Talk:Paper - The development of the human prostate gland with reference to the development of other structures at the neck of the urinary bladder
1. The mucosa is always free from folds over the fetal trigonum vesicae. The musculature of the bladder wall, trigonum, and sphincter begins to develop at the thirteenth week and by the sixteenth week is very pronounced.
2. The subtrigonal glands begin to develop at the twentieth week. They are found at all ages after that, are few in number and insignificant in appearance, their only importance being that they occupy a strategic position where a small pedunculated enlargement might cause great obstruction to urinary outflow.
3. The subcervical glands of Albarran are constant after the age of sixteen weeks. They are similar in structure but are more numerous and larger than the sub trigonal tubules. Their importance also lies in their position. They originate from the floor of the urethra within and below the internal sphincter and grow back under the mucosa so that they lie directly within it. Hence a slight increase in their size would cause very grave obstruction to urinary outflow.
4. The prostate gland originates from five independent groups of tubules which begin to develop at about the twelfth week as follows :
(a) The middle lobe is made up of nine or ten large branching tubules originating on the floor of the urethra between the bladder and the openings of the ejaculatory ducts. There may be an absence of the middle lobe in which case there may be an ingrowth of tubules from the lateral lobes to form a commissure beneath the urethra. Embryologically the middle lobe is an independent structure. Practically it makes no difference because it is not separated by a capsule from the lateral lobes. The middle lobe is rarely absent, being found definitely present in ninety-seven specimens examined, possibly lacking in five others and definitely absent in one.
(b) The right and left lateral lobe tubules originate in the prosstatic furrows and from the lateral walls of the urethra. They are composed of from twenty-seven to forty-six tubules which grow back to form the main part of the base of the prostate. They are well separated from each other by the anterior lobe and commissure, the urethra, the middle lobe and the ejaculatory ducts. Posteriorly they are separated from the posterior lobe by a fibrous capsule.
(c) The posterior lobe is an independent structure being made up of tubules which originate from the floor of the prostatic urethra below the openings of the ejaculatory ducts. They grow back behind the latter structures and are in no sense a glandular commissure as they are definitely separated from the other parts of the gland. The posterior lobe is the part of the prostate palpated per rectum and is an important consideration in the performance of perineal prostatectomy. Hypertrophy rarely or never occurs in it and primary carcinoma of the prostate rarely or never begins anywhere else (Boyd and Geraghty).
(d) The anterior lobe is fairly large until the sixteenth week after which time it becomes greatly decreased in size and in the number of its tubules. It was found in all of the microscopic specimens studied but shrinks into insignificance at the twentysecond week. There is evidence in the occasional finding of enlarged anterior lobes at autopsy that this structure may persist throughout life. The number of openings of prostatic tubules into the urethra is usually said to be between twenty and thirty. My studies have convinced me that this number is too low as in the specimens here recorded the number of tubules opening into the urethra varies from fifty-three to seventy-four, the average being sixtythree.
5. The vasa deferentia in early fetal life are comparatively speaking very large, being greater in size than the urethra at the thirteenth week. Their lumina broaden out behind the vesical sphincter at this time showing the earliest appearance of the ampullae. They become relatively decreased in size after the sixteenth week.
6. The seminal vesicles begin to develop as lateral evaginations from the vasa deferentia at the thirteenth week. They grow backward and laterally becoming more or less tortuous and send off as many as four short tortuous branches. In the later stages they communicate through a very narrow duct with the vasa deferentia just within the base of the prostate gland.
7. In the younger fetuses the ejaculatory ducts pass obliquely through the posterior wall of the prostatic urethra forming with their envelopes the verum montanum. In the older specimens their course through the prostate is not so regular. At the base they progress on a gradual slant until the middle of the gland is reached, where they rise quite sharply until they lie in the top of the verum montanum, after which their course lies parallel to the axis of the urethra for some distance. They open into the urethra on the sides of the verum montanum, their mouths being composed of a collapsible fold of tissue so that pressure within the prostatic urethra very effectively closes them.
8. The fused Mullerian ducts may persist intact until the thirteenth week, after which time the lower end (utriculus prostaticus) which has become quite large in size and surrounded by a rather dense layer of stroma cells, contracts until after the twenty-second week when it is found only in the tip of the verum montanum and is relatively very small in size. It usually opens in the midline just below the ejaculatory duct openings and rarely if ever is there an ejaculatory duct or a prostatic tubule opening into it.
- Kuznitzky found a persistent ventral lobe in one out of every fifteen prostates.