Anatomy of bone system. The manual for medical students / Анатомия костной системы. Учебное пособие для медицинских вузов. Г. И. Ничипорук
may be accelerated or decelerated; it depends on the genetic, hormonal and environmental factors. The term «osteal age» is used to assess the process of skeleton development in children. It is determined according to the number of ossification centres in bones and according to the time of their fusion. To evaluate ossification, roentgenography of the hand is made, because the age dynamics of ossification centre appearance and formation of synostosis are very clearly manifested in this part of the body. Ossification centres in carpal bones appear in the following periods:
– at birth, carpal bones are cartilaginous;
– ossification points emerge in the capitate and hamate bones during the first year of life;
– in the triquetral bone – during the third year of life;
– in the lunate bone – during the fourth year of life;
– in the scaphoid bone – during the fifth year of life;
– in the trapezium and trapezoid bones – during the sixth-seventh years of life;
– in the pisiform bone – in the tenth-fourteenth years of life.
Ossifcation of free parts of limbs is given in fig. 1.5.
V.S. Speransky distinguishes the following characteristic features in the ossification process:
1) ossification starts earlier in the connective tissue than in the cartilage;
2) ossification of the skeleton occurs in the cranial-caudal direction;
3) skull ossification spreads from the viscerocranium to the neurocranium;
4) in the free parts of extremities, ossification occurs from the proximal regions to the distal areas.
Fig. 1.5. Periods of ossification of free parts of limbs in male (Alexina L.A., 1985, 1998)
Osteal age does not always coincide with the passport age. In some children, the ossification process terminates 1–2 years earlier than it happens normally, in others – 1–2 years later. Starting from the age of 9 years, sexual differences of ossification can be distinguished clearly – in girls this process occurs more rapidly.
Body growth in girls terminates mainly at the age of about 16–17 years, in boys – at about 17–18 years. After this age, body growth in length is no more than 2 %.
In old age, bone rarefication termed osteoporosis occurs in different parts of the skeleton. In tubular bones, osseous tissue dissolves inside the diaphysis, as a result, the medullary cavity becomes wider.
At the same time, calcium salts are accumulated, and osseous tissue is developed on the outer surface of the bone, under the periosteum. Quite often, in places of attachment of ligaments and tendons, bony outgrowths called osteophytes develop. They also emerge along the edges of articular surfaces. In elderly persons, bone durability considerably decreases, and even minor injuries may cause fractures.
Skeleton ageing is characterized by individual changeability. In some persons, ageing symptoms appear as early as at the age of 35–40 years, in other persons – only after 70. Skeleton ageing symptoms are more manifested in women than in men. But this process significantly depends on the complex of factors: genetic, climatic, hormonal, alimentary (nutritive), functional, ecological etc.
1.9. Anomalies of Bone Development
1. Osteomalacia – disorder of calcification of newly formed osseous tissue which is caused by deficiency in calcium or vitamin D.
2. Osteoporosis – disorder of formation of the bony matrix during the skeleton formation (insufficient compensation of resorbed bone tissue). It occurs in elderly and old age and is caused by exessive resorption of osseous tissue.
3. Ectopic osteogenesis – ossification of soft tissues in abnormal places (in walls of arteries, kidneys etc.)
TEST QUESTIONS
1. What function does the skeleton carry out?
2. Name the types and functions of the bone marrow.
3. List the principles of the bone classification.
4. Give the characteristic of the primary and secondary bones.
5. What organic and inorganic substances are included into the composition of the bone (in what ratio)?
6. What connective tissue structure covers the bone from outside? What is its function?
7. What is the structural unit of osseous tissue? Name the types of osteocytes.
CLINICOANATOMICAL PROBLEM
During the surgical operation in a 10-year-old patient the metaepiphysial cartilage which separates the head of humerus from the body of humerus, was radically removed. What is the prognosis?
2. SKELETON OF TRUNK
The skeleton of trunk consists of the vertebral column, or backbone, columna vertebralis, and the thorax, cavea thoracis (thorax).
The vertebral column in an adult person consists of 24 individual vertebrae, sacrum and coccyx. There are the cervical vertebrae (7), thoracic (12) and lumbar ones (5) distinguished in the vertebral column. The sacrum consists of five fused sacral vertebrae. The coccyx consists of 3–5 fused coccygeal vertebrae. The thorax consists of 12 pairs of ribs with corresponding thoracic vertebrae and the sternum.
2.1. General Vertebral Features
The vertebra, vertebra, is comprised of the vertebral body, corpus vertebrae, anteriorly, the vertebral arch, arcus vertebrae, posteriorly and vertebral processes, processus vertebrae. The vertebral body is anterior and supporting part of the vertebra. The arch is located behind the vertebral body. The vertebral arch is attached to the body with the help of two pedicles of vertebral arch, pediculi arcus vertebrae, thus bounding the vertebral foramen, foramen vertebrale (fig. 2.1).
The foramina of all vertebrae form the vertebral canal, canalis vertebralis, enclosing the spinal cord. Openings for blood vessels named nutrient foramina, foramina nutricia, are visible on the surface of the vertebral body.
Seven processes project from the vertebral arch. An unpaired spinous process, processus spinosus, projects dorsally along the median line. The paired transverse processes, processus transversus, project on the right and on the left in the frontal plane. The paired superior and inferior articular processes, processus articularis superior et processus articularis inferior, project up and down from the arch. The bases of the articular processes bound the superior and inferior vertebral notches, incisura vertebralis superior et incisura vertebralis inferior. The inferior notches are deeper than the superior ones. When the vertebrae are articulated with each other, the inferior and superior notches form an intervertebral foramen, foramen intervertebrale, on the right and on the left. The intervertebral foramina transmit spinal nerves and blood vessels.
Fig. 2.1. Thoracic vertebra:
a – lateral aspect: 1 – vertebral body (corpus vertebrae); 2 – superior costal demi-facet (fovea costalis superior); 3 – superior vertebral notch (incisura vertebralis superior); 4 – superior articular process (processus articularis superior); 5 – transverse process (processus transversus); 6 – transverse costal facet (fovea costalis processus transversi); 7 – spinous process (processus spinosus); 8 – inferior articular process (processus articularis inferior); 9 – inferior vertebral notch (incisura vertebralis inferior); 10 – inferior costal demi-facet (fovea costalis inferior)
b – superior aspect: 1 – spinous process (processus spinosus); 2 – vertebral arch (arcus vertebrae); 3 – pedicles of vertebral arch (pediculi arcus vertebrae); 4 – superior costal demi-facet (fovea costalis superior); 5 – superior articular process (processus articularis superior); 6 – transverse costal facet (fovea costalis