D19 - The eyeball: tunics Flashcards Preview

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Flashcards in D19 - The eyeball: tunics Deck (10)
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1
Q

What does the visual organ consists of?

A
  • Eyeball
  • N. opticus
  • Accessory organs
    • Corpus adiposum orbitae
    • Fascia bulbi
      • Preorbita
      • Fascia muscularis superficialis
      • Fascia muscularis profunda
    • Muscles of the eyeball
    • Eyelids (palpebrae)
      • Superior
      • Inferior
    • Gl. lacrimalis
2
Q

Define orbit

General knowledge

A
  • The orbit is a cavity on the lateral surface of the skull
  • Contains the eyeball
  • Continous with fossa temporalis and fossa peterygopalatina
3
Q

Give the division of the interior of the eyeball

General knowledge, not directly linked to the topic

A
  • The interior of the eyeball is divided into 3 chambers (camera bulbi):
    • Camera anteror (anterior chamber)
      • Between cornea and iris
      • Filled with aqueous humor
    • Camera posterior (posterior chamber)
      • Between iris, ciliary body and lens
      • Filled with aqueous humo
    • Camera viteria (viterous body)
      • Largest of the 3 chambers
      • Behind the lens
      • Surrounded by retina
4
Q

The eyeball

Give the tunics of the eyeball

A
  • The wall of the eyeball is formed by 3 layers (tunicae), which enclose the interior of the eyeball
  1. Tunica externa/fibrosa
    • Role: gives form and protects the eyeball
    • The only complete tunic
    • Consists of:
      • Sclera
      • Cornea
  2. Tunica media/vasculosa
    • Consists of blood vessels and smooth muscles
    • Role:
      • Nutrition of the eyeball
      • Regulation of the shape of the lens and size of the pupil
    • Consists of:
      • Choroidea
      • Ciliary body
      • Iris
  3. Tunica interna/nervosa
    • Consists of nervous tissue
    • Role: the layer most directly concerned with vision
      • Translation of visual stimuli into nerve impulses form interpretation by the brain
    • Consists of:
      • Nonvisual retina (pars caeca retina)
      • Optic part of retina (pars optica retinae)
5
Q

Tunics

Tunica externa/fibrosa

A
  • Made up of very dense collagenous tissue
    • Resisting the internal pressure and gives the eye shape and stifness
  • Consists of sclera and cornea which meet at the limbus
  • Sclera:
    • Outer layer (together with cornea)
    • “white of the eye”
    • Pars perforata: ventral to the posterior pole, passes the fibers of n. opticus
    • It gives attachment to the tendons of the ocular muscles anterior to the equator
    • Vagina bulbi: posteriorly, except for the area taken up by the m. retractor bulbi, it is covered by a thin membrane that separates the corpus adiposum orbitae
    • Near the limbus the sclera is covered by conjuctiva, which furnishes connection to the inside of the lids
  • Limbus cornea: the edge of the cornea where it is continous witht the sclera
  • Cornea: ​​
    • Outer layer (together with sclera)
    • Avascular
    • Layers:
      • Epithelium
      • Lamina limitans anterior (acellular)
      • Substantia propria
      • Lamina limitans posterior (acellular)
      • Endothelium camerae anterioris
    • Cornea lack blood vessels
      • Nourished by diffusion from the interior of the eye
      • Nutrition: vessels of limbus → lacrimal fluid
    • Corneal reflex: free nerve endings from the n. ciliaris longus (of n. opthalmici); eye lids close when touching the cornea
6
Q

Tunics

Tunica media/vascularis

A
  • Tunica vasculosa = uvea
  • Interposed between sclera and retina
  • Functions:
    • Blood supply
    • Suspension and regulation of shape of the lens
    • Regulation of the size of the pupil
    • Production of aqueous humor
  • 3 zones in posterioanteroior sequence
    1. Choroidea
    2. Corpus cileare
    3. Iris
7
Q

Tunics

Tunica media/vascularis: choroidea

A
  • ​​Vascular layer
  • Envelopes the posterior part of the eyeball
  • Tapedium lucidum:
    • Dorsal to optic papilla, in a half-moon shaped area
    • Has an additional reflective layer between the vascular and choroideocapillary layer
    • Avascular layer (ø sus)
    • Cellular (ca)
    • Fibrous (ru, eq)
8
Q

Tunics

Tunica media/vascularis: corpus ciliaris

A
  • Thickened middle segment of tunica vascularis
  • Between choridea and iris
  • forms lateral borders of the posterior chamber
  • Outer surface is covered by sclera
  • Inner surface is covered by nonvisual part of retina
  • Corpus ciliaris can be subdivided into:
    • Ciliary ring
    • Crown of ciliary body
      • Most prominant anterior portion
      • Contains processus ciliaris
  • Lens is fixed in position by ciliary zonule
  • M. ciliaris:
    • Smooth muscle
    • Action: accommodation
      • Enables the lens to change its shape to focus on near or distant objects
    • Innervation:
      • Parasympathetic from ggl. ciliaris (muscle contract)
      • Sympathetic innervation from plexus caroticus interna (muscle relaxes)
      • Sensory: V1 → n. nasociliares → n. ciliare
  • Oculomotorius ??
  • 1 motor nuclei ??
  • Parasympathetic nuclei ??
9
Q

Tunics

Tunica media/vascularis: iris

A
  • Thin ring of vascular tissue
  • Suspended between the cornea and lens
  • Attached at the periphery of the sclera (by ligg. pectinati) and corpus ciliaris
  • Color of the iris determines the color of the eyes, depending on the number of pigmented cells present in the stroma
  • Size of pupil: amount of light reaching the retina are regulated by the smooth muscles
    • M. sphincter pupillae
      • Close to pupillary margin
      • Parasympathetic fibers
    • M. dilator pupillae
      • Contraction → enlarges pupil
      • Sympathetic fibers
  • Divides the space between the lens and cornea into:
    • Anterior chamber
    • Posterior chamber
  • Both chambers are filed with aqueous humor
    • Circulation:
      1. Pupil
      2. Angulus iridocornealis
      3. Space of fontana
      4. Channels of schlemm
      5. Episcleral veins
  • Consists of 3 layers:
    • Anterior epithelial layer
    • Middle layer
    • Posterior epithelial layer
10
Q

Tunics

Tunica interna/nervosa

A

Retina:

  • Contains light-sensitive receptor cells
  • No blood vessels
  • Connected by n. opticus
  • Outgrowth of diencephalon
  • The retina can be divided into:
    • Non-visual retina (pars caeca retinae)
      • ​Ciliary part of retina (pars ciliaris retinae)
      • Iridial part of retina (pars iridica retinae)
    • Optic part of retina (pars optica retinae)
  • Ora serrata: marks the border between non-visual retina and optic part of retina
  • Discus n. optici: Blind spot where n. opticus enters
  • Macula: Area of maximum optical resolution
  • Non- visual retina: (optic part)
    • Pars ciliaris
    • Pars iridialis

Pars ceca retinae:

  • Anterior part of eye

Pars optica retinae:

  • Posterior to ora serrata
  • Divided into:
    • Outer pigmented layer
    • Inner neural layer
  • Layers:
    • Pigmented cells
    • Receptor cells:
      • ​Rods (black/white vision, night)
      • Cones (color vision, day)
    • Bipolar ganglion cells
    • Multipolar ganglion calles
  • Transduction of stimulus: (tertiary receptor type)
    • Cell 1: rods and cones (sensing stimuli)
    • Cell 2: bipolar cells (transduction and transformation)
    • Cell 3: gangilon cells (affterent nerve)

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