The inner ear is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the temporal bone of the skull with a system of passages comprising two main functional parts:
In human anatomy, the thoracic duct is the larger of the two lymph ducts of the lymphatic system. It is also known as the left lymphatic duct, alimentary duct, chyliferous duct, and Van Hoorne's canal. The other duct is the right lymphatic duct. The thoracic duct carries chyle, a liquid containing both lymph and emulsified fats, rather than pure lymph. It also collects most of the lymph in the body other than from the right thorax, arm, head, and neck. The thoracic duct usually starts from the level of the twelfth thoracic vertebra (T12) and extends to the root of the neck. It drains into the systemic (blood) circulation at the junction of the left subclavian and internal jugular veins, at the commencement of the brachiocephalic vein.
The semicircular canals or semicircular ducts are three semicircular, interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the horizontal, superior and posterior semicircular canals.
The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail. It is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders. Several bony landmarks of the lacrimal bone function in the process of lacrimation or crying. Specifically, the lacrimal bone helps form the nasolacrimal canal necessary for tear translocation. A depression on the anterior inferior portion of the bone, the lacrimal fossa, houses the membranous lacrimal sac. Tears or lacrimal fluid, from the lacrimal glands, collect in this sac during excessive lacrimation. The fluid then flows through the nasolacrimal duct and into the nasopharynx. This drainage results in what is commonly referred to a runny nose during excessive crying or tear production. Injury or fracture of the lacrimal bone can result in posttraumatic obstruction of the lacrimal pathways.
The saccule is a bed of sensory cells in the inner ear. It translates head movements into neural impulses for the brain to interpret. The saccule detects linear accelerations and head tilts in the vertical plane. 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.
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents. In the adult human, the volume of the orbit is 30 millilitres, of which the eye occupies 6.5 ml. The orbital contents comprise the eye, the orbital and retrobulbar fascia, extraocular muscles, cranial nerves II, III, IV, V, and VI, blood vessels, fat, the lacrimal gland with its sac and duct, the eyelids, medial and lateral palpebral ligaments, cheek ligaments, the suspensory ligament, septum, ciliary ganglion and short ciliary nerves.
The lacrimal glands are paired exocrine glands, one for each eye, found in most terrestrial vertebrates and some marine mammals, that secrete the aqueous layer of the tear film. In humans, they are situated in the upper lateral region of each orbit, in the lacrimal fossa of the orbit formed by the frontal bone. Inflammation of the lacrimal glands is called dacryoadenitis. The lacrimal gland produces tears which are secreted by the lacrimal ducts, and flow over the ocular surface, and then into canals that connect to the lacrimal sac. From that sac, the tears drain through the lacrimal duct into the nose.
The mediastinum is the central compartment of the thoracic cavity. Surrounded by loose connective tissue, it is an undelineated region that contains a group of structures within the thorax, namely the heart and its vessels, the esophagus, the trachea, the phrenic and cardiac nerves, the thoracic duct, the thymus and the lymph nodes of the central chest.
The orbital or horizontal part of the frontal bone consists of two thin triangular plates, the orbital plates, which form the vaults of the orbits, and are separated from one another by a median gap, the ethmoidal notch.
The external anal sphincter is a flat plane of skeletal muscle fibers, elliptical in shape and intimately adherent to the skin surrounding the margin of the anus.
The foregut is the anterior part of the alimentary canal, from the mouth to the duodenum at the entrance of the bile duct. Beyond the stomach, the foregut is attached to the abdominal walls by mesentery. The foregut arises from the endoderm, developing from the folding primitive gut, and is developmentally distinct from the midgut and hindgut. Although the term “foregut” is typically used in reference to the anterior section of the primitive gut, components of the adult gut can also be described with this designation. Pain in the epigastric region, just below the intersection of the ribs, typically refers to structures in the adult foregut.
The transversalis fascia is a thin aponeurotic membrane of the abdomen. It lies between the inner surface of the transverse abdominal muscle and the parietal peritoneum.
The infraorbital artery is an artery in the head that branches off the maxillary artery, emerging through the infraorbital foramen, just under the orbit of the eye.
At the hinder part of the medial wall of the vestibule is the orifice of the vestibular aqueduct, which extends to the posterior surface of the petrous portion of the temporal bone.
From the posterior wall of the saccule a canal, the endolymphatic duct, is given off; this duct is joined by the utriculosaccular duct, and then passes along the vestibular aqueduct and ends in a blind pouch, the endolymphatic sac, on the posterior surface of the petrous portion of the temporal bone, where it is in contact with the dura mater. Studies suggest that the endolymphatic duct and endolymphatic sac perform both absorptive and secretory, as well as phagocytic and immunodefensive, functions.
The vestibule is the central part of the bony labyrinth in the inner ear, and is situated medial to the eardrum, behind the cochlea, and in front of the three semicircular canals.
The following outline is provided as an overview of and topical guide to human anatomy:
Jakob Ernst Arthur Böttcher was a Baltic German pathologist and anatomist who was a native of Bauska, in what was then the Courland Governorate. He worked primarily within the Russian Empire.
Large vestibular aqueduct is a structural deformity of the inner ear. Enlargement of this duct is one of the most common inner ear deformities and is commonly associated with hearing loss during childhood. The term was first discovered in 1791 by Mondini when he was completing a temporal bone dissection. It was then defined by Valvassori and Clemis as a vestibular aqueduct that is greater than or equal to 2.0 mm at the operculum and/or greater than or equal to 1.0 mm at the midpoint. Some use the term enlarged vestibular aqueduct syndrome but this is felt by others to be erroneous as it is a clinical finding which can occur in several syndromes.
An endolymphatic sac tumor (ELST) is a very uncommon papillary epithelial neoplasm arising within the endolymphatic sac or endolymphatic duct. This tumor shows a very high association with Von Hippel–Lindau syndrome (VHL).
