Urological Research @ by Springer-Verlag 1977

UroloFica! R e s e a r c h .5, i@3-167 (1977)

ORIGINALS The Zonal Anatomy of the Prostate in Man and in the Rhesus Monkey (Macaca Mulatta) N.J. Blacklock and K. Bouskill Royal Naval Hospital, Haslar, U,K. Received: April 18, 1977

S u m m a r y : Study of whole sections of h u m a n prostate has confirmed m o r p h o l o g y of the external glands (2) in the t e r m s of a central zone caudal to this. A study of the n o n - h u m a n primate, M a c a c a Mulatta, prostatic entities in this animal w h o s e anatomical relationships and h o m o l o g y with the central and peripheral zones of the human. K e y words: Prostate - M o r p h o l o g y - H u m a n

THE

HUMAN

- Monkey

PROSTATE

M c N e a l (4), in describing the anatomical subdivisions of the p a r e n c h y m a of the functional prostate, or external glands (2), designated these as "zones" and in so doing helped to distinguish n o r m a l a n a t o m y f r o m areas of focal pathology within the gland. T h e s e zones are identified both by morphological differences and by differential susceptibility to inflammation, degeneration and neoplasia. H e defined two subdivisions of the prostate which are c o m p a r a b l e in m a n y respects with those described by Hutch (3). T h e central zone is a w e d g e of glandular tissue of variable size with its apex at the v e r u m o n t a n u m and its base superiorly behind the bladder neck. In contrast to other descriptions, however, this zone surrounds the c o m m o n ejaculatory ducts and distal extremities of the vas deferens and ducts of the seminal vesicles (I). The acini of the central zone constitute the base of the prostate whilst those of the peripheral zone caudally f o r m the r e m a i n d e r of the p a r e n c h y m a and partially enclose the apex or lower part of the central zone. T h e central zone c o m p r i s e s about one third of the external gland m a s s . THE

PROSTATE

OF

THE

NON-HUMAN

PRIMATE

Price (6) described the m o n k e y prostate as lying entirely on the dorsal aspect of the urethra and neck of the bladder (Fig. i) and having two

M c N e a l ' s (4) concept of a dual cranially and a peripheral zone has s h o w n cranial and caudal histological characteristics suggest

- Central zone - Peripheral zone.

discrete lobes. The cranial entity had a furr o w e d surface which closely r e s e m b l e d that of the seminal vesicles in external appearance. The caudal lobe w a s s m o o t h on its external surface and again lay on the dorso-lateral aspect of the urethra (Figs. 2, 3, and 4). Price noted that the two lobes differed histologically. V a n W a g e n e n (8) found the secretion f r o m the cranial lobe to coagulate the secretion of the seminal vesicles and in this respect it appeared to have similar properties to the secretion of the coagulating gland of the rodent. Schoonees et al. (7) in describing a similar general a n a t o m y in±he baboon, found differential zinc concentration between the two parts of the gland. T h e r e w a s a significantly greater concentration of zinc in the caudal lobe and, furthermore, both castration and exogenous testosterone appeared to influence the zinc content of the caudal entity m o r e than that of the cranial. M o r e recent w o r k has s h o w n very high acid phosphatase content of the caudal lobe of the baboon prostate and greater susceptibility of this lobe co antiprostatic drugs (5).

MATERIAL

AND

METHODS

T h e bladder, prostate and m e m b r a n o u s urethra w e r e r e m o v e d f r o m h u m a n cadavers at postm o r t e m in various age ranges. The bladder, seminal vesicles, prostatic c o m p l e x and upper urethra w e r e r e m o v e d f r o m 13 rhesus m o n k e y s

164

Urol.

Res.,

Vol.

5, No.

4 (1977)

(Macaca mulatta), both mature and immature, under terminal anaesthesia. S p e c i m e n s w e r e sectioned in the fresh condition either in the coronal or sagittal plane and fixed in formolsaline. W h o l e histological sections w e r e m a d e and stained with a variety of tissue stains.

RESULTS

The H u m a n

. ,~,.

Fig. i. Cross prostate

. :L'

i ~II:

section of rhesus

:

monkey

Prostate

There w a s confirmation of McNeal~s description both in sagittal (Fig. 5) and coronal (Fig. 6) sections of the prostate. A cranial zone corresponding with McNeal's central zone w a s defined occupying the base of the gland behind and below the bladder neck and enclosing the c o m m o n ejaculatory ducts, terminal vas deferens, ducts of the seminal vesicles and the utriculus masculinus. The demarcation between this zone and the peripheral zone caudally w a s s o m e t i m e s well-defined by a condensation of fibromuscular s t r o m a (Fig. 6). Before puberty, the central and peripheral zone aeini are morphologically indistinguishable and consist of simple straight tubules, widely separated by a coarse fibromuscular s t r o m a and lined by a stratified cuboidal epithelium. Following puberty, the acini in the two zones develop distinct histological differences.

2 ¸¸

3

.,%

2

4 . . .;. .

Cm

Fig. 2. Anterior vlew of bladder, urethra, seminal vesicles and prostate of rhesus m o n k e y Fig. 3. Lateral view of bladder, urethra, seminal vesicles and prostate of rhesus m o n k e y Fig. 4. Posterior aspect of bladder, urethra,

seminal vesicles and prostate of rhesus m o n k e y

s

N.J.

B l a c k l o c k and K. B o u s k i l l : Z o n a l A n a t o m y of the P r o s t a t e

F i g . 5. H u m a n p r o s t a t e , s a g i t t a l Van G i e s o n F i g . 6. H u m a n p r o s t a t e , c o r o n a l H&E F i g . 7. R h e s u s m o n k e y p r o s t a t e , s e c t i o n , Van G i e s o n F i g . 8. R h e s u s m o n k e y p r o s t a t e , section. H & E

165

section. section. sagittat coronal

The acini in the central zone b e c o m e large and angular with a complex, m i x e d cribriform and papillary pattern similar to the pattern of the seminal vesicles. Several acini are grouped together and separated f r o m adjacent groups by a coarse, fibromuscular s t r o m a (Fig. 9). T h e acini of the peripheral zone are m u c h

166

Fig. H&E

Urol, Res.,

9. Human

prostate,

acini of central

zone.

smaller with a more regular, simple, tubular appearance and less papillary infolding of the epithelium. They are not grouped together and each acinus is separated from its neighbour by a delicate, fine fibromuscular stroma (Fig. i0). The epithelium lining both types of acinus is too variable to allow distinction between the two zones and varies from a single-layered cuboidal epithelium to a stratified, tall columnar epithelium in either zone. In serial coronal sections forward from the posterior surface of the gland to the midurethral plane there was the appearance of a further subdivision of the central zone into right and left halves by its enclosure of the common ejaculatory ducts and utriculus masculinus. This study in the human therefore confirms McNeal's description of the morphology of the parenchyma of the external glands or functional prostate in the terms of central and peripheral zones. The Prostate of the R h e s u s M o n k e y Mulatta)

(iViaca~a

In the dissection of material r e m o v e d f r o m the rhesus m o n k e y s , there w a s confirmation that a capsule invested both entities of the prostate

Fig. i0. H u m a n zone. H & E

Vol. 5, No. 4 (1977)

prost.ale, acini of peripheral

and the urethra and a loose capsule bound the cranial prostate to the seminal vesicles, The surface of the cranial lobe w a s deeply furrowed and in this respect r e s e m b l e d the seminal vesicles. The caudal lobe w a s m o r e closely applied to the urethra than the cranial lobe and had a s m o o t h surface (Figs. 2, 3 and 4). The cranial lobe could be easily separated f r o m the seminal vesicles above ~(Figs. 3 and 4). It w a s found to surround the terminal vas deferens and the duct of the s~eminal vesicles of each side as these passed d o w n w a r d s and forw a r d s to the urethra. It .could be separated f r o m these structures with ease and also f r o m the urethra in fronl. T h e r e w a s anatomical separation between the ~cranial and caudal lobes peripherally but antero--medially the tissues of the two lobes m e r g e d w h e r e the ducts f r o m the cranial lobe in c o m p a n y w i ~ t~he c o m m o n ejac.ulatory ducts penetrated the flat upper surface of t~he caud~al lobe before passing thraugh the wall of the mrefkra at t.he level of the ve r,um.ontanum. Large histological sections both in the sagittal and c.oronal planes confirm these gross findings (Figs. 7 and 8). The histological appe~armnce of the ,crania~l and caudal lobes is qai.te different. T h e acini in the

N.J.

Blacklock

and K. Bouskill:

Zonal

Anatomy

cranial lobe consist of large, irregular branching tubules with a prominent fibromuscular stroma which widely separates individual acini. The acini are lined by tall c o l u m n a r stratified epithelium with strongly eosinophilic cytoplasm and dense basal nuclei with their long axis at right angles to the b a s e m e n t m e m b r a n e . The acini in the caudal lobe are m u c h smaller and consist of simple tubules with a regular appearance overall. The fibromuscular s t r o m a is m o r e delicate and individual acini are in close proximity to each other. The acini are lined by a single layer of cuboidal or low c o l u m n a r epithelium with pale eosinophilic cytoplasm and vesicular basal nuclei with their long axis parallel with the b a s e m e n t m e m b r a n e . The seminal vesicle is morphologically identical to that in the h u m a n and has a complicated papillary pattern.

of the Prostate

167

Medicine, Farnborough, U.K. for animal facilities and to Mr. J a m e s C o o k s o n for expert technical assistance.

REFERENCES

This study of the parenchyma of the human prostate confirms McNeal's concept of a dual morphology of the external glands represented by the central and peripheral zones which he described. There is a direct comparison with the prostatic complex of the monkey, the cranial lobe of the monkey having features in common with the central zone of man, the monkey caudal lobe reseml~ling the human peripheral zone. If homology can be further established, the monkey prostate may prove a convenient model for further studies and appears particularly suitable for the study of prostatic function.

i. Blacklock, N.: The m o r p h o l o g y of the p a r e n c h y m a of the prostate. Urological R e s e a r c h 5, 155 (1977) 2. Franks, L . M . : Benign nodular hyperplasia of the prostate; a review. Annals of the Royal College of Surgeons of England 14, 92 (1954) 3. Hutch, J. A. : Anatomy and Physiology of the Bladder, Trigone and Urethra. London: Butterworth 1972 4. McNeal, J.E. : Regional morphology and pathology of the prostate. American Journal of Clinical Pathology 49, 347 (1968) 5. Muntzing, J., Myhrberg, H., Saroff, J., Sandberg, A.A. , Murphy, G.P. : Histochemical and ultrastructural study of prostatic tissue from baboons treated with antiprostatic drugs. Investigative Urology 14, 162 (1976) 6. Price, D.: Comparative aspects of development and structure in the prostate. National C a n c e r Institute M o n o g r a p h s 12, i (1963) 7. Schoonees, R., de Klerk, J.N., Murphy, G. P. : Correlation of prostatic blood flow with 65 zinc activity in intact, castrated and testosterone-treated baboons. Investigative Urology 6, 476 (1969) 8. V a n Wagenen, G. : The coagulating function of the cranial lobe of the prostate gland in the monkey. Anatomical R e c o r d 66, 411 (1936)

Acknowledgements. This work has been supported by a grant from Schering Chemicals Limited, United Kingdom. The authors are grateful to the Medical Officer in Charge, Institute of Aviation

N.J. Blacklock, M.D. Royal Naval Hospital Haslar, Gosport Hants. P012 2AA United Kingdom

CONCLUSIONS