Download Excretory System

Excretory System
Topic 13
I. Excretion
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A. excretion – removal of metabolic wastes
produced in the body
B. carbon dioxide – aerobic respiration
C. water – aerobic respiration, dehydration
synthesis
D. nitrogenous wastes – (urea, ammonia, uric
acid) – deamination of amino acids
E. mineral salts – all metabolic processes
II. Excretion in organisms
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A. protozoa and cnidarians – simple diffusion
through the cell membrane – water –
contractile vacuole – ameba, paramecium,
and hydra
Ameba
Paramecium
Hydra
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B. annelida – earthworm – two pairs of
nephridia tubules – excrete water, mineral
salts and nitrogenous wastes in the form of
urea
Earthworm’s Nephridia
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C. arthropods – grasshopper – nitrogenous
wastes in the form of solid uric acid crystals –
use Malphigian tubules – crystals are
transported to the intestine and are expelled
along with solid wastes of digestion
Grasshopper – Malpighian
tubules
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D. fish – osmoregulation – regulate the
volume and salt content of their internal fluids
Osmoregulation in fish
III. Human Excretory System parts
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A. kidneys – form urine to remove nitrogenous
wastes in the form of urea (urea is formed in the
liver) as well as regulating the volume and salt
content of the extracellular fluids
B. ureter – tube that leads from the kidneys to
the urinary bladder
C. urinary bladder – urine is stored here until
urination occurs
D. urethra – urine leaves body through this tube
Human Urinary System
IV. Human excretory system –
functional unit
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A. urea – amino acids get broken down from
proteins and are used for energy in the Krebs
cycle – the nitrogen is removed and released
as ammonia which is toxic – the liver
converts the ammonia to urea which is less
toxic – the kidneys remove the urea from the
blood stream
Nephron
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B. nephron – functional unit of the kidney – first
filters blood to form a filtrate fluid and then
selectively modifies the filtrate to produce urine
(essay – steps 1- 6)
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1. glomerulus – a ball-shaped cluster of capillaries –
where the blood enters the nephron – pressure of blood
in the glomerulus squeezes the liquid portion of the
blood out of the glomerulus through a sievelike filtering
structure – blood cells are too large to pass through the
sieve and most proteins are retained in blood by their
size and charged nature – other small molecules such
as salts, amino acids, glucose, water, and urea pass
easily into the filtrate
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2. Bowman’s capsule – the filtrate that leaves the
blood enters a cup-shaped structure that
surrounds the glomerulus – this is the starting of
the tubelike nephron
3. proximal convoluted tubule – the urine is
modified here – active transport pumps glucose,
amino acids, sodium, and proteins back out of the
filtrate – water is also reabsorbed by the process
of osmosis which concentrates the urine and
reduces the volume of the filtrate
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4. loop of Henle – the filtrate passes to the loop of
Henle – more water is absorbed by the process of
osmosis – sodium leaves the filtrate – the volume
of the filtrate is reduced
5. distal tubule – aldosterone – steroid hormone –
increase the absorption of sodium from the
urinary filtrate
6. collecting duct – hormone ADH (antidiuretic
hormone – also called vasopressin) regulates the
permeability of the collecting duct walls – may
absorb more water – urine travels to ureter
V. Thermoregulation and the
skin
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A. two types of organisms
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1. ectothermic – cold blooded – most of their heat
energy escapes to the environment – body
temperature is similar to the environment – also
called poikilotherms
2. homeothermic – warm blooded – maintain their
body temperature
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B. skin – protects the body from microbial
invasion – melanocytes make melanin which
protects the body from uv rays – receptor of
stimuli – excretory organ – thermoregulatory
organ
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1. sweat glands – secrete a mixture of water,
dissolved salts, and urea – both excretory and
thermoregulatory function
Sweat glands
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2. subcutaneous fat – found in the hypodermis of
the skin – insulates the body – hair traps and
retains warm air at the skin’s surface –
epinephrine can increase the metabolic rate which
increases heat production – muscles can also
generate heat by contraction (shivering)
Subcutaneous fat
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C. other methods of regulation
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1. panting – evaporates water from respiratory
passages
2. hibernation – animal remains dormant over a
period of weeks or months with body temperature
maintained below normal
VI. Malfunctions
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A. gall stones – collections of salts,
cholesterol, or calcium that build up in the gall
bladder
B. gout – build up of uric acid in the joints
C. Kidney stones – collections of salts,
cholesterol, or calcium that build up in the
kidneys