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Gynaecological Anatomy

Introduction

The female reproductive system consists of:

  1. Ovaries
  2. Uterine Tubes
  3. Uterus
  4. Vagina
  5. External genitalia

 

Some of the organs are stabilised within the pelvic cavity by ligaments and folds of the peritoneum, for example:  

 

Broad Ligament - The ovaries, uterine tubes, and uterus are enclosed within this a mesentery (a double fold of peritoneum). This ligament attaches to lateral walls and pelvic floor of pelvic cavity and thus stabilises the organs within it and prevents their side to side movement.

    Mesovarium – This is a thick fold of peritoneum which stabilises the position of the ovaries

      Ovarian ligament -  (Round ligament of ovary) – Attaches the ovaries to the lateral wall of uterus

        Infundibulopelvic ligament – Attaches the ovary to the pelvic wall and contains the main blood vessels which enter the ovary at the hilum

          Suspensory ligaments of the uterus (round ligament, uterosacral ligament and cardinal ligament) – Stabilises the uterus

             

              Figure 1: Ligaments of the uterus and ovaries

              Peritoneum from the abdomen descends into the pelvic cavity as far down as the superior surface of the bladder. However, it reflects back up to the abdomen and covers various organs of the reproductive system:

               

              1. The peritoneum covers superior surface of bladder
              2. Reflects onto the body of the uterus, covers the fundus and posterior wall
              3. Continues down posterior wall of vagina
              4. Reflects onto anterior wall of rectum

               

              During this journey of the peritoneum it gives off the broad ligament (see above) and  because of the way it reflects from one organ to another, various pouches are formed:

               

              Vesicouterine pouch –  between the bladder and uterus as peritoneum reflects from the bladder onto the uterus  

               

              Rectouterine pouch – between the uterus and rectum as the peritoneum reflects from the vagina onto the anterior wall of rectum

                Figure 2 Sagittal section demonstrating the rectouterine and vesicouterine pouches

                This article will briefly describe the anatomy of each component of the female reproductive system.

                 

                Ovaries

                These are paired oval shaped organ which are 5cm long, 2cm wide, and 8mm thick. They lie against the lateral walls of the pelvic cavity in a depression called the Ovarian Fossa. They are stabilised by the mesovarium, the ovarian ligament and the infundibulopelvic ligament (see above). These organs are responsible for the process of oogenesis and release the ova into the uterine tubes.

                 

                Arterial supply

                • Ovarian artery  - a branch of the abdominal aorta
                • Uterine artery -  branch internal iliac artery

                 

                Venous drainage

                • Ovarian veins – these veins are formed from tributaries of the pampiniform plexus which is found in the broad ligament near the ovaries. The right one drains into the inferior vena cava directly and the left one drains into the left renal vein which in turn drains into the inferior vena cava

                 

                Innervation

                Autonomic – via the ovarian plexus

                Visceral afferents – accompany the sympathetic fibers to T10 – T12 level of the spinal cord sensory ganglia

                 

                Histology

                The surface of the ovaries is covered by visceral peritoneum (germinal epithelium) which consists of columnar epithelium cells

                Underneath this layer is the tunica albuginea which is a dense connective tissue layer

                 

                Internally, the ovaries are subdivided into a cortex and medulla. The cortex is where the gametes are produced.

                 

                Uterine (Fallopian) Tubes

                These are the ducts that take the ovum from the ovary to the uterus when ovulation occurs. There are two uterine tubes (one for each ovary). They are hollow muscular and are about 13 cm long. Each one is divided into four parts:

                 

                1. The infundibulum – this is the part that is closest to the ovary and has finger-like projections called FIMBRIAE that drape over the ovary. There is cilia lining the infundibulum which help to propel the ovum down the tube
                2. The ampulla – this is the widest part of the tube and the smooth muscle gets thicker nearer to the uterus
                3. The isthmus –  narrowest part of the tube just lateral to the uterus
                4. The intramural part – pierces the lateral wall of the uterus

                 

                  Figure 4 The uterine tube

                  The functions of the uterine tubes are:

                  • Takes ovum to the uterus and acts as a conduit along which sperm travel to reach an ovum
                  • Provides the site of fertilisation (at the ampulla)
                  • Provides nourishment for the fertilised ovum and the sperm

                  Arterial supply

                  • Uterine artery  - a branch of the internal iliac artery
                  • Ovarian artery – a branch of the abdominal artery

                   

                  Venous drainage

                  • Ovarian veins – drains the pampiniform plexus and the right one drains into the inferior vena cava directly and the left one drains into the left renal vein which in turn drains into the inferior vena cava

                   

                  Innervation

                  Autonomic – via ovarian plexus and uterine plexus

                  Visceral afferents – follow the sympathetic fibres to T11- L1 level of the spinal cord sensory ganglia

                   

                  Histology

                  The tubes are lined by ciliated columnar epithelium cells which help to propel ovum down the tube. There are scattered mucin secreting cells within the epithelial layer that provide nutrients for the sperm and pre-embryo. Smooth muscle lines the mucosa and provides the forces to push ovum down the tubes. Peg cells also exist and provide fluid to provide nutrition and complete the capacitation of the sperm.The outer surfaces of the tubes are lined by visceral peritoneum.

                   

                  Figure 3 Different parts of the ovary

                  Uterus

                  This is a small organ weighing 30-40g and its most common position is described as being anterverted – this means that it is bending forwards over the urinary bladder. In some women it may be retroverted which means that it bends backwards towards the sacrum instead. This is generally asymptomatic but may be a cause of dyspareunia.

                   

                  The relations of the uterus are:

                  Anteriorly – vesicouterine pouch and the urinary bladder

                  Posteriorly – the rectouterine pouch and the anterior surface of rectum

                  Laterally – the broad ligament

                   

                  Suspensory ligaments

                  There are three extra pairs of ligaments in addition to the broad ligament that stabilise the position of the uterus:

                   

                  • The uterosacral ligament – from the lateral surface of the ligament to the anterior surface of sacrum. These prevent the uterus from being displaced inferiorly and anteriorly.

                   

                  • The round ligaments – lateral surface of uterus (just posterior to attachment point of uterine tubes) to connective tissue in the external genitalia. These restrict posterior movement of the uterus

                   

                  • The cardinal ligaments – from base of the uterus to the lateral wall of pelvis. These prevent inferior movement of the uterus.
                  Figure 5 Ligaments of the uterus

                   

                  Internal anatomy

                  The uterus can be divided into the body and the cervix.

                   

                  Body – the largest part and has a rounded superior portion known as the fundus and ends inferiorly at a constriction called the isthmus.

                   

                  Cervix - this is the inferior portion of the uterus that extends to the vagina. The internal aspect is known as the cervical canal which is a passageway that is bounded between the Internal Os and External Os.

                   

                  Figure 6 Internal anatomy of the uterus and the uterine wall

                   

                  Uterine wall

                  The wall of the uterus consists of:

                  • Endometrium – a thin glandular layer (mucosa) that is shed every month as part of the menstrual cycle
                  • Myometrium – thick smooth muscle layer that contracts when pushing a fetus out
                  • Perimetrium – outermost layer known as serosa which is covering the fundus and posterior surface of uterine body

                     

                    Arterial supply

                    • Uterine arteries – a branch of internal iliac artery
                    • Ovarian arteries – a branch of the abdominal aorta at the level of L1.

                    These are extensively interconnected to ensure a good blood supply

                     

                    Venous drainage

                    • Uterine veins – they are formed from the plexus and drain into internal iliac veins

                     

                    Innervation

                    Autonomic – Hypogastric plexus (sympathetic)                         S3-S4 (parasympathetic)

                    Visceral afferents – T11-T12

                     

                    Vagina

                    This is a muscular tube that extends from the cervix to the external genitalia. It opens into an area called the vestibule. The cervix extends slightly into the vaginal canal thus creating areas known as the fornix. The relations of the vagina are:

                    Anteriorly –the urethra open just anterior to at the urethral orifice

                    Posteriorly – The rectum lies parallel to it in close contact

                     

                    The vaginal walls contain layers of smooth muscle and a network of blood vessels. The vagina is separated from the vestibule by a thin epithelial sheet called the hymen which breaks, often during first sexual intercourse. There are two bulbospongiosus muscles that surround the masses of erectile tissue and can constrict.

                     

                    The layers of the vagina are:

                    • Non – keratinised squamous epithelium which forms folds called rugae and elastic lamina propria containing blood vessels and lymph nodes
                    • Circular and longitudinal smooth muscle layer
                    • Outer layer  - superiorly: serosa which is continuous with the peritoneum                       - inferiorly: adventitia which is a fibrous connective tissue

                     

                    Arterial supply

                    Uterine arteries supplies the superior portion – a branch of the internal iliac artery

                    Vaginal artery and internal pudendal arteries supply the middle and inferior parts – branches of the internal iliac artery

                     

                    Venous drainage

                    Uterovaginal plexus – drains into internal iliac veins

                     

                    Innervation

                    Autonomic – inferior hypogastric plexus, pelvic splanchnic, pudendal nerve (all provide parasympathetic Innervation from S2-S4)

                    Visceral afferents – accompany parasympathetic fibers of inferior hypogastric and  pelvic splanchnic nerves to S2-S4

                    Somatic afferents – accompany pudendal nerve to S2-S4

                     

                    External Genitalia

                    This area is known as the VULVA and consists of:

                     

                    • Vestibule – a central space where the vagina and urethra open into
                    • Labia minors – folds of smooth skin surrounding the vestibule
                    • Clitoris – this is the erectile tissue anterior to the urethral opening
                    • Prepuce – extensions of the labia minora that encircle the body of the clitoris
                    • Greater vestibular glands – ducts of these open into vestibule near the posterolateral margin of the vaginal opening secreting mucous during sexual intercourse
                    • Lesser vestibular glands – variable number of these secrete fluid to keep the vestibule moist
                    • Labia majora – prominent folds of skin that form the outer margin of the vulva laterally. They contain subcutaneous fat, hair and partially cove the labia minora
                    • Mons pubis – the bulge, containing adipose tissue and skin covered with hair, that forms the outer margin of the vulva superiorly

                     

                      Figure 7: The External Genitalia

                      References

                      Fundamentals of anatomy and physiology – Martini. F.H; Nath J.L, 8th edition

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