Respiration,+Circulation,+and+Excretion

__ **Respiratory, Circulatory, and Excretion** __
** The Respiratory System ** The Respiratory system contains two large organs known as the lungs. The left lung is slightly smaller than the right to make room for the heart. The main passageways are the throat, the windpipe, and the bronchi. The major function of the respiratory system is the gas exchange, also called respiration, between the external environment and the circulatory system. In humans and mammals, this exchange facilitates [|oxygenation] of the blood with a concomitant removal of carbon dioxide and other gaseous [|metabolic wastes] from the [|circulation]. As gas exchange occurs, the acid-base balance of the body is maintained as part of [|homeostasis]. This process begins when air is taken into the body by the nose or mouth. It is then taken into the throat, passes the epiglottis, and moves through the pharynx. Then it passes through the trachea, which leads to two tubes, or bronchi, which leads into the lungs. The lungs, nasal captivity, trachea, and bronchi are all lined with ciliated cells that secrete mucus to prevent unwanted materials from reaching the lungs. Alveoli are the sacs of lungs where oxygen and carbon dioxide are exchanged by diffusion between the air and blood. ** Circulatory System ** ** The Urinary System ** The Urinary system contains two kidneys, a pair of ureters, the urinary bladder, and the urethra. The kidneys filter the blood to remove waste, to maintain homeostasis. Each kidney connects to the tube called the ureter, which lead into the Urinary bladder. The urinary bladder stores wastes. The kidneys each contain about 1 million tiny filters. Each of these filtering units is called a nephron. As blood flows into the nephron, it is under high pressure and flows into a bed of capillaries called the glomerulus. Water, amino acids, proteins, glucose, vitamins, urea, salts, and ions from the blood pass out of the capillaries into part of the nephron called Bowman’s capsule. These pass through a tube and enter the bloodstream. This helps maintain homeostasis. The liquid that remains in the tubes is called urine.
 * __ The Passageway and Lungs __**
 * __ The Process of Gas Exchange __**
 * Blood, the heart, and blood vessels form the circulatory system
 * Blood is composed of fluid, cells, and fragments of cells.
 * Blood caries oxygen from the lungs and nutrients from the digestive system to cells, then hauls away cellular wastes.
 * Red blood cells carry oxygen to body cells. They make up 44% of blood, and are only in circulation for about 120 days.
 * Red blood cells are produced in the marrow of long bones.
 * Red blood cells contain hemoglobin which bonds with oxygen and carbon dioxide.
 * The fluid portion of blood is plasma.
 * Plasma contains proteins and transports red and white blood cells. It makes up 55% of blood.
 * White blood cells defend the body against disease; they make up only 1% of blood.
 * Platelets are used for blood clotting. They are removed from the blood by the spleen and liver after about one week.
 * RH= Rhesus factor. This is an inherited characteristic that can cause complications in some pregnancies where a RH- mother becomes pregnant with a RH+ baby; the mother will begin to produce anti-RH+ antibodies which can destroy red blood cells in a future fetus.
 * Arteries carry blood from the heart. They divide into smaller arteries that divide into arterioles. Arterioles enter tissues where they branch into the smallest blood vessels; capillaries. Capillaries merge into venules, which merge to form veins.
 * The surge of blood through an artery is called a pulse.
 * Blood pressure is the force the blood exerts on the blood vessels. It rises and falls with each heartbeat.