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Neural Canal
In the developing chordate (including vertebrates), the neural tube is the embryonic precursor to the central nervous system, which is made up of the brain and spinal cord. The neural groove gradually deepens as the neural fold become elevated, and ultimately the folds meet and coalesce in the middle line and convert the groove into the closed neural tube. In humans, neural tube closure usually occurs by the fourth week of pregnancy (the 28th day after conception). The ectodermal wall of the tube forms the rudiment of the nervous system. The centre of the tube is the ''neural canal''.It is an important structure for the development of fetus's brain and spine Development The neural tube develops in two ways: primary neurulation and secondary neurulation. Primary neurulation divides the ectoderm into three cell types: * The internally located neural tube * The externally located epidermis * The neural crest cells, which develop in the region between the neural tube and epidermi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anatomical Terms Of Location
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provides a definition of what is at the front ("anterior"), behind ("posterior") and so on. As part of defining and describing terms, the body is described through the use of anatomical planes and anatomical axes. The meaning of terms that are used can change depending on whether an organism is bipedal or quadrupedal. Additionally, for some animals such as invertebrates, some terms may not have any meaning at all; for example, an animal that is radially symmetrical will have no anterior surface, but can still have a description that a part is close to the middle ("proximal") or further from the middle ("distal"). International organisations have determined vocabularies that are often used as standard vocabularies for subdisciplines of anatom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of living fish species are ray-finned fish, belonging to the class Actinopterygii, with around 99% of those being teleosts. The earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed external armor that protected them from predators. The first fish with jaws appeared in the Silurian period, after which many (such as sharks) became formidable marine predators rather than just the prey of arthropods. Mos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metencephalon
The metencephalon is the embryonic part of the hindbrain that differentiates into the pons and the cerebellum. It contains a portion of the fourth ventricle and the trigeminal nerve (CN V), abducens nerve (CN VI), facial nerve (CN VII), and a portion of the vestibulocochlear nerve (CN VIII). Embryology The metencephalon develops from the higher/rostral half of the embryonic rhombencephalon, and is differentiated from the myelencephalon in the embryo by approximately 5 weeks of age. By the third month, the metencephalon differentiates into its two main structures, the pons and the cerebellum. Functions The pons regulates breathing through particular nuclei that regulate the breathing center of the medulla oblongata. The cerebellum works to coordinate muscle movements, maintain posture, and integrate sensory information from the inner ear and proprioceptors in the muscles and joints. Development At the early stages of brain development, the brain vesicles that are formed ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypothalamus
The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus is located below the thalamus and is part of the limbic system. In the terminology of neuroanatomy, it forms the ventral part of the diencephalon. All vertebrate brains contain a hypothalamus. In humans, it is the size of an almond. The hypothalamus is responsible for regulating certain metabolic processes and other activities of the autonomic nervous system. It synthesizes and secretes certain neurohormones, called releasing hormones or hypothalamic hormones, and these in turn stimulate or inhibit the secretion of hormones from the pituitary gland. The hypothalamus controls body temperature, hunger, important aspects of parenting and maternal attachment behaviours, thirst, fatigue, sleep, and circadian rhythms. Structure T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optic Vesicle
The eyes begin to develop as a pair of diverticula (pouches) from the lateral aspects of the forebrain. These diverticula make their appearance before the closure of the anterior end of the neural tube; after the closure of the tube around the 4th week of development, they are known as the optic vesicles. Previous studies of optic vesicles suggest that the surrounding extraocular tissues – the surface ectoderm and extraocular mesenchyme – are necessary for normal eye growth and differentiation. They project toward the sides of the head, and the peripheral part of each expands to form a hollow bulb, while the proximal part remains narrow and constitutes the optic stalk, which goes on to form the optic nerve. Additional images File:Gray460.png, Head of chick embryo of about thirty-eight hours’ incubation, viewed from the ventral surface. X 26 See also * Eye development Eye formation in the human embryo begins at approximately three weeks into embryonic development ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diencephalon
The diencephalon (or interbrain) is a division of the forebrain (embryonic ''prosencephalon''). It is situated between the telencephalon and the midbrain (embryonic ''mesencephalon''). The diencephalon has also been known as the 'tweenbrain in older literature. It consists of structures that are on either side of the third ventricle, including the thalamus, the hypothalamus, the epithalamus and the subthalamus. The diencephalon is one of the main vesicles of the brain formed during embryogenesis. During the third week of development a neural tube is created from the ectoderm, one of the three primary germ layers. The tube forms three main vesicles during the third week of development: the prosencephalon, the mesencephalon and the rhombencephalon. The prosencephalon gradually divides into the telencephalon and the diencephalon. Structure The diencephalon consists of the following structures: *Thalamus *Hypothalamus including the posterior pituitary *Epithalamus which consists of: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cerebrum
The cerebrum, telencephalon or endbrain is the largest part of the brain containing the cerebral cortex (of the two cerebral hemispheres), as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. In the human brain, the cerebrum is the uppermost region of the central nervous system. The cerebrum prenatal development, develops prenatally from the forebrain (prosencephalon). In mammals, the Dorsum (biology), dorsal telencephalon, or Pallium (neuroanatomy), pallium, develops into the cerebral cortex, and the ventral telencephalon, or Pallium (neuroanatomy), subpallium, becomes the basal ganglia. The cerebrum is also divided into approximately symmetric Lateralization of brain function, left and right cerebral hemispheres. With the assistance of the cerebellum, the cerebrum controls all voluntary actions in the human body. Structure The cerebrum is the largest part of the brain. Depending upon the position of the animal it lies eithe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telencephalon
The cerebrum, telencephalon or endbrain is the largest part of the brain containing the cerebral cortex (of the two cerebral hemispheres), as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. In the human brain, the cerebrum is the uppermost region of the central nervous system. The cerebrum develops prenatally from the forebrain (prosencephalon). In mammals, the dorsal telencephalon, or pallium, develops into the cerebral cortex, and the ventral telencephalon, or subpallium, becomes the basal ganglia. The cerebrum is also divided into approximately symmetric left and right cerebral hemispheres. With the assistance of the cerebellum, the cerebrum controls all voluntary actions in the human body. Structure The cerebrum is the largest part of the brain. Depending upon the position of the animal it lies either in front or on top of the brainstem. In humans, the cerebrum is the largest and best-developed of the five major divi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hindbrain
The hindbrain or rhombencephalon or lower brain is a developmental categorization of portions of the central nervous system in vertebrates. It includes the medulla, pons, and cerebellum. Together they support vital bodily processes. Metencephalon Rhombomeres Rh3-Rh1 form the metencephalon. The metencephalon is composed of the pons and the cerebellum; it contains: * a portion of the fourth (IV) ventricle, * the trigeminal nerve (CN V), * abducens nerve (CN VI), * facial nerve (CN VII), * and a portion of the vestibulocochlear nerve (CN VIII). Myelencephalon Rhombomeres Rh8-Rh4 form the myelencephalon. The myelencephalon forms the medulla oblongata in the adult brain; it contains: * a portion of the fourth ventricle, * the glossopharyngeal nerve (CN IX), * vagus nerve (CN X), * accessory nerve (CN XI), * hypoglossal nerve (CN XII), * and a portion of the vestibulocochlear nerve (CN VIII). Evolution The hindbrain is homologous to a part of the arthropod brain known as the sub- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Midbrain
The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal (alertness), and temperature regulation. The name comes from the Greek ''mesos'', "middle", and ''enkephalos'', "brain". Structure The principal regions of the midbrain are the tectum, the cerebral aqueduct, tegmentum, and the cerebral peduncles. Rostrally the midbrain adjoins the diencephalon (thalamus, hypothalamus, etc.), while caudally it adjoins the hindbrain (pons, medulla and cerebellum). In the rostral direction, the midbrain noticeably splays laterally. Sectioning of the midbrain is usually performed axially, at one of two levels – that of the superior colliculi, or that of the inferior colliculi. One common technique for remembering the structures of the midbrain involves visualizing these cross-sections (especially at the level of the superior colliculi) as the upside-down face of a be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forebrain
In the anatomy of the brain of vertebrates, the forebrain or prosencephalon is the Anatomical terms of location#Directional terms, rostral (forward-most) portion of the brain. The forebrain (prosencephalon), the midbrain (mesencephalon), and hindbrain (rhombencephalon) are the three Brain vesicle, primary brain vesicles during the early development of the nervous system. The forebrain controls body temperature, reproductive functions, eating, sleeping, and the display of emotions. At the five-vesicle stage, the forebrain separates into the diencephalon (thalamus, hypothalamus, subthalamus, and epithalamus) and the telencephalon which develops into the cerebrum. The cerebrum consists of the cerebral cortex, underlying white matter, and the basal ganglia. In humans, by 5 weeks in utero it is visible as a single portion toward the front of the fetus. At 8 weeks in utero, the forebrain splits into the left and right cerebral hemispheres. When the embryonic forebrain fails to divide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neuroepithelial Cells
Neuroepithelial cells, or neuroectodermal cells, form the wall of the closed neural tube in early embryonic development. The neuroepithelial cells span the thickness of the tube's wall, connecting with the pial surface and with the ventricular or lumenal surface. They are joined at the lumen of the tube by junctional complexes, where they form a pseudostratified layer of epithelium called neuroepithelium. Neuroepithelial cells are the stem cells of the central nervous system, known as neural stem cells, and generate the intermediate progenitor cells known as radial glial cells, that differentiate into neurons and glia in the process of neurogenesis. Embryonic neural development Brain development During the third week of embryonic growth the brain begins to develop in the early fetus in a process called morphogenesis. Neuroepithelial cells of the ectoderm begin multiplying rapidly and fold in forming the neural plate, which invaginates during the fourth week of embryonic growth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
