Topographic lines and body regions

Natural anatomical landmarks

In clinical practice, the physician always relies on visually noticeable or easily palpable body structures. These include the bony elements of the chest, shoulder girdle, pelvis, and spine, as well as various natural depressions in the soft tissues.

• Sternum and ribs: The sternum consists of the manubrium, body, and xiphoid process. The most important clinical landmark is the sternal angle, the site where the manubrium joins the body. This angle is easily palpable on the patient's chest as a characteristic transverse ridge. It is to this angle that the cartilage of the second (II) rib attaches. Having palpated the angle and the second rib, the physician moves slightly lower to find the second intercostal space. This is a critically important zone, as auscultation (listening) of the aortic and pulmonary valves is performed here. The clavicles, scapulae, and costal margins also serve as useful landmarks.
• Spine: The main reference point on the back is the spinous process of the seventh cervical vertebra (C7), which protrudes most prominently when the patient's head is bent forward. The other spinous processes are also used for vertical navigation.
• Pelvis: In the lower part of the torso, the landmarks are the iliac crests, the pubic symphysis, and the anterior superior iliac spine, which is easily palpable beneath the skin.
• Soft tissues and fossae: To determine organ projections, clinicians actively use the jugular notch (located directly above the sternal manubrium), supraclavicular and infraclavicular fossae, axillary fossae, and intercostal spaces.

Topography of the anterior abdominal wall

To accurately describe the localization of pain or the location of internal organs, the anterior abdominal wall is conventionally divided into nine zones (regiones). First, the abdomen is divided into three horizontal floors using two lines:

1. Intercostal line (upper): A horizontal line connecting the lowest points of the costal margins. If projected onto the spine, it passes precisely along the upper edge of the third (III) lumbar vertebra.
2. Interspinous line (lower): A horizontal line connecting the anterior superior iliac spines. Its projection onto the spine corresponds to the level of the second (II) sacral vertebra.

These two lines form three abdominal floors:

• Upper — epigastrium (epigastrium).
• Middle — mesogastrium (mesogastrium).
• Lower — hypogastrium (hypogastrium).

Next, each of the three floors is intersected by two vertical lines running strictly along the outer (lateral) edges of the rectus abdominis muscles. The intersection results in 9 regions:

• Median (unpaired) regions: Located along the central axis. These are the epigastric region proper (in the upper floor), the umbilical region (regio umbilicalis, around the navel in the middle floor), and the pubic region (regio pubica, above the symphysis in the lower floor).
• Lateral (paired) regions: To the right and left of the central axis lie the hypochondriac regions (regio hypochondriaca), the lateral abdominal regions or flanks (regio lateralis), and the inguinal or iliac regions (regio inguinalis / iliaca).

An additional zone outside the anterior abdominal wall is distinguished separately—the lumbar region (regio lumbalis), which corresponds to the projection of the lumbar spine and kidneys from the patient's back.

Topographic lines of the chest

To detail the projection of thoracic cavity organs onto the body surface, a system of conventional vertical lines encircling the chest is used.

Lines of the anterior and lateral surface:

• Anterior median line (linea mediana anterior) — runs strictly vertically through the middle of the sternum.
• Sternal line (linea sternalis) — projected along the lateral (side) edge of the sternum.
• Midclavicular line (linea medioclavicularis) — drawn through the middle of the clavicle. It is important to remember that it does not always coincide with the nipple line (linea mamillaris); in clinical practice, these landmarks must be strictly distinguished.
• Parasternal line (linea parasternalis) — bisects the distance between the sternal and midclavicular lines.

On the lateral surface, the landmark is the axillary fossa, through which three lines pass:

• Anterior axillary line (linea axillaris anterior) — runs along the anterior edge of the fossa, anatomically corresponding to the edge of the pectoralis major muscle.
• Midaxillary line (linea axillaris media) — descends from the deepest central point of the fossa.
• Posterior axillary line (linea axillaris posterior) — runs along the posterior edge of the fossa, coinciding with the edge of the latissimus dorsi muscle.

Lines of the posterior surface:

• Posterior median line (linea mediana posterior) — projected precisely along the spinous processes of the thoracic vertebrae.
• Scapular line (linea scapularis) — passes through the inferior angle of the scapula. Important condition: the patient's arm must be lowered along the torso.
• Paravertebral line (linea paravertebralis) — located exactly midway between the spinous processes of the vertebrae and the scapular line.

Class and exam questions

What else to study on this topic

• Projection of internal organs onto the 9 abdominal regions.
• Topography of lung lobes along the chest lines.
• Determination of heart borders on the anterior chest wall.
• Methods of palpation and percussion using topographic landmarks.

Other topics in the section «Patient Examination Methods»

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