areolar) binds mucosa to Muscularis externa o Blood and lymph vessels oSubmucosal nerve plexus 4. Mucosa (Mucous Membrane) oInnermost oFaces exterior = lumen o Muscularis Mucosa  Next to submucosa  Smooth muscle allows movement of mucosa oLamina Propria  Areolar  Has blood and lymph vessels and lymph nodules/tissues (immune) c.Mucous Epithelium  Goblet cells  Stratified squamous in esophagus, mouth and pharynx, anal canal  Simple columnar (stomach, small, large intestine) Mouth  Oral cavity includes lips, cheeks, tongue  Wall is skeletal muscle, lined by mucous membrane a. Tongue  Skeletal muscle  Attached to hyoid bone  Dorsal surface/superior covered with... 1. Papillae:  Projections of mucosa  3 types, some have taste buds 2. Lingual Glands  Release fluid and enzyme lingual lipase (fat digestion) b. Palate  Hard anterior: Maxilla + palatine bones  Soft posterior: Uvula post. Projection  Both rise to close nasal pharynx while swallowing c. Major Salivary Glands Outside Mouth  Parotid inferior  Anterior to ears  Thin saliva rich in amylase, no mucous Submandibular  Mix of fluid, amylase, and mucous iii. Sublingual  Below  Tongue on floor of mouth  Mostly mucous d.Teeth  In maxillae + mandible  Mechanical digestion  Child = primary = deciduous  Adult = secondary dentition/permanent Classification: Central Incisor: 1 in each quadrant Lateral incisor: 1 in each quadrant Canine: 1 in each quadrant Premolars: 2 for adults Molars: 2 in child 3 in adult  20 teeth in child 32 in adult Structure: Crown = dentin with enamel overlay above gum Neck = boundary where enamel + cementum meet at gum level Root = dentin with cementum overlay Periodontal Ligaments: Attach roots to jaw bones Pulp cavity = enclosed by dentin Pulp = CT, Blood + lymph vessels, nerves Root canal = extension of pulp cavity into root Dentin = calcified CT similar to bone may have cells Enamel = Acellular calcium phosphate salts Cementum = calcified CT Pharynx  Oropharynx and laryngopharynx are muscular externa skeletal Muscle  mucosa = strat. Squamous Esophagus  Dorsal(behind) trachea in mediastinum no
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