pars plana

pars pla·na (pln)

n.

See ciliary disk.

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pars

pl. partes [L.] a division or part.

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pars ciliaris retinae

see ciliary body.

pars distalis

the major part of the anterior lobe of the pituitary gland, the adenohypophysis. It is separated from the neurohypophysis by the intraglandular cleft, the residual lumen of Rathke's pouch.

pars disseminata

the thin layer of the prostate that surrounds the urethra; as distinct from the body of the gland.

pars flaccida

the small, triangular portion of the tympanic membrane lying between the lateral process of the malleus and the margins of the tympanic incisure.

pars infundibularis

the neural stalk that connects the neurohypophysis with the hypothalamus.

pars intermedia

the part of the adenohypophysis consisting of a layer of cells contiguous with the neurohypophysis. The source of melanocyte-stimulating hormone.

pars iridica retinae

see iris¹.

pars longa glandis

the long, cylindrical part of the dog glans; distinct from the bulbar part.

pars major uteri

the section of the bird's oviduct in which the egg is held while the shell is formed.

pars mastoidea

the mastoid portion of the temporal bone, being the irregular, posterior part.

pars nervosa

of the pituitary gland. See neurohypophysis.

pars optica retina

the large, posterior part of the retina which contains the nervous elements of rods, cones and optic nerve fibers.

pars petrosa

the petrous portion of the temporal bone, containing the inner ear.

pars pigmentosa

the pigmented part of the retina.

pars plana

the thin flat part of the ciliary body; the ciliary disk.

pars plicata

the folded part of the ciliary body.

pars pylorica

distal segment of the stomach or abomasum, curved behind the omasum.

pars pylorica ventriculi

the distal (aboral) third of the stomach.

pars squamosa

the flat, scalelike, anterior and superior portion of the temporal bone.

pars tensa

the drumlike part of the tympanic membrane.

pars tuberalis

a layer of cells surrounding the neural stalk of the pituitary gland and forming part of the adenohypophysis.

pars tympanica

the tympanic portion of the temporal bone, forming the anterior and inferior walls and part of the posterior wall of the external acoustic meatus.

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ciliary body 

Part of the uvea, anterior to the ora serrata and extending to the root of the iris where it is attached to the scleral spur. It comprises the ciliary muscle and the ciliary processes and is roughly triangular in sagittal section. The whole ciliary body forms a ring. The part just beyond the ora serrata is smooth and is thus known as pars plana (orbiculus ciliaris). Anterior to this lies a region of ridges, which are the ciliary processes; this region is called the pars plicata (corona ciliaris). From the sclera inward the ciliary body consists of: the supraciliaris (supraciliary layers) which is made up of strands of collagen containing melanocytes and fibroblasts; the ciliary stroma which contains blood vessels, melanocytes and the ciliary muscle; and the ciliary epithelium which comprises an inner non-pigmented layer and an outer pigmented layer and is a continuation of the internal limiting membrane of the retina and of the retinal pigment epithelium, respectively. The cells of these layers (particularly those of the non-pigmented layer) appear to be actively engaged in ion and water transport and the production of aqueous humour. See angle recession; cyclitis; iridodialysis; supraciliary space; stria; ultrafiltration.