02a2 Excretion & Nephron Notesbonusblogs.4j.lane.edu/sanderson/files/2016/09/02a2... · Human...
Transcript of 02a2 Excretion & Nephron Notesbonusblogs.4j.lane.edu/sanderson/files/2016/09/02a2... · Human...
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
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
KIDNEY (one of a pair)
URETER (one of a pair)
URINARY BLADDER
URETHRA
adrenal gland
abdominal aorta
inferior vena cava
Components:
1) Kidneys filter blood in structures called nephrons. 2) Ureter 3) Bladder 4) Urethra
Urinary SystemFunctions:
• Balancing intake & output of water & salts.
• Separation of harmful & useful material. • Produce hormones to regulate blood pressure (adrenaline & aldosterone)
Waste material: urea which is a metabolic by-product of amino acids (proteins) metabolism.
Human Kidney Structure
ureter
renal pelvis
renal vein
renal artery
cortex
medulla
glomerulus (coded red)
proximal tubule (orange)
start of distal tubule (brown)
loop of Henle (yellow)
collecting duct
Nephron
Kidney Layers:
- cortex - medulla - pelvis
Nephrons - Basic functional units of kidney.
Bowman’s capsule
glomerular capillaries
COLLECTING DUCT
Nephrons Are Filtering Units
Each nephron consists of following:
- Bowman’s capsule
- Proximal tubule - Loop of Henle - Distal tubule - Collecting duct
- Capillaries: * Glomerular capillaries
* peritubular capillaries
DISTAL TUBULE
Artery Vein
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 Bowman’s capsule --> three regions of the nephron• proximal tubule -->• loop of Henle -->• distal tubule
• Then several nephrons -->• into a collecting duct
Urine Formation
Four Steps in Urine Formation:
1) Filtration (of solutes out of blood)
2) Reabsorption (of solutes into blood)
3) Secretion (of solutes out of blood)
- at glomerulus: small molecules & H2O move out of
blood into kidney tubules.
- at proximal tubules & loop of Henle: solutes & H2O
move back into blood.
- H+ and K+ are actively transported into nephron’s
lumen. 4) Excretion
Nephrons - Filtering Units
Bowman’s capsule
+ glomerular capillaries
= glomerulus
blood vessel entering
blood vessel leaving
COLLECTING DUCT
2) Reabsorption
1) Filtration
3) Secretion
Urine Formation
• Blood enters nephron thru glomerulus —› Bowman’s capsule.
• Blood cells, large solutes & proteins stay in blood. (size matters)
• Filtrate moves from Bowman’s capsule into proximal tubule.
Bowman’s capsule glomerular
capillaries
collecting duct
1) Filtration:
Urine Formation
Na+
Na+
Na+
Na+
Cl-
H2O
Interstitial fluid
KID
NEY
TU
BU
LE
Na+
Na+
•is the process of solutes getting back into blood capillaries.
BLO
OD
CA
PILL
ARY
Blo
od c
apill
ary
2) Reabsorption:
Urine Formation
2) Reabsorption:
• Na+, amino acids & glucose (filtrate) make their way back into blood by active transport.
• water follows these materials into capillaries by osmosis (99 %).
• most of reabsorption occurs in proximal tubule.
Bowman’s capsule glomerular
capillaries
collecting duct
Na+
glucose
H2O
Urine FormationBowman’s capsule
3) Secretion (by blood capillaries):
• occurs in the tubule wall, but in opposite direction of reabsorption.
• capillaries move H+ , K+ , urea and drugs into nephron’s lumen.
K+
H+ Drugs
• If hypothalamus detects a drop in extracellular fluid,
• ADH binds to receptors on distal tubule & collecting duct
• More water is reabsorbed from tubule into blood capillaries —› urine is more concentrated.
• Alcohol & caffeine = inhibitors of ADH.
H2O
H2O
H2O
H2O
ADH
Hormonal Control On Urine Formation (Antidiuretic Hormone)
• it calls for secretion of antidiuretic hormone (ADH).
•if decrease in Na+ level then adrenal gland releases:
•aldosterone
•distal tubules & collecting ducts reabsorb more Na+
Na+
Na+
Na+
Na+
Hormonal Control On Urine Formation (Aldosterone)
aldosterone
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