Table of Contents
Definition / general | Terminology | Diagrams / tables | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Electron microscopy descriptionCite this page: Al-Hussain T. Anatomy & histology. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/testisanatomy.html. Accessed July 3rd, 2022.
Definition / general
- Birth to age 4 (static phase): seminiferous tubules filled with small cuboidal cells with no definite lumen present, Leydig cells usually not visible
- Age 4 - 10 (growth phase): tubules, tubular lumina and cells enlarge; tubules become tortuous
- Age 10 to puberty (maturation phase): tubular cells have mitoses; Leydig cells prominent; spermatocyte differentiation visible
- Adult (postpuberty): each testis weights 15 - 19g, measures 5 × 3 cm; takes 70 days for cells to mature from spermatogonium to primary spermatocyte to secondary spermatocyte to spermatid to spermatozoa; maturation is orderly along length of tubule but often not present in biopsy cross section
- Normal spermatogenesis:
- Not every tubule has complete spermatogenesis
- Number of late spermatids correlates best with sperm counts
- Some patients have normal sperm counts but low motility or duct obstruction
- Testes is paired organ suspended in scrotum by spermatic cord
- Each testis is attached to an epididymis, which connects rete testis to vas deferens
- Testis is composed of convoluted seminiferous tubules in a stroma with Leydig cells
- Three layers: outer serosa (tunica vaginalis, extension of peritoneal cavity) with mesothelial cells; tunica albuginea (tough fibrous septa that extends into testis and separates it into 250 lobules of 1 - 4 seminiferous tubules), inner tunica vasculosa
- Seminiferous tubules converge into rete testis at hilum, anastomose into efferent tubules that penetrate tunica albuginea to form head of epididymis
Terminology
- Efferent ducts: see micro images below
- Epididymis:
- Connects efferent ductules to vas deferens
- Has head, body and tail
- Composed of columnar cells (tall, ciliated with PAS+ nuclear inclusions), clear cells and basal contractile cells (actin positive)
- May have "monster" cells similar to seminal vesicle (no significance, Am J Surg Pathol 1981;5:483)
- Tubules have thick muscular coat
- References: Am J Surg Pathol 2003;27:469
- Nonpathologic morphologic variations:
- Intranuclear eosinophilic inclusions: 72%, usually older patients
- Lipofuscin pigment: 33% usually in efferent ducts and associated with obstructive changes
- Cribriform hyperplasia: 42% usually NOT in normal testis
- Paneth cell-like metaplasia: 8% with hyalin-like globules that are positive for PAS with and without diastase digestion, associated with obstructive changes
- Nuclear atypia: 14% similar to that in seminal vesicles, associated with older age
- Note: rarely present within hernia sacs (Am J Surg Pathol 1999;23:880)
- References: Am J Surg Pathol 1998;22:990
- Interstitium: contains Leydig cells and stromal elements (collagen and myoid cells that surround seminiferous tubules)
- Leydig cells:
- Single (20 microns) or in clusters between seminiferous tubules, produce testosterone in response to luteinizing hormone (LH)
- Often associated with nerve fibers and blood vessels
- Have abundant pink cytoplasm with lipid, lipochrome pigment, Reinke crystalloids (hexagonal prisms by EM), round nuclei with distinct nucleoli
- Fewer Leydig cells in elderly
- Mediastinum: posterior testicular capsule with vasculature, nerves, mediastinum of rete testis (where tubules converge)
- Rete testis:
- At testicular hilum
- Complex tubular architecture may resemble teratoma
- Connects testicular tubules to 12 - 15 ciliated efferent ducts, which merge into a single duct, the epididymis at its head
- Rete lined by flattened to columnar epithelium with numerous microvilli
- Efferent duct lumina are narrower than epididymis, lined by ciliated columnar cells with microvilli
- Seminiferous tubules:
- 150 - 250 microns in diameter, the average total length in each testes is 540 m (range 299 - 981 m)
- Lined by multilayered epithelium with most mature cells towards lumina
- Have basal lamina, outer myoid cells (positive for desmin, muscle specific actin, vimentin) and collagen
- Contain Sertoli cells, spermatogonia (types A and B), primary spermatocytes, secondary spermatocytes, spermatids and spermatozoa
- All except spermatozoa are held together by a narrow cytoplasmic bridge
- Immature tubules are positive for alpha inhibin
- Sertoli cells:
- Columnar, on basement membrane, surround germ cell elements with cytoplasmic extensions, form blood - testis barrier
- 7% of tubular cells
- May contain Charcot-Bottcher crystalloids (bundles of microfilaments)
- Have irregular, highly folded nuclei with prominent nucleoli
- Produce anti-Müllerian hormone, which causes regression of Müllerian duct structures in utero
- After birth, secrete androgen binding protein and are responsive to FSH
- Also produce inhibin
- Vas deferens:
- Also called ductus deferens
- 30 - 40 cm long tubular structure from tail of epididymis to prostatic urethra at level of verumontanum; distal vas deferens joins seminal vesicle to form ejaculatory duct
- Rarely present within hernia sacs (Am J Surg Pathol 1999;23:880)
- Should see complete transection in vasectomy specimens
- References: Am J Surg Pathol 2003;27:469
Vestigial remnants:
- Appendix epididymis: remnant of mesonephric duct
- Appendix testis (hydatid of Morgagni):
- Remnant of Müllerian duct; attached to tunica albuginea at upper testicular pole; present in 90% of males
- May undergo hemorrhagic infarction from twisting on its pedicle
- Gross: round / oval, 1 - 10 mm, pedunculated
- Micro: columnar epithelium with vascular fibrous core with smooth muscle cells; may have glandular-like structures due to surface invaginations
- Paradidymis (organ of Giraldes): remnant of mesonephric tubules
- Vas aberrans (organ of Haller): remnant of mesonephric tubules
Diagrams / tables
Microscopic (histologic) description
- Spermatic cord:
- Ciliated, pseudostratified epithelium with prominent nuclear inclusions resting on basal cell layer
- Markedly thickened muscle coat of 3 layers (inner longitudinal, outer longitudinal, middle circular layer)
- May contain psammoma bodies
Microscopic (histologic) images
Positive stains
- Epididymis and spermatic cord: CD10
Electron microscopy description
- Spermatogenesis: EM may show round headed sperm or immotile cilia syndrome