**1. Introduction**

#### **1.1. Anatomy of the ciliary body**

The ciliary body is the site of aqueous humor production and it is totally involved in aqueous humor dynamics. The ciliary body is the anterior portion of the uveal tract, which is located between the iris and the choroid. (figure 1)

**Figure 1.** Histology of human ciliary body (courtesy Prof. Ruth Santo)

properly cited.

© 2013 Borges- Giampani and Giampani Junior; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

On cross-section, the ciliary body has the shape of a right triangle, approximately 6 mm in length, where its apex is contiguous with the choroid and the base close to the iris. Externally, it attaches to the scleral spur creating a potential space, the supraciliary space, between it and the sclera. The external surface forms the anterior insertion of the uveal tract. The internal surface of the ciliary body comes in contact with the vitreous surface and is continuous with the retina [1].

**1.2. Ciliary muscle**

tor of the eye [6].

**1.3. Ciliary vessels**

**1.4. Ciliary epithelia**

epithelium. (figure 3)

**1.5. Innervation**

canal.

The ciliary muscle consists of three separate muscle fibers: longitudinal, circular and oblique. The longitudinal fibers (meridional), which are the most external, attach the ciliary body anteriorly to the scleral spur and trabecular meshwork at the limbus, and posteriorly to the supracoroidal lamina (fibers connecting choroid and sclera) as far back as the equa‐

Anatomy of Ciliary Body, Ciliary Processes, Anterior Chamber Angle and Collector Vessels

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The contraction of the longitudinal muscle, opens the trabecular meshwork and Schlemm`s

The circular fibers (sphincteric) make up the more anterior and inner portion, and run parallel to the limbus. This insertion is in the posterior iris. When these fibers contract, the zonules

The oblique fibers (radial or intermediate) connect the longitudinal and circular fibers. The

Traditional views hold that the vasculature of the ciliary body is supplied by the anterior ciliary arteries and the long posterior ciliary arteries, forming the major arterial circle near the root of the iris, wherefrom branches supply the iris, ciliary body and the anterior choroid. Recent studies in primates have shown a complex vascular arrangement with collateral circulation on at least three levels [7,8]: an episcleral circle formed by anterior ciliary branches; an intramus‐ cular circle formed through the anastomosis between anterior ciliary arteries and long posterior ciliary artery branches; and the major arterial circle formed primarily, if not exclu‐ sively, by paralimbal branches of the long posterior ciliary arteries. The major arterial circle is

The inner surfaces of the ciliary processes and the pars plana are lined by two layers of

The outer layer is the pigmented epithelium, which is composed of low cuboidal cells and is

The inner layer is formed by the nonpigmented epithelium, a columnar epithelium, adjacent

The major innervation is provided by ciliary nerve branches (third cranial nerve-oculomotor), forming a rich parasympathetic plexus. There are also sympathetic fibers originating from the

adjacent to the stroma and continuous with the retinal pigmented epithelium.

to the aqueous humor in the posterior chamber and continuous with the retina.

These two layers of the epithelium are appositioned in their apical surfaces.

superior cervical ganglion which keep pace with arteries and their branches.

relax, increasing the lens axial diameter and its convexity.

contraction of these fibers may widen the uveal trabecular spaces.

the immediate vascular supply of the iris and ciliary processes [8,9].

The anterior portion of the ciliary body is called the *pars plicata* or *corona ciliaris* and is charac‐ terized by ciliary processes, which consist of approximately 70 radial ridges (major ciliary processes) and an equal number of smaller ridges (minor or intermediate ciliary processes) between them [2].

The *pars plicata* is contiguous with the iris posterior surface and is approximately 2 mm in length, 0.5 mm in width, and 0.8-1 mm in height [2,3].

Thus, the ciliary processes have a large surface area, estimated to be 6 cm2 , for ultrafiltration and active fluid transport, this being the actual site of aqueous production; the *pars plicata* accounts for approximately 25% of the total length of the ciliary body (2 mm) [4] (figure 2)

The posterior portion of the ciliary body is called the *pars plana* or *orbicularis ciliaris*, which has a relatively flat and very pigmented inner surface, and is continuous with the choroid at the ora serrata.

In the adult eye, the anterior-posterior length of the ciliary body ranges 4.5-5.2 mm nasally and 5.6 -6.3 mm temporally [5].

The ciliary body is composed of muscle, vessels and epithelium.

**Figure 2.** Pars plicata of rabbit ciliary body (courtesy of Prof. Durval Carvalho Jr.)

### **1.2. Ciliary muscle**

On cross-section, the ciliary body has the shape of a right triangle, approximately 6 mm in length, where its apex is contiguous with the choroid and the base close to the iris. Externally, it attaches to the scleral spur creating a potential space, the supraciliary space, between it and the sclera. The external surface forms the anterior insertion of the uveal tract. The internal surface of the ciliary body comes in contact with the vitreous surface and is continuous with

The anterior portion of the ciliary body is called the *pars plicata* or *corona ciliaris* and is charac‐ terized by ciliary processes, which consist of approximately 70 radial ridges (major ciliary processes) and an equal number of smaller ridges (minor or intermediate ciliary processes)

The *pars plicata* is contiguous with the iris posterior surface and is approximately 2 mm in

and active fluid transport, this being the actual site of aqueous production; the *pars plicata* accounts for approximately 25% of the total length of the ciliary body (2 mm) [4] (figure 2)

The posterior portion of the ciliary body is called the *pars plana* or *orbicularis ciliaris*, which has a relatively flat and very pigmented inner surface, and is continuous with the choroid at the

In the adult eye, the anterior-posterior length of the ciliary body ranges 4.5-5.2 mm nasally and

, for ultrafiltration

Thus, the ciliary processes have a large surface area, estimated to be 6 cm2

The ciliary body is composed of muscle, vessels and epithelium.

**Figure 2.** Pars plicata of rabbit ciliary body (courtesy of Prof. Durval Carvalho Jr.)

the retina [1].

4 Glaucoma - Basic and Clinical Aspects

between them [2].

ora serrata.

5.6 -6.3 mm temporally [5].

length, 0.5 mm in width, and 0.8-1 mm in height [2,3].

The ciliary muscle consists of three separate muscle fibers: longitudinal, circular and oblique.

The longitudinal fibers (meridional), which are the most external, attach the ciliary body anteriorly to the scleral spur and trabecular meshwork at the limbus, and posteriorly to the supracoroidal lamina (fibers connecting choroid and sclera) as far back as the equa‐ tor of the eye [6].

The contraction of the longitudinal muscle, opens the trabecular meshwork and Schlemm`s canal.

The circular fibers (sphincteric) make up the more anterior and inner portion, and run parallel to the limbus. This insertion is in the posterior iris. When these fibers contract, the zonules relax, increasing the lens axial diameter and its convexity.

The oblique fibers (radial or intermediate) connect the longitudinal and circular fibers. The contraction of these fibers may widen the uveal trabecular spaces.

#### **1.3. Ciliary vessels**

Traditional views hold that the vasculature of the ciliary body is supplied by the anterior ciliary arteries and the long posterior ciliary arteries, forming the major arterial circle near the root of the iris, wherefrom branches supply the iris, ciliary body and the anterior choroid. Recent studies in primates have shown a complex vascular arrangement with collateral circulation on at least three levels [7,8]: an episcleral circle formed by anterior ciliary branches; an intramus‐ cular circle formed through the anastomosis between anterior ciliary arteries and long posterior ciliary artery branches; and the major arterial circle formed primarily, if not exclu‐ sively, by paralimbal branches of the long posterior ciliary arteries. The major arterial circle is the immediate vascular supply of the iris and ciliary processes [8,9].

#### **1.4. Ciliary epithelia**

The inner surfaces of the ciliary processes and the pars plana are lined by two layers of epithelium. (figure 3)

The outer layer is the pigmented epithelium, which is composed of low cuboidal cells and is adjacent to the stroma and continuous with the retinal pigmented epithelium.

The inner layer is formed by the nonpigmented epithelium, a columnar epithelium, adjacent to the aqueous humor in the posterior chamber and continuous with the retina.

These two layers of the epithelium are appositioned in their apical surfaces.

#### **1.5. Innervation**

The major innervation is provided by ciliary nerve branches (third cranial nerve-oculomotor), forming a rich parasympathetic plexus. There are also sympathetic fibers originating from the superior cervical ganglion which keep pace with arteries and their branches.

faces the aqueous humor, is composed of fibrils in a glycoprotein with laminin and collagens I, III and IV [16]. The apical cells of this membrane are connected by tight junctions (zonulae occludentae), creating a permeability barrier, which is an important component of the blood-

Anatomy of Ciliary Body, Ciliary Processes, Anterior Chamber Angle and Collector Vessels

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Adjacent cells within each epithelial layer and between the apical cells of the two layers are connected by gap junctions, tight junctions and desmosomes. The apical membranes of the

The anterior portion of the nonpigmented ciliary epithelium has the morphologic features of a tissue involved in active fluid transport, i.e., evidence of abundant sodium-potassium adenosine triphosphatase ( Na+ K+ ATPase), glycolytic enzymes activity, and incorporation of labeled sulfate into glycolipids and glycoproteins [17]. There are many indications that the aqueous humor is produced in the anterior portion of the nonpigmented epithelia of ciliary

There is a potential space between the two epithelial layers, called "ciliary channels". The aqueous humor may be secreted into this space after beta-adrenergic agonist stimulation, but

The iris inserts into the anterior side of the ciliary body and separates the aqueous compartment into a posterior and anterior chamber. The angle formed by the iris and the cornea is the

The aqueous humor is formed by the ciliary process, passes from posterior chamber to the anterior chamber through the pupil, and leaves the eye at the anterior chamber angle. Most of the aqueous humor exits the eye through the trabecular meshwork, which is called the conventional or canalicular system, and accounts for 83 to 96% of aqueous outflow of normal

The other 5-15% of the aqueous humor leaves the eye through the uveoscleral and uveovortex systems (unconventional systems), including anterior ciliary muscle and iris to reach supra‐

This line or zone represents the transition from the trabecular to corneal endothelium, the termination of Descemet`s membrane, and the trabecular insertion into the corneal stroma.

**3.1. Anatomy of anterior chamber angle (conventional outflow system)**

aqueous barrier called the internal limiting membrane.

processes [17,18,19].

this notion requires additional studies [20].

.

ciliary and suprachoroidal spaces [22,23,24].

**3. Anterior chamber angle**

anterior chamber angle6

human eyes [21,22].

**a.** Schwalbe`s line

nonpigmented epithelium are also joined by tight junctions [12,13,14]

These tight junctions are permeable only to low-molecular-weight solutes.

**Figure 3.** Histology of human ciliary epithelia
