【PEP】Junior High Biology Grade 7, Vol. 2: The Red Flow of Life

Blood, known as the "river of life" flowing within us, is not only a carrier of nutrients but also a defender of health. It is a fluidconnective tissue. In adults, blood volume accounts for approximately $7\% \sim 8\%$ of body weight.

Core Components Explained

Plasma: The liquid matrix of blood.$90\%$ is water, with the rest consisting of proteins, glucose, inorganic salts, etc. Its role is to carry blood cells and transport nutrients and metabolic waste.
Blood Cells: Includes red blood cells (oxygen transport), white blood cells (immune defense), and platelets (blood clotting and hemostasis).
Hematopoietic Stem Cells: The "seeds of life" in blood, found in bone marrow, with remarkable ability to divide and differentiate, continuously producing new blood cells.

Glossary: Stem Cells

In animals and humans, stem cells are primitive cells with self-renewal capacity and multilineage differentiation potential. Like "universal cells," they can differentiate into various tissue and organ cells. Hematopoietic stem cells are among the most well-studied types.

QUESTION 1

When observing a permanent human blood smear under a microscope, which cells are the most numerous, biconcave disc-shaped, and lack a nucleus when mature?

White Blood Cells

Red Blood Cells

Platelets

Hematopoietic Stem Cells

QUESTION 2

How would you distinguish between red blood cells and white blood cells?

Red blood cells are large and have a nucleus; white blood cells are small and have no nucleus

Red blood cells are few and red; white blood cells are many and white

Red blood cells are numerous and lack a nucleus; white blood cells are fewer, have a nucleus, and are larger in size

QUESTION 3

When the body loses large amounts of sweat from intense exercise or suffers from severe diarrhea, which blood component is primarily lost, and how should it be replenished?

Red blood cells are lost; a whole blood transfusion is needed

Water and inorganic salts from the plasma are lost; drink light salt water or receive intravenous saline

White blood cells are lost; take antibiotics

QUESTION 4

Which of the following most comprehensively describes the function of plasma?

Specifically transports oxygen and carbon dioxide

Carries blood cells and transports nutrients and waste

Only responsible for engulfing pathogens and protecting the body

QUESTION 5

As blood flows through the circulatory system, what key change in blood composition occurs during the pulmonary circulation pathway?

Deoxygenated blood becomes oxygenated blood, with increased oxygen content

Oxygenated blood becomes deoxygenated blood, with decreased oxygen content

The number of white blood cells increases significantly