Skip to content
KinPilot™Learn & Explore
Menu
← TopicsReading path →

Grades 3–5 · Organisms

How can a chick breathe inside an unbroken egg?

An eggshell looks solid, but it has many tiny pores. These openings let gases move between the air outside and the developing chick inside. An intact shell is not an airtight wall.

W012 visual explanationGases cross pores in the shell; oxygen in; CO₂ out; shell; vessel network; Embryo membranes exchange gases before lung breathing begins.Gases cross pores in the shelloxygen inCO₂ outshellvessel networkEmbryo membranes exchange gases before lung breathing begins.

In the diagramGases cross pores in the shelloxygen inCO₂ outshellvessel networkEmbryo membranes exchange gases before lung breathing begins.

An enlarged shell pore links outside air with blood vessels in an embryo’s membrane. Oxygen moves inward and carbon dioxide outward; the embryo’s lungs are not shown as the early gas-exchange surface.

Early in development, the chick does not breathe air with its lungs as a hatched bird does. Blood vessels spread through membranes near the shell. Oxygen moves inward through the pores and membranes, reaches the blood, and is carried to growing tissues.

The tissues use oxygen and produce carbon dioxide. That gas travels back toward the shell and moves out. Gases move overall from places where they are more concentrated toward places where they are less concentrated; no tiny door has to pull each gas through.

Near hatching, the chick reaches the air space at the broad end of the egg and begins using its lungs. The method changes as the chick develops. Water vapor also escapes through pores, so the shell connects the chick with its surroundings in more than one way.

About this explanation

Starting knowledge: Know that living animals use oxygen and give off carbon dioxide.

Sources

  • Pennsylvania State University Extension — The Parts of the Egg
  • Pennsylvania State University Extension — Physiological Processes within the Egg
← Grades 3–5 topics