Answers and Explanations

1. Answer: A. In a lumbar puncture, which is used to sample CSF, the needle must enter the subarachnoid space by last crossing the arachnoid mater. Pericardiocentesis is performed after the needle crosses the parietal layer of serous pericardium, which is deep to fibrous pericardium. Thoracocentesis is performed after the needle traverses the parietal pleura. Culdoscopy is performed after an endoscope traverses the parietal peritoneum lining the rectouterine pouch of Douglas. A pudendal block anesthetizes the pudendal nerve after it has emerged from the greater sciatic foramen.

2. Answer: B. The ligamentum flava unite the laminae of adjacent vertebrae and would be pierced in an off-midline lumbar puncture. The posterior and Longitudinal ligaments are found on the corresponding side of the bodies and discs of vertebrae and are outside the dural sac. The denticulate ligament and the filum terminale are pial extensions that help stabilize the spinal cord. Neither would have to be pierced in a lumbar puncture.

3. Answer: D. Branches of the vagus nerves provide preganglionic parasympathetic innervation to terminal ganglia in the midgut by following branches of the arterial blood supply to the midgut, which is provided by the superior mesenteric artery. Pelvic splanchnic nerves increase peristalsis and glandular secretion in the hindgut. The other choices provide sympathetic innervation to gut structures, which inhibits peristalsis and glandular secretion.

4. Answer: B. The pterygopalatine ganglion provides postganglionic parasympathetic innervation to the lacrimal gland and to mucous glands of the oral and nasal cavities. The otic ganglion innervates the parotid gland, the ciliary ganglion innervates the ciliary and constrictor pupillae muscles, the superior cervical ganglion provides sympathetic innervation to the face scalp and orbit, and axons from the submandibular ganglion innervate the submandibular and sublingual salivary glands.

5. Answer: B. The spinal nerves affected by lumbar disc herniation between L4 and L5 might be the L5 and Si spinal nerves. The L4 spinal nerve exits between L4 and L5 but is spared because it passes through the intervertebral foramen superior to the site of the herniation. The bladder and rectum are controlled by the S2, S3, and S4 spinal cord segments and are less likely to be unaffected. The L3 dermatome would not be affected, but the SI dermatome might show some paresthesia The quadriceps femoris muscle, which is the sole extensor of the leg at the knee, is innervated by the L2—L4 spinal cord segments and would not be affected.

6. Answer: B. A lumbar midline cyst containing CSF and no neural tissue is classified as spina bifida cystica with meningomyelocele. Spina bifida occulta is asymptomatic, Arnold Chiari formations are downward herniations of the cerebellum through the foramen magnum, spins bifida defects are caudal neuropore problems, and a cystocele is a herniation of the bladder into the vagina.

Thorax

CHEST WALL

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Essentials of Human Physiology

Essentials of Human Physiology

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