Organ
Isthmus of the uterine tube
The narrow muscular segment beside the uterine wall
High-yield
Isthmus is the narrow extrauterine segment; interstitial tube lies within the uterine wall. Both differ from the wider, folded ampulla.
Overview
The isthmus links the broad ampulla with the intramural portion of the uterine tube. Its narrow lumen has fewer mucosal folds and a relatively thick muscular wall. The intramural segment is a separate short continuation through the myometrium.
Reference facts
- Location
- Immediately lateral to the uterus, between the ampulla and the intramural tubal segment.
- Parts
- A narrow extrauterine segment with prominent smooth muscle, followed medially by the distinct interstitial portion in the myometrium.
- Blood supply
- Mainly uterine tubal branches with ovarian arterial anastomoses.
- Innervation
- Autonomic fibers from uterine and ovarian plexuses regulate muscular and vascular activity; sensory fibers follow visceral pathways.
- Venous/Lymphatic drainage
- Veins join uterine and ovarian networks; lymphatic connections reach pelvic and lumbar nodes.
- Relations
- Near the uterine horn, superior to the uterine attachments of the round and ovarian ligaments.
- Function
- Participates in coordinated transport of gametes and the early embryo through smooth-muscle activity, secretions and ciliary transport.
Clinical correlation
Ectopic implantation can occur in the isthmic or interstitial portions. Bleeding risk depends on the implantation site and surrounding vessels, but the segment alone cannot establish when rupture will occur. 'Interstitial' and 'cornual' are not interchangeable descriptions in every context.
Frequently asked questions
Where is the isthmus of the uterine tube located?
The isthmus of the uterine tube lies immediately lateral to the uterus, between the ampulla and the intramural tubal segment.
What does the isthmus of the uterine tube do?
Participates in coordinated transport of gametes and the early embryo through smooth-muscle activity, secretions and ciliary transport.
What are the parts of the isthmus of the uterine tube?
A narrow extrauterine segment with prominent smooth muscle, followed medially by the distinct interstitial portion in the myometrium.
What is the blood supply of the isthmus of the uterine tube?
Mainly uterine tubal branches with ovarian arterial anastomoses.