High-yield map
Key points before the detail
- 01
The femoral nerve is outside the femoral sheath.
- 02
The femoral canal is medial to the femoral vein.
- 03
The lacunar ligament forms the medial boundary of the ring; the femoral vein forms the lateral boundary.
- 04
Division near the lacunar ligament can endanger an aberrant obturator vessel or corona mortis.
Femoral sheath and compartments
Below the inguinal ligament, the femoral sheath encloses the proximal femoral artery and vein and a medial potential space: the femoral canal. The femoral nerve lies lateral to the sheath, which is an important distinction in both examination and procedural anatomy.
| Compartment | Main content |
|---|---|
| Lateral | Femoral artery |
| Intermediate | Femoral vein |
| Medial | Femoral canal: loose tissue, lymphatics and the deep inguinal node of Cloquet |
Femoral ring boundaries
| Boundary | Structure |
|---|---|
| Anterior | Inguinal ligament |
| Posterior | Pectineal ligament and fascia over pectineus |
| Medial | Lacunar ligament |
| Lateral | Femoral vein |
Why the canal exists
The canal is not an empty defect. Its loose tissue allows the femoral vein to expand when venous return increases, and it transmits lymphatics and a deep inguinal node. This explains why obliterating or narrowing the medial sheath indiscriminately could compromise nearby venous anatomy.
Why femoral hernias are dangerous
A femoral hernia enters through the femoral ring, descends in the canal and may then present through the saphenous opening. The neck is narrow and bounded by firm structures, so bowel or omentum can become trapped and its blood supply compromised.
- A groin lump below and lateral to the pubic tubercle is the classic surface relationship.
- Do not use surface position alone to exclude a complicated hernia in an acutely ill patient.
Repair hazards
| At-risk structure | Why it matters |
|---|---|
| Femoral vein | Immediately lateral to the ring; careless lateral dissection can injure it. |
| Aberrant obturator vessel / corona mortis | May cross near the lacunar ligament and can bleed significantly if divided. |
| Bladder | Can be close to preperitoneal approaches, particularly when distended or anatomically variant. |
| Bowel | May be contained within the hernia sac and must be assessed for viability when strangulation is suspected. |
Active recall
Close the notes and answer these
Try each question from memory before revealing the answer. These public prompts are a small preview of the integrated retrieval system inside SurgAtlas.
01What are the four boundaries of the femoral ring?
Anterior inguinal ligament, posterior pectineal ligament/pectineus fascia, medial lacunar ligament and lateral femoral vein.
02What lies in the femoral canal?
Loose connective tissue, lymphatics and the deep inguinal node of Cloquet; the space also permits femoral-vein expansion.
03Which important structure is outside the femoral sheath?
The femoral nerve.
Sources & editorial basis
References & editorial basis
- SurgAtlas production chapter — Anatomy — Abdomen I and Lower Limb I. Primary source for this public lesson. The teaching has been condensed from the corresponding production chapter without changing the underlying anatomical relationships.
- Last’s Anatomy: Regional and Applied. Reference for stable groin and femoral-triangle anatomy.
This lesson is derived from the corresponding SurgAtlas production teaching material. Where the source makes current management or guideline claims, the public lesson uses the cited contemporary guidance. It is written for education and examination preparation, not as patient-specific clinical advice.
Editorial details
Medical Doctor (MD) · MRCS Part A · Physician · Surgical Educator
SurgAtlas is an educational resource. For patient care, verify current national guidance, local antimicrobial and transfusion policies, specialty pathways and individual patient factors.
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