femoral sheath

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Femoral Sheath

Definition and Formation

The femoral sheath is a funnel-shaped (cone-shaped) sleeve of fascia that surrounds the femoral artery, femoral vein, and associated lymphatics as they pass beneath the inguinal ligament into the femoral triangle. It is formed by:

Anteriorly: transversalis fascia (proper)
Posteriorly/Laterally: iliopsoas fascia (itself a continuation of the transversalis/endoabdominal fascia)
The iliopectineal arch joins the iliopubic tract to contribute to the proximal portion of the sheath

The sheath is continuous superiorly with the transversalis fascia and iliac fascia of the abdomen, and fuses inferiorly with the connective tissue adventitia of the femoral vessels (about 3-4 cm below the inguinal ligament).

- Gray's Anatomy for Students; Mulholland and Greenfield's Surgery, 7e

Compartments (Three)

The femoral sheath is divided into three compartments by internal septa:

Compartment	Position	Contents
Lateral	Most lateral	Femoral artery
Intermediate	Middle	Femoral vein
Femoral canal	Most medial	Lymphatics + connective tissue; Cloquet's node at the ring

The femoral nerve lies lateral to the sheath and is not enclosed within it (it lies in the lacuna musculorum, separated by the iliopectineal arch).

Femoral sheath, ring, and canal - schematic view showing compartments, anterior transversalis fascia, posterior iliopsoas fascia, and the femoral ring contents

Figure: Schematic view of the femoral sheath, ring, and canal - Mulholland and Greenfield's Surgery, 7e

Femoral Canal

The most medial compartment of the sheath
Cone/cul-de-sac shaped, narrowing inferiorly as the medial septum fuses with the femoral vein adventitia
Normally contains only wisps of connective tissue and small lymph nodes
At its proximal (superior) opening = the femoral ring

Femoral Ring

The femoral ring is the extraperitoneal opening (superior mouth) of the femoral canal. Its boundaries:

Anteriorly: inguinal ligament
Posteriorly: iliopubic tract + pectineal (Cooper's) ligament
Medially: curved edge of the transversus abdominis aponeurosis (NOT the lacunar ligament, which inserts more medially)
Laterally: connective tissue septum between femoral ring and femoral vein

The ring contains the node of Cloquet (Rosenmüller's node), a large lymph node.

The canal is not in direct communication with the pelvic cavity because the transversalis fascia is diverted at this point to form the sheath itself, creating a weakened area prone to herniation.

Femoral Triangle Context

Femoral triangle contents - femoral nerve (lateral), artery (middle), vein (medial), lymphatics; in relation to inguinal ligament, sartorius, and adductor longus

Contents of the femoral triangle (Gray's Anatomy for Students)

From lateral to medial in the femoral triangle: Nerve - Artery - Vein - Lymphatics (mnemonic: NAVL)

The femoral artery is palpable just inferior to the inguinal ligament at the midpoint between the ASIS and the pubic symphysis.

Clinical Relevance

1. Femoral hernia The femoral ring/canal is a weak point in the lower abdominal wall. Abdominal contents can herniate through the ring into the femoral canal, producing a femoral hernia - more common in females due to a wider pelvis. Repair involves suturing Cooper's ligament to the femoral sheath.

2. Vascular access The femoral artery and vein within the sheath are accessible just inferior to the inguinal ligament. Used for:

Coronary angiography and angioplasty (arterial access)
Right heart catheterization, pulmonary artery catheters (venous access)
Access to renal, gonadal, cerebral, and thoracic vessels

3. Great saphenous vein The great saphenous vein dips through the fossa ovalis (saphenous opening in the fascia lata), penetrates the femoral sheath, and joins the femoral vein.

4. Surgical dissection To expose the femoral artery and its branches (superficial femoral, profunda femoris), both the fascia lata and the femoral sheath must be divided.

- Gray's Anatomy for Students; Mulholland and Greenfield's Surgery, 7e; Sabiston Textbook of Surgery; Fischer's Mastery of Surgery, 8e

only femoral shealth for 5 marks

Femoral Sheath (5 Marks)

Definition

A funnel-shaped fascial sleeve surrounding the femoral vessels as they pass beneath the inguinal ligament into the femoral triangle.

Formation

Anteriorly - transversalis fascia
Posteriorly - iliopsoas fascia (iliac fascia)
Above - continuous with abdominal fascia
Below - fuses with adventitia of femoral vessels (~4 cm below inguinal ligament)

Compartments (3)

Compartment	Contents
Lateral	Femoral artery
Middle	Femoral vein
Medial (femoral canal)	Lymphatics + Cloquet's node

Note: Femoral nerve lies outside the sheath (lateral to it)

Femoral Canal

Most medial, cone-shaped compartment
Contains lymphatics and connective tissue
Upper opening = femoral ring

Boundaries of femoral ring:

Anteriorly - inguinal ligament
Posteriorly - pectineal (Cooper's) ligament
Medially - lacunar ligament
Laterally - femoral vein

Clinical Significance

Femoral hernia - abdominal contents herniate through the femoral ring into the canal; more common in females
Vascular access - femoral artery/vein used for cardiac catheterization and angiography

- Gray's Anatomy for Students; Mulholland and Greenfield's Surgery, 7e

also add a digram

Femoral Sheath (5 Marks)

Definition

A funnel-shaped fascial sleeve surrounding the femoral vessels as they pass beneath the inguinal ligament into the femoral triangle.

Formation

Anteriorly - transversalis fascia
Posteriorly - iliopsoas fascia (iliac fascia)
Above - continuous with abdominal fascia
Below - fuses with adventitia of femoral vessels (~4 cm below inguinal ligament)

Compartments (3)

Compartment	Contents
Lateral	Femoral artery
Middle	Femoral vein
Medial (femoral canal)	Lymphatics + Cloquet's node

Note: Femoral nerve lies outside the sheath (lateral to it)

Femoral Canal

Most medial, cone-shaped compartment
Contains lymphatics and connective tissue
Upper opening = femoral ring

Boundaries of femoral ring:

Anteriorly - inguinal ligament
Posteriorly - pectineal (Cooper's) ligament
Medially - lacunar ligament
Laterally - femoral vein

Diagram

Femoral sheath, ring, and canal - showing the three compartments separated by septa, with the anterior transversalis fascia, posterior iliopsoas fascia, and the femoral ring contents (Mulholland and Greenfield's Surgery, 7e)

Clinical Significance

Femoral hernia - abdominal contents herniate through the femoral ring into the canal; more common in females
Vascular access - femoral artery/vein used for cardiac catheterization and angiography

- Gray's Anatomy for Students; Mulholland and Greenfield's Surgery, 7e

femoral canal

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Femoral Canal

Definition

The femoral canal is the most medial compartment of the femoral sheath - a short, cone-shaped (cul-de-sac) space that lies medial to the femoral vein, just below the inguinal ligament.

Dimensions

Length: approximately 1.25 cm
Wider above (at the femoral ring), narrows and closes below as it fuses with the adventitia of the femoral vein

Areolar (loose connective) tissue
Lymphatics
Cloquet's node (Rosenmüller's node) - a large lymph node at the femoral ring

Femoral Ring (Upper Opening)

The femoral ring is the abdominal/proximal opening of the femoral canal. It is closed by a thin layer of extraperitoneal fascia (the femoral septum).

Boundaries:

Boundary	Structure
Anteriorly	Inguinal ligament (iliopubic tract)
Posteriorly	Pectineal (Cooper's) ligament
Medially	Lacunar (Gimbernat's) ligament
Laterally	Femoral vein (via its periadventitial septum)

Important: The medial border is the lacunar ligament only in smaller canals; in reality the iliopubic tract forms the anterior/medial boundary in most individuals. The lacunar ligament is more medial still.

Diagram

Femoral canal without iliopubic tract - showing the lacunar ligament (blue arrow) as the medial boundary, with femoral artery (red) and vein (blue) passing beneath the inguinal ligament

Femoral canal (blue arrow = lacunar ligament) - Sabiston Textbook of Surgery

Femoral canal with iliopubic tract (yellow arrows) shown - more lateral than the lacunar ligament, forming the true medial boundary

Femoral canal with the iliopubic tract (yellow arrows) - Sabiston Textbook of Surgery

Function

Allows the femoral vein to expand during increased venous return (e.g., during exercise)
Acts as a potential dead space

Clinical Significance

Femoral Hernia

The femoral ring is a potential weak point in the abdominal wall
Abdominal contents (usually small bowel or omentum) can herniate through the ring into the canal
More common in females due to wider pelvis and broader femoral ring
There is no preformed peritoneal sac - the sac develops as the hernia pushes through
The canal is rigid (bony + ligamentous walls) so strangulation is common

Dangerous Structures at Risk During Repair

Femoral vein - can be compressed by sutures placed too laterally
Anomalous obturator artery (present in ~30%) - may cross the femoral ring medially and be easily cut ("corona mortis" variant)

Repair Principle

Close the femoral ring by suturing Cooper's ligament to the femoral sheath (McVay/Cooper's ligament repair)
Alternatively, a mesh plug is used to obliterate the canal (the ring is relatively rigid and difficult to close with sutures from below)

- Fischer's Mastery of Surgery, 8e; Sabiston Textbook of Surgery; Mulholland and Greenfield's Surgery, 7e

femoral artery with diagram

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Femoral Artery

Definition / Origin

The femoral artery is the direct continuation of the external iliac artery, beginning as it passes under the inguinal ligament to enter the femoral triangle of the anterior thigh.

Surface Marking

Palpable just inferior to the inguinal ligament, at the midpoint between the ASIS and the pubic symphysis (midinguinal point). It bisects the inguinal ligament reliably - this relationship holds even when the pulse is impalpable due to occlusive disease.

Course (Three Segments)

Segment	Location
1. Femoral triangle	Passes vertically downward within the femoral sheath
2. Adductor (Hunter's) canal	Passes inferomedially beneath sartorius between vastus medialis and adductors
3. Adductor hiatus	Passes through the opening in adductor magnus → becomes popliteal artery

Relations in the Femoral Triangle

Lateral: femoral nerve (outside the sheath)
Medial: femoral vein (within the sheath)
In the distal femoral triangle/adductor canal: the femoral vein shifts posterior then posterolateral to the artery

Branches

In the Femoral Triangle (Superficial branches - arise just below inguinal ligament):

Superficial epigastric artery - to lower abdominal wall
Superficial circumflex iliac artery - to skin over iliac crest
Superficial external pudendal artery - to scrotum/labia
Deep external pudendal artery - to perineum

Major Branch:

Profunda femoris artery (Deep artery of thigh) - arises 4-5 cm below the inguinal ligament from the posterolateral aspect; the most important branch
- Medial circumflex femoral artery - main supply to head and neck of femur
- Lateral circumflex femoral artery - ascending, descending, and transverse branches
- 4 perforating arteries - supply posterior thigh (hamstrings)

Terminal Branch:

Descending genicular artery - just before the adductor hiatus; contributes to knee anastomosis

Diagrams

Femoral artery course from inguinal ligament through femoral triangle into adductor canal, showing all branches including superficial epigastric, external pudendal, deep artery of thigh, and termination as popliteal artery at adductor hiatus

Fig 6.65 - Femoral Artery (Gray's Anatomy for Students)

Overview of femoral and popliteal arteries - anterior view showing profunda femoris, circumflex femoral arteries, perforating branches, and continuation as popliteal; posterior view and angiogram

Fig 238.2 - Overview of femoral and popliteal arteries (Fischer's Mastery of Surgery, 8e)

Dissection of femoral artery showing femoral sheath (A), femoral triangle with profunda femoris and perforating arteries (B), and femoral artery in the thigh with saphenous nerve, medial circumflex femoral artery and branches (C)

Fig 238.1 - Dissections of femoral artery: A. Femoral sheath, B. Femoral triangle, C. Thigh (Fischer's Mastery of Surgery, 8e)

Anastomoses

Branches of femoral, inferior gluteal, superior gluteal, and obturator arteries interconnect to form an anastomotic network in the upper thigh and gluteal region - provides collateral circulation if any single vessel is interrupted.

Clinical Significance

Vascular access - femoral artery puncture just below inguinal ligament for cardiac catheterization and angiography
Femoral artery aneurysm - pulsatile groin mass
Peripheral arterial disease - superficial femoral artery most commonly affected segment in the thigh
At-risk nerves during surgery: saphenous nerve and nerve to vastus medialis lie lateral to the artery within the sheath - endangered by excessive lateral dissection

- Gray's Anatomy for Students; Fischer's Mastery of Surgery, 8e

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