Lymphatic Capillaries

-
.
These vessels are found in all body tissues except the central nervous system, which has a circulatory system known as the cerebrospinal system. The lymphatic capillaries run together to form larger ducts that intertwine about the arteries and veins. The lymph in these larger ducts, which are similar to thin, dilated veins, is moved along by the muscular movements of the body as a whole; it is prevented from moving back through the ducts by valves located along them at intervals. The ducts from the lower limbs and abdomen come together at the dorsal left side of the body to form a channel, known as the cisterna chyli, that gives rise to the chief lymphatic vessel of the body, the thoracic duct. This vessel receives lymph from the left side of the thorax, the left arm, and the left side of the head and neck; it empties into the junction of the left jugular and left subclavian veins. Another, smaller vessel, known as the right lymphatic duct, receives lymph from the right side of the thorax, the right arm, and the right side of the head and neck and empties its contents into the right subclavian vein.

Comments

Post a Comment

Popular posts from this blog

Cellular Respiration

-
Cellular Respiration, process in which cells produce the energy they need to survive. In cellular respiration, cells use oxygen to break down the sugar glucose and store its energy in molecules of adenosine triphosphate (ATP). Cellular respiration is critical for the survival of most organisms because the energy in glucose cannot be used by cells until it is stored in ATP. Cells use ATP to power virtually all of their activities—to grow, divide, replace worn out cell parts, and execute many other tasks. Cellular respiration provides the energy required for an amoeba to glide toward food, the Venus fly trap to capture its prey, or the ballet dancer to execute stunning leaps. Cellular respiration occurs within a cell constantly, day and night, and if it ceases, the cell—and ultimately the organism—dies. Two critical ingredients required for cellular respiration are glucose and oxygen. The glucose used in cellular respiration enters cells in a variety of ways. Plants, algae, and cer
Read more

The Human Eye

-
Image
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
Read more

Respiratory System

-
. Respiratory System, in anatomy and physiology, organs that deliver oxygen to the circulatory system for transport to all body cells. Oxygen is essential for cells, which use this vital substance to liberate the energy needed for cellular activities. In addition to supplying oxygen, the respiratory system aids in removing of carbon dioxide, preventing the lethal buildup of this waste product in body tissues. Day-in and day-out, without the prompt of conscious thought, the respiratory system carries out its life-sustaining activities. If the respiratory system’s tasks are interrupted for more than a few minutes, serious, irreversible damage to tissues occurs, followed by the failure of all body systems, and ultimately, death. While the intake of oxygen and removal of carbon dioxide are the primary functions of the respiratory system, it plays other important roles in the body. The respiratory system helps regulate the balance of acid and base in tissues, a process crucial for the norma
Read more