What structure is indicated by the arrow "3"?

Question

BlackTom AI · Accepted Answer

To interpret the labeled diagram, I’ll evaluate what each potential structure corresponds to in a chordate embryo.
Option: post-anal tail — This is the extended tail region beyond the anal opening. It is not a distinct internal rod and is usually a continuation of the body, not a compact midline structure marked by an arrow.
Option: intestine — The gut tube would be a hollow tube running along the ventral midline, connected to the stomach and intestines. The arrow in this position is not pointing at the gut tube; it points to a compact rod-like structure.
Option: nerve cord — The dorsal nerve cord lies just above the notochord in the embryo and is also a hollow tubular structure. If the arrow were at the dorsal nerve cord, we’d expect it to point at a tube-like structure near the dorsal midline. Here, the arrow labeled 3 designates a rod-like structure between the gut and the nerve cord, not the nerve cord itself.
Option: notochord — In chordate embryos, the notochord is a flexible, rod-shaped support that runs along the dorsal midline between the gut tube (ventral) and the nerve cord (dorsal). It provides axial support and is classically depicted as a distinct midline rod in diagrams of early development. The position and morphology match a central, rod-like structure labeled by arrow 3.
Option: myotome (muscle segment) — Myotomes are blocks of segmented muscle derived from somites, located lateral to the neural tube and not as a single midline rod. They are typically seen as paired blocks rather than a single central rod.
Option: pharyngeal arch — Pharyngeal arches appear in the head region as segmented external-gacial structures and arches, not as a midline rod along the trunk. They would be located more anteriorly and laterally, not along the midline where arrow 3 points.
Option: atriopore — The atriopore is an opening associated with early chordate circulatory or pharyngeal structures, not a central midline rod. It would not correspond to the labeled straight, elongated structure in the middle of the trunk.
Overall, the arrow 3 points to a central, rod-like structure along the dorsal midline consistent with the notochord, distinguishing it from the other options based on position, morphology, and developmental role.

W25 BIOL D006A 02Y Form/Funct In The Biolgcl Wrld Animal Review Test

What structure is indicated by the arrow "3"?

View Explanation

Log in for full answers

Similar Questions

Which of the following structures do all chordates share?

Which of the following structures do all chordates share?

Which of the following structures do all chordates share?

Which characteristic common to all Chordata?

In a consumer society, many adults channel creativity into buying things

Economic stress and unpredictable times have resulted in a booming industry for self-help products

People born without creativity never can develop it

A product has a selling price of $20, a contribution margin ratio of 40% and fixed cost of $120,000. To make a profit of $30,000. The number of units that must be sold is: Type the number without $ and a comma. Eg: 20000

More Practical Tools for Students Powered by AI Study Helper

Homework AI Solver

Stylized AI Paper Writer

Plagiarism Checker Assistant

Citation AI Academic Writing Tool

In-Class Translation Assistant

AI Note Generator

AI Quiz Answers

Past Exam Questions from University Test Bank

Smart Practice Assistant

Adaptive Practice

Making Your Study Simpler