I. EXCRETION- is the process of removing metabolic wastes (metabolic means it has entered the body cells)
A. The metabolic activities of living organisms result in the production of waste materials
|
Metabolic Activity |
Wastes |
|
cellular respiration |
carbon dioxide + water |
|
dehydration synthesis |
water |
|
certain metabolic processes |
mineral salts |
|
protein metabolism |
nitrogenous |
1. nitrogenous wastes (come from the breakdown of amino acids) are produced when excess amino acids are utilized in cellular respiration.
2. nitrogenous wastes vary from the extremely toxic ammonia to less toxic urea and the nontoxic uric acid.
3. excretion maintains homeostasis by regulating the chemistry of body fluids and maintaining body temperature.
B. Adaptations- some organisms display various adaptations for excretion. Adaptations vary depending on the metabolic activities of the organism and the environment in which it lives.
1. Protista - special excretory structures are absent in many unicellular organisms. Excretion is accomplished by diffusion through cell membranes.
a. Freshwater Protozoans (animal like protists)- in the ameba and paramecium, carbon dioxide, ammonia, and mineral salts diffuse through the cell membrane directly into the watery environment.
b. use contractile vacuoles and osmosis
2. Plants
a. plants recycle the photosynthetic and respiratory gases
b. excess gases leave the plant through the stomates, lenticel, and epidermal cell of the root
c. some waste products, such as organic acids which might be toxic, are stored in vacuoles where they cause no injury to the plant.
3. Animals
a. Hydra
- excretion in the hydra is essentially similar to that of the protozoans because entire body surface is in contact with the environment.
- diffusion releases wastes
b. Earthworm
- NEPHRIDIA are the excretory organs of the earthworm; one pair in each segment.
- nephridia excrete urine out the nephriopores which leads out of the body.
- carbon dioxide is excreted by diffusion through the "moist skin".
c. Grasshopper
- carbon dioxide diffuses from the grasshopper's body fluids into tracheal tubes and is expelled through the small openings called spiracles.
- MALPIGHIAN TUBULES are the excretory organs.
- minerals and uric acid are expelled with fecal matter.(BIRDS and REPTILES do the same thing that insects do.) It is the uric acid in the fecal matter of birds that makes it necessary to wipe this substance off your car or the paint will be ruined.
- the excretion of uric acid is a water-conserving mechanism of particular advantage to an egg-laying terrestrial organism.
- of all the nitrogenous wastes, ammonia (NH3), is the most toxic, uric acid is the least toxic.
- all insects secrete uric acid.
d. EXCRETION of HUMANS- because of complexity will have its own section in notes
II. ORGANS of EXCRETION for HUMANS
A. Liver- multipurpose organ which include functions of 1) making bile, 2) detoxifies blood, 3) destroys red blood cells, 4) makes urea from excess amino acids.
1. deamination- the amine group (NH2) + an extra Hydrogen are removed from amino acids (a.a. can not be stored in the body) and converted to ammonia which is later converted into urea
2. cirrhosis- inflammation of liver cells & surrounding tissues liver cells don't function properly.
3. gout- also associated with diets containing increase levels of specific organ compounds.
4. jaundice- a condition when bile is not excreted properly and metabolic wastes are reabsorbed into the blood; this cause skin to look yellow.
B. Urinary System (organs of urinary system are: kidneys, ureters, urinary bladder, urethra)
1. Kidneys have two functions
| a. remove metabolic wastes from the blood (make urine) |
| b. control the concentration of many substances in body tissue. |
c. Structure of KIDNEY
Cortex- outer most region; FILTERING of urine is completed
Medulla- middle region; collecting ducts
Pelvis- inner region; cavity that connects kidney to ureter
NEPHRON- is the functional unit of the kidney; made of 3 structures:
1.glomerulus- cluster of capillaries which serves as the filter for blood
2. Bowman's capsule- surrounds the glomerulus
FILTRATE- are substances (water, urea, glucose, amino acids & salts) that pass through the glomerulus & enter the Bowman's capsule. Red blood cells do NOT pass through these structures but the filtrate does.
3. Loop of Henle- long tubule extending out of Bowman's capsule where reabsorption of salts & water. A capillary network surrounds the loop of Henle
REABSORPTION- into the blood occurs as the filtrate slows through the Loop of Henle
99% water reabsorption occurs by osmosis
-in all amino acids + many salts (reabsorption occurs by active transport)
Summary of Urine Function
1. Filtration - from glomerulus into the bowman's
2. Reabsorption - from the Loop of Henle in capillary network
2. Ureter carries urine to bladder
3. Urinary Bladder stores urine
4. Urethra carries urine outside the body
C. Lungs - excrete Carbon Dioxide, Water & Heat which are waste products of cell respiration
D. Sweat Glands of Skin - Water,salts, and some urea diffuse from the blood into the sweat glands and are subsequently excreted as perspiration. Respiration is only incidentally excretory, its primary function being temperature regulation. Evaporation of the sweat (98% water and 2%salts and urea) occurs when heat is absorbed from skin cells. This absorption of heat lowers body temperature. Temperature regulations an example of homeostasis. Skin has two layers the epidermis and the dermis. The epidermis is the above layer while the dermis is the inner layer.
epidermis: tightly packed epithelial cells. Tough, waterproof; protects the dermis
dermis: elastic connective tissue supports skin, binds it to muscles & bones
-has blood vessels, lymph vessels nerves, sense receptors, glands & hair follicles
-layer of fat (adipose tissue) below
-sebaceous glands which secrete oil
-sweat glands secrete Respiration (urea, water, salt)
Functions of the SKIN 1. Protection 2. Excretion 3. Sensory 4. Temperature Regulation
Biology Trivia
1. Can you name the organs involved with excretion? answer
2. Why is urine yellow? answer
3. Do you know the correct pathway for the removal of urine from the human body? answer
4. Different organisms have adaptations that allow them to remove cellular wastes effectively. These adaptations vary according to the... answer
5. Ammonia, a very toxic nitrogenous waste, is produced by aquatic animals. these animals do no die of ammonia poisoning because ammonia... answer
6. According to the organisms that we studied this chapter which organism has the most similar structure to the nephron found in the human kidney? answer
7. The principle function of perspiration is to... answer
8. What is the integumentary system in humans? answer
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