Surface Anatomy Landmarks
On this page
Direct answer
One palpable ridge — the sternal angle of Louis at the manubriosternal joint — anchors the whole thorax: it marks the second costal cartilage, so all rib counting starts there, and its plane at the T4–T5 disc marks the bifurcation of the trachea, the beginning and end of the arch of the aorta, the crossing of the thoracic duct from right to left and the entry of the azygos vein into the superior vena cava. In the abdomen the transpyloric plane of Addison, halfway between the suprasternal notch and the pubic symphysis at L1, carries the pylorus, the neck of the pancreas, the hila of the kidneys, the duodenojejunal flexure, the origin of the superior mesenteric artery and the termination of the spinal cord. These two planes, with the mid-inguinal point and McBurney's point, convert the body surface into an examination grid.
What you must remember
- Sternal angle inventory: second costal cartilage on both sides, aortic arch begins and ends, tracheal bifurcation and carina, thoracic duct crossing and azygos termination.
- Transpyloric plane (L1) inventory: pylorus of stomach, neck of pancreas, renal hila, duodenojejunal flexure, fundus of gallbladder, origin of the superior mesenteric artery and the conus medullaris of the cord.
- Vertebral level pairs worth memorising: C4 — bifurcation of the common carotid artery at the upper border of the thyroid cartilage; C6 — cricoid cartilage, beginning of the oesophagus and larynx's lower limit, vertebral artery entering its foramen transversarium; T4 — sternal angle; L1 — transpyloric plane and renal hilum; L4 — aortic bifurcation and the intercristal line; L5 — beginning of the inferior vena cava.
- Anterior abdominal points: mid-inguinal point (ASIS to symphysis) — femoral artery; midpoint of the inguinal ligament (ASIS to pubic tubercle) — deep inguinal ring; McBurney's point — junction of the medial two-thirds and lateral third of the spinoumbilical line, maximal tenderness of appendicitis; Lanz point — junction of the right and middle thirds of the interspinous line.
- Cardiac surface anatomy: apex beat in the fifth left intercostal space at the midclavicular line, about 8 to 9 cm from the midsternal line; auscultation — aortic valve at the second right intercostal space, pulmonary at the second left, tricuspid at the lower left sternal border, mitral at the apex.
- Gallbladder and kidney: fundus of the gallbladder at the tip of the ninth costal cartilage where the lateral border of rectus abdominis crosses it; kidneys from T12 to L3, the right lower by half a level.
- Back landmarks: spinous process of T3 opposite the spine of the scapula and T7 its inferior angle; the dimples of Venus over the posterior superior iliac spines mark S2 and the middle of the sacroiliac joint.
Landmarks at the bedside
Run three procedures through the grid. For a femoral line, palpate the mid-inguinal point between the anterior superior iliac spine and the pubic symphysis; confusing it with the midpoint of the inguinal ligament, which marks the deep inguinal ring, misplaces the needle lateral to the target. For a chest drain, count down from the second space at the sternal angle to the fifth intercostal space just anterior to the midaxillary line, passing the drain over the lower rib to spare the neurovascular bundle of the subcostal groove. For a lumbar puncture, the intercristal line across the highest points of the iliac crests marks L4, and the space above or below is chosen; in a caudal block the sacral cornua and hiatus are palpated below the dimples of Venus at S2. An appendicectomy incision centres on McBurney's point along skin creases.
Level-matching drills
Screening papers frame this region as one structure paired with one level, and the errors are always the neighbouring distractors: the aortic bifurcation offered at L3, the conus medullaris offered at L3, the carotid bifurcation at C6 — each one level off the truth. The transpyloric plane list is quoted as a five-option single-best answer in which the duodenojejunal flexure or the renal hila are the recurring answers.
Frequently asked questions
What does the sternal angle mark?
The manubriosternal joint at the T4–T5 disc, where the second costal cartilage articulates, the trachea bifurcates, the aortic arch begins and ends, the thoracic duct crosses to the left and the azygos vein joins the superior vena cava.
What structures lie at the transpyloric plane?
The pylorus, pancreatic neck, renal hila, duodenojejunal flexure, gallbladder fundus, origin of the superior mesenteric artery and the conus medullaris, all at the L1 vertebral level.
Which landmark guides the level for lumbar puncture?
The intercristal (Tuffier) line joining the highest points of the iliac crests crosses approximately the L4 spine, so the L3–L4 or L4–L5 interspace is chosen below the conus medullaris.
Where are the mid-inguinal point and the midpoint of the inguinal ligament, and what do they mark?
The mid-inguinal point halfway between the ASIS and pubic symphysis marks the femoral artery; the midpoint of the inguinal ligament between the ASIS and pubic tubercle marks the deep inguinal ring.
Where is the apex beat normally palpated?
In the fifth left intercostal space at the midclavicular line, about 8 to 9 cm from the midsternal line.