Answer:
Kupffer cells, also known as stellate macrophages due to their particular structure while viewed under a microscope, were first identified by scientist Karl Wilhelm von Kupffer, after whom the cells were named, in 1876.
These cells, whose origin is in the yolk sack during fetal development, later on move to the liver where they will stay and further differentiate into their mature versions.
These cells are part of the liver cells, and are found particularly on the walls of the sinusoids, where they perform their two most important tasks. First, these cells are part of the immune system, as they are essentially macrophages. However, their role is pretty unique, as they are responsible not just for phagocytosis of invading bacteria, and other pathogens, and initiating immune responses, but also, this cell plays a role in decomposing red blood cells who are dying, and taking up the hemoglobin from them to further break that into reusable globin, and the heme group, from which iron is further extracted to be re-used and also to create bilirrubin, a part of bile.
Finally, these cells have been found to be connected to hepatic cirrhosis, as in their process of detoxifying ethanol, they produce toxins that force the liver cells to produce collagen, and thus to become fibrous.
The tough, thin outer membrane covering the bones is called the periosteum.
Answer:
• Penile erections and sexual activity
After circumcision, nighttime and morning erections often cause pain because they pull on the skin stitches and cause the man to wake up. The pain usually causes the erection to subside; this relaxes the tension on skin stitches, and the pain goes away.
Explanation:
Answer:
Intramembranous ossification:
Intramembranous ossification, the development of osseous tissue occurs without the cartliage formation. The bone forms on the mesenchyme tissue. No intermediate cartilage is formed in this type of ossification. This process is important for the formation of flat bones.
Endochondral ossification:
Endochondral ossification, the development occurs from the center and true bone tissue is replaced in this type of ossification. The cartilage formation occur in this process. An intermediate cartilage is formed in this type of ossification. This process is important for the formation of long bones.
