Menstrual Cycle - Histology

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Endometrium during menstrual cycle secretory phase.

During the menstrual cycle, the uterus undergoes a series of histologically recognisable cyclic changes under the influence of changing circulating hormonal levels.

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

Beneath these clinical images are a number of more detailed uterus histology images.

Menstrual Cycle Links: Introduction | Menstrual Cycle - Histology | Ovary | Oocyte | Uterus | Uterine Gland | Estrous Cycle | Pregnancy Test

Histology Links: Stains | Fixatives | Menstrual Cycle | Placenta | Heart | Liver | Pancreas | Gall Bladder | Colon | Renal | Respiratory Histology | Bone | Category:Histology | UNSW Histology
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History of the Pap Smear

(Papanicolaou smear, pap test, cervical 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

Papanicolaou (1933)[1] Hand coloured photomicrographs from the publication showing the human reproductive cycle as revealed by vaginal smears.

Papanicolaou Stain

This histology technique was originally described in a publication by George Nikolas Papanicolaou in 1942.[2] There are 5 different stains used in the technique and it has been used for many different human bodily fluids (CSF, semen, aspirations). The original protocol has also been modified several ways (Bismarck brown Y deleted).

Links: Papanicolaou Stain | Histology Stains | Histology

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

Histology Images

Uterus Histology Links: Labeled - proliferative phase | Labeled - gland proliferative phase | Labeled - secretory phase | Unlabeled - secretory phase | Unlabeled - late secretory phase | Labeled - gland secretory phase | Menstrual Cycle | Uterine Gland | 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).[3]
  • clinical features - malodorous, thin homogeneous vaginal discharge with elevated vaginal pH above 4.5.
  • Nugent's criteria[4] - microbiological diagnosis of bacterial vaginosis, by counting bacterial cell types on Gram stained slides of vaginal smears.

Proposed Gram stain based categorisation[5]

  1. grade I - when only Lactobacillus cell types (large Gram positive rods) were present.
  2. grade II (intermediate) when both Lactobacillus and Gardnerella or Bacteroides-Prevotella cell types were present.
  3. grade III (bacterial vaginosis) when Lactobacillus cell types were absent and only Gardnerella, Bacteroides-Prevotella or Mobiluncus cell types were present.
  4. grade IV when Gram positive cocci were predominantly present.

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. Papanicolaou GN. The Sexual Cycle in the Human Female as revealed by Vaginal Smears. Am J Anat. 1933;52: 519–637.
  2. G N Papanicolaou A NEW PROCEDURE FOR STAINING VAGINAL SMEARS. Science: 1942, 95(2469);438-9 PubMed 17842594 | Science
  3. H L GARDNER, C D DUKES Haemophilus vaginalis vaginitis: a newly defined specific infection previously classified non-specific vaginitis. Am. J. Obstet. Gynecol.: 1955, 69(5);962-76 PubMed 14361525
  4. R P Nugent, M A Krohn, S L Hillier Reliability of diagnosing bacterial vaginosis is improved by a standardized method of gram stain interpretation. J. Clin. Microbiol.: 1991, 29(2);297-301 PubMed 1706728 | PMC269757
  5. Rita Verhelst, Hans Verstraelen, Geert Claeys, Gerda Verschraegen, Leen Van Simaey, Catharine De Ganck, Ellen De Backer, Marleen Temmerman, Mario Vaneechoutte Comparison between Gram stain and culture for the characterization of vaginal microflora: definition of a distinct grade that resembles grade I microflora and revised categorization of grade I microflora. BMC Microbiol.: 2005, 5;61 PubMed 16225680 | PMC1266370 | BMC Microbiol.

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Cite this page: Hill, M.A. (2016) Embryology Menstrual Cycle - Histology. Retrieved May 29, 2016, from

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© Dr Mark Hill 2016, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G