Which part of the uterus is called the living ligature of the uterus?

UPPSC-2021

Obstetrics & Gynaecology

Easy

Appeared in: UPPSC-2021

Explanation

The middle layer of the myometrium is referred to as the 'living ligature' of the uterus.
It is the thickest layer of the uterine wall and contains interlacing smooth muscle fibers arranged in a figure-of-eight pattern.
These fibers surround the blood vessels that supply the placenta.
Following delivery, uterine contraction causes these criss-crossing fibers to constrict the blood vessels, achieving hemostasis and preventing postpartum hemorrhage.
This physiological clamping mechanism functions like a natural, living tourniquet.

Option A: The perimetrium is the thin, outermost serous layer of the uterus. It serves a protective function and is not composed of muscle, so it cannot contract to constrict blood vessels.
Option B: The endometrium is the inner mucosal lining of the uterus. It is where the embryo implants and is shed during menstruation. It is glandular and vascular but lacks the muscular structure needed for contraction and hemostasis.
Option D: The inner layer of the myometrium consists mainly of circular muscle fibers. While it contributes to uterine contractions, the primary 'ligature' effect comes from the thick, interlacing fibers of the middle layer.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy and physiology of the uterus, specifically the function of the myometrium in postpartum hemostasis as background academic context rather than a clinical decision trigger.
A nurse's primary responsibility immediately postpartum is to assess the uterine fundus for firmness. A firm, 'well-contracted' uterus indicates that the 'living ligature' is functioning correctly, minimizing the risk of PPH.
If the uterus is found to be boggy (soft), it signifies uterine atony, and immediate fundal massage is required to stimulate contraction and prevent hemorrhage.
Administration of uterotonic medications like oxytocin is a standard part of active management of the third stage of labor to augment the natural contraction of the myometrium.

How to Approach the Question

First, identify the key phrase in the question: 'living ligature'. This is a specific anatomical and functional term.
Recall the layers of the uterine wall: Perimetrium (outer), Myometrium (middle, muscular), and Endometrium (inner).
Associate the term 'ligature' (something that ties or binds) with the function of stopping bleeding. In the context of the uterus, this relates to controlling bleeding after childbirth.
Connect the function of stopping bleeding with the muscular layer, the myometrium, which contracts.
Differentiate between the sub-layers of the myometrium. The unique criss-cross fiber arrangement of the middle layer is specifically responsible for constricting blood vessels.
Eliminate the other options: the perimetrium is a protective covering, and the endometrium is the lining for implantation. The inner myometrium does not have the same powerful ligature effect as the middle layer.

Concept Tested & Keywords

Concept Tested: Anatomy and physiology of the uterus, specifically the function of the myometrium in postpartum hemostasis.
Stem keywords: uterus, living ligature
Lead-in keywords: Which part
Negative lead-in flag: false

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