myeloid
Meaning of myeloid: One of the two great branches of blood cell production, and the branch that supplies everything except lymphocytes.
Definition of myeloid
Myeloid describes the bone marrow and, more often, the family of blood cells that develops there apart from lymphocytes. Red cells, platelets and most infection fighting white cells belong to the myeloid line. The word appears in the names of blood cancers to state which line the abnormal cells came from, as in acute myeloid leukemia.
How myeloid is built
- myel/o Combining form · Greek bone marrow, spinal cord
- -oid Suffix · Greek resembling, like
A medical term is read from its ending backwards: the suffix first, then the prefix, then the root. See all 223 word parts.
Which cells are myeloid?
All blood cells begin as one kind of stem cell in the bone marrow. Early on, that stem cell commits to one of two paths. The lymphoid path produces lymphocytes, the cells of targeted immunity. The myeloid path produces everything else.
| Myeloid cell | What it does |
|---|---|
| Red cells | Carry oxygen |
| Platelets | Plug damaged vessels and start clotting |
| Neutrophils, eosinophils, basophils | Attack bacteria and parasites, drive allergy |
| Monocytes and macrophages | Swallow debris and microbes, alert other immune cells |
| Mast cells and dendritic cells | Release alarm chemicals, present material to T cells |
Why does the label matter in leukemia?
Leukemia is named by the branch the abnormal cells belong to and by how fast the illness moves. Acute myeloid leukemia arises from immature myeloid cells that stop maturing and pile up in the marrow, crowding out normal production. Acute lymphoblastic leukemia arises from the other branch. The two can look similar on a blood count but answer to different drugs, so the laboratory identifies the line from surface markers and gene changes before treatment is chosen. The same division runs through the chronic forms.
Is myeloid the same as myelogenous?
For practical purposes, yes. Acute myeloid leukemia and acute myelogenous leukemia name one disease, and both shorten to AML. Older reports favor myelogenous, newer ones favor myeloid. A related trap is the prefix myel-, which points to marrow in some words and to the spinal cord in others. Myelopathy means damage to the spinal cord, while myelodysplasia in a blood report means faulty marrow production, and only the rest of the term settles which is meant.
What does a myeloid failure look like?
Because this branch supplies oxygen carriage, clotting and the first defense against bacteria, failure shows up as a combination rather than a single symptom: tiredness and breathlessness from low red cells, bruising and bleeding from low platelets, and repeated infections from low neutrophils. That trio arriving together is what points toward the marrow rather than toward any one organ.
Also known as
Used in a sentence
Flow cytometry confirmed that the blasts carried myeloid surface markers.
Good to know
Myeloid and myelogenous mean the same thing when leukemias are named, but the prefix myel- refers to the spinal cord in words such as myelopathy, so the rest of the term decides the meaning.
Word origin
Where “myeloid” comes from
From the Greek myelos, meaning marrow, with the ending -oid, meaning resembling.