. The kidneys contain millions of _________, which are the smallest functional units of the kidneys since each one can make urine from blood.
2. There are 3 stages in urine formation. The first stage is called____________; during this stage, blood pressure pushes water and small solutes out of a ball of capillaries called the __________ into the first part of the renal tubule called the _________ _________.
3. The second stage of urine formation is called _________. Cells lining the proximal convoluted tubules (PCTs) have special projections called _________ which increase their surface area, thus enabling the PCTs to transport about 70% of filtrate back into blood.
4. When a person is dehydrated, their blood volume and blood pressure are too low. Two hormones reduce the loss of sodium and water from the body during dehydration by concentrating urine to prevent further water loss. The first hormone is secreted by the adrenal cortex and is called __________; this hormone stimulates sodium retention by nephrons. The second hormone is released by the posterior pituitary gland and is called _________; this hormone cause water retention by nephrons.
5. ___________is the waste product of cellular respiration (ATP synthesis). This waste product must be eliminated from the body because it becomes toxic at high levels. This waste product combines with water in blood to form carbonic acid, which is then converted into bicarbonate ions (HCO3-) and hydrogen ions (H+). Hydrogen ions lower blood pH, causing it to become too acidic. Kidneys are able to sense high H+ levels in blood and actively transport hydrogen ions (and other toxic blood borne chemicals) from blood into urine during ___________, the third stage of urine formation.
6. Urine and blood differ in composition. In a healthy person, blood contains _________ , __________, and _________ but urine DOES NOT these materials.
7. Urine moves from the kidneys down the ureters into the bladder due to __________, a form of motility wherein _________ muscle tissue in the ureteral walls undergoes rhythmic waves of contractions.
8. The kidneys are located in the ___________ cavity; ureters conduct urine to the urinary bladder which is located in the pelvic cavity behind the symphysis joint of the _________ bones.
9. The three major systems which participate in the excretion of cellular wastes from blood include: the __________ system which eliminates urea and excess electrolytes like sodium; the ___________ system which eliminates water and salt; and the ____________ system, which eliminates carbon dioxide.
10. When the bladder is full, the _____________ reflex is initiated. During this reflex, the bladder walls contract and the ________ ________ sphincter, a circular structure made of _______ ______tissue, relaxes. Upon sensing an urge to urinate, a person can consciously contract their _______ _______ sphincter, a circular structure made of ________ ________ tissue - this stops the flow of urine out of the bladder and into the urethra until the time is convenient to urinate.
REFERENCE CITATIONS: _______________________________
