Immunoglobulin A (IgA, also referred to as sIgA) is an antibody that plays a critical role in immune function in the mucous membranes. More IgA is produced in mucosal linings than all other types of antibody combined; between three and five grams are secreted into the intestinal lumen each day. This accumulates up to 15% of the total immunoglobulin produced in the entire body.
The beginning of the optic nerve in the retina is called the optic nerve head or optic disc. Since there are no photoreceptors (cones and rods) in the optic nerve head, this area of the retina cannot respond to light stimulation.As a result, it is known as the blind spot, and everybody has one in each eye.rom there, the nerve fibers become the optic tract, passing through the thalamus and turning into the optic radiation until they reach the visual cortex in the occipital lobe at the back of the brain. This is where the visual center of the brain is located.
The occipital lobes are the visual processing center of mammalian brains. The primary visual area is Brodmann area 17, located in the interior portion of the occipital lobe at the calcarine sulcus and sometimes continuing onto the surface of the lobe.The lobes' Peristriate regions are the sites for center visuospatial processing, for color discrimination and for discrimination of movement.he front edge of the occipital lobe is separated from the parietal lobe by the Parieto-occipital sulcus. The sides of the lobe merge with the parietal lobes along a vague boundary defined by several lateral occipital gyri, which are separated by lateral occipital sulcus.