Anatomy Terms Starting With F

Fascia is a continuous sheet or band of dense connective tissue that envelops, separates, and connects muscles, organs, and neurovascular structures throughout the body.

Superficial fascia lies beneath the skin, blending with the dermis and housing fat, cutaneous nerves, and blood vessels; deep fascia is a tougher, less extensible layer that wraps individual muscles and muscle groups, forming compartments. Fascial compartments in the limbs can develop dangerously elevated pressures after trauma or reperfusion, a surgical emergency called compartment syndrome that requires immediate fasciotomy to prevent muscle necrosis and nerve damage. Research over the past two decades has identified fascia as a mechanosensory tissue containing fibroblasts, free nerve endings, and Ruffini corpuscles that transmit proprioceptive signals and respond to mechanical loading.

Cadaveric dissection studies have shown that tension applied to one fascial region can be detected mechanically several centimeters away, supporting the concept of myofascial force transmission across body segments.

Femur is the single long bone of the thigh and the longest, strongest bone in the human body, transmitting body weight from the hip to the knee.

The femoral head articulates with the acetabulum of the pelvis to form the hip joint; the distal femur articulates with the tibia and patella at the knee. Between these two joints, the neck-shaft angle of approximately 126 degrees positions the knee under the body’s center of gravity, a geometry that supports efficient bipedal locomotion. Hip fractures through the femoral neck are among the most serious injuries in elderly people, carrying mortality rates of up to 30 percent within one year, largely because immobility after fracture accelerates cardiovascular and pulmonary complications.

Bone density in the femoral neck declines with age and is measured clinically by dual-energy X-ray absorptiometry to assess osteoporosis risk before fracture occurs.

Fibula is the slender lateral bone of the lower leg that runs parallel to the tibia, provides attachment sites for multiple muscles, and forms the lateral malleolus of the ankle mortise while bearing only a small fraction of body weight.

Proximally, the fibula articulates with the tibia just below the knee at the proximal tibiofibular joint; distally, the lateral malleolus projects downward and posteriorly to form the outer boundary of the ankle mortise, bracing the talus against inversion and lateral displacement. Although the fibula bears only approximately 10 percent of lower limb load during standing, with the tibia carrying the remaining 90 percent, it provides attachment for the fibularis longus, fibularis brevis, soleus, extensor digitorum longus, and extensor hallucis longus muscles. Lateral malleolus fractures are the most common ankle fractures in both athletic and trauma populations, and even isolated fibular fractures can destabilize the ankle mortise if the associated ligaments are torn.

Surgeons frequently harvest a segment of the fibular shaft as a vascularized bone graft for reconstructing the mandible or other long bones, exploiting the fact that its removal does not compromise walking when the ankle joint remains intact.

Filtration in the kidney is the process by which blood pressure forces water, ions, and small solutes across the glomerular capillary wall into Bowman's capsule to form the glomerular filtrate.

Filtration is driven by the net filtration pressure, which is the hydrostatic pressure of glomerular blood minus the osmotic pressure of plasma proteins and the capsular hydrostatic pressure. Three layers form the glomerular filtration barrier: the fenestrated capillary endothelium, the glomerular basement membrane, and the podocyte filtration slits, which together exclude proteins and cells from the filtrate. A healthy adult’s glomerular filtration rate is approximately 125 mL per minute, producing 180 liters of filtrate per day, over 99% of which is reabsorbed downstream.