External structure and parts
Anatomically, the uterus is divided into several consecutive parts:
- Fundus (fundus uteri) — the upper convex part of the organ.
- Body (corpus uteri) — the main triangular part. The body gradually narrows downwards.
- Isthmus (isthmus uteri) — the narrow transition zone between the body and the inferior part.
- Cervix (cervix uteri) — the lower cylindrical part.
The body of the uterus has two surfaces. The anterior surface is called the vesical surface (facies vesicalis) as it faces the urinary bladder. The posterior surface is the intestinal surface (facies intestinalis), adjacent to the rectum. Laterally, these surfaces converge to form the right and left margins of the uterus (margines uteri). At the superior angles, where the uterine tubes enter the uterus, the so-called uterine horns (cornua uteri) are distinguished.
Uterine cavity and wall
The uterine cavity (cavitas uteri) has a triangular shape on a coronal section. The uterine tubes open into its superior angles, while inferiorly the cavity narrows and transitions into the internal os of the uterus, leading into the cervical canal.
The organ wall consists of three distinct layers:
- Endometrium (endometrium) — the inner mucous membrane.
- Myometrium (myometrium) — the thick middle muscular layer.
- Perimetrium (perimetrium) — the outer serous coat, which is a layer of the peritoneum.
Anatomy of the cervix
The cervix (cervix uteri) is about 3–4 cm long and topographically divided into two parts: the upper supravaginal part (portio supravaginalis) and the lower vaginal part (portio vaginalis).
The cervical canal (canalis cervicis uteri) runs inside the cervix. The mucous membrane of this canal forms characteristic palmate folds (plicae palmatae).
The canal opens into the vagina via the external os of the uterus (ostium uteri). The shape of this opening depends on obstetric history:
- In nulliparous women, it is round in shape.
- In women who have given birth, the external os takes on the appearance of a transverse slit.
Ligamentous apparatus and fixation
The normal position of the uterus in the pelvis is described by the terms anteversio (anterior tilt) and anteflexio (anterior flexion). The organ is securely fixed in the lesser pelvis due to a well-developed ligamentous apparatus.
The main ligaments include:
- Broad ligament of uterus (lig. latum uteri).
- Round ligament of uterus (lig. teres uteri).
- Ovarian ligament (lig. ovarii proprium).
- Suspensory ligament of ovary (lig. suspensorium ovarii).
In addition to ligaments, the parametrium (parametrium) — the perimetrial cellular tissue (parametrium) — plays an important role. Blood vessels and nerve plexuses supplying the organ pass through this fatty tissue.
Blood supply and innervation
Arterial blood supply is provided by two paired vessels:
- Uterine artery (a. uterina).
- Ovarian artery (a. ovarica).
Venous drainage originates from the uterine venous plexus (plexus venosus uterinus). Blood then flows out via the uterine veins (vv. uterinae) and ovarian veins (vv. ovaricae), heading into the internal iliac vein system (v. iliaca interna).
Innervation of the organ is provided by autonomic nerve plexuses: the inferior hypogastric plexus (plexus hypogastricus inferior) and the uterovaginal plexus (plexus uterovaginalis).
Briefly: answers to topical questions
Which ligaments form the fixing apparatus of the uterus?
The cited sources indicate that fixation of the uterus is ensured by the interaction of the suspensory, fixing, and supporting apparatuses. The exact composition of the uterine fixing apparatus is not specified in the sources.
To which regional lymph nodes does lymphatic drainage from the uterus occur?
Lymphatic drainage from the uterus occurs:
- from the lower part of the uterus — into the sacral, external iliac, and common iliac lymph nodes;
- partially — into the lower lumbar nodes along the abdominal aorta and into the superficial inguinal nodes;
- from the upper part of the uterus — laterally along the broad ligament of the uterus, then through the suspensory ligament of the ovary, along the course of the ovarian vessels into the lymph nodes along the lower abdominal aorta.
What pouches are formed by the peritoneum when transitioning from the uterus to adjacent organs?
When the peritoneum transitions from the uterus to adjacent organs, it forms the rectouterine pouch, also known as the pouch of Douglas. The common lymphatic plexus is located beneath the peritoneum of the rectouterine pouch.
The uterine layers are easy to remember by their Latin prefixes: PERImetrium — outside (periphery), MYOmetrium — in the middle (muscle), ENDOmetrium — inside.
Class and exam questions
Where is the uterus located in the pelvic cavity?
The uterus is located in the lesser pelvis: the urinary bladder is anterior to it, and the rectum is posterior.
What is the shape of the external os of the cervix?
In nulliparous women, the external os (ostium uteri) has a rounded shape, whereas in parous women it appears as a transverse slit.
What is the parametrium?
Parametrium (parametrium) is the perimetrial adipose tissue through which the vessels and nerves supplying the uterus run.
What else to study on this topic
- Features of the course and branching of the uterine artery
- Syntopy of the uterus with the urinary bladder and rectum
- Topography and formation of the broad ligament of the uterus
- Formation of lesser pelvis venous plexuses
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