Myometrial norms during pregnancy. Myometrial hypertonicity during pregnancy. Myometrial thickening during pregnancy. Hypertonicity of the muscular layer of the uterus (myometrium): what is it and why is it dangerous? Local myometrial tone

Pregnant women often experience ailments that can pose a threat to the health of the woman and baby. Myometrial hypertonicity is one of these critical conditions. Probably every second pregnant woman worries about the tone of the uterus. On later pregnancy, such a phenomenon is difficult to miss.

The always soft and round tummy suddenly suddenly becomes hard as a stone. In addition to anxiety, a “petrified” uterus gives a woman discomfort when moving. But much more woman I'm worried about the risk of miscarriage. How dangerous is this condition and why does it occur?

What is myometrial hypertonicity?

Myometrial hypertonicity is not a disease. This is a symptom in which the smooth muscles of the uterus - the myometrium - become very tense. Myometrial tension occurs regularly throughout a woman’s life in accordance with menstrual cycle. And she doesn't notice it. Contractions are natural for the uterus.

The uterus is a hollow muscular organ - a kind of sac. Under the influence of pregnancy hormones, the uterus becomes a safe haven for the developing embryo for 9 months and temporarily forgets about its usual activity - contractions. Hormones have a relaxing effect on her.

High contractile activity The uterus will be needed later, when the fetus is ripe. Intense contractions of the organ push the baby out, helping him to be born. Until this point, uterine contractions can be dangerous for the fetus. Therefore, tense myometrium is an alarming sign during pregnancy.

Return to contents

Why is myometrial hypertonicity dangerous?

Contraction of the uterine muscles in the first trimester of pregnancy can lead to fetal death and miscarriage. At such an early stage, women do not feel contractions and do not consult a doctor on time. Myometrial hypertonicity can be detected by a doctor during examination or during an ultrasound examination.

In the second trimester, myometrial hypertonicity also increases the risk of spontaneous abortion. Frequently repeated uterine contractions can cause fetal hypoxia. Fetal hypoxia is a series of changes in the body of the fetus that are caused by a lack of oxygen. Chronic oxygen starvation does not allow the fetus to develop normally. Disturbances in its development may occur individual organs or systems.

Hypertonicity of the myometrium in the third trimester can provoke premature birth of a non-viable or premature baby. The consequence of myometrial hypertonicity at this stage can be isthmic-cervical insufficiency (ICI). With ICI, the isthmus and cervix cannot cope with the load of the constantly increasing weight of the child and opens prematurely, allowing the fetus to leave the uterus ahead of schedule. During contraction of the muscular organ, the pressure on the isthmus and cervix increases many times and the risk of premature birth increases.

In the second and third trimester, uterine contractions can lead to abruption of the placenta, the organ through which the fetus receives all the substances necessary for development. Detachment of the third part of the placenta can kill the fetus. However, the risk of placental abruption is high only if it is abnormally low.

Myometrial hypertonicity is harmless only at the very end of pregnancy. Contractions of the uterus before childbirth are training and do not threaten the health of the mother and baby.

Return to contents

Localization and symptoms of uterine hypertonicity

Uterine hypertonicity is divided according to the type of its localization into different areas organ: hypertonicity of the anterior wall, hypertonicity of the posterior wall and total hypertonicity.

Hypertonicity on the anterior wall of the uterus is a sign of pregnancy complications. A woman may experience pain in the lower abdomen or perineal area. A sign of uterine contraction is also frequent urination and bowel movements. If measures are not taken urgently, they may appear bloody issues.
Local hypertonicity of the posterior wall of the uterus may go unnoticed. Women often do not feel any unpleasant ailments with this localization. This condition can be determined by a doctor during examination or during an ultrasound examination. However, sometimes local hypertonicity along the posterior wall of the uterus causes a woman painful sensations in the lower abdomen or lumbar region, as well as a feeling of fullness. Similar condition signals pregnancy complications and the threat of premature termination of pregnancy.
Total hypertonicity covers the entire muscle organ. A pregnant woman identifies this condition by her “petrified” belly. It becomes like a round and hard ball. A woman may experience the same symptoms as with local hypertonicity. Only they can be expressed more clearly. The causes of myometrial hypertonicity can be different.

Return to contents

Causes of myometrial hypertonicity

If the uterus is in good shape during pregnancy, then the processes that regulate pregnancy are disrupted. The following factors can cause uterine tone:

Hormonal imbalance, for example, a lack of the pregnancy hormone progesterone.
Inflammatory diseases of the pelvic organs, endometriosis.
Previously transferred surgical operations on the uterus or caesarean section.
Pathologies of the development of the reproductive system.
Neoplasms in the uterus.
Excessive stretching of the uterine walls. For example, during multiple pregnancy.
Severe physical stress and injury.
Stress and depression.
Diseases not related to the female reproductive system.
With age, the likelihood of developing hypertension increases.
Intense gas formation and intestinal peristalsis can provoke contractions of the uterus.

Women who have undergone repeated induced or spontaneous abortions are also at risk. Smoking, alcohol abuse and chronic lack of sleep have a negative effect on pregnancy.

Return to contents

What to do in this case?

A pregnant woman should be wary of any unusual sensations. Especially if they look like menstrual symptoms. Nagging pain, distension, unusual position of the abdomen, discomfort during movements and any other signs that were not previously observed. Some pregnant women have slightly increased myometrial tone, and this is a normal condition for them. But if new sensations appear, it is better to consult a doctor. An urgent visit to the doctor or call an ambulance at home is necessary in cases of bleeding.

To alleviate the condition with moderate myometrial hypertonicity, a woman can perform a number of exercises before visiting a doctor. To do this, you need to get on all fours, arch your back and raise your head. After a minute, the back arches in the opposite direction, and the head drops. The suspended state of the uterus will help it relax. After repeating the exercises several times, you need to sit in a comfortable chair, relax and calm down as much as possible. You can drink a cup herbal tea with a decoction of mint or lemon balm, adding a little honey. Calm music and a warm (not hot) bath will help you relax. You can add a decoction of mint or lemon balm to the water.

As a preventive measure, from the second half of pregnancy it is recommended to wear a bandage and include in the diet more foods rich in B vitamins and magnesium. Consumption of products that cause increased gas formation and intestinal peristalsis should be avoided. In the morning and evening, it is useful to stroke the abdomen in a circular, calm motion. To do this, it is better to be in bed in a relaxed, calm state.

A woman’s uterus is a hollow muscular organ that serves as a receptacle for the fetus during gestation. The walls of the uterus consist of several layers, one of which is the myometrium, the function of which is to nourish, protect, and, in the last stages of pregnancy, expel the fetus. For normal pregnancy, the muscular layer of the uterus must be relaxed. Hypertonicity of the myometrium along the posterior wall is a direct sign of a threatened miscarriage.

Why can this pathology develop?

There are a number of factors that increase the tone of the uterus. With successful determination of the etiological reason for which the myometrial tone is increased, it is possible to develop the most effective technique and its treatment strategy. The most common reasons include the following factors:

In the first trimester of pregnancy, that is, in the first three months, increased tone myometrium may be due to a decrease in the production of progesterone by the corpus luteum, and then the condition is called deficiency corpus luteum. Considering the fact that progesterone reduces the contractility of the myometrium and its sensitivity to estrogen, accordingly, when it is sufficiently present in the blood of a pregnant woman, the myometrial fibers remain relaxed. If there is a deficiency of progesterone, then the uterus becomes toned, and in such cases spontaneous miscarriage cannot be ruled out.
Hypertonicity also occurs with uterine fibroids. Uterine fibroids are benign tumor, arising in muscle layer uterus and consisting of rounded nodes. Uterine fibroids are still considered a hormone-dependent tumor, and if it is present, an imbalance of estrogen and progesterone with a shift towards increasing estrogen content is necessarily diagnosed in parallel.
Local hypertonicity of the myometrium is often observed in endometriosis, when the growth of endometrial cells in localized areas changes the very structure of the endometrial muscle fibers and leads it to a state of hypertonicity. This occurs against the background of endometrial growth in uncharacteristic places.
In case of any inflammatory processes in the uterus that were experienced before pregnancy and detected during pregnancy, the area of the myometrium with a disturbed structure is rendered incapable of stretching. It is this fact that leads to the fact that the myometrial tone becomes increased.
Another one important reason the occurrence of the pathology under discussion is adnexitis. Inflammation of the ovaries leads to significant hormonal deficiency. This is a trigger for the development of a condition in which myometrial tone is increased.
Neurogenic mechanisms of development of uterine hypertonicity. In addition to the reasons listed above, myometrial tone may be increased due to dysregulation at the level of the central nervous system. Failure of the hypothalamic-pituitary axis, for example, leads to excess production of prostaglandins. And they, in turn, provoke the release of excess estrogen into the woman’s bloodstream. Which ultimately leads to the development of hypertonicity.

Typical conditions and symptoms of increased uterine tone

According to localization, hypertonicity can be in the following areas of the uterus:

Hypertonicity along the posterior wall of the uterus is accompanied, in addition to nagging pain in the lower abdomen, pain in the lower back. With prolonged pain, bleeding may occur. This condition can lead to miscarriage.
Hypertonicity of the myometrium of the anterior wall is also accompanied by pain in the lower abdomen. But in this case there is tension, the stomach becomes like “stone”. If this condition occurs later in pregnancy, fetal movements may slow down. This condition is also threatening for miscarriage.

Large veins also pass along the posterior wall of the uterus. blood vessels, which nourish the fetus. When the myometrium is tense, they become compressed, and fetal hypoxia begins to develop.

Often, hypertonicity along the anterior wall can occur due to external irritation of the uterus, for example, during ultrasound. Sometimes this occurs with other effects on the anterior abdominal wall.

More about women's diseases explained in the video:

Treatment and prevention of increased uterine tone

It is important to understand that any pain or other manifestations of discomfort during pregnancy cannot be ignored. Anyone unnoticed alarm signal may cause an irreparable tragedy. The pregnant woman herself and the relatives around her are simply obliged to create a favorable environment for the expectant mother.

Adequate sleep, avoidance of psycho-emotional overload, a ban on heavy lifting, nutritious nutrition rich in vitamins - this is a small list of conditions for the birth of a healthy and full-fledged child. Increased local myometrial tone and its diffuse distribution always refer to emergency conditions requiring medical intervention. To prevent spontaneous abortion that has begun early stages or a miscarriage at a later stage, it is necessary to prevent the onset of conditions that can provoke an increase in uterine tension. It should always be remembered that it is impossible to stop a spontaneous abortion that has begun. You can only accept everything possible measures for its prevention and prevention.

For emergency relief of this condition at home, you can take the drug No-shpa, which relieves spasms of the smooth muscles of the uterus. It is also recommended that immediately if symptoms of increasing uterine tone are detected, lie down on the bed and do not get up until the doctor arrives or the ambulance arrives. medical care.

Having understood and realized what hypertonicity is, you can prevent its onset or stop the total spasm of the uterine muscles that has already begun. And, thereby, maintain the pregnancy and give birth to a healthy and strong baby.

The increase in myometrial tone is quite serious pathological condition uterus, which brings many problems and requires monitoring by a gynecologist. It manifests itself with symptoms, the nature of which suggests the presence of a disease. This is expressed dull ache in the pelvic area and discharge streaked with blood.

Often changes in the state of myometrial tone in the uterus are a signal of developing diseases in the body of a pregnant woman. This may be a sign infectious process, tumors or other diseases, infectious nature or acquired through sexual contact. Inferior development or infantility of the uterus can lead to serious problems, and in special cases cause termination of pregnancy or miscarriage.

In some cases, the reason for increased tone is a banal violation the right image life, consisting in lack of sleep, poor nutrition with insufficient essential vitamins. Excessive physical activity uncomfortable shoes on the heel, also brings the uterine myometrium into an excited state. IN similar situations You will have to give up your usual way of life and be more attentive to your well-being.

The condition of the uterus depends on the tension of the myometrium and is expressed as:

hypotonicity - a pathological condition indicating increased relaxation of the muscle layer, which manifests itself during the first hours after birth as pain in the lower abdomen and uterine bleeding, occurring due to a disturbance in the contraction of the uterine vessels;
normotonus - a normal condition in which the myometrium is in accordance with the norm;
Myometrial hypertonicity or increased tone is evidence of tension in the uterine muscles; it can be constant (with uterine fibroids) and lead to the threat of miscarriage during pregnancy, or periodic, occurring during contractions during childbirth.

Hypertonicity can be locally expressed or with total manifestations that involve the entire uterus.

Causes of myometrial hypertonicity

It is necessary to understand that increased tone, or hypertonicity, of the myometrium is not always an indicator of a pathological condition in the body of a pregnant woman and leads to termination of pregnancy. To prevent the possibility of complications and save the child, the expectant mother must follow the recommendations that are necessary to stabilize the situation. Thanks to measures taken possible risk is reduced to a minimum, and the myometrium returns to its normal state.

Hypotomus, unlike hypertonicity, does not pose a great danger to pregnancy and does not have a harmful effect on the development of the child. However, during labor it can cause complications and lead to protracted labor And caesarean section. A decrease in myometrial tone will require close monitoring by a doctor of the condition of the uterus before childbirth in a hospital setting.

Myometrial hypertonicity is one of the most important indicators affecting reproductive function body. The readiness of the uterus to accept an embryo and preserve and develop the fetus until a favorable resolution depends on these parameters.

There are many reasons that cause uterine hypertonicity during pregnancy. This infectious diseases, endocrine disorders, fibroids, birth defects and others. Hypertonicity of the posterior wall of the myometrium can occur with multiple pregnancies, physical exertion, and stress. Increased tone is observed during ultrasound, and this normal reaction uterus on external changes. Fetal movements can also cause the posterior wall to become more agitated. It is possible to reduce some state of increased tone and prevent further tension, but some changes do not depend on us and we have to put up with their presence.

Symptoms of changes in tone

Increased tone is expressed in tension in the muscles of the uterus - the myometrium. When the uterus is tense, a feeling of slight pain appears in the area of the anterior wall of the uterus, especially in the first weeks of pregnancy. Over time, the growth of the uterus leads to localization of tension, the pain disappears, and in the last weeks the tension can be felt in the very bottom of the uterus.
Bloody discharge of a brownish or pinkish color should be alarming, which indicates that the uterus is under increased tension and the possibility of fetal loss.
Increased tension may lead to structural changes uterus resulting from tumors in its walls, such as fibroids, polyps, adenomyotic nodes. They interfere with the normal development of the embryo and do not allow the walls to stretch as the fetus grows during pregnancy, which also causes hypertonicity.

Hormonal fluctuations and increased level estrogen causes stimulation of the walls of the uterus and maintenance of a state of hypertonicity in them. In a state of pregnancy must be observed hormonal balance, which is the ratio of two important hormones - estrogen and progesterone. Almost the entire period, the level of estrogen in a pregnant woman is reduced, and progesterone is increased, which creates favorable conditions for fetal development. Violation of this relationship leads to uterine bleeding and termination of pregnancy. Before childbirth, this position is reversed.

Important! Estrogen regulates the elasticity and tone of the uterus, as well as the possibility of its contraction. Without this hormone, successful gestation and full labor are impossible.

What to do?

Treatment of hypertonicity is carried out in extreme cases, when examination reveals symptoms characterizing possible interruption pregnancy. This may be pain in various parts body, in the stomach, in lumbar region, the presence of unusual discharge mixed with blood or discolored. If these signs appear, the pregnant woman should immediately contact medical institution. To maintain pregnancy, the gynecologist places the patient in stationary conditions. Treatment at home in these cases is unacceptable. If there are signs of moderate hypertonicity, in which myometrial tension is not observed constantly, but in periods, it may be sufficient outpatient treatment. To achieve success, it is necessary first of all to identify the cause of the pathology that has arisen, and based on it, prescribe the necessary medications.

– a pathological condition accompanied by increased contractility of the myometrium, which appears before the established date of birth. Among clinical signs there is visible tension in the anterior abdominal wall, nagging pain lower abdomen. To diagnose uterine hypertonicity, an objective examination of the woman and an ultrasound scan are used. Additionally, blood tests may be performed to determine hormones. Treatment consists of ensuring complete rest, prescribing sedatives, antispasmodics, vitamin therapy.

General information

Uterine hypertonicity is increased excitability of the smooth muscles of the uterus, provoked by hormonal changes or negative factors of a psychophysiological nature. This condition is more often diagnosed in women under 18 and over 30 years of age. In the first case, uterine hypertonicity is caused by underdevelopment of the genital area and the organ’s unpreparedness for bearing a fetus. As for patients over 30 years of age, hyperexcitability usually develops against the background of frequent abortions, past infections and other obstetric and gynecological pathologies. Hypertonicity of the uterus poses a real threat to the life and health of the baby, as it can provoke not only hypoxia, but also miscarriage, premature birth, and fetal death.

Causes of uterine hypertonicity

In most cases, uterine hypertonicity develops against the background of decreased production of progesterone, a hormone that ensures the normal course of pregnancy. Under its influence, there is a decrease in the contractility of the myometrium, the excitability of the uterine receptors and spinal cord, which together allows you to carry the fetus to 38-40 weeks and give birth healthy child. Progesterone deficiency with uterine hypertonicity manifests itself in the form of spontaneous miscarriages, fetal hypoxia, miscarriage or premature birth. Therefore, in treatment, the main goal should be to influence these etiological links of the pathological condition.

Uterine hypertonicity often develops when a woman has hyperandrogenism, a condition in which there is an increased production of male sex hormones. This diagnosis is also possible with genital infantilism. In this case, the underdeveloped uterus may respond with increased hyperexcitability in response to excessive enlargement. Hyperprolactinemia is also common reason hypertonicity of the uterus. The condition is accompanied by increased production of prolactin, which blocks the production of progesterone and leads to increased contractility of smooth muscles.

Often, uterine hypertonicity is caused by hormone-dependent diseases that the woman suffered from even before conception. Among them are fibroids and endometriosis. Previously transferred inflammatory processes, spreading to the uterine cavity and appendages, also increase the likelihood of developing increased excitability of the myometrium. Hypertonicity of the uterus can be caused by dysregulation of the central nervous system, which manifests itself in increased contractility and the inability to maintain optimal muscle tone. Women with multiple pregnancies, polyhydramnios, and the presence of a large fetus are more susceptible to this pathology. These factors contribute to excessive overstretching of the myometrium.

The risk group for the development of uterine hypertonicity includes patients with genetic abnormalities, diseases thyroid gland, suffered viral infections in the early stages of pregnancy. When the expectant mother’s body is exposed to negative factors (harmful working conditions, lack of sleep, daily work), the likelihood of this condition also increases. Often, uterine hypertonicity is caused by psycho-emotional experiences, stress, bad habits. Therefore, such factors must be excluded from the patient’s life.

Symptoms of uterine hypertonicity

Depending on which part of the myometrium is tense, in obstetrics there are 1 and 2 degrees of uterine hypertonicity. In the first case, there is a contraction of only the posterior wall of the organ, which most often is not accompanied by pathological manifestations. In the third trimester of pregnancy, uterine hypertonicity of the 1st degree can manifest itself as minor nagging pain in the lower back, a feeling of heaviness in the sacral area. There are usually no other symptoms.

Hypertonicity of the uterus of the 2nd degree implies tension of the myometrium of the anterior wall of the organ and is accompanied by a more pronounced clinical picture. The main symptom is nagging pain in the lower abdomen, similar to those that occur in women during the premenstrual period. Often, with hypertonicity of the uterus, pain spreads to the perineum, and a feeling of fullness in the external genitalia may be observed. In this case, there is an increase in urination and contraction of the muscle fibers of the rectum, similar to the urge to defecate.

Visually, with hypertonicity of the uterus, the abdomen becomes dense, rises slightly, and takes on a more rounded shape than usual. The tension of the myometrium can be determined through the anterior abdominal wall by palpation. As for the lower segment of the genital organ, that is, the cervix, when the uterus is hypertonic, its contraction is usually not observed, although such a symptom is sometimes present if the woman has previously had injuries cervical canal, for example, during previous births.

Diagnosis of uterine hypertonicity

Hypertonicity of the uterus – alarming symptom in obstetrics, which may indicate the possible likelihood of spontaneous abortion or premature birth. Therefore from timely diagnosis and the treatment provided depends on the health and life of the fetus. An obstetrician-gynecologist can identify uterine hypertonicity using a routine objective examination of a woman, which is carried out at every appointment. When palpating the abdomen, tension in the myometrium will be felt; the intensity of this symptom can vary - up to a feeling of “petrification”. In this case, patients often report discomfort and even pain.

As additional method Diagnosis of uterine hypertonicity is used ultrasound scanning. By using this study it is possible to determine local or total contraction of the myometrium. With 1 degree of hypertonicity, thickening of the muscular layer of the uterus on one side is observed. If such a sign is detected in the area of placenta attachment, then there is a high probability of its detachment. With uterine hypertonicity of the 2nd degree, the entire myometrium is thickened, there are corresponding clinical symptoms. Also, to determine contractility, tonuometry can be performed - measuring the tone of the uterus using a special sensor, which is placed on the anterior abdominal wall and records the level of tension in the muscle layer.

Treatment of uterine hypertonicity

If there is hypertonicity of the uterus, a pregnant woman should first of all provide bed rest. It is necessary to eliminate any negative factors (physical activity, stress) that may cause aggravation of the pathological condition. If excessive myometrial contractility is not accompanied severe symptoms, treatment can be carried out in outpatient setting. Hospitalization of a woman is indicated for grade 2 uterine hypertonicity, especially if spotting and bleeding from the vagina is observed. This symptom may indicate early abortion, premature birth, or placental abruption in the 2nd-3rd trimester.

Drug treatment of uterine hypertonicity depends on the etiology of the pathological condition. If there is a lack of progesterone production, progesterone drugs are prescribed. If uterine hypertonicity has developed against the background of magnesium deficiency, the patient is advised to take tablets based on this microelement or injections of magnesium sulfate in the case of medical care in a hospital setting. Under the influence of this component, the contractility of the myometrium decreases and the transmission of nerve impulses normalizes.

Antispasmodics are prescribed as symptomatic therapy for uterine hypertonicity. They reduce the contractility of the myometrium and eliminate pain. The use of sedatives is also indicated. For uterine hypertonicity, drugs are mainly used plant origin. Additionally apply vitamin complexes. Until the 34th week of pregnancy, tocolytics are prescribed, which reduce myometrial contractions and suppress the onset of labor. With this diagnosis, specialists always try to prolong the pregnancy as much as possible and carry the fetus to 38 weeks.

Forecast and prevention of uterine hypertonicity

In most cases, the prognosis for uterine hypertonicity is favorable. With timely medical care, it is possible to suppress the increased excitability of the myometrium and prolong gestation until the expected date of birth. With the progression of uterine hypertonicity, the possibility of giving birth to a viable baby appears only at 25-28 weeks. At earlier stages, the fetus simply will not be able to survive in environmental conditions.

Prevention of uterine hypertonicity should begin when planning conception. It is important to promptly detect and treat sexually transmitted infections and diseases of hormonal etiology. After pregnancy, preventing uterine hypertonicity involves reducing physical activity, proper organization work and rest regime. You should also completely eliminate emotional experiences and stress. If even minimal signs of uterine hypertonicity are observed, you should immediately seek medical help.

Uterine hypertonicity means increased muscle tone of the uterus before labor begins. In the article we will look at next questions: what is the danger of hypertonicity, how to determine the pathological condition, for what reasons does the pathology develop, what to do with uterine hypertonicity. So, about everything in more detail.

Why is increased uterine tone dangerous during pregnancy?

Options for the development of the situation depend on the gestation period. But in any case, hypertonicity is dangerous at any stage through termination of pregnancy. So in the early stages, uterine tone prevents the fetus from becoming well established in the endometrium, then, when the placenta has formed, there is a risk of its detachment. In addition, hypertonicity of the uterus during pregnancy puts pressure on the blood vessels that connect mother and child, causing the child to lack oxygen and nutrients, for normal development. Especially often, the pathological condition develops precisely in the early stages of pregnancy, and this is a threat to pregnancy. In addition, hypertension is often increased in late pregnant women. Then it may be confused with training contractions.

Symptoms of hypertension in pregnant women are as follows::

Pain in the lower abdomen, as during menstruation, or radiating to the lumbar region.
In the second trimester, there is a feeling of tension, constant excitement of the uterus.
The uterus is hard, the pregnant woman’s belly moves and can change shape.

However, these signs may not appear. Sometimes doctors determine this pathological condition during an ultrasound examination. It must be said that in both cases the tone can be provoked emotional state pregnant woman before ultrasound.

Due to the high risks for the fetus, additional medications are required. research in order to accurately establish the pathology and find out its cause.

Separately, it should be said about local uterine hypertonicity along the posterior or anterior wall. By the way, the development of the pathology depends on the location of the pathology. pain syndrome only in the stomach or in lumbar region. On ultrasound examination video pathology based on an obvious change in the shape of the organ: one of its walls bends into the inner part.