The human body is the entire structure of a human organism and comprises a head, neck, torso, two arms and two legs. By the time the human reaches adulthood, the body consists of close to 100 trillion cells, the basic unit of life. These cells are organised biologically to eventually form the whole body.
Cranial nerves are nerves that emerge directly from the brain, in contrast to spinal nerves, which emerge from segments of the spinal cord. In humans, there are traditionally twelve pairs of cranial nerves (although an additional anterior pair of nerves, numbered 0, also exists). The first three pairs (including nerve 0) emerge from the cerebrum; the remaining ten pairs emerge from the brainstem.
The cranial nerves are part of the peripheral nervous system (PNS), with the exception of cranial nerve II (the optic nerve), which is not a true peripheral nerve but a tract of the diencephalon leading to the retina; both the optic nerve and the retina are hence part of the central nervous system (CNS). The axons of the remaining twelve nerves extend beyond the brain and are therefore considered part of the PNS. The ganglia of the cranial nerves originate in the CNS.
The reproductive system or genital system is a system of sex organs within an organism which work together for the purpose of reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system.[dead link] Unlike most organ systems, the sexes of differentiated species often have significant differences. These differences allow for a combination of genetic material between two individuals, which allows for the possibility of greater genetic fitness of the offspring.
Sexual arousal (also sexual excitement) is the arousal of sexual desire, during or in anticipation of sexual activity. A number of physiological responses occur in the body and mind as preparation for sex and continue during it. Genital responses are not the only changes, but noticeable and necessary for consensual and comfortable intercourse. Male arousal will lead to an erection and in female arousal, the body's response is engorged sexual tissues such as nipples, vulva, clitoris, vaginal walls and vaginal lubrication. Mental stimuli and physical stimuli such as touch, and the internal fluctuation of hormones, can influence sexual arousal.
Sexual arousal has several stages and may not lead to any actual sexual activity, beyond a mental arousal and the physiological changes that accompany it. Given sufficient sexual stimulation, sexual arousal in humans reaches its climax during an orgasm. It may also be pursued for its own sake, even in the absence of an orgasm.
A sex organ or primary sexual characteristic, as narrowly defined, is any anatomical part of the body involved in sexual reproduction and constituting the reproductive system in a complex organism, especially the external sex organs; the external sex organs are also commonly referred to as the genitalia or genitals.
Flowers are the reproductive organs of flowering plants, cones are the reproductive organs of coniferous plants, whereas mosses, ferns, and other similar plants have gametangia for reproductive organs.
Clitoral erection is a physiological phenomenon where the clitoris becomes enlarged and firm. Clitoral erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual arousal.
Science of drugs including their origin, composition, pharmacokinetics,
pharmacodynamics, therapeutic use, and toxicology.
Pharmacology (from Greek φάρμακον, pharmakon, "poison" in classic Greek; "drug" in modern Greek; and -λογία, -logia "study of", "knowledge of") is the branch of medicine and biology concerned with the study of drug action, where a drug can be broadly defined as any man-made, natural, or endogenous (within the body) molecule which exerts a biochemical and/or physiological effect on the cell, tissue, organ, or organism. More specifically, it is the study of the interactions that occur between a living organism and chemicals that affect normal or abnormal biochemical function. If substances have medicinal properties, they are considered pharmaceuticals.