Anus The opening at the lower end of the alimentary canal through which solid waste is eliminated from the body.
Branchial arches The bony or cartilaginous arches which support the gills on each side of the throat of fishes and amphibians.
Corpuscles of Stannius These are islands of eosinophilic granular cells located in paired organs on the ventral surface of the kidney. This organ secretes a protein called hypocalcin (teleocalcin) that acts with calcitonin to regulate calcium metabolism.
Diencephalon The posterior part of the forebrain that connects the midbrain with the cerebral hemispheres, encloses the third ventricle, and contains the thalamus and hypothalamus. Also called betweenbrain, interbrain, thalamencephalon.
Ears The vertebrate organ of hearing, responsible for maintaining equilibrium as well as sensing sound and divided in mammals into the external ear, the middle ear, and the inner ear.
Epiphysis A small body that arises from the roof of the third ventricle and is enclosed by the pia mater and that functions primarily as an endocrine gland that produces melatonin called also pineal, pineal body, pineal organ.
Epithelia Membranous tissue composed of one or more layers of cells separated by very little intercellular substance and forming the covering of most internal and external surfaces of the body and its organs.
Eye Either of a pair of hollow structures located in bony sockets of the skull, functioning together or independently, each having a lens capable of focusing incident light on an internal photosensitive retina from which nerve impulses are sent to the brain; the vertebrate organ of vision.
Fins A membranous appendage extending from the body of a fish or other aquatic animal, used for propelling, steering, or balancing the body in the water.
Forebrain The most anterior of the three primary regions of the embryonic brain which includes the cerebrum, thalamus, and hypothalamus.
Gut The alimentary canal or a portion thereof, especially the intestine or stomach.
Heart The chambered muscular organ in vertebrates and invetebrates that pumps blood received from the veins into the arteries, thereby maintaining the flow of blood through the entire circulatory system.
Hindbrain The lower or hind region of the embryonic brain from which the metencephalon and myelencephalon develop, it comprises of the pons and medulla oblongata.
Intestine The portion of the alimentary canal extending from the stomach to the anus and, in humans and other mammals, consisting of two segments, the small intestine and the large intestine.
Jaw Either of two bony or cartilaginous structures that in most vertebrates form the framework of the mouth and hold the teeth.
Lateral line A series of sensory pores along the head and sides of fish and some amphibians by which water currents, vibrations, and pressure changes are detected.
Lens A transparent, biconvex body of the eye between the iris and the vitreous humor that focuses light rays entering through the pupil to form an image on the retina.
Midbrain The middle division of the three primary divisions of the developing vertebrate brain or the corresponding part of the adult brain that includes a ventral part containing the cerebral peduncles and a dorsal tectum containing the corpora quadrigemina and that surrounds the aqueduct of Sylvius connecting the third and fourth ventricles called also mesencephalon.
Mouth The cavity lying at the upper end of the alimentary canal, bounded on the outside by the lips and inside by the oropharynx and containing in higher vertebrates the tongue, gums, and teeth.
Neural tubes A dorsal tubular structure in the vertebrate embryo formed by longitudinal folding of the neural plate and differentiating into the brain and spinal cord.
Neuromast A group or tube of neuroepithelial cells along the lateral line.
Notochord A flexible rodlike structure that forms the main support of the body in the lowest chordates, such as the lancelet; a primitive backbone. A similar structure in embryos of higher vertebrates, from which the spinal column develops.
Olfactory pits A depression on the head of an embryo that becomes converted into a nasal passage called also nasal sac.
Oligodendrocytes One of the cells comprising the oligodendroglia.
Oligodendroglia Neuroglia consisting of cells similar to but smaller than astrocytes, found in the central nervous system and associated with the formation of myelin.
Pericard The membranous sac filled with serous fluid that encloses the heart and the roots of the aorta and other large blood vessels.
Pigment cell A pigment-bearing cell especially in the skin.
Retina A delicate, multilayered, light-sensitive membrane lining the inner eyeball and connected by the optic nerve to the brain.
Rhombomere Neuromeres or segments in the hindbrain region that are of developmental significance.
Roof plate The most dorsal subdivision of the embryonic neural tube, a dorsal signaling center.
Skeleton The internal structure composed of bone and cartilage that protects and supports the soft organs, tissues, and other parts of a vertebrate organism; endoskeleton.
Skin The membranous tissue forming the external covering or integument of an animal and consisting in vertebrates of the epidermis and dermis.
Somites A segmental mass of mesoderm in the vertebrate embryo, occurring in pairs along the notochord and developing into muscles and vertebrae.
Spinal cord The thick, whitish cord of nerve tissue that extends from the medulla oblongata down through the spinal column and from which the spinal nerves branch off to various parts of the body.
Stomach The enlarged, saclike portion of the alimentary canal, one of the principal organs of digestion, located in vertebrates between the esophagus and the small intestine.
Swim bladder An air-filled sac near the spinal column in many fishes that helps maintain buoyancy.
Tegmentum A ventral part of the midbrain consisting of white fibers running lengthwise through gray matter.
Throat The portion of the digestive tract that lies between the rear of the mouth and the esophagus and includes the fauces and the pharynx.
Yolk A corresponding portion of the egg of other animals, consisting of protein and fat that serve as the primary source of nourishment for the early embryo and protoplasmic substances from which the embryo develops.