kidney

What are the three main functions of the kidneys?

Waste removal (especially NH4), osmoregulation, and blood pressure regulation.

What is the role of the loop of Henle in the nephron?

Uses countercurrent exchange to concentrate urine and conserve water.

What is ammonotelism?

Direct elimination of ammonia (NH3), usually through diffusion into water; requires lots of water.

What is uricotelism?

Nitrogenous waste is excreted as uric acid; conserves water, common in reptiles and birds.

What is ureotelism?

Conversion of ammonia into urea, which is then excreted in urine; seen in mammals and amphibians.

What is the evolutionary advantage of different nitrogen waste strategies?

They reflect habitat: aquatic animals use ammonotelism, terrestrial animals use uricotelism or ureotelism to conserve water.

What accessory organs help with salt balance in vertebrates?

Salt glands (reptiles, seabirds), rectal gland (sharks), and gills (fish).

What is the tripartite concept of kidney development?

Kidneys develop in 3 regions of the nephric ridge: pronephros (anterior), mesonephros (middle), and metanephros (posterior).

What kidney type is functional in adult amniotes?

Metanephros.

Which kidney structure is used by most adult fish and amphibians?

Opisthonephros (a fusion of mesonephros and posterior tubules).

what is the nephron?

The functional unit of the kidney that filters blood and forms urine.

What is osmoregulation?

The process of maintaining the proper balance of water and salts in the body.

What does "hyperosmotic" mean?

A solution has a greater concentration of solutes than another.

Which vertebrates are osmoconformers?

hagfishes, chondrichthyans (e.g., sharks), coelacanths, some amphibians.

What's the difference between osmoconformers and osmoregulators?

Osmoconformers match the osmolarity of their environment; osmoregulators actively control it.

Where do kidneys develop embryonically?

In the mesoderm of the dorsal body wall.

What embryonic structure gives rise to the nephron?

Nephrotome

What is the pathway of fluid in a nephron starting at the glomerulus?

Filtered at glomerulus → enters nephron tubules → wastes secreted, water reabsorbed → urine formed.

What is the pronephros and when is it functional?

the earliest kidney stage; functional in larval agnathans, some fishes, and embryos of other vertebrates.

What is the mesonephros and what is its fate?

The second kidney stage; functional in embryos and contributes to the adult kidney in fish/amphibians (opisthonephros), but replaced in amniotes.

What is the metanephros and who has it?

The final kidney stage; forms the adult kidney in all amniotes (reptiles, birds, mammals).

What duct drains the pronephros?

The pronephric duct, which becomes the archinephric duct.

What is the fate of the archinephric duct?

in males, it becomes the sperm duct (ductus deferens); in females, it may regress or be replaced by Müllerian ducts.

What duct drains the metanephros?

The metanephric duct, also called the ureter.

What kidney type do agnathans (e.g., hagfish, lamprey) have?

Simple pronephric and mesonephric kidneys; opisthonephros forms adult kidney in lamprey.

What is the kidney structure in chondrichthyans (e.g., sharks)?

Opisthonephros; archinephric duct carries sperm in males, with separate accessory urinary ducts.

How do bony fishes' kidneys develop and function?

Larval pronephros degenerates; adult kidney is opisthonephros; archinephric duct may serve both reproductive and excretory functions.

What kidney form is seen in amphibians?

Pronephros in larvae; opisthonephros in adults. Separate ducts may serve excretory and reproductive functions.

What is the adult kidney in amniotes?

Metanephros, drained by the ureter (metanephric duct).

What is the opisthonephros?

A kidney formed by mesonephric and posterior tubules; typical of adult fish and amphibians.

n amniotes, what happens to the archinephric duct?

Becomes part of the male reproductive tract (ductus deferens); no longer drains urine.

What is an indifferent gonad?

A gonad that is identical in early development before becoming testes or ovaries.

How do germ cells establish differently in males and females?

Females: cortex (outer layer); Males: medulla (inner layer).

What ducts are associated with the reproductive system?

Oviducts (females), ductus deferens (males), derived from shared embryonic ducts.

What does the archinephric duct become in amniote males?

The ductus (vas) deferens for sperm transport.

How do reproductive ducts differ across vertebrates like fishes and amphibians?

Cyclostomes lack paired ducts; others use archinephric ducts or accessory ducts.

What are intermittent organs and what is the baculum?

Intermittent organs (e.g., penis, hemipenes, claspers) transfer sperm; baculum is a penis bone in some mammals.

Which vertebrates use external fertilization?

Most aquatic species like fish and frogs; others use internal fertilization.

How do chondrichthyans and caecilians achieve internal fertilization?

Chondrichthyans use claspers; caecilians evert part of their cloaca.

What is the cloaca, where is it found, and who has it?

A shared chamber for urinary, digestive, and reproductive systems; found in most vertebrates except placental mammals.

How do marsupial and eutherian (placental) mammal reproductive tracts differ?

Marsupials have paired vaginas; eutherians have varied uterus types (e.g., simplex, bicornuate).

What reproductive duct arrangement is found in elasmobranchs?

Müllerian ducts are rudimentary; archinephric duct becomes ductus deferens.

In amphibians, what does the archinephric duct do?

May serve both testes and kidneys, or may be separated via accessory ducts

Which vertebrates typically show external fertilization?

Most aquatic vertebrates like many fish and frogs.

What is the sulcus spermaticus?

A groove used to transport sperm in birds and some reptiles.

What are the 3 chambers of the cloaca in some reptiles and birds?

Coprodeum (feces), urodeum (urine/genital ducts), proctodeum (copulation).