34 Alan Farthing West London Gynaecological Cancer Centre, Queen Charlotte’s Hospital, Imperial College Healthcare NHS Trust, London, UK This chapter aims to summarize important aspects of the anatomy of the abdomen and the pelvis that should be known to the obstetric or gynaecological specialist. Many of the investigations and treatments we order on a daily basis require good anatomical knowledge in order to be properly understood. The anterior abdominal wall can be divided into four quadrants by lines passing horizontally and vertically through the umbilicus (Fig. 34.1). In the upper abdomen is the epigastrium, which is the area just inferior to the xiphisternum, and in the lower abdomen lie the right and left iliac fossae and the hypogastrium. Fig. 34.1 The abdomen can be divided into quadrants. The cutaneous nerve supply of the anterior abdominal wall arises from the anterior rami of the lower thoracic and lumbar vertebrae. The dermatomes of significant structures on the anterior abdominal wall are T7 (xiphisternum), T10 (umbilicus) and L1 (symphysis pubis). The blood supply is via the superior epigastric (branch of the internal thoracic artery) and the inferior epigastric (branch of the external iliac artery) vessels. During laparoscopy, the inferior epigastric vessels can be seen between the peritoneum and rectus muscle on the anterior abdominal wall and commence their journey superiorly from approximately two‐thirds of the way along the inguinal ligament closer to the symphysis pubis. Care needs to be taken to avoid them while using accessory trocars during laparoscopy and to ensure that they are identified when making a Maylard incision of the abdominal wall. Beneath the skin and the fat of the superficial anterior abdominal wall lies a sheath and combination of muscles including the rectus abdominis, external and internal oblique and tranversalis muscles (Fig. 34.2). Where these muscles coalesce in the midline, the linea alba is formed. Pyramidalis muscle is present in almost all women, originating on the anterior surface of the pubis and inserting into the linea alba. The exact configuration of the muscles encountered by the surgeon depends on exactly where any incision is made. Fig. 34.2 The layers of the anterior abdominal wall in tranverse section. The umbilicus is essentially a scar made from the remnants of the umbilical cord. It is situated in the linea alba and in a variable position depending on the obesity of the patient. However, the base of the umbilicus is always the thinnest part of the anterior abdominal wall and is the commonest site of insertion of the primary port in laparoscopy. The urachus is the remains of the allantois from the fetus and runs from the apex of the bladder to the umbilicus. Occasionally this can remain patent in newborns. In early embryological life, the vitelline duct also runs through the umbilicus from the developing midgut. Although the duct is severed long before delivery, a remnant of this structure is found in 2% of the population as a Meckel’s diverticulum. The aorta divides into the common iliac arteries approximately 1–2 cm below the umbilicus in most slim women (Fig. 34.3). The common iliac veins combine to form the inferior vena cava just below this and all these structures are a potential hazard for the laparoscopist inserting ports at the umbilicus. Fig. 34.3 The umbilicus in relation to the underlying vasculature in a thin patient. The anterior abdominal wall including the vulva, vagina and perineal areas are lined with squamous epithelium. The epithelium lining the endocervix and uterine cavity is columnar and the squamocolumnar junction usually arises at the ectocervix in women of reproductive age. This is an important site as it is the area from which cervical intraepithelial neoplasia (CIN) and eventually cervical malignancy arises. The bladder is lined by transitional epithelium that becomes columnar as it lines the urethra. The anal margin is still squamous epithelium but this changes to columnar immediately inside the anus and into the rectum. The genital tract, from the vagina, through the uterus and out through the fallopian tubes into the peritoneal cavity, is an open passage. This is an essential route for sperm to traverse in the process of fertilization but unfortunately it also allows the transport of pathological organisms that may result in ascending infection. The peritoneum is a thin serous membrane that lines the inside of the pelvic and abdominal cavities. In simplistic terms, it is probably best to imagine the pelvis containing the bladder, uterus and rectum (Fig. 34.4) and note that the peritoneum is a layer placed over these organs in a single sheet. This complete layer is then pierced by both the fallopian tubes and the ovaries on each side. Posteriorly the rectum also pierces the peritoneum where it connects to the sigmoid colon, and the area between the posterior surface of the uterus and its supporting ligaments and the rectum is called the pouch of Douglas. This particular area is important in gynaecology as the place where gravity‐dependent fluid collects. As a result this is where blood is found in ectopic pregnancies, pus in infections and endometriosis caused by retrograde menstruation. Fig. 34.4 Transverse view of the pelvic organs. The vulva is the area of the perineum comprising the mons pubis, labia majora and minora, and the opening into both the vagina and urethra (Fig. 34.5). The labia majora are areas of skin with underlying fat pads which bound the vagina. Medial to these are the labia minora, which consist of vascular tissue that engorges with blood during sexual arousal. Anteriorly they come together to form the prepuce of the clitoris and posteriorly they form the fourchette. The hymen is a fold of mucosa at the entrance to the vagina. It usually has a small opening in virgins and is only seen as an irregular remnant in sexually active women. To each side of the introitus are the ducts of the vestibular glands commonly known as Bartholin’s glands, which produce much of the lubrication during sexual intercourse. Fig. 34.5 Surface anatomy of the vulva.
Clinical Anatomy of the Pelvis and Reproductive Tract
Surface anatomy
The anterior abdominal wall
The umbilicus
Epithelium of the genital tract
The peritoneum
Vulva
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
