Exam 4 - Osmoregulation and Excretion in Humans (parts 1, 2, and 3) Flashcards
What do humans excrete in addition to excess salts and water?
toxins
What is urinary excretion?
elimination of wastes that are products of cell metabolism
What is defecation?
elimination of feces that are waste products of the digestive system
What other systems does the urinary system interact with?
cardiovascular system, endocrine system, and respiratory system
What are the two goals of the kidneys?
- removing metabolic wastes/toxins
- osmoregulation
In addition to the major functions, what else other functions do the kidneys have?
- alter pH by absorbing or secreting protons
- alter blood volume by absorbing or secreting water
What is the functional unit of the kidney?
the nephron
What are the characteristics of nephrons?
- cellular, tube-like structures
- intimately associated with capillary beds
What is the pathway of the urinary system?
- nephrons from kidneys connected to ureters
- ureters connect to bladder
- bladder connects to urethra
What percent of cardiac output goes to the kidneys?
20%
What is filtration?
initial movement of molecules from capillary into nephron
What is reabsorption?
movement of molecules in nephron back into capillary
What is secretion?
movement of a molecule from the capillary back into the nephron after filtration
Which toxic, nitrogenous wastes are removed by the kidneys?
- urea
- uric acid
- creatine
What are the two types of nephrons?
- juxtamedullary (near edge of medulla)
- cortical (in cortex)
What are the five regions of the nephron, and their functions?
- glomerular (Bowman’s) capsule: filtration
- proximal convoluted tubule: secretion and reabsorption
- nephron loop (Loop of Henle): secretion and reabsorption
- distal convoluted tubule: secretion and reabsorption
- collection duct: secretion and reabsorption
What are the vessels associated with nephron blood supply?
- afferent arteriole: blood flow to glomerulus
- glomerulus: capillary bed
- efferent arteriole: blood flow leaving glomerulus
- peritubular capillaries: associated with PCT and DCT
- vasa recta capillaries: associated with Loop of Henle
How much initial filtrate is produced each day?
180 L
How much urine is actually produced and transported to the bladder each day?
1.5 L
What is reabsorbed by the kidneys?
- 99% of the water
- nearly all sugars, amino acids, vitamins, organic nutrients
What are the characteristics of osmotic concentration?
- also known as osmolarity
- measure of solute concentration
- in kidneys, looking at Na+ and Cl- solute concentrations
What are the steps of the urinary system?
- initial filtration of blood at the filtration membrane
- reabsorption/secretion at the PCT
- salty medulla in the nephron loop
- reabsorption/secretion at the DCT
- water conservation in the collecting duct
What are the characteristics of initial filtration?
- occurs at the filtration membrane and is non-specific
- filtration occurs at “filtration slits”
- anything small enough to fit between splits enters nephron
- cells and large proteins are trapped in capillaries
With normal kidney function, which molecules are present in plasma but not in filtrate?
proteins and blood cells