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A&P > Special senses (Ch 15) > Flashcards

Special senses (Ch 15) Flashcards

1
Q

THE EYE AND VISION

A
  • 70% of body’s sensory receptors are in eye
  • Half of cerebral cortex is involved in visual processing
  • The Eye is a small sphere; only one-sixth of surface visible
  • Most of eye enclosed and protected by fat cushion and bony orbit
  • Consists of accessory structures and the eyeball
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2
Q

the structure of the eye?

A
  • Eyebrows
  • Eyelids
  • Conjunctiva
  • Lacrimal apparatus
  • Extrinsic eye muscles
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3
Q

Eyelids

A
  • Function: Protect the eye anteriorly.
  • Structure: Thin skin-covered folds separated at the palpebral fissure, meeting at medial and lateral commissures.
  • Lacrimal Caruncle: Located at the medial commissure, contains oil and sweat glands.
  • Tarsal Plates: Supporting connective tissue for folds, anchoring orbicularis oculi and levator palpebrae superioris muscles.
  • Innervation: Levator palpebrae superioris by oculomotor nerve (CN III), orbicularis oculi by facial nerve (CN VII).
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4
Q

what are some lubricating glands found within the eyelids

A
  • Tarsal glands: Modified sebaceous glands produce oily secretion that lubricates lid and eye
  • Ciliary glands between hair follicles are
    Modified sweat glands.
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5
Q

what muscle helps pull the eye upwards:

A

Levator palpebrae innervated by the branches of the oculomotor nerve (CN III)

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6
Q

Conjunctiva?

A
  • Description: Transparent mucous membrane producing lubricating mucous secretion.
  • Palpebral Conjunctiva: Membrane lining the inside of eyelids.
  • Bulbar Conjunctiva: Membrane covering the sclera (whites of eyes) excluding the cornea.
  • Conjunctival Sac: Space between palpebral and bulbar conjunctiva.
  • Conditions: Conjunctivitis (Pinkeye) - Inflammation, often due to infections (bacterial or viral), highly contagious.
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7
Q

Lacrimal apparatus

A

Components:
- Lacrimal Gland: Located in the orbit above the lateral end of the eye, secretes tears (lacrima).
- Lacrimal Ducts: Drains tears into the nasal cavity.
- Tear Composition: Dilute saline solution with mucus, antibodies, and antibacterial lysozyme.
- Blinking Mechanism: Tears spread toward the medial commissure during blinking.
- Lacrimal canaliculi and puncta: Channels and holes through which tears enter.
Drainage Pathway:
- Tears drain into the lacrimal sac and then the nasolacrimal duct.
- Nasolacrimal duct empties into the nasal cavity.

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8
Q

Significance of Strabismus?

A

Strabismus (“cross-eye”): congenital weakness of external eye muscles
- Eye Patch: Temporarily cover the stronger eye to strengthen the weaker one (amblyopia)

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9
Q

What are 3 layer of eye layer?

A
  1. Fibrous Layer: Outermost layer. made up of the sclera and cornea.
  2. Vascular Layer: Middle layer. made up of the uvea
  3. Inner Layer: Innermost layer.
    - Internal Cavity: Filled with fluids known as humors.
    - Lens: Separates internal cavity into anterior and posterior segments.
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10
Q

Cornea

A

Forms clear window that lets light enter and bends light as it enters eye
- protects from abrasions

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11
Q

Vascular Layer (Tunic)?

A
  • Middle pigmented layer of eye, also called uvea
  • Three regions: choroid, ciliary body, and iris-
    1) Choroid region (pink layer): Posterior portion, and Supplies blood to all layers; absorbs light to prevent scattering.
    2) Ciliary body (connects lens to rest of vascular layer): Anterior extension of the choroid, Controls lens shape via the ciliary zonule.
    3)iris: Colored part of eye that lies between cornea and lens, connected by the ciliary body.
    – ciliary zonule (suspensory ligament) extends from ciliary processes to lens. (Holds lens in position)
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12
Q

Iris and pupil

A
  • Iris: Colored part of the eye situated between the cornea and lens, connected by the ciliary body.
  • Pupil: Central opening regulating the amount of light entering the eye.
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13
Q

Sympathetic and parasympathetic?

A
  • Sympathetic: dilator pupillae, muscle contracts pupil dilates
  • Parasympathetic: pupil constricts. (size decreases).
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14
Q

Inner layer (tunic)?

A
  • Retina originates as an outpocketing of brain.
  • Contains:
    Millions of photoreceptor cells that transduce light energy
    Neurons
    Glial cells
  • Delicate two-layered membrane
    Outer pigmented layer (picks out color).
    Inner neural layer
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15
Q

layer of retina?

A

Pigmented Layer: Single-cell-thick lining next to the choroid.
Functions:
- Absorbs light and prevents its scattering.
- Phagocytizes photoreceptor cell fragments.
- Stores vitamin A.
Neural Layer: Three main types of neurons - Photoreceptors, bipolar cells, ganglion cells.
- Signals spread from photoreceptors to bipolar cells to ganglion cells.
- Exit the eye as the optic nerve.

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16
Q

Optic Disc (Blind Spot):

A

Optic Disc (Blind Spot): Site where the optic nerve leaves the eye.
Characteristics:
Lacks photoreceptors, hence referred to as the blind spot.
- Rods (for dim blurry vision)
Dim light, peripheral vision receptors
More numerous and more sensitive to light than cones
No color vision or sharp images

17
Q

cones - colour vision

A
  • cones: Vision receptors for bright light.
    High-resolution color vision.
  • Macula Lutea: Area at the posterior pole lateral to the blind spot. (Contains mostly cones.)
  • Fovea Centralis: Tiny pit in the center of the macula lutea, contains ALL cones. Allows fovea to pick up fovea to pick up details when seeing.
18
Q

Eye Chambers and Fluids?

A

Posterior Segment:
- Contains vitreous humor.
- Functions: Transmits light, supports the lens, holds retina layers together.
- Forms in embryo, lasts a lifetime.
Anterior Segment:
- Contains aqueous humor. (Aqua: water, watery)
- Formation: Continuously formed by ciliary processes.
- Drainage: Via scleral venous sinus.
- Functions: Supplies nutrients and oxygen to lens and cornea, drains waste.

19
Q

lens and its 2 regions

A
  • Changes shape to precisely focus light on retina.
    Lens Epithelium: Anterior region, composed of cuboidal cells.
  • Lens Fibers: Bulk of the lens, filled with transparent protein crystallin.
    –> Function: Work together for light refraction and focusing on the retina.
20
Q

explain briefly the Refraction and lenses

A

Convex lenses bend light passing through it, so that rays converge at focal point

21
Q

some significances of the eye

A
  • Retinal Detachment: Separation of the light-sensitive retina from the underlying tissue.
    Causes: Trauma, age-related changes, inflammatory disorders.
  • Glaucoma in which drainage of aqueous humor is blocked, causing fluid to back up and increase pressure within eye
  • Cataract: is a cloudy area in the lens of your eye.
  • Myopia (nearsightedness): near objects appear clear, but objects farther away look blurry.
  • Hyperopia (farsightedness): opposite of myopia.
  • Astigmatism: Unequal curvatures in different parts of cornea or lens

A&P (9 decks)

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