Kids Research Express

Sugar Metabolism, process by which the body uses sugar for energy. Carbohydrates, one of the three principal constituents of food, form the bulk of the average human diet. The end product of the digestion and assimilation of all forms of carbohydrate is a simple sugar, glucose , commonly called grape sugar when found in food, or blood sugar when found in the human body. The metabolism of fats and of certain protein substances also sometimes leads to the production of glucose. Glucose is the principal fuel that the muscles and other portions of the body consume to produce energy. It is present in every cell and almost every fluid of the body, and its concentration and distribution are among the most important processes in human physiology. A few other sugars are of comparatively minor importance in human physiology, notably lactose , or milk sugar, which is formed in the mammary glands of all lactating animals and is present in their milk. See Metabolism ; Sugar. More Articles: D...

Thalamus, a brain part, consists of two rounded masses of gray tissue lying within the middle of the brain, between the two cerebral hemispheres. The thalamus is the main relay station for incoming sensory signals to the cerebral cortex and for outgoing motor signals from it. All sensory input to the brain, except that of the sense of smell , connects to individual nuclei of the thalamus.

Phagocytosis (Greek -phagos, “one that eats”; kytos, “cell”), process of ingestion of matter by cells known, in this context, as phagocytes. Single-celled life forms that bodily engulf and ingest foreign matter—whether other cells, bacteria, or nonliving material—display phagocytosis. In multicellular organisms the process is relegated to specialized cells, generally for the purpose of defending the organism as a whole from potentially harmful invaders. In humans and other higher animals, phagocytes are wandering cells that occur throughout the body. Larger phagocytes, called macrophages, are particularly important in the lymph system, liver, and spleen; amoeboid macrophages also travel throughout the body's tissues, feeding on bacteria and other foreign matter. Smaller phagocytes, which are known as granular leukocytes—a type of white blood cell—are carried throughout the body by the bloodstream (see Blood ). Attracted to sites of infection by chemicals which are emitted by t...

Brain, portion of the central nervous system contained within the skull. The brain is the control center for movement, sleep, hunger, thirst, and virtually every other vital activity necessary to survival. All human emotions —including love, hate, fear, anger, elation, and sadness—are controlled by the brain. It also receives and interprets the countless signals that are sent to it from other parts of the body and from the external environment. The brain makes us conscious, emotional, and intelligent. THE HUMAN BRAIN The human brain has three major structural components: the large dome-shaped  cerebrum (top), the smaller somewhat spherical cerebellum (lower right), and the brainstem (center). Prominent in the brainstem are the medulla oblongata (the egg-shaped enlargement at center) and the  thalamus (between the medulla and the cerebrum). The cerebrum is responsible for intelligence and reasoning. The cerebellum helps to maintain balance and posture. The medulla i...

Structure of the Eye The amount of light entering the eye (right) is controlled by the pupil, which dilates and contracts accordingly. The cornea and lens, whose shape is adjusted by the ciliary body, focus the light on the retina, where receptors convert it into nerve signals that pass to the brain. A mesh of blood vessels, the choroid, supplies the retina with oxygen and sugar. Lacrimal glands (left) secrete tears that wash foreign bodies out of the eye and keep the cornea from drying out. Blinking compresses and releases the lacrimal sac, creating a suction that pulls excess moisture from the eye’s surface. The entire eye , often called the eyeball, is a spherical structure approximately 2.5 cm (about 1 in) in diameter with a pronounced bulge on its forward surface. The outer part of the eye is composed of three layers of tissue. The outside layer is the sclera, a protective coating. It covers about five-sixths of the surface of the eye. At the front of the eyeball, it is continuo...

Eye (anatomy), light-sensitive organ of vision in animals. The eyes of various species vary from simple structures that are capable only of differentiating between light and dark to complex organs, such as those of humans and other mammals, that can distinguish minute variations of shape, color, brightness, and distance. The actual process of seeing is performed by the brain rather than by the eye. The function of the eye is to translate the electromagnetic vibrations of light into patterns of nerve impulses that are transmitted to the brain . Related Topics: Human Eye ,  Functioning of the Eye Eye Protective Structures Eye Comparative Anatomy Eye Diseases

Fallopian Tube, one of two ducts in female mammals leading from the ovaries to the upper part of the uterus . They are also known as oviducts. In the human female the fallopian tubes are about 2 cm (about 0.75 in) thick and 10 to 13 cm (4 to 5 in) long. As the ovum leaves the ovary it passes into the mouth of the adjoining fallopian tube and is propelled toward the uterus by hairlike projections called cilia on the inner surface of the tube. If the ovum is fertilized inside the tube, where most fertilization takes place, it usually implants in the uterus. Some fertilized ova, however, implant in the fallopian tube itself and must be surgically excised. The condition is called an ectopic pregnancy. Many cases of infertility in women are due to blocked fallopian tubes, which can result from infection, especially that which is contracted from sexually transmitted disease. Surgical severing and sealing of the fallopian tubes is a common method of preventing pregnancy. These tubes were n...