PseudopodAn arm of the cell that closes around a particle.
LysosomeA small bag of digestive enzymes.
Cell membraneThe boundary of the cell; it folds in around a particle.
ReceptorA surface protein that recognizes a particle to take in.
Eating a bacterium 5
BacteriumThe particle the cell takes in and breaks down.
PhagosomeA bag of cell membrane closed around the bacterium.
PhagolysosomeA phagosome joined by lysosomes; enzymes digest the bacterium.
MHC class II moleculeIt shows a piece of the bacterium to helper T cells.
ExocytosisLeftover debris is released from the cell.
How this list was compiled: Every name and detail line was read on 2026-10-03 and kept only where two independent sources give it. (1) Wikipedia, text only: Macrophage, Phagocytosis, Phagosome, Phagolysosome, Lysosome and Cell nucleus, https://en.wikipedia.org/wiki/Macrophage and https://en.wikipedia.org/wiki/Phagocytosis . (2) Phagocytosis: A Fundamental Process in Immunity, BioMed Research International (2017), open access, read in full through Europe PMC, https://europepmc.org/article/PMC/PMC5485277 . (3) US National Institute of Allergy and Infectious Diseases, Immune Cells, https://www.niaid.nih.gov/research/immune-cells . (4) US National Human Genome Research Institute, Talking Glossary: Nucleus, Lysosome and Plasma Membrane, https://www.genome.gov/genetics-glossary/Lysosome . (5) Textbook passages found by archive.org's full-text search: Immunology: Mucosal and Body Surface Defences (2012), https://archive.org/details/immunologymucosa0000will ; Blood Cell Formation and the Cellular Basis of Immune Responses (1979), https://archive.org/details/bloodcellformati0000hama ; Functional Histology (1980), https://archive.org/details/functionalhistol00whea_0 ; Microbiology: Principles and Explorations (2006), https://archive.org/details/microbiologyprin00blac . The drawing is our own. Licence: own work
The drawing: Drawn for this site on 2026-10-03 from plain geometry. Own original drawing; nothing traced or copied. Licence: own work
How it works
This macrophage cell diagram has two views. The first names the parts of one cell. The second follows phagocytosis from left to right, as the cell takes in a bacterium and breaks it down.
Read the full guide
The cell
A macrophage is a white blood cell. Its membrane carries receptors and pushes out arms called pseudopods. Inside are the nucleus and many lysosomes, small bags of digestive enzymes.
Eating a bacterium
Receptors catch the bacterium and pseudopods close around it. Inside the cell it sits in a phagosome. Lysosomes fuse with the phagosome to make a phagolysosome, and their enzymes break the bacterium up. Leftover debris leaves by exocytosis, and one piece is shown on the surface in an MHC class II molecule.
Phagosome plus lysosome makes phagolysosome: the name is the two joined.
Questions and answers
What does a macrophage do?
It is a white blood cell that takes in and digests bacteria, dead cells and debris, a process called phagocytosis. It also shows pieces of what it has digested to other immune cells.
What are the steps of phagocytosis?
Receptors on the cell recognize the particle. Pseudopods close around it and take it into the cell in a phagosome. Lysosomes fuse with the phagosome to make a phagolysosome, where enzymes break the particle down.
What is the difference between a phagosome and a phagolysosome?
A phagosome is the bag of membrane that forms around a particle the cell has taken in. It becomes a phagolysosome when lysosomes fuse with it and add their digestive enzymes.
What does the word macrophage mean?
Big eater, from Greek. The cell is named for its ability to take in and break down bacteria.