| Saccule | |
|---|---|
 |
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| illustration of otolith organs showing detail of utricle, ococonia, endolymph, cupula, macula, hair cell filaments, and saccular nerve | |
| Latin | sacculus |
| Gray's | subject #232 1052 |
| MeSH | Saccule+and+Utricle |
Contents |
Introduction
The saccule is a bed of sensory cells situated in the inner ear. Endolymph is the fluid contained in the Membranous labyrinth of the Inner ear. The cupula is a structure in the Vestibular system, sensing Proprioception. The macula or macula lutea (from Latin macula, "spot" + lutea, "yellow" is an oval Yellow spot near the center Hair cells are the Sensory receptors of both the Auditory system and the Vestibular system in all Vertebrates. The saccular nerve is a nerve which supplies the Macula of the Saccule. The posterior semicircular canal is a part of the Vestibular system and detects rotations of the head in the Sagittal plane The superior semicircular canal ( anterior semicircular canal) is a part of the Vestibular system and detects rotation of the head around a rostral-caudal (anterior-posterior The utricle, or utriculus along with the Saccule is one of the two Otolith organs located in the Vertebrate Inner ear. The lateral or horizontal canal (external semicircular canal is the shortest of the three canals "Vestibulum" and "vestibule" redirect here For other uses see Vestibule (disambiguation. The cochlea is the auditory portion of the Inner ear. Its core component is the Organ of Corti, the sensory organ of hearing, which is distributed along Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. the Peripheral organs of the Special senses the organs of Taste ( Peripheral gustatory or Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books The saccule translates head movements into neural impulses which the brain can interpret. The saccule is sensitive to linear translations of the head, specifically movements up and down (think about moving on an elevator). When the head moves vertically, the sensory cells of the saccule are disturbed and the neurons connected to them begin transmitting impulses to the brain. These impulses travel along the vestibular portion of the eighth cranial nerve to the vestibular nuclei in the brainstem.
The vestibular system is important in maintaining balance, or equilibrium. The vestibular system includes the saccule, utricle, and the three semicircular canals. The semicircular canals are three half-circular interconnected tubes located inside each Ear that are the equivalent of three Gyroscopes located in three orthogonal The vestibule is the name of the fluid-filled, membranous duct than contains these organs of balance. The vestibule is encased in the temporal bone of the skull. The temporal bones are situated at the sides and base of the Skull.
Anatomy
The saccule, or sacculus, is the smaller of the two vestibular sacs. It is globular in form and lies in the recessus sphæricus near the opening of the scala vestibuli of the cochlea. Scala vestibuli is a Perilymph filled cavity inside the Cochlea of the Inner ear. The cochlea is the auditory portion of the Inner ear. Its core component is the Organ of Corti, the sensory organ of hearing, which is distributed along Its cavity does not directly communicate with that of the utricle. The anterior part of the saccule exhibits an oval thickening, the macula acustica sacculi, or macula, to which are distributed the saccular filaments of the vestibular branch of the vestibulocochlear nerve, also known as the acoustic nerve or cranial nerve VIII. The macula or macula lutea (from Latin macula, "spot" + lutea, "yellow" is an oval Yellow spot near the center The vestibulocochlear nerve (also known as the auditory or acoustic nerve) is the eighth of twelve Cranial nerves, and is responsible for transmitting sound The vestibulocochlear nerve (also known as the auditory or acoustic nerve) is the eighth of twelve Cranial nerves, and is responsible for transmitting sound The vestibulocochlear nerve (also known as the auditory or acoustic nerve) is the eighth of twelve Cranial nerves, and is responsible for transmitting sound
Within the macula are hair cells, each having a hair bundle on the apical aspect. Hair cells are the Sensory receptors of both the Auditory system and the Vestibular system in all Vertebrates. The hair bundle is composed of a single kinocilium and many (at least 70) stereocilia. A kinocilium is a special structure on the apex of Hair cells located in the sensory epithelium of the vertebrate Inner ear. Stereocilia are apical modifications of the cell which are distinct from Microvilli and Cilia. Stereocilia are connected to mechanically-gated ion channels in the hair cell plasma membrane via tip links. Supporting cells are interdigitate between hair cells and secrete the otolithic membrane, a thick, gelatinous layer of glycoprotein. The otolithic membrane is a Gelatinous membrane located in the Vestibular apparatus of the Inner ear, and plays an essential role in the Covering the surface of the otolithic membrane are otoliths, which are crystals of calcium carbonate. An otolith, (οτο- oto-, ear + λιθος lithos, a stone also called statoconium or otoconium is a structure in the Saccule For this reason, the saccule is sometimes called an "otolithic organ. "
From the posterior wall of the saccule is given off a canal, the ductus endolymphaticus. This duct is joined by the ductus utriculosaccularis, and then passes along the aquæductus vestibuli and ends in a blind pouch (saccus endolymphaticus) on the posterior surface of the petrous portion of the temporal bone, where it is in contact with the dura mater. The temporal bones are situated at the sides and base of the Skull. The dura mater (from the Latin "hard mother" or pachymeninx, is the tough and inflexible outermost of the three layers of the Meninges surrounding the
From the lower part of the saccule a short tube, the canalis reuniens of Hensen, passes downward and opens into the ductus cochlearis near its vestibular extremity. From the lower part of the Saccule a short tube the canalis reuniens of Hensen, passes downward and opens into the Ductus cochlearis near its vestibular extremity The cochlear duct (or scala media) is an Endolymph filled cavity inside the Cochlea, located in between the Scala tympani and the Scala
Physiology
The saccule gathers sensory information to orient the body in space. It primarily gathers information about linear movement in the vertical plane. The structures that enable to saccule to gather this vestibular information are the hair cells. Hair cells are the Sensory receptors of both the Auditory system and the Vestibular system in all Vertebrates. When the head tilts, the otolithic membrane slides over the hair cells in the direction of the tilt. This sliding bends the hair bundles of the hair cells, which causes stretching of the tip links and opening of the mechanically gated ion channels. Cations such as K+ rush into the hair cell cytosol, depolarizing it. Depolarization induces opening of voltage-gated Ca2+ channels at the basal aspect of the hair cell, which triggers exocytosis of neurotransmitter to the vestibular neurons. Exocytosis (ek-soh-sy-TOH-sis Greek: Έξω - external and κύτος - cell is the durable process by which a cell directs secretory vesicles out of the Cell See Chemical synapse for an introduction to concepts and terminology used in this article These impulses are communicated via the vestibular nerve to vestibular nuclei in the brainstem and medulla. The brain stem (or brainstem) is the lower part of the Brain, adjoining and structurally continuous with the Spinal cord. Impulses are also carried to the cerebellum via the inferior cerebral peduncles. The cerebellum ( Latin: "little brain" is a region of the Brain that plays an important role in the integration of sensory perception The cerebral peduncle, by most classifications is everything in the Mesencephalon except the Tectum.
See also
Additional images
 The membranous labyrinth. An otolith, (οτο- oto-, ear + λιθος lithos, a stone also called statoconium or otoconium is a structure in the Saccule |
 Vestibular system |
References
- Tortora, G. J. & Derrickson, B. (2006). "Principles of Anatomy and Physiology," 11th Edition. John Wiley and Sons, Inc.
External links
This article was originally based on an entry from a public domain edition of Gray's Anatomy. The public domain is a range of abstract materials &ndash commonly referred to as Intellectual property &ndash which are not owned or controlled by anyone Henry Gray's Anatomy of the Human Body (or Gray's Anatomy as it has commonly been shortened is an English-language Human anatomy Textbook As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.
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