| freeze fracture | Method of specimen preparation for the electron microscope in which rapidly frozen tissue is cracked so as to produce a fracture plane through the specimen. The surface of the fracture plane is then shadowed by heavy metal vapour, strengthened by a carbon film and the underlying specimen is digested away, leaving a replica that can be picked up on a grid and examined in the transmission electron microscope. The great advantage of the method is that the fracture plane tends to pass along the centre of lipid bilayers and it is therefore possible to get en face views of membranes that reveal the pattern of Integral membrane proteins. The E face is the outer lamella of the plasma membrane viewed as if from within the cell, the P face the inner lamella viewed from outside the cell. Fracture planes also often pass along lines of weakness such as the interface between cytoplasm and membrane, so that outer and inner membrane surfaces can be viewed. Further information about the structure can be revealed by freeze etching. Extremely rapid freezing followed by deep etching has allowed the structure of the cytoplasm to be studied without the artefacts that might be introduced by fixation. (18 Nov 1997) |
|---|---|
| lefort fracture | <radiology> Types: I transverse fracture through floor of maxillary sinuses (only palate moves), II through maxillary sinuses (pyramidal fracture), III through orbits (craniofacial dysjunction), clinically, may be mixed (12 Dec 1998) |
| Le Fort I fracture | A fracture of the facial bones in which there is a horizontal fracture at the base of the maxillae above the apices of the teeth. Synonym: horizontal fracture, Le Fort I fracture. (05 Mar 2000) |
| Le Fort II fracture | A fracture of the midfacial skeleton with the principal fracture lines meeting at an apex at or near the superior aspect of the nasal bones. Synonym: Le Fort II fracture. (05 Mar 2000) |
| Le Fort III fracture | A complex fracture in which the facial bones are separated from the cranial bones. Synonym: Le Fort III craniofacial dysjunction, Le Fort III fracture, transverse facial fracture. (05 Mar 2000) |
| linear fracture | A fracture running parallel with the long axis of the bone. Synonym: fissured fracture. (05 Mar 2000) |
| linear skull fracture | A skull fracture resembling a line. (05 Mar 2000) |
| lisfranc fracture-dislocation | <radiology> Tarsal-metatarsal fracture-dislocation, trauma, diabetes (neuropathic) (12 Dec 1998) |
| longitudinal fracture | A fracture involving the bone in the line of its axis. (05 Mar 2000) |
| abdominal part of aorta | <anatomy> The largest arterial conduit below the diaphragm. This term refers to the portion of the aorta below the diaphragm to the bifurcation into the right and left common iliac arteries. It supplies blood to the abdominal viscera, pelvic organs and lower extremities. (20 Jun 2000) |
| abdominal part of oesophagus | The part of the oesophagus inferior to the diaphragm. See: oesophagus. Synonym: pars abdominalis oesophagi. (05 Mar 2000) |
| abdominal part of thoracic duct | The part of the thoracic duct between the cisterna chyli and the aortic hiatus of the diaphragm. Synonym: pars abdominalis ductus thoracici. (05 Mar 2000) |
| abdominal part of ureter | The part of the ureter between the renal pelvis and the brim of the pelvis. Synonym: pars abdominalis ureteris. (05 Mar 2000) |
| accessory flower part | <plant biology> Sepal and petal organs found on flowers. The sepals and petals are not essential for pollination but may aid in attracting insects or other organisms. (15 Jan 1998) |
| alar part of nasalis muscle | <anatomy> See: nasalis muscle. Synonym: pars alaris musculi nasalis. (05 Mar 2000) |