Musculoskeletal system

Evolutionary heritage and developmental anomalies

The formation of the human musculoskeletal system is closely linked to the phylogenesis of chordates. Specific anatomical phenomena serve as evidence of this:

• Vestiges (rudimentary organs) are structures that have lost their primary significance but are present in all representatives of a species. These include the coccyx (tail remnant), wisdom teeth, appendix, Darwin's tubercle on the auricle, and swimming webs.
• Atavisms are traits of distant ancestors that are normally lost but sporadically appear in individual humans. Examples include the presence of a tail, supernumerary nipples (polymastia, polythelia), or dense hair growth (hypertrichosis).

The basis for the appearance of atavistic defects is the disruption of the reduction of ancient structures during early embryogenesis (e.g., at the neurula stage, when the axial skeleton is laid down).

Biomechanics and anatomy of the spine

The spinal column consists of the cervical, thoracic, lumbar, sacral, and coccygeal regions. The presence of physiological curves (cervical and lumbar lordoses, thoracic and sacrococcygeal kyphoses) turns it into a springy system capable of cushioning vertical loads.

A typical vertebra consists of a body, an arch, and processes (spinous, transverse, articular). However, the cervical region has exceptions: the first vertebra (atlas) lacks a body and is formed by two arches, and the vertebral arteries pass through the transverse processes of all cervical vertebrae.

The functional unit is the vertebral segment, which combines two adjacent vertebrae, the intervertebral disc (with the annulus fibrosus and nucleus pulposus), and the ligamentous apparatus.

The foot: functions and deformities

The foot performs four key functions: support, shock absorption, balancing, and propulsion. Its architecture relies on a system of arches:

1. Lateral longitudinal (supportive) arch — formed by the calcaneus, cuboid, IV, and V metatarsal bones. It contacts the surface, providing rollout during walking.
2. Medial longitudinal (shock-absorbing) arch — includes the talus, navicular, cuneiform, and the first three metatarsal bones. It does not touch the support and absorbs impacts.
3. Transverse arch.

The most frequent pathology (over 60% of cases) is static deformities resulting from muscle and ligament weakness, especially in people whose jobs involve standing. In transverse flatfoot, the biomechanics of the step are severely impaired: pressure on the head of the first metatarsal bone drops to 14%, overloading the middle metatarsals.

Pelvic injuries: diagnostics and risks

Pelvic ring fractures are fraught with severe complications. In the acute period, shock, massive blood loss, fat embolism, and internal organ damage are possible. The risk of urethral rupture is particularly high in bilateral fractures of the pubic and ischial bones.

Ultrasound is mandatory for diagnostics. If urinary tract injury is suspected, retrograde urography is performed in strict sequence, followed (if no pathology is detected) by excretory cystourethrography.

The absence of adequate bone reposition leads to persistent pain, gait disturbances, deforming arthrosis, and, in sacral injuries, impairment of pelvic functions and impotence.

Receptor apparatus

Neuroregulation of movements and maintenance of posture are impossible without a developed network of receptors. According to their anatomical organization, they are divided into:

• Primary — sensitive dendritic endings (proprioceptors, pain, tactile, temperature). The neuron body is located in a spinal or cranial ganglion (e.g., ganglion geniculi).
• Secondary — have a specialized cell connected to the dendrite via a synapse (gustatory, vestibular, photoreceptors).

Pain receptors (nociceptors) are free nerve endings that respond to mechanical, thermal, and chemical stimuli such as histamine, bradykinin, potassium ions, and hydrogen ions.

Class and exam questions

What else to study on this topic

• Embryological evidence of the animal origin of humans (biogenetic law).
• Surgical correction of hand deformities: corrective osteotomies and muscle transposition.
• Classification of receptors by modality and the mode of perceiving an adequate stimulus.
• Structural features of the cervical spine and craniovertebral junction.
• Walking biomechanics: a detailed analysis of the stance and swing phases.

Other topics in the "Additional Topics" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.