SMALL pelvis.

LARGE pelvis

The large pelvis is much wider than the small one. Limited:

From the sides with the wings of the ilium,

Behind - the last lumbar vertebrae,

Anteriorly, the lower part of the abdominal wall.

The small pelvis is the bony part of the birth canal.

The back wall of the small pelvis consists of:

sacrum and coccyx,

The lateral ones are formed by the ischial bones,

anterior - pubic bones and symphysis

Parts of the small pelvis:

Cavity

In the pelvic cavity, a wide and narrow part is distinguished.

In accordance with this, four planes of the small pelvis are considered:

I - the plane of the entrance to the pelvis,

II - the plane of the wide part of the pelvic cavity,

III - the plane of the narrow part of the pelvic cavity,

IV - the plane of the exit of the pelvis.

I. The plane of the entrance to the small pelvis has the following boundaries:

In front - the upper edge of the symphysis and the upper inner edge of the pubic bones,

From the sides - nameless lines,

Behind - the sacral cape.

The entrance plane has the shape of a kidney or a transverse oval with a notch corresponding to the sacral promontory.

Three sizes are distinguished at the entrance to the pelvis:

Transverse,

Two oblique.

Straight size- the distance from the sacral cape to the most prominent point on the inner surface of the pubic joint. This size is called obstetric, or true conjugate(conjugata vera). There is also an anatomical conjugate - the distance from the cape to the middle of the upper inner edge of the symphysis; the anatomical conjugate is slightly (0.3-0.5 cm) larger than the obstetric conjugate. Obstetric, or true conjugate is 11 cm.

Transverse dimension- the distance between the most distant points of the nameless lines. This size is 13-13.5 cm.

oblique dimensions: right and left, which are equal to 12-12.5 cm.

Right oblique size - the distance from the right sacroiliac joint to the left iliac-pubic tubercle,

Left oblique size - from the left sacroiliac joint to the right iliac-pubic tubercle.

II. The plane of the wide part of the pelvic cavity has the following boundaries:

in front - the middle of the inner surface of the symphysis,

on the sides - the middle of the acetabulum,

behind - the junction of the II and III sacral vertebrae.

In the wide part of the pelvic cavity, two sizes are distinguished: straight and transverse.

Straight size - from the junction of II and III sacral vertebrae to the middle of the inner surface of the symphysis; equal to 12.5 cm.

Transverse size - between the tops of the acetabulum; equal to 12.5 cm.

There are no oblique dimensions in the wide part of the pelvic cavity because in this place the pelvis does not form a continuous bone ring. Oblique dimensions in the wide part of the pelvis are allowed conditionally (length 13 cm).

III. The plane of the narrow part of the pelvic cavity limited:

in front of the lower edge of the symphysis,

from the sides - the awns of the ischial bones,

behind - sacrococcygeal joint.

There are two sizes: straight and transverse.

Straight the size goes from the sacrococcygeal joint to the lower edge of the symphysis (apex of the pubic arch); equal to 11-11.5 cm.

Transverse the size connects the spine of the ischial bones; equal to 10.5 cm.

IV. Pelvic outlet plane has the following boundaries:

In front - the lower edge of the symphysis,

From the sides - ischial tubercles,

Behind - the tip of the coccyx.

In the outlet of the pelvis, two sizes are distinguished: straight and transverse.

Straight the size of the exit of the pelvis goes from the top of the coccyx to the lower edge of the symphysis; it is equal to 9.5 cm. When the fetus passes through the small pelvis, the coccyx departs by 1.5-2 cm and the direct size increases to 11.5 cm.

Transverse the size of the outlet of the pelvis connects the inner surfaces of the ischial tubercles; = 11 cm.

By puberty in a healthy woman, the pelvis should have a normal shape and size for a woman. For the formation of the correct pelvis, the normal development of the girl during the prenatal period, the prevention of rickets, good physical development and nutrition, natural ultraviolet radiation, injury prevention, normal hormonal and metabolic processes are necessary.

The pelvis (pelvis) consists of two pelvic, or nameless, bones, the sacrum (os sacrum) and the coccyx (os coccygis). Each pelvic bone consists of three fused bones: the ilium (os ilium), the ischium (os ischii) and the pubis (ospubis). The bones of the pelvis are connected in front by the symphysis. This inactive joint is a semi-joint in which two pubic bones are connected using cartilage. The sacroiliac joints (almost immobile) connect the lateral surfaces of the sacrum and the ilium. The sacrococcygeal junction is a mobile joint in women. The protruding part of the sacrum is called the cape (promontorium).

Measuring the size of the pelvis.

To assess the capacity of the pelvis, 3 external dimensions of the pelvis and the distance between the femurs are measured. The measurement of the pelvis is called pelvimetry and is carried out using a pelvisometer.

External dimensions of the pelvis:

1. Distancia spinarum - interspinous distance - the distance between the anterior superior iliac spines (spine - spina), in a normal pelvis is 25-26 cm.
2. Distancia cristarum - intercrest distance - the distance between the most distant points of the iliac crests (crest - crista), normally equals 28-29 cm.
3. Distancia trochanterica - intertuberous distance - the distance between the large tubercles of the trochanters of the femur (large tubercle - trochanter major), normally equals 31 cm.
4. Conjugata externa - external conjugate - the distance between the middle of the upper edge of the symphysis and the supra-sacral fossa (depression between the spinous process of the V lumbar and I sacral vertebrae). Normally it is 20-21 cm.

When measuring the first three parameters, the woman lies in a horizontal position on her back with outstretched legs, the buttons of the tazomer are set on the edges of the size. When measuring the direct size of the wide part of the pelvic cavity. To better identify large skewers, a woman is asked to bring her toes together. When measuring the external conjugates, the woman is asked to turn her back to the midwife and flex her lower leg.

Rhombus Michaelis

- this is an expansion of a depression in the sacral region, the limits of which are: above - a fossa under the spinous process of the fifth lumbar vertebra (supracrural fossa), below - points corresponding to the posterior superior iliac spines. The average length of a rhombus is 11 cm, and the diameter is 10 cm.

Diagonal conjugate

- the distance from the lower edge of the symphysis to the most protruding point of the promontory of the sacral bone is determined during vaginal examination. With normal pelvic dimensions, it is 12.5-13 cm.

The size of the true conjugate (the direct size of the entrance to the small pelvis) is determined by subtracting 9 cm from the length of the outer conjugate or subtracting 1.5-2 cm from the length of the diagonal conjugate (depending on the Solovyov index).

Solovyov index

- the circumference of the wrist-carpal joint, divided by 10. The index allows you to have an idea of ​​\u200b\u200bthe thickness of a woman's bones. The thinner the bones (index = 1.4-1.6), the greater the capacity of the small pelvis. In these cases, 1.5 cm is subtracted from the diagonal conjugate and the length of the true conjugate is obtained. With a Solovyov index of 1.7-1.8, they subtract 2 cm.

Pelvic tilt angle

- the angle between the plane of entry into the small pelvis and the horizon is 55-60 °. Deviations in one direction or another can adversely affect the course of childbirth.

The height of the symphysis is normally 4 cm and is measured with the index finger during vaginal examination. The pubic angle - with normal pelvic dimensions is 90-100 °.

Small pelvis

is the bony part of the birth canal. The posterior wall of the small pelvis consists of the sacrum and the coccyx, the lateral ones are formed by the ischium, the anterior one is formed by the pubic bones and the symphysis. The small pelvis has the following sections: entrance, cavity and exit.

In the pelvic cavity, a wide and narrow part is distinguished. In this regard, four planes of the small pelvis are determined:

1 - the plane of the entrance to the small pelvis.

2 - the plane of the wide part of the pelvic cavity.

3 - the plane of the narrow part of the pelvic cavity.

4 - the plane of the exit from the pelvis.

The plane of the entrance to the small pelvis passes through the upper inner edge of the pubic arch, the innominate lines and the top of the promontory. In the plane of the entrance, the following dimensions are distinguished:

1. Direct size - the distance from the sacral protrusion to the point that protrudes most on the upper inner surface of the symphysis - this is an obstetric, or true conjugate, equal to 11 cm.
2. Transverse size - the distance between the distant points of the arcuate lines, which is 13-13.5 cm.
3. Two oblique dimensions - from the ilio-sacral junction on one side to the ilio-pubic tubercle on the opposite side of the pelvis. They are 12-12.5 cm.

The plane of the wide part of the cavity of the small pelvis passes through the middle of the inner surface of the pubic arch, on the sides through the middle of the acetabular cavities and behind - through the connection between the II and III sacral vertebrae.

In the plane of the wide part of the small pelvis, there are:

1. Direct size - from the middle of the inner surface of the pubic arch to the junction between II and III sacral vertebrae. It is equal to 12.5 cm.
2. The transverse dimension passes between the midpoints of the acetabulum. It is equal to 12.5 cm.

The plane of the narrow part through the lower edge of the pubic junction, on the sides - through the gluteal awns, behind - through the sacrococcygeal junction.

In the plane of the narrow part they distinguish:

1. Direct size - from the lower edge of the symphysis to the sacrococcygeal junction. It is equal to II, 5 cm.
2. The transverse dimension between the distant points of the inner surface of the ischial spines. It is equal to 10.5 cm.

The plane of exit from the small pelvis passes in front through the lower edge of the symphysis, from the sides - through the tops of the gluteal tubercles, from behind - through the crown of the coccyx.

In the plane of exit from the small pelvis, there are:

1. Direct size - from the top of the coccyx to the lower edge of the symphysis. It is equal to 9.5 cm, and when the fetus passes through the small pelvis, it increases by 1.5-2 cm due to the deviation of the tip of the coccyx of the presenting part of the fetus.
2. Transverse size - between the distant points of the inner surfaces of the ischial tuberosities; it is equal to 11cm.

The line connecting the midpoints of the direct dimensions of all planes of the pelvis is called the leading axis of the pelvis, and has the form of a forward concave line. It is along this line that the leading point passes through the birth canal.

SMALL PELVIS Planes and dimensions of the small pelvis. The small pelvis is the bony part of the birth canal. The posterior wall of the small pelvis consists of the sacrum and the coccyx, the lateral ones are formed by the ischial bones, the anterior - by the pubic bones and symphysis. The posterior wall of the small pelvis is 3 times longer than the anterior one. The upper part of the small pelvis is a solid, unyielding bone ring. In the lower part of the pelvic wall is not continuous; they have obturator openings and ischial notches, limited by two pairs of ligaments (sacrospinous and sacrotuberous). In the pelvis, there are the following departments: entrance, cavity and exit. In the pelvic cavity, a wide and narrow part is distinguished. In accordance with this, four planes of the small pelvis are considered: I - the plane of the entrance to the pelvis, II - the plane of the wide part of the cavity of the small pelvis, III - the plane of the narrow part of the pelvic cavity, IV - the plane of the exit of the pelvis.

I. The plane of the entrance to the small pelvis has the following boundaries: in front - the upper edge of the symphysis and the upper inner edge of the pubic bones, from the sides - nameless lines, behind - the sacral cape. The entrance plane has the shape of a kidney or a transverse oval with a notch corresponding to the sacral promontory. At the entrance to the pelvis, three sizes are distinguished: straight, transverse and two oblique. Direct size - the distance from the sacral cape to the most prominent point on the inner surface of the pubic joint. This size is called obstetric, or true, conjugate (conjugata vera). There is also an anatomical conjugate - the distance from the cape to the middle of the upper inner edge of the symphysis; the anatomical conjugate is slightly (0.3-0.5 cm) larger than the obstetric conjugate. The obstetric, or true conjugate, is 11 cm. The transverse size is the distance between the most distant points of the nameless lines. This size is 13-13.5 cm. There are two oblique sizes: right and left, which are equal to 12-12.5 cm. The right oblique size is the distance from the right sacroiliac joint to the left ilio-pubic tubercle, the left oblique size is from left sacroiliac joint to the right iliac-pubic tubercle. In order to make it easier to navigate in the direction of the oblique dimensions of the pelvis in a woman in labor, M.S. Malinovsky and M.G. Kushnir offer the following reception. The hands of both hands are folded at a right angle, with the palms facing up; the ends of the fingers are brought closer to the outlet of the pelvis of the lying woman. The plane of the left hand will coincide with the left oblique size of the pelvis, the plane of the right hand with the right.

II. The plane of the wide part of the pelvic cavity has the following boundaries: in front - the middle of the inner surface of the symphysis, on the sides - the middle of the acetabulum, behind - the junction of the II and III sacral vertebrae. In the wide part of the pelvic cavity, two sizes are distinguished: straight and transverse. Direct size - from the junction of the II and III sacral vertebrae to the middle of the inner surface of the symphysis; equal to 12.5 cm. The transverse dimension is between the tops of the acetabulum; equal to 12.5 cm. There are no oblique dimensions in the wide part of the pelvic cavity because in this place the pelvis does not form a continuous bone ring. Oblique dimensions in the wide part of the pelvis are allowed conditionally (length 13 cm).

III. The plane of the narrow part of the cavity of the small pelvis is limited in front by the lower edge of the symphysis, from the sides - by the awns of the ischial bones, and behind - by the sacrococcygeal joint. There are two sizes: straight and transverse. The direct size goes from the sacrococcygeal joint to the lower edge of the symphysis (apex of the pubic arch); equal to 11-11.5 cm. The transverse dimension connects the spines of the ischial bones; equal to 10.5 cm.

IV. The plane of the exit of the small pelvis has the following boundaries: in front - the lower edge of the symphysis, from the sides - ischial tubercles, behind - the tip of the coccyx. The pelvic exit plane consists of two triangular planes, the common base of which is the line connecting the ischial tuberosities. In the outlet of the pelvis, two sizes are distinguished: straight and transverse. The direct size of the exit of the pelvis goes from the top of the coccyx to the lower edge of the symphysis; it is equal to 9.5 cm. When the fetus passes through the small pelvis, the coccyx departs by 1.5-2 cm and the direct size increases to 11.5 cm. The transverse size of the pelvic outlet connects the inner surfaces of the ischial tubercles; is 11 cm. Thus, at the entrance to the small pelvis, the largest size is the transverse one. In the wide part of the cavity, the direct and transverse dimensions are equal; the largest size will be the conditionally accepted oblique size. In the narrow part of the cavity and the outlet of the pelvis, the direct dimensions are larger than the transverse ones. In addition to the above (classical) pelvic cavities, there are parallel pelvic planes (Goji planes). The first (upper) plane passes through the terminal line (I. terminalis innominata) and is therefore called the terminal plane. The second - the main plane, runs parallel to the first at the level of the lower edge of the symphysis. It is called the main one because the head, having passed this plane, does not encounter significant obstacles, since it has passed a continuous bone ring. The third - the spinal plane, parallel to the first and second, crosses the pelvis in the spina oss. ischii. The fourth - the exit plane, represents the bottom of the small pelvis (its diaphragm) and almost coincides with the direction of the coccyx. The wire axis (line) of the pelvis. All planes (classical) of the small pelvis in front border on one or another point of the symphysis, and behind - on different points of the sacrum or coccyx. The symphysis is much shorter than the sacrum with the coccyx, so the planes of the pelvis converge in an anterior direction and fan-shaped diverge backwards. If you connect the middle of the direct dimensions of all the planes of the pelvis, you will get not a straight line, but a concave anterior (to the symphysis) line. This conditional line connecting the centers of all direct dimensions of the pelvis is called the wire axis of the pelvis. The wire axis of the pelvis is initially straight, it bends in the pelvic cavity in accordance with the concavity of the inner surface of the sacrum. In the direction of the wire axis of the pelvis, the fetus passes through the birth canal.

The angle of inclination of the pelvis (the intersection of the plane of its entrance with the plane of the horizon) when a woman is standing can be different depending on the physique and ranges from 45-55 °. It can be reduced if the woman lying on her back is forced to pull the hips strongly to the stomach, which leads to the elevation of the womb. It can be increased by placing a roll-shaped hard pillow under the lower back, which will lead to the downward deviation of the womb. A decrease in the angle of inclination of the pelvis is also achieved if the woman is given a semi-sitting position, squatting.

The structure and purpose of the bone pelvis

The birth canal includes both the bony pelvis and the soft tissues of the birth canal (uterus, vagina, pelvic floor, and external genitalia).

1. Bone pelvis. (Pelvis)

It is a combination of 4 bones:

2 x nameless (ossa innominata)

Sacrum (os sacrum)

Coccyx (os coccygeum)

Nameless bones are connected to each other through the pubic articulation (symphysis), with the sacrum using the right and left sacroiliac joints (articulatio sacro-iliaca dextra et sinistra).

The coccyx is connected to the sacrum through the sacrococcygeal articulation (acticulatio sacro-coccygeum).

The pelvis is divided into large and small

a) The large pelvis is that part of the bone canal that is located above its nameless or border line (linea innominata, s. terminalis). The iliac fossa of the innominate bones (fossa iliaca dextra et sinistra) serve as the side walls. In front, the large pelvis is open, in the back it is limited by the lumbar part of the spine (IV and V vertebrae).

The size of the small pelvis is judged by the size of the large pelvis.

b) The small pelvis is that part of the bone canal that is located below the nameless or border line. Most important in the obstetric sense. Knowing its size is necessary to understand the biomechanism of childbirth. Moving in the small pelvis, the fetus is subjected to the greatest stress - compression, rotation. Possible deformation of the bones of the fetal head.

The walls of the small pelvis are formed: in front - by the inner surface of the pubic joint, on the sides - by the inner surfaces of the innominate bones, behind - by the inner surface of the sacrum.

Classic pelvic planes

Pelvic planes:

a) the plane of entry into the small pelvis;

b) the plane of the wide part;

c) the plane of the narrow part;

d) the plane of the exit of the small pelvis.

I. The boundaries of the plane of entry into the small pelvis - the cape of the sacrum, the nameless line and the upper edge of the symphysis.

Dimensions of the entrance to the small pelvis:

1) Direct - true conjugate (conjugata vera) - from the most protruding point of the inner surface of the womb to the cape of the sacrum - 11 cm.

2) Transverse dimension - connects the most distant points of the border line - 13-13.5 cm.

3) Two oblique sizes: the right one - from the right sacroiliac joint to the left iliopubic tubercle (eminentia-iliopubica sinistra) and the left one - from the left sacroiliac joint to the right iliopubic tubercle.

Oblique dimensions are 12-12.5 cm.

Normally, oblique dimensions are considered to be the dimensions of a typical insertion of the fetal head.

II. The plane of the wide part of the pelvic cavity.

Borders in front - the middle of the inner surface of the pubic joint, behind - the line of connection of the 2nd and 3rd sacral vertebrae, from the sides - the middle of the acetabulum (lamina accetabuli).

The dimensions of the wide part of the pelvic cavity:

direct size - from the upper edge of the 3rd sacral vertebra to the middle of the inner surface of the symphysis - 12.5 cm;

transverse size - between the midpoints of the acetabulum 12.5 cm;

oblique dimensions - conditionally from the upper edge of the large ischial notch (incisura ischiadica major) of one side to the groove of the obturator muscle (sulcus obturatorius) - 13 cm.

III. The plane of the narrow part of the pelvic cavity.

Borders: in front - the lower edge of the pubic joint, behind - the tip of the sacrum, from the sides - ischial spines (spinae ischii).

Dimensions of the narrow part of the pelvic cavity:

direct size - from the top of the sacrum to the lower edge of the pubic joint (11-11.5 cm);

transverse size - the line connecting the ischial spines - 10.5 cm.

IV. The plane of the exit of the small pelvis.

Borders: in front - the pubic arch, behind - the tip of the coccyx, on the sides - the inner surfaces of the ischial tubercles (tubera ischii).

Dimensions of the exit of the small pelvis:

direct size - from the lower edge of the pubic joint to the top of the coccyx - 9.5 cm, with deviation of the coccyx - 11.5 cm;

transverse dimension - between the inner surfaces of the ischial tubercles - 11 cm.

Wire line of the pelvis (pelvic axis).

If you connect the centers of all the direct dimensions of the pelvis to each other, you get a concave anterior line, which is called the wire axis, or the line of the pelvis.

The wire axis of the pelvis first goes in the form of a straight line until it reaches a plane that intersects the lower edge of the symphysis, the so-called main one. From here, a little lower, it begins to bend, crossing at right angles a successive series of planes that run from the lower edge of the symphysis to the sacrum and coccyx. If this line is continued upwards from the center of the entrance to the pelvis, then it will cross the abdominal wall in the navel; if it is continued downwards, then it will pass through the lower end of the coccyx. As for the exit axis of the pelvis, then, being continued upward, it will cross the upper part of the 1st sacral vertebra.

The head of the fetus, when passing through the birth canal, cuts through a series of parallel planes with its circumference until it reaches the wire point of the bottom of the pelvis. These planes through which the head passes, Goji called parallel planes.

Of the parallel planes, the most important are the following four, which are almost equally spaced from each other (3-4 cm).

The first (upper) plane passes through the terminal line (linea terminalis) and is therefore called the terminal plane.

The second plane, parallel to the first, crosses the symphysis at its lower edge - the inferior parallel plane. It is called the main plane.

The third plane, parallel to the first and second, crosses the pelvis in the region of spinae ossis ischii - this is the spinal plane.

Finally, the fourth plane, parallel to the third, is the bottom of the small pelvis, its diaphragm, and almost coincides with the direction of the coccyx. This plane is called the output plane.

Inclination of the pelvis - the ratio of the plane of entry into the pelvis to the horizontal plane (55-60 gr.) The angle of inclination can be slightly increased or decreased by placing a roller under the lower back and crosses for a lying woman.

pelvic floor

The pelvic floor is a powerful muscular-fascial layer, consisting of three layers.

I. Lower (outer) layer.

1. Bulbous-cavernous (m. bulbocavernosus) compresses the vaginal entrance.

2. Ischiocavernosus (m. ischocavernosus).

3. Superficial transverse muscle of the perineum (m. transversus perinei superficialis).

4. external sphincter of the anus (m. sphincter ani externus).

II. The middle layer is the urogenital diaphragm (diaphragma urogenitale) - a triangular muscular-fascial plate located under the symphysis, in the pubic arch. Its back part is called the deep transverse muscle of the perineum (m. transversus perinei profundus).

III. The upper (inner) layer - the pelvic diaphragm (diaphragma pelvis) consists of a paired muscle that lifts the anus (m. Levator ani).

Functions of the muscles and fasciae of the pelvic floor.

1. They are a support for the internal genital organs, contribute to the preservation of their normal position. With the contraction, the genital gap closes, the lumen of the rectum and vagina narrows.

2. They are a support for the viscera, participate in the regulation of intra-abdominal pressure.

3. During childbirth, during expulsion, all three layers of the pelvic floor muscles stretch and form a wide tube, which is a continuation of the bone birth canal.

Obstetric (anterior) perineum - part of the pelvic floor between the posterior commissure of the labia and the anus.

Posterior perineum - part of the pelvic floor, between the anus and the coccyx.

LITERATURE:

BASIC:

1. Bodyazhina V.I., Zhmakin K.N. Obstetrics, M., Medicine, 1995.

2. Malinovsky M.R. Operative obstetrics. 3rd ed. M., Medicine, 1974.

3. Serov V.N., Strizhakov A.N., Markin S.A. Practical obstetrics. M., Medicine, 1989. - 512 p.

4. Chernukha E.A. Maternity block. M., Medicine, 1991.

OPTIONAL:

1. Abramchenko V.V. Modern methods of preparing pregnant women for childbirth. St. Petersburg., 1991. - 255 p.

2. Directory of the doctor of the antenatal clinic. Ed. Gerasimovich G.I.

In this way, small pelvis it appears as if in the form of a channel, definitely curved in the anterior direction. But it only seems. In fact, studies have shown that the bony pelvis is not curved anteriorly. The fetus, when the head passes through the birth canal, passes with its head circumference through several planes, until it reaches the bottom of the pelvic cavity. The planes through which the fetus passes with its head were studied by the scientist Goji and named them as parallel planes. When examining a woman, they are easily identified by well-recognized anatomical points.
Among the parallel planes, four planes are distinguished, which are the most important for understanding obstetrics. These planes are at an equal distance from each other, approximately 3-4 cm.

Topmost and first plane is located at the level of the terminal line and passes through it (linea terminalis or innominata), as a result of which it was called the terminal plane.

Second plane, is at some distance from the first and parallel to it. The second plane of the pelvis passes at the level of the pubic symphysis and crosses it at the level of the lower edge. Given the location of the plane, it was called the lower-latitude parallel plane. It is also called the main plane, because the head, having passed this plane, usually no longer encounters obstacles on its further path (it has passed a solid bone ring).

Third plane of the pelvis, is parallel to all the planes described above and passes through the pelvis at the level of spinae ossis ischii of the pelvis. As a result, the third plane of the pelvis was called the spinal plane.

Finally, fourth plane, parallel to the third, represents the bottom of the small pelvis, its diaphragm (diaphragma) and almost coincides with the direction of the coccyx. This plane is called the output plane.

The head goes into the pelvis from the entrance to its bottom (almost do perpendicular lily, which intersects all four parallel planes.

When the head's wire dot j will start up to the exit plane, the head turns forward, towards the exit. Thus, the axis of the pelvis is a line in the form of an arc connecting the middle, of all direct sizes, resembling, in the words of A.P. Gubarev, a fishhook: in the upper parts of the pelvis, the direction of the genital canal (the axis of the pelvis) goes in a straight line from top to bottom, making a sharp anterior turn at the bottom of the pelvis, approximately at the level of the spinal plane (knee of the birth canal).

Connection of the pelvic bones.

Pelvic bones(an outdated name is nameless), the sacrum and coccyx are interconnected by the following strong joints.

1. pubic articulation(symphysis) - fusion of the pubic bones through a fibrocartilaginous layer with the formation of a narrow articular cavity in the center. The pubic joint is reinforced with powerful, strong ligaments. The symphysis as a semi-joint (hemearthrosis) has an extremely limited range of motion. Only during pregnancy, due to edematous impregnation and loosening of tissues, small movements (up to 10 mm) of the articular ends, pubic bones up and down, like piano keys, are possible, especially in young multiparous women. Such mobility is of some importance in the management of childbirth with difficult insertion of the head and during surgical interventions. In some cases, greater mobility in the pubic junction causes some pain and awkwardness in walking and standing during pregnancy.

2. sacroiliac joint(articulatio sacroiliaca) - the connection of the sacrum with both iliac. Thus, the articulation is paired, built but of the same type as the symphysis, and also has strong ligaments. The joint is a typical amphiarthrosis, its active mobility is zero, the passive one is minimal (Krukenberg) - only slight sliding movements are possible.

3. sacrococcygeal articulation(articulatio sacro-coccygea) - connection between the distal surface of the coccyx. The articulation is reinforced from the sides, as well as in front and behind by auxiliary ligaments. It is so mobile that the coccygeal bone can freely bend back, which actually happens during childbirth. Softening of the articular cartilage during pregnancy increases joint mobility. With age (after 35-40 years), in women, due to ossification of the cartilage, the mobility of the joint decreases, as a result of which, during childbirth, with a sharp deviation of the coccyx posteriorly, its dislocation and even fracture can occur.