Osmoregulation and Excretion Chapter 44. Osmoregulation A balancing act The physiological systems of...
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Transcript of Osmoregulation and Excretion Chapter 44. Osmoregulation A balancing act The physiological systems of...
Osmoregulation and Excretion
Chapter 44
Osmoregulation
A balancing act The physiological systems of animals
Operate in a fluid environment The relative concentrations of water
and solutes in this environment Must be maintained within fairly narrow limits
Osmoregulation & Excretion Osmoregulation
Regulates solute concentrations and balances the gain and loss of water
Is based largely on controlled movement of solutes
Excretion Gets rid of metabolic wastes Most important is the nitrogenous wastes
Ammonia Urea Uric Acid
Nitrogenous Wastes Ammonia generally produced by aquatic
animals, very toxic, Need access to lots of water,release it across the whole body surface or through the gills
Urea ammonia converted to less toxic urea by the liver of mammals and most adult amphibians Urea is carried to the kidneys,
concentrated ,excreted with a minimal loss of water
Uric Acid insects, land snails, and many reptiles, including birds excrete uric acid as their major nitrogenous waste Is insoluble in water and can be secreted as a
paste with little water loss
Excretory Systems
Regulate solute movement between internal fluids and the external environment
Produce urine by refining a filtrate derived from body fluids
Filtration. The excretory tubule collects a filtrate from the blood.Water and solutes are forced by blood pressure across the selectively permeable membranes of a cluster of capillaries and into the excretory tubule.
Reabsorption. The transport epithelium reclaims valuable substances from the filtrate and returns them to the body fluids.
Secretion. Other substances, such as toxins and excess ions, are extracted from body fluids and added to the contents of the excretory tubule.
Excretion. The filtrate leaves the system and the body.
Capillary
Excretorytubule
Filtrate
Urine
1
2
3
4
Tubular Theme of Excretory Systems
Key Functions Filtration, pressure-filtering of body
fluids producing a filtrate Reabsorption, reclaiming valuable
solutes from the filtrate Secretion, addition of toxins and
other solutes from the body fluids to the filtrate
Excretion, the filtrate leaves the system
Survey of Excretory Systems
The systems that perform basic excretory functions Vary widely among animal groups Are generally built on a complex
network of tubules
Nucleusof cap cell
Cilia
Interstitial fluidfilters throughmembrane wherecap cell and tubulecell interdigitate(interlock)
Tubule cell
Flamebulb
Nephridioporein body wall
Tubule
Protonephridia(tubules)
Protonephridia:Flame-Bulb Systems
Is a network of dead-end tubules lacking internal openings
The tubules branch throughout the body And the smallest
branches are capped by a cellular unit called a flame bulb
These tubules excrete a dilute fluid And function in
osmoregulationFigure 44.10
Metanephridia Each segment of
an earthworm a pair of open-ended metanephridia
Consist of tubules that collect coelomic fluid and produce dilute urine for excretion
Nephrostome Metanephridia
Nephridio-pore
Collectingtubule
Bladder
Capillarynetwork
Coelom
Digestive tract
Midgut(stomach)
Malpighiantubules
RectumIntestine
Hindgut
Salt, water, and nitrogenous
wastes
Feces and urineAnus
Malpighiantubule
Rectum
Reabsorption of H2O,ions, and valuableorganic molecules
HEMOLYMPH
Malpighian Tubules Insects and other
terrestrial arthropods Remove nitrogenous
wastes from hemolymph
Function in osmoregulation
Figure 44.12
Vertebrate Kidneys Kidneys, the excretory organs of
vertebrates Function in both excretion and
osmoregulation
Mammalian Excretory System Centers on paired
kidneys Each kidney
Is supplied with blood by a renal artery and drained by a renal vein
Urine exits each kidney Through a duct called
the ureter Both ureters
Drain into a common urinary bladder
Posterior vena cava
Renal artery and vein
Aorta
Ureter
Urinary bladder
Urethra
(a) Excretory organs and major associated blood vessels
Kidney
Mammalian Kidney The mammalian kidney has two
distinct regionsAn outer renal cortex and an inner renal
medulla
(b) Kidney structure
UreterSection of kidney from a rat
Renalmedulla
Renalcortex
Renalpelvis
Figure 44.13b
Both regions are packed with microscopic excretory tubules, nephrons, and their associated blood vessels.
Each nephron consists of a single long tubule and a ball of capillaries, called the glomerulus.
The blind end of the tubule forms a cup-shaped swelling, called Bowman’s capsule, that surrounds the glomerulus
Each human kidney packs about a million nephrons.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 44.21
Filtration of the Blood
Filtration occurs as blood pressure Forces fluid from the blood in the
glomerulus into the lumen of Bowman’s capsule
The filtrate in Bowman’s capsule is a mixture that mirrors the concentration of various solutes in the blood plasma
Pathway of the Filtrate
From Bowman’s capsule, the filtrate passes through three regions of the nephron The proximal tubule, the loop of
Henle, and the distal tubule Fluid from several nephrons
Flows into a collecting duct
Processes
FiltrationSecretionReabsorption
Proximal Tubule
Secretion and reabsorption changes vol & comp of filterate
controls of pH by H+ and bicarbonate
Glucose and amino acids reabsorbed
NaCl and water reabsorbed
Loop of Henle
Descending-permeable to water, reabsorption of water
Ascending-permeable to salt, no water
Distal Tubule
Regulates K= secretion into filtrate and NaCl reabsorption from filtrate
Regulation of Kidney Function Antidiuretic hormone (ADH)-made in
hypothalamus, released from pituitary, keeps water in Alcohol inhibits ADH
Renin released by kidneys activates Angiotensin II
Angiotensin IIhormone that causes arterioles to contract blood press. Goes up causes adrenal glands to release Aldosterone
Aldosteronekidney to reabs. Na+ water retention, blood volume and pressure go up