Blood is transported through the body by the heart's pumping action. As we continue, we will enter the hepatic portal vein, which delivers blood from the gastrointestinal tract to the liver, into the ascending aorta, up towards the heart. As we approach the heart, it's pumping will pull us up into its chambers and through to the lungs where we will get oxygen and continue our journey to the kidneys. As we return to the heart, we will pass through the aortic arch and descend through the thoracic aorta continuing past the descending abdominal aorta until we reach the renal artery. We will make a left turn and pass through the glomeruli through the kidney's tubules and conclude this phase of our journey into the left kidney.
The last stage of our journey will take us through the kidney and into the urinary system where we will conclude our tour as we exit the human body. The human kidney is made up of the cortex, medulla, pyramids, papilla, renal pelvis, and calyces. In order to complete our journey, we must pass through a nephron back into the glomerulus. Each glomerulus is covered by the Bowman's capsule. Please note the high level of pressure present. This pressure is a necessary component of filtration in the kidneys. The glomeruli and Bowman's capsule make up a renal corpuscle. Filtration begins when the blood flowing through the glomeruli exerts pressure pushing water and dissolved substances out of the glomeruli and into the Bowman's capsule and continues filtration through the glomerular-capsular membrane. This glomberular filtration usually occurs at a rate of 125 ml per minute....
Unwanted wastes and substances move into urine through the distal and collecting tubules from blood in capillaries surrounding these tubules. This urine will drain out of the collecting tubules into the renal pelvis through the kidney's ureter and down into the urinary bladder. Notice the mucosal membrane that also coats the ureter and renal pelvis. The ureter has a thick, muscular wall that will help move urine down the ureter into the bladder through peristaltic contractions. To leave the body, we must travel past the trigone and down into the urethra where we will conclude our journey. The urethra in this test subject is approximately 8 inches in length.
In order to maintain a near perfect system, homeostasis must be maintained. The inability to maintain homeostasis may result in death or disease. The body's brain, kidneys, and liver help to maintain homeostasis in the closed system by removing, metabolizing, and digesting substances that are necessary for bodily function. The presence of toxins within the circulatory system may lead to diabetes, dehydration, hyper/hypoglycemia, and gout. The kidneys are responsible for the regulation of blood-water levels, reabsorption of substances into the bloodstream, the maintenance of salt and ion levels in the blood, regulation pH in the blood, and the excretion of urea and other wastes from the body.
Reference List:
Thibodeau, G. (1992). Structure and Function of the Body. Chicago: Mosby Year Book.
