Rajasthan Board RBSE Class 12 Biology Chapter 25 Man-Excretory System
RBSE Class 12 Biology Chapter 25 Multiple Choice Questions
Question 1.
The main excretory substance in human is:
(a) Uric acid
(b) Ammonia
(c) Urea
(d) Amino acid
Answer:
(c) Urea
Question 2.
The main excretory organ of human is:
(a) Lungs
(b) Kidney
(c) Skin
(d) Liver
Answer:
(b) Kidney
Question 3.
Henle’s loop contains:
(a) Urine
(b) Urea
(c) Blood
(d) Glomerular filtrate
Answer:
(d) Glomerular filtrate
Question 4.
A renal column of Bertini is related to:
(a) Kidney
(b) Urinary bladder
(c) Liver
(d) Testis
Answer:
(a) Kidney
Question 5.
Human kidneys are:
(a) Pronephric
(b) Metanephric
(c) Mesonephric
(d) All of the above
Answer:
(b) Metanephric
Question 6.
Ultrafiltration occurs in:
(a) Glomerulus
(b) Bowman’s capsule
(c) Urinary bladder
(d) Blood vessels
Answer:
(a) Glomerulus
Question 7.
The glomerular filtrate is:
(a) Water, ammonia and blood corpuscles
(b) Blood without blood corpuscles and plasma protein
(c) Blood without blood corpuscles
(d) Urine
Answer:
(b) Blood without blood corpuscles and plasma protein
Question 8.
The blood vessel which brings blood into the glomerulus:
(a) Efferent arteriole
(b) Renal artery
(c) Afferent arteriole
(d) Renal vein
Answer:
(c) Afferent arteriole
RBSE Class 12 Biology Chapter 25 Very Short Answer Type Questions
Question 1.
What is Excretion?
Answer:
Removal of metabolic waste products from the body is called excretion.
Question 2.
An animal which excretes ammonia is called?
Answer:
Ammonotelic.
Question 3.
Animals which excrete uric acid are called?
Answer:
Uricotelic.
Question 4.
What is Ultrafiltration?
Answer:
The process of filtration of blood from the glomerulus into the Bowman’s capsule because of increased glomerular blood pressure is called as Ultrafiltration.
Question 5.
Write the name of the excretory unit in the kidney.
Answer:
Nephron or uriniferous tubule.
Question 6.
Name the blood vessel coming out of the glomerulus.
Answer:
Efferent arteriole.
Question 7.
What is the term used for pain at the time of micturition?
Answer:
Dysuria.
Question 8.
Where the glomerulus is found? What is its role?
Answer:
The glomerulus is enclosed in Bowman’s capsule. It performs Ultrafiltration.
Question 9.
What is the malpighian body?
Answer:
The anterior part of the nephron is called a Malpighian body. It includes glomerulus and Bowman’s capsule.
Question 10.
Where the Henle’s loop is found?
Answer:
It is a U-shaped part of Nephron.
Question 11.
What are Renal columns of Bertin?
Answer:
The pushing of the cortex part of the kidney into the medulla is termed as a renal column of Bertin.
Question 12.
What is the main role of kidneys in the body?
Answer:
Removal of nitrogenous waste product (urea) from the body.
Question 13.
What is haemodialysis?
Answer:
Removal urea and other waste products from the blood using artificial kidney (Dialyser) are termed as haemodialysis.
Question 14.
Presence of Urea in the blood is called?
Answer:
Urania.
Question 15.
What is glycosuria?
Answer:
Presence of glucose in the urine is called glycosuria.
RBSE Class 12 Biology Chapter 25 Short Answer Type Questions
Question 1.
Describe the excretory organ in the human body other than kidneys.
Answer:
Other Excretory Organs in Man:
- Skin: Sweat glands are found in the human skin, which secretes out sweat containing water and some nitrogenous excretory substances.
- Lungs: Cellular respiration release CO2 as excretory substance, which is eliminated outside by respiratory process in the lungs.
- Liver: Liver cells convert nitrogenous part of amino acids into ammonia and then ammonia into urea. The urea is released into the blood. The liver also forms bile pigments which are excreted along with the bile juice into the intestine.
Question 2.
What is Gout disease?
Answer:
Gout:
- It is a hereditary disease in which blood uric acid is increased. It gets deposited in the synovial joints and in Kidney tissues. This disease may cause due to dehydration, fasting and diuresis.
Question 3.
Explain Bright’s disease.
Answer:
Bright’s disease or Nephritis:
- This disease is caused due to infection of Streptococci bacteria in the glomeruli. As a result, they swell and their membrane becomes more permeable to RBC’s and proteins which filtered out and appears in the filtrate. If nephritis is not cured than fluid deposition occurs and the condition of swollen legs happens, which is called Edema or Dropsy.
Question 4.
What is the role of ultrafiltration and selective reabsorption in urine formation?
Answer:
Ultrafiltration:
- It is a passive process which takes place from the glomerulus into the Bowman’s Capsule The glomerular epithelium has various micropores (diameter = 0.1μ) which increase the rate of filtration.
- The ultrafiltration takes place due to increased blood pressure in the glomerulus which is increased due to the difference in the diameters of afferent & efferent arterioles.
- There is ultrafiltration of all the components of the blood except the blood corpuscles, plasma proteins macromolecular foreign substance. The ultrafiltration forms glomerular filtrate in the Bowman’s capsule.
- The glomerular filtrate is plasma without plasma protein.
Glomerular filtrate ⇒ Blood – Blood Cells + Plasma Proteins
Glomerular filtrate ⇒ Plasma – Proteins - The hydrostatic pressure in the glomerulus (GHP) is 65 to 75 mm of Hg. Out of it, the blood colloidal osmotic pressure (BCOP) due to plasma proteins is 30 mm of Hg.
- On the contrary, the capsular hydrostatic pressure (CHP) is 20 mm of Hg. Hence, the net Effective glomerular filtration pressure (EFP) is 15 to 25 mm of Hg which is responsible for ultrafiltration.
- In human beings, the glomerular filtration rate (GFR) is 125 ml per minute i.e. both the kidneys form 125 ml of filtrate per minute.
- Hence, 180 litres of filtrate is formed per day. Out of it, only 1.5 litres of urine is produced per day which is 0.8% of the total filtrate.
Reabsorption:
- In the renal tubules, 99.2% of the glomerular filtrate is reabsorbed into the blood.
- The reabsorption takes place by active transport and most of the reabsorption takes place in the PCT. However, water is absorbed by passive transport.
- The reabsorption of the substance is according to the renal threshold value. The maximum capacity of both the kidneys to absorb a particular substance is called a renal threshold of the substance. The renal threshold value of the substances is according to their requirement in the body.
- The substances are of 3 types on the basis of their renal threshold value –
- High threshold substances:
- Such substances are absorbed almost all.
- Example: Sugar, amino acids, vitamins etc.
- Low threshold substances:
- They are absorbed in low concentration.
- Example: Urea, creatine, creatinine, phosphate etc.
- A threshold substances:
- They are not absorbed.
- Example: Uric acid etc.
- High threshold substances:
- If any substance exceeds its renal threshold value, it will appear in the urine.
- The renal threshold value of glucose is 350 mg per minute which is also called as TmG.
- The reabsorption of the substances is under the control of hormones which are as follows:
- Glucocorticoids:
- They are secreted by adrenal cortex & they control reabsorption of sugars, amino acids & vitamins in the PCT.
- Mineralocorticoids:
- They are secreted by the adrenal cortex and they control reabsorption of mineral ions in the PCT
- Calcitonin & Parathormone:
- They control the absorption of Cat+ in the DCT.
- Vasopressin or ADH:
- It is a hormone of the Pituitary gland which controls the absorption of water in the DCT. Most of the water (about 80%) is absorbed in the PCT along with the substances.
- It is called as obligatory water reabsorption. Remaining water (about 20°.) is absorbed in the DCT under the control of ADH according to the body requirement. It is called facultative water reabsorption.
- Glucocorticoids:
- Excess release of the ADH result in a decreased volume of the urine
Question 5.
What do you mean by kidney transplantation? Explain in brief.
Answer:
Kidney Transplantation:
In a human being when kidneys stop functioning and are not curable than a kidney of other healthy person is to be transplanted. The Kidney is obtained from a donor who may be decreased or live. Kidney donor should be the nearest relative whose blood and tissue structures are to be similar.
If unmatched kidney transplantation is done than the immune system of patient will not accept the transplanted kidney and it will not work properly so the patient may die. Although special medicines are given to a patient to inactivate the immune system and the possibility to accept the kidney of the donor is increased.
RBSE Class 12 Biology Chapter 25 Essay Type Questions
Question 1.
Explain the excretory system in man by giving a suitable diagram.
Answer:
Excretory System of Man:
- Kidneys are the main excretory organs in man. In addition, the excretory system also includes ureters, urinary bladder and urethra.
Kidney:
- In man, the kidneys are metanephric which originate from mesoderm.
- There is a pair of kidneys which are attached with the help of peritoneum in the dorsal side of the middle part of the coelom. The peritoneum is found only on the ventral side. Such kidneys are called retroperitoneal.
- The kidneys are dark red in colour. They are unequally situated. In human beings, the right kidney is somewhat posteriorly situated.
- The weight of each kidney is 120 – 170 gm.
- The kidney is bean-shaped i.e., concavo-convex. The concave inner surface is called as hilus which gives out a ureter.
- From this hilus surface, the renal artery enters into the kidney, the renal vein comes out and the renal nerves enter into the kidney.
- The dimensional of a human kidney is 4″ × 2.5″ × 1″ inch.
- An adrenal gland is attached to the anterior end of each kidney like a cap.
Ureters:
- The inner hilum (hilus) surface of the kidney gives out a ureter.
- The anterior end of the ureter is funnel-shaped which is called as the pelvis.
- Both the ureters open separately into the urinary bladder.
- The wall of the ureter is thick and muscular. Its peristalsis movement helps to move the urine.
Urinary Bladder:
- The urinary bladder is baglike which is made up of smooth & involuntary muscles. The lumen of the urinary bladder is lined by transitional epithelium which has great power of stretching. Hence, the urinary bladder can store more urine.
- The urinary bladder leads into male urethra & its opening is regulated by a sphincter. In human beings, the sphincter is made up of voluntary muscles. The sphincter is relaxed only at the time of micturition.
- The act of passing urine is called micturition which is a partly voluntary process in human beings.
- In a male, the urethra leads outside through the penis and in female through the vulva.
- In woman urethra is absent. Hence, the urinary bladder opens outside directly through the urinary orifice. In man, the urethra can be divided into three parts –
- Prostatic or Urethral Part: Anterior most part having length 2.5 cm. It receives prostate gland, urinary bladder and both the vas deferens.
- Membranous part: It is the middle part which receives the Cowper’s glands.
- Penile part: It is situated inside the corpus sporangium of the penis. Its length is about 15 cm.
Question 2.
Describe the functional structure of Uriniferous tubule.
Answer:
Structure of Nephron:
- It is a unit of excretion in which urine is formed independently.
- Its an anteriormost part is called a Malpighian body which includes a cup-like Bowmann’s capsule & a glomerulus.
- The glomerulus is a bunch of blood capillaries. It receives the blood through an afferent arteriole and the blood comes out through the efferent arteriole. The diameter of the afferent is comparatively more.
- The Bowman’s capsule opens into a proximal convoluted tubule (PCT) through a short & straight neck. The anterior part of the PCT is more coiled whereas its posterior part is almost straight. The PCT opens into a Henle’s loop.
- The Henle’s loop is a U-shaped structure which has a distinct descending limb & an ascending limb. The ascending limb opens into the DCT.
- The descending convoluted tubule (DCT) is a coiled duct.
- Many DCT unites to form a collecting duct. The collecting ducts of one pyramid unite to form a duct of Bellini. The ducts of Bellini lead into the pelvis part.
- The Malpighian body and a part of PCT & DCT are situated in the cortex. Most of the part of PCT & DCT, Henle’s loop and collecting ducts are found in the medulla.
- The efferent arteriole forms a peri-tubular capillary network around the PCT, DCT & Henle’s loop which is called as Vasa recta.
- The capillaries of Vasa recta join to form venules which finally open into the renal vein.
Histology of Nephron:
- The wall of the Bowman’s capsule is made up of simple squamous epithelium.
- Its inner wall has special cells, called podocytes.
- The podocytes have finger-like processes which bind the glomerular-blood capillaries.
- The neck of the nephron & collecting duct is made up the ciliated epithelium.
- PCT is made up of simple cuboidal epithelium. It has brush-border of microvilli.
- The Henle’s loop is made up of simple squamous epithelium.
- DCT is made up of simple cuboidal epithelium. It is without microvilli.
Question 3.
Explain other excretory organs in Man.
Answer:
Other Excretory Organs in Man:
- Skin: Sweat glands are found in the human skin, which secretes out sweat containing water and some nitrogenous excretory substances.
- Lungs: Cellular respiration release CO2 as excretory substance, which is eliminated outside by respiratory process in the lungs.
- Liver: Liver cells convert nitrogenous part of amino acids into ammonia and then ammonia into urea. The urea is released into the blood. The liver also forms bile pigments which are excreted along with the bile juice into the intestine.
Question 4.
Describe various diseases associated with the excretory system.
Answer:
Disorders related to Excretion:
Irregularities in excretion may cause various diseases in human. Some of the diseases are as follows:
- Uremia: When the amount of urea in the blood becomes more than 10 – 30 mg/100 ml, the condition is called Uremia. Excess amount of urea in blood is harmful and may be fatal.
- Gout: It is a hereditary disease in which blood uric acid is increased. It gets deposited in the synovial joints and in Kidney tissues. This disease may cause due to dehydration, fasting and diuresis.
- Kidney stones: Normally crystals of substance like calcium oxalate, phosphate, uric acid etc get deposited in the renal pelvis as renal stones. They cause pain & difficulty in micturition.
- Bright’s disease or Nephritis: This disease is caused due to infection of Streptococci bacteria in the glomeruli. As a result, they swell and their membrane becomes more permeable to RBC’s and proteins which filtered out and appears in the filtrate. If nephritis is not cured than fluid deposition occurs and the condition of swollen legs happens, which is called Edema or Dropsy.
- Glycosuria: Presence or excretion of glucose in the urines is called Glycosuria. It is caused due to deficiency of insulin hormone. This disease is called diabetes mellitus.
- Dysuria: Pain at the time of micturition is called dysuria.
- Polyurea: The increased amount of urine due to less absorption of water is called as polyurea.
- Cystitis: The swelling of the urinary bladder by the infection of bacteria, chemical or mechanical damage is called cystitis.
- Diabetes Insipidus: Due to hyposecretion of antidiuretic hormone (ADH), the water absorption does not occur in the distal convoluted tubules and collecting tubule results into an increase in the volume of Urine. There is frequent and excess micturition.
- Oliguria: Formation of less quantity of urine as compared to normal.
- Proteinuria: Presence of more protein in urine is called proteinuria.
- Albuminuria: Presence of more amount of albumin protein in the Urine.
- Ketonurea: Increase the number of ketone bodies in urine such as acetone acetic acid.
- Haematonurea: Elimination of red blood corpuscles (RBC’s) along with urine is called haematuria.
- Haemoglobuinurea: Presence of haemoglobin in urine is called haemoglobinuria.
- Pyuria: Presence of pus cells in urine is called pyuria.
- Jaundice: Presence of bile pigments in huge amount in urine is a symptom of jaundice. It is seen during hepatitis or due to blockage of the bile duct.
- Alkaptonuria: Presence of alkaline or homogentisic acid is termed alkaptonuria. When alcapton comes in contact with air than urine becomes black in colour, it is also known as Black urine disease.