Multiple Choice
Different animal species differ in the relative number of rods and cones that are present in their eyes. Which of the following statements would you expect to be true about these differences?
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15. The Special Senses
Inner Layer of the Eyeball
2:14 minutesProblem 8
Textbook Question
Which sequence best describes a normal route for the flow of tears from the eyes into the nasal cavity?
a. Lacrimal canaliculi, lacrimal sacs, nasolacrimal ducts
b. Lacrimal ducts, lacrimal canaliculi, nasolacrimal ducts
c. Nasolacrimal ducts, lacrimal canaliculi, lacrimal sacs
Verified step by step guidance1
Step 1: Understand the anatomy involved in tear drainage. Tears are produced by the lacrimal glands and then flow across the surface of the eye to keep it moist.
Step 2: Identify the structures that collect tears from the eye surface. Tears first enter small openings called lacrimal puncta, which lead into the lacrimal canaliculi.
Step 3: Recognize that the lacrimal canaliculi drain tears into the lacrimal sac, which acts as a reservoir for the tears before they continue their path.
Step 4: Know that from the lacrimal sac, tears flow down through the nasolacrimal duct, which empties into the nasal cavity.
Step 5: Based on this sequence, the correct order for tear flow is: lacrimal canaliculi → lacrimal sac → nasolacrimal duct.
Verified video answer for a similar problem:This video solution was recommended by our tutors as helpful for the problem above
Video duration:
2mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Anatomy of the Lacrimal Apparatus
The lacrimal apparatus includes structures responsible for tear production and drainage, such as the lacrimal glands, canaliculi, lacrimal sac, and nasolacrimal duct. Understanding these parts is essential to trace the tear flow from the eye to the nasal cavity.
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Golgi Apparatus
Pathway of Tear Drainage
Tears drain from the eye surface through the lacrimal puncta into the lacrimal canaliculi, then collect in the lacrimal sac, and finally flow down the nasolacrimal duct into the nasal cavity. This sequence ensures proper tear drainage and prevents eye dryness.
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Function of the Nasolacrimal Duct
The nasolacrimal duct is the final passageway that channels tears from the lacrimal sac into the nasal cavity. Its role explains why crying often leads to a runny nose, linking the eye's tear system to the respiratory tract.
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