fertility basics

Anatomy of Uterus, Functions and Uterine Conditions in Women and Pregnancy

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The uterus is an 8 cm long hollow muscular organ in the female pelvis. It consists of several anatomical parts like the cervix, isthmus, and body. The reproductive function of a uterus is to accept a fertilized ovum that passes through the utero-tubal junction from the fallopian tube.

The uterus (womb) as an organ of the female reproductive system is responsible for the development of the embryo and fetus during pregnancy. It is located above the vagina, between the bladder and rectum. It is about 8 cm long and 5 cm across at the widest point. It is held in place within the pelvis by several ligaments. The reproductive system of the female is made up of internal organs, including the uterus, vagina, ovaries and fallopian tubes. The reproductive system also includes the external genital organs the parts that make up the vulva. All the internal organs are in the pelvis, which is between the hipbones and below the abdomen. (1)

In this article, we will look at:

  1. What is the anatomy of the uterus?
  2. What is the role of uterus in blood supply and innervation?
  3. What is the histology of the uterus?
  4. What is the function of uterus in women and pregnancy?
  5. What are various Uterine Conditions in Women?

1. What Is the Anatomy of the Uterus?

Parts & Position

The uterus is divided into three parts the cervix, isthmus and corpus.

  • The cervix or neck of the uterus is the lower, narrow part of the uterus that joins to the top of the vagina. The opening of the cervix is called the os, which allows menstrual blood to flow out from the vagina during menstruation. During pregnancy, the cervical os or cervical osteophytes close to help keep the fetus inside the womb until birth. During labor, the cervix dilates and widens to allow the baby to move from the uterus to the vagina. Approximately half the length of the cervix is visible with appropriate medical equipment during a cervical screening (smear test) using a speculum. The rest of the cervix is called the endocervical canal that is the narrow passageway that runs up from the cervix into the womb and it cannot be seen during cervical screening. The cervical canal has two orifices: the external orifice to the vagina and the internal orifice to the isthmus. (2)
  • The isthmus is the inferior-posterior part of the uterus and morphologically defined as a topographic zone between the uterine corpus and the cervix, in very close association with the vaso-musculary inferences. The isthmus coincides to the connective muscular function, which is different by its thickness from 2 mm-10 mm and by its morphology (undulating sharp and regular). Histologically isthmus is made up of collagen fibers myometrial muscle cells, irregularly directed. The relationship of these two components reveals their functional synergy between the weakners of the muscle cells and the predominance of the connective tissue. The specific function of the isthmus and its autonomy depends on the type, direction of the collagen fibers, the quantity and arrangement of the muscle cells, of the biochemical modifications and the variability of the ground substance moreover of the relations with the nervo-vascular endings. The isthmus incontinence is associated with these structural anomalies muscular components, elastic fibers defects, connective tissue pathology, activity of the nerve endings and enzymatic troubles under hormonal control. (3)
  • The corpus is the main body of the uterus and lies Intraperitoneally. The corpus has a triangle lumen through its connection to the isthmus and both fallopian tubes. The base of the uterus is called fundus. The corpus is very muscular and can stretch to accommodate a developing fetus. During labor, the muscular walls of the corpus contract and expand to help push the baby through the cervix and vagina.

In most of the women, the corpus is bent forward against the cervix at the isthmus (anteflexion) and the long axis of the uterus is inclined towards the vagina (anteversion). The shape and size of the corpus, however, may vary depending on the number of pregnancies, age and hormonal status. The uterus is surrounded by the circumjacent connective tissue known as parametrium. The serous membrane, which forms the lining of the abdominal cavity, is known as Peritoneum. It covers the uterus completely except the ventral part of the cervix forming two recesses - dorsally the rectouterine pouch also known as pouch of Douglas and ventrally the Vesicouterine pouch. (4)

2. What Is the Role of Uterus in Blood Supply and Innervation?

The uterus is supplied by arterial blood both from the ovarian artery and the uterine artery. Another anastomotic branch may also supply the uterus from anastomosis of both these arteries. The venous blood is drained through the uterine venous plexus into the internal iliac vein. The nerves derive from the inferior hypogastric plexus. All vessels and nerves run through the lateral ligaments - ligamentum latum uteri, a broad duplication of the peritoneum connecting the lateral wall of the uterus with the pelvic wall. (5)

3. What Is the Histology of the Uterus?

The uterus has three layers namely:

  1. Mucosa (endometrium),
  2. Muscularis (myometrium) and
  3. Serosa/adventitia (Perimetrium)

1. Mucosa (endometrium): The endometrium or uterine mucous membrane is lined with simple columnar epithelium (lamina epithelialis) and contains numerous tubular glands. A cell-rich connective tissue layer - called Lamina Propria, follows it. Physiologically the endometrium is divided into two layers: the functional layer (stratum functionale) and basal layer (stratum basale).

2. The myometrium (uterine musculature): The myometrium (uterine musculature) comprises a complex of three smooth muscle layers which are microscopically difficult to separate:

  • The subvascular layer is rather thin and mainly participates in the sealing of the tubes and the separation of the endometrium during the menstrual cycle.
  • The vascular layer is quite strong and well-perfused running around the uterus like a net. It plays a major role during labor.
  • The supravascular layer is again a thin sheet of crossing muscle fibers stabilizing the uterine wall. (6)

3. Serosa/adventitia (Perimetrium): The serosa of the uterus is called the perimetrium and is the outermost layer of the connective tissue which lines outside the organ. The serosa layer provides a partition between the internal organs and the abdominal cavity. The cells of serous layer secret a serous fluid, which provides lubrication to reduce friction. The three serous cavities within the human body are the pericardial cavity (surrounding the heart), the pleural cavity  (surrounding the lungs) and peritoneal cavity (surrounding most of the organs near the abdomen). The serous membrane covering the heart is a double layer consisting of an inner layer or parietal pericardium and an outer layer or visceral pericardium. (7)

4. What Is the Function of Uterus in Women and Pregnancy?

The uterus plays an important role in human reproduction system. It is the uterus where the implantation and nourishment of the fertilized ovum takes place. Furthermore, uterus helps in pushing out the baby during birth through muscle contraction. The uteruses of women in childbearing age underlie an about 28 day hormone-controlled rhythm (menstrual cycle) which goes through three phases:

  • During the menstrual phase from day 1 to 4, the spiral arteries in the endometrium contract leading to ischemia and sloughing of the functional layer (desquamation). Simultaneously, coagulation factors in the menstrual blood are decomposed in order to avoid blood clotting. This phase is predominantly controlled by estrogen causing painful contractions of the uterine musculature.
  • During the proliferative phase from day 5 to 14, the cells of the basal layer divide rapidly leading to a fast regeneration of the epithelium, functional layer and spiral arteries.
  • The secretory phase from day 15 to 28 begins with the ovulation stopping the proliferation and preparing implantation of the ovum. At the secretory phase, the uterine lumen dilates and intracellular accumulation of glycogen takes place. The glands resemble a saw-tooth-like shape and increasingly secrete nutrients. The endometrial stromal cells resemble the decidua of the placenta (predecidual cells). If no fertilization takes place during the secretory phase, the spiral arteries contract and the cycle begins again.

The reproductive function of the uterus is to accept a fertilized ovum that passes through the utero-tubal junction from the fallopian tube. After fertilization, the ovum divides to become a blastocyst and gets implanted into the endometrium. It derives nourishment from blood vessels, which develop exclusively for this purpose. The fertilized ovum develops into an embryo, attaches to a wall of the uterus, creates a placenta, and finally develops into a fetus (gestates) until childbirth. Due to anatomical barriers such as the pelvis, the uterus is pushed partially or contracts into the abdomen during pregnancy. Even during pregnancy, the mass of a human uterus amounts to only about a kilogram or 2.2 pounds. It also plays a significant role in sexual response, by directing blood flow to the pelvis and ovaries, and to the external genitals, including the vagina, labia, and clitoris. (8)

5. What Are Various Uterine Conditions in Women?

  • Endometriosis: Endometrial tissue lines the uterus. Each month, in tune with the menstrual cycle, the endometrial tissue thickens and is shed during menstruation. If a woman has endometriosis, it means that the same kind of tissue that lines her uterus is also growing in other parts of her body, usually in the abdomen. This can cause scar tissue to build up around her organs. Endometriosis may cause severe pain and abnormal bleeding, usually around the time of a woman’s period. Pain during intercourse is another common symptom. It is possible that a woman may have endometriosis and not have any symptoms. It is one of the leading cause of infertility (inability to get pregnant). Often it is not diagnosed until a woman has trouble getting pregnant and may lessen after menopause and during pregnancy since the growth of endometrial tissue depends on estrogen. If a woman has endometriosis and takes estrogen-replacement therapy after menopause, the tissue may grow back. (9)
  • Uterine fibroids: Uterine fibroids are noncancerous growths of the uterus that often develop during childbearing years. Also called leiomyomas or myomas, uterine fibroids are not associated with an increased risk of uterine cancer and almost never develop into cancer. Uterine fibroids range in size from seedlings, undetectable by the human eye, to bulky masses that can distort and enlarge the uterus. Many women have uterine fibroids sometime during their lives but most women do not realize they have uterine fibroids because they often cause no symptoms. Uterine fibroids can be detected during a pelvic exam or prenatal ultrasound. (10)
  • Abnormal Bleeding: The normal length of a woman’s menstrual cycle is between 24 days and 38 days. Bleeding is considered abnormal uterine bleeding in case of the following conditions: bleeding or spotting occurs between periods, bleeding or spotting after sex, heavy bleeding during period, menstrual cycles that are shorter than 24 days or longer than 38 days, irregular periods in which cycle length varies by more than 7 to 9 days and bleeding after menopause. (11)
  • Uterine prolapse: Uterine prolapse is caused when the tissues and muscles of the pelvic floor are weakened and cannot support the weight of the uterus. Advancing age and childbirth are commonly linked with this condition. Symptoms may include leakage of urine, inability to completely empty your bladder, feeling of heaviness or fullness in around the pelvis, bulging in the vagina, lower-back pain, aching or a feeling of pressure in the lower belly (abdomen) or pelvis, constipation, accidental leakage of stool or straining when moving the bowels, bleeding or discharge. (12)
  • Pelvic inflammatory disease (PID): Pelvic inflammatory disease (PID) is an infection of the uterus, fallopian tubes or ovaries. PID is the most common serious infection among young women, with approximately one million new cases diagnosed in the United States each year. About one in every seven women receives treatment for the pelvic inflammatory disease at some point in her life. PID infection can cause tissue inside the fallopian tubes to become scarred, which can damage the fallopian tubes or block them completely. The more often a woman gets PID infection, the greater her risk of becoming infertile. (13)
  • Uterine cancers: Uterine cancers are of two types: endometrial cancer (common) and uterine sarcoma (rare). Endometrial cancer can often be cured while uterine sarcoma is often more aggressive and harder to treat. (14) Majority of women diagnosed with endometrial cancer are postmenopausal, more than half of cases occur in women between the age of 50 to 69. Younger women known to develop the condition tend to be obese or have a genetic predisposition. Unlike ovarian cancer, endometrial cancer has a major, identifiable symptom in its early stages like abnormal vaginal bleeding or postmenopausal bleeding. Other symptoms include a pelvic mass, pelvic pressure, abnormal discharge that does not look like blood, difficulty and pain during urination and pain during intercourse. The greatest risk factors for developing endometrial cancer are obesity and abnormal precancerous changes in the uterus. (15)

The article has covered detailed information about the functions of uterus. Learn more about medical treatments by following OVO Fertility Blog today. Avail the best IVF treatment in India at an affordable cost. Call OVO Fertility and find out if you are eligible for medical loans at 0 percent interest rate. Reach us at +918268260808.

 

SOURCES AND REFERENCES:

  1. ^ Secondary Sex Organ of the Reproductive System in Humans - Wiki Pedia En.wikipedia.org, 29 March 2019
  2. ^ Adenocarcinoma of the Cervix - Jos Trust Jostrust.org.uk, 29 March 2019
  3. ^ Histophysiology of the Uterine Isthmus - NCBI Ncbi.nlm.nih.gov, 29 March 2019
  4. ^ Histology of the Uterus - Kenhub Kenhub.com, 29 March 2019
  5. ^ Secondary Sex Organ of the Reproductive System in Humans - Wiki Pedia En.wikipedia.org, 29 March 2019
  6. ^ Histology of the Uterus - Kenhub Kenhub.com, 29 March 2019
  7. ^ Structure of the Serosa - Oer 2 Go Oer2go.org, 29 March 2019
  8. ^ Anatomy of the Uterus - Kenhub Kenhub.com, 29 March 2019
  9. ^ Common Uterine Conditions - Archive Archive.ahrq.gov, 29 March 2019
  10. ^ Common Symptoms of Uterine Fibroids - Mayo Clinic Mayoclinic.org, 29 March 2019
  11. ^ When Is Bleeding Abnormal - ACOG Acog.org, 29 March 2019
  12. ^ What Is Uterine Prolapse - Cedars Cedars-sinai.org, 29 March 2019
  13. ^ Pelvic Inflammatory Disease - Harvard Health.harvard.edu, 29 March 2019
  14. ^ Uterine Cancers Can Be of Two Types - Cancer Cancer.gov, 29 March 2019
  15. ^ Diseases & Conditions Uterine Cancer - Healthy Women Healthywomen.org, 29 March 2019
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5 Comments

Vikram Bhanu

We take uterus as one which can only conceive and deliver but it is lot more than we could think off. Thanks for sharing this knowledge.

Sept. 30, 2018, 8:33 p.m. 5.0

Shewta Valik

Every time I have sex, I feel abdominal pain, itchiness around my cervix and odorful vaginal discharge. Is this normal or should I visit a gynecologist?

Sept. 9, 2018, 1:37 p.m. 4.5

Shahid Ahmed

Women with a weak uterus or small sized uterus have infertility.

Aug. 12, 2018, 4:40 p.m. 5.0

Kaustubh Muniyappa

Never knew my uterus did so much.

Jan. 24, 2018, 5:29 p.m. 4.5

Lohitaksha Saripella

Are functions of uterus disrupted in anyway with the change in size alone?

Jan. 22, 2018, 7:45 p.m. 4.5

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