SciOly Anatomy and Physiology: Sense Organs

What are the main sense organs in the human body?

The eye, ear, nose, and tongue.

What percentage of sensory receptors are located in the eyes?

70%.

What is the average diameter of an adult human eye?

About one inch.

What are the accessory structures of the eye?

Eyebrows, eyelids, conjunctiva, lacrimal apparatus, and extrinsic eye muscles.

What is the function of eyebrows?

They prevent perspiration from getting into the eyes and shade the eyes from sunlight.

What are eyelids also known as?

Palpebrae.

What is the role of the levator palpebrae superioris muscle?

It raises the superior eyelid to open the eye.

What is the function of the orbicularis oculi muscle?

It brings the eyelids together to shut the eye.

How often do we blink to prevent dehydration of the eye?

Every 3-7 seconds.

What are tarsal glands also known as?

Meibomian glands.

What do tarsal glands produce?

A lubricating oily secretion called meibum.

What is the conjunctiva?

A transparent mucous membrane that lines the anterior surface of the eye and the insides of the eyelid.

What is the function of the lacrimal apparatus?

It produces tears and drains excess lacrimal secretions into the nasal cavity.

What is the pathway of tears from the lacrimal gland to the nasal cavity?

Tears travel through excretory ducts to the surface of the eye, enter the lacrimal canaliculi via lacrimal puncta, then to the lacrimal sac, nasolacrimal duct, and finally into the nasal cavity.

What components are found in lacrimal fluid?

Mucus, antibodies, and lysozyme.

What is the primary function of tears?

To lubricate, moisten, and cleanse the surface of the eye.

What is the major function of the conjunctiva?

To produce a lubricating mucus that prevents the eyes from drying out.

What triggers blinking when something touches the eye?

The rich innervation of the eyelashes.

What is the lacrimal caruncle?

A fleshy elevation next to the medial canthus containing sebaceous and sweat glands.

What are the small holes called that allow tears to enter the lacrimal canaliculi?

Lacrimal puncta.

What is meibum?

A lubricating oily secretion produced by tarsal glands.

What is the significance of lysozyme in tears?

It is an enzyme that kills bacteria.

What is the role of the lacrimal gland?

To continually secrete a dilute saline solution known as lacrimal secretion or tears.

What are the primary functions of the extrinsic eye muscles?

They allow the eyes to follow moving objects, help maintain the shape of the eye, and hold it in the orbit.

How many rectus muscles are part of the extrinsic eye muscles, and what are their names?

There are four rectus muscles: superior, inferior, lateral, and medial.

What are the two oblique muscles of the extrinsic eye muscles?

The superior oblique and inferior oblique.

Describe the path of the superior oblique muscle.

It originates from the common tendinous ring, runs along the medial wall of the orbit, makes a right angle turn through a loop called the trochlea, and inserts on the superior aspect of the eyeball.

Where does the inferior oblique muscle originate and insert?

It originates from the medial orbit surface and runs laterally to insert on the inferior aspect of the eye.

Which cranial nerve controls the lateral rectus muscle?

Abducens (VI) controls the lateral rectus muscle.

What action does the medial rectus muscle perform and which nerve controls it?

It moves the eye medially and is controlled by the Oculomotor nerve (III).

What are the actions of the superior rectus muscle?

It rotates the eye medially and elevates the eye.

Which cranial nerve controls the inferior rectus muscle?

The Oculomotor nerve (III) controls the inferior rectus muscle.

What is the function of the inferior oblique muscle?

It rotates the eye laterally and elevates the eye.

Which cranial nerve is responsible for the superior oblique muscle?

Trochlear (IV) is responsible for the superior oblique muscle.

What are the three layers of the eyeball wall?

The three layers are the fibrous layer, vascular layer, and inner layer (retina).

What is the fibrous layer of the eyeball composed of?

It is composed of dense avascular connective tissue.

What is the vascular layer also known as?

The vascular layer is also called the uvea.

What are the two layers of the retina, and which one is involved in vision?

The two layers are the pigmented layer and the neural layer; only the neural layer plays a part in vision.

What types of photoreceptors are found in the retina?

There are rods and cones.

What is the function of cone cells in the retina?

Cone cells are sensitive to color and are located in the fovea.

What is the role of rod cells in vision?

Rod cells are not sensitive to color but have greater sensitivity to light, responsible for peripheral and night vision.

What is the 'blind spot' in the eye?

The optic nerve is called the 'blind spot' because it is insensitive to light.

How does the brain process visual input from the eyes?

The occipital lobe maps the visual input, combining input from both eyes into a three-dimensional image.

What happens to the image on the retina due to the lens, and how does the brain compensate?

The image on the retina is upside-down, but the brain compensates to provide the right-side-up perception.

What occurs in the eye in low light conditions?

A substance produced by rod cells increases sensitivity to detect very dim light.

How does the iris respond to strong light?

The iris contracts, reducing the size of the aperture that admits light into the eye.

What is the range of light sensitivity for the human eye?

The eye is sensitive to a spectrum of light that varies from red to violet.

What are the lower electromagnetic frequencies in the infrared sensed as?

Heat, but cannot be seen.

What sensations can higher frequencies in the ultraviolet cause?

Tingling of the skin or eyes, depending on the frequency.

Is the human eye sensitive to the polarization of light?

No, the human eye is not sensitive to the polarization of light.

What is the function of the outer ear?

To direct sounds toward the tympanic membrane.

What are the small bones in the middle ear called?

Malleus, incus, and stapes.

What is the cochlea?

A spiral-shaped chamber in the inner ear covered internally by nerve fibers that react to vibrations.

How does the brain determine the direction and distance of sounds?

By combining the input from both ears.

What is the vestibular system and what does it do?

Formed by three semicircular canals, it is responsible for the sense of balance and spatial orientation.

What are otoliths and their function in the inner ear?

Small particles containing calcium carbonate that help send signals to the brain about motion and acceleration.

What is the frequency range that the human ear can perceive?

From 16 cycles per second (very deep bass) to 28,000 cycles per second (very high pitch).

What is 'perfect pitch'?

The ability to map a tone precisely on the musical scale without reference to an external standard.

What is the primary function of the nose?

To serve as the organ of smell.

How do smell receptors in the nose transmit sensations to the brain?

By interacting with vapor molecules and connecting to the olfactory nerve.

What is the vomeronasal organ suspected to be sensitive to?

Pheromones that influence the reproductive cycle.

How many types of sensations can smell receptors detect?

Seven types: camphor, musk, flower, mint, ether, acrid, or putrid.

What can temporarily cause a loss of the sense of smell?

Having a cold.

What is the primary function of the tongue?

To serve as the organ of taste.

Where are taste buds primarily located?

In the tongue, roof of the mouth, and near the pharynx.

What are the four basic tastes that taste buds can detect?

Salty, sweet, bitter, and sour.

What additional taste sensation can the tongue detect?

Umami, from taste receptors sensitive to amino acids.

How does the sensitivity of taste buds vary among individuals?

The number of taste buds varies, and greater numbers increase sensitivity.

What gives the tongue its rough texture?

Papillae covering the surface of the tongue.