fold
(fōld 
)
- A ridge or a crevice formed when a flexible surface doubles back on itself. SYN: plica.
- A bend, as in a polypeptide that determines its in-situ three-dimensional structure.
- A particular three-dimensional folded shape assumed by a polymer, such as a protein.
- A thin, doubled sheet extending from a tissue or a cell.
amniotic f.In the gastrula stage of the embryo, a small fold of embryonic ectoderm and mesoderm that begins extending into the proamniotic cavity and eventually gives rise to the amnion and the chorion.
aryepiglottic f.Each of the two lateral folds of the inlet to the larynx, which are the top edges of the quadrate membranes. These folds are ridges composed of mucous muscle fibers and fibrocartilage ligaments. They lie behind the thyroid cartilage and extend downward from the sides of the epiglottis anteriorly to the tops of the arytenoid cartilages posteriorly. Near their posterior ends, each fold surrounds a small cuneiform cartilage and then a corniculate cartilage.
axillary f.Either of two folds (anterior axillary fold, posterior axillary fold) of skin-covered muscle along the sides of the chest where the underside of each arm meets the shoulder. The anterior axillary fold is formed by the lateral edge of the pectoralis major muscle; the posterior axillary fold, by the lateral edges of the latissimus dorsi and teres major muscles.
circular f.Any of the transverse folds around the inner wall of the small intestine. The circular folds (plicae) are soft ridges of mucosa that protrude into the intestinal lumen. These folds are largest and closest together in the duodenum distal to the major duodenal papilla; they decrease in height and number through the distal jejunum, and they disappear in the distal ileum.
Variant: epicanthic fold
Epicanthus.gastric f.Any of the mostly longitudinal folds of mucosa found in the empty stomach.
SEE: ruga.
genital f.A fold of skin in the embryo on each side of the genital tubercle that develops into the labia minora in females.
glossoepiglottic f.One of three mucous membrane folds between the base of the tongue and the epiglottis.
gluteal f.The linear fold in the skin that separates the buttocks from the thighs and marks the inferior limits of the gluteus maximus muscle.
inframammary f.The lower border of the breast where it meets the chest wall. SYN: submammary fold.
infraorbital f.A line that forms in the skin under the swollen eyelids of patients with atopic dermatitis. SYN: atopic pleat; Dennie-Morgan fold.
mucobuccal f.Along the back wall of the mouth, the fold of oral mucosa that runs from the maxilla (superiorly) or the mand ible (inferiorly) to the cheek.
mucosal f.A fold of mucosal tissue.
nail f.A fold in the skin surrounding the margins and proximal edges of the nail.
neural f.In the early embryo, the raised lateral edges of the neural plate. The neural folds are thickened ridges of epithelium that are pushed up and meet in the midline as the neural plate curls into a longitudinal tube. These folds are transition zones between the neural tissue in the neural plate and the surrounding surface ectoderm and give rise to the neural crest cells and to ectodermal placodes.
rectouterine f.Douglas cul-de-sac.
Variant: skinfold
A doubling of skin and its underlying adherent subcutaneous tissue. To assess a person's body fat, a skin fold is pinched at a stand ard site, and the thickness of the doubled skin is measured with skin fold calipers. A body fat estimate is calculated by a table or a computer program. There are between 6 and 12 stand ard locations for measuring skin fold thickness, e.g., over the triceps muscle along the back of the arm, or just above the iliac crest of the hip.submammary f.Inframammary fold.
SEE: urogenital ridge.
ventricular f.False vocal cord
vestigial f.The ligament of the left side of the superior vena cava.
vocal f.The lower pair of folds that project into the midsection of the larynx; these define the lower boundary of the laryngeal vestibule. Each vocal fold is composed of whitish, stratified squamous epithelium covering the vocal ligament. The protruding vocal folds create the narrowest cross-section of the larynx and form the edges of the rima glottidis.
During a strong inspiration, the vocal folds are pulled farther apart to widen the opening into the trachea. During swallowing, the vocal folds are pulled together to protect the trachea. During phonation, the vocal folds are pulled together, and airflow causes them to vibrate and make a sound; the pitch of this sound can be changed by varying the tension on the vocal ligaments.
SYN: true vocal cord; vocal cord.SEE: false vocal cord.