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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