Exoskeleton and Endoskeleton
Multicellular organisms e.g. man meet their needs through use of specialized systems that they have in their bodies. Examples of such include:
1. cardiovascular system composed of heart, veins and arteries which facilitate transport of nutrients to all parts of the body .
2. Skeletal system composed of bones, joints, ligaments and cartilage whose function is support and protection of the body. <span>
3. Digestive system composed of mouth, esophagus, stomach , small and large intestines whose function is breakdown of food and absorption of nutrients.</span>
Smokers, who are exposed to secondhand smoke, evokes craving to the smoker according study funded by the National Institute on Drug Abuse, part of the National Institutes of Health. The same thing happens to both smokers and nonsmokers when exposed to secondhand smoke for an hour.