The Human Excretory System Flashcards
Major Organs
- adrenal gland
- kidney
- inferior vena cava
- ureter
- urinary bladder
- urethra
Kidneys
• two kidneys
Role: •removes waste - filters/cleans blood that enter through renal artery (receives 1.25L/min) • balances blood pH • maintains body’s water balance
Kidney Anatomy
• renal cortex: outer layer
• medulla: inner layer
• renal pelvis: connects the kidney to the ureter
- urine passes through the ureter, which passes to the urinary bladder
- urine exits the body through the urethra
Nephron: Regions
• each nephron is differentiated into regions
- glomerulus
- Bowman’s capsules
- proximal convoluted tubule
- loop of Henkle
- distal convoluted tubule
Glomerulus pt. 3
• blood enters here at high pressure
• filtration occurs
- fluid leaks through glomerular membrane, large molecules and blood cells stay in blood
Bowman’s Capsule
- located in the renal cortex
- a small folded structure that encircles the glomerulus
- is the site of the site steps of filtration
Proximal Convoluted Tubule pt. 1
• proximal convoluted tubule: the first site of reabsorption
- materials are transferred back into interstitial fluid
1. Water
2. Ions (K, NA, Cl)
3. Nutrients
Proximal Convoluted Tubule pt. 3
- walls of the tubules are lined with microvilli to aid reabsorption
- urea, and other unwanted materials are not reabsorbed
Descending Loop of Henle
• very permeable to water
• not very permeable to ions
• water from filtrate continues to be reabsorbed into interstitial space
- osmosis and aquaporins (due to higher concentrations of Na and Cl in interstitial space
Distal Convoluted Tubule
- additional water and salts are removed from filtrate
- secretion occurs
- waste molecule still left in the blood are passed into nephron to be removed in urine
- permeability can change depending on if ADH is present
- K
- additional active secretion of H
(helps to control blood’s pH)
Collecting Ducts
• concentrates filtrate of urea and wastes flow into collecting ducts
• many nephrons empty into each collecting duct
• further removal of water if needed
- greatly concentrates urine
Filtration Parts
- glomerulus
* Bowman’s capsule
Reabsorption Parts
- proximal convoluted tubule
- descending loop of Henle
- ascending loop of Henle
- distal convoluted tubule
- collecting ducts
Nephron
• found in the kidneys
- each kidney contains about 1 million nephrons
• the functional untis of the kidney
• specialized tubules to regulate water balance and conduct excretion
Filtration: Golerulus Part 1
- located in the renal cortex
- a group of blood capillaries that originate from the renal artery
- blood leading towards the glomerulus is by the afferent arteriole
Filtration: Glomerulus Part 2
- encased by the Bowman’s capsule
- supplies the original unfiltered blood
- filtered blood leaves the glomerulus through the efferent arteriole
Glomerulus: Filtrate (passing into capsule)
- plasma (20%)
- water
- sugars
- amino acids
- salts
- wastss (urea, uric acid)
Glomerulus: Remaining in Arteriole
- blood cells
- large proteins (can’t fit through pores)
- plasma (80%)
Filtration: Amounts
• 1400L of blood pass through the kidneys each day
• 180L enters into the Bowman’s capsule
• kidneys will filter blood plasma 65 times/day
- only 1.5L of daily filtrate is excreted as urine
Reabsorbtion: Priximal Convoluted Tubule Part 2
• reabsorption occurs through passive and active
• Ion pumps for: K+, Na+, Cl-
- Reabsorbs into the interstitial fluid
• active transport proteins
- reabsorbs aa’s, glucose, and other nutrients
Reabsorbtion: Priximal Convoluted Tubule Part 4
• filtrate becomes hypoosmotic to interstitial fluid
- causes water flow out of tubules by osmosis
- water movement also aided by aquaporins
• reabsorbed water and nutrients enter into peritubular capillaries from the interstitial space
Reabsorption: Ascending Loop of Henle
• very permeable ions
• impermeable to water
• Na+ and Cl- are reabsorbed from filtrate into interstitial fluid
- first by passive diffusion
> high concentration gradients
- secondly by active transport
> concentration gradients lessen near the top of the loop
• urea and nitrogenous wastes become concentrated in the filtrate
