Upper and lower limbs of the human skeleton
The upper limb consists of a girdle and a free limb, which consists of the shoulder (1 bone - humerus), forearm (2 bones - ulna and radius) and hand (wrist - 8 bones, metacarpus - 5 bones and phalanges of the fingers - 14 bones).
The human shoulder girdle is formed by two paired bones: the clavicle and the scapula, which are attached to the chest by muscles and ligaments, and in front by the joint between the clavicle and the handle of the sternum.
The clavicle (clavicula) is an S-shaped curved tubular bone with a body and two ends: the scapular (acromial) and the sternal. At both ends there are articular surfaces for articulation (respectively) with the clavicular notch of the handle of the sternum and the acromial process of the scapula. The clavicle seems to push the shoulder joint to the periphery of the body, providing freedom of movement of the arm.
The scapula is a flat triangular bone. On the dorsal plane of the bone there is a protrusion (spinus) that divides the scapula into the upper and lower parts. The protrusion continues laterally and forward into the acromion, on which there is an articular surface for articulation with the clavicle. The upper edge of the scapula passes into a beak-shaped process, under which is a large notch of the scapula. The lateral angle of the scapula ends with a thickening with an articular fossa. In humans, the scapula is located dorsally, the length has decreased compared to the width.
The long tubular humerus has a body (diaphysis) and two heads (epiphyses). On the upper epiphysis there is a spherical articular surface for articulation with the scapula and a large (lateral) and small (medial) tubercles. From the tubercles, ridges extend downward, between which there is an intertubercular groove (the tendon of the biceps muscle is located here). The lower part of the bone has a triangular shape and ends with a complex articular surface. There are actually two articular surfaces here for articulation with the ulna and radius of the forearm: a block and a spherical head laterally from it.
The body of the long tubular ulna (ulna) resembles a trihedral prism. The upper epiphysis is more massive, has two processes - the ulna (behind, for articulation with the block of the humerus) and the coronal (in front). On the coronal process there is an articular surface for articulation with the radius. On the lower epiphysis of the ulna there is an articular surface for articulation with the radius and a styloid process is located medially.
The upper epiphysis of the long tubular radius bone (radius) has an articular fossa for articulation with the head of the humerus and an articular circle for articulation with the ulna. Next to this head is the tuberosity of the biceps muscle. The distal epiphysis has a carpal articular surface for articulation with the upper (proximal) row of carpal bones and ends with a lateral styloid process. On the medial edge of this epiphysis there is an articular surface for articulation with the ulna.
The lower limb consists of a girdle (represented by the pelvic bones, between which the sacrum is located posteriorly) and a free lower limb. The free limb includes the thigh (femur), lower leg (major and minor tibias) and foot with the metatarsus (7 bones), metatarsus (5 bones) and phalanges of the fingers (14 bones).
The pelvis (os coxae) is a paired flat bone formed by the pubic, iliac and ischium bones, which have fused in the area of the acetabulum - a deep fossa that articulates with the head of the thigh. The ischium and pubic bones limit the large oval-shaped obturator foramen, which is closed by a connective tissue obturator membrane. In front, the pubic bones are connected by a semi-joint - the symphysis. The pelvic bones are connected to the sacrum by the ear-shaped surfaces of the iliac bone, forming a joint.
The femur (os femoris) is the largest tubular bone. The spherical head of the femur, which articulates with the acetabulum of the pelvic bone, has a round ligament fossa on it. The long neck of the bone is located at an angle to it. In men, this angle is obtuse, in women it is almost straight. Under the neck, a large trochanter is located laterally. On the medial side there is a small trochanter. The body of the femur is cylindrical in shape. On its posterior surface there is a tubercle for attaching the rectus muscles of the lower limb. On the lower epiphysis there are two condyles - medial and lateral (on their lateral surfaces there are epicondyles, separated by an intercondylar fossa, which passes into the patellar surface, where the patella abuts).
Patella (patella) - a sesamoid bone that lies in the thickness of the tendon of the 4-headed muscle of the thigh.
The tibia (tibia) articulates with the femur, forming the knee joint. On the upper massive and wide epiphysis there are two condyles with lateral and medial fossae, between which there is an interfossae elevation. The articular surfaces do not correspond in depth to the tubercles of the thigh, therefore there are two cartilaginous menisci. On the lateral surface of the tubercle of the same name there is a fibular articular surface. The body of the tibia is triangular in shape. On its upper part in front there is a tubercle for attaching the 4-headed muscle. The interosseous membrane is attached to the lateral (interosseous) edge. The quadrangular distal epiphysis has a lower articular surface for connecting with the talus of the foot. Its medial (epiphysis) end is retracted and forms the medial .... (taper) On the lateral surface of the lower epiphysis of the tibia there is a fibular notch for articulation with the bone of the same name.
The thin long tubular fibula has an articular surface on the upper epiphysis for articulation with the tibia. The triangular body of the bone ends with a lateral talus, on which there is an articular surface of the talus. The lower articular surface of the tibia and the articular surfaces of the talus form a fork that covers the talus block from above and from the sides.
The bones (skeleton) of the foot (ossa pedis) are connected in such a way as to form an arch. The tarsus is formed by 7 bones: talus, calcaneus, cuboid, navicular and 3 cuneiform. The tibia is connected to the talus. The largest bone is the calcaneus.
The metatarsus consists of 5 short tubular bones. The phalanges of the fingers also belong to the short tubular bones.
The bones of the limbs (except the clavicle) in human ontogenesis go through 3 stages: connective tissue, cartilaginous and bone. In the diaphyses of the tubular bones at the end of the 2nd - beginning of the 3rd month of intrauterine development, primary ossification points are laid, which extend to the epiphyses. In newborns, the epiphyses are cartilaginous, secondary ossification points are laid in them during the first 5-10 years, and the growth of the epiphyses with the diaphyses, as a rule, occurs after 15-18 years, and in girls 1-2 years earlier than in boys.
The joints of bones (arthrology) are usually divided into intermittent and continuous. Continuous connection is provided by connective tissue. It can be fibrous (syndesmosis), cartilaginous (synchondrosis) and bony (growth).
Syndesmosis - ligaments and membranes (interosseous membranes of the forearm and lower leg, yellow ligaments of the vertebral arches and sutures (dentate, scaly and straight). Syndesmosis also includes driving (teeth).
Synchondrosis - cartilage is located between the bones (handle or xiphoid process with the body of the sternum). Bone connections appear when synchondrosis ossifies.
Cartilaginous connections also include half-joints or symphysis. In such cartilages there are cavities that are devoid of a synovial membrane. This type of connection, according to the PNA, includes the intervertebral symphysis, pubic symphysis and symphysis of the handle of the sternum.
Joints are intermittent (synovial) connections of bones that are covered with hyaline cartilage (except for the temporomandibular and sternoclavicular joints - here fibrous cartilage) articular surfaces of bones, joint capsule, cavity, synovial fluid. The thickness of cartilage (0.2 - 6.0 mm) depends on the functional load on the joint. Cartilage is devoid of blood vessels on the cartilage, contains many organic compounds (collagen fibers <gives strength> and proteoglycans <gives elasticity>). On the side of the articular surface, cartilage is covered with a layer of amorphous substance. Lubrication of the articular surfaces is provided by synovial fluid, which is produced by the synovial membrane (the inner layer of the joint capsule). The synovial membrane has many villi and folds, which increases its surface. It is well vascularized, capillaries lie directly under the layer of epithelial cells (secretory synoviocytes), which produce synovial fluid <its amount does not exceed 2-3 ml> (the main component of which is hyaluronic acid). Phagocytic synoviocytes have the properties of macrophages.
The dense outer layer of the joint capsule (fibrous membrane) is attached to the bones near the edges of the articular surfaces and passes into the periosteum. The joint capsule is biologically sealed. It is usually strengthened by extra-articular (in the thickness of the capsule) ligaments. Ligaments not only strengthen the joint, but also direct and limit movements. The pressure in the joint capsule is lower than atmospheric.
The articular surfaces rarely repeat (complement) each other in shape. To achieve congruence (from the Latin congruens - corresponding) in the joints there are a number of auxiliary formations - cartilage discs, menisci, lips, synovial bags and vaginas. For example, in the temporomandibular joint there is a cartilage disc fused with the capsule along the outer edge; in the knee - the semicircular medial and lateral menisci, which are located between the articular surfaces of the femur and tibia; along the edge of the acetabulum there is a lip of the same name, due to which the articular surface of the hip joint deepens and more closely corresponds to the spherical head of the femur. Synovial bursae and sheaths - small cavities of the synovial membrane, which are located in the fibrous membrane (shell) and are filled with synovial fluid. They facilitate the movement of adjacent tendons, ligaments, and bones.
Depending on the number of articular surfaces in the joint, they are divided into simple (two articular surfaces), compound (more than two), complex (between the articular surfaces there is a disc or meniscus, which divides the joint cavity into two compartments), and combined (anatomically distinct joints work as one unit <temporomandibular, intervertebral, costovertebral, etc.>).
The shape of the articular surfaces determines the number of planes in which movements can be performed. Depending on this, joints are divided into single- (cylindrical, block-shaped), double- (elliptical, saddle-shaped) and multi-axial (spherical and flat).
For convenience, the shape of the articular surface is compared with the segment of the body of rotation and on this basis the joints are distinguished: cylindrical (medial atlantoaxial, proximal radioulnar), block-shaped - these are actually cylindrical, but separated by a depression or tubercle (interphalangeal joints of the hands, brachio-ulnar), elliptical (radio-carpal, geniculate <complex>, atlanto-occipital <combined>), saddle-shaped (carpal-metacarpal of the thumb <only in humans>), spherical (brachial, hip), flat (intercarpal, tarsal-metatarsal).
In joints, flexion and extension occur around the transverse axis, abduction and adduction around the sagittal axis, and torsion around the frontal axis.