Menstrual Cycle - Histology

From Embryology


This page presents images from vaginal smears and uterine endometrium dilatation and curettage[1] samples during different phases of the human menstrual cycle.

Menstrual Cycle Links: Introduction | menstrual histology | ovary | corpus luteum | oocyte | uterus | Uterine Gland | estrous cycle | pregnancy test
Historic Embryology - Menstrual 
1839 Corpus Luteum Structure | 1851 Corpus Luteum | 1933 Pap Smear | 1937 Corpus Luteum Hormone | 1942 Human Reproduction Hormones | 1951 Corpus Luteum | 1969 Ultrastructure of Development and Regression | 1969 Ultrastructure during Pregnancy
Histology Links: stains | fixatives | artifacts | menstrual histology | placenta histology | heart histology | liver histology | Pancreas | Gall Bladder | Colon | Renal | Respiratory Histology | Bone | Category:Histology | UNSW Histology
  Historic Histology Textbooks: 1941 Histology] | 1944 Oral Histology
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History of the Pap Smear

The text below is from the ABC - Great Moments In Science

"Luckily, we have the famous Pap Smear - an excellent way to find cancer of the cervix before it digs in locally and/or spreads throughout the body. The Pap Smear is named after a certain Dr. Papanicolaou - who did a Pap Smear on his wife virtually every day for 20 years.

George Nikolas Papanicolaou was born in 1883 in Kymi, a small town overlooking the Aegean Sea on the Island of Euboea in Greece. His father, Nikolas Papanicolaou was both the Major of Kymi and a medical doctor. His older brother, Naso, had studied law, so his father convinced George to continue in the family medical tradition. So George studied medicine, and did well, graduating with a degree in honours in 1904............"

Links: ABC - Great Moments In Science

Dilation and Curettage

Medical procedure where uterine endometrium is collected by Dilation and Curettage (D&C or DnC). This medical procedure is used to diagnose or treat uterine abnormalities or in association with a miscarriage.

Links: Medline Plus D&C | PMID 15725872


Phase Days (range) Smear Smear Description Uterine Endometrium (D&C)
Menstrual 1 - 4 Click on image to see full size. Both stratum corneum (red) and stratum spinosum (blue) epithelial cells will mostly blood.

Leukocytes and bacteria may also be present.

Human- menstrual uterine endometrium.jpg
Early Proliferative 5 - 9 Smear- early proliferative.jpg Mainly large and small basophilic (blue) stratum spinosum cells.  
Mid Proliferative 9 - 13 Smear- mid-proliferative.jpg Stratum spinosum (blue) increase in size.

Dark precipate outside cells are bacteria.

Human- mid-proliferative uterine endometrium.jpg
Late Proliferative, Ovulatory 13-14 Smear- late-proliferative.jpg mainly stratum corneum (red) which are large and flat.

Appear due to high estrogen levels.

Human- late proliferative uterine endometrium.jpg
Secretory 15 - 22 Smear- secretory.jpg stratum spinosum cells (blue) which are folded or with curled edges.

Appear immediately after ovulation due to increase in progesterone.

Leukocytes (small black cells) becoming more numerous.

Human- secretory uterine endometrium.jpg
Late Secretory, (Ischemic) Premenstrual 23 - 28 Smear- late secretory.jpg stratum spinosum cells (blue) mainly with a few stratum corneum cells (red).

Clustering of cells occurs at this stage.

Both leukocytes and bacteria are prevelant.

Human- late secretory uterine endometrium.jpg

Human vaginal smear histology images in sequence: early proliferative | mid-proliferative | late proliferative | secretory | late secretory

Human Uterus (D and C histology images) in sequence: menstrual | mid-proliferative | late proliferative | secretory | late secretory

See also Uterus Development


Bacterial Vaginosis

  • The normal vaginal flora (lactobacillus morphotypes) is replaced by a mixed microbial flora consisting of Gardnerella vaginalis, Mycoplasma hominis and anaerobes.
    • Originally described by Gardner and Dukes (1955).[2]
  • clinical features - malodorous, thin homogeneous vaginal discharge with elevated vaginal pH above 4.5.
Smear Image Links: L. crispatus | L. crispatus | non-L. crispatus with thin lactobacilli | non-L. crispatus with thin lactobacilli | mixture non-L. crispatus with L. crispatus | mixture non-L. crispatus with L. crispatus | irregular-shaped Gram positive rod | irregular-shaped Gram positive rod | mixture Lactobacillus and bacterial vaginosis-associated | mixture Lactobacillus and bacterial vaginosis-associated | bacterial vaginosis | bacterial vaginosis
Links: Menstrual Cycle - Histology | Histology - Gram Stain | Bacterial Vaginosis | CDC (USA) Fact Sheet - Bacterial Vaginosis


  1. <pubmed>19594996</pubmed>
  2. <pubmed>14361525</pubmed>

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Cite this page: Hill, M.A. (2021, November 28) Embryology Menstrual Cycle - Histology. Retrieved from

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© Dr Mark Hill 2021, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G