Diseases restricting lower thoracic/abdominal volume (e.g. obesity, diaphragmatic hernia, or the presence of ascites). Pleural thickening. Pathophysiology
In normal respiratory function, the air flows in through the upper airway, down through the bronchi and into the lung parenchyma (the bronchioles down to the alveoli) where gas exchange of carbon dioxide and oxygen occurs. During inspiration, the lungs expand to allow airflow into the lungs and thereby increasing total volume. After inspiration follows expiration during which the lungs recoil and push air back out of the pulmonary pathway. Lung compliance is the difference of volume during inspiration and expiration.Restrictive lung disease is characterized by reduced lung volumes, and therefore reduced lung compliance, either due to an intrinsic reason, for example a change in the lung parenchyma, or due to an extrinsic reason, for example diseases of the chest wall, pleura, or respiratory muscles. Generally, intrinsic causes are from lung parenchyma diseases that cause inflammation or scarring of the lung tissue, such as interstitial lung disease or pulmonary fibrosis, or from having the alveoli air spaces filled with external material such as debris or exudate in pneumonitis. As some diseases of the lung parenchyma progress, the normal lung tissue can be gradually replaced with scar tissue that is interspersed with pockets of air. This can lead to parts of the lung having a honeycomb-like appearance.
The distance from one ora to the other (or macula), the most sensitive area along the horizontal meridian is about 32 mm.In section, the retina is no more than 0.5 mm thick. It has three layers of nerve cells and two of synapses, including the unique ribbon synapse. The optic nerve carries the ganglion cell axons to the brain, and the blood vessels that supply the retina. The ganglion cells lie innermost in the eye while the photoreceptive cells lie beyond. Because of this counter-intuitive arrangement, light must first pass through and around the ganglion cells and through the thickness of the retina, (including its capillary vessels, not shown) before reaching the rods and cones. Light is absorbed by the retinal pigment epithelium or the choroid (both of which are opaque). The white blood cells in the capillaries in front of the photoreceptors can be perceived as tiny bright moving dots when looking into blue light. This is known as the blue field entoptic phenomenon (or Scheerers phenomenon). Between the ganglion cell layer and the rods and cones there are two layers of neuropils where synaptic contacts are made. The neuropil layers are the outer plexiform layer and the inner plexiform layer. In the outer neuropil layer, the rods and cones connect to the vertically running bipolar cells, and the horizontally oriented horizontal cells connect to ganglion cells. The central retina predominantly contains cones, while the peripheral retina predominantly contains rods. In total, there are about seven million cones and a hundred million rods.