Download Excretion Summary Excretion The removal of harmful and unwanted

Excretion
Summary
Excretion
The removal of harmful and unwanted toxic waste products of metabolism is known as excretion
Osmoregulation
The process by which the water content and the ion concentration is regulated and kept constant in
the cell is known as osmoregulation
Excretory wastes
This consists of respiratory wastes, nitrogenous wastes and bile pigments

The kidneys function as a pair of filters through which about one litre of blood circulates
each minute. The entire blood in the body passes through them in 5 - 6 minutes. In a day it
filters 1800 litres of blood which is 400 times the blood volume.

Tea, coffee and alcohol are beverages that increase the formation of urine. They are
termed diuretics.

The human kidney contains more than 1.2 million nephrons

When a kidney is damaged or diseased, the other kidney is able to compensate for it. So a
person can lead a normal life with only one kidney

A normal adult excretes 1 - 1.8 litres of urine per day

An artificial kidney (dialysing machine) is used for dialysis. When the kidneys of a patient
stop functioning, life can be prolonged through dialysis.

Kidney transplants have had good success rates and have given fresh lease of life to
patients

Nitrogenous wastes consists of ammonia, urea, uric acid and amino acids

Excretion and osmoregulation takes place in the amoeba through the contractile vacuole

Excretion and osmoregulation takes place in the earthworm through the nephridia and skin

Excretion and osmoregulation in man takes place through the kidneys. Excretion also
takes place through the skin, lungs and liver.

The urinary system in man consists of a pair of kidneys, a pair of ureters, a urinary bladder
and a urethra

Each kidney has three distinct regions, cortex, medulla and pelvis

The nephron is the structural and functional unit of the kidney

Each nephron has a network of capillaries called glomerulus which fits into a cup called
the Bowman's capsule and a long tubule consisting of proximal convoluted tubule, Henle's loop,
distal convoluted tubule and connecting tubule.
Question (1): How are wastes formed in the body?
Answer: Wastes are formed in the body as by-products of the metabolic activities in the body.
Question (2): Define excretion.
Answer: The removal of harmful and unwanted toxic waste products of metabolism from the body is known as
excretion.
Question (3): Define osmoregulation.
Answer: The process by which the water content and the ion concentration is regulated and kept constant in the
cells is known as osmoregulation.
Question (4): Name an organ that performs both excretion and osmoregulation.
Answer: Kidneys perform both excretion and osmoregulation.
Question (5): What is secretion? Give two examples.
Answer: Secretion is the production of useful chemical substances like hormones, enzymes or other molecules
by glands, endocrine glands or specialized cells. For example: The liver secretes bile, the islets of langerhans
secrete insulin, epithelial lining of the large intestine secrete mucus.
Question (6): What is egestion?
Answer: The expelling of undigested wastes from the body in the form of excreta is known as egestion.
Question (7): What are the three main groups of excretory wastes found in animals?
Answer: 1) Respiratory wastes
2) Nitrogenous wastes
3) Bile pigments
Question (8): Name the two respiratory waste products formed due to catabolism of food.
Answer: The two respiratory waste products formed due to catabolism of food are carbon dioxide and water.
Question (9): Mention four nitrogenous waste products produced by animals.
Answer: Four nitrogenous waste products produced by animals are:
1) urea
2) uric acid
3) ammonia
4) amino acids
Question (10): In higher animals, what does ammonia react with to produce urea?
Answer: Ammonia reacts with carbon dioxide in the liver to form a less toxic substance, urea which is
periodically flushed out of the system.
Question (11): Name two groups of animals in which amino acids are excreted out without undergoing any
change.
Answer: Amino acids are excreted out without undergoing any change in:
1) Molluscs
2) Echinoderms
Question (12): Name two groups of animals which excrete uric acid in the form of a white paste or pellet.
Answer: Animals which excrete uric acid in the form of a white paste or pellet are:
1) Birds
2) Reptiles
Question (13): Name the organ that converts ammonia into urea in higher animals.
Answer: Ammonia is converted into urea in the liver.
Question (14): How are bile pigments formed?
Answer: Bile pigments are formed by the breaking down of haemoglobin present in the red blood cells.
Question (15): Name the organ that destroys worn out red blood cells.
Answer: Worn out red blood cells are destroyed in the liver.
Question (16): Name two bile pigments.
Answer: The two bile pigments are:
1) Bilirubin
2) Biliverdin
Question (17): Name the organelle in amoeba that performs excretion and osmoregulation.
Answer: Contractile vacuole in amoeba performs excretion and osmoregulation.
Question (18): What would happen to amoeba if osmoregulation did not take place?
Answer: If osmoregulation did not take place the organism would get flooded with water and burst.
Question (19): How does the cell membrane perform excretion in amoeba?
Answer: The cell membrane of Amoeba being semi permeable the carbon dioxide diffuses out of the cell
membrane into the surrounding water. The cell membrane forms the general body surface of amoeba.
Question (20): Name two waste products excreted by the skin.
Answer: Two waste products excreted by the skin are:
1) sweat
2) sebum
Question (21): Mention one difference between sebum and sweat.
Answer: Sebum is secreted by the sebaceous gland. Sweat is secreted by the sweat gland.
Question (22): Where are sebaceous glands found?
Answer: Sebaceous glands are found attached to the hair follicle in the skin of mammals.
Question (23): Mention three excretory substances found in sebum.
Answer: Three excretory substances found in sebum are:
1) Wax
2) Fatty acid
3) Sterols
Question (24): Name the principal excretory organ in man. What does it excrete?
Answer: The main excretory organ in man are the kidneys. They excrete urine.
Question (25): Why is the right kidney lower than the left?
Answer: The right kidney is lower than the left because of the presence of liver, in the abdominal cavity.
Question (26): Name three beverages that are diuretics.
Answer: Three beverages that are diuretics are:
1) coffee
2) tea
3) alcohol
Question (27): Differentiate between afferent arteriole and efferent arteriole.
Answer:
Afferent Arteriole
Efferent Arteriole
Formed by the joining of the
Formed by the branching of the renal artery
glomerular capillaries
Its lumen is twice as thick as the efferent
Its lumen is twice as narrow as that of
arteriole
the afferent arteriole
Carries oxygenated blood away from
Brings oxygenated blood into the kidney
the Bowman's capsule
Brings blood which contains large amounts of It carries away blood that is relatively
water and nitrogenous metabolic wastes
thicker and free of toxic wastes
Divides to form the glomerulus which is a knot Divides to form the vasa rectae
inside the Bowman's capsule
enveloping the renal tubule
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Question (1): Loop of Henle is concerned with:
1. excretory system
2. reproductive system
3. nervous system
4. muscular system
Ans: 1
Question (2): Urea is transported by
1. plasma
2. blood
3. RBC
4. WBC
Ans: 1
Question (3): The kidneys resemble the contractile vacuoles of amoeba in
1. expelling out excess of water
2. expelling out glucose
3. expelling out urea and uric acid
4. expelling out salts
Ans: 1
Question (4): Glucose is reabsorbed in the kidney mainly by
1. Bowman's capsule
2. Loop of Henle
3. Proximal Convoluted Tubule
4. Distal Convoluted Tubule
Ans: 3
Question (5): Excess amino acids in the body are broken down to form urea in
1. kidney
2. liver
3. spleen
4. pancreas
Ans: 2
Question (6): Difference between glomerular filtrate and blood plasma is of
1. proteins in plasma
2. potassium
3. first is white and second is yellow
4. proteins in glomerular filtrate
Ans: 1
Question (7): In the kidneys of mammals, Loop of Henle can be found in
1. medulla
2. cortex
3. pelvis
4. pyramid
Ans: 1
Question (8): In the kidney the correct sequence of formation of urine involves the following processes:
1. glomerular filtration, reabsorption, tubular secretion
2. reabsorption, filtration, secretion
3. filtration, secretion, reabsorption
4. reabsorption, secretion, filtration
Ans: 1
Question (9): A severe fall in blood pressure disturbs the function of kidneys and reduces
1. renal filtration
2. glomerular filtration
3. reabsorption
4. secretion of nitrogenous wastes
Ans: 2
Question (10): Excretion of bile pigments in urine indicates
1. anaemia
2. diabetes
3. gout
4. jaundice
Ans: 4
Question (11): Workers in deep mines usually suffer from dehydration because
1. water is lost due to evaporation
2. water is lost due to defecation
3. water is lost in the form of sweat
4. water is lost along with salts in the form of sweat
Ans: 4
Question (12): The concentration of urea is highest in
1. renal vein
2. hepatic portal vein
3. dorsal aorta
4. hepatic vein
Ans: 4
Question (13): The concentration of urea is least in
1. renal artery
2. renal vein
3. post canal
4. dorsal aorta
Ans: 2
Question (14): The function of the mammalian kidney is to excrete
1. extra salts, urea and excess water
2. extra urea, excess water and excess amino acids
3. extra urea, extra carbohydrates and extra water
4. extra urea, extra salts and extra sugar
Ans: 1
Question (15): The plasma is similar in its composition with the filtrate produced in glomerulus except for the
presence of
1. glucose
2. chlorides
3. proteins
4. amino acids
Ans: 3
Question (16): If a man takes in large amount of proteins he is likely to secrete more amount of
1. urea
2. uric acid
3. sugar
4. carbon dioxide
Ans: 1
Question (17): What will happen if one kidney of a person is removed
1. he will survive and remain normal
2. he will die
3. urea will go on accumulating in the blood
4. urination will stop
Ans: 1
Question (18): The glomerular filtrate contains
1. blood minus cells
2. blood minus cells and minus proteins
3. blood minus proteins
4. plasma minus cells minus proteins
Ans: 2
Question (19): In the distal convoluted tubule of the nephrons
1. Sodium reabsorption requires energy
2. Secretion of potassium does not require energy
3. Water reabsorption requires energy
4. Ammonia is secreted
Ans: 1
Question (20): The mechanism of uric acid secretion in the nephron is
1. diffusion
2. excretion
3. ultrafiltration
4. osmosis
Ans: 3
Question (21): Human kidney has
1. Ciliated nephrons
2. No loop of Henle
3. Meronephric duct
4. Glomeruli concentrated in cortex
Ans: 4
Question (22): Uriniferous tubules are found in
1. Kidneys
2. Testes
3. Ovary
4. Stomach
Ans: 1
Question (23): Reabsorption of chloride ions from the glomerular filtrate in the kidney tubule is carried out by
1. Osmosis
2. Diffusion
3. Active transport
4. Brownian movement
Ans: 2
Question (24): Bowman's capsule and glomerulus form
1. cortex
2. pyramid
3. malphigian body
4. medulla
Ans: 3