line
(līn 
)
[L. linea, string, thread]
- A narrow straight mark.
- A boundary, edge, or outline.
- A wrinkle.
- An imaginary anatomical line used as a stand ard of reference.
- A catheter attached to a patient, e.g., an intravenous line or an arterial line.
abdominal l.Any of the stand ard imaginary surface lines delineating abdominal regions.
SEE: abdominal regions.
absorption l.A black line in the continuous spectrum of light passing through an absorbing medium.
ala-tragus l.An imaginary line that extends from the ala of the nose to the tragus of the ear. The line is an estimated point of entry for intraoral dental radiographs of the maxilla and is also used in denture prosthodontics.
arcuate l.1The lower edge of the iliac fossa of the ilium. The arcuate line is a continuation of the pectineal line of the pubis, and it continues up and back along the ilium to merge with the edge of the sacral ala and then the sacral promontory. The continuous bony ridge, of which the arcuate line is one segment, encircles the pelvic inlet and is called the pelvic brim.2On the internal surface of the anterior abdominal wall, below the level of the umbilicus, the inferior edge of the posterior layer of the rectus sheath. At this level, the inferior epigastric vessels enter the sheath and run along the underside of the rectus abdominis muscles.
SEE: under Arlt line.
arterial l.A hemodynamic monitoring system consisting of a catheter in an artery connected to pressure tubing, a transducer, and an electronic monitor. It is used to measure systemic blood pressure and to provide ease of access for the drawing of blood (as in intensive care, when regular monitoring of blood gases is necessary).
auriculobregmatic l.The line from the auricular point to the bregma.
axial l.A line running in the main axis of the body or a body part, such as a limb. For example, the axial line of the hand runs longitudinally through the middle digit; the axial line of the foot runs longitudinally through the second digit.
axillary l.Any of the imaginary lines that extend in parallel down the side of the body from the axilla. These lines are the anterior axillary line, the midaxillary line, and the posterior axillary line.
base l.An imaginary cephalometric line from the infraorbital ridge through the middle of the external auditory meatus to midline of occiput.
SEE: baseline.
basiobregmatic l.The line from the basion to the bregma.
SEE: under Baudelocque, Jean-Louis.
SEE: Beau line.
biauricular l.A line over the vertex from one auditory meatus to the other.
SEE: Burton line.
canthomeatal l.An imaginary cephalometric line extending from the lateral canthus of the eye to the center of the external auditory meatus.
cement l.The edge of a secondary (new) osteon. It contains glycoproteins and proteoglycans and has little or no collagen.
central l.A venous access device inserted into and kept in the vena cava, innominate, or subclavian veins. It is used to infuse fluids and medicines or for gaining access to the heart to measure pressures in the venous circulation. Keeping the line open permits later venous access when the veins might be collapsed and difficult to enter.
SEE: central venous catheter.
SEE: central venous catheter; central line.
cervical l.1A line of junction of cementum and enamel of a tooth.2A line on the neck of the tooth where the gum is attached.
costoarticular l.The line from sternoclavicular joint to a point on the 11th rib.
costoclavicular l.The line midway between the nipple and the border of the sternum.
Variant: demarcation line
The dividing line between healthy and diseased tissue.dentate l.On the luminal wall, the transition zone between the anal canal and the rectum. Inside the anal canal, the anal valves are located along the pectinate line; outside the anal canal, the superficial portion of the external anal sphincter is located at the pectinate line. The pectinate line marks where, in the embryo, two separate epithelia (the endoderm of the developing hindgut and the ectoderm of the invaginating proctodeum) meet and fuse. SYN: pectinate line.
Variant: Douglas line
SEE: under Douglas, James.
ectental l.The junction in the gastrula of the endoderm and ectoderm.
epiphyseal l.A line marking the junction of the epiphysis and diaphysis of a long bone. It is the remnant of the epiphyseal disk.
SEE: Feiss line.
Variant: fixation line
Visual linefrown l.A permanent skin fold or wrinkle between the eyebrows or near the corners of the mouth that develops as a result of repeated use of underlying muscles and aging.
glabelloalveolar l.An imaginary line through the glabella on the frontal bone and the alveolar process of the maxilla.
glabellomeatal l.An imaginary line that extends from the glabella to the center of the external auditory meatus and is used for radiographical positioning of the skull.
gluteal l.Any of three lines (the posterior, the anterior, or the inferior gluteal) that are bony ridges on the posterior (exterior) surface of the ilium parallel to the iliac crest. The posterior gluteal line runs along the outer edge of the iliac crest and marks the upper edge of the origin of the gluteus medius muscle. The anterior gluteal line has the same contour as the iliac crest but runs a few centimeters lower and marks the upper edge of origin of the gluteus minimus muscle. The inferior gluteal line has a contour similar to, but fainter than, the other gluteal lines, it runs a few centimeters above the acetabulum, and it marks the lower edge of the origin of the gluteus minimus muscle on the ilium.
SEE: gumline.
SEE: under Hilton, John.
iliopectineal l.The segment of the pelvic brim from the pubic symphysis to the sacrum, including the pubic crest, the pectineal line, and the arcuate line.
incremental l.Any of the lines seen in a microscopic section of tooth enamel. They mark the sequential layers of added enamel, similar to the growth lines in a tree.
SEE: under Retzius, Magnus Gustaf.
incremental l. of von Ebner Very light lines in the dentin of a tooth that represent the boundary between the layers of dentin produced daily.
inferior nuchal l.On the posterior outer surface of the occipital bone, a ridge extending laterally from either side of the greater occipital crest 1 to 2 cm below the greater external occipital protuberance and curving slightly upward at its end.
ABBR: IOML
An imaginary line from the inferior orbital margin to the external auditory meatus, used for radiographical positioning of the skull.interauricular l.An imaginary cephalometric line passing through the left and right external auditory meatus.
intercondylar l.The transverse ridge joining condyles of the femur above the intercondyloid fossa.
intermediate l. of ilium The ridge on the crest of the ilium between the inner and outer lips.
ABBR: IPL
An imaginary horizontal line drawn between the centers of the pupils of the eyes. The length of the line is the interpupillary distance.intertrochanteric l.A roughened circumferential ridge at the base of the neck of the femur interconnecting the greater and lesser trochanters.
intertuberal l.The line joining the inner borders of the ischial tuberosities below the lesser sciatic notch.
SEE: major dense line.
SEE: Langer lines.
lateral canthal l.Skin folds or wrinkles that form at the temporal sides of the eyes. Also technically known as lateral canthal rhytids. Colloquially known as “crow’s feet.”
lateral supracondylar l.Either of two ridges on the posterior surface of the distal end of the femur, formed by diverging lips of the linea aspera. It is one of the proximal attachments of the vastus lateralis muscle of the quadriceps.
SEE: medial supracondylar line.
lead l.An irregular dark line in the gingival margin. The line is present in chronic lead poisoning and is caused by the deposition of lead in that portion of the gum.SYN: blue line.
lip l.The highest or lowest point the lips reach on the teeth or gums during a broad smile.
M l.In high power micrographs of striated muscle, the thin, dark line in the center of the H band of a sarcomere. It contains myomesin (a protein that connects thick (myosin) filaments), C protein, and creatinine kinase. SYN: M band ; M disk.
magnetic l. of force The lines indicating the direction of the magnetic force in the space surrounding a magnet or constituting a magnetic field.
major dense l.In electron microscopic images of myelin sheaths, the compacted cytoplasmic side of the Schwann cell membranes, which alternates in multiple layered sheaths with tightly opposed external membrane surfaces called the minor dense line or the intraperiod line. SYN: period line.
SEE: intraperiod line.
mammillary l.An imaginary line through the center of the nipple along the long axis of the breast.
marionette l.The indentation in the facial skin that runs from the corner of each side of the mouth, to the corner of the chin. The line tends to deepen with age. One element of plastic surgery to rejuvenate the face is to eliminate this line with natural or artificial fillers.
medial supracondylar l.Either of two ridges on the posterior surface of the distal end of the femur, formed by diverging lips of the linea aspera.
SEE: lateral supracondylar line.
median l.An imaginary vertical line dividing the body (or one of its parts) into a right and a left side.
mentomeatal l.An imaginary line from the mental point of the mand ible to the external auditory meatus, used in radiography of the skull.
midclavicular l.An imaginary longitudinal line through the middle of the clavicle, used for describing locations on the trunk. At its top, it passes through the midpoint of the clavicle, and on a male, it runs just medial to the nipple. It crosses the costal margin near the end of the 9th costal cartilage and it extends to the thigh, passing through the fold of the groin halfway between the anterior superior iliac spine and the symphysis pubis. At one point, the milk line (mammary line) intersects the midclavicular line.
milk l.A longitudinal line along each side of the chest and abdomen of mammals marking the location of the mammary ridge of the embryo. Mammary gland s and nipples (both normal and supernumerary) develop along the milk line. The milk line and the midclavicular line intersect at one point. SYN: mammary line.
SEE: mammary ridge.
mucogingival l.Mucogingival junction
mylohyoid l.A ridge on the inner surface of the mand ible. It extends from a point beneath the mental spine upward and back to the ramus past the last molar. The mylohyoid muscle and the superior constrictor muscle of the pharynx attach to this ridge.
nasal l.A line from the lower edge of the ala nasi curving to the outer side of the orbicularis oris muscle.
nasobasilar l.A line through the basion and nasion.
neonatal l.A prominent incremental line in the tooth enamel and dentine made partly after birth. The line indicates infant survival for at least a few days after birth.
nuchal l.The inferior or the superior nuchal line.
oblique l. of fibula The medial crest of posteromedial border; a line extending from the medial side of the head and terminating distally at the interosseous crest.
oblique l. of mand ible On the outside of the body of the mand ible, a ridge continuing from the line of the anterior border of the mand ibular ramus. As it passes the region below the first molar, the oblique line curves forward and runs (below the mental foramen) parallel to the lower edge of the mand ible; it finally disappears into the mental tubercle. The oblique line marks the attachments of several muscles: the depressor labii inferioris, the depressor anguli oris, and parts of the platysma.
oblique l. of radius The faint ridge on the anterior surface passing inferolaterally from the radial tuberosity.
oblique l. of thyroid cartilage A line running obliquely across the external surface of each of the two laminae of the thyroid cartilage. Three muscles attach to this ridge: the sternothyroid, the thyrohyoid, and the thyropharyngeus portion of the inferior pharyngeal constrictor.
oculozygomatic l.A line appearing between the inner canthus of the eye and the cheek, supposedly indicative of neural disorders.
orbitomeatal l.The imaginary line running through the outer (lateral) canthus of the eye and the ipsilateral external auditory meatus. It is commonly used for radiographic positioning.
l. of Owen Any of the occasional prominent growth lines or band s in the dentin of a tooth. They provide a record of the growth of the coronal or radicular dentin.
parasternal l.The line midway between the midclavicular line and the ipsilateral border of the sternum.
pectineal l.1A ridge along the upper edge of the superior ramus of the pubis (pubic bone) extending from the pubic tubercle to the ilium, where it continues as the arcuate line. Together, the pectineal line and the arcuate line form the iliopectineal line, which is a large portion of the pelvic brim.SYN: pecten pubis.2 A short, rough ridge on the posterior surface of the femur extending downward from the lesser trochanter to the linea aspera. The pectineus muscle attaches to this ridge.
popliteal l. of femur An oblique line on the posterior surface of the femur.
popliteal l. of tibia A line on the posterior surface of the tibia, extending obliquely downward from the fibular facet on the lateral condyle to the medial border of the bone.
pure l.1The progeny of a single homozygous individual obtained by self-fertilization.2The progeny of an individual reproducing asexually by simple fission, or by buds, runners, or stolons.3The progeny of two homozygous individuals reproducing sexually.
resting l.A smooth cement line seen in microscopic sections of bone; it marks a place where bone growth stopped temporarily and then resumed.
reversal l.A cement line seen in microscopic sections of bone that shows scallops and irregularities representing earlier bone resorption. Resorption to that point occurred before the process reversed and new bone was formed by apposition.
SEE: Howship lacuna.
scapular l.In anatomical descriptions, an imaginary vertical line parallel to the midline and passing through the tip of the inferior angle of the scapula when the ipsilateral arm is hanging at the side of the body.
SEE: under Schwalbe, Gustav Albert.
SEE: linea semilunaris.
SEE: Shenton line.
sight l.An imaginary line from the center of the pupil to a viewed object.
soleal l.A roughened diagonal line on the posterior surface of the upper quarter of the tibia. It descends from the back of the tibial tuberosity to the medial edge of the shaft of the tibia. Part of the soleus muscle originates from the soleal line.
SEE: spigelian line.
sternal l.An imaginary vertical midline passing through the sternum.
sternomastoid l.A line connecting the midpoint of the heads of the sternocleidomastoid muscle and the mastoid process of the temporal bone.
superior nuchal l.On the posterior outer surface of the occipital bone, a ridge extending laterally from either side of the greater occipital protuberance and curving slightly downward at its end.
supraorbital l.The line across the forehead above the root of the exterior angular process of the frontal bone.
sylvian l.A line on exterior of the cranium, marking direction of the sylvian fissure.
temporal l.Either of two lines, the superior or the inferior temporal. The superior temporal line is an arching ridge along the lateral surface of the skull; it begins as a continuation of the upper posterior border of the zygomatic bone and continues as a broad arch along the frontal and parietal bones, above and roughly parallel to the upper edge of the temporal bone. The inferior temporal line begins with the superior temporal line and separates from its lower edge to form a parallel but tighter and lower arch. The inferior temporal line marks the origin of the temporalis muscle; the superior temporal line marks the attachment of the muscle's fascia.
temporal l. of frontal bone A line from the posterior edge of the zygomatic process of the frontal bone, curving up and back, dividing into the superior and inferior temporal lines.
umbilicopubic l.The portion of median line extending from the umbilicus to the symphysis pubis.
visual l.An imaginary line connecting the fovea of the eye to the object being viewed. SYN: line of fixation; visual axis.
warm l.Any means of communication that provides access to consultative or managerial services, typically within several hours or a day.
SEE: hotline.
SEE: linea alba.
Z l.Regular dark striations visible in high power micrographs of skeletal muscle fibers. Z lines mark the ends of sarcomeres and are the anchors for the sarcomere's actin filaments. SYN: Z band .
SEE: Z disk.
Zöllner l.Parallel lines, usually three long ones, with a series of short lines drawn at regular intervals across one of the lines at approx. 60°. Similar lines are drawn across the second line at the angle of approx. 120°. Short lines are drawn across the third at the same angle as on the first lines. These lines produce the optical illusion that the long lines are converging or diverging.