Transport epithelium
One or more layers of specialized epithelial cells that carry out and regulate solute movement.
Urinary bladder
The pouch where urine is stored prior to elimination.
Countercurrent multiplier system
a countercurrent system in which energy is expended in active transport to facilitate exchange of materials and generate concentration gradients.
Juxtaglomerular apparatus
a specialized tissue in nephrons that releases the enzyme renin in response to a drop in blood pressure or volume.
Secretion
The discharge of molecules synthesized by a cell. The active transport of wastes and certain other solutes from the body fluid into the filtrate in an excretory system.
Ammonia
A small, toxic molecule produced by nitrogen fixation or as a metabolic waste product of protein and nucleic acid metabolism.
Metanephridium
An excretory organ found in many invertebrates that typically consists of tubules connecting ciliated internal openings to external openings.
Urea
A soluble nitrogenous waste produced in the liver by a metabolic cycle that combines ammonia with carbon dioxide.
Collecting duct
The location in the kidney where processed filtrate, called urine, is collected from the renal tubules.
Glomerulus
A ball of capillaries surrounded by Bowman's capsule in the nephron and serving as the site of filtration in the vertebrate kidney.
Aquaporin
A channel protein in a cellular membrane that specifically facilitate osmosis, the diffusion of free water across the membrane.
Excretion
The disposal of nitrogen-containing metabolites and other waste products.
Distal tubule
In the vertebrate kidney, the portion of a nephron that helps refine filtrate and empties it into a collecting duct.
Cortical nephron
In mammals and birds, a nephron with a loop of Henle located almost entirely in the renal cortex.
Vasa recta
The capillary system in the kidney that serves the loop of Henle.
Anhydrobiosis
A dormant state involving loss of almost all body water.
Peritubular capillary
One of the tiny blood vessels that form a network surrounding the proximal and distal tubules in the kidney.
Renal cortex
The outer portion of the vertebrate kidney.
Filtration
In excretory systems, the extraction of water and small solutes, including metabolic wastes, from the body fluid.
Ureter
A duct leading from the kidney to the urinary bladder.
Renal medulla
The inner portion of the vertebrate kidney, beneath the renal cortex.
Loop of Henle
The hairpin turn, with a descending and ascending limb, between the proximal and distal tubules of the vertebrate kidney; functions in water and salt reabsorption.
Proximal tubule
In the vertebrate kidney, the portion of a nephron immediately downstream from Bowman's capsule that conveys and helps refine filtrate.
Renin-angiotensin-aldosterone system
A hormone cascade pathway that helps regulate blood pressure and blood volume.
Kidney
In vertebrates, one of a pair of excretory organs where blood filtrate is formed and processed into urine.
Antidiuretic hormone
A peptide hormone, also called vasopressin, that promotes water retention by the kidneys. Produced in the hypothalamus and released from the posterior pituitary, and also functions in the brain.
Reabsorption
In excretory system, the recovery of solutes and water from filtrate.
Osmoregulator
An animal that controls its internal osmolarity independent of the external environment.
Osmolarity
solute concentration expressed as molarity
Osmoconformer
an animal that is isoosmotic with its environment.
Filtrate
cell-free fluid extracted from the body fluid by the excretory system.
Juxtamedullary nephron
In mammals and birds, a nephron with a loop of Henle that extends far into the renal medulla
Osmoregulation
regulation of solute concentrations and water balance by a cell or organism.
Uric acid
a product of protein and purine metabolism and the major nitrogenous waste product of insects, land snails, and many reptiles. It is relatively nontoxic and largely insoluble in water.
Nephron
The tubular excretory unit of the vertebrate kidney
Bowman's capsule
A cup-shaped receptacle in the vertebrate kidney that is the initial, expanded segment of the nephron, where filtrate enters from the blood.
Atrial Natriuretic Peptide
A peptide hormone secreted by cells of the atria of the heart in response to high blood pressure. It affects on the kidney alter ion and water movement and reduce blood pressure.
Malpighian tubule
A unique excretory organ of insects that empties into the digestive tract, removes nitrogenous wastes from the hemolymph, and functions in osmoregulation.
Renal pelvis
the funnel-shaped chamber that receives processed filtrate from the vertebrate kidney's collecting ducts and is drained by the ureter.
Protonephridium
an excretory system, such as the flame bulb system of flatworms, consisting of a network of tubules lacking internal openings.
osmosis
Water enters and leaves cells by ____________, which occurs when two solutions separated by a membrane differ in total solute concentration
Osmolarity
unit of measurement for solute concentration, the number of moles of solute per liter of solution.
Isoosmotic
two solutions with the same osmolarity.
Hyperosmotic
when two solutions differ in osmolarity, the solution with the higher concentration of solutes.
Hypoosmotic
when two solutions differ in osmolarity, the solution is more diluted.
Stenohaline
animals that cannot tolerate substantial changes in external osmolarity
Euryhaline
can survive large fluctuations in external osmolarity
Trimethylamine oxide
produced by shark tissues that protects proteins from the denaturing effect of urea
Anhydrobiosis
adaptation where some aquatic invertebrates in temporary ponds lose almost all their body water and survive in a dormant state
Dessication
refers to extreme dehydration
Phylogeny and Habitat
an animal's nitrogenous wastes reflect its _______________________
Gout
painful joint inflammation caused by deposits of uric acid crystals that are particularly susceptible to males
Filtration
key steps of excretory system function that filter body fluids. The filtrate is converted to a waste fluid by the specific transport of materials into or out of the filtrate.
Reabsorption
key steps of excretory system function that reclaim valuable solutes including glucose, certain salts, vitamins, hormones, and amino acids through active transport
Secretion
key steps of excretory system function that add nonessential solutes and wastes from the body fluids to the filtrate. It also occurs by active transport.
Excretion
key steps of excretory system function where the processed filtrate containing nitrogenous wastes is released from the body as urine
flame bulb
the smallest branches of the network are capped by a cellular unit called a _________________.
Ciliated funnel
A ___________________ surrounds the internal opening of each metanephridium.
Ureter
a duct where urine produced by each kidney exits
Urinary bladder
common sac where two ureters drain into
Urethra
tube that expel urine from the bladder to the vagina in females and through the penis in males during urination
Sphincter
muscles near the junction of the urethra and bladder regulate urination.
renal cortex
outer layer of the kidney
Renal medulla
inner layer of the kidney
Excretory tubules
lie tightly packed within the cortex and medulla that carry and process a filtrate produced from the blood entering the kidney.
renal vein
Nearly all of the fluid in the filtrate is reabsorbed into the surrounding blood vessels and exits the kidney in the _____________.
urine
The remaining fluid leaves the excretory tubules as __________
Cortical nephrons
85% of the roughly 1 million nephrons in a human kidney which reach only a short distance into the medulla.
afferent arteriole
Each nephron is supplied with blood by an _____________, an offshoot of the renal artery that branches and forms the capillaries of the glomerulus.
efferent arteriole
The capillaries converge as they leave the glomerulus, forming an _______________.
peritubular capillaries
Branches of this vessel form the __________________, which surround the proximal and distal tubules.
Proximal tubule
reabsorption of ions, water, and nutrients takes place here.
descending limb
permeable to water but not salt; water moves by osmosis into the interstitial fluid
Ascending limb
permeable to salt but not water; salt leaves by diffusion and by active transport.
elbow
The highest osmolarity (about 1,200 mOsm/L) occurs at the _________of the loop of Henle.
Distal tubule
plays a key role in regulating the K+ and NaCl concentration of body fluids.
Mammals
excrete the most hyperosmotic urine such as Australian hopping mice, North american kangaroo rats, and other desert mammals,have many juxtamedullary nephrons with loops of Henle that extend deep into the medulla.
Birds and other Reptiles
have kidneys with juxtamedullary nephrons and excrete their nitrogenous wastes as uric acid
Freshwater fish and Amphibians
produce large volumes of very dilute urine
Diabetes insipidus
from the Greek for “to pass through” and “having no flavor” cause severe dehydration and solute imbalance due to the production of copious dilute urine.
Angiotensin II
raises blood pressure and decreases blood flow to the kidneys. It triggers vasoconstriction, increasing blood pressure and decreasing blood flow to capillaries in the kidney.
atrial natriuretic peptide
opposes the RAAS, released in response to an increase in blood volume and pressure and inhibits the release of renin.