The Eyeball

There are 3 layers to the eyeball: the sclera-the outer most layer, which is also known as the fibrous tunic, the choroid-the middle layer, which is also know as the pigmented tunic, and the retina-the inner layer, which also known as the visual tunic. The sclera is the white of the eye and is vascular. It is white in color because of collagen and is a continuous with the dura mater. The sclera is covered by a thin membrane called conjunctiva, the conjunctiva also lines inside of the eyelid. The choroid layer lies between the sclera and the retina. It is vascular and provides oxygen and nourishment to the retina. The retina is avascular. Light hitting the retina triggers nerve impulses which are sent to the brain via fibers of the optic nerve. Photoreceptors of the retina are rod cells-perceive light, and cone cells-perceive color. The Central fovea, a small indentation in the macula of the retina, is where cones are most concentrated and the area of most acute vision.
The eye has always been a wonder to me. Thanks to world of contacts I do not have to wear extremely heavy akward glasses. I was diagnosed with cataracts about 2 years ago. Cataracts are a clouding of the lens of the eye because of a build up of deposits. It is caused by a number of things-age, injury, congenital. I come from a long line of eye diseases and poor vision. I keep reading new ways that they treat this disease. From the advice of my Optometrist I look for the alternatives to laser surgery. I have thin corneas and he has advised that laser surgery would be dangerous. We are trying to hold off as long as possible before having the intraocular lens implanted because of my age and the likelihood of cataracts reoccurring. According to the Spokane Eye Clinic the cataract surgery has a 90% success rate of the patient recovering at least some of the lost vision. My optometrist says I should have vision in an eye that has never had anything other than a few shadows.

Spinal nerves within the Vertebral Column

There are 31 pairs of spinal nerves. They consist of 8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar nerves 5 pairs of sacral nerves and 1 coccyxgeal nerve. The spinal cord passes through the vertebral foramen, it comes to an end at the conus medullaris. The filum terminale comes off the end of the conus medullaris and is a anchoring strip of fibrous tissue that attaches the spinal cord to the interior surface of the pelvic girdle. The dura mater of the spinal cord has only 1 layer unlike the dura mater of the brain that has 2 layers, the periosteal and the meningeal. The gray matter, cell bodies of the neurons, in the brain is superficial where in the spinal cord it is deep and its counterpart the white matter, mostly myelinated axons, is superficial in the spinal cord and deep in the brain.
This relates to everyday living by giving us the map of the nerves through the spinal column. Understanding which nerve controls what muscles gives me a better concept of how injuries to certain parts of the spinal cord causes parylsis.

The Peripheral Nervous System

We had Brad Haskell for lecture. We learned that the spinal cord ends at L2 region of the vertebral column. Plexuses are a weaving or braiding of a nerve and the nerves that come off from it. The principal plexuses are cervical, brachial, lumbar, and sacral plexuses. The sciatic nerve is the longest and thickest nerve in the body. Phrenic nerve controls the diaphragm injury to C5 can be life threatening. We reviewed the cranial nerve names and a few of he foramen. We went over the central canal of the spinal column.
This relates to every day living for any human being because if some reason there is an injury or the neurons misfire it effects the way our bodies work. The sensory nerves have to get the impulse to the brain in order for an impulse to be sent to the motor nerves for movement to happen.

The Brain

Meninges are the 3 wrappings around the brain. 1. The outer most layer is the Dura Mater that consists of major blood vessels. The Dura Mater is 2 layers thick around the brain, inner called the Meningeal and outer called the Periosteal, and 1 layer thick around the spinal cord. 2. Arachnoid Mater is the middle most layer there are no blood vessels in this layer, CSF is located here. 3. Pia Mater is the inner most layer that contains capillary network. We are also working on the Circulatory Pathways. Venous Pathway or Venous drainage and the Arterial Pathway. Venous drainage, CSF drains from the Superior Sagittal Sinus through the Confluence of Sinuses (point where straight sinus, s sagittal sinus, & occiptal sinus meet) then to the transverse sinuses on to the sigmoid sinuses and into the 2 internal jugular veins. Arterial Pathway, oxygen rich blood from the left side of the heart is carried to the left Atrium it then reaches the left Ventricle via the Bicuspid valve, from the left Ventricle it travels through the Semilunas valve (Aortic valve) into the Ascending Aorta to the Aortic Arch. In the Aortic Arch it goes to the right Subclavian artery and right Common Carotid artery via the Brachiocephalic, the left Common Caroid artery which feeds the Circle of Willis, and to the left Subclavian artery. It also travels out the descending Aorta to suppply blood to the Thoracic and Abdomen.
We receive many patients that have suffered strokes and or blood clots to areas of their bodies. DVT's (deep vein thrombosis) are common with our elderly. I was once involved with a code on a patient that was having a Pulmonary Emblosism, I knew it was a blood clot that had traveled to the lungs but I did not understand it completely until I started to get more in detail with this weeks study of the Circulatory pathway of blood and CSF. That same patient also had a history of strokes.