Question

Ciliary muscles are found in (a) Diaphragm of a mammal (b) Eyes of vertebrates (c) Heart of vertebrates (d) Stomach of frog

Short answer

The ciliary muscles are found in the (b) Eyes of vertebrates.

Step-by-step solution

- Understand What Ciliary Muscles Are

Ciliary muscles are tiny muscles in the eye, particularly the ciliary body. They help control the shape of the lens and thus help the eye focus on objects at varying distances.

- Analyze Each Choice in Light of Definition

Now considering each option: \n(a) Diaphragm of a mammal: The diaphragm is a muscular structure for breathing, and does not contain ciliary muscles.\n(b) Eyes of vertebrates: Ciliary muscles are indeed found here based on the definition.\n(c) Heart of vertebrate: The heart is made of cardiac muscle cells, not ciliary muscles.\n(d) Stomach of frog: The muscles in the frog's stomach are smooth muscles, not ciliary muscles.

- Conclude Which Option Is Correct

Having gone through all the options, only one matches the description and location of ciliary muscles - (b) Eyes of vertebrates

Key concepts

Vertebrate Eye Anatomy

Understanding the vertebrate eye anatomy is essential to grasp the role and function of ciliary muscles. Vertebrates, such as mammals, birds, and reptiles, have a complex eye structure tailored to their environment. At a basic level, the eye is composed of several key components:

• Cornea: The clear front surface of the eye that helps focus incoming light.
• Pupil: The opening in the iris through which light enters the eye.
• Lens: Adjusts its shape for focusing light onto the retina.
• Retina: Contains photoreceptor cells that convert light into electrical signals.
• Optic Nerve: Transmits these signals to the brain for processing.

The ciliary muscles, situated within the ciliary body, connect to the lens via zonules (also called suspensory ligaments). These muscles play a pivotal role in adjusting the lens shape, thereby aiding in precise focusing of objects at different distances.

Lens Focusing Mechanism

The lens focusing mechanism in the eye is a fascinating interplay of biological structures. At its core, it's about how the eye adjusts to bring objects into sharp focus. This adjustment is greatly aided by the ciliary muscles and the lens.
Here's how the focusing works:

• Lens Shape Change: The lens is flexible and can change its shape to focus light accurately on the retina.
• Ciliary Muscle Contraction: When these muscles contract, the lens becomes more rounded, allowing it to focus on closer objects.
• Ciliary Muscle Relaxation: When the ciliary muscles relax, the lens flattens, making it possible to focus on distant objects.

This dynamic changing shape of the lens—controlled by the ciliary muscles—is what allows for clear vision across varying distances. This focusing mechanism ensures that regardless of whether an object is nearby or far away, the eye can quickly adjust to bring the image into focus on the retina.

Eye Accommodation Process

Eye accommodation refers to the process by which the eye changes optical power to maintain a clear image or focus on an object as its distance varies. This process involves the ciliary muscles and the elasticity of the lens.
Accommodation lets us have sharp vision across different distances. The steps involved in this process are:

• Close Object Focus: When focusing on something nearby, the ciliary muscles contract, reducing the tension on the zonules. This allows the lens to thicken and become more convex, increasing its focusing power.
• Distant Object Focus: To focus on distant objects, the ciliary muscles relax, increasing tension on the zonules, which flattens the lens, reducing its focusing power.

In young individuals, the lens is very elastic, enabling easy accommodation for near objects. However, with age, the lens can become less flexible—a condition known as presbyopia—leading to difficulties in focusing on close objects. Understanding this accommodation process helps to appreciate how our vision adapts seamlessly to different visual demands.