SEXUAL OFFENCES - FORENSIC ANATOMY

Female Genitalia

Recognition and interpretation of injuries and other changes of female genital tract need a knowledge and understanding of normal female genital anatomy. It should also be appreciated that the anatomy changes with age and puberty.

Important structures of female genitalia, which is also known as vulva, are clitoris, labia majora and minora, posterior fourchette, fossa navicularis, vestibule, urethral orifice, hymen and hymenal orifice.

Vestibule is the area which surrounds the vaginal and urethral orifice. Its margins are the clitoris anteriorly, the labia minora laterally and posterior fourchette posteriorly. At the lower part of the vestibule, extending from just below the hymen to the posterior fourchette is the fossa navicularis.

Hymen

Hymen is a rim of tissue or a membrane (sometimes it is not a complete rim) present at the vaginal opening, which is also called hymenal opening. From that point vaginal canal extends internally upward and backward ending at the cervix.

The area between the posterior fourchette and the anus is called perineum.

The white or pigmented line representing the point at which the two halves of the body join is called the ‘median raphe’, which runs from posterior fourchette to anus.

Median Raphe

Hymenal appearance

Hymenal configuration is the appearance of the hymenal membrane.

Description of the Hymenal injuries and lesions

The location or site of hymenal injuries and lesions are described and represented on a position of a ‘clock face’ with the victim supine. The 12 ‘O’ clock at the mons pubis and 6 ‘O’ clock at the coccyx.

Clock Face Description

 

  Common hymenal configurations are

1. Annular

 2. Crescentic

3. Fimbriated.

In annular hymen the hymenal tissue is present right around the hymenal or vaginal opening. In ‘crescentic’ hymen hymenal tissue is absent in the anterior half to two third leaving a gap around 12 ‘O’ clock position. In ‘fimbriated hymen’ edge of the hymen is highly folded, which gives the hymen a flower like appearance with multiple petal like or scalloped edge.

 

 Less common hymenal configurations are

1. Septate (two opening with band of tissue in the middle) 2. Cribriform (multiple openings) 3. Microperforate (extremely small hymenal opening) 4. Imperforate .

There is no evidence that hymen can be congenitally absent.

Appearance of hymen changes with age and pubertal status. In new born maternal oestrogen gives the hymen a fleshy appearance. After that with age it becomes thin and delicate and may lose anterior portion making it ‘crescentic hymen’. Then later it might change in to annular hymen. As puberty approaches the hymen thickens assume a fimbriated appearance. At the same time elasticity of the hymen increases.

Forensic anatomy of anus

Anal canal is the terminal part of the large intestine extending from rectum to the anal orifice. There are two muscles, involuntary internal sphincter muscle, which surrounds the anal canal and the external sphincter, a voluntary muscle at the anal verge. The anus is normally closed and opens for passage of gas or faecal matter.

The normal physiological ano-rectal reflex occurs when the internal anal sphincter relaxes as the rectum contracts in response to distension by faecal mass. The act of defecation is controlled by contraction of the external sphincter and only occurs after voluntary relaxation of the muscle.

The anus can easily accommodate at least one gentle examining finger without any sign of injury even in new born. Factors that affects the likelihood and nature of anal injury after abuse include the degree of penetration, the size of penetrating object, the degree of force used, degree of cooperation, use of lubricant, number and frequency of episodes, the person’s (if it is a child) age and how soon the victim is examined after the event.

 

 

Priyanjith Perera

12/12/12