Have you learned about these blood knowledge?

The human body is different at different stages starting from the embryo, with each tissue and organ participating in hematopoiesis and playing its own role.

1. Blood Production

The production of blood is very interesting, like a relay race on the track and field, with participants including the embryo's yolk sac, liver, spleen, kidneys, lymph nodes, bone marrow, etc.

Hematopoiesis begins in the third week of human embryo development. At this stage, no organs have yet formed, and an embryonic tissue called the yolk sac takes on the primary responsibility for hematopoiesis.

In the sixth week of human embryo development, human organs are formed, and the liver then produces blood.

In the third month of human embryo development, the spleen is the main hematopoietic organ.

After the fourth month of human embryo development, the bone marrow begins to produce hematopoiesis, which is the most important hematopoietic tissue in the human body.

Image source: Pixabay

After birth, the liver and spleen stop producing blood, and the bone marrow takes over the entire responsibility for producing blood.

Blood cells include red blood cells, white blood cells, platelets, etc. They each have their own functions, but they all come from the same type of cell - multifunctional stem cells. It is through the proliferation, differentiation and maturation of these cells that they become various terminal blood cells flowing in the blood vessels.

2. Human blood volume

Don't rush to replenish blood if you lose a small amount of blood, because the body's "blood reservoir" will quickly replenish blood circulation.

Blood accounts for about 7%-8% of an adult's body weight, which means that an adult weighing 60 kg has a body full of 8 mineral water bottles. However, only 70%-80% of the blood actually circulates in the body, and the rest is stored in the "human blood bank" such as the liver and spleen. When the body loses a small amount of blood, the blood stored in the "human blood bank" will be released immediately to replenish the circulating blood at any time.

3. Composition of blood

The white blood cells and platelets in the blood are like the body's guards, one resists the invasion of bacteria, viruses and other foreign substances, and the other coagulates and stops bleeding.

Blood is composed of 55%-60% plasma and 40%-45% blood cells (red blood cells, white blood cells, platelets). The main blood cells are red blood cells, which transport oxygen to various parts of the body and transport the carbon dioxide produced by metabolism to the lungs to be expelled from the body with exhalation; the second is white blood cells, which can help the human body resist the invasion of bacteria, viruses and other foreign bodies, and are the guardians of human health; the third is platelets, which can play a role in coagulation and hemostasis when the human body bleeds. 90% of plasma is water, and the rest is substances required for human metabolism such as protein, sodium, potassium, hormones, enzymes, etc. to maintain normal life activities of the human body.

4. Blood typing

The world is rich and colorful, and the blood type system also has many types.

At present, there are more than 40 blood group systems discovered by humans. The ABO and Rh blood group systems are mainly related to blood transfusion in my country.

ABO blood type: Type A contains A antigen on the red blood cells; Type B contains B antigen on the red blood cells; Type O contains neither A antigen nor B antigen on the red blood cells; Type AB contains both A antigen and B antigen on the red blood cells.

Rh blood type: Rh positive means the presence of D antigen on red blood cells, and Rh negative means the absence of D antigen on red blood cells. More than 99% of people in my country are Rh positive, and only 0.3% of the Han people are Rh negative.

(Knowledge point source: Donate blood while you are young)

Contributor: Chongqing Jiulongpo District Science Popularization Creation and Communication Association Review expert: Tao Ran, deputy chief physician of Jiulongpo District Center for Disease Control and Prevention Statement: Except for original content and special instructions, some pictures are sourced from the Internet for non-commercial purposes and are only used as popular science materials. The copyright belongs to the original author. If there is any infringement, please contact us to delete it.