Type of connection of the pelvic bones and the sacrum. Joints of the bones of the pelvic girdle and the bones of the free lower limb

The skeleton of the lower extremities is divided into the bones of the pelvic girdle and the bones of the free lower limb.

Taz- (Pelvis) consists of 3 bones, firmly interconnected, with the sacrum, coccyx and their connections.

The pelvis is formed by one unpaired bone, the sacrum and two massive pelvic bones.

Pelvic bone(Os coxae) - it distinguishes 3 interconnected bones: ilium (Os ileum), ischial (Os ischii), pubic or pubic (Os pubis). Only after 16 years they grow together into one. All these 3 bones are interconnected by bodies in the region of the acetabulum, which includes the head of the femur.

Ilium- the largest, consists of a body and a wing. The wing is expanded upwards and ends in a long edge with a crest. Front on the ridge 2 protrusions:

The anterior projections are the superior and inferior iliac spines. Behind the crest, the posterior superior and inferior iliac spines are less pronounced.

The inner surface of the wing is concave and forms the iliac fossa, and the outer surface is convex (gluteal surface). On the inner surface of the wing there is an ear-shaped surface, with which the pelvic bone articulates with the sacrum. The ilium has an arcuate line.

Ischium- consists of a body and branches, has an ischial tubercle and an ischial spine. Above and below the spine are the greater and lesser ischial notches.

Pubic bone- consists of a body, upper and lower branches. Together with the branch of the ischium, they limit the obturator opening, which is closed by a connective tissue membrane.

On the pelvic bone there is in front iliopubic eminence, which is located at the junction of the bodies of the pubic and iliac bones.

acetabulum formed by fused bodies of 3 pelvic bones. The articular semilunar surface of the acetabulum is located on the peripheral part of the cavity.

Pelvis connection:

The sacroiliac joint is a flat, inactive, paired joint. It is formed by the ear-shaped surfaces of the sacrum and ilium. Strengthened by ligaments - anterior and posterior ilio-sacral; interosseous sacroiliac (fuse with the joint capsule), iliac-lumbar (from the transverse processes of the two lower lumbar vertebrae to the iliac crest). An unpaired fusion is formed in front of the pelvis - the pubic symphysis is a semi-joint in which the pubic bones are interconnected using cartilage. In the thickness of the cartilage there is a small cavity filled with fluid. Reinforced by the arcuate pubic ligament and superior pubic ligament. The intrinsic ligaments of the pelvis include the sacrotuberous and the sacrospinous. They close the sciatic notches into the large and small sciatic foramen, through which muscles, vessels and nerves pass.

Taz (Pelvis)- Distinguish between the large and small pelvis. The boundary line separating them runs from the cape of the spine along the arcuate lines of the ilium, then along the upper branches of the pubic bones and the upper edge of the pubic symphysis.

Large pelvis- formed by deployed wings of the iliac bones - this is a receptacle for the abdominal organs.

Small pelvis- formed by the pelvic surface of the sacrum and coccyx, ischial and pubic bones. It distinguishes between the upper and lower apertures (inlet and outlet) and the cavity. In the pelvis are the internal organs, and it is also the birth canal.

Related information:

1. Estel Otium Diamond Leveling cream for smooth and shiny hair
2. Are there any special subtleties or recipes for losing weight?
3. A) Rectangular planes are the most convenient for their constructive combination with each other. This convenience is that
4. Algorithm for providing emergency care to a child with shock in combination with severe malnutrition and the calculation of intravenous fluid

IV. STUDY NEW MATERIAL

III. STUDENT KNOWLEDGE CONTROL

II. MOTIVATION OF LEARNING ACTIVITIES

1. Knowledge of the morpho-anatomical and physiological structure of the human lower limb movement apparatus, the structure of bones and their joints is necessary when studying clinical disciplines, as well as in your future practical activities.

A. Questions for oral answers at the blackboard:

1. Tell us about the topography, structure, connection of the bones of the shoulder girdle (collarbone, shoulder blade).

2. Tell us about the topography, structure, connection of the humerus.

3. Tell us about the topography, structure, connection of the ulna, radius.

4. Tell us about the topography, structure, connection of the bones of the hand.

B. Answer the silent cards (written survey):

1. The structure of the scapula and collarbone.

2. The structure of the humerus.

3. The structure of the bones of the forearm.

4. The structure of the bones of the hand.

Plan:

1. The bones of the pelvis. Connection of the pelvic bones.

2. Skeleton of the free lower limb.

3. Connection of the bones of the free lower limb.

4. Foot as a whole.

The skeleton of the lower extremities is divided into the bones of the pelvic girdle and the bones of the free lower limb.

Taz- (Pelvis) consists of 3 bones, firmly interconnected, with the sacrum, coccyx and their connections.

The pelvis is formed by one unpaired bone, the sacrum and two massive pelvic bones.

Pelvic bone(Os coxae) - it distinguishes 3 interconnected bones: ilium (Os ileum), ischial (Os ischii), pubic or pubic (Os pubis). Only after 16 years they grow together into one. All these 3 bones are interconnected by bodies in the region of the acetabulum, which includes the head of the femur.

Ilium- the largest, consists of a body and a wing. The wing is expanded upwards and ends in a long edge with a crest. Front on the ridge 2 protrusions:

The anterior projections are the superior and inferior iliac spines. Behind the crest, the posterior superior and inferior iliac spines are less pronounced.

The inner surface of the wing is concave and forms the iliac fossa, and the outer surface is convex (gluteal surface). On the inner surface of the wing there is an ear-shaped surface, with which the pelvic bone articulates with the sacrum. The ilium has an arcuate line.

Ischium- consists of a body and branches, has an ischial tubercle and an ischial spine. Above and below the spine are the greater and lesser ischial notches.

Pubic bone- consists of a body, upper and lower branches. Together with the branch of the ischium, they limit the obturator opening, which is closed by a connective tissue membrane.

On the pelvic bone there is in front iliopubic eminence, which is located at the junction of the bodies of the pubic and iliac bones.

acetabulum formed by fused bodies of 3 pelvic bones. The articular semilunar surface of the acetabulum is located on the peripheral part of the cavity.

Pelvis connection:

The sacroiliac joint is a flat, inactive, paired joint. It is formed by the ear-shaped surfaces of the sacrum and ilium. Strengthened by ligaments - anterior and posterior ilio-sacral; interosseous sacroiliac (fuse with the joint capsule), iliac-lumbar (from the transverse processes of the two lower lumbar vertebrae to the iliac crest). An unpaired fusion is formed in front of the pelvis - the pubic symphysis is a semi-joint in which the pubic bones are interconnected using cartilage. In the thickness of the cartilage there is a small cavity filled with fluid. Reinforced by the arcuate pubic ligament and superior pubic ligament. The intrinsic ligaments of the pelvis include the sacrotuberous and the sacrospinous. They close the sciatic notches into the large and small sciatic foramen, through which muscles, vessels and nerves pass.

Taz (Pelvis)- Distinguish between the large and small pelvis. The boundary line separating them runs from the cape of the spine along the arcuate lines of the ilium, then along the upper branches of the pubic bones and the upper edge of the pubic symphysis.

Large pelvis- formed by deployed wings of the iliac bones - this is a receptacle for the abdominal organs.

Small pelvis- formed by the pelvic surface of the sacrum and coccyx, ischial and pubic bones. It distinguishes between the upper and lower apertures (inlet and outlet) and the cavity. In the pelvis are the internal organs, and it is also the birth canal.

The joints of the pelvic bones in humans reflect the development of these bones in connection with changing functional conditions in the process of phylogenesis. As mentioned above, the pelvis in four-legged vertebrates does not experience a large load due to their horizontal position.

With the transition of a person to an upright posture, the pelvis becomes a support for the viscera and a place for transferring weight from the trunk to the lower limbs, as a result of which it experiences a huge load. Separate bones, connected by cartilage, merge into a single bone formation - the pelvic bone, so that synchondrosis passes into synostosis. However, synchondrosis at the junction of both pubic bones does not turn into synostosis, but becomes a symphysis.

The connection of both bones of the pelvis with the sacrum, which needs a combination of mobility with strength, takes the form of a true joint - diarthrosis, firmly strengthened by ligaments ( syndesmosis).

As a result, all types of joints are observed in the human pelvis, reflecting the successive stages of skeletal development: synarthroses in the form of syndesmosis (ligaments), synchondroses (between separate parts of the pelvic bone) and synostoses (after merging them into the pelvic bone), symphysis (pubic) and diarthrosis ( sacroiliac joint). The overall mobility between the pelvic bones is very low (4-10°).

1. Sacroiliac joint, art. sacroiliaca, refers to the type of tight joints (amphiarthrosis), formed by the ear-shaped articular surfaces of the sacrum and ilium in contact with each other. It is strengthened ligg. sacroiliaca interossea arranged in short bundles between tuberositas iliaca and the sacrum, which are among the strongest ligaments of the entire human body. They serve as the axis around which the movements of the sacroiliac joint occur.

The latter is also strengthened by other ligaments connecting the sacrum and the ilium: in front - ligg. sacroiliaca ventralia, behind - ligg. sacroiliac dorsalia, as well as lig. iliolumbale, which is stretched from the transverse process of the V lumbar vertebra to Crista Iliaca.

The sacroiliac joint is vascularized from the aa. lumbalis, iliolumbalis et sacrales laterales. The outflow of venous blood occurs in the veins of the same name. The outflow of lymph is carried out through deep lymphatic vessels in nodi lymphatici sacrales et lumbales. The innervation of the joint is provided by the branches of the lumbar and sacral plexuses.

2. Pubic symphysis, symphysis piibica, connects, located along the midline, both pubic bones to each other. Between the facies symphysitis of these bones facing each other, covered with a layer of hyaline cartilage, a fibrocartilaginous plate is laid, discus interpubicus, in which usually, starting from the age of 7, there is a narrow synovial gap (half-joint).

The pubic symphysis is supported by a dense periosteum and ligaments; on the upper edge - lig. pubicum superius and on the lower - lig. arcuatum pubis; the latter smoothes the angle under the symphysis, angulus subpubicus.

3. Lig. sacrotuberal and lig. sacrospinal- two strong interosseous ligaments connecting the sacrum to the pelvic bone on each side: the first - with tuber ischii, the second - with spina ischiadica. The described ligaments complement the bony skeleton of the pelvis in its posterior-lower section and turn the large and small ischial notches into openings of the same name: foramen ischiadicum majus et minus.

4. Obturator membrane, membrana obturatoria,- fibrous plate covering the foramen obturatum of the pelvis, with the exception of the upper lateral angle of this opening. Attached to the edges of the sulcus obturatorius of the pubic bone located here, it turns this groove into a canal of the same name, canalis obturatorius due to the passage of the obturator vessels and nerve.

Page 5 of 5

5.5. Joints of the bones of the lower limb

Joints of the bones of the girdle of the lower limb. The pelvic bones are connected to each other and to the sacrum by means of discontinuous, continuous joints and a semi-joint.

sacroiliac joint, articulatio sacroiliaca, is formed by the ear-shaped surfaces of the sacrum and ilium. The articular surfaces are covered with fibrous cartilage. The sacroiliac joint is flat, strengthened by powerful sacroiliac ligaments, so there are no movements in it.

pubic symphysis, symphysis pubica, is located in the median plane, connects the pubic bones to each other and is a semi-joint (Fig. 5.10). Inside the cartilage (in its upper posterior section) there is a cavity in the form of a narrow gap, which develops on the 1st - 2nd year of life. Small movements in the pubic symphysis are possible only in women during childbirth. The pubic symphysis is strengthened by two ligaments: from above - by the superior pubic ligament, from below - by the inferior pubic ligament.

Continuous joints of the pelvic bone. The iliac-lumbar ligament descends from the transverse processes of the two lower lumbar vertebrae to the iliac crest.

sacrotuberous ligament connects the ischial tubercle with the lateral edge of the sacrum and coccyx.

sacrospinous ligament stretched from the ischial spine to the lateral edge of the sacrum.

Rice. 5.10. Bone connections and pelvic dimensions (diagram): a - top view: 7 - distantia intercristalis; 2 - distantia interspinosa; 3 - pubic symphysis; 4 - transverse size of the entrance to the small pelvis; 5 - true conjugate; 6 - border line; 7 - sacroiliac joint; b - side view: 7 - large sciatic foramen; 2 - small sciatic foramen; 3 - sacrospinous ligament; 4 - sacrotuberous ligament; 5 - output conjugate; 6 - angle of inclination of the pelvis; 7 - wire axis of the pelvis; 8 - true conjugate; 9 - anatomical conjugate; 10 - diagonal conjugate

obturator membrane closes the hole of the same name, leaving a small hole free at the obturator sulcus (see Fig. 5.11).

Taz in general. The pelvic bones, sacrum, coccyx and their ligamentous apparatus form the pelvis, pelvis. With the help of the pelvic bones, the trunk is also connected to the free section of the lower extremities.

Distinguish large pelvis, pelvis major, and small pelvis, pelvis minor. They are separated from each other by a border line, which is drawn on both sides from the cape through an arcuate line along the pubic crest to the pubic tubercle and further along the upper edge of the pubic symphysis.

The walls of the pelvic cavity form: behind - the sacrum and the anterior surface of the coccyx; in front - the anterior sections of the pubic bones and symphysis; from the sides - the inner surface of the pelvic bone below the border line. The obturator foramen located here is almost completely closed by the membrane of the same name, except for a small hole in the region of the obturator sulcus.

On the side wall of the small pelvis are the large and small sciatic foramen. The greater sciatic foramen is bounded by the sacrospinous ligament and the greater sciatic notch. The lesser sciatic foramen is limited by the sacrospinous and sacrotuberous ligaments, as well as the lesser sciatic notch. Vessels and nerves pass through these openings from the pelvic cavity to the gluteal region.

The pelvis in a vertical position of a person is tilted forward; the plane of the upper aperture of the pelvis forms an acute angle with the horizontal plane, forming the angle of inclination of the pelvis. In women, this angle is 55-60°, in men 50-55°.

Sex differences of the pelvis. In women, the pelvis is lower and wider. The distance between the spines and the iliac crests is greater, since the wings of these bones are deployed to the sides. The cape protrudes less forward, so the entrance to the male pelvis resembles a card heart in shape; in women, it is more rounded, sometimes even approaching an ellipse. The symphysis of the female pelvis is wider and shorter. The pelvic cavity is larger in women and narrower in men. The sacrum in women is wider and shorter, the ischial tubercles are turned to the sides, so the transverse size of the outlet is 1–2 cm larger. The angle between the lower branches of the pubic bones (subpubic angle) in women is 90-100°, in men 70-75°.

Of great importance in obstetrics for predicting the course of childbirth is knowledge of the average size of a woman's pelvis. The median anteroposterior dimensions of the small pelvis are collectively called conjugates. Typically, input and output conjugates are measured. The direct size of the entrance to the small pelvis - the distance between the cape and the upper edge of the pubic symphysis, is called the anatomical conjugate. It is equal to 11.5 cm. The distance between the cape and the most posterior point of the symphysis is called the true, or gynecological conjugate; it is equal to 10.5 - 11.0 cm. The diagonal conjugate is measured between the cape and the lower edge of the symphysis, it can be determined in a woman during a vaginal examination; its value is 12.5 -13.0 cm. To determine the size of the true conjugate, it is necessary to subtract 2 cm from the length of the diagonal conjugate.

Transverse diameter of the entrance to the small pelvis measured between the most distant points of the boundary line; it is equal to 13.5 cm. The oblique diameter of the entrance to the small pelvis is the distance between the sacroiliac joint on one side and the iliac-pubic eminence on the other; it is equal to 13 cm.

The direct size of the exit (exit conjugate) from the small pelvis in women is 9 cm and is determined between the tip of the coccyx and the lower edge of the pubic symphysis. During childbirth, the coccyx deviates back in the sacrococcygeal synchondrosis, and this distance increases by 2.0-2.5 cm.

Cross outlet dimension from the pelvic cavity is 11 cm. It is measured between the inner surfaces of the ischial tuberosities.

Wired pelvic axis, or guide line, is a curve connecting the midpoints of all conjugates. She goes almost parallel to the anterior surface of the sacrum and shows the path that the fetal head takes during childbirth.

Rice. 5.11. Hip joint: 1 - joint capsule; 2- iliac-femoral ligament; 3- obturator membrane; 4- pubic-femoral ligament; 5 - circular zone; 6- articular lip; 7 - acetabulum; 8- ligament of the femoral head

In obstetric practice, some dimensions of the large pelvis are also of great importance (see Fig. 5.10): the distance between the anterior superior iliac spines (distantia interspinosa), which is 25–27 cm; the distance between the most distant points of the iliac crests (distantia intercristalis), equal to 27 - 29 cm; the distance between the large trochanters of the femur (distantia intertrochanterica), equal to 31-32 cm. To assess the anteroposterior dimensions of the pelvis, the external conjugate is measured - the distance between the outer surface of the pubic symphysis and the spinous process of the V lumbar vertebra, which is 20 cm.

Joints of the free lower limb.

hip joint, articulatio coxae, is formed by the acetabulum of the pelvis and the head of the femur (Fig. 5.11). The central fossa of the acetabulum is filled with adipose tissue.

The articular capsule is attached along the edge of the acetabular lip and along the medial edge of the femoral neck. Thus, most of the femoral neck lies outside the joint cavity and the fracture of its lateral part is extra-articular, which greatly facilitates the treatment and prognosis of the injury.

In the thickness of the capsule is a ligament, called the circular zone, which covers the neck of the femur approximately in the middle. In the capsule of the joint, there are also fibers of three ligaments directed longitudinally: ilio-femoral, pubic-femoral and ischio-femoral, connecting the bones of the same name.

Auxiliary are the following elements of the joint: the acetabular lip, which complements the semilunar articular surface of the acetabulum; transverse ligament of the acetabulum, thrown over the notch of the acetabulum; ligament of the femoral head that connects the fossa of the acetabulum to the fossa of the femoral head and contains the blood vessels that feed the femoral head.

The hip joint is a type of spherical joint - walnut, or cup-shaped. It allows movements around all axes: flexion and extension around the frontal axis, abduction and adduction around the sagittal axis, circular movement around the frontal and sagittal axes, rotation around the vertical axis.

Knee-joint, articulatio genus, is the largest joint of the human body. Three bones take part in its formation: the femur, tibia and patella (Fig. 5.12). The articular surfaces are: the lateral and medial condyles of the femur, the superior articular surface of the tibia and the articular surface of the patella.

The capsule of the knee joint is attached to the femur 1 cm above the edge of the articular cartilage and in front passes into the suprapatellar bursa located above the patella between the femur and the tendon of the quadriceps femoris muscle. On the tibia, the capsule is attached along the edge of the articular surface.

The joint capsule is strengthened by the peroneal and tibial collateral ligaments located on both sides of the joint, as well as the patellar ligament. It is a tendon of the quadriceps femoris muscle, located below the patella.

Rice. 5.12. Knee-joint: 1 - femur; 2 - posterior cruciate ligament; 3 - anterior cruciate ligament; 4 - medial meniscus; 5 - transverse ligament of the knee; 6- collateral tibial ligament; 7- ligament of the patella; 8 - patella; 9 - tendon of the quadriceps femoris; 10 - interosseous membrane of the leg; 11 - tibia; 12 - fibula; 13 - tibiofibular joint; 14- collateral peroneal ligament; 15 - lateral meniscus; 16 - lateral condyle of the femur; 17 - patella surface

The joint has many accessory elements such as the patella, menisci, intraarticular ligaments, bursae, and folds.

The lateral and medial menisci partially eliminate the incongruence of the articular surfaces and perform a shock-absorbing role. The medial meniscus is narrow, crescent-shaped. The lateral meniscus is wider, oval. The menisci are connected to each other by the transverse ligament of the knee.

The anterior and posterior cruciate ligaments firmly connect the femur and tibia, crossing each other in the form of the letter "X".

The auxiliary elements of the knee joint also include pterygoid folds, which contain fatty tissue. They are

located below the patella on both sides. From the top of the patella to the anterior part of the tibia, an unpaired subpatellar synovial fold is directed.

The knee joint has several synovial bags, bursae synoviales, some of which communicate with the joint cavity:

1) suprapatellar bag, located between the femur and the tendon of the quadriceps femoris muscle; communicates with the joint cavity;

2) a deep subpatellar bag located between the patellar ligament and the tibia;

3) subcutaneous and subtendonal prepatellar bursae located in the tissue on the anterior surface of the knee joint;

4) muscle bags located at the place of attachment of the muscles of the lower leg and thigh in the area of ​​the knee joint.

Rice. 5.13. Joints of the bones of the lower leg: 1 - upper articular surface; 2 - tibia; 3 - interosseous membrane of the leg; 4 - medial malleolus; 5 - lower articular surface; b - lateral ankle; 7 - tibiofibular syndesmosis; 8 - fibula; 9 - tibiofibular joint

The knee joint is condylar in shape. Flexion and extension occur around the frontal axis. Around the vertical axis in a bent position, rotation of the leg in a small amount is possible.

Joints of the bones of the leg. The bones of the lower leg are connected to each other with the help of discontinuous and continuous connections.

The proximal ends of the bones of the lower leg are connected by a discontinuous connection - the tibiofibular joint, articulatio tibiofibularis (Fig. 5.13), - flat, inactive. The distal ends of the bones of the lower leg are connected by the tibiofibular syndesmosis, represented by short ligaments connecting the fibular notch of the tibia and the lateral malleolus of the fibula. A strong fibrous plate is an interosseous membrane that connects both bones almost throughout.

Joints of the bones of the foot. The joints of the bones of the foot can be divided into four groups:

1) connections of the bones of the foot with the bones of the lower leg - the ankle joint;

2) connections between the bones of the tarsus;

3) connections between the bones of the tarsus and metatarsus;

4) joints of the bones of the fingers.

Ankle (supratalar) joint, articulatio talocruralis, formed by both bones of the lower leg and the talus (Fig. 5.14). In this case, the block of the talus from the sides is covered by the lateral and medial ankles.

The joint capsule is attached along the edge of the articular surfaces. On the medial side, it is strengthened by the medial (deltoid) ligament. On the lateral side, the joint capsule is strengthened by three ligaments: anterior and posterior early-fibular, as well as calcaneal-fibular, which connect the corresponding bones.

Rice. 5.14. Joints of the bones of the foot: 1 - tibia; 2 - interosseous membrane of the leg; 3 - fibula; 4 - ankle joint; 5 - talocalcaneal-navicular joint; 6 - navicular bone; 7 - calcaneocuboid joint; 8 - tarsal-metatarsal joints; 9 - metatarsophalangeal joints; 10 - interphalangeal joints

The ankle joint is blocky in shape. It allows movements around the frontal axis: plantar flexion and dorsiflexion (extension). Due to the fact that the talus block is narrower behind, with maximum plantar flexion in the ankle joint, lateral rocking movements in a small amount are possible. Movements in the ankle joint are combined with movements in the subtalar and talocalcaneal-navicular joints.

Joints of the bones of the tarsus. Represented by the following joints: subtalar, talocalcaneal-navicular, calcaneocuboid, cuneiform.

subtalar joint, articulatio subtalaris, located between the talus and calcaneus. The joint is cylindrical, slight movements are possible in it only around the sagittal axis.

talocalcaneal-navicular joint, articulatio talocalcaneonavicularis, has a spherical shape, located between the bones of the same name. The articular cavity is supplemented by cartilage, which is formed along the plantar calcaneal-navicular ligament.

Ankle (nadtalar), the subtalar and talocalcaneal-navicular joints usually function together, forming a single functional joint of the foot, in which the talus plays the role of a bone disk.

Calcaneocuboid joint, articulatio calcaneocuboidea, located between the bones of the same name, saddle-shaped, inactive.

From a surgical point of view, the calcaneocuboid and talonavicular (part of the talocalcaneonavicular) joints are considered as one joint - the transverse tarsal joint (Chopard's joint). The articular space of these joints is located almost on the same line, along which it is possible to make an exarticulation (exarticulation) of the foot in case of severe injuries.

wedge-shaped joint, articulatio cuneonavicularis, is formed by the navicular and sphenoid bones and is practically immobile.

Tarsus-metatarsal joints, articulationes tarsometatarsales, are three flat joints located between the medial sphenoid and first metatarsal bones; between the intermediate, lateral sphenoid and II, III metatarsal bones; between the cuboid and IV, V metatarsal bones. All three joints from a surgical point of view are combined into one joint - the Lisfranc joint, which is also used to isolate the distal part of the foot.

metatarsophalangeal joints, articulationes metatarsophalangeae, formed by the heads of the metatarsal bones and the pits of the bases of the proximal phalanges. They are spherical in shape, strengthened by collateral (lateral) and plantar ligaments. They are fixed to each other by a deep transverse metatarsal ligament running transversely between the heads of the I-V metatarsal bones. This ligament plays an important role in the formation of the transverse metatarsal arch of the foot.

Two sesamoid bones are constantly enclosed in the plantar part of the capsule of the I metatarsophalangeal joint, so it functions as a block joint. The joints of the other four fingers function as ellipsoid. Flexion and extension around the frontal axis, abduction and adduction around the sagittal axis, and a small amount of circular motion are possible in them.

interphalangeal joints, articulationes interphalangeae, in form and function are similar to the same joints of the hand. They belong to block joints. They are strengthened by collateral and plantar ligaments. In the normal state, the proximal phalanges are in a state of dorsiflexion, and the middle ones are in plantar flexion.

As mentioned earlier, the foot forms longitudinal (five) and transverse (two) arches. A special role in the fixation of the transverse arches belongs to the deep transverse metatarsal ligament, which connects the metatarsophalangeal joints. The longitudinal arches are reinforced by a long plantar ligament that runs from the calcaneal tuber to the base of each metatarsal. The ligaments are the "passive" fixators of the arches of the foot.

test questions

1. What types of bone joints do you know?

2. Describe the continuous connections of the bones.

3. Name the main elements of the joint.

4. List the auxiliary elements of the joint.

5. How are joints classified according to shape? Describe the possible movements in them.

6. Give a classification of vertebral joints.

7. List the bends of the spinal column and name the timing of their appearance.

8. What rib connections do you know?

9. Describe the structural features of the temporomandibular joint.

10. List the joints of the upper limb. What movements are implemented in them?

11. What connections does the pelvic bone form?

12. What gender differences do you know of the pelvis?

13. List the dimensions of the female pelvis.

14. Describe the joints of the free lower limb.

Why, at first glance, the fixed connection of the pelvic bones with the sacrum still has little mobility? The elements of the pelvis are attached to each other with the help of low-elastic ligaments, these structures allow the bones to diverge somewhat.

Pelvis as a functional unit

In order to understand whether the pelvis should be connected to the sacrum using a movable connection, it is necessary to understand the functions and general structure of this part of the skeleton. The pelvis is formed in such a way that it has all types of joints:

1. Movable joint. It is called the true joint. First of all, it is the hip joint, which connects the limbs to the pelvis. Also, like most joints, it does not have a large angle of movement.
2. Fixed joint. These are such joints that are formed with the help of tight ligaments. These include the sacroiliac joint, fixed by several ligaments.
3. Transition joint. They define it as something between a mobile and a fixed connection, called a symphysis. This is how the frontal bone is connected to other elements with the help of cartilage tissues, in which there is a gap - the pubic junction.

The pubic joint is almost always motionless, it is fixed by ligaments. Its transitional form will only play into the hands of a woman when the time comes for childbirth - in order for the fetus not to be injured, the ligaments during pregnancy will become more elastic, which will make it easier for the child to exit the birth canal.

During the period of human growth, the pelvic bones undergo several phases - from the separated three bones (pubic, iliac and ischial), to their gradual fusion. Complete fusion in 2 pelvic or innominate bones is observed at the age of about 25 years. These bones are connected in a circle to other components of the skeleton.

Why is the junction of the pelvis and sacrum immovable?

The complex and non-standard structure of the pelvis is necessary for the implementation of all the functions that the pelvis is endowed with. It really has a lot of features:

1. The pelvis connects the trunk to the lower limbs. In order for a person to walk, sit down and perform other movements normally, this area has true joints.
2. Internal organs are placed in the pelvic cavity, which protect the pelvic bones from blows and other injuries.
3. Support and foundation. The entire body, when walking or other movement, relies only on the pelvic bones. In addition, the pelvis is the basis for the spine.

Precisely because of the need for support, and because man is known as the only upright species of creatures, nature has provided for a fixed connection of the pelvis with the sacrum. The connection occurs so that the sacrum, the beginning of the spine and the pelvis create an axis that maintains balance.

The connection, including the sacroiliac joint and the sacrum with the pelvic bones, is carried out using several ligaments:

1. Iliac-lumbar. Connects the iliac crest and several vertebrae.
2. Sacro-spinous. Attaches the ischium, the horns of the coccyx and the horns of the sacrum.
3. Sacro-tuberous. Acts as a junction of the sacrum, coccyx and ischial tuberosity.

These ligaments are thin, formed into short bundles. The sacrum enters, wedged, into the space between the two pelvic bones and serves as the closure of the pelvic ring. When moving, thanks to a strong ligamentous apparatus, it is always in place.

This immobile connection is considered immobile only conditionally, since there is movement, especially in the region of the iliopsoas ligament. However, the movement is minimal - all ligaments can move no more than 4 °, as for the iliopsoas ligament - it can move up to 8-10 °.

For reference! Mobility in the coccyx is more pronounced in women due to the fact that it must deviate back during childbirth, the movement of the fetus.

If this articulation had greater mobility, upright posture, as well as the integrity of the pelvic ring, would be at risk. Since no movement is needed in this area, the connection is made using strong, short ligaments.