1. Final Review Part II

2. Salivary Glands Saliva contains salivary amylase—begins digestion of carbohydrates 2

3. Wall of the Digestive Tract Lumen—hollow space within the “tube” of the digestive tract Tissue layers of the wall of the digestive tube from inside to outside – Mucosa—mucous epithelium – Muscularis peristalsis – Muscularis —two layers of smooth muscle that move food through the tube by rhythmic muscular waves known as peristalsis 3

4. Wall of the Digestive Tract Tissue layers (cont’d) – Serosa – Serosa —serous membrane that covers the outside of abdominal organs visceral peritoneum in abdominal cavity Composed of visceral peritoneum in abdominal cavity It attaches the digestive tract to the wall of the abdominopelvic cavity by forming folds called mesenteries 4

5. Small Intestine About 7 m (20 feet) long but only 2 cm or so in diameter Divisions – Duodenum – Jejunum – Ileum Wall—contains smooth muscle fibers that contract to produce peristalsis 5

6. Liver and Gallbladder Liver – Ducts Hepatic —drains bile from liver Cystic —duct by which bile enters and leaves gallbladder Common bile —formed by union of hepatic and cystic ducts and drains bile from hepatic or cystic ducts into duodenum Gallbladder – Location—undersurface of the liver – Function—concentrates and stores bile produced in the liver 6

7. Disorders of the Liver and Gallbladder Gallstones—calculi (stones) made of crystallized bile pigments and calcium salts – Cholelithiasis —condition of having gallstones – Cholecystitis —inflammation of the gallbladder; may accompany cholelithiasis – Stones can obstruct bile canals, causing jaundice 7

8. Pancreas Location—behind stomach Functions – Pancreatic cells secrete pancreatic juice into pancreatic ducts; main duct empties into duodenum – Pancreatic islets (of Langerhans)—cells not connected with pancreatic ducts; secrete hormones glucagons and insulin into the blood – Why is pancreatic juice the most important digestive juice? It contains enzymes that digest all three major kinds of food (carbohydrates, fats, proteins). 8

9. Digestion Carbohydrate digestion —mainly in small intestine – Pancreatic amylase—changes starches to maltose – Intestinal juice enzymes Maltase—changes maltose to glucose Sucrase—changes sucrose to glucose Lactase—changes lactose to glucose 9

10. Digestion Protein digestion Protein digestion —starts in stomach; completed in small intestine – Gastric juice enzymes, rennin and pepsin, partially digest proteins – Pancreatic enzyme, trypsin, completes digestion of proteins to amino acids – Intestinal enzymes, peptidases, complete digestion of partially digested proteins to amino acids 10

11. Digestion Fat digestion – Bile contains no enzymes but emulsifies fats (breaks fat droplets into very small droplets) – Pancreatic lipase changes emulsified fats to fatty acids and glycerol in small intestine 11

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13. Disorders of the Stomach Pylorospasm—abnormal spasms of the pyloric sphincter – Common in infants – Pyloric stenosis is similar abnormality— obstructive narrowing of the pyloric opening Ulcers—open wounds caused by acid in gastric juice – Often occurs in duodenum or stomach – Associated with infection by the bacterium Helicobacter pylori and use of NSAIDs – Current treatment involves triple therapy 13

14. Terms to Know Large Intestine Pancreas Liver Stomach Esophagus Salivary Glans Gallbladder Mouth Pharynx Small Intestine

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16. Cells of the Nervous System Neurons – Consist of three parts Cell body of neuron—main part Dendrites Dendrites —branching projections that conduct impulses to cell body of neuron Axon—elongated projection that conducts impulses away from cell body of neuron 16

17. Cells of the Nervous System Neurons Neurons classified according to function or direction of impulse Sensory neurons: conduct impulses to the spinal cord and brain; also called afferent neurons Motor neurons: conduct impulses away from brain and spinal cord to muscles and glands; also called efferent neurons Interneurons: conduct impulses from sensory neurons to motor neurons; also called central or connecting neurons 17

18. Cells of the Nervous System Glia (neuroglia) Support cells, bringing the cells of nervous tissue together structurally and functionally Astrocytes—star-shaped cells that anchor small blood vessels to neurons Microglia —small cells that move in inflamed brain tissue carrying on phagocytosis myelin sheaths Oligodendrocytes —form myelin sheaths on axons in the CNS (Schwann cells form myelin sheaths in PNS only) 18

19. Cells of the Nervous System Disorders of nervous tissue – Multiple sclerosis —characterized by myelin loss in central nerve fibers and resulting conduction impairments – Tumors General name for nervous system tumors is neuroma Most neuromas are gliomas, glial tumors Multiple neurofibromatosis—characterized by numerous benign tumors 19

20. Reflex Arcs The simplest reflex arcs are two-neuron arcs The simplest reflex arcs are two-neuron arcs —consisting of sensory neurons synapsing in the spinal cord with motor neurons; three-neuron arcs consist of sensory neurons synapsing in the spinal cord with interneurons that synapse with motor neurons 20

21. The Synapse Definition—the place where impulses are transmitted from one neuron to another (the postsynaptic neuron) Synapse made of three structures—synaptic knob, synaptic cleft, and plasma membrane Neurotransmitters bind to specific receptor molecules in the membrane of a postsynaptic neuron, opening ion channels and thereby stimulating impulse conduction by the membrane 21

22. Terms to Know microglia axon dendrites oligodendrocyte afferent neuron astrocytes efferent neuron interneurons nodes of Ranvier Schwann cells

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