The thickest layer of uterus is
A. Endometrium
B. Myometrium
C. Perimetrium
D. Peritoneum
Correct Answer: B. Myometrium
Explanation: The thickest layer of the uterus is the myometrium.
Layers of the uterus (from innermost to outermost):
1. Endometrium – the innermost mucosal layer (thin, changes thickness during menstrual cycle, but usually only 2–8 mm thick).
2. Myometrium – the middle muscular layer (thickest layer, made of smooth muscle; during non-pregnant state it is about 10–15 mm thick, but can become much thicker during pregnancy, up to several centimeters).
3.Perimetrium – the outer serosal layer (very thin).
So, in both non-pregnant and pregnant states, the myometrium is by far the thickest layer of the uterine wall.
Other Options Details
Here is a clear description of all the options, which are the four main layers that cover or make up the uterus (from inside to outside):
A. Endometrium
• The innermost layer of the uterus.
• It is a mucous membrane (highly vascularized and glandular).
• Divided into two sub-layers:
• Stratum functionalis (functional layer) – thickens every month and is shed during menstruation.
• Stratum basalis (basal layer) remains permanent and regenerates the functional layer each cycle.
• Site of embryo implantation during pregnancy; if no pregnancy occurs, most of it is shed during menstruation.
B. Myometrium
• The middle and thickest layer of the uterine wall.
• Made of smooth muscle (three layers of muscle fibers: longitudinal, circular, and spiral).
• Responsible for powerful contractions during labor/childbirth and also during menstruation (helps expel the endometrial lining).
• Dramatically enlarges during pregnancy to accommodate the growing fetus.
C. Perimetrium
• The outermost layer of the uterus itself.
• It is a thin serous (serosal) membrane.
• Actually a part of the visceral peritoneum that directly covers the uterus.
• Provides an external covering and some support; it is continuous with the broad ligament and other peritoneal folds.
D. Peritoneum
– Not a layer of the uterus itself, but the large serous membrane that lines the abdominal cavity (parietal peritoneum) and covers many abdominal organs (visceral peritoneum).
In the context of the uterus:
• The perimetrium (option C) is the visceral peritoneum covering the uterus.
• Anteriorly, the peritoneum reflects off the uterus to the bladder, forming the vesico-uterine pouch.
• Posteriorly, it forms the deeper recto-uterine pouch (pouch of Douglas).
• Secretes serous fluid to reduce friction between organs.
Quick summary of layers from inside to outside:
Endometrium → Myometrium → Perimetrium (visceral peritoneum)
(The broader peritoneal cavity is lined by the peritoneum in general – option D)
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Writer: Vandita Singh, Lucknow (GS India Nursing Group)