Eye Anatomy | How You Actually See (Special Senses)

Video Description

Content: 00:00 Introduction & Content 02:12 Layers of the Eye (Tunics) 03:20 Fibrous Layer of the Eye 03:29 Sclera 05:01 Cornea 06:46 Vascular Layer of the Eye 06:57 Choroid 07:46 Ciliary Body 10:33 Iris 12:27 Neural (inner) Layer of the Eye 12:34 Retina 16:25 Lens 18:05 Vitreous Body 19:40 Anterior and Posterior Chambers 20:02 Flow of Aqueous Humor 21:22 Eyelids 23:17 Conjunctiva 24:18 Lacrimal Apparatus 25:45 Ending 🫀Help me make more free educational content: youtube.com/channel/UCEr7pkSXVsHcBLLBcJAGV-Q/join 📲Other Links: Website: https://taimtalksmed.com/ Instagram: https://www.instagram.com/taimtalksmed/ Discord: https://discord.com/invite/DENMUpS8ey In this video I break down the anatomy of the human eye step-by-step, explaining how structures like the cornea, lens, retina, and optic nerve transform light into vision. Fibrous Layer (Tunica fibrosa) - Sclera: tough outer coat maintaining eye shape - Episclera: thin vascular connective tissue layer - Scleral stroma: dense collagen giving sclera its white color - Lamina fusca: pigmented layer preventing internal light scatter - Scleral sulcus: groove marking the cornea–sclera junction - Cornea (Cornea): major refracting surface bending incoming light - Epithelium: highly innervated layer detecting irritation - Bowman’s layer: rigid sheet adding structural strength - Stroma: organized collagen responsible for corneal clarity - Descemet’s membrane: strong basement membrane - Endothelium: pumps fluid to keep cornea transparent Vascular Layer (Tunica vasculosa) - Choroid (Choroidea): vascular, pigmented layer supplying retina and absorbing stray light - Ciliary ring + corona ciliaris: base and folded region of ciliary body - Ciliary processes: produce aqueous humor via non-pigmented epithelium - Zonular fibers (Fibrae zonulares): suspend lens and transmit tension - Ciliary muscle: circular + radial fibers adjusting lens shape for near/far focus - Parasympathetic pathway (EW nucleus → CN III → ciliary ganglion → short ciliary nerves): drives accommodation - Sympathetic fibers: relax ciliary muscle for distance vision - Iris (Iris): melanocyte-rich diaphragm controlling pupil size - Pupil (Pupilla): opening regulating light entry - Sphincter pupillae: constricts pupil in bright light (miosis) - Dilator pupillae: enlarges pupil in dim light (mydriasis) Nervous Layer (Retina) - Photoreceptors (rods + cones): detect light and color - Horizontal cells: integrate lateral visual signals - Bipolar cells: transmit signals from photoreceptors to ganglion cells - Amacrine cells: refine temporal and contrast processing - Ganglion cells: axons form the optic nerve - Macula lutea: central vision and high acuity - Fovea centralis: cone-only region responsible for finest detail - Optic disc: blind spot where CN II exits - Ora serrata: jagged retinal boundary where neural part ends - Retinal pigmented epithelium: absorbs light and supports photoreceptors Lens - Lens capsule: elastic outer covering anchoring zonular fibers - Lens cortex: newer fibers with high transparency - Lens nucleus: older, compacted fibers stiffening with age - Lens fibers: elongated cells packed with crystallins for refraction Posterior Eye - Vitreous chamber: space behind lens - Vitreous body: gel maintaining shape and retinal position - Hyaloid canal: remnant of fetal hyaloid artery Anterior Segment - Anterior chamber: between cornea and iris - Posterior chamber: between iris and lens - Aqueous humor flow: ciliary body → posterior chamber → pupil → anterior chamber - Iridocorneal angle: site of drainage - Trabecular meshwork → Schlemm’s canal: major outflow pathway controlling IOP - Uveoscleral pathway: secondary outflow through ciliary body Accessory Visual Structures - Eyelids (Palpebrae): protect and spread tear film - Tarsal plates: connective tissue giving eyelids structure - Palpebral orbicularis oculi: closes eyelids during blinking - Levator palpebrae superioris: elevates upper lid (CN III) - Superior tarsal muscle: sympathetically controlled lid elevation - Eyelashes (Cilia): trap airborne debris - Tarsal glands: oily secretion preventing tear evaporation - Ciliary and sebaceous glands: support lash follicles Conjunctiva - Palpebral conjunctiva: lines inner eyelids - Bulbar conjunctiva: covers sclera - Conjunctival fornix: fold allowing eyelid movement - Conjunctival sac: pocket where eyedrops collect Lacrimal Apparatus (Apparatus lacrimalis) - Lacrimal gland: produces tears (CN VII) - Excretory ducts: deliver tears to eye surface - Lacrimal caruncle: medial pink structure - Lacrimal puncta: drain tears into canaliculi - Lacrimal canaliculi → lacrimal sac → nasolacrimal duct → inferior nasal meatus: tear drainage into nose Clinical Notes - Jaundice of sclera, conjunctivitis, cataracts, floaters, glaucoma, Horner’s syndrome, tractional retinal detachment Sources: Memorix Anatomy • Gray’s Anatomy • Bergman’s Variation Atlas Programs: Complete Anatomy, Biorender, PowerPoint