Osmoregulation and Excret

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.