The question that I have for this week revolves around the lack of cancer in muscular tissue, or a sarcoma. According to cancer.org there were 13,190 reported cases of sarcomas in 2022, with 5,130 (or nearly 39%) are expected to be lethal. Now I understand that cancers are much more likely to develop in areas with cell turnover is higher, and there is not much for cell death/reproduction occurring in muscles, but even brain cancers have nearly double the cases at 25,050 last year. I would imagine that muscles, with tissue damage occurring during exercise, would have a higher rate of cancer development compared to the brain since there is a blood-brain barrier to keep out unwanted chemicals, and there little to no cell development/replication. So is there some special mechanism or some special resistance to cancer development in muscle tissue? 

have been intrigued by how the cardiac muscle works, specifically the intercalated discs.

As we all know, the cardiac muscle only lives within the heart. The coordination of the contractions of this muscle help to pump the blood into the vessels of the circulatory system. It is striated and organized into sarcomeres, which process the same banding organization as skeletal muscles, cardiac muscles are just shorter!  These muscle fibers process mitochondria and myoglobin as ATP is being produced through aerobic metabolism. An intercalated disc is what allows the cardiac muscle to contract in the wave pattern that a heart pumps. 

Now that we have a basis of where the intercalated disc lives, lets dive a little bit more. These discs are part of the sarcolemma and contain two different structures that are important in the contraction, those would be the gap junctions and the desmosomes. Gap junctions form channels between adjacent cardiac muscle fibers that allow for electric coupling to occur. Electric coupling is when there is a depolarizing coupling and allows the quick transmission of action potentials with the coordinated contracts of the whole heart. All of that then allows for electrically connected muscle cells to a functional unit of contraction called the syncytium. The rest of the intercalated disc is made up of desmosomes, which is a cell structure that anchors the ends of the cardiac muscle fibers together so that they don’t pull apart during the contractions.