02a2 excretion & nephron notes officialblogs.4j.lane.edu/sanderson/files/2018/04/02a2... ·...
TRANSCRIPT
Chapter 32
Osmoregulation and Excretion
afferent arteriolealdosteroneammoniaangiotensin IIanhydrobiosisantidiuretic hormone (ADH)Bowman’s capsule collecting ductcortical nephronscountercurrent multiplier systemdistal tubuleefferent arterioleexcretionfiltratefiltrationglomerulusjuxtaglomerular apparatus (JGA)juxtamedullary nephronsloop of HenleMalpighian tubulemetanephridiumnephron
osmoconformerosmolarityosmoregulationosmoregulatorperitubular capillariesprotonephridiumproximal tubulerenal arteryrenal cortexrenal medullarenal pelvisrenal veinsecretionselective reabsorptiontransport epitheliumultrafiltrationureaureterurethrauric acidurinary bladder
Overview/Background• Osmolarity vs Tonicity• both compare solute concentrations separated by a
membrane• osmolarity includes total solutes; both permeable and
impermeable• tonicity just includes permeable solutes• ex: a solution can be both hyperosmotic and isotonic
• Osmoregulation• Regulate solute concentrations• balance the gain and loss of water• controlled movement of solutes
• Excretion• Gets rid of metabolic wastes
THE INTERNAL ENVIRONMENT
WATER GAIN (milliliters)
WATER LOSS (milliliters)
by ingesting solids by ingesting liquids
by metabolism
in urine in feces
by evaporation
6.0 0.0
54.0 60.0
850 1,400
350 2,600
13.5 2.6
43.9 60.0
1,500 200 900
2,600
KANGAROO RAT HUMAN
Homeostasis - maintaining internal conditions, i.e. water concentration, temperature, pH, glucose level.
Proteins Nucleic acids
Amino acids Nitrogenous bases
–NH2 Amino groups
Most aquatic animals, including most bony fishes
Mammals, most amphibians, sharks, some bony fishes
Many reptiles (including
birds), insects, land snails
Ammonia Urea Uric acid
NH3NH2
NH2
O C
C
CN
CO
N
H H
C O
NC
HN
O
H
Nitrogenous Wastes
• Where do they come from?• products of proteins and
nucleic acids• What’s wrong with them?• toxic on their own
• Insects use:• Malphigian tubules
Nitrogenous waste type correlated with evolutionary history and habitat
Mammals: Functional Unit of the Excretory System• Nephrons and associated blood vessels• Mammals: paired kidneys• water balance and salt regulation
• Each kidney supplied by:• renal artery
• Drained by:• renal vein
Mammals: Functional Unit of the Excretory SystemBlood in the renal vein (i.e. after the kidney) will have:
▪ Less urea ▪ Less water and solutes / ions ▪ Less glucose and oxygen ▪ More carbon dioxide
Filtration of the Blood• Blood pressure forces fluid from the blood in the glomerulus
--> Bowman’s capsule• Nonselective filtration (=“ultrafiltration”)• The filtrate mirrors the concentration of various solutes in
the blood plasma
From Blood Filtrate to Urine: A Closer Look
s
sg
From Blood Filtrate to Urine: A Closer Look
• Role o/t descending limb of the Loop of Henle:• Reabsorption of
water• the longer the loop,
the more water is reabsorbed
• Countercurrent system:• maintains high salt
concentration in kidney interior
From Blood Filtrate to Urine: A Closer Look
• Role o/t ascending limb of the loop of Henle:• Salt diffuses out of the
permeable tubule into the interstitial fluid
• not permeable to water• The distal tubule• regulates K+ and NaCl
From Blood Filtrate to Urine: A Closer Look
• Role o/t collecting duct• Carries the filtrate through
the medulla to the renal pelvis
• permeable to water• not permeable to salt• permeable to urea
• helps maintain countercurrent gradient
REGULATION OF KIDNEY
FUNCTION
• Osmolarity of the urine is regulated by • nervous and hormonal control
• water and salt reabsorption in the kidneys
• Antidiuretic hormone (ADH)• Increases water reabsorption
• in the distal tubules and• collecting ducts of the
kidney