Histology: Male Prostate and Penis

Capsule

  • Fibroelastic connective tissue and smooth muscle.
  • Capsule is continuous with the central stroma.

Central stroma

  • Gives rise to septa that divide the prostate tissue into lobules.

Tuboloalveolar glands

  • Acini lined by pseudostratified epithelial lining.
    – The secretory cells, as their name implies, secrete a white serous fluid that contains substances, including PSA, that facilitate semen liquefaction. At a higher magnification, the prominent Golgi complex and abundant secretory vesicles are visible.
    – In acini, may see a corpora amylacea (aka, prostatic concretion), which is a lamellated mass of accumulated secretions. These deposits occur more frequently with age, and may become calcified.

Stroma

  • Surrounds glands, comprises collagen and smooth muscle fibers.

Zones of the prostate:

  • Fibromuscular zone = anterior.
  • Transitional zone surrounds the prostatic urethra, into which the glands drain.
  • Central zone surrounds the ejaculatory ducts.
  • Peripheral zone includes the rest of the prostate gland.
  • Zones have clinical relevance:
    – The transitional zone is most susceptible to benign prostatic hyperplasia, whereas the peripheral zone is most susceptible to inflammation and prostatic adenocarcinomas.
    – Elevated plasma prostate-specific antigen, which is produced by the secretory cells of the peripheral zone, is indicative of adenocarcinoma; surgery, radiation, and hormone therapy are used to treat).

Be aware of intertextual variation in prostate zoning, and that, because of its shape, sections from different levels and perspectives will show more or less of these zones.

Penis

Comprises three cylindrical bodies of erectile tissue:

  • The dorsal bodies are the corpus cavernosa; they are wrapped in a thick fibrous layer of tunica albuginea.
    – In histological sample of the corpus cavernosum, can see a helicine artery and a nearby venous sinus.
  • The ventral body is the corpus spongiosum; the penile urethra lies within it.
    – Houses the urethral glands of Littre, which secrete pre-ejaculatory mucus into the prostatic urethra.

Histology:

  • The erectile bodies comprise fibroelastic connective tissue interspersed with smooth muscle and neurovascular structures; indicate the deep arteries within the corpus cavernosa, and the dorsal artery and veins dorsally.
  • During an erection, parasympathetic stimulation dilates the helicine arteries and the venous sinuses become engorged, blocking venous drainage.
  • It is possible to “fracture” the penis: force exerted on an erect penis can rupture the tunica albuginea; surgery may be necessary for repair.

Uterus and Uterine Tube Histology

Perimetrium

  • Outer serosal covering

Myometrium

  • Comprises a thick layer of smooth muscle continuous with the vagina
  • Interweaving smooth muscle bundles contract during orgasm and to expel uterine contents during menstruation and parturition.
  • Branches of the uterine artery course through the myometrium and form straight arteries, which reach only the stratum basalis, and spiral arteries, which travel to the stratum functionalis.

Endometrium

  • The inner most layer; it faces the uterine cavity
  • Can be subdivided into the stratum basalis, which lies against the myometrium, and the stratum functionalis, which faces the uterine cavity (be aware that some authors further divide the stratum functionalis into the stratum compactum and spongiosum).
  • Tubular glands of the endometrium are surrounded by stroma, in which we can also see blood vessels.
  • The endometrial glands comprise columnar ciliated and secretory cells.
  • The stratum functionalis, but not the stratum basalis, cyclically proliferates and sheds over the course of a menstrual cycle.

UTERINE TUBE

Serosa

  • Outermost layer

Muscularis (aka, myosalpinx)

  • Smooth muscle
  • Muscularis comprises thin longitudinal and circular layers of smooth muscle that contract to propel the ova towards the uterus.

Mucosa (aka, endosalpinx)

  • Inner lining
  • Mucosal folds are lined with two types of columnar cells: ciliated and non-ciliated secretory (aka, peg cells). The ciliated cells propel the ova towards the uterus, while the secretory cells produce fluids that nourish the ova and assist in sperm capacitation.
  • The labyrinth-like folds ensure that the ova will be in close proximity to the epithelia.

Clinical Correlations:

  • Endometriosis occurs when endometrial tissues are displaced and implant elsewhere in the abdominopelvic cavity. Lesions can cause pain and damaging scars.
  • Salpingitis, inflammation of the uterine tube, is typically caused by bacterial infection; it can damage the uterine tube and cause infertility.

Ovarian Follicle Histology

Primordial Follicle

  • Comprises:
    • The primary oocyte, which is arrested in meiosis I
    • A single layer of flat granulosa cells; the granulosa cells and oocyte interact to guide follicular maturation
    • A basement membrane (aka, lamina) surrounds the follicle
    • In puberty, follicles are cyclically “recruited” for further development
  • Primordial follicles are found towards the outermost portion of the ovary

Primary follicle

  • Comprises:
    • The growing primary oocyte
    • Newly formed zona pellucida, which is thick a-cellular coat that covers the oocyte; It displays sperm receptors and facilitates the acrosome reaction necessary for fertilization; after fertilization, the zona pellucida prevents additional sperm from joining with the oocyte.
    • Single layer of granulosa cells transition from flat to cuboidal, which reflects their greater cellular activity.

Secondary follicle

  • Comprises
    • Primary oocyte; has achieved meiotic and developmental competence (it is capable of completing meiosis and preparing for implantation).
    • Zona pellucida, and,
    • Multiple layers of cuboid granulosa cell (typically 6-9 layers)
    • Theca cells, which arise from the ovarian interstitium, begin to accumulate around the basement membrane of the secondary follicle.

Tertiary follicle

  • Comprises
    • Secondary oocyte, which is the product of meiosis I (we’ve omitted the polar body)
    • Zona pellucida
    • Granulosa cells separated by the antrum
    • Cumulos oophorus is the collection of granulosa cells that support the secondary oocyte
    • Corona radiata is a subset of the cumulus oophorus that directly surround the zona pellucida.
    • Theca cells have diversified, and now form the theca interna and externa layers.
    • Of the late tertiary follicles, only one, the so-called “dominant follicle,” is ovulated.

Ruptured follicle

  • Transitions physiologically and morphologically to become the corpus luteum, which acts as a temporary endocrine gland.
  • Ovulated secondary oocyte takes the corona radiata with it; in most cases, it is swept into the uterine tube and transported to the uterus for menstruation or implantation.