Anatomy - complete hysterectomy, bilateral adnexectomy, sentinel node biopsy pelvic bilateral laparoscopic, robot-assisted laparoscopy (DaVinci)

The human pelvis is a complex ring structure that fulfills two main functions. On one hand, it forms the lower closure of the trunk and thus supports the weight of the upper body. On the other hand, it transfers this weight to the lower limbs, which is crucial for the upright posture and locomotion of humans.

The pelvis is composed of several bony elements. The foundation is formed by the two hip bones, also known as the pelvic girdle or Cingulum membri inferioris. In between is the sacrum. The Os coxae consists of three main components:

1. The ilium (Os ilium), consisting of the Corpus ossis ilii and the Ala ossis ilii.
2. The ischium (Os ischii), consisting of the Corpus ossis ischii and the Ramus ossis ischii.
3. The pubis (Os pubis), consisting of the Corpus ossis pubis, the Ramus superior, and the Ramus inferior ossis pubis.

These bones and the sacrum are connected by various types of connections, including ligamentous connections, cartilaginous connections, and joints:

1. Ligamentous connections include the Membrana obturatoria, the Ligamenta sacroiliaca, sacrotuberale, and sacrospinale.
2. Fibrocartilaginous connections are made by the Symphysis pubica.
3. Joint connections include the Articulation sacroiliaca and the Articulatio sacrococcygea.

There are various ligaments involved in the joints:

• The Ligg. sacroiliaca anteriora and posteriora are ligaments that connect the upper and lower ends of the ilium to the sacrum.
• The Ligg. sacroiliaca interossea extend between the sacrum and the Tuberositas ossis sacri and Tuberositas iliaca.
• The Lig. iliolumbale runs from the 4th and 5th lumbar vertebrae to the Crista iliaca and the Tuberositas iliaca.
• The Ligg. sacrotuberale et sacrospinale are additional ligaments that act on the Articulatio sacroiliaca.
• The Lig. sacrococcygeum anterius, the Lig. sacrococcygeum posterius profundum, and the Lig. sacrococcygeum posterius superficiale are ligaments that connect the sacrum to the coccyx.

The pelvis is divided into two main parts: 

• the greater pelvis (Pelvis major) and 
• the lesser pelvis (Pelvis minor). 

The Linea terminalis is the dividing line between them. The greater pelvis, above the Linea terminalis, contains the space between the two iliac wings, while the lesser pelvis includes the pelvic inlet, the pelvic outlet, and the pelvic walls.

The pelvic walls are covered by connective tissue called fasciae. These fasciae are important for the stability and delineation of the pelvic organs. Furthermore, there are openings in the pelvic walls that allow the passage of blood vessels, nerves, and muscles that run between the pelvis and the gluteal region. The pelvic region is rich in neurovascular structures that play an important role in supplying the pelvis and the lower extremities.

The pelvic diaphragm is a term that describes the muscular structure forming the pelvic floor. It consists of three main muscles:

M. levator ani: The muscle forms a funnel-like structure with an open tip downward. At its front side, the urogenital hiatus opens, a gap extending from the posterior side of the pubic bone to the perineal center. The M. levator ani frames this hiatus with its two limbs, which unite in front of the rectum at the perineal center. This center forms the muscular and connective tissue foundation of the perineum. The urogenital hiatus itself is covered and closed by the urogenital diaphragm. The levator ani is composed of the following muscles:

• M. puborectalis,
• M. pubococcygeus
• M. iliococcygeus.

M. coccygeus: This muscle extends from the ischial spine to the coccyx and runs like the M. levator ani in the pelvic floor.

M. sphincter ani externus: This is the external anal sphincter and consists of striated muscle tissue. It has three parts: Pars subcutanea, Pars superficialis, and Pars profunda. The Pars subcutanea consists of superficial fibers running in front of and behind the anus. The Pars superficialis forms muscle plates on the sides of the rectum and acts like a clamp. The Pars profunda consists of circularly arranged muscle fibers surrounding the rectum, enabling voluntary closure of the intestine.

The pelvic floor also contains the urogenital diaphragm, which closes the urogenital hiatus. It consists of various muscles located in the superficial perineal space (superficial pelvic floor space) and the deep perineal space (deep pelvic floor space):

M. transversus perinei superficialis: a flat, transversely running muscle of the pelvic floor. It belongs to the superficial perineal muscles and extends from the pubic bone (Ramus inferior ossis pubis) to the middle of the perineum, where it merges with the muscle of the opposite side or connects with the fibers of the external anal sphincter.

M. transversus perinei profundus: It lies below the M. transversus perinei superficialis and is stronger and more deeply embedded in the structure of the pelvic floor compared to it. The muscle also runs transversely from the inner edge of the ischium (Ramus inferior ossis ischii) to the midline of the body, where it meets the muscle of the opposite side or connects with the fibers of the external sphincter of the urethra and partially the M. sphincter ani externus.

M. sphincter urethrae externus: This is the external sphincter of the urethra and is formed by the M. transversus perinei profundus.

Additionally, there are two muscles adjacent to the internal genital organs:

M. ischiocavernosus: This muscle attaches to the ischial branches and covers the clitoral corpus cavernosum. It is involved in erection.

M. bulbospongiosus (M. bulbocavernosus): This muscle runs from the perineal center and covers the vestibular gland. In women, it can narrow the vestibule of the vagina.

The pelvic fascia, also known as the pelvic fascia, plays a crucial role in the structure and function of the pelvis. It comprises a series of connective tissue layers that support the pelvic organs, envelop the musculature, and contribute to the overall stability of the pelvic floor. This fascial structure is divided into two main parts: the parietal pelvic fascia and the visceral pelvic fascia.

1. Parietal pelvic fascia (Fascia endopelvina) This fascial layer lines the inner walls of the pelvis. It covers the muscles forming the pelvis, including the M. piriformis and the M. obturator internus. The parietal pelvic fascia contributes to the demarcation of pelvic spaces and forms important anatomical structures such as the retropubic space and the ischioanal space. It also provides an attachment surface for other fasciae and ligaments that hold the pelvic organs in position.
2. Visceral pelvic fascia (Fascia propria organi): The visceral pelvic fascia encloses the pelvic organs and adapts to their shape changes. Each organ is surrounded by a specific part of the fascia, giving it a unique name. Additionally, this fascia forms various septa that separate the organs from each other, including the vesicovaginal septum between the bladder and vagina and the rectovaginal septum between the rectum and vagina. The accompanying connective tissue, which carries blood vessels and nerves to the respective organs, is specifically named: as Paraproctium, supporting the rectum, as Paracystium, supporting the bladder, as Parametrium, surrounding the uterus, and as Paracolpium, structuring the vagina.

There are also openings in the wall of the lesser pelvis that allow the passage of nerves and blood vessels:

Obturator canal: A canal for the obturator nerve and vessels, which run from the lesser pelvis to the inner thigh.

Ischiadic foramina: These allow the passage of vessels, nerves, and muscles from the lesser pelvis into the gluteal region. There is the greater sciatic foramen and the lesser sciatic foramen.

Finally, the lesser pelvis houses internal genital organs, the bladder, part of the ureter, and the rectum. These organs are surrounded by fat and connective tissue, and vessels and nerves run in the pelvic wall and connective tissue to supply and innervate them.

• Origin of the Rectum: Extension of the sigmoid colon, beginning at the upper edge of the third sacral vertebra.
• Shape and Curvatures:
  • Sacral Flexure: Follows the contour of the sacrum downward.
  • Anorectal (perineal) Flexure: Bends backward in the perineal area, bulging forward.
  • Lateral Flexures: Occasionally variable curvatures in the frontal plane.
• Structural Features:
  • Length of about 15 cm.
  • Three semilunar transverse folds; the most prominent is the Kohlrausch fold approximately 6 cm above the anus on the right side.
• Continuation into the Anal Canal: Ampulla recti above the anal canal, which expands when filled.
• Boundaries and Location:
  • Upper Section: Covered by peritoneum in front and laterally, retroperitoneal (Rectum fixum).
  • Peritoneal Contact: In women, the peritoneum meets the posterior vaginal fornix and the back of the uterus (rectouterine excavation) at the middle transverse fold.
  • Below the Kohlrausch Fold: Completely extraperitoneal.
• Anatomical Neighborhood:
  • Adjacent to the sacrum, coccyx, and the posterior parts of the levator ani muscle.
  • Adjacent to the vagina in front.
• Vasculature and Innervation:
  • Median sacral artery, superior rectal artery.
  • Sympathetic trunks, lateral sacral arteries, sacral plexus in retrorectal connective tissue.

Pelvic and intramural part of the ureter: Section extending from the crossing of the linea terminalis with the sacroiliac joint to the entry into the bladder wall.

• Course of the ureter: On the right, the ureter runs above the initial segment of the external iliac artery and on the left over the bifurcation of the common iliac artery.
• Peritoneal covering: Initially covered by peritoneum, the ureter follows the lateral wall of the small pelvis, positioning itself ventral to the internal iliac artery.
• Change of direction of the ureter: Near the ischial spine, the ureter turns frontal and medial towards the bladder, separating from the peritoneum.
• Crossing with the broad ligament of the uterus: The ureter crosses this ligament, running below the uterine artery and near the lateral vaginal fornix.
• Intramural part: This part of the ureter obliquely penetrates the bladder wall and opens into the bladder at the ureteral orifice.

The urinary bladder is a muscular hollow organ that serves to store urine and later expel it through the urethra. The bladder's capacity is normally 300-500 ml. The bladder can be divided into different parts,

• the bladder apex (Apex vesicae),
• the bladder body (Corpus vesicae),
• bladder base (Fundus vesicae),
• bladder neck (Collum or Cervix vesicae), transition to the urethra

The apex is connected to the median umbilical ligament (Chorda urachi), the obliterated allantoic duct that leads to the navel.

The peritoneum extends from the bladder to the uterus (Excavatio vesicouterina).

The trigone of the bladder is a roughly triangular, fold-free mucosal area located at the base of the urinary bladder. This triangle is formed by the two openings of the ureters (Ostia ureterum) and the internal opening of the urethra (Ostium urethrae internum). The interureteric fold (Plica interureterica) bounds the trigone posteriorly, and anteriorly it forms an angle that extends into the urethra. In this area, the tunica mucosa is closely fused with the tunica muscularis. In other areas of the bladder, there exists a tunica submucosa, which forms a slightly movable buffer zone between the mucosa and muscle layer, allowing the bladder to fill and empty without difficulty.

The female urethra is approximately 3-5 centimeters long. It is anteriorly connected to the connective tissue of the septum urethrovaginale. Its course begins in the bladder at the ostium urethrae internum and ends in the vestibulum vaginae, after passing through the urogenital diaphragm at the ostium urethrae externum.

The wall of the female urethra consists of various layers:

• the outer tunica adventitia,
• the middle tunica muscularis,
• the tunica spongiosa, and
• the tunica mucosa.

The outer circular muscle layer near the bladder forms the M. sphincter urethrae internus (M. sphincter vesicae internus), which belongs to the bladder. The actual M. sphincter urethrae (formerly M. urethrae externus) is located in the urogenital diaphragm.

Ovary (Ovarium)

The ovary (Ovarium) is located laterally in the pelvic region and runs in a vertical orientation. It has an inner surface facing the pelvic interior (Facies medialis/intestinalis) and an outer surface directed towards the lateral pelvic wall (Facies lateralis). The rounded free edge is called the Margo liber, and at the anterior edge, the Margo mesovaricus, the mesovarium is attached, which is a structure of the broad ligament of the uterus (Lig. latum uteri).

There are two poles:

• Extremitas uterina
• Extremitas tubaria

The hilum ovarii, where vessels and nerves enter, is located at the attachment of the connective tissue of the ovary, known as the mesovarium, at the Margo mesovaricus.

The ovary is connected to the pelvic wall at the extremitas tubaria by the suspensory ligament of the ovary. The ovarian vessels (Vasa ovarica), lymphatic vessels, and nerves run along this suspensory ligament.

The proper ovarian ligament lies between the ovary (extremitas uterina). This is located directly behind the tubal angle. The artery R. ovaricus of the uterine artery runs here.

The ovary is supplied by:

• A. ovarica
• Ramus ovaricus from the uterine artery.

These arteries form anastomoses at the Margo mesovaricus and supply the ovary with blood.

Veins transport the venous blood via the right ovarian vein to the inferior vena cava and via the left ovarian vein to the left renal vein. Part of the blood flows through the uterine plexus to the internal iliac vein.

The ovary is located in the abdominal cavity (intraperitoneal) in the ovarian fossa. Here, in the retroperitoneum, run the obturator nerve, obturator vessels, and external iliac vessels. Medially, the umbilical artery and uterine artery also run.

The Fallopian Tube (Tuba uterina, Salpinx)

The fallopian tube, also known as the tuba uterina, is about 10-15 centimeters long and 2-5 millimeters thick. It runs intraperitoneally along the upper free edge of the broad ligament of the uterus (Ligamentum latum uteri), from the corner of the uterus to the ovary. In the mesosalpinx, the blood vessels and nerves to the fallopian tube run, additionally fastening the fallopian tube to the broad ligament.

The fallopian tube itself can be divided into different sections:

• Infundibulum tubae uterinae (+ Ostium abdominale tubae uterinae)
• Fimbriae tubae uterinae,
• Ampulla tubae uterinae
• Isthmus tubae uterinae
• Pars uterina.

The blood supply of the tuba uterina is provided by small branches (Rr. tubarii) from the arteries A. ovarica and A. uterina, which run in the mesosalpinx and anastomose with each other. Veins accompany the arteries and drain into the ovarian vein and the uterine/uterovaginal plexus.

The Uterus

The uterus, also known as the womb, is a hollow, muscular organ in the female body that plays an important role during pregnancy and childbirth.

The uterus consists of:

• the body (Corpus uteri),
• the isthmus uteri
• the cervix (Cervix uteri)

The average length of the uterus is about 7.5 cm, the width 4 cm, and the thickness 2.5 cm.

The fundus: uteri represents the upper section of the uterus, located above the entry points of the fallopian tubes. Its lateral walls are connected to the broad ligament (Ligamentum latum uteri). At the lateral edges of the uterus, where the fallopian tubes enter the uterus, the tubal angle is formed. From the tubal angle, the proper ovarian ligament extends to the ovary, while the round ligament of the uterus extends to the inguinal canal.

Cervix uteri: The cervix extends with its conical lower third into the vagina. It is divided into the supravaginal portion of the cervix (Endocervix) and the vaginal portion of the cervix (Ectocervix or simply Portio). In the upper area of the vagina, the cervix uteri forms the anterior and posterior vaginal fornices (Fornix vaginae) between the portio and the vaginal wall.

Portio vaginalis: At the end of the portio vaginalis is the external os, also known as the ostium uteri (Orificium externum uteri).

The portio vaginalis normally has a reddish color and is covered with stratified, non-keratinized squamous epithelium, similar to the vagina. At the transition to the ostium uteri, this epithelium changes to the single-layered, high columnar epithelium of the cervical canal (Canalis cervicis). Between puberty and menopause, the cylindrical epithelium of the cervical canal can migrate outward onto the portio (ectropion), leading to more intense redness. With a colposcopy, precancerous stages and cancer can be detected in this area.

Ligaments of the Uterus (Uterine Ligaments):

Cardinal ligament: This ligament runs laterally on the uterus and extends to the vagina. It divides into:

• Bladder pillar (Paracystium) in front
• Rectal pillar (Paraproctium) behind
• Towards cervix (Paracervix) laterally
• Towards vagina (Paracolpium) laterally

Parametria:

• anterior = Paracystium,
• lateral = Uterovaginal pillar, cardinal ligament,
• posterior = Paraproctium

Pubovesical ligament: This ligament runs from the symphysis (pubic symphysis) to the bladder and supports the anterior wall of the vagina.

Vesicocervical ligament: This ligament extends from the cervix uteri to the bladder and provides support.

Vesicovaginal ligament: This ligament runs from the vagina to the bladder and supports the bladder.

Lateral vesical ligament: It runs from the tendinous arch of the pelvic fascia to the bladder and contributes to the stability of the bladder. The inferior vesical artery also runs here.

Sacrouterine ligament: This ligament connects the cervix uteri with the rectum (end intestine) and the sacrum. It forms a peritoneal fold and is an important part of the posterior support of the uterus.

Round ligament of the uterus (Lig. rotundum, round uterine ligament): This ligament runs from both sides of the tubal angle to the internal inguinal ring through the inguinal canal into the connective tissue of the mons pubis and the labia majora.

The peritoneum, also known as the peritoneum, forms a kind of double layer in the pelvic area of the woman, covering and protecting the internal organs.

The peritoneum lies like a cloth on the uterus. In front, it covers the bladder and the anterior wall of the uterus, forming a depression at the level of the cervix uteri, called the vesicouterine excavation. It further extends over the fundus and onto the posterior wall to the posterior fornix of the vagina. Here, another depression is formed, called the rectouterine excavation or Douglas space. The peritoneum then covers the anterior wall of the rectum. The Douglas space is the deepest point in the female pelvis.

Broad Ligament of the Uterus (Ligamentum latum uteri): From the lateral edges of the uterus, broad peritoneal tissue, the Lig. latum uteri, extends to the lateral pelvic wall. Between the two layers of the peritoneum (peritoneal duplication), there is connective tissue known as the parametrium or paracervix. Structure of the Ligamentum latum uteri:

• Connective tissue
• Blood vessels
• Nerves

The ureter runs near the posterior side of the Lig. latum and bends inward and forward above the pelvic floor. It crosses under the uterine artery.

The Lig. latum uteri consists of three parts:

• the mesometrium, laterally of the uterus including the uterine artery and veins from the uterovaginal plexus
• the mesosalpinx, in the area of the tube
• the mesovarium, in the area of the ovary including the proper ovarian ligament, suspensory ligament of the ovary

Vagina

Length and Structure: The vagina is a muscular and connective tissue organ with a length of about 8-11 cm. In its non-stretched state, it shows a characteristic H-shaped structure in cross-section.

Anatomical Orientation: Naturally, the vagina runs from below forward to above backward, adapted to the shape of the female pelvis.

Vaginal Walls:

• Anterior wall (Paries anterior): This wall is shorter due to the presence of the portio vaginalis uteri, a part of the cervix that protrudes into the vagina.
• Posterior wall (Paries posterior): Longer than the anterior wall, it forms the larger posterior vaginal fornix (Fornix posterior).

Vaginal Fornices (Fornix vaginae):

• There are a total of four fornices: the posterior fornix, anterior fornix, and two lateral fornices, which form around the portio vaginalis of the uterus.

Opening and Entrance:

• Vaginal orifice (Ostium vaginae): The opening of the vagina opens into the vestibule of the vagina, directly below the urogenital diaphragm.
• Vaginal introitus (Introitus vaginae): The entrance to the vagina, where the hymen or its remnants, the hymenal caruncles, are located.

Vaginal Wall Features:

• The wall of the vagina is soft in younger years and shows characteristic transverse folds, known as vaginal rugae, which contribute to flexibility and distensibility.

Position in the Pelvis:

• The vagina runs between the rectum and the bladder or urethra. Between these structures are the rectovaginal septum and the vesicovaginal or urethrovaginal septum, which serve as separating membranes.

Features of the Posterior Vaginal Fornix:

• The posterior fornix of the vagina forms the lower end of the rectouterine excavation, also known as the Douglas space, and is covered by peritoneum.

Vascular Supply:

• The uterine artery reaches the cervix uteri near the lateral fornices of the vagina. At this anatomical site, the ureter crosses under the uterine artery, which is significant during surgical procedures.

Mons pubis

The mons pubis is a triangular elevation of connective tissue located above the symphysis. In adult women, this elevation bears pubic hair.

Labia majora and minora pudendi

Labia majora pudendi:

• The outer labia, also known as labia majora pudendi, contain subcutaneous fat tissue that forms them into raised skin folds.
• They form a protective barrier for the vagina and enclose the labia minora.
• The anterior and posterior connection of the labia majora is referred to as the commissura labiorum anterior et posterior.

Labia minora pudendi:

• The labia minora, also called labia minora pudendi, are thin, without fat tissue, but rich in sebaceous glands.
• They surround the vestibule of the vagina (vestibulum vaginae).
• Anteriorly, the labia minora form the frenulum clitoridis and the prepuce of the clitoris, posteriorly the frenulum labiorum.

Vestibule of the vagina (vestibulum vaginae)

The vestibule of the vagina is laterally bounded by the labia minora, anteriorly by the frenulum clitoridis, and posteriorly by the frenulum labiorum. Within the vestibule are:

• The vaginal opening (ostium vaginae)
• The external urethral opening (ostium urethrae externum)
• The ducts of the major and minor vestibular glands (glandulae vestibulares majores et minores)

Glands of the vestibule of the vagina

Bartholin's glands (glandulae vestibulares majores):

• These paired, pea-sized glands are located in the urogenital diaphragm.
• Their ducts open on the inner side of the labia minora, near the ostium vaginae.
• They produce a secretion to lubricate the vaginal entrance.
• If the ducts become blocked, Bartholin's cysts can form, and if these become inflamed, it is referred to as a Bartholin's abscess.

Minor vestibular glands (glandulae vestibulares minores):

• These are clusters of small glands that open into the vestibule of the vagina.

Paraurethral glands (Skene's glands):

• These glands open beside the urethra and are also called ductus paraurethrales.

Hymen

The hymen is a membrane that separates the external from the internal genital area.

Vulva and erectile tissue

Clitoris:

• The clitoris consists of the crura clitoridis, the corpus clitoridis, and the glans clitoridis. It corresponds to the corpora cavernosa penis in males.

Bulbus vestibuli:

• The two bulbi vestibuli are located laterally to the vestibulum vaginae and correspond to the corpus spongiosum penis in males.

Regional Lymph Nodes of the Uterus

The regional lymph nodes of the uterus are located along the major vessels. They can be divided into the following groups based on their location:

• Nll. lumbales: These lymph nodes are situated in the lumbar region, both beside and on the aorta. They receive lymph from the upper part of the uterus, particularly the fundus.
• Nll. iliaci communes: Positioned along the common iliac artery, they serve as central collection points for lymph fluid from the uterus.
• Nll. iliaci externi et interni: These nodes follow the course of the arteries of the same name and play an essential role in uterine lymph drainage.
• Nll. interiliaci: They are located between the external and internal iliac arteries.
• Nll. glutei superiores et inferiores: These lymph nodes are found at the exit point of the corresponding arteries.
• Nll. subaortici: These are located at the aortic bifurcation and are significant for lymph drainage in this area.
• Nll. sacrales: They lie on the pelvic surface of the sacrum and receive lymph from the deep pelvic region.
• Nll. parauterini: Located directly next to the uterus in the broad ligament, they are closely associated with the lymphatic supply of the uterus.
• Nll. inguinales superficiales: These superficial lymph nodes are located subcutaneously on the front of the thigh, just below the inguinal ligament.

Main Pathways of Lymphatic Drainage

The lymphatic drainage of the uterine body proceeds through various pathways to specific lymph node groups:

Pelvic Lymph Node Stations

• The lymph primarily flows into the Nll. iliaci interni, externi, and communes, which are located along the internal, external, and common iliac arteries.
• The Nll. obturatorii, located near the obturator foramen, are particularly frequently involved.
• Another important station is the Nll. interiliaci, located between the external and internal iliac arteries.

Paraaortic Lymph Node Stations

• From the pelvic lymph nodes, part of the lymph moves further to the Nll. lumbales, located bilaterally to the aorta in the lower lumbar region.
• These lymph nodes are of particular importance as they often represent the first stations for metastatic deposits from the uterine fundus.

Inguinal Lymphatic Drainage

• A smaller portion of the lymph drains via the ligamentum teres uteri into the inguinal canal and further to the Nll. inguinales superficiales.
• This route is particularly relevant for metastasis to the superficial inguinal lymph nodes.

Sacral and Subaortic Lymphatic Drainage Pathways

• Through posterior drainage pathways, lymph is also directed to the Nll. sacrales, located on the anterior surface of the sacrum, and to the Nll. subaortici, located at the bifurcation of the aorta.