Lab 8 (Senses) Study Notes

Identification of Muscles
- Superior Rectus: Located on the upper part of the eye.
- Lateral Rectus: Positioned on the side of the eye.
- Inferior Rectus: Visible along the bottom of the eye.
- Medial Rectus: Not visible from this view.
- Location: It is positioned medially and cannot be directly observed.
- Superior Oblique: Its tendon passes through a hook (called the trochlea) which changes its angle. Innervation: It is innervated by the trochlear cranial nerve.
- Inferior Oblique: Indicated by a green arrow; it wraps around the bottom of the eye.
Optic Nerve: Represented as a white structure situated among the extrinsic eye muscles.

Partially Removed Sclera: Displays the underlying choroid layer.
- Structures Identified: Sclera, Cornea, Iris, Pupil.

Key Components:
- Ciliary Body: Appears as a black “flower”.
- Suspensory Ligaments: Depicted as a white “flower”.
- Lens: The refractive part of the eye.
- Vitreous Humor: The gel-like substance filling the eye.
- Retina: The brown inner lining; critical for image formation.
- Pupil: Denotes the hole at the front; light enters here:
- Back Hole: Contains structures passing through; specifics not detailed in the notes.

Components Identified:
- Cornea, Sclera, Optic Nerve: Found in a coronally sectioned cow eye.
- Retina Detached from Choroid: Demonstrates anatomy and structures visually.

Lens: A small, orange ball that is clear in a living eye; preservative alters its color.
Vitreous Humor: Clear, gel-like substance supporting the eye's shape.
Suspensory Ligaments: Visible attaching the lens to the eye structure.
Choroid: Dark blue layer (tapetum lucidum), enhances low-light vision; absent in humans.
- Optic Disk: A tan region within the choroid indicating the start of the optic nerve.
Iris: The shiny black layer surrounding the pupil.
Ciliary Body: Rougher black area situated beyond the iris.
Aqueous Humor: Liquid in front of the lens; may spill during dissection, indicating drainage pathways.

Structures Identified: Ciliary Body, Iris, Pupil, Vitreous Humor, Lens, Cornea, Anterior Compartment, Choroid, Tapetum Lucidum, Retina, Sclera.

Purpose: Charts used to measure visual acuity.
- Procedure: Subject stands 6 meters (20 feet) away from the chart, with the smallest readable line denoting visual acuity.

Concept: The optic disk contains no photoreceptors (rods or cones), thus images here cannot be perceived.
- Typical Experience: Due to constant eye movement, the brain compensates for this absence.
- Demonstration Method: One eye is closed, fixate on a cross while moving an image closer until it disappears upon reaching the optic disk.

Definition of Astigmatism: An eye condition where the cornea is not perfectly spherical, leading to distorted vision.
- Testing Method: Lines on a chart appear uneven; darker lines indicate astigmatism. Uniformity in darkness suggests absence of the condition.

Structures: Auricle (or Pinna), External Acoustic Meatus, Tympanic Membrane, Auditory Ossicles (Malleus, Incus, Stapes), Pharyngotympanic Tube, Semicircular Canals.

Components:
- Malleus: Connects to the tympanic membrane.
- Incus: Functions as a bridge among ossicles.
- Stapes: Contacts the oval window.

Components Identified: Tympanic Membrane, Auditory Ossicles (Malleus, Incus, Stapes), Cochlea, Vestibule, Semicircular Canals, Vestibular Nerve, Cochlear Nerve.

Types of Deafness:
- Conductive Deafness: Involves obstruction within the external/middle ear affecting air sound conduction; bone conduction remains intact.
- Sensorineural Deafness: Related to defects in the cochlea or cochlear nerve affecting transmission of sound signals to the brain.
Tests Used: Weber and Rinne hearing tests help differentiate the types of hearing impairment.
- Resource: Instructions available in the lab manual and a video link provided for supplementary understanding.