Ch. 15 The Special Senses

Marieb, Hoehn11th EditionHuman Anatomy & PhysiologyISBN: 9780136874034Non è quello che usi tu?Cambia libro di testo
Capitolo 15, Problema 31
Assume that a tumor in the pituitary gland or hypothalamus is protruding inferiorly and compressing the optic chiasma. What could be the visual outcome?
Guida verificata passo dopo passo1
Step 1: Understand the anatomical relationship between the pituitary gland, hypothalamus, and the optic chiasma. The optic chiasma is located just above the pituitary gland, where the optic nerves partially cross.
Step 2: Recognize that compression of the optic chiasma typically affects the crossing fibers from the nasal (medial) halves of both retinas. These fibers carry visual information from the temporal (lateral) visual fields of each eye.
Step 3: Recall that damage to the crossing fibers in the optic chiasma results in loss of peripheral vision on both sides, a condition known as bitemporal hemianopsia.
Step 4: Connect the tumor's inferior protrusion compressing the optic chiasma to the expected visual deficit, which is loss of the outer (temporal) visual fields in both eyes.
Step 5: Summarize that the visual outcome of such compression would be bitemporal hemianopsia, characterized by loss of peripheral vision bilaterally, while central vision remains intact.
Concetti chiave
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Anatomy of the Optic Chiasma
The optic chiasma is the X-shaped structure where the optic nerves partially cross. It lies just above the pituitary gland and hypothalamus. Understanding its location is crucial because compression here can affect visual pathways, leading to specific visual field defects.
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Optic Components
Visual Pathway and Field Defects
The optic chiasma contains crossing fibers from the nasal halves of both retinas, which correspond to the temporal visual fields. Compression of these fibers typically causes bitemporal hemianopia, a loss of peripheral vision on both sides.
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Percorso guidato
Alternative Pathway
Effects of Pituitary or Hypothalamic Tumors
Tumors in the pituitary gland or hypothalamus can grow upward and compress the optic chiasma from below. This mechanical pressure disrupts nerve signal transmission, often resulting in characteristic visual disturbances such as bitemporal hemianopia.
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The Hypothalamus and Pituitary Gland Example 2
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