Where does blood come from?
While an embryo is still developing, blood cell formation happens in the yolk sac. As organs develop and mature they take over the production - namely the liver and spleen. When bones undergo ossification and bone marrow develops, they will take over hematopoiesis. In children most hematopoiesis takes place in the long bones. As one matures, blood production happens mainly in the flat bones such as the pelvis, cranium and sternum.
Structure of Blood
Blood is the only fluid tissue in the body. It is classified as connective tissue. All connective tissues have cells embedded in a matrix. The matrix of blood is exceptional, because it is fluid - this is the blood plasma. The cells are a variety of different blood cells, all with their specific function.
Parts of Blood
Physical Characteristics of Blood
- Color: oxygen-rich blood is scarlet red while oxygen-poor blood is dull red
- pH: must remain between 7.35 and 7.45
- Temperature: 100.4°F
- Volume: 5-6 liters (healthy adult man)
- Blood makes up 8% of body weight
Blood as Transportation
Blood transports everything that must be carried from one place to another.
- body heat
Crash Course - Blood Part 1
basic components of blood, hemostasis & blood types
Crash Course - Blood Part 2
structure and function of erythrocytes & hemoglobin, formation and life cycle of a red blood cell