Femoral Triangle

Boundaries

• Gray's Anatomy for Students

Contents

1. Femoral nerve (L2-L4) - lateral; lies outside the femoral sheath
2. Femoral artery - continuation of the external iliac artery, enters under the inguinal ligament; palpable midway between ASIS and pubic symphysis
3. Femoral vein - medial to the artery
4. Femoral canal (lymphatics + deep inguinal lymph nodes, including the node of Cloquet/Rosenmüller) - most medial

Femoral Sheath

• Gray's Anatomy for Students, p. 675-676

Detailed Neurovascular Anatomy

Femoral Artery

• Continuation of the external iliac artery below the inguinal ligament
• Gives off the profunda femoris (deep artery of the thigh) in the triangle - the main blood supply to the thigh
• Also gives: superficial epigastric artery, superficial circumflex iliac artery, superficial and deep external pudendal arteries
• At the apex, passes into the adductor canal (Hunter's canal), exiting as the popliteal artery through the adductor hiatus

Femoral Vein

• Medial to the femoral artery
• Receives the great saphenous vein at the saphenous opening (fossa ovalis)
• Receives tributaries corresponding to the branches of the femoral artery

Femoral Nerve (L2, L3, L4)

• Largest branch of the lumbar plexus
• Enters the thigh lateral to the femoral artery, outside the femoral sheath
• Within or just below the triangle, divides into anterior and posterior divisions:
  • Anterior: cutaneous branches to the anteromedial thigh (medial and intermediate femoral cutaneous nerves)
  • Posterior: motor to quadriceps femoris and rectus femoris; gives off the saphenous nerve (continues into adductor canal)

Adductor Canal (Hunter's Canal)

• Femoral artery and vein
• Saphenous nerve
• Nerve to vastus medialis

Surface Anatomy and Clinical Relevance

Pulse point

• Pulse palpation
• Femoral artery catheterization (angiography, cardiac catheterization, angioplasty)
• Femoral venous access (for right heart catheterization, pulmonary artery catheterization, dialysis)

Femoral Hernia

• Protrusion of abdominal contents through the femoral ring into the femoral canal
• More common in women (wider pelvis, wider femoral ring)
• Presents as a mass below and lateral to the pubic tubercle (distinguishing it from inguinal hernias, which are above and medial to the pubic tubercle)
• High risk of strangulation due to the rigid boundaries of the femoral ring

Inguinal Lymphadenopathy

Lumbar Plexus Blocks / Femoral Nerve Block

Summary Table

Histology of Cartilage

General Properties

• No blood vessels, lymphatics, or nerves - nutrients reach chondrocytes entirely by diffusion through the matrix
• The ECM's high glycosaminoglycan (GAG) content binds large amounts of water (60-80% of cartilage net weight), enabling this diffusion and providing resilience under compression
• Surrounded by a perichondrium (except articular cartilage and epiphyseal plates)

The Cells: Chondroblasts and Chondrocytes

• Rounded/ovoid cells with a central nucleus, prominent nucleolus
• Cytoplasm contains abundant rough ER (rER), Golgi apparatus, lipid droplets, and glycogen - reflecting high secretory activity
• Do not divide readily in mature cartilage (limited repair capacity)
• Chondrocytes that have recently divided remain clustered together as isogenous groups (cell nests) - 2-8 cells sharing a single lacuna

The Extracellular Matrix

Molecular Composition of Hyaline Cartilage (Fig. 7.2)

• Type II collagen - predominant (80% of all collagen); forms thin 20-nm fibrils creating a tension-resisting meshwork
• Type IX - links fibrils to proteoglycan molecules
• Type XI - regulates fibril diameter
• Type X - organizes fibrils into a 3D hexagonal lattice (important for mechanical function)
• Type VI - concentrated in the capsular matrix (pericellular zone); anchors chondrocytes to the matrix via integrin receptors

• Aggrecan is the major proteoglycan. Each aggrecan monomer has a core protein with many attached GAG chains (chondroitin sulfate and keratan sulfate)
• Aggrecan monomers bind to hyaluronan via link proteins to form enormous proteoglycan aggregates
• These aggregates are highly hydrated and enable cartilage to bear compressive loads

• Fibronectin, decorin, laminin - mediate cell-matrix adhesion

Matrix Zones Around Chondrocytes

Types of Cartilage

1. Hyaline Cartilage

• Matrix appears glassy/homogeneous ("hyaline" = glassy) on H&E - type II collagen fibrils are invisible because they have the same refractive index as the surrounding ground substance
• Chondrocytes in lacunae, often in isogenous groups
• Surrounded by perichondrium (except articular cartilage and epiphyseal plates)
• Matrix stains basophilic with H&E (due to sulfated GAGs) and metachromatic with toluidine blue

• Articular surfaces of synovial joints
• Costal cartilages (ribs)
• Larynx (thyroid, cricoid, arytenoid cartilages)
• Tracheal rings and bronchial plates
• Nasal cartilages
• Fetal skeleton (precursor to most bones via endochondral ossification)
• Epiphyseal growth plates

Special Structure: Articular Cartilage

2. Elastic Cartilage

• Identical to hyaline cartilage in basic organization (chondrocytes in lacunae, isogenous groups, perichondrium present)
• Matrix additionally contains dense networks of branching and anastomosing elastic fibers and lamellae
• Elastic fibers are not visible on H&E - require special stains: orcein or resorcin-fuchsin stain them brown/dark

• Pinna (auricle) of the external ear
• External acoustic meatus
• Eustachian (auditory) tube
• Epiglottis
• Vocal folds (corniculate and cuneiform cartilages)

• Gives elasticity and flexibility in addition to the resilience of hyaline cartilage
• Does NOT calcify with aging (unlike hyaline cartilage)
• Has perichondrium

3. Fibrocartilage

• A combination of dense regular connective tissue + hyaline cartilage
• Chondrocytes are scattered singly, in rows, or in small isogenous groups amid thick bundles of type I collagen fibers
• Much less ground substance than hyaline cartilage
• No perichondrium
• Two cell populations visible: chondrocytes (round nuclei, small halo of amorphous matrix in lacunae) and fibroblasts (flattened/elongated nuclei within the fibrous areas)

• Intervertebral discs (annulus fibrosus)
• Pubic symphysis
• Menisci of the knee
• Articular discs (e.g., temporomandibular, sternoclavicular joints)
• Tendon and ligament insertions (entheses)

• Type I and type II collagen (unlike pure hyaline which is type II only)
• Resists both compression and tension - suited to sites of high mechanical stress
• Proportions of type I:type II vary by site and change with age (more type II in older individuals due to ongoing chondrocyte activity)
• No perichondrium; transitions directly into adjacent connective tissue

Summary Comparison Table

Perichondrium

• Outer (fibrous) layer: dense irregular connective tissue with type I collagen fibers and fibroblasts; provides tensile strength
• Inner (chondrogenic) layer: contains chondroprogenitor cells (chondroblasts) that produce new cartilage during appositional growth

Cartilage Growth

1. Appositional growth - new cartilage added at the surface by differentiation of chondroblasts from the inner perichondrium; transcription factor SOX-9 drives this differentiation
2. Interstitial growth - chondrocytes divide within their lacunae and produce new matrix around themselves, expanding cartilage from within; prominent during fetal development

Repair

• Avascularity (no vascular inflammatory response)
• Immobility and low mitotic activity of mature chondrocytes
• Matrix as a barrier to cell migration