C. Choroid: L.C.T. rich in b.v. & pigments. Function: provide nutrients to retina.
Ⅲ. Retina 10 layers of histological structures 4 layers of cells: Ganglion Cells Bipollar Cells Optic Cells Pigment Cells
A.Pigment epithelial cells 1 layer, columnar, rich in melanin granules. B. Photoreceptor cells (optic cells) including: rod cells cone cells
Rod cells ： (1) photosensitive bipolar neurons. (2) a body, two opposite processes. (3) outer process: Inner segment: rich in Mt, rER, r. Outer segment: flattened membranous disks (visual purple or rhodopsin). Sensitive to low intensity light, (for night vision). Lack of Vitamin A leads night blindness. (4) inner process: the end knob synapses with the dendrite of bipolar cells.
Cone cells: Differ from rods in: (1). Outer segments: pyramidal disks continuous with covering cellular membrane. (2). 3 types of cones contain variety photopigments (iodopsin) on disks, sensitive to red, green, & blue light. (3). Sensitive to high intensity light & colors (day vision & color distinguishing), visual acuity is better than rods. Lack of them leads to color blindness.
C. Bipolar cells: An axon & a dendrite, they synapse with ganglion cells & photoreceptor cells respectively. D. Ganglion cells: The dendrites synapse with bipolar cell. The axons concentrate together to form optic nerve.
Müller cells Neuroglia, extend entire thickness of retina; support, nourish and insulate the retinal neurons and fibers.
1. Bony labyrinth: there are 3 portions: Osseous semicircular ducts, vestibule and cochlea. filled with perilymph.
2. Membranous labyrinth: Suspends in perilymph & filled with endolymph. Consist of 4 parts (Membranous semicircular ducts, utricle, saccule, and cochlear duct).
3. Cochlear duct & the organ of Corti A. Cochlear duct: Triangular shape filled with endolymph.
u Roof: vestibular membrane. u Outer wall: stria vascularis, rich in blood capillaries (secrete endolymph) u Floor: osseous spiral lamina & basilar membrane. The organ of Corti locates on the membrane.
B. The organ of Corti Locate on the basilar membrane. A tectorial membrane covers on the Corti. There are auditory strings (collagenous fibrils) in basilar membrane. The length of fibrils is responsible for sound frequencies.
a. Supporting cells: Pillar cells: Inner & outer. Tall columnar with wide broad base & contacted apices. A inner tunnel between them. Phalangeal cells: At inner & outer sides of pillar cells respactively. The apex : finger-like process for supporting hair cells.
b. Hair cells: u Inner (1 row) & outer (3-5 rows). u On inner & outer phalangeal cells respectively. u Stereocilia touch with the tectorial membrane. u Nerve ending of cochlear N. synapses with hair cells.
Homework Explanation of rods, cones, optic papilla, fovea, Müller cells. Describe the structure of the organ of Corti.