NURS 3120 Lecture Notes - Lecture 4: Palpebral Fissure, Meibomian Gland, Optic Disc

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HEENT Physiology and Anatomy
Head
Head and neck contain multiple structures:
o Skull encloses brain
o Facial structures include eyes, ears, nose, and mouth
o Neck structures include:
Upper portion of spine
Esophagus
Trachea
Thyroid gland
Arteries
Veins
Lymph nodes
Anatomy and Physiology: Head
Skull is a bony structure that protects brain and upper spinal cord:
o Contains special senses of vision, hearing, smell, taste
o Comprises six bones fused at sutures
o Covered by scalp tissue typically covered with hair
Face comprises 14 bones:
o Mandible articulates with temporal bone to form temporomandibular joint
o Facial muscles innervated by cranial nerves V (trigeminal) and VII (facial)
Anatomy and Physiology: Eyes External Ocular Structures
External Ocular structures:
o External eye is composed of eyebrows, upper and lower eyelids, eyelashes,
conjunctivae, and lacrimal glands
o Palpebral fissure is opening between eyelids
o Conjunctivae are two thin, transparent mucous membranes, between eyelids
and eyeball
Bulbar conjunctiva covers scleral surface of eyeball
Palpebral conjunctiva lines eyelids and contains blood vessels, nerves,
hair follicles, and sebaceous glands
o Meibomian gland secretes substance to lubricate lids, slows evaporation of
tears, provides airtight seal when lids closed
o Lacrimal glands form tears that combine with sebaceous secretions to maintain
constant film over cornea
Anatomy and Physiology: Eyes: Ocular Structures
Ocular structures:
o Globe of the eye, the eyeball, is surrounded by three separate layers:
Sclera, outer layer
Uvea, middle layer
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Retina, inner layer
Anatomy and Physiology: Eye: Sclera
Ocular structures: Sclera
o “lera is tough, firous outer layer, hite of eye
o Limbus is junction where sclera merges with cornea
o Cornea covers iris and pupil, is transparent, avascular, and richly innervated with
sensory nerves
Cornea allows light transmission through lens to retina
Tears provide cornea with oxygen and protect surface from drying
Anatomy and Physiology: Eyes: Uvea
Ocular structures: Uvea
o Uvea, middle layer, consists of:
Choroid layer, posteriorly, which supplies blood to retina
Iris, anteriorly, is circular, muscular membrane that regulates pupil
dilation and constriction via the oculomotor nerve, cranial nerve III
Pupil, central opening of iris, allows light transmission to retina
Ciliary body, anteriorly, adjusts lens to accommodate vision at varying
distances
Also produces transparent aqueous humor that flows between
lens and iris
Anatomy and Physiology: Eye: Retina
Ocular structures: Retina
o Retina, inner layer, extension of central nervous system (CNS)
Transparent layer with photoreceptor cells, rods and cones, unevenly
distributed over its surface
Rods and cones perceive images and colors in response to varying light
stimuli
Rods respond to low levels of light
Cones respond to higher levels of light
Anatomy and Physiology: Eye: Optic Disc
Ocular structures: Optic Disc
o Optic disc, perforates retina, head of optic nerve, CN II, which contains no rods
or cones and causes small blind spot at center of vision
Central retinal artery and central vein bifurcate, emerge, and feed into
smaller branches throughout retinal surface
Anatomy and Physiology: Eye: Ocular Function
Vision occurs when:
o Rods and cones respond to varying light stimuli
o Lenses constantly adjust to stimuli at different distances by accommodation
When lens focus nerve impulses transmit information to visual cortex
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Document Summary

Head: head and neck contain multiple structures, skull encloses brain, facial structures include eyes, ears, nose, and mouth, neck structures include: Bulbar conjunctiva covers scleral surface of eyeball. Anatomy and physiology: eyes: ocular structures: ocular structures, globe of the eye, the eyeball, is surrounded by three separate layers: Cornea allows light transmission through lens to retina. Tears provide cornea with oxygen and protect surface from drying. Anatomy and physiology: eyes: uvea: ocular structures: uvea, uvea, middle layer, consists of: Choroid layer, posteriorly, which supplies blood to retina. Iris, anteriorly, is circular, muscular membrane that regulates pupil dilation and constriction via the oculomotor nerve, cranial nerve iii. Pupil, central opening of iris, allows light transmission to retina. Ciliary body, anteriorly, adjusts lens to accommodate vision at varying distances. Also produces transparent aqueous humor that flows between lens and iris. Anatomy and physiology: eye: retina: ocular structures: retina, retina, inner layer, extension of central nervous system (cns)

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