Q: Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.

\$\textbf{Solution:}\$ Alveoli Nephrons\$\bullet\$ air sacs present in the lungs facilitate the exchange of gases. \$\bullet\$ Filtration units of kidneys that filter blood and forms urine.\$\bullet\$ They belong to the respiratory system. \$\bullet\$ They are a part of the excretory system.\$\bullet\$ They are made of simple squamous epithelium. \$\bullet\$ They are made of simple cuboidal epithelium.\$\bullet\$ They are surrounded by blood vessels.\$\bullet\$ They are surrounded by blood vessels as well as made up of blood vessels (Glomerulus part).\$\bullet\$ Around 350 million alveoli are found in each lung.\$\bullet\$ Approximately 1.5 million nephrons are present in each kidney.

Q: Explain excretion in human beings.

The wastes that are produced in human body are removed by the process of excretion. Human body consists of a number of excretory organs such as liver, skin, kidneys etc. But there is a specialized system in humans that helps to purifies blood. That is called excretory system. It consists of Kidneys, ureters, urethra, urinary bladder . Kidneys are placed in lower abdomen and bean like shaped. They filter the blood and removes toxins from the blood. It also reabsorbs the essential ions and substances from the filtrate. The final toxins are collected and removed from the body in the from of urine. The urine is 95% of water in composition and rest it contains urea and other wastes.

Question 1

Describe the structure and functioning of nephrons.

Accepted Answer

A nephron is the filtration unit of the kidney. It consists of a tubule which is connected with collecting duct at one end and a cup-shaped structure at the other end. This filtrate contains glucose, amino acids, urea, uric acid, salts and a major amount of water.

Question 2

Explain the Human Excretory System with the help of suitable diagram.

Accepted Answer

Human excretory system:(a) In humans, the excretory system consists of a pair of kidneys, a pair of ureters, urinary bladder and urethra.(b) Kidneys are two bean shaped organs lying at the back of the abdomen, one on either side of the vertebral column. Waste products from the blood and urine are removed by the kidney.(c) A Nephron is the basic filtration unit of the kidney. It is a cluster of thin walled blood capillaries.(d) The urine produced by filtering the blood is transported to the urinary bladder. This is done by a pair of ureters. Ureters are long muscular tubes.(e) Urinary bladder is a muscular bag like structure which can hold urine. The urinary bladder is under the control of nerves. When the bladder is full one get urge to urinate.(f) This urine is thrown out of the body through urethra.(g) Apart from the kidney, the skin and lungs are also helpful in the excretion.

Question 3

Draw a well-labelled diagram of a human excretory system. Write the functions of(a) Kidney(b) Ureter(c) Urinary bladder

Accepted Answer

(a) Kidney- Kidneys filter the blood and remove nitrogenous wastes and other toxic substances from the blood and help in urine formation.(b) Ureter- The ureters are the tubes that carry urine from kidneys to the urinary bladder.(c) Urinary bladder- It is the reservoir of urine and stores urine until it is excreted out.

Question 4

Draw labelled diagram of a nephron. Explain the process of urine formation.

Accepted Answer

The process of urine formation in kidneys include the following steps:(i) Glomerular filtration - Urine formation begins when the blood is filtered by the glomerulus and enters the Bowman's capsule and the glomerular filtrate is formed. The afferent arteriole entering the glomerulus is wider than the efferent arteriole in diameter. This increases the blood pressure within the glomerulus helps in the filtration. Glomerular filtrate is formed of all blood constituents except corpuscles and plasma proteins.(ii) Tubular reabsorption - When the glomerular filtrate comes to the proximal tubule then the essential nutrients are reabsorbed. Glucose, amino acids, water, ions like sodium, potassium, chloride, bicarbonate, magnesium, calcium are reabsorbed from the glomerular filtrate. When the filtrate finally comes to the collecting duct ADH (anti-diuretic hormone) acts and reabsorbs the excess water and decreases the urine volume.(iii) Tubular secretion - When the glomerular filtrate is in the proximal tubule cretinine, uric acid are secreted in it. When the filtrate goes to the distal part urea, potasium ion and some hydrogen ions are secreted in it.

Question 5

Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.

Accepted Answer

$\textbf{Solution:}$           Alveoli                   Nephrons$\bullet$ air sacs present in the lungs facilitate the exchange of gases. $\bullet$ Filtration units of kidneys that filter blood and forms urine.$\bullet$ They belong to the respiratory system. $\bullet$ They are a part of the excretory system.$\bullet$ They are made of simple squamous epithelium. $\bullet$ They are made of simple cuboidal epithelium.$\bullet$ They are surrounded by blood vessels.$\bullet$ They are surrounded by blood vessels as well as made up of blood vessels (Glomerulus part).$\bullet$ Around 350 million alveoli are found in each lung.$\bullet$  Approximately 1.5 million nephrons are present in each kidney.

Question 6

Draw a labelled diagram of nephron.

Accepted Answer

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Question 7

Which of the following is not a function of kidneys?

Accepted Answer

The kidneys remove excess organic molecules from the blood, which are the waste products of metabolism. They are also essential in controlling homeostatic functions, such as the regulation of electrolytes, maintenance of acid-base balance, and regulation of blood pressure (via maintaining salt and water balance). They serve the body as a natural filter of the blood, and remove water soluble wastes. The kidneys also produce hormones, including calcitriol, erythropoietin, and the enzyme renin.

Question 8

Explain excretion in human beings.

Accepted Answer

The wastes that are produced in human body&#10;are removed by the process of excretion. Human body consists of a number of&#10;excretory organs such as liver, skin, kidneys etc. But there is a specialized&#10;system in humans that helps to purifies blood. That is called excretory system.&#10;It consists of Kidneys, ureters, urethra, urinary bladder .&#10;&#10;Kidneys are placed in lower abdomen and&#10;bean like shaped. They filter the blood and removes toxins from the blood. It&#10;also reabsorbs the essential ions and substances from the filtrate. The final&#10;toxins are collected and removed from the body in the from of urine. &#10;&#10;The urine is 95% of water in&#10;composition and rest it contains urea and other wastes.

Question 9

Describe in brief how urine is produced in human body.

Accepted Answer

Our body produces waste chemical compounds like- Urea and Uric acid. These waste compounds are filtered out from blood in the kidney So, the kidney is nothing bur filtration unit for blood.Nephrons are the basic structures present in the kidney that help in the filtration process of blood.It has two parts- Bowman's capsule and Renal Tubule. Bowman's capsule is  cup-shaped and consists of the coiled tube of blood capillary - Glomerulus, this helps in filtering out the blood. The filtrate goes to the Renal tubule.But some substance in this initial filtrate like- Glucose, amino acids, salts gets absorbed selectively along with  major amount of water in the capillaries surrounding the renal tubule, as it passes through it. The rest of the liquid moves through the collecting duct towards the urinary bladder to get stored, before micturition.

Question 10

What is the significance of Juxtaglomerular apparatus (JGA) in kidney function ?

Accepted Answer

Juxta glomerular apparatus is a group of specialized cells from afferent arteriole and distal convoluted tubule of a nephron. They help in maintaining the blood pressure and glomerular filtration rate through renin angiotensin system. Juxta glomerular cells secrete renin based on the stimulation of stretch receptors in the walls of arterioles. They result in aldosterone production and thus regulate the salt absorption from the filtrate and regulate the blood pressure.

Revise with Concepts

Human Excretory System

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Human Excretory System - An Introduction

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