68. Phylogeny and development of organ of vision..
Covers the phylogeny and development of the vision organ, tracing how light detection in opsin-based photoreceptors grew into camera-type eyes across molluscs, chordates and vertebrates. It then follows embryonic eye formation from optic vesicles and the Pax6 gene, before describing retinal layers, the fovea, uveal parts, lens and accommodation. Mnemonics and recap questions accompany the text.
Inside: 17 sections · 16 flashcards · 10 min
Topic 69 of 105 in the MU Sofia syllabus for Biology (Medicine, Year 1). The free AceMed note covers it in 17 sections, about 1,470 words (10 min of reading), with 16 flashcards.
In this note
Phylogeny and development of organ of vision.
Overview of the Eye as an Organ of Vision
Molecular Basis of Photoreception and Vision
Phylogenetic Evolution of the Eye
Steps in Eye Evolution
Eye Types Across Species
Additional Evolutionary Adaptations
Development of the Eye
Key Developmental Stages
Genetic and Developmental Regulation
Structure of the Vertebrate Eye
Structure and Function of Uveal Components
Lens Structure and Function
Features of the Lens
Mechanism of Accommodation
RECAP QUESTIONS
MNEMONICS
Overview of the Eye as an Organ of Vision
The eye is a specialized sensory organ responsible for photoreception, which is the ability to detect light, and for vision, which is the refined processing of light into meaningful images.
Eyes are typically paired and located near the front of the body, a characteristic feature of bilaterally symmetrical animals (Bilateria).
Molecular Basis of Photoreception and Vision
Light is detected by proteins called opsins, which are part of the G protein-coupled receptor family.
Opsins require a light-sensitive molecule called retinal, derived from vitamin A, to function. Retinal absorbs visible light, something amino acids cannot do.
The type of opsin determines the specific wavelength of light that retinal will absorb, allowing for color sensitivity.
Opsins are found across almost all multicellular animals, including both bilaterians and cnidarians.
Photoreceptor cells are specialized neurons made up of:
A synaptic terminal for communication
An inner segment that contains cellular organelles
A nonmotile cilium that connects to the outer segment
An outer segment that contains stacked discs with opsins
These photoreceptors alone can only detect light, not process images or direction.
Continue reading free
The whole note, all 17 sections, is free with an AceMed account, with its 16 flashcards. Premium adds flashcard recall, highlights and Ask AI.
