Answer:
A callus is a hardening of skin, keratin is the protein which is abundant in callus. Skin is a protective layer against a external environment. Outer layer of skin consist of keratin which is also found in hair. Callus is the accumulation of dead cells result due to friction and pressure exerts on the part in which they are present. The keratin component (keratinocytes) remains undifferentiated in these dead cells which causes hardening in callus.
Answer:
i think nicotine travels through blood and we know blood reaches the right ventricle first
maybe right ventricle
Four unifying principles form the foundation of modern biology<span>: cell theory, evolutionary theory, the gene theory and the </span>principle<span> of homeostasis. These </span>four principles<span> are the founding principles of each category of biology</span>
