Erythrocytes

Microscopic image of a monolayer of pink to red-staining erythrocytes against a white background, characteristic of a blood smear. The erythrocytes are primarily discoid shape, with some exhibiting irregular forms. Small blue to purple granules are dispersed among the erythrocytes, likely representing cellular debris or staining artifacts. The composition is a high-magnification view, providing cellular-level detail.
Figure 1: Microscopic view of red blood cells (erythrocytes) in a blood sample. Pink, round cells scattered on white background.

Erythrocytes, commonly known as red blood cells (RBCs), are empty backpacks perfect for carrying, picking up, and dropping off oxygen.

Erythrocytes are small, biconcave disc-shaped cells without a nucleus or other organelles. Their biconcave shape increases surface area-to-volume ratio, allowing for efficient gas exchange. The absence of a nucleus and organelles maximizes space for hemoglobin, the protein responsible for binding and transporting oxygen.

Nucleus

Erythrocytes have no nucleus.  In the normoblast stage of erythropoiesis, erythrocytes exocytoze their nucleus and organelle to make more room for hemoglobin.

Cytoplasm

The cytoplasm of erythrocytes is rich in hemoglobin, which gives them their characteristic red color. Hemoglobin molecules bind oxygen in the lungs and release it in tissues, facilitating oxygen transport. Each erythrocyte contains millions of hemoglobin molecules, which occupy the majority of the cell’s volume.

Function

The primary function of erythrocytes is to transport oxygen from the lungs to tissues. They also transport carbon dioxide from tissues to the lungs. This oxygen transport is essential for cellular respiration and energy production in tissues throughout the body. Erythrocytes also play a role in maintaining acid-base balance and blood viscosity.

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All Figures: Slide 86X Human blood smear, Giemsa stain, 86X scan from hematopathology normals collection
All by University of Michigan Histology, licensed under CC BY-NC-SA 3.0.

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