Download Requirements of Animals Ch 5 Pt D - SandyBiology1-2

Common Requirements of living things ANIMALS – Chapter 5 Part D
Excretion
Elimination of Metabolic wastes
The physiological systems of animals operate within a fluid environment.
The relative concentrations of water and solutes must be maintained
within narrow limits, despite variations in the animal’s external
environment.
Metabolism also poses the problem of disposal of wastes.
The breakdown of proteins and nucleic acids is problematic because
ammonia, the primary metabolic waste from breakdown of these
molecules, is very toxic.
An organism maintains a physiological favourable environment by :
• Osmoregulation= regulating solute balance and the gain and loss of
water and
• Excretion, the removal of nitrogen-containing waste products of
metabolism.
Osmoregulators: expend energy to control their internal chemical balance
Osmoconformers: organisms whose internal environment varies with their
external environment.
Waste Removal and Water balance
• The human body and in fact all organisms are not 100%
efficient at converting all the raw materials ingested into
useful substances.
• Which means we have waste products.
–
–
–
–
–
CO2 is a waste product of cellular respiration
Water
Salts
Sugars if in extreme concentrations
Protein breakdown( metabolism) results in nitrogenenous waste
• This then is excreted as either ammonia, urea or uric acid
Nitrogenous
Wastes
Excretion of Nitrogenous wastes
Transport Epithelia
• Transport epithelia are specialized cells that regulate solute movement
• They are essential components of osmotic regulation and metabolic waste
disposal
• They are arranged in complex tubular networks
• An example is in salt glands of marine birds, which remove excess sodium
chloride from the blood
LE 44-7b
Lumen of
secretory tubule
Vein
Capillary
Artery
Secretory
tubule
NaCl
Transport
epithelium
Direction
of salt
movement
Blood
flow Secretory cell
of transport
epithelium
Central
duct
Ammonia
• Animals that excrete nitrogenous wastes as ammonia need lots
of water
• They release ammonia across the whole body surface or through
gills
Uric Acid
• Insects, land snails, and many
reptiles, including birds, mainly
excrete uric acid
• Uric acid is largely insoluble in
water and can be secreted as a
paste with little water loss
Urea
• The liver of mammals and most adult
amphibians converts ammonia to less
toxic urea
• The circulatory system carries urea to
the kidneys, where it is excreted
Organs of Excretion: The Lungs
Organs of Excretion : the Skin
+ some
nitrogenous
compounds
Organs of Excretion : The Kidneys
The kidneys are the organs that
removes nitrogenous waste from the
body.
Urine : composition
Creatinine :a break-down product
of creatine phosphate in muscle,
and is usually produced at a fairly
constant rate by the body
Mammalian Excretory Systems: deal with
•
•
•
•
•
•
•
Osmolarity
Total body water
Volume of extracellular fluid
Cell volume (osmotic pressure)
Individual ions
Acid-base balance
Metabolic waste products
• Urea
• Uric acid
• Creatinin (from muscle)
• Foreign chemicals
• Drugs, pesticides, food additives, etc.
Regulates:
Eliminates:
Vertebrate Excretory System
Overview of Human Excretion
• Kidneys, the excretory organs of
vertebrates,
–
function in both excretion and osmoregulation
• The mammalian excretory system centers
on paired kidneys, which are also the
principal site of water balance and salt
regulation
• 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
The Nephron
The Glomerulus
Glomerular filtration:
Bulk flow of protein free plasma from glomerular
capillaries to
space of Bowman’s capsule.
Bowman’s capsule: 2 walls
1) Outer wall – simple
squamous epithelium
2) Inner wall – podocytes
coat capillaries
Glomerular capillaries
Tuft of capillaries
surrounded by
Bowman’s space
Supplied by afferent
arterioles
Kidney flowchart of events
Glomerulus
Bowman’s
capsule
Proximal
tubule
Distal tubule
Loop of henle
(ascending)
Loop of henle
(descending)
Collecting
ducts
Bladder
Excreted
Posterior vena cava
Renal artery and vein
Kidney
Renal
medulla
Renal
cortex
Renal
pelvis
Aorta
Ureter
Urinary bladder
Urethra
Ureter
Excretory organs and
major associated blood
vessels
JuxtaCortical
medullary nephron
nephron
Afferent
arteriole
Glomerulus
from renal
Bowman’s capsule
artery
Proximal tubule
Peritubular capillaries
Renal
cortex
Collecting
duct
20 µm
Renal
medulla
To
renal
pelvis
Nephron
Section of kidney from a rat
Kidney structure
SEM
Efferent
arteriole from
glomerulus
Distal
tubule
Collecting
duct
Branch of
renal vein
Descending
Loop limb
of
Henle Ascending
limb
Vasa
recta
Filtrate and blood flow
Proximal tubule
NaCl Nutrients
HCO3–
K+
H2O
H+
NH3
Distal tubule
H2O
NaCl
K+
HCO3–
H+
CORTEX
Descending limb
of loop of
Henle
Filtrate
H2O
Salts (NaCl and others)
HCO3–
H+
Urea
Glucose; amino acids
Some drugs
Thick segment
of ascending
limb
NaCl
H2O
OUTER
MEDULLA
NaCl
Thin segment
of ascending
limb
Key
Collecting
duct
Urea
NaCl
Active transport
Passive transport
INNER
MEDULLA
H2O
Osmolarity of
interstitial
fluid
(mosm/L)
300
300
100
300
100
CORTEX
Active
transport
H2O
H2O
NaCl
400
NaCl
300
300
400
400
H2O
200
H2O
Passive
transport
OUTER
MEDULLA
H2O
NaCl
H2O
NaCl
H2O
INNER
MEDULLA
H2O
400
600
H2O
H2O
NaCl
900
NaCl
NaCl
H2O
600
H2O
Urea
700
H2O
Urea
900
H2O
Urea
1200
1200
600
1200
Adaptation of Vertebrate Kidneys:
Length of loop of Henle related to need for water
conservation – longer loops, greater ability to conserve
water.
Protonephridia: Flame-Bulb Systems
• A protonephridium is a network
of dead-end tubules lacking
internal openings
• The smallest branches of the
network are capped by a cellular
unit called a flame bulb
• These tubules excrete a dilute
fluid and function in
osmoregulation
Metanephridia
• Each segment of an
earthworm has a pair of
open-ended
metanephridia
• Metanephridia consist
of tubules that collect
coelomic fluid and
produce dilute urine for
excretion
Digestive tract
Rectum
Hindgut
Intestine
Midgut
(stomach)
Malpighian
tubules
Feces and urine
Salt, water, and
nitrogenous
wastes
Anus
Malpighian
tubule
Rectum
Reabsorption of H2O,
ions, and valuable
organic molecules
HEMOLYMPH