Uterine fibroids
How a single smooth muscle cell of the uterine wall grows, under oestrogen and progesterone, into a benign tumour, and why its position decides whether it causes heavy periods or pressure symptoms.
By the end, you can
- Describe the myometrium and its response to oestrogen and progesterone.
- Explain how a fibroid arises as a benign clonal tumour rich in extracellular matrix.
- Explain why fibroids grow during the reproductive years and usually shrink after menopause.
- Distinguish submucosal, intramural and subserosal fibroids and relate each to its typical symptoms.
- Explain the mechanisms of heavy menstrual bleeding and pressure effects.
- Recognise the classic appearance, degeneration types, FIGO types and tests of fibroids, and explain how each main treatment acts on its mechanism.
What it is
Uterine fibroids (leiomyomas) are benign tumours of the smooth muscle of the uterine wall (the myometrium), each arising from a single cell and containing abundant fibrous extracellular matrix. They are classified by position: submucosal (bulging into the cavity), intramural (within the wall) and subserosal (projecting from the outer surface), with cervical fibroids as a less common site.
4 types to tell apart
- Submucosal
- Bulges into the uterine cavity beneath the endometrium; even a small one can cause heavy bleeding and affect implantation.
- Intramural
- Within the muscle wall; the commonest type. Large ones enlarge the uterus and can distort the cavity.
- Subserosal and pedunculated
- Projects outwards from the surface, sometimes on a stalk; causes pressure effects rather than heavy bleeding, and a stalk can twist.
- Cervical
- Arises in the cervix; uncommon, but can press on the bladder or ureters low in the pelvis.
US spelling: tumours → tumors, oestrogen → estrogen.
Normal function
The myometrium
The wall of the uterus is mostly myometrium: thick, interlacing bundles of , each a spindle with one central , with blood vessels and connective tissue between the bundles. The endometrium lines it on the inside, and the peritoneum (serosa) covers it on the outside.
Myometrial cells carry receptors for oestrogen and progesterone. In pregnancy these hormones make the cells enlarge and multiply, so the uterus grows many times its size, and the cells then contract in labour. Outside pregnancy, myometrial contractions during a period help compress the vessels that open as the endometrium sheds, which limits blood loss.
Underlying change · Step 1 of 5
One cell grows into a benign tumour
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Underlying change · Step 2 of 5
Oestrogen and progesterone drive growth
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 3 of 5
Position decides the symptoms
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 4 of 5
Heavy menstrual bleeding
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Consequences · Step 5 of 5
Bulk and pressure on neighbouring organs
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Symptoms and signs
Symptoms, signs and findings
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Exam detail
Exam detail
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Treatment
How treatment works
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Recap
Recap
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Self-check
Check your understanding
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .