Welcome to the practical classes of histology of organs and systems. Introducing lab class (in spanish)
These practical classes aims to provide students with the necessary educational resources so that they acquire basic practical skills of each topic, i.e. recognize, locate and describe the types of cell, tissue and structures specific to each body.
Each of these practical classes are structured in three main elements:
-Definition of learning objectives.
-Notes: Description of structures, tissues and cell types inherent in the system.
-Location of structures exercises / cell types in virtual preparations

LEARNING OBJECTIVES
-Identify the three tunics of the eye.
-identify the compartments of the eye.
-Identify the cornea and the sclera in the fibrous tunic.
-Identify the layers of the cornea.
-Identify the choroid, iris and ciliary body in the vascular tunic.
-Characterize the structure of the ciliary body.
-Characterize the structure of the lens.
-Locate the retina.
-Identify the compartments of the cochlea: tympanic ramp, media and vestibular and its limits.
-Identify the typescell phones and structures of the organ of Corti.
-Identify the spiral ganglion.
-Identify the semicircular canals and the organ of balance ampulares ridges.

GENERAL QUESTIONS
The sensory system aims to capture the environment information for transmission to the Central nervous system, to match the answers of the Agency.
Five basic senses are traditionally defined:
-Vision: This connection is carried out by the eye.
-Hearing: This connection is carried out by the ear, which also contains the organ of balance.
-Smell: This function is performed in the nostrils, by the olfactory epithelium.
-Taste: The structures responsible for capturing the taste sensations are the taste buds of the tongue.
-Touch: Tactile information is captured by sensory corpuscles of skin.
In this chapter we will try the structure of the eye and the inner ear.
The olfactory epithelium is described in the "Respiratory system" topic. (Volume 2 of this series)
Papillae are discussed in the section "The language" of the "digestive system I: oral tissues". (Volume 3 of this series)
Tactile sensory corpuscles arestudy on the theme "Integumentary system (skin)" (in this volume).

THE EYE
The eye has mission to capture the light, focus on its posterior wall (retina), where numerous sensory cells transduced light information into nerve impulses that are transported by the optic nerve to the brain, which will form the image.
The eyes are even bodies located in cavities in the skull (orbits) in the anterior part of the head, that protect them. The eyes have a set of (skeletal) muscles that allow its movement. Also find a few folds of skin to protect the anterior part of the eye: the eyelids.
Both eyes are slightly separated, which allows many species (including humans) have three-dimensional vision, as the images that receive each eye are slightly different, and these differences allow the brain to recreate the 3D environment.
The eye is spheroidal (eyeball) delimited by a set of three layers (robes), which defined a set of spaces (Chambers) in its interior. These robes are: Tunics (layers) of the eye Microscopic anatomy of the eye
-Fibrous tunic: the outermost layer, it is fibrous my(dense connective tissue) and consists of two parts: Structure of the anterior part of the eye
-The cornea, which occupies the anterior and is transparent to facilitate the passage of light.
-The sclera, which occupies the rest of this tunic is whitish (opaque), making the interior of the eyeball in a Camera Obscura.
-Vascular tunic: also known as uveal and includes: the choroid, ciliary body and iris stroma.
-Nervous tunic: it is the innermost layer, lines after three-quarters of the eyeball, it contains the retina, which is the seat of the sensory cells.
In the eyeball differentiate three cavities or chambers: Chambers of the eye Microscopic anatomy of the eye
-Anterior Chamber: it is located between the cornea and the iris, is occupied by the aqueous humor.
-Rear camera: it is located between the iris and the lens and is also occupied by aqueous humor.
-Vitreous body: it lies behind the iris and is occupied by the vitreous humor.

CORNEA
It is part of the fibrous tunic and is located in the front part of the eye. Structure of the anterior part of the eye
It is transparent to allow the passage of light. This transparency is due to the regularity of the structure.
The cóRNEA is organized in layers are from the outside to the inside: Structure of the Cornea
-Previous epithelium: is the outermost layer and with the outside. It is a fairly thin not stratified stratified flat epithelium (from 5 to 7 layers of cells in humans). This epithelium is continuous with the epithelium of the conjunctiva.
-Bowman membrane: consists of the basement membrane of the previous epithelium together with Collagen fibers. It has about 10 m of thickness.
-Stromal corneal (own substance): it is the thickest layer and consists of very regular dense connective tissue. In each layer the collagen fibers are arranged parallel each other but rotated 900 with respect to the previous layer and later. This regularity in the arrangement of collagen fibres is that provides transparency to the cornea. Between the layers of fibers collagen located fibroblasts very flattened, to which some authors called queratocitos. The corneal stroma is avascular, although it does have nerve fibres.
-Membrane of Descemet: this corresponds to the basal membrane of the posterior epithelium, is one of the thicker body basal membranes and has a thickness of 5 to 10 m.
-Epitsubsequent Elio: it is a simple flat epithelium, given its way some authors refer to it as corneal endothelium. It is bordered by the anterior Chamber of the eye.

SCLEROTIC Structure of the Sclera
It is the continuation of the cornea (belongs to the fibrous tunic)., the area of Union with the cornea known as limbo. It differs from the cornea because it is whitish and non-transparent, this is because in the stromal Collagen fibers no available form an irregular shape and not regular in the corneal stroma.
The Mission of the sclera is the provide resistance to the eyeball.
The whites from the outside towards the choroid differ three layers:
-Episcleral sheet: is a layer of loose connective tissue
-Stroma (own substance / Tenon capsule): dense irregular connective tissue is.
-Lamina fusca (supracoroidea sheet): is the innermost layer of the sclera. Consists of connective tissue fibres collagen and elastic, as well as fibroblasts, melanocytes, macrophages and other cells of the connective tissue.

CHOROID Structure of the Choroid
The choroid is the portion of the vascular tunic which covers the retina and isbelow the sclera. The choroid is highly vascularizada it has as mission the provision of oxygen and nutrients to the adjacent structures.
The choroid is also organized in layers from the whites to the retina are:
-Supracoroidea plate: it is the layer next to the sclera and presents similar characteristics to the supracoroidea lamina (lamina fusca) in the sclera by what some authors define both layers as a single.
-Choroid stroma (own substance): is composed of connective tissue with lots of lines and arteries.
-Coriocapilar: Is a thin foil full of fenestrated capillaries, whose mission is to provide oxygen and nutrients to the nearest layers of the retina.
-Bruch sheet: is composed of the basal lamina of the retinal epithelium comp0lementado with collagen fibrils and some elastic fibers.
IRIS Structure of the Iris
The iris is the most anterior part of the vascular tunic and a disc that lies between the cornea and the lens delimiting the anterior and posterior Chambers of the eye.
In the center of the iris is a hole called pupil, whose diameter can varythrough two contractile structures
-Circular/sphincter muscle (not shown). Located in the stroma of the iris near the pupillary border, it is composed of smooth muscle fibers. His action causes the contraction of the pupil "meiosis".
-The pupil dilator. It is radial morphology, i.e. from around the pupillary border towards the periphery. It is located just above the posterior epithelium and is formed by myoepithelial cells. His action causes the dilation of the pupil "Mydriasis".
The function of the iris is to regulate the amount of light entering the eyeball by varying the diameter of the pupil.
One of the most important characteristics of the iris is the color, which in humans varies considerably from one individual to another. These colour differences are due to the different amount and disposition of melanocytes.
Four layers are from the anterior chamber towards the rear camera can be distinguished in the iris:
-Fibrous layer (previous marginal lamina): consists primarily of melanocytes and fibroblasts.
-Stroma: Is composed of very vascularized connective tissue.
-The pupil dilator. It is a thin layer of cells mioepitelialIt is located just above the posterior epithelium.
-Posterior epithelium: is composed of a double layer of pigmented cells (making it difficult to distinguish cell boundaries in samples under a microscope).

BODY Structure of the Ciliary body Items of the ciliary body CILIARY Structure of the anterior part of the eye
The ciliary body is located between the "ora serrata" of the retina and the basis of the iris, forms a ring on the front of the eyeball.
It is composed of a body (or base), formed by a stroma of connective similar to that of the choroid (with which is continuous) and a few finger projections "ciliary processes".
A package of smooth muscle fibers, known as "ciliary muscle", Items of the ciliary body which is responsible for the process of accommodation is located in the stroma. The accommodation process is the change in the form of the lens which changes the angle of incidence of the light and therefore the focal length. To enter into the ciliary muscle lens is rounded, while the relax you lens is flattened.
Ciliary processes are formed by a stroma of connective coated by a double layer of epithelial cells, of which the inner layer are very pigmented. This epithelium has as its mission the synthesis of smokeaqueous r, which occupies the after and before Chambers of the eye. Process of the Ciliary body
In the previous part of the ciliary body, in the angle Iridium-corneal, which is the angle formed by the iris and the cornea, is located in the stroma, the Schlem channel, which is the route of evacuation of excess aqueous humor. Structure of the Ciliary body This channel obstruction causes an increase in pressure within the eyeball (as is not evacuated aqueous humor). This disease is known as "glaucoma".

CRYSTALLINE Microscopic anatomy of the eye Structure of the anterior part of the eye
Lens, also known as lens, is floating, behind the cornea, suspended by a few filaments (zonulares fibres), which are anchored in the ciliary processes.
It is formed by epithelial cells arranged very regularly in the form of honeycomb, what gives crystal clear characteristics.
It is surrounded by a thick basal lamina "capsule of the lens', where the zonulares fibers are inserted.
In the previous part, Structure of Lens (surface) below the capsule, stands a simple rate cubical epithelium. This epithelium cells divide by the polar plane so new cells progress toward the equatorial planeof the lens. When they arrive to the Equator they introduce inside and lose the core, although the cells do not die and its metabolic activity persists. Structure of Lens (equatorial area) Those cells that make up the body of the lens are very cylindrical profile. Structure of Lens (surface) Structure of Lens (equatorial area) In the cytoplasm of these cells are located a soluble crystalline calls proteins with a high index of refraction lens that provides their optical properties. The loss of solubility of these proteins leads to opacity in a disease known as falls.
The previous epithelium maintains, although in a slow way, its mitotic activity throughout life, so the lens grows continuously, which can cause, with age phenomena of impossibility of approach to short distances "eyestrain".

RETINA Layers of the retina
He composed the nervous tunic of the eye and is the layer where the transduction of light information occurs in nerve impulses which are transported to the brain.
Is organized into 10 layers are from the choroid to the vitreous humor: Layers of the retina
1-Pigmented cells (epithelium).
2 Layer of photoreceptors.
3. External limiting membrane.
4.-CAPA nuclear external.
5.-Internal plexiforme layer.
6.-Nuclear layer internal.
7.-Internal plexiforme layer.
8 Layer node.
9 Layer of fibers.
10.-Internal limiting membrane.
In all these layers are located numerous cell types, of which include the photoreceptors: "rods and cones". There are also different types glial and neuronal types.
-Cones and sticks: cells (neurons) are thin and long arranged perpendicular. They occupy several layers of the retina layers 2, 3, 4 and 5. Both cell types have a segmented cytoplasm. The segment of the cytoplasm containing the kernel is located in layer 4 (external nuclear), below this segment the cytoplasm strangles slightly and are membrane zónulas adherens that anchor cones, poles and Müller (glial cells) cells; all these unions are at the same height and form the layer 3 (external limiting membrane), located below the internal segment containing the majority of cytoplasmic organelles of cells. Under the segment domestic and United to him by a modified cilium is located the external segment consisting of stacked membranous discs. In the case ofcanes the external segment is thin and has a cylindrical shape, while canes presents a conical shape and is somewhat thick and short. External segments of cones and sticks rest in cytoplasmic projections of the epithelial cells of layer 1. In both cell types the domestic segment and the external segment located in layer 2 (photoreceptors). The transduction of visual information is done at the height of the outer segment, thanks to the pigments found in the membranous disks. The canes are recipients of light intensity (discriminate between clarity and darkness), while the cones respond to high light intensities and the movement being able to resolve fine details and colors. Above the zone of the kernel, already in layer 5 (external plexiforme) are cytoplasmic extensions responsible for transmitting the nervous information in the first relay. The extensions on the Poles are known as "spherules" and those of the Poles as "pedicles". To appreciate these details of the morphology of these types cellular is necessary the use of electron microscopy at the light microscope and stains convincedend as the hematoxylin - eosin or the trichrome Masson, not these cells only, appreciating the set of kernels in the layer 4 can identify, layer 3 is difficult to distinguish internal and external segments of cones and rods form the layer 2 Although it is not possible to identify them. In humans, are located approximately 120 million rods and 6 million cones in each eye.
-Bipolar neurons: present the typical morphology of the bipolar neurons. Its neuronal body located in layer 6 (internal nuclear), their dendrites receive information through synapses (first relay) from cells (spherules of rods and cones pedicles) photoreceptor layer 5 (internal plexiforme). These cells the axon branches into Layer 7 (internal plexiforme).
-Horizontal cells: are neurons whose cell body is also located in the outer nuclear layer. Sinaptan on several cones and sticks, and dendrites of bipolar neurons.
-Ganglion neurons: their cell bodies are found in the layer (node) 8. Their dendrites are deployed in the Layer 7 (internal plexiforme). They receive information, mainly of the bipolar neurons (s)(second relay). Your Axon rises to layer 9 (nerve fibers) where it adopts a horizontal trajectory and moves towards the posterior part of the eye (to the optic disc), which bind all these axons, cross the three robes and leave the eye forming the optic nerve.
-Amacrinas cell: the cell body of these neurons are located in layer 6 (internal nuclear) and its extensions ascend to the Layer 7 where sinaptan, both with ganglion neurons and the extensions of the bipolar neurons.
-Müller cells: are character glial cells. Its cell body located in layer 6 (internal nuclear). His apical extension reaches the layer 10 where it forms the inner limiting membrane. Its basal extension reaches the layer 3 where anchor through zónulas adherens to cones and rods forming the outer limiting membrane, both extensions are short projections that surround the synapses in the plexiformes layers and the cell bodies of the photoreceptors.
-Pigment epithelium: is a simple cubic type epithelium. Form the layer 1 and its cells contain large amount of pigment that make light rebound and is captured by the photoreceptors. Among these cécells are established for narrow joints which form a barrier between the choroid and retina called retinal barrier. The apical part you can appreciate various projections that encompass parties terminals of cones and rods and anchor them. They also play a role of recycling to engulf the discarded these photoreceptors membranous disks.
In the back of the retina, at the height of the visual axis, the retina has a depression and the number of layers is smaller. In this area there are no rods and cones are only found in the layer of photoreceptors. This area is known as the central fovea (not shown).
The contribution of nutrients and oxygen to the retina is done in two ways:
-The innermost layers (of the 6-10) receive this contribution from capillaries that interned until the Layer 7 from branches of the retinal artery that runs over layer 10.
-More outer layers (1 to 5) receive input from oxygen and nutrients from the choroidal vessels. These elements across the retinal barrier, whether by diffusion or active transport (e.g. oxygen and water) and then disseminated freely until the layer 4 or 5.
In the previous part of the ojo, at the height of the beginning of the ciliary body, the retina gradually decreases its thickness in an area that is known as "ora serrata". Retina, Ora serrata

OPTIC NERVE
As has been said, the axons of ganglion neurons run through the surface of the retina (layer 9) to merge in the back of the eye in the area known as optical disk. In this area the axons change direction and cross, in the form of beams, the sclera, in the structure known as cribosa plate. Structure of the initial segment of the optic nerve
These axons form a thick nerve in each eye that carries the large amount of visual information generated by each eye.
The optic nerve, given its embryonic origin as their structural characteristics should be considered as part of the Central nervous system, an example of this is the fact that the optic nerve, as well as the brain, is protected by meninges (PIA mater, Dura and arachnoid mater) and not epineuro as the peripheral nerves. Structure of the Optic nerve

PÁRPADO Structure of the eyelid
The eyelids are folds of skin whose mission is the protection of the eyes.
The eyelids, like the rest of the skin, are lined by epidermis and present structures ofthe skin such as hair follicles and sebaceous glands.
The most significant hairs of the eyelid are tabs, whose hair follicles are located near the edge of the eyelid, on its outer side.
The sebaceous glands of the eyelid are called "glands of Meibonio" and are located on the inside of the eyelid and flow into the edge of the eyelid unrelated to the hair follicles. Its oily secretion aims to form a film on the tears, which thing serves to maintain the hydration of the cornea and prevent their dehydration.

EAR
The ear contains two functional bodies: the organ of hearing and balance organ.
The ear is traditionally divided into three parts:
-Outer ear: consists of the pinna (ear) and the ear canal, whose mission is to capture the sound waves and drive them to the eardrum (which vibrates in resonance).
-Middle ear: the middle ear starts in the eardrum, or tympanic membrane, to which is attached the chain of ossicles: hammer, anvil and stirrup that transmits the vibrations of the membrane timpánica to the inner ear. It also is part of the middle ear the auditory tube or Eustachian tube that connects the middle ear with the pharynx equalizing air pressures.
-Inner ear: the inner ear are both the organ of hearing, which receives sound waves transmitted by the ossicles of the middle ear and the transduce in nerve impulses that are transmitted to the brain, and the body of the balance, which operates independently of the sound waves and provides to the brain information about our position and orientation in space.

ORGAN of hearing Microscopic anatomy of the inner ear
The main element of the inner ear is the cochlea. The cochlea is basically a duct wrapped on itself in the form of caracol.
This duct is divided into three spaces, ramps: Inner ear. Structure of the cochlea, Organ of Corti
-Tympanic ramp
-Average ramp
-Ramp vestibular
These ramps are filled with liquid: the musician (perilymph in vestibular ramps and tympanic, and the endolymph in the average ramp).
Along the Canal ramps are separated each other. The organ of Corti with the basilar membrane separating the tympanic ramp ramp media and Reiner membrane separates the average ramp ramp vestibular. At the end of the cochlea tympanic ramps and vestibular communicate through a hole called the helicotrema.
-Organ of Corti: Inner ear. Cellula types and structures of the organ of Corti the body and Corti is a set of structures that have the function the transduction of sound waves transmitted by the lymph in nerve impulses, which are then transmitted to the brain and cells. An important element of the organ of Corti is the tectoria membrane, which is a membrane of connective tissue whose free end rests on the Cilia of the apical dominance of the sensory cells (internal and external). The waves of the lymph move membrane tectoria, which hits the Cilia of the sensory cells (ciliated cells) which causes the change of polarity of its membrane thereby creating the nerve impulse is transferred to the sensory fibers from the spiral ganglion neurons. Ciliated cells resting on falángicas cells and these ACE or time on the cells of the pillar, are, also cell companions that give strength to all. The whole descasa on an epithelial membrane called the basilar membrane.
The lateral wall of theaverage ramp is upholstered by a cúbico-cilíndrico simple epithelium known as "Striates vascularis" which is responsible for the secretion of the endolymph which fill the medium ramp.

THE balance organ Microscopic anatomy of the inner ear
The organ of balance consists of a series of spaces filled with endolymph containing sensory structures. These spaces are:
-Semicircular canals
-Utricle and Sáculo
The semicircular canals are three, each oriented in um space axis. Each has a sensory structure: the ridges ampulares. The sensory cells of the ampulares ridges contain Cilia that his move from the flow of the perilymph of the channels, which provides information about the direction of movement in space.
The utricle and the sáculo also have sensory structures: the macules. The macules are similar to the crests ampulares with the particularity that on the Cilia located a gelatinous mass surmounted by a series of small crystals of calcite (calcium carbonate) called Otoliths. ETA structure makes the macules sensory cells sensitive to linear motion and acceleration.

EXERCISES
1 SHOWS:Cornea (eye), Masson 1.5 Tricrómico um Cornea Masson's trichrome 7um
-It is located abroad, the cornea, and anterior Chamber of the eye.
-Identify each of the layers of the cornea.
SHOWS 2: Crystal (eye), Masson 1.5 Tricrómico um Lens Masson's trichrome 7um
-Identify the elements and areas of the lens.
SHOWS 3: Ciliary processes (eye), Masson 1.5 Tricrómico um Ciliary processes Masson's trichrome 7um
-Locate the processes in the ciliary body.
-Identify of coating epithelium and its layers of the ciliary processes.
SHOWS 4: Retina (eye), Masson 1.5 Tricrómico um Retina Masson's trichrome 7um
-Located sclera, choroid and retina.
-Identify each of the layers of the retina.
SHOWS 5: Eye developing (embryo), Hematoxilina-Eosina 1.5 um Developing eye H-E 1,5um
-Identify the structures of the eye in development.
-Identify the eyelids.
-Identify the cornea.
-It identifies the iris.
-It identifies the lens.
Displays 6: Inner ear (cochlea), 7 Hematoxilina-Eosina um Inner ear (Cochlea) H-E 7um
-Identifies the ramps of the cochlea: tympanic ramp, media, vestibular.
-Identify the membrane by Reiner.
-Identifies the organ of Corti and characterized their significant structures.