The Excretory System Class 10 ICSE Notes
ICSE Class 10 Biology Chapter 9 The Excretory System Notes, Summary, Definition, Diagram. The Excretory System Notes.
Excretion –
→ process of removal of chemical wastes , unwanted nitrogenous waste products from the body is known as excretion.
→ Plays an important role in maintaining the homeostatic (steady state) condition of the body.
Substances to be eliminated by excretion –
1) Carbon dioxide and water (respiratory products) –
→ CO2 eliminated through lungs
→ Extra water released out of body in form sweat
2) Nitrogenous waste – urea, uric acid and ammonia
→ Mainly produced in liver from dead protein
→ Any extra amino acids cannot be stored in the body.
→ Broken down in liver to glucose and urea
→ Urea is highly poisonous, if accumulated in body can cause death
3) Excess salts such as common salt (NaCl) and even some excess water soluble vitamins(B &C) need to be eliminated.
4) Water
5) Bile pigments (yellow bilirubin)
→ Are breakdown products of haemoglobin of dead RBCs.
The Excretory Organs –
1.) Kidneys –
→ Primary excretory organs eliminating nitrogenous waste from blood through urine
2.) Skin –
→ Sweat excreted by sweat gland of skin excretes out water and NaCl along with small amount of urea and lactic acid.
→ Sweat gland pass out sweat only for cooling are not for excretory.
3.) Lungs –
→ Ecrete out CO2 from body through expired air.
4.) Liver –
→ Detoxification of ammonia by converting it into urea.
→ Also break down bad cholesterol, alcohol, nicotine and drugs.
Kidney –
→ 2 bean shaped organ
→ 10cm long and 6cm wide
→ Located on either side of backbone and protected by last 2 ribs.
→ Ureter arises from the notch (hilum) in the median surface of each kidney and connects behind with the urinary bladder in lower abdomen part.
→ The front end of ureter expanded into kidney called pelvis.
→ A sphincter (circular muscle) guards the opening of bladder into urethra and relaxes only at the time of urination (micturation) under as impulse from the brain.
Kidney → ureter → urinary bladder→ urethra → urine excreted out
Internal structure of the kidney
→ 2 main region
i.) Outer dark cortex
ii.) Inner lighter medulla –
- Composed of finely striped substance arranged in several conical pyramids.
- Apex of each pyramid is called papilla which projects into the pelvis of kidney
- Portions of conical tissue extend in between adjacent renal pyramids to form renal columns
- Kidney is composed of an enormous number of minute tubules called uriniferous tubules or nephrons or renal tubules or just kidney tubules.
Structure of kidney tubule
→ Each kidney tubule has following parts –
i.) Bowman’s capsule –
- Thin-walled (single cell thick epithelium) cup
- Hollow ball pressed deep on one side continues tubule.
- It contains a mass of blood capillaries called glomerulus.
- Bowman’s capsule and glomerulus together called malpighian capsule or renal capsule.
ii.) Proximal/first Convulated Tubule (PCT) –
- is starting Convulated region of tubule
- Both Bowman’s capsule and PCT lie in the cortex giving dotted appearance in sectional view.
iii.) Loop of henle (middle U shaped part) –
- Is like a hairpin shaped not convulated
- Runs in medulla to turn back and re-enter the cortex to continue in next Convulated region of tubule.
iv.) Distal Convulated Tubule (DCT) –
- Is the end part of kidney tubule
- It opens into a collecting duct
v.) Collecting duct –
- Receive the content of many kidney tubules and pours it as urine in pelvis of kidney
Internal structure of the kidney
→ 2 main region
i.) Outer dark cortex
ii.) Inner lighter medulla –
- Composed of finely striped substance arranged in several conical pyramids.
- Apex of each pyramid is called papilla which projects into the pelvis of kidney
- Portions of conical tissue extend in between adjacent renal pyramids to form renal columns
- Kidney is composed of an enormous number of minute tubules called uriniferous tubules or nephrons or renal tubules or just kidney tubules.
Structure of kidney tubule
→ Each kidney tubule has following parts –
i.) Bowman’s capsule –
- Thin-walled (single cell thick epithelium) cup
- Hollow ball pressed deep on one side continues tubule.
- It contains a mass of blood capillaries called glomerulus.
- Bowman’s capsule and glomerulus together called malpighian capsule or renal capsule.
ii.) Proximal/first Convulated Tubule (PCT) –
- is starting Convulated region of tubule
- Both Bowman’s capsule and PCT lie in the cortex giving dotted appearance in sectional view.
iii.) Loop of henle (middle U shaped part) –
- Is like a hairpin shaped not convulated
- Runs in medulla to turn back and re-enter the cortex to continue in next Convulated region of tubule.
iv.) Distal Convulated Tubule (DCT) –
- Is the end part of kidney tubule
- It opens into a collecting duct
v.) Collecting duct –
- Receive the content of many kidney tubules and pours it as urine in pelvis of kidney
→ Henle’s loop and collecting ducts lie in medulla giving it a striped appearance in a sectional view.
Blood supply to the Kidney Tubules –
→ From dorsal Aorta, a pair of renal arteries enters kidney.
→ Each renal artery produces afferent arteries which enters Bowman’s capsule and breaks down as form a bunch of capillaries glomerulus.
→ This is a reunited capillary of glomerulus form efferent arteriole which breaks into secondary capillary network which surrounds renal tubule and rejoins vein.
→ Many united vein of kidney form renal vein which leaves kidney at median surface.
Renal artery → afferent arteriole → Bownman’s capsule → Glomerulus → Efferent arteriole → PCT → Loop of Henle → DCT → Collecting Duct
Functions of kidney – production of urine
1) Ultrafiltration –
→ Part of blood plasma is filtered out under pressure through glomerulus into Bowman’s capsule.
→ The fluid entering the renal tubule is called glomerular filterate.
→ Glomerular filtrate consists of water, urea, salts, glucose and other plasma solutes.
→ Thus the blood proceeding away from the glomerulus is relatively thick.
2) Reabsorption –
→ Glomerular filterate entering the renal tubule is not urine.
→ Selective absorption – reabsorption is only to the extent that the normal concentration of blood is not distributed.
3) Tubular secretion –
→ K+ and chemicals like penicillin are passed into urine in DCT.
→ This passage involes the activity of cells of tubular wall, hence called tubular secretion.
→ The filterate left after reabsorption and tubular secretion is called urine.
→ Oxygen deman of kidneys is 6 to 7 times higher than what is required by muscles.
Urine excretion –
→ urine is expelled from urinary bladder through urethra (penis male, directly in female) by relaxation of sphincter muscles located at opening of urethra under impulse from nervous system
→ This process is called micturation.
Physical properties of urine –
1) Colour – clear yellow , colour varies with diet
2) Volume – 1 to 1.5 litres per day but varies
3) pH – 5 to 8, usually slightly acidic (pH=6), protein diet makes it more acidic while vegetable diet makes it alkaline.
4) Odour – smell of urine becomes strong, ammonia-like due to bacterial activity, otherwise faint smell
5) Specific gravity – 1.003 to 1.035
Constituent s of urine –
→ 95% of water
→ 5% solid wastes
Organic in (g/L)
→ Urea – 2.3 g/L
→ Creatinine – 1.5 g/L
→ Uric acid – 0.7 g/L
→ Others – 2.6 g/L
Inorganic in (g/L)
→ Sodium chloride – 9 (g/L)
→ Potassium chloride – 2.5 (g/L)
→ Ammonia – 0.6 (g/L)
Abnormal constituents in urine
i.) Blood cells –
→ known as haematuria
→ blood passes with urine due to some infection in urinary tract, kidney stones or tumour.
ii.) Glucose –
→ Known as glycosuria
→ Excess glucose passes with urine due to diabetes mellitus (sugar diabetes)
iii.) Albumin –
→ Condition termed as albuminuria
→ Due to high blood pressure or increased permeability of Bowman’s capsule membrane on account of bacterial infection
→ Albumin protein maybe passed via urine
iv.) Bile pigments –
→ Due to anaemia, hepatitis (jaundice) or liver cirrhosis, urine may contain bile pigments.
Diabetes insipidus –
Urine becomes tasteless when there is much water in urine
Due to insufficient ADH hormone
Regulation of urine output –
- Pituitary gland and dieresis (increased production of urine)
- Concentration of urine by water reabsorption is controlled by antidiuretic hormone (ADH) secreted by the posterior lobe of pituitary gland.
- If ADH secretion is reduced there is an increased production of urine known as “diuresis”
- Liquid diets, tea, coffee, alcohol, etc causes increase in formation of urine.
Osmoregulation –
- kidney while removing wastes like urea from the blood also regulates its composition,i.e. the percentage of water and salts.
- It implies the regulation of osmotic pressure of blood.
Artificial kidney –
- If one kidney is damaged or removed, the other kidney is sufficient for excretory needs and person can lead to a normal life.
- But failure of both kidneys would lead to death.
- Hence an artificial kidney is a dialysis machine.
- Patient’s blood is led from radial artery in his arm through the machine where urea and excess salts removed and purified blood is returned o vein in same arm.
- N case of permanent damage to the kidneys, dialysis is to be repeated for about 12 hours twice a week.
Glossary –
1.) Gout – uric acid is relatively less soluble in water and may crystallize and get deposited in the joints
2.) Kidney stone – excessive uric acid and certain salts like calcium oxalate , when kidneys are not working fully normally.
3.) An immediate treatment to replenish water in the blood by glucose-saline drip or by giving oral rehydration solution through mouth.
For more update follow net explanations homepage
Very good notes keep it up