Human Anatomy: Eye and Ear Functions

Motivational Quote

• Do something today that your future self will thank you for.

Special Senses and the Lymphatic System

Case Study

• Leslie woke up with irritated and swollen eyes.
• The white portion of her eyes became reddish and itchy.

Special Senses

• Sight
• Taste
• Touch
• Smell
• Hearing and Equilibrium

Sight

• The eye is the organ of sight.
• Eyes take in light from the outside world and send visual information to the brain.
• Approximately 70% of all body receptors are in the eyes.
• The eye is a sphere about 1 inch in diameter.

Parts of the Eye

• Sclera
• Cornea
• Retina
• Iris
• Pupil
• Lens
• Macula
• Vitreous Humour

Sclera

• The white outer layer, supporting wall of the eyeball.
• Helps maintain the eye's shape and protects it from injury.

Cornea

• The eye's outermost lens.
• Functions like a window, controlling and focusing light entry.
• Contributes 65-75% of the eye's focusing power.

Retina

• A thin layer of tissue covering most of the back of the eye, near the optic nerve.
• Receives light from the lens, converts it to neural signals, and transmits them to the brain for visual recognition.

Iris

• The colored part of the eye.
• Regulates the amount of light entering the eye.
• Contracts (closes) in bright light, and expands (opens) in dim light to adjust for the amount of light.

Pupil

• The opening in the center of the iris.
• Its function is to control the amount of light entering the eye based on light levels.

Lens

• Located in the eyeball.
• Changes its shape to change the focal distance of the eye.
• Focuses light rays to create clear images of objects at various distances.

Macula

• Located near the center of the retina.
• Processes sharp, clear, straight-ahead vision.

Vitreous Humour

• A transparent, colorless, gelatinous mass filling the space between the lens and retina.
• Helps maintain the eye's rounded shape and with vision clarity.
• Accounts for approximately 80% of the eye's volume.

Aqueous Humour

• A transparent, colorless, gelatinous mass.
• Flows in and out of the front of the eye.
• Maintains proper ocular pressure (eye pressure) in the eye.

External and Accessory Parts

• Eyelids
• Eyelashes
• Conjunctiva
• Lacrimal Gland

Eyelids

• Thin tissue structures covering and protecting the eye's front.
• Spread tears over the eye surface to keep it moist and protect it from drying out.

Eyelashes

• Short hairs along the edge of the eyelids.
• First line of defense against airborne particles like dirt, dust, lint etc.

Conjunctiva

• Transparent mucous membrane covering the inside surface of the eyelids and the anterior eye surface (excluding the cornea)
• Protects and lubricates the eye.
• Prevents bacteria from entering the eye.

Lacrimal Gland

• Situated laterally at the end of each eye.
• Produces lacrimal fluid (tears).

Tears

• Clear liquid secreted by the lacrimal glands
• Contains dilute salt solution, mucus, antibodies, and lysozyme
• Functions to clean, protect, moisten, and lubricate the eye.

Hearing and Balance

• The ears are the organs.
• They're paired, located on each side of the head.
• The ear comprises 3 sections:
• External ear
• Middle ear
• Internal ear

Anatomy of the Ear

• External Ear, Middle Ear, Inner Ear

External Ear

• Auricle
• External acoustic meatus
• Tympanic membrane

Middle Ear Cavity

• Air-filled, mucosa-lined cavity.
• Hearing only.
• Located between tympanic membrane and oval/round windows.
• Made of auditory ossicles.

Auditory Ossicles

• Malleus (hammer), Incus (anvil), Stapes (stirrup).
• Transmit vibrations from the eardrum to the fluids of the inner ear.

Malleus

• Largest, most lateral of the bony chain of ossicles.
• Club-shaped structure.
• Functions with other bones to transmit vibrations.

Incus

• Middle of the 3 small bones in the middle ear.
• Transmits vibrations from the malleus to the stapes.

Stapes

• Smallest bone in the human body.
• Innermost (most medial).
• Transmits vibrations to the cochlea.

Inner Ear

• Cochlea
• Vestibule
• Semicircular canals

Cochlea

• Hollow, spiral-shaped bone in the inner ear.
• Key to hearing.
• Transduces sound waves into electrical impulses.
• Interprets sound frequencies.

Vestibule

• Area in the inner ear between the tympanic cavity and the cochlea.
• Controls equilibrium and balance.

Semicircular Canals

• Tiny, fluid-filled tubes in the inner ear.
• Help maintain balance.
• Liquid movement within the canals triggers the tiny hairs for balance detection.

Equilibrium

• State of balance.
• Inner ear receptors respond to head movements.
• Vestibular apparatus with two parts - static and dynamic equilibrium.

Smell and Taste

• Involves 2 organs:
• Tongue.
• Nose

Olfactory Receptor

• Faculty to perceive odors/scents.
• Receptors in the nose detect odors.

Taste

• Sensation of flavor.
• Tongue the organ of taste.
• Taste receptors (taste buds) on the tongue surface detect flavors (salty, sweet, sour, bitter, and umami).

Taste Buds

• Sensory organs on the tongue.
• Detect sweet, salty, sour, bitter, and umami tastes.

Lymphatic System

• Tissues and organs carrying white blood cells for fighting infections.
• Drainage system returning excess fluids from cells to blood vessels.

Main Functions

• Collecting excess fluid from tissues back to the bloodstream.
• Helping the body absorb fats.
• Protecting the body against invaders.

Lymphatic Vessels

• Thin tubes carrying lymph (lymphatic fluid) and white blood cells.

Lymph

• Fluid flowing through the lymphatic system.
• Similar to blood plasma, but richer in lymphocytes when exiting lymph nodes.

Lymph Nodes

• Small glands filtering lymph through lymph vessels
• Become swollen in response to infection or tumors
• Kidney-shaped, less than 1 inch, encapsulated, in connective tissues

Lymphoid Organs

• Spleen
• Thymus
• Tonsils
• Peyer’s Patches

Spleen

• Soft organ on the left side of the abdomen.
• Filters and cleanses blood.
• Destroys worn-out red blood cells (RBCs).
• Returns breakdown products to the liver.

Thymus

• Lymphoid mass in the anterior mediastinum, above the heart.
• Produces and matures lymphocytes (T cells).
• Important for immune responses.

Tonsils

• Lymphoid tissue masses in the throat.
• Trap and remove bacteria.

Peyer’s Patches

• Lymphoid tissue in the intestinal wall.
• Capture and destroy bacteria.

Test your knowledge on the functions of the eye and ear in this quiz! Explore topics such as the vitreous humor, external ear structure, and the roles of tears and the cochlea. Perfect for students studying human anatomy or anyone interested in how our sensory systems work.