Answers and Explanations

1. Answer: A. Defects in the body wall including all forms of spina cystica present with elevated levels of the alpha-fetoprotein in amniotic fluid. Clubfoot and pulmonary hypoplasia are seen in stillborn infants with oligohydramnios. A tuft or hair in skin over the defect is seen only in spina bifida occulta.

2. Answer: C. Anencephaly, the result of a failure of the rostral neuropore to close, will be accompanied by polyhydramnios in utero. With improper formation of rostral end of the brain, the fetus lacks the neural mechanism for swallowing and cannot reduce the amount of amniotic fluid in the amniotic sac.

Answer: C. The infant has a meningocele, which is a form of spina bifida cystica where the dura and arachnoid layers protrude through the defect. Deep to the arachnoid, an extension of the subarachnoid space in the cyst will contain cerebrospinal fluid.

Answer: A. All preganglionic sympathetic axons everywhere in the body, including those that synapse with chromaffin cells in the adrenal medulla, utilize acetylcholine as their n eurotr an sm itte r.

Answer: A, A lesion at the level of the cervical spinal cord might affect the descending hypothalamic fibers, which control all preganglionic sympathetic neurons, including those that provide sympathetic innervation to the face, scalp, and orbit.

Answen B. The basal plate of the neural tube gives rise to motor neurons in the spinal cord and the brainstem. The only motor structure on the List is the substantia nigra, which is part of the basal ganglia and is found in the midbrain.

Answer: B. The adenohypophysis is derived from an outgrowth of oral ectoderm called Rathke's pouch. All other choices are derived from the diencephalon of the neural tube.

Answer: C. Hair cells in the vestibular and cochlear end organs are derived from ectoderm.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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