ANATOMIA DOS OLHOS E DO OUVIDO INTERNO. VIDEO AULA. ENSINO SUPERIOR

Introduction to Sensory System: Anatomy of Eyes and Ears

Overview of the Lesson

• Laurão Soares introduces himself as a professor of human anatomy and physiology, outlining the focus on the sensory system, specifically the anatomy of eyes and ears.

Understanding Eye Functionality

• The eyes are described as structures that facilitate visual perception but do not interpret images; this function is performed by the brain.

• Light capture by the retina is essential for vision; without it, sight is impossible. The eyes act like cameras, transmitting information to be interpreted by the brain.

Brain's Role in Vision

• The brain corrects inverted images received from the eyes, allowing proper interpretation of visual stimuli.

• Eye movement is controlled by cranial nerves; misalignment can lead to conditions such as strabismus.

Detailed Anatomy of Eyes

• The lesson emphasizes that eyes transform light into nerve impulses which are processed in the occipital region of the brain.

• Human vision relies on daylight; our physiology is adapted for daytime activity rather than nocturnal vision.

Structural Components of Eyes

• A detailed anatomical description includes parts like the anterior chamber, ligaments, lens (crystal), cornea, iris, and pupil.

• The pupil adjusts size for distance viewing through dilation and contraction mechanisms.

Muscles and Vascularization

• Muscles around the eye ensure proper positioning within its bony cavity while blood vessels provide necessary nutrients and oxygen.

Layers of Eye Structure

• Three layers are identified: fibrous tunic (cornea & sclera), vascular tunic (choroid & iris), and internal tunic (retina).

Importance of Cornea

• The cornea plays a crucial role in focusing light but lacks blood vessels; it’s vital for refractive functions.

Brain's Filtering Mechanism

• Despite detecting surrounding elements like the nose during vision, the brain filters out irrelevant information to maintain focus on primary visual stimuli.

Understanding the Anatomy of the Eye

Structure and Function of the Cornea

• The cornea consists of multiple layers, including stratified epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium. Each layer plays a crucial role in maintaining corneal health and function.

• A clinical case highlights the difference between a normal eye and one with keratoconus (kerato), which causes distortion in vision due to protrusion of the cornea. This condition can arise from excessive eye rubbing.

• Rubbing the eyes can lead to keratoconus by causing structural changes over time; thus, avoiding this behavior is essential for eye health. Prolonged friction increases risk factors for developing this condition.

The Sclera: Protective Layer of the Eye

• The sclera is described as a white, hollow layer that encases the posterior structures of the eyeball and consists of three layers: episclera, scleral stroma, and lamina fusca. Its primary function is to protect internal ocular structures.

• It also serves as an attachment point for extraocular muscles that facilitate eye movement through innervation by cranial nerve III (oculomotor nerve). This connection is vital for coordinated ocular motion.

Exploring the Choroid

• The choroid is a highly vascularized structure divided into three layers: vascular layer (rich in blood vessels), capillary layer (not related to hair), and membrane layer. It provides essential blood supply to retinal tissues while preventing light reflection within the eye.

• Innervated by short and long ciliary nerves originating from cranial nerve V (trigeminal nerve), it plays a significant role in sensory functions related to ocular health. Additionally, it absorbs excess light entering the eye to enhance visual clarity.

Components of Ciliary Body and Iris

• The ciliary body produces aqueous humor in the posterior chamber and contains ciliary muscle responsible for adjusting lens shape for better focus (accommodation). This process is critical for clear vision at varying distances.

• The iris features pigmentation influenced by genetic factors; variations include brown shades or blue hues among individuals. It regulates pupil size through sphincter action affecting light entry into the eye—essential for optimal vision under different lighting conditions.

Additional Observations on Eyelids

• Eyelids consist of upper and lower parts along with eyelashes; they serve protective roles against environmental elements impacting ocular health.

• Vibrating eyelids may indicate stress or elevated cortisol levels; understanding these physiological responses can provide insights into overall well-being related to visual strain or anxiety levels experienced by individuals during stressful situations.

Understanding Stress and Its Effects on the Body

The Connection Between Stress and Physical Symptoms

• Stress can lead to physical symptoms such as eyelid twitching, indicating that the body is signaling a need to relax.

• Elevated stress levels can cause significant physiological changes, including pupil dilation (mydriasis), which may be observed in clinical cases.

• Mydriasis can occur due to drug use or medications that induce this response, highlighting the body's reaction to external substances.

Anatomy of the Eye: Key Structures

Retina and Its Functions

• The retina plays a crucial role in processing light; it converts light into nerve impulses sent to the brain via the optic nerve.

• The retina consists of two main parts: the neurosensory retina and the retinal pigment epithelium, each serving distinct functions in vision.

Histological Aspects of the Retina

• Microscopic examination reveals various cell types within the neurosensory retina, including densely packed nuclei indicative of cellular activity.

• The internal nuclear layer contains numerous cell nuclei, while ganglion cells are more sparsely distributed in other layers.

Neural Pathways and Visual Processing

Transmission of Visual Information

• The neurosensory retina is responsible for receiving light information and transmitting sensory data to the brain for interpretation.

• Neurons within the retina play a vital role in propagating visual information towards the occipital lobe of the brain, where visual processing occurs.

Specialized Structures Within the Eye

Macula and Lens Functionality

• The macula is central to vision; it contains photoreceptors that convert light stimuli into electrical signals essential for sight.

• The lens focuses light onto the retina; its structure includes a capsule, epithelial layer, and crystalline fibers crucial for refractive function.

Vitreous Body's Role

• The vitreous body is a gelatinous substance contributing to light refraction within the eye. It connects with adjacent structures for optimal functionality.

Summary of Eye Anatomy

Overview of Key Components

• A comprehensive understanding of eye anatomy includes structures like cornea, pupil, iris, ciliary body, and vitreous body—all integral for vision.

Understanding the Aqueous Humor and Eye Anatomy

The Role of Aqueous Humor

• Aqueous humor is a nutrient-rich fluid filling the anterior and posterior chambers of the eye, produced by ciliary processes.

• Its primary function is to nourish critical structures like the lens and cornea, which require special care.

Components of Vision

• Key components involved in vision include:

• Pupil: An orifice that adjusts size based on light conditions.

• Cornea: The outer layer that helps focus light.

• Iris: The colored part behind the cornea.

• Retina: Contains neuro-sensory cells crucial for image processing.

Common Visual Impairments

• Conditions such as myopia (nearsightedness), hyperopia (farsightedness), and astigmatism significantly affect visual fields.

• Patients often rely on glasses for correction, though surgical options and contact lenses are also available.

Anatomy of the Ear

Overview of Ear Functionality

• The ear is a sensory structure responsible for sound perception and maintaining balance through its internal anatomy.

Structure of the Ear

• The ear consists of three parts:

• Outer Ear

• Middle Ear

• Inner Ear

Sound Processing Mechanism

• Sound waves are converted into nerve impulses that travel to specific brain areas, primarily interpreted in the temporal lobe.

Detailed Examination of Outer Ear Anatomy

Components of Outer Ear

• The outer ear includes small bony structures like the malleus (hammer) and incus (anvil), essential for sound transmission.

Importance of External Structures

• The external ear extends from the auricle to the tympanic membrane, approximately 2 to 3 cm long.

• Caution is advised when cleaning ears with cotton swabs as they can damage sensitive structures like the tympanic membrane.

Protective Functions of Cerumen

• Glands within the outer ear produce cerumen (earwax), which protects against pathogens while accumulating debris.

Tympanic Membrane Functionality

• The tympanic membrane vibrates upon receiving sound waves, transmitting these vibrations to middle ear structures for further processing.

This structured approach provides a comprehensive overview while allowing easy navigation through key concepts discussed in this segment.

Anatomy of the Ear

Overview of Ear Structure

• The tympanic membrane is observed in the figure, along with the cartilage tissue of the external ear. The middle ear is described as an air-filled cavity located within the petrous part of the temporal bone.

• The middle ear contains an auditory tube that connects it to the nasopharynx and includes structures like the antromastoid, mastoid cells, and three ossicles: malleus, incus, and stapes.

• These ossicles are interconnected rather than isolated, playing a crucial role in sound wave reception within the ear.

Inner Ear Functionality

• The inner ear functions as a vestibulocochlear organ responsible for both hearing and balance. It consists of bony labyrinth structures forming cavities within the temporal bone and membranous labyrinth systems containing ducts and sacs.

• Key components of the inner ear include:

• Cochlea

• Semicircular canals

• Vestibular nerve

• Cochlear nerve

• Auditory tube

External Ear Anatomy

• The external ear comprises visible parts such as:

• Concha (the outer shell)

• Auricular lobe (earlobe)

• This section has fewer blood vessels; notably, it's where earrings are typically placed.

Sensory Nerve Connections

• The sensory innervation from the inner ear to the brain is facilitated by various nerves including vestibular nerves. This concludes today's lesson on eye and ear anatomy, aiming for clarity and objectivity in understanding these structures.