Infraclavicular region (Regio infraclavicularis)
Anatomically, this zone belongs to the chest and upper extremity, while in topographical anatomy it is considered part of the shoulder girdle (pectoral girdle). Its layers participate in the formation of the axillary fossa, which is directly adjacent to the main neurovascular bundle of the upper limb.
Boundaries of the region:
- Superior: clavicle.
- Inferior: horizontal line at the level of the third intercostal space.
- Medial: lateral edge of the sternum.
- Lateral: anterior edge of the deltoid muscle (m. deltoideus).
An important landmark is the infraclavicular fossa (Mohrenheim's fossa). It is localized below the clavicle, at the border of its outer and middle thirds, between the clavicular part of the pectoralis major muscle and the deltoid muscle. Distally, the fossa transitions into the deltopectoral groove (sulcus deltopectoralis). In the depth of this groove, 1.5–2 cm below the clavicle, the coracoid process of the scapula (processus coracoideus) can be palpated. The pectoralis minor muscle (m. pectoralis minor) is projected here as a small triangle extending from the anterior ends of ribs III–V to the coracoid process.
Frontoparietooccipital region
This extensive zone unites the first three unpaired regions of the cranial vault due to their similar anatomical structure. Anteriorly, it is bounded by the supraorbital margin of the frontal bone and the glabella, posteriorly by the superior nuchal line, and laterally by the superior temporal line.
Layered structure:
- Skin: thick, immobile, hair-covered, rich in sebaceous and sweat glands.
- Subcutaneous adipose tissue (SAT): has a cellular structure due to fibrous septa. Important neurovascular bundles pass here: supraorbital, supratrochlear, superficial temporal, occipital, and posterior auricular vessels and nerves, as well as the temporal branch of the facial nerve.
- Musculo-aponeurotic layer: includes the occipitofrontalis muscle and the epicranial aponeurosis (galea aponeurotica). The skin, SAT, and aponeurosis are firmly connected into a single layer, which accounts for the scalped nature of wounds during trauma.
- Subaponeurotic tissue: loose, devoid of septa, which is why the inflammatory process here is always diffuse in nature.
- Periosteum and subperiosteal tissue: the periosteum is loosely connected to the bone (except at the suture lines), therefore subperiosteal abscesses are limited to the boundaries of a single bone.
- Bones of the cranial vault: belong to flat bones and consist of a durable outer table, spongy substance (diploë), and a very fragile inner ("glassy") table. The dura mater (dura mater), which forms the venous sinuses, lies tightly against the inner surface of the bones.
Dorsum of the hand and temporal region
Dorsal surface of the hand has a number of topographical features. The first metacarpal bone is located at an angle to the others, forming the widest intermetacarpal space, where the convexity of the first dorsal interosseous muscle (m. interosseus dorsalis I) is visualized. The skin here is thin and mobile, containing hair follicles (which creates a risk for the development of furuncles). The subcutaneous tissue is very loose — this is a favorite site for the accumulation of edematous fluid, including during purulent processes on the palm.
A dense venous network forms in the subcutaneous layer of the hand. On the radial side, the cephalic vein (v. cephalica) originates, accompanied by the superficial branch of the radial nerve (ramus superficialis n. radialis). On the ulnar side, the basilic vein (v. basilica) forms, running together with the dorsal branch of the ulnar nerve (ramus dorsalis n. ulnaris).
Temporal region (Regio temporalis) is a paired zone on the lateral surface of the head, corresponding to the projection of the temporal fossa of the cranium. It is of immense importance in maxillofacial surgery: a powerful masticatory muscle is located here, large superficial blood vessels pass through, and local fascial spaces communicate directly with the deep areas of the face.
To easily remember the pattern of pus spread on the cranial vault, pay attention to the density of the layers: in the cellular subcutaneous tissue, abscesses are localized; in the loose subaponeurotic tissue, they are diffuse; and in the subperiosteal tissue, they are strictly limited to the boundaries of a single bone (the suture line).
Class and exam questions
Where is the coracoid process of the scapula palpated?
It is palpated in the depth of the deltopectoral groove, approximately 1.5–2 cm below the clavicle.
Why are scalp wounds often of a scalped nature?
This is due to the fact that the first three layers (skin, subcutaneous tissue, and epicranial aponeurosis) are firmly fused by fibrous septa and strip off from the underlying tissues as a single monolithic layer upon trauma.
How is the joint space of the metacarpophalangeal articulations projected?
The joint space is located 8–10 mm distal (inferior) to the heads of the metacarpal bones.
Why does edema from inflammation on the palm often manifest on the dorsum of the hand?
On the dorsal surface of the hand, the subcutaneous tissue is very loose, so edematous fluid easily accumulates precisely there, even if the primary inflammatory focus is located on the palmar side.
What else to study on this topic
- Topography and sources of formation of the neurovascular bundles of the frontoparietooccipital region.
- Structure of the cranial vault bones: diploic veins, glassy table, and frontal sinus.
- Fascial spaces of the temporal region and their connection with deep facial structures.
- Syntopy of subcutaneous veins and nerves at the border with the dorsal wrist region.
- Projection and practical significance of Mohrenheim's fossa in operative surgery.
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