Lecture 8:Anatomy of Semicircular Canals
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Questions and Answers

What happens to the cilia in the otolithic membrane when the head moves?

  • They move in a circular motion
  • They remain stationary
  • They bend in the opposite direction of gravity
  • They bend in the direction of gravity (correct)

    • What is the function of the crista ampullaris in the semicircular canals?

  • To produce endolymph
  • To support the hair cells
  • To contain hair cells and supporting cells (correct)
  • To connect the semicircular canals to the vestibule

    • What is the gelatinous structure on the apical surface of the hair cells?

  • Endolymph
  • Crista ampullaris
  • Cupula (correct)
  • Otolithic membrane

    • What happens to the nerve fiber when the cilia bend in a certain direction?

    <p>It is either stimulated or inhibited depending on the direction of bending</p> Signup and view all the answers

    What is the function of the ampulla in the semicircular canals?

    <p>To open into the vestibule</p> Signup and view all the answers

    What is the purpose of the otolithic membrane bending the cilia in the direction of gravity?

    <p>To recognize the position of the head</p> Signup and view all the answers

    What is the function of the utricle and saccule in the inner ear?

    <p>Balance</p> Signup and view all the answers

    What is the main component of the eyelid?

    <p>Tarsal plate</p> Signup and view all the answers

    What is the function of the cristae ampullaris?

    <p>Balance</p> Signup and view all the answers

    What type of epithelium is found in the conjunctiva?

    <p>Stratified columnar or cuboidal</p> Signup and view all the answers

    What is the function of the cochlear ducts?

    <p>Hearing</p> Signup and view all the answers

    What is the outermost layer of the retina?

    <p>External limiting membrane</p> Signup and view all the answers

    What is the function of the Meibomian glands?

    <p>Producing sweat</p> Signup and view all the answers

    What is the function of the ganglionic cell layer?

    <p>Forming the optic nerve</p> Signup and view all the answers

    What is the main function of the pigmented iris in the human eye?

    <p>To regulate the amount of light reaching the retina</p> Signup and view all the answers

    What is the layer of the cornea composed of simple squamous epithelium?

    <p>Endothelium of anterior chamber</p> Signup and view all the answers

    How many layers are there in the stroma of the cornea?

    <p>Around 200 layers</p> Signup and view all the answers

    What is the function of the melanin pigments in the pigmented epithelium of the retina?

    <p>To absorb light after photoreceptors have been stimulated</p> Signup and view all the answers

    What is the name of the outermost layer of the retina?

    <p>Pigmented layer</p> Signup and view all the answers

    What type of epithelium is the corneal epithelium made of?

    <p>Stratified squamous non-keratinized epithelium</p> Signup and view all the answers

    How many main neurons are there in the nervous part of the retina?

    <p>3</p> Signup and view all the answers

    What is the name of the middle coat of the human eye?

    <p>Uveal tract</p> Signup and view all the answers

    Where are the sense organs located?

    <p>Inside the membranous labyrinth</p> Signup and view all the answers

    What is the function of the otolith organs?

    <p>To sense head vertical position</p> Signup and view all the answers

    What is the function of the cristae ampullaris?

    <p>To sense head rotation</p> Signup and view all the answers

    What is the name of the gelatinous mass that the stereocilia of the hair cells are embedded in?

    <p>Otolithic membrane</p> Signup and view all the answers

    What are the two types of hair cells found in the organ of Corti?

    <p>Inner and outer hair cells</p> Signup and view all the answers

    What is the name of the membrane that rests on top of the stereo cilia of the hair cells?

    <p>Tectorial membrane</p> Signup and view all the answers

    What is the name of the part of the hair cell that is directly related to the dendritic process of the afferent sensory neuron?

    <p>Basal part</p> Signup and view all the answers

    What is the term for the entrance hall of the bony labyrinth in the inner ear?

    <p>Vestibule</p> Signup and view all the answers

    What is the function of the organ of Corti?

    <p>To sense sound</p> Signup and view all the answers

    What is the name of the membrane that separates the scala vestibuli from the scala media?

    <p>Reissner's membrane</p> Signup and view all the answers

    What is the function of the utricle and saccule?

    <p>To sense head vertical position</p> Signup and view all the answers

    What is the name of the part of the hair cell that is directly related to the dendritic process of the afferent sensory neuron?

    <p>Basal part</p> Signup and view all the answers

    What is the name of the structure that contains the sensory cells in the utricle and saccule?

    <p>Macula</p> Signup and view all the answers

    What is the name of the gelatinous mass that the stereocilia of the hair cells are embedded in?

    <p>Otolithic membrane</p> Signup and view all the answers

    What is the name of the part of the cochlea that contains the organ of Corti?

    <p>Scala media</p> Signup and view all the answers

    What is the function of the cristae ampullaris?

    <p>To sense head rotation</p> Signup and view all the answers

    What is the name of the central part of the bony labyrinth in the inner ear?

    <p>Vestibule</p> Signup and view all the answers

    What are the two types of hair cells found in the organ of Corti?

    <p>Inner and outer hair cells</p> Signup and view all the answers

    Study Notes

    Semicircular Canals

    • Semicircular canals are arranged in different planes
    • Each canal contains a tube of the membranous labyrinth, filled with endolymph
    • Each canal has an expanded end called the ampulla, which opens into the vestibule
    • The membranous ampulla contains a group of tissues called the crista ampullaris
    • Crista ampullaris contains hair cells and supporting cells

    Histology of Semicircular Canals

    • On the apical surface of the hair cells, there is a gelatinous structure called the cupula
    • The apical surface of the hair cells contains tufts of cilia, which project into the cupula
    • When the head moves, the cupula moves too, and the tufts of cilia will move as a result of the movement of the cupula
    • Depending on the direction of the bending of the cilia, the nerve fiber will be stimulated or inhibited

    The Human Eye

    • The human eye has three coats or layers: fibro-elastic outer coat, middle vascular coat, and inner photosensitive nervous coat
    • The outer coat consists of sclera and cornea
    • The middle vascular coat consists of iris, ciliary body, and choroid
    • The inner photosensitive nervous coat is the retina

    Cornea

    • The cornea consists of five layers: corneal epithelium, Bowman's membrane, stroma, Descemet's membrane, and endothelium
    • Corneal epithelium is made of stratified squamous non-keratinized epithelium
    • Bowman's membrane is made of compactly packed collagen fibrils
    • Stroma is composed of around 200 layers of collagen fibrils with fibroblasts, arranged in a highly organized manner

    Histology of the Retina

    • The retina is principally composed of two parts: pigmented cuboidal epithelium and multilayered nervous part
    • The pigmented cuboidal epithelium contains melanin pigments that absorb light after photoreceptors have been stimulated
    • The multilayered nervous part contains three main neurons: photoreceptors (rods and cones), bipolar neurons, and ganglionic multipolar neurons

    Layers of the Retina

    • The retina is subdivided into 10 recognizable layers: pigmented layer, photoreceptor layer, external limiting membrane, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer, ganglionic cell layer, nerve fiber layer, and internal limiting membrane

    Histology of the Eyelid

    • The eyelid consists of a dense fibro-elastic plate (the tarsal plate) which is covered externally by thin skin and lined internally by the conjunctiva
    • Orbicularis oculi muscle can be seen between the skin and tarsal plate
    • Within the tarsal plate, lie 12-30 tarsal (Meibomian) glands
    • Associated with the eyelashes are some ciliary sweat glands
    • The conjunctiva is the epithelium which covers the exposed part of the sclera and inner surface of the eyelids

    The Inner Ear

    • The inner ear consists of the bony labyrinth and membranous labyrinth, filled with perilymph and endolymph respectively
    • Parts of bony labyrinth include vestibule, semicircular canals, and cochlea
    • Parts of membranous labyrinth include utricle and saccule, semicircular ducts, and cochlear ducts
    • Sensory receptors in the membranous labyrinth include maculae, crista ampullaris, and organ of Corti

    Histology of the Cochlea

    • The lumen of the cochlea is divided into three chambers: the scala vestibuli, the scala media (or cochlear duct), and the scala tympani
    • Both scala vestibuli and scala tympani are filled with perilymph, while the scala media is filled with endolymph
    • The organ of Corti is located in the scala media, where it is surrounded by the endolymph
    • The organ of Corti rests on the basilar membrane and contains two types of hair cells: inner hair cells and outer hair cells
    • The apical part of the hair cell shows multiple cilia that are attached to the tectorial membrane

    Histology of the Vestibule

    • The vestibule is the central part of the bony labyrinth in the inner ear
    • The vestibule has two membranous sacs: the utricle and the saccule
    • Together, both of the utricle and the saccule are known as the otolith organs
    • Each of the utricle and the saccule has on its inner surface a single patch of sensory cells called a macula
    • Each macula consists of hair cells and supporting cells resting on a basement membrane

    Otolith Organs

    • Within each macula, the stereocilia of the hair cells are embedded in a gelatinous mass known as the otolithic membrane
    • When the head moves, the otolithic membrane bends the cilia in the direction of gravity, and the position is recognized by the central nervous system

    Semicircular Canals

    • Semicircular canals are arranged in different planes
    • Each canal contains a tube of the membranous labyrinth, filled with endolymph
    • Each canal has an expanded end called the ampulla, which opens into the vestibule
    • The membranous ampulla contains a group of tissues called the crista ampullaris
    • Crista ampullaris contains hair cells and supporting cells

    Histology of Semicircular Canals

    • On the apical surface of the hair cells, there is a gelatinous structure called the cupula
    • The apical surface of the hair cells contains tufts of cilia, which project into the cupula
    • When the head moves, the cupula moves too, and the tufts of cilia will move as a result of the movement of the cupula
    • Depending on the direction of the bending of the cilia, the nerve fiber will be stimulated or inhibited

    The Human Eye

    • The human eye has three coats or layers: fibro-elastic outer coat, middle vascular coat, and inner photosensitive nervous coat
    • The outer coat consists of sclera and cornea
    • The middle vascular coat consists of iris, ciliary body, and choroid
    • The inner photosensitive nervous coat is the retina

    Cornea

    • The cornea consists of five layers: corneal epithelium, Bowman's membrane, stroma, Descemet's membrane, and endothelium
    • Corneal epithelium is made of stratified squamous non-keratinized epithelium
    • Bowman's membrane is made of compactly packed collagen fibrils
    • Stroma is composed of around 200 layers of collagen fibrils with fibroblasts, arranged in a highly organized manner

    Histology of the Retina

    • The retina is principally composed of two parts: pigmented cuboidal epithelium and multilayered nervous part
    • The pigmented cuboidal epithelium contains melanin pigments that absorb light after photoreceptors have been stimulated
    • The multilayered nervous part contains three main neurons: photoreceptors (rods and cones), bipolar neurons, and ganglionic multipolar neurons

    Layers of the Retina

    • The retina is subdivided into 10 recognizable layers: pigmented layer, photoreceptor layer, external limiting membrane, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer, ganglionic cell layer, nerve fiber layer, and internal limiting membrane

    Histology of the Eyelid

    • The eyelid consists of a dense fibro-elastic plate (the tarsal plate) which is covered externally by thin skin and lined internally by the conjunctiva
    • Orbicularis oculi muscle can be seen between the skin and tarsal plate
    • Within the tarsal plate, lie 12-30 tarsal (Meibomian) glands
    • Associated with the eyelashes are some ciliary sweat glands
    • The conjunctiva is the epithelium which covers the exposed part of the sclera and inner surface of the eyelids

    The Inner Ear

    • The inner ear consists of the bony labyrinth and membranous labyrinth, filled with perilymph and endolymph respectively
    • Parts of bony labyrinth include vestibule, semicircular canals, and cochlea
    • Parts of membranous labyrinth include utricle and saccule, semicircular ducts, and cochlear ducts
    • Sensory receptors in the membranous labyrinth include maculae, crista ampullaris, and organ of Corti

    Histology of the Cochlea

    • The lumen of the cochlea is divided into three chambers: the scala vestibuli, the scala media (or cochlear duct), and the scala tympani
    • Both scala vestibuli and scala tympani are filled with perilymph, while the scala media is filled with endolymph
    • The organ of Corti is located in the scala media, where it is surrounded by the endolymph
    • The organ of Corti rests on the basilar membrane and contains two types of hair cells: inner hair cells and outer hair cells
    • The apical part of the hair cell shows multiple cilia that are attached to the tectorial membrane

    Histology of the Vestibule

    • The vestibule is the central part of the bony labyrinth in the inner ear
    • The vestibule has two membranous sacs: the utricle and the saccule
    • Together, both of the utricle and the saccule are known as the otolith organs
    • Each of the utricle and the saccule has on its inner surface a single patch of sensory cells called a macula
    • Each macula consists of hair cells and supporting cells resting on a basement membrane

    Otolith Organs

    • Within each macula, the stereocilia of the hair cells are embedded in a gelatinous mass known as the otolithic membrane
    • When the head moves, the otolithic membrane bends the cilia in the direction of gravity, and the position is recognized by the central nervous system

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    This quiz covers the structure and function of semicircular canals, including their arrangement, contents, and relationship to the vestibule.

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