Page 70 - Clinical Anatomy

ECA2 7/18/06 6:42 PM Page 55

Surface anatomy and

surface markings

Be able to identify these landmarks on yourself or the patient (Fig. 42).
The xiphoid. The costal margin extends from the 7th costal cartilage at
the xiphoid to the tip of the 12th rib (although the latter is often difficult
to feel); this margin bears a distinct step, which is the tip of the 9th costal
cartilage.
The iliac crest ends in front at the anterior superior spine from which
the inguinal ligament (Poupart’s ligament) passes downwards and medially
to the pubic tubercle. Identify this tubercle by direct palpation and also
by running the fingers along the adductor longus tendon (tensed by
flexing, abducting and externally rotating the thigh) to its origin at the
tubercle.
Feel the firm vas deferens between the finger and thumb as it lies within
the spermatic cord at the scrotal neck. Trace the vas upwards and note that
it passes medially to the pubic tubercle and thence through the external
inguinal ring, which can be felt by invaginating the scrotal skin with the
fingertip.

Vertebral levels (Fig. 42a)

•◊◊T9—the xiphoid.
•◊◊L1 — the transpyloric plane of Addison lies half-way between the supra-
sternal notch and the pubis, or approximately a hand’s breadth below
the xiphoid. This plane passes through the pylorus, the pancreatic
neck, the duodenojejunal flexure, the fundus of the gall-bladder,
the tip of the 9th costal cartilage (felt as a distinct ‘step’), and the hila
of the kidneys. It also corresponds to the level of termination of the spinal
cord.
•◊◊L3 — the subcostal plane, a line joining the lowest point of the thoracic
cage on each side, which is the inferior margin of the 10th rib. It passes
through the origin of the inferior mesenteric artery
•◊◊L4—the plane of the iliac crests. This corresponds to the level of the bifur-
cation of the aorta. It is also a useful landmark in performing a lumbar
puncture, since it is well below the level of the termination of the spinal
cord, which is approximately at L1 (see page 338).
•◊◊The umbilicus is an inconstant landmark. In the healthy adult it lies at
the junction of L3 and L4 vertebrae. It is lower in the infant and, naturally,
when the abdomen is pendulous. It is higher in late pregnancy.

Surface markings (Fig. 42b)
The abdominal viscera are inconstant in their position but the surface
markings of the following structures are of clinical value.
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