Biology · Human Reproduction · NEET
From outside to inside the three layers are: (1) Perimetrium - the thin outer membranous layer, (2) Myometrium - the thick middle layer of smooth muscle, and (3) Endometrium - the inner glandular layer that lines the uterine cavity. NCERT states this exact order, so remember outside-to-inside as Peri, Myo, Endo.
The myometrium is the middle thick layer of smooth muscle. It contracts strongly during delivery of the baby to push the baby out. The endometrium is the inner glandular lining of the uterine cavity. It undergoes cyclical changes during the menstrual cycle and is the layer where the embryo implants. In short: myometrium = muscle for delivery, endometrium = lining for implantation and menstruation.
The myometrium contracts during delivery. It is the middle thick layer of smooth muscle, and NCERT says the myometrium exhibits strong contraction during delivery of the baby. Oxytocin acts on this muscle layer during parturition. Students often wrongly pick endometrium - but endometrium is only the lining, it does not contract to push the baby out.
The endometrium is shed during menstruation. The endometrium undergoes cyclical changes during the menstrual cycle - it thickens after the menstrual phase and, if fertilisation does not happen, the corpus luteum degenerates, progesterone falls, and the endometrium disintegrates, causing bleeding. The myometrium and perimetrium are NOT shed.
The perimetrium is the external, thin, membranous layer of the uterine wall - it is the outermost covering. NCERT describes it as 'the external thin membranous perimetrium.' It does not have muscle or glands like the other two layers; it simply covers and protects the uterus from outside.
The endometrium is the site of implantation. After fertilisation, the blastocyst attaches to the endometrium and gets embedded in it - this is implantation, which leads to pregnancy. Progesterone from the corpus luteum maintains the endometrium so that implantation can happen. This is why NCERT says the endometrium is necessary for implantation.
Assertion A: Endometrium is necessary for implantation of blastocyst. Reason R: In the absence of fertilization, the corpus luteum degenerates that causes disintegration of endometrium. In the light of the above statements, choose the correct answer.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The perimetrium is the outermost layer. It is a thin, membranous covering on the external surface of the uterine wall.
The endometrium is the glandular layer. It lines the uterine cavity and its glands change through the menstrual cycle to prepare for implantation.
No. The endometrium undergoes the cyclical changes during the menstrual cycle. The myometrium's main special role is strong contraction during delivery of the baby, not monthly cycling.
Use 'PME - outside to inside': Perimetrium (Protect), Myometrium (Muscle), Endometrium (Egg-bed for implantation). Peri = around/outer, Myo = muscle in the middle, Endo = inner lining.
Oxytocin acts on the myometrium, the smooth-muscle layer, causing strong uterine contractions that expel the baby during parturition.
