2. Fish: shark

Amphibian: mud puppy

Bird: pigeon

Mammal: cat and rabbit

Tripartite concept of kidney organization: tubules develop in one of three regions on nephric ridge

anterior - pronephros

middle - mesonephros

posterior - metanephros

meso and meta not connected to the coelom

Pronephros play transitory role in embryonic development; embryonic pronephros regress to be replaced by mesonephros

Mesonephros become functional in embryo. If persists in adult, modified by addition of tubules from posterior nephric ridge - opistonephros, characteristic of most adult fish and amphibians.

Thus, the two types of kidney - opisthonephric and metanephric - can be distinguished by the developmental origin of the kidney.

Opisthonephric kidney is the adult kidney of anamniotes - such as the shark and mud puppy - and develops from all or most of the nephric ridge posterior to the pronephros.

Metanephric kidney is the adult kidney of amniotes - the pigeon, cat and rabbit - and develops from a small posterior part of the nephric ridge.

In fish and amphibians, nephrons within opistonephros differentiate into proximal and distal regions. In reptiles, birds and mammals, the metanephric tubules become differentiated into three regions: proximal, intermediate and distal. Only groups which produce concentrated urine (birds and mammals) have the loop of Henle, formed from a very long intermediate portion. In mammals, the intermediate section and the loop of Henle is very long, producing a very concentrated urine. Mammals urine 2 - 25x more concentrated than blood. Birds 2 - 4x more concentrated than blood, without long Loop of Henle.

Two functions of kidney:

1. excretion

2. osmoregulation

Voiding of metabolic byproducts.

Ammonia is very toxic - must be directly excreted with excrete it directly with a large quantity of dilute urine (animals living in fresh water)

Uric acid (birds, most reptiles): not soluble in water - sludge of Na+, K+, ammonium salts

Urea (mammals) are not as toxic.

Maintenance of homeostasis by careful regulation of blood solutes.

In aquatic vertebrates, gill epithelium and digestive tract are also important in osmoregulation.

Marine fishes: kidneys excrete little water, gills and sometimes specialized glands secrete excess salt.

Reptiles, mammals, birds are all water conservers: recover water before nitrogenous wastes are eliminated from body

All have internal fertilization.

Shark: claspers, siphon sac

Mud puppy: delay between insemination and fertilization. Sperm are stored in spermatheca within dorsal pocket of cloaca. Female lays eggs, stays with brood. Males have vestigial oviduct. All individuals start out female, become male under hormonal influence.

Pigeon: parental care of young

1 ovary, oviduct, uterus: sometimes can see vestigial right one

Mammals: copulatory organ - penis - has reproductive and urinary function

In female, can see separation of two systems until very close to the body opening.

Cat and rabbit very similar

Rabbit - testes only descend during mating season

- has duplex uterus, with 2 uteri, 2 cervixes, 2 os uteri

Cat - bipartite uteri, partially fused

Collecting tubules are within kidney; should have basic knowledge of kidney function.

Mesovarium not described in pigeon dissection guide; same function as that given for mud puppy

Renal pyramid consists of renal medulla and renal papilla

Os penis cannot be seen in male cat

Anal glands are optional and are not described in the dissection guide. To find them, dissect away the tissue adjacent to the anus of the male cat.

Fallopian tube is labelled as uterine tube in dissection guide.

Mesometrium is not labelled in the dissection guide. It is that portion of the broad ligament that attaches to the uterus.

For both the rabbit and the cat, make a longitudinal incision through the vagina to see the type of uterus, noting the number and position of cervical openings - os uteri - in each animal.

For both animals, remove one kidney and section it longitudinally to see the internal structures.

Responsible only for female rabbit; contrast rabbit’s ancestral duplex uterus to the bipartite uterus found in the cat.

A number of the structures listed for the rabbit cannot be found in the rabbit dissection guide; refer to the cat dissection guide for the location of these structures.

Ignore ovarian ligament.

Look at Figure 6-1 for kidney structures - Renal medulla, renal papilla together making up renal pyramid.

Page 225 - Renal sinus and hilus are described

Figure 6-3 shows adrenal glands and ureters.

Page 226 - Fundus and neck of bladder are described.

Page 228 - Mesovarium, broad ligament and round ligament are described. As in the cat, the mesometrium is that portion of the broad ligament attaching to the uterus.

Page 230 - Urogenital sinus, urogenital orifice or opening, vulva, labia majora, clitoris, os uteri