Protein
Protein is an important component of every cell in the body. Hair and nails are mostly made of protein. Your body uses protein to build and repair tissues. You also use protein to make enzymes, hormones, and other body chemicals. Protein is an important building block of bones, muscle, cartilage, skin, and blood.

Along with fat and carbohydrates, protein is a "macronutrient," meaning that the body needs relatively large amount of it. Vitamins and minerals, which are needed in only small quantities, are called "micronutrients." But unlike fat and carbohydrates, the body does not store protein, and therefore has no reservoir to draw when it needs a new supply.

So you may assume the solution is to eat protein all day long. Not so fast, say nutritionists.

The truth is, we need less total protein that might think. But we could all benefit for getting more protein from better food sources (Reference: https://www.webmd.com/men/features/benefits-protein)

Blood
Blood is a specialized body fluid. Blood has many functions, including;

> transporting oxygen and nutrients to the lungs and tissues
> forming blood clots to prevent excess blood loss
> carrying cells and antibodies that fight infection
> bringing waste products to the kidneys and liver, which filter and clean the blood
> regulating body temperature

The blood that runs through the veins, arteries, and capillaries is known as whole blood, a mixture of about 55 percent plasma and 45 percent blood cells. About 7 to 8 percent of your total body weight is blood. An average-sized man has about 12 pints of blood in his body, and an average-sized woman has about nine pints.

Components of Blood
Plasma - The liquid component of blood.

Red Blood Cells (Erythrocytes) - It's known for their bright red color

White Blood Cells (Leukocytes) - It protect body from infection

Platelets (Thrombocytes) - It help the blood clotting process

(Credit: https://www.hematology.org/Patients/Basics)