avian nephrology Flashcards
avain adapations are related to ability to ____
fly
- aerodynamic
- weight reduction
- flight/migration stamina
what do birds lack in their urinary tract
urinary bladder and urethra, instead they have a cloaca
where do the kidneys sit
renal fossa of synacrum in the coelom
what is the synsacrum
depression in lumbar spinal column
what are the 3 sections of the kidneys
- cranial pole
- middle pole
- caudal pole
the kidneys are in close associated with ____ and ____ plexi
lumbar and sacral
in the microscopic anatomy of the kidney, what do birds lack?
- distinct single cortex and medulla
- no renal pelvis
what are the two different types of nephrons
cortical
* akin to reptiles
* most abundant
* uric acid through glomeruli into PCT; NO LOOP OF HENLE
medullary
* akin to mammals
* have loop of henle in medullary region
* forming/concentrating urine
* more abundant in birds from deserts
ureters lined by and secrete
- lined by pseudostratified columnar epithelial cells
- mucus secretion
what does mucus secretion aid in
passing of urates
where do the ureters enter
urodeum
parts of cloaca
- coprodeum
- urodeum
- proctodeum
- vent
- bursa
coprodeum
- cranial compartment
- rectum empties; part of colon
- separates urodeum by coprourodeal fold (vital for mixing of GI and Uro contents)
urodeum
- middle compartment
- ureters and genital ducts empties here
- can retropulse urine from urodeum to coprodeum and intestines for water resorption
proctodeum
- short compartment
- empties into vent
- bursa on dorsal wall
vent
- external opening of cloaca
- variably shaped
- muscular sphincter controls for excretion and copulation
bursa
- dorsal extension of proctodeum
- unique to birds
- site of B cell maturation
- regresses with age
what are salt glands
- present in all birds
- most prominent in sea birds (drink salt water; excretion of salt)
- prominent in birds from arid climates
- countercurrent blood flow removes salt from blood
- pass from nasal passages to be sneezed out
where are the adrenal glands
- cranial to kidneys and gonads
- adjacent to aorta and caudal vena cava
adrenal glands microanatomy
cortex not well differentiated from the medulla
what hormones are secreted where in the adrenal gland
- adrenaline and norepinephrine secreted by medulla
- corticosterone (glucocorticoid and mineralocorticoid) and aldosterone from cortex
desert birds conserve water with:
- more medullar nephrons concentrate urine more efficiently
- cooling warm air through blood supply in the nares
- ~20-40% less water in excrement in birds from arid regions
dehydration prevented in migratory birds due to:
- high altitude preventing evaporative water loss
- water produced from metabolizing fat stores
- flying at night (cooler air)
what are the 3 components of avian droppings
- feces: brown/green part made of solid waste
- urates/uric acid: byproduct of protein catabolism which is white and chalky
- urine: liquid component; usually clear
90% of urine portion is reabsorbed by ___
tubules
what is the major mechanism of water control that is similar to mammals
tubular resorption
what does retroperistalsis do
move urates to rectum, mixing with feces
what is the main endproduct of protein catabolism
uric acid
- high protein diet = high blood uric acid levels
uric acid is made in the liver and excreted in kidney by:
- filtration of glomeruli
- direct tubular secretion
liver produces uric acid regardless of:
urine flow by cortical nephrons (even in dehydrated birds)
