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histology of endometrial

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endometrium histology microscopy glands stroma

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proliferative endometrium histology tubular glands

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secretory endometrium subnuclear vacuoles saw-tooth glands

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Here is a comprehensive overview of endometrial histology, drawn from Junqueira's Basic Histology (17e) and Histology: A Text and Atlas (Ross & Pawlina).

Histology of the Endometrium

General Structure

The endometrium is the inner mucosal lining of the uterus. It consists of:
  1. Surface epithelium — simple columnar epithelium with both ciliated and secretory cells
  2. Lamina propria (stroma) — cellular connective tissue rich in fibroblasts, ground substance, and non-bundled type III collagen
  3. Uterine glands — tubular glands lined by columnar secretory epithelium that penetrate the full thickness of the endometrium

Two Concentric Layers

LayerLocationCharacteristics
Stratum Basale (Basal layer)Adjacent to myometriumHighly cellular stroma; contains deep basal ends of glands and lower portions of spiral arteries; not shed during menstruation
Stratum Functionale (Functional layer)SuperficialSpongier stroma, rich in ground substance; contains most of the gland length and surface epithelium; shed cyclically during menses
Arterial supply diagram showing functional and basal layers, spiral and straight arteries, uterine glands, and myometrium

Blood Supply (Histologically Important)

Arcuate arteries in the myometrium give off radial arteries that enter the endometrium and divide into:
  • Straight arteries — supply only the stratum basale
  • Spiral arteries — coiled, progesterone-sensitive; supply the stratum functionale; their vasoconstriction triggers menstrual shedding

Cyclic Histological Changes

The endometrium undergoes three cyclic phases driven by ovarian hormones:

1. Proliferative Phase (Days 5–14)

Driven by estrogen from growing follicles
  • Endometrial thickness: ~3 mm
  • Glands: straight to slightly wavy, narrow lumina, pseudostratified columnar epithelium with mitoses
  • Stroma: compact, cellular with active mitoses
  • Spiral arteries: only mildly coiled, do not reach upper third of endometrium
  • Glycogen accumulates in basal cytoplasm of gland cells (appears empty on H&E after fixation)
Normal proliferative phase endometrium — H&E showing round tubular glands in a cellular stroma

2. Secretory Phase (Days 15–28)

Driven by progesterone from corpus luteum
  • Endometrial thickness: up to 5–6 mm
  • Glands: corkscrew/saw-tooth shaped with sacculated, dilated lumina filled with glycogen-rich mucoid secretion
  • Subnuclear vacuoles appear early (day 17–18) — hallmark of early secretory phase
  • Stroma: edematous; later undergoes predecidual change (enlarged pale stromal cells rich in glycogen)
  • Spiral arteries: markedly elongated, tightly coiled, extend nearly to surface
  • Mitoses are rare
Secretory phase endometrium — H&E showing dilated, irregular serrated glands and edematous stroma

3. Menstrual Phase (Days 1–4)

Triggered by decline in estrogen and progesterone
  • Spiral artery vasoconstriction → ischemia of stratum functionale
  • Glands stop secreting; stroma loses edema
  • Rupture of blood vessels → extravasation, necrosis, and sloughing of the functional layer
  • Only the stratum basale persists
  • Average blood loss: 35–50 mL over ~5 days

Comparative Histology at a Glance

FeatureProliferativeSecretoryMenstrual
Thickness~3 mm5–6 mmThinning
Gland shapeStraight/wavyCorkscrew/sacculatedDegenerating
Gland lumenNarrowWide, filled with secretionCollapsing
EpitheliumTall, pseudostratified, mitosesSecretory, vacuolated, no mitosesNecrotic
StromaCompact, mitoticEdematous → predecidualNecrotic/hemorrhagic
Spiral arteriesMildly coiledTightly coiledConstricted → rupture
Hormone driverEstrogenProgesteroneWithdrawal of both
H&E photomicrographs of all three phases — proliferative (a), secretory (b), and menstrual (c)

Clinical Correlations

  • Anovulatory cycles: No corpus luteum → no progesterone → endometrium stays in prolonged proliferative phase → can lead to endometrial hyperplasia
  • Endometrial dating: Histological appearance of the glands and stroma can be used to assess cycle day and diagnose luteal phase defects
  • Endometriosis: Viable endometrial cells reflux through the tubes and implant on pelvic structures, responding to cyclic hormonal changes
  • Decidualization: If implantation occurs, stromal cells transform into large, pale decidual cells rich in glycogen under sustained progesterone stimulation
Sources: Junqueira's Basic Histology, 17e, p. 1133–1135 | Histology: A Text and Atlas (Ross & Pawlina), pp. 2246–2249

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squamous cell carcinoma histology keratin pearls H&E

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squamous cell carcinoma well differentiated moderately poorly differentiated grading comparison

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