The vagina is an elastic fibromuscular canal extending upwards and backwards from the vulva at an angle of 60-70 degrees to the horizontal, although it is not straight as is generally supposed angled backwards. Vagina. That this is so is demonstrated not only by topography but by the taking of casts of the vagina in the living woman. The vagina pierces the triangular ligament and the pelvic diaphragm, the level of these structures being approximately 1 and 2.5cm, respectively, from its lower end. The vagina has a blind upper end except so far that the cervix with its external os projects through its upper anterior wall. Vagina
The vault of the vagina is divided into four areas according to their relations to the cervix: the posterior fornix which is capacious, the anterior fornix which is shallow, and two lateral fornices. Because the cervix is inserted below the vault, the posterior vaginal wall is approximately 10 cm, whereas the anterior wall is approximately 8 cm, in length.
The Introitus Functional
The introitus is functionally closed by the labia which are in contact with each other. Moreover, the lumen of the vagina is ordinarily obliterated by the anterior and posterior walls lying in apposition. In its lower part, it appears H-shaped on a cross-section with lateral recesses anteriorly and posteriorly. When, however, a woman is in the knee-chest, Sims or kneeling position, and the labia are separate, the vagina balloons out. This is the result of negative intra-abdominal pressure, transmitted to the vagina, causing the entry of air. Exceptionally, such air can enter the uterus, tubes and peritoneal cavity.
If the walls are separated, the vagina of the nulliparous married woman has a diameter of approximately 4-5 cm at its lower end and is twice as wide at its upper end. Although the width and length of the vagina show considerable individual variations, anatomical shortness or narrowness is rarely a cause of difficulty or pain on coitus because the vagina is distensible and accommodates itself. The functional width is determine to a large extent by the tone and contractions of surrounding muscles.
A raised double column form by underlying fascia can often be see running sagittally down the anterior wall and there is a less definite median ridge on the posterior wall Running circum- inferentially from these columns are folds of the epithelium (rugae) which account for a part for the ability of the vagina to distend during labour
Epithelium
The vagina is line by strat squamous epithelium which also extends onto and covers the vaginal cervix as far as the external os. The surface is normally devoid of keratin but is capable of becoming keratinized if it becomes exposed to, the air as in prolapse. The epithelium is many-layer, the basal cuboidal cells being the source of continuous production of the squamous cells above. The cells in the middle and superficial zones contain glycogen, which explains why the vagina stains deep brown with iodine. It shows cyclical histological changes in association with menstruation.
The epithelium does not contain glands of any kind and does not secrete in the ordinary sense of the word. The frequently used term vaginal me is, therefore strictly incorrect. Although it may in part represent a transudate, the vaginal secretion arises mainly from the constant breakdown of superficial epithelial cells. This breakdown liberates the contain glycogen which is act upon by Doderlein’s bacillus, a normal inhabitant of the vagina to produce lactic acid. The vaginal secretion, therefore, consists of tissue fluids, epithelial debris, electrolytes, proteins and lactic acid. The amount of the last is governe by the glycogen content of the epithelium and the presence of Doderlein bacilli but, in the adult healthy vagina, is in a concentration of 0.75 percent.
The pH varies
The pH varies with the level of the vagina, being highest in the upper part because of an admixture of alkaline cervical mucus. Estimates also vary according to the method used for its determination. Some authorities give the normal range for the adult non-pregnant woman as from 3.5 to 4.2. but the generally accepted figures are from 4.0 to 5.5 with an average of 4.5. The level varies with the time in the menstrual cycle and the effects of ovarian hormones on the vaginal epithelium and cervical secretion. During menstruation, the flow of alkaline blood raises the vaginal pH to levels of 5.8 to 6.8.
The acidity of the vagina is of great practical importance for it explains the resistance of the mature vagina to pyogenic organisms.
The vagina not only secretes’ it; it absorbs water, electrolytes and substances of low molecular weight. This property is utilize when therapeutic agents such as oestrogens and glucose are administer locally and can be a nuisance in that it permits the absorption of medicaments such as mercurials and arsenicals to cause systemic reactions. Absorption and reabsorption are believe to occur mainly in the lateral recesses of the lower vagina.
Fascia and muscle
The epithelium rests on a subepithelial connective layer which contains elastic tissue. Outside this are muscle coats in which the fibres are nearly all arranged in a criss-cross spiral fashion rather than in the outer longitudinal’ and ‘inner circular pattern which was describe in the past. The muscle of the vaginal wall is involuntary in type although there are sometimes a few intermingling
Globules of fluid, the sweating phenomenon, are said to collect on the surface during coitus and sexual excitation.
voluntary fibres contributed by muscles such as the levator ani at the sites of their insertions. Outside the muscle, layers is a strong sheath of connective tissue which has special condensations down. The anterior wall to form the pubocercia fascit. And down the posterior wall to the rectovaginal fascia. This fascial sheath fuses with that covering the levator ani muscles. The triang lar ligament and perineal muscles. The vaginal wall itself and the tissues around are extremely vascular so they usually bleed freely
at the time of injury and operation.
Changes in the vagina with age and parity
The vagina of the newborn child is under the influence of oestrogen which has crossed the placenta from the maternal circulation. The epithelium is therefore moderately well develop by the third or fourth day. When the vaginal acidity approaches that of an adult. By 10-14 days the oestrogen stimulus is lost and the epithelium atrophies and becomes devoid of glycogen. The pH then rises to approximately 7 and remains at that level until the approach of puberty. When with the onset of full ovarian function, the vagina assumes the features already described,
Throughout childhood.
Doderlein’s bacilli are present in small numbers but after puberty, they are the predominant organism. During pregnancy, the amount of glycogen is increase to a maximum and the acidity of the vagina is high (pH 3.5-4.5). After menopause, the epithelium atrophies and loses its glycogen. Döderlein’s bacilli are find in fewer numbers and the pH rises to a range of 6-8. In some women menopausal atrophy is slow to develop. Possibly because of the peripheral conversion of androgens produced by the adrenal cortex.
Marriage and regular coitus result in some stretching of the vaginal walls, and this is increase by childbearing. Repeated childbirth leads to obliteration of the rugae and the vagina becomes a smooth-walled and rather a patulous canal. After menopause, it undergoes contract- ure in length and width, but this change is to some extent counteracted by the continuance of regular coitus. The fornices become shallow, however, and the cervix no longer projects far into the vault When these changes are extreme the vagina is said to become tent-shape. Even in nulliparous women, the vagina loses its rugae after the climacteric.
The relationship of the vagina
Anterior
Embedded in the lower anterior vaginal wall is the urethra. Its muscles fuse with those of the vaginal coat without the intervention of fascia. So it is difficult to separate from the vagina at the time of operation. In close connexion to are Skene’s tubules which open into the urethra . Above the urethra, the vagina is directly related to the bladder, separated from it. By fascia and lose areolar tissue (Figure 2.7)
Posterior:
From below upwards the vaginal wall is in relation to the perineal body. The ampulla of the rectum and the peritoneum of the pouch of Douglas. At the level of the posterior fornix there is only vaginal wall. Fascia and extraperitoneal cellular tissue separating the peritoneal cavity from the exterior (Figure 2.12).
Lateral:
At its orifice, the vagina has on either side the sphincter vaginae (bulbospongiosus) muscle. The vestibular bulb, Bartholin’s gland and its duct, and
the triangular ligament (urogenital diaphragm) with its muscles. At a higher level is the levator ani with the paracolpos above, and the ischiorectal fossa below its insertion. The lateral fornix is relate to the lower parts of the cardinal ligament which are insert into it.
Superior :
The cervix dips into the upper and anterior part of the vagina: above this is the uterus itself. Overlying the lateral fornix and situated only 1-2 cm away is the ureter with the uterine vessels immediately above. These lie in the cellular tissue of the base of the broad ligament which is also an important relation. The uterosacral ligaments are just above the posterior fornix; between and above them is the peritoneal pouch of Douglas contain- ing loops of intestine. Higher and to the side are the fallopian tube and ovary (Figure 2.10).
Vascular connexions
Arterial :
These are: the vaginal artery mainly; branches of the uterine artery; branches of the internal pudendal artery; and twigs from the middle and inferior rectal arteries.