Ovaries

The two ovaries are solid ovoid/almond‐shaped structures, about 3 cm long, 2 cm wide, and 1 cm thick whose size and shape differs throughout life. Before puberty, they are smooth, dull white, and solid in consistency. During the reproductive years, the ovaries increase in size and have an irregular surface. Postmenopausally, they shrink and are covered with scar tissue (see Chapter 4 for more detail on ovarian anatomy, the oocyte, and folliculogenesis).

The ovaries develop on the posterior abdominal wall and descend to the level of the pelvic brim at the end of the fimbriae of the uterine tubes. As ovoid structures the ovaries have two poles:

1. The superior pole: receiving the ovarian vessels, nerves, and lymphatics through a peritoneal fold called the suspensory ligament of the ovary.
   
2. The inferior pole: attached to a fibromuscular band, the ligament of the ovary; continuous with the round ligament of the uterus as it crosses the uterine horns.

The anterior border of the ovary is covered by a double fold of the broad ligament called the mesovarium. The lateral surface is related to the internal and external iliac vessels and separated from the obturator nerve by the parietal peritoneum. The medial surface is closely approximated to the fimbriae of the uterine tubes.

• Blood supply: from the gonadal or ovarian arteries originating from the anterolateral side of the abdominal aorta. Each artery descends on the posterior abdominal wall, anterior to psoas muscle where it crosses the ureter obliquely. As it descends over the pelvic brim the ovarian artery passes over the external iliac vessels and enters the suspensory ligament. Approaching the lateral side of the ovary, the ovarian artery gives a branch to the uterine tube, which anastomoses with the uterine artery before reaching the ovary.
  
• Venous drainage: through ovarian plexuses found in the suspensory ligaments that accompany the ovarian arteries. The plexuses join on each side to form ovarian veins that drain asymmetrically into the interior vena cava: directly on the right and via the left renal vein on the left.
  
• Lymphatic drainage: towards the para‐aortic nodes in the lumbar region around the origin of the ovarian arteries.
  
• Innervation: sympathetic innervation from T10 and 11 spinal segments via the ovarian plexus is carried along the ovarian arteries. As sensory fibres travel with the sympathetics, ovarian pain is referred to the periumbilical region. Parasympathetic fibres can reach the ovaries via the inferior hypogastric plexus and bring about vasodilation.

Fallopian Tubes

Their function is to carry the expelled oocyte from the ovary to the uterus and provide the site of fertilization and early embryo development (Chapter 8 discusses the role of the Fallopian tubes in early embryo development in more detail). Fallopian tubes are about 10  cm in length and extend posterolaterally from the uterine horns to open into the peritoneal cavity near the medial surface of the ovary. They are suspended bilaterally in the free anterosuperior edge of the broad ligament, called the mesosalpinx. The uterine tube has four parts from lateral to medial:

1. Infundibulum: the lateral/distal end of the tube also known as the fimbriated portion of the uterine tube. It is characterized by finger‐like projections surrounding the opening into the peritoneal cavity (abdominal ostium). The fimbriae surround the medial surface of the ovary; one large fimbria usually extends and is closely related to the superior pole of the ovary.
   
2. Ampulla: the normal site of fertilization. It is the widest and longest part, forming more than half of the length of the uterine tube.
   
3. Isthmus: a thick‐walled, narrow and straight portion of the tube, about 2.5 cm in length that enters into the uterine horn. Functions as a reservoir for spermatozoa.
   
4. Uterine: the most medial part, which is also known as the intramural segment. It is about 1–2.5 cm long and passes through the wall of the uterus to open into the cavity via the uterine ostium.
   
   
   
   • Blood supply: from tubal branches of the ovarian artery and the uterine artery, originating from the abdominal aorta and internal iliac artery respectively. Branches from both arteries supply the tube from opposite ends and anastomose with each other.
     
   • Venous drainage: through the ovarian and uterine venous plexuses.
     
   • Lymphatic drainage: towards the para‐aortic lymph nodes of the abdomen.
     
   • Innervation: by the ovarian and uterine plexuses.

Uterus

The uterus is a hollow pear‐shaped muscular structure, about 7.5 cm long, 5 cm wide, and 2.5 cm thick, that lies in the true pelvis during the nonpregnant phase. Like the ovaries the uterus changes size over the course of life, growing during puberty and atrophying postmenopausally. The position of the uterus changes relative to fullness of the urinary bladder/rectum, and the stage of pregnancy. It is typically positioned on top of the urinary bladder, angled anterosuperiorly relative to the axis of the vagina (anteverted), and flexed anteriorly relative to the cervix (anteflexed). The uterus has two surfaces:

1. A superior surface: related to the intestines.
   
2. An inferior surface: separated from the urinary bladder by the vesicouterine fascia.

The uterus can be considered as three anatomically distinct regions named from superior to inferior:

1. Fundus: the rounded part that lies superior to the level of the uterine ostia (openings of the uterine tubes). Pelvic peritoneum covers the fundus and extends inferiorly toward the body.
   
2. Body: extending from the fundus above to the cervix inferiorly; it receives the openings of the uterine tube at the junction between the fundus and the body in a region termed the cornua or uterine horn. The body narrows inferiorly within a segment called the isthmus demarcating where the cervix begins. The body is enveloped in peritoneum that extends laterally as the mesometrium of the broad ligament
   
3. Cervix: the inferior third of the uterus can be further subdivided into two parts:
   
   
   
   • Supravaginal part: extending from the isthmus to the vagina.
     
   • Vaginal part: protruding into the vagina and is surrounded by a sulcus. The sulcus is termed a fornix and is deepest posteriorly.

An anterior wall of the cervix is located posterior to the urinary bladder and is attached above the bladder trigone by dense connective tissue. It is related to ureters that pass laterally then anterior to the anterior fornix. The posterior wall is covered by peritoneum forming the anterior wall of the rectouterine pouch.

The cervical canal is continuous with the cavity of the body through the internal os and with the vagina through the external os. The external os is normally at the level of the ischial spines.

Many ligaments and muscles support the uterus and keep it centred in the pelvic cavity. They also prevent the uterus from being pushed through the vagina and act as passageway for vessels, lymphatics and nerves to get to pelvic organs:

• The broad ligament of the uterus: a double layer of peritoneum enveloping the uterus and extending laterally to pelvic wall and floor, it comprises:
  
  
  
  • – Mesosalpinx: the upper border covering the uterine tubes.
    
  • – Mesovarium: the small posterior extension of mesentery holding the ovaries.
    
  • – Mesometrium: the extension that spans over the body of the uterus inferior to mesosalpinx.
  
  
• Suspensory ligament of the ovary (infundibular ligament): the upper lateral part of the broad ligament covering the ovarian vessels and nerves. It extends laterally as a fold over the iliac vessels on its way to the superior pole of the ovary.
  
• The round ligament of the ovary: extends from the inferior pole of the ovary to the junction between the uterus and the uterine tubes.
  
• The round ligament of the uterus: continuous with the ligament of the ovary, this ligament extends from the junction between the uterus and the uterine tubes to the deep inguinal ring. It passes through the inguinal canal and ends as fibrous tissue blending with the subcutaneous tissue in the labia majora. This ligament contributes to the uterus position in an anteflexed–anteverted position.
  
• The transverse cervical (cardinal) ligament: a thickening of connective tissue at the base of the broad ligament extending laterally to the pelvic wall. It is key to the support of the the cervix and uterus.
  
• The uterosacral ligaments: fibrous tissue that extends from the cervix to the sacrum. It maintains the cervix and positions the uterus in an anteverted state against the forward pull of the round ligament.
  
• Pubovaginalis muscle: a part of levator ani (pelvic diaphragm) that plays an important role in supporting the vagina and positioning the cervix.

• Blood supply: from branches of the uterine arteries. As the ovarian arteries anastomose with the uterine arteries, there is also contribution from the ovarian arteries to the blood supply of the uterus.
  
• Venous drainage: the uterine veins converge to form a uterine venous plexus around the cervix and drain through the internal iliac veins.
  
• Lymphatic drainage: follows the arterial supply to four sets of lymph nodes:
  
  
  
  • – The fundus and upper part of the uterine body drain towards para‐aortic lymph nodes.
    
  • – The lower part of the uterine body and small part of the cervix drain towards the external iliac nodes.
    
  • – The cervix mainly drains towards the internal iliac and sacral lymph nodes.
    
  • – A small region of the uterine horns drain toward the superficial inguinal nodes along with the round ligament of the uterus.
  
  
• Innervation: the uterovaginal nerve plexus from the inferior hypogastric plexus carries sympathetic, parasympathetic, and visceral afferents fibres to the uterus. Sympathetic fibres originate from T10‐L1 spinal segments and parasympathetic fibres from S2‐S4. Visceral afferents conducting pain from the fundus, body, and upper cervix follow the sympathetic pathway and are carried back to the inferior thoracic/superior lumbar ganglia. Visceral afferents conducting pain from the cervix follow the parasympathetic fibres pathway and are carried back toward S2‐S4 spinal ganglia.

Vagina

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