You have just received your flu vaccine in your deltoid muscle. explain all of the layers and structures the needle passed through

The layers include the; epidermis, dermis, subcutaneous layer, a connective tissue layer, muscle.

The epidermis is the outermost layer and is made of flat squamous cells that have a lot of keratin.

The dermis is the layer below the epidermis and is much thicker than the epidermis and mainly composed of fibroblasts. It is also filled with blood and lymph vessels, glands and sensory receptors.

The subcutaneous is composed mainly of fat cells, called adipocytes, that act as an insulator layer. The connective tissue layer below has elastin and collagen fibres that connect the skin with the muscle tissue below.

helicase, i think thats it

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!