Anatomical structure

The aorta (pronounced "ay-OR-tuh") is the largest artery in the human body, originating from the left ventricle of the heart and bringing oxygenated blood to all parts of the body in the systemic circulation. The aorta is usually divided into seven segments/sections : The aorta is a hard artery, and as such is quite distensible. When the left ventricle contracts to force blood into the aorta, the aorta expands. This stretching gives the potential energy that will help maintain blood pressure...

The entorhinal cortex (EC) is an important memory center in the brain. The EC forms the main input to the hippocampus and is responsible for the pre-processing (familiarity) of the input signals. In the reflex nictitating membrane response of classical trace conditioning, the association of impulses from the eye and the ear occurs in the entorhinal cortex. The EC-hippocampus system plays an important role in memory consolidation and memory optimization in sleep. Entorhinal cortex is one of...

A spermatozoon or spermatozoan (pl. spermatozoa), from the ancient Greek σπέρμα (seed) and (living being) and more commonly known as a sperm cell, is the haploid cell that is the male gamete. It joins an ovum to form a zygote. A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo. Sperm cells contribute half of the genetic information to the diploid offspring. In mammals, the sex of the offspring is determined by the sperm cells: a spermatozoon...

In anatomy, the urinary bladder is a hollow, muscular, and distensible (or elastic) organ that sits on the pelvic floor in mammal. It is the organ that collects urine excreted by the kidney prior to disposal by urination. Urine enters the bladder via the ureter and exits via the urethra. In males, the bladder is superior to the prostate, and separated from the rectum by the rectovesical excavation. In females, the bladder is separated from the rectum by the rectouterine excavation, and it is...

White matter is one of the three main solid components of the central nervous system designated by color. The other two are gray matter and substantia nigra. White matter is composed of myelin nerve cell processes, or axon, which connect various gray matter areas (the locations of nerve cell bodies) of the brain to each other and carry nerve impulse between neurons. Cerebral and spinal white matter do not contain dendrite, which can only be found in gray matter along with neural cell bodies...

The vagus nerve (VĀ-gəs) (also called pneumogastric nerve or cranial nerve X) is the tenth of twelve paired cranial nerves, and is the only nerve that starts in the brainstem (within the medulla oblongata) and extends, through the jugular foramen, down below the head, to the neck, chest and abdomen, where it contributes to the innervation of the viscera. The medieval Latin word vagus means literally "Wandering" (the words vagrant, vagabond, and vague come from the same root). Sometimes the...

The putamen is a structure in the middle of the brain, which, together with the caudate nucleus forms the dorsal striatum. The putamen is a portion of the basal ganglia that forms the outermost part of the lenticular nucleus. It appears to play a role in reinforcement learning. The motor and somatosensory cortices, the intralaminar nuclei of the thalamus, and the substantia nigra project to the putamen. The putamen projects to premotor and supplementary motor area of cortex via the globus...

The germ layer mesoderm forms in the embryo of animal more complex than cnidaria, making them triploblastic. Mesoderm forms during gastrulation when some of the cells migrating inward to form the endoderm form an additional layer between the endoderm and the ectoderm. This key innovation evolved hundreds of millions of years ago and led to the evolution of nearly all large, complex animals. The formation of a mesoderm led to the formation of a coelom. Organs formed inside a coelom (body...

Broca's area is a section of the human brain that is involved in language processing, speech or sign production, and comprehension. Broca's area is named after the 19th-century physician Paul Broca. The concept of Broca's Area was originally produced with the intent to explain how speech production was inhibited in the learning of communication by the deaf; however, it is currently used to describe many anatomical aspects of psychological processing mechanisms. Broca's area is located in the...

The substantia nigra (Latin for "black substance", Sömmering) or locus niger is a heterogeneous portion of the midbrain, separating the pes (foot) from the tegmentum (covering), and an accessory to the basal ganglia system. It consists of two strongly contrasted ensembles, the pars compacta and adjacent dopaminergic groups, and another ensemble made up of the pars reticulata and the pars lateralis. The latter two, along with the pallidal nuclei, are elements of the core of the basal ganglia....

In some male mammal the scrotum is a protuberance of skin and muscle containing the testicle. It is an extension of the abdomen, and is located between the penis and anus. In humans and some other mammals, the base of the scrotum becomes covered with pubic hair at puberty. In common speech, the scrotum is often improperly referred to as the testicles, which actually refer to organs encased inside the scrotum. The scrotum is homologous to the labia majora in females. It becomes tight when...

The inner ear is the bony labyrinth, a system of passages comprising two main functional parts: Inner ears are found in all vertebrates, with substantial variations in the form and function of their sensory organs. Each animal has two inner ears, one on each side of its head. In mammals, the outer ear focuses and directs sound waves into the middle ear. In the middle ear, the energy of these pressure waves is translated into mechanical vibrations of the middle ear’s bone structure. The...

The pituitary gland, or hypophysis, is an endocrine gland about the size of a pea. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity (sella turcica) covered by a dural fold (diaphragma sellae). The pituitary fossa, in which the pituitary gland sits, is situated in the sphenoid bone in the middle cranial fossa at the base of the brain. The pituitary gland secretes hormone regulating homeostasis, including trophic hormone that...

The colon is a storage tube for solid wastes. The main function of the colon appears to be extraction of water and salts from feces. In mammal, it consists of the ascending colon, transverse colon, the descending colon, and the sigmoid colon. The colon from cecum to the splenic flexure (the junction between the transverse and descending colon) is also known as the right colon. The remainder is known as the left colon. The location of the parts of the colon are either in the abdominal cavity or...

The pharynx (plural: pharynges) is the part of the neck and throat situated immediately posterior to (behind) the mouth and nasal cavity, and cranial, or superior, to the esophagus, larynx, and trachea. It is part of the digestive system and respiratory system of many organisms. Because both food and air pass through the pharynx, a flap of connective tissue called the epiglottis closes over the trachea when food is swallowed to prevent choking or aspiration. In humans the pharynx is...