Human Anatomy - Lecture Notes - Savchuk O.I. 2017

Vertebral Column and Thoracic Cage - Skeleton of the Trunk

Lecture outline

1. Structure OF THE vertebrae

2. JOINTS OF THE vertebrae

3. THE Vertebral Column as a whole

4. Structural Features of the I-II cervical vertebrae.

The Skeleton of the Trunk includes the vertebral column and the bones forming The thoracic cage.

Vertebral column.

The spine serves as the body's support and acts as a flexible axis for the trunk. In humans, the vertebral column consists of 33-34 vertebrae. The last 9 vertebrae fuse to form the sacrum and coccyx. The vertebral column is divided into the following regions: cervical (7 vertebrae), thoracic (12 vertebrae), lumbar (5 vertebrae), sacral (5 vertebrae), and coccygeal (4-5 vertebrae).

Structure of the vertebrae

All vertebrae, except for the I and II cervical vertebrae, share a similar structure; specifically, each vertebra has an anteriorly directed body from which an arch extends. The body and the arch enclose the vertebral foramen. When the vertebrae are stacked on top of one another, these foramina form the vertebral canal, which houses the Spinal Cord. This canal communicates with the cranial cavity through the foramen magnum (Occipital bone).

The vertebral arch is attached to the body by the pedicles of the vertebral arch, where the superior and inferior vertebral notches are located. These notches form the intervertebral foramina, through which the Spinal Nerves pass. Processes project from the arch of each vertebra: vertical ones (upward and downward) — the superior and inferior articular processes (paired); posterior — the spinous process (unpaired); and lateral — the transverse processes (paired).

Cervical vertebrae. A characteristic feature of the cervical vertebrae is the presence of a foramen in the transverse processes, and the spinous process is bifid (except for V). The first cervical vertebra, called the atlas, lacks a body and a spinous process, consisting only of two arches (anterior and posterior) and lateral masses, which bear articular facets (superior and inferior) for articulation with the occipital bone and the II cervical vertebra. The second cervical vertebra has a body with an upward-projecting dens (odontoid process) for articulation with the anterior arch of the atlas. The VII cervical vertebra (vertebra prominens) has a long, non-bifid spinous process. These vertebrae can be counted to locate the site for puncture during subdural anesthesia.

Thoracic vertebrae. A characteristic feature of the thoracic vertebrae is the presence of costal facets on the lateral surfaces of the body and transverse processes for articulation with the HEAD and tubercle of the rib.

Lumbar vertebrae have a massive body because they bear a heavy load, and they also feature accessory processes.

Sacral vertebrae are referred to as false vertebrae because they fuse into a single bone, the sacrum. It features an anterior (pelvic) and a posterior (dorsal) surface, a base (directed upward), and an apex (directed downward). On the posterior surface, There are five crests: the median, and the paired medial and lateral crests. These are formed by the fusion of the spinous, transverse, and articular processes. On the pelvic surface, the superior border of the body of the I sacral vertebra and the inferior border

of the body of the V lumbar vertebra form a projection called the promontory, which obstetricians use to determine pelvic dimensions. Running inside the sacrum is the sacral canal, formed by the fusion of the sacral vertebrae. The lateral PARTS OF THE sacrum feature an auricular surface for articulation with the hip bone. There are also pelvic sacral foramina.

Coccygeal vertebrae. The coccygeal region of the human spine corresponds to the tail of vertebrate animals. The coccygeal vertebrae also fuse into a single bone, the coccyx. Occasionally, children are born with a tail-like appendage.

TYPES OF JOINTS between vertebrae

All types of joints are found between the vertebrae, namely:

✵ syndesmoses — the anterior and posterior longitudinal ligaments;

✵ synchondroses — the intervertebral discs between the vertebral bodies;

✵ synostoses — the sacral vertebrae fused into the sacrum;

✵ diarthroses — the joints between the superior and inferior articular processes of the vertebrae.

Each disc is shaped like a biconvex lens, the peripheral part of which is formed by fibrocartilage, with its fibers forming the annulus fibrosus, while the central part consists of an elastic substance called The Nucleus pulposus. The bodies of adjacent vertebrae are joined together by the annulus fibrosus. The nucleus pulposus, located inside the annulus fibrosus and compressed by the bodies of adjacent vertebrae, acts as a Shock absorber.

Along the vertebral column, the vertebral bodies and intervertebral discs are connected by the anterior and posterior longitudinal ligaments. The transverse processes and spinous processes are also connected by ligaments (interspinous ligaments). Running over the tips of the spinous processes is the long supraspinous ligament, which in the cervical region becomes the nuchal ligament.

Between the first cervical vertebra and the occipital bone, the right and left atlanto-occipital joints are formed; they are combined in structure, ellipsoidal in shape, and biaxial in function. Movements in these joints are possible around the frontal (flexion and extension) and sagittal (abduction and adduction) axes.

In the cylindrical atlanto-axial joint, head rotation to the right and left takes place. During this, the atlas rotates around the dens of the II cervical vertebra together with the Skull.

The vertebral column as a whole

The adult vertebral column has curvatures. A distinction is made between physiological and pathological curvatures.

Physiological curvatures include:

1) Lordosis - a curvature with its convexity facing forward. There are cervical and lumbar lordoses. They develop in a child when they begin to hold their head up and walk.

2) Kyphosis - a curvature with its convexity facing backward. There are thoracic and sacral kyphoses. They develop as the child begins to sit.

In healthy individuals, there is normally also a slight lateral curvature of the spine - Scoliosis. It arises due to the greater Development of the musculature on one side of the body (on the right in right-handed people, on the left in left-handed people). In older age, thoracic kyphosis increases. Pathological changes caused by diseases can lead to The formation of a hump.

Spinal curvatures cushion shocks and vibrations to the body during walking, running, and jumping.

The following movements are possible in the vertebral column: flexion and extension, abduction and adduction (lateral bending), and so-called rotation (twisting).

The thoracic cage

The thoracic cage is formed by 12 pairs of Ribs, the unpaired breastbone (Sternum), and the thoracic vertebrae.

Ribs

Ribs are narrow, long, curved flat bones. They are classified into true ribs (the upper seven), which attach directly to the sternum with their anterior ends; false ribs (VIII, IX-X), which connect via their cartilages to the Cartilage of the preceding rib, only occasionally reaching the sternum, and form the costal arch; and floating ribs (XI, XII), whose anterior ends terminate freely in the Muscles of the anterolateral abdominal wall.

Each rib consists of a posterior bony part and an anterior costal cartilage. The bony part has a head, a neck, and a shaft (body). In the upper 10 pairs of ribs, a tubercle is located between the neck and the shaft. The shaft features outer and inner surfaces, as well as superior and inferior borders. On the inner surface of the inferior border, the costal groove is visible, where Vessels and nerves run. Therefore, during pleural puncture, the needle must be inserted along the superior border of the rib.

The first rib, unlike all others, has superior and inferior surfaces, and outer and inner borders. On its superior surface, there is the scalene tubercle (the attachment site of the scalene Muscle). Posterior to the tubercle lies the groove for the Subclavian Artery, and anterior to it is the groove for the subclavian vein.

Sternum

The sternum is a flat bone consisting of three parts: the manubrium, the body, and the xiphoid process. The body is joined to the manubrium at an obtuse angle. On the superior border of the manubrium, there is the jugular notch, flanked by the clavicular notches. Costal notches are visible on the lateral borders of the manubrium and the body of the sternum. Unlike other bones, the sternum contains a large amount of Cytology/practical/86.html">Red Bone Marrow (hence sternal punctures are performed in Blood diseases). Red bone marrow transplants are also performed here in cases of radiation sickness.

The sternum contains a large amount of spongy (cancellous) bone with a highly developed vascular network, which allows for intraosseous blood transfusion.

Articulations of the thoracic cage

With their posterior ends (heads), the ribs articulate with the thoracic vertebrae to form the joints of the head of the rib. The tubercles of the ribs articulate with the transverse processes to form the costotransverse joints. These are combined joints, in which elevation and depression of the ribs occur. The anterior ends of the upper seven pairs of ribs articulate with the sternum. The first rib forms a synchondrosis with the sternum, while the next six form synovial joints (diarthroses); the VIII, IX, and X ribs connect to each other via synchondroses to form the costal arch.

The thoracic cage as a whole

The thoracic cage encloses the thoracic cavity, which contains Internal Organs such as the Lungs, etc. The shape of the thoracic cage depends on sex, age, body build, and physical development. It can be wide and short (hypersthenic) or long and narrow (asthenic).

The superior thoracic aperture is bounded by the body of the I thoracic vertebra, the first pair of ribs, and the manubrium of the sternum; the inferior thoracic aperture is bounded by the XII thoracic vertebra, the costal arches, and the xiphoid process. It is closed by the Diaphragm. In women, the thoracic cage is shorter than in men.

The right and left costal arches form the infrasternal angle, which opens downward. The shape of the thoracic cage can be affected by past illnesses. For instance, Rickets can result in a Pigeon chest (pectus carinatum) or a barrel chest.

Movements of the rib cage during breathing are uneven because the lower ribs are longer and more curved. In the upper chest, so-called costal breathing is observed, where the thoracic cavity expands sagittally during inhalation, while the lower chest simultaneously expands transversely (abdominal breathing).

The first rib has limited mobility, resulting in insufficient ventilation of the lung apex (which is why tuberculosis primarily affects the apices of the lungs).

The following imaginary lines are distinguished on the outer surface of the chest wall:

✵ Anterior median line;

✵ Parasternal line;

✵ Midclavicular line;

✵ Anterior, mid-, and posterior axillary lines;

✵ Scapular line;

✵ Paravertebral line;

✵ Posterior median line.

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