Chapter 15 - Urinary System Flashcards
Define excretion:
The removal of metabolic wastes produced in the body
What produces CO2 and H2O?
Aerobic respiration
What produces nitrogenous wastes (i.e. urea and ammonia)?
Deamination of amino acids in the liver
Define elimination:
The removal of indigestible material
- Ex. Dietary fiber
What are the principal organs of excretion?
1) Lungs
2) Liver
3) Skin
4) Kidneys
How does excretion occur in the lungs?
CO2 and H2O vapour diffuse through blood and are exhaled
How does excretion occur from the skin?
Sweat glands in the skin excrete water and dissolved salts
How does excretion occur in the liver and kidney?
Processes nitrogenous wastes, hemoglobin, and other chemicals for excretion
- Urea is produced by deamination of amino acids in the liver and diffuses into the blood for ultimate excretion in the kidneys
- Kidneys function to maintain osmolarity of blood, excrete waste product/toxic chemicals, and conserve glucose, salt, and water
What role do bile salts have during excretion?
Bile salts are excreted as bile and pass with the feces
What is the function of the kidneys?
Regulate concentration of salt and water in the blood through formation and excretion of urine
What is the kidney composed of?
~1 million units called nephrons
What 3 regions is the kidney divided into?
1) Outer cortex
2) Medulla
3) Renal pelvis
What does a nephron consist of?
1) Bowman’s Capsule: Embraces capillary bed (glomerulus) that leads to a long, coiled tubule
2) Proximal Convoluted Tubule
3) Loop of Henle
4) Distal Convoluted Tubule
5) Collecting Duct
What part of the nephron runs through the medulla?
Loop of Henle & Collecting Duct
What part of the nephron runs through the cortex?
Bowman’s Capsule & Convoluted Tubules
Describe the flow of urine:
- Urine in collecting tubules flows into the pelvis of kidney, a funnel-like region the opens into the ureter
- Ureters from kidney empty into urinary bladder where urine collects until expelled by the urethra
What is most of the nephron surrounded by?
Complex peritubular capillary network that facilitates reabsorption of amino acids, glucose, salts, and water
What are the 3 processes of urine formation?
1) Filration
- BP forces 20% of blood plasma entering glomerulus through capillary walls into the Bowman’s Capsule (filtrate)
- Filtrate is isotonic with blood plasma
- Particles too large remain in the circulatory system
- Filtration is passive driven by hydrostatic pressure of blood; High BP results in increased hydrostatic pressure which exerts pressure on kidney tissue, and may lead to kidney damage
2) Secretion
- Wastes are secreted from IF into filtrate via passive and active transport
3) Reabsorption
- Essential substances and water are reabsorbed from filtrate and returned to blood
- Occurs mainly in proximal convoluted tubule (active)
- Movement of these molecules is accompanied by passive movement of water because water follows solute
- (Results in concentrated urine (hypertonic to blood)
How does the nephron function?
Through selective permeability of the walls and maintenance of an osmolarity gradient
- Ability to regulate balance of salt and water in the body
What is the primary function of the nephron?
Clean blood plasma of unwanted substances as the filtrate passes through the kidney
What is the primary site of nutrient reabsorption?
Proximal convoluted tubule
What is the primary site for regulation of water, sodium, and potassium?
Loop of Henle & Collecting Duct
What is the major site for secretion of substances into the filtrate?
Distal convoluted tubule
Describe the descending loop of Henle:
- Permeable to water but not to ions or urea
