Excretion and homeostasis

Campbell aqnd Reece chapter 44 (there was some homeostasis in Chapter 40 too)

Consider the work of the kidneys
Artificial kidney 10 hr 2 times per week
This is why transplant important, and there is difficulty getting a compatable donor
Cell makes wastes go to plasma
heart pumps 7000 l/day (32 55 gal drums)
1/4 (8 55 gal drums) through kidneys
Glomerulus - Bowman's capsule 180 l/day filter
1 l urine/day

Osmoregulation (for ions)
Hypertonic (concentrated), isotonic, hypotonic (dilute)
Nitrogenous waste is from catabolism of amino acids and nucleotides
Water animals - nitrogenous waste can be ammonia (toxic)
There is a tradition in undergraduate biology to emphasize comparative aspects:
("nephron" is the term for "higher" organisms)
Protonephridia in flame-bulb system of planaria TRANSPARENCY Fig. 44.18
Nephridiopores have flame bulb where cilia drive filtering through interdigitating cells
TRANSPARENCY Fig. 44.19 earthworm has nephrostome with nephridiopore in each segment in close juxtaposition with vascular system.
TRANSPARENCY Fig. 44.20 Malpighian tubule puts out uric acid and rectum recovers water and other molecules
In humans, mild accumulation of uric acid causes gout - crystals in joint cause inflammatory response which is treated by NSAIDS (non-steroidal anti-inflammatory drugs like prostaglandin inhibitors like indomethacin, ibuprophin while enzyme is inhibited by chronic treatment with allopurinol; genetically pathological uric acid accumulation which is Lesch-Nyhan syndome - children have bizarre self mutilation from HGPRTase (hypoxanthine guanine phospho ribosyl transferase) deficiency.
Marine invertebrates osmoconformers
fish 30-40% tonicity of sea water
Freshwater fish - gills leak water in, pump salt in, TRANSPARENCY Fig. 44.14 dilute urine
Salt water fish, gills lose water- pump salt out through gills, not much urine
(When we get to neurons, we will see how universal ion pumping is.)
Salmon (which move from fresh to salt to fresh water) must adapt
Cartilagenous fish keep urea in blood for equal tonicity- need to dialyse meat for preparation
Marine birds - nasal salt gland


Human TRANSPARENCY (Fig. 44.21)
kidney, ureter, bladder, urethra
Pelvis=basin; Medulla=marrow; Cortex=bark ("medulla" and "cortex" are terms used a lot, like in brain and in adrenal gland)
many blood vessels - kidney is supplied by major blood vessels
Renal artery and vein branches near eachother
each kidney has 1 million nephrons
Blood flow in glomeruli
Glomerulus - Bowman's capsule filter 180 l/day (throwing out the baby with the bath water)
blood and osmotic pressures drive
Glomerulus - capillaries a sieve
here is a picture from the histology course
another picture highlights glomerulus by dye injected into artery
large molecules dye do not pass
- small molecules dye passes through
blood proteins and cells do not pass
Small molecule dye in blood to tubules
Need for resorption TRANSPARENCY Fig. 44.22
Proximal Convvoluted tubule - bring back amino acids, glucose note active (NaCl) vs passive (water) transport
Inject dye with micropipette - show salt solution is resorbed
Na pump
6% of body's energy at rest
Countercurrant system
Ascending loop - salt resorbed but not water TRANSPARENCY (Fig. 44.23)
Ascending loop of Henle - salt outward resorption is stimulated by aldosterone
ADH (vasopressin) makes water follow back into interstitial fluid which is hypertonic from salt
alcohol and caffeine inhibit ADH, hence diuresis (excessive urination)
TRANSPARENCY Fig. 44.21 a - regulation of ADH (from hypothalamus to pituitary) and relation to thirst
hormonal control
TRANSPARENCY FIG. 44.21 b low blood pressure -> JGA (juxtaglomerular apparatus) makes renin which causes Angiotensinogen (liver) -> angiotensin II- closes arterioles
stimulates aldosterone
(remember that that adrenal cortex hormone control not mentioned earlier)
High blood pressure ->atrial natriuretic protein ->(-) aldosterone and renin

Filter, resorb (salt and water)
Sweat pores not as good -which is why gatorade tastes good to athletes
especially bad in cystic fibrosis (salty sweat) molecular genetics shows a chloride channel defect
Kidney also secretes - pump out (penicillin)

Kangaroo rat - metabolic water, hypertonic urine
Uric acid (birds, reptiles, insects)
of course, skin prevents water loss
more exoskeleton, insect preadaptation to land also trehalose hold or act like water

Homeostasis (regulation)
Body temperature set-point in hypothalamus
Sex hormones

Temp. Heat is what changes temperature
1 calorie raises temperature of 1 ml of water 1 degree C
(the "calories you "count" in a diet are kcal's)
conduction convection radiation evaporation
540 cal pant, sweat, saliva spread insensible water loss
Ectotherms (behavioral regulation like snake in sun)
Endotherms 98.6oF = 37oC
metabolic needs of small animals like hummingbirds
camels - allow to change 34-40
evaporation dog panting, sweating
reset in fever (pyrogens, antipyretics) or hibernation
Produce shiver, metabolism (thyroxine, epinephrine)
Reg. loss: Arrector pili, vasoconstr, blubber
TRANSPARENCY (Fig. 44.6) role of skin

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