final review part ii. salivary glands saliva contains salivary amylase—begins digestion of...
TRANSCRIPT
Final Review Part II
Salivary Glands
• Saliva contains salivary amylase—begins digestion of carbohydrates
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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—two layers of smooth muscle that move food through the tube by rhythmic muscular waves known as peristalsis
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Wall of the Digestive Tract
• Tissue layers (cont’d)–Serosa—serous membrane that covers the
outside of abdominal organs• Composed of visceral peritoneum in abdominal
cavity• It attaches the digestive tract to the wall of the
abdominopelvic cavity by forming folds called mesenteries
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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
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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
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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
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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).
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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
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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
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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
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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
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Terms to Know
• Large Intestine • Pancreas• Liver• Stomach• Esophagus• Salivary Glans• Gallbladder• Mouth• Pharynx• Small Intestine
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Cells of the Nervous System
• Neurons–Consist of three parts• Cell body of neuron—main part
•Dendrites—branching projections that conduct impulses to cell body of neuron• Axon—elongated projection that conducts
impulses away from cell body of neuron
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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 neurons17
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•Oligodendrocytes—form myelin sheaths on axons
in the CNS (Schwann cells form myelin sheaths in PNS only)
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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
Reflex 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
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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
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Terms to Knowmicrogliaaxondendritesoligodendrocyteafferent neuronastrocytesefferent neuroninterneuronsnodes of RanvierSchwann cells
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