Final answer:
Keratinocytes in the spinous and granular layers of the epidermis are joined together through desmosomes. The cells become flattened and generate proteins such as keratin and keratohyalin. As the cells die, they leave behind keratin, keratohyalin, and cell membranes.
Step-by-step explanation:
In the spinous and granular layers of the epidermis, keratinocytes are joined together through a structure called desmosomes. Desmosomes are intercellular junctions that connect adjacent cells and provide strength and cohesion to the tissue.
These desmosomes interlock with each other and form spiny projections on the surface of the cells, hence the name "stratum spinosum." This layer is composed of 8 to 10 layers of keratinocytes that are formed as a result of cell division in the stratum basale.
In the stratum granulosum, the keratinocytes further change and become flattened. They generate large amounts of proteins called keratin and keratohyalin, which make up the bulk of the keratinocyte mass in this layer. As the cells die, the nuclei and other cell organelles disintegrate, leaving behind the keratin, keratohyalin, and cell membranes.