The human excretory system is crucial for removing metabolic waste products, including carbon dioxide, water, urea, and uric acid. Key organs involved are the kidneys, ureters, urinary bladder, and urethra, with the kidneys playing a primary role in excretion and osmoregulation. The urine formation process includes steps like ultrafiltration, tubular reabsorption, and secretion, ultimately leading to urination, with an adult typically producing 1-1.8 liters of urine daily.

1. HUMAN EXCRETORY SYSTEM: EASY
DIAGRAM OF IT
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HUMAN EXCRETORY SYSTEM
INTRODUCTION:-
Various waste products are formed in our body as a result of many
metabolic activities taking place inside the body. These waste substances if
accumulated would poison cells or slow down their metabolism. Hence, the body must
get rid of these unwanted substances.The metabolic wastes to be excreted include
CO2, H2O, fat, ammonia, urea and uric acid. (EXCRETION SYSTEM)
The nourishment coming from food that is simplified or processed by digestion is consumed by the blood and
conveyed all through the body. When this absorbed food is broken down in the tissues and many toxic and
poisonous substances are produced which should be removed as they may be fatal if present beyond a
certain concentration. The removal of these substances is known as excretion. Excretion and
osmoregulation, both are interconnected processes and occur side by side. in higher vertebrates like
humans, kidneys perform both the functions, excretion as well as osmoregulation.The system responsible for
these function is known as the excretory system or urinary system
DEFINITION
1)Excretion: It is the removal of metabolic waste from the body. (EXCRETION SYSTEM)
2) Osmoregulation: It is the process by which the water content and ion concentration are regulated in the
cells. By this, the osmotic pressure (thrust) of blood is kept constant. (balanced) (EXCRETION
SYSTEM)
VARIOUS EXCRETORY ORGANS: ( EXCRETION SYSTEM)
Humans possess a number of excretory organs like skin, lungs, liver and kidneys. Skin,
lungs and liver are considered as accessory excretory organs while Kidneys are the
most important excretory organs.
TYPE OF EXCRETORY
ORGAN
EXCRETORY PRODUCTS SPECIALITY
1)SKIN
*salts
*water
*some ions
Here excretory products pass
out through the ducts of glands
and pores
2)SWEAT GLAND
*dissolved salts like sodium
chloride
*lactic acid
*traces of urea
*amino acids
*glucose
Sweat flows out from the
sweat gland ducts on the
surface of the skin
3)SEBACEOUS GLAND *wax-like secretion containing These are secreted out through

2. lipids, sterols, fatty acids,
hydrocarbon
( EXCRETION SYSTEM)
the ducts on the surface of the
skin
4)LUNGS
*carbon dioxide
*water vapour
These are removed by way of
expiration.
5)LIVER
*bile pigment-containing
biliverdin and bilirubin
Removed along with faeces.
6)LIVER
*cholesterol
*products of complex
hormones
*alcohol
*nicotine
*drugs
*urea formed by the reation of
ammonia with CO2
Removed along with faeces
7)KIDNEYS
*urea
*other nitrogenous waste
Eliminated through urine.
( EXCRETION SYSTEM)
HUMAN EXCRETORY SYSTEM

3. The excretory system in human beings consists of the following parts: ( EXCRETION SYSTEM)
* Kidneys
* ureters
* urinary bladder
*urethra
KIDNEYS:
The Kidneys are ruddy dark colored or dark pink in coloured, a combined structure that lie along the backside
of the stomach on either side of the vertebral column section. They are protected by the last two pairs of ribs
(floating ribs). The shape of the kidney is of bean seed with a length of 10 cm, breadth of 6 cm and with the
thickness of 4 cm. The right kidney is situated somewhat lower than the left kidney as the correct side of the
stomach hole is occupied by the liver. They are held in position by padding. On the inner side of the concave
or curved side of the kidney is present a
notch or ridge which is called hilum. It is the place from where the ureter and the renal vein come out and the
renal artery enters to kidney.
URETERS:-
The ureters arise from within the renal sinus of the kidneys at hilum. The anterior part of each ureter is a
funnel-shaped structure, the renal pelvis. The ureters passes urine from the kidneys to the urinary bladder.
Each ureter opens obliquely in the urinary bladder by a slit-like aperture to prevent
back flow of the urine.
URINARY BLADDER:- ( EXCRETION SYSTEM)
The urinary bladder acts as a muscular reservoir for storage of urine. It lies inside the pelvic cavity of the
abdomen. The opening or neck of the urinary bladder is surrounded by sphincter muscles which act like a
valve which remain closed until the time of micturition (urination). In an adult, the average capacily of the
urinary bladder varies from 150 mL to 300 ml.
URETHRA:-
The urethra is membranous tube that arises from the neck of the urinary bladder and extends up to the
urethral orifice. In male it serves as a common passage from urine and sperms. Urethra in females serves
as an exit for pee in particular..
MICTURITION :- It is the act of voiding the urine. The urine is carried by peristaltic wave down ureter. The
waves originates in a pace makerat the renal end of the ureter. The ureter pass obliquely through the thick
muscular wallof the bladder. Accumulation of urine in the bladder raises its pressure, and aspontaneous
reflex is initiated. As the smooth muscles of the bladder wall contract, the urethral sphincter muscles relax,
evacuating the urine. Urinedoes not flow back during contraction of bladder to ureters as theureters pass
obliquely and their terminal
parts get closed during contraction. Micturition may be initiated or delayed voluntarily.

4. INTERNAL STRUCTUREOF KIDNEY
Each Kidney consists of two distinct regions – an outer
part which is renal cortex and an inner region which is known as renal medulla The medulla is subdivided
into 15 or 16 conical masses, the renal pyramids. Each pyramid has narrow renal papilla towards the pelvis
and a broad base toward the cortex. Renal papillae open into a wide funnel-like structure, renal pelvis. The
renal pelvis in turn leads into the ureter.
Each kidney contains endless filtering or seiving units called nephrons. A kidney may have more than 1.2
million nephrons.. Every nephron starts to originate in the cortex area and widely stretches out into the
medulla region distinctly. In a kidney, the renal supply route divides to split into various arterioles and
vessels, for the maximum part in the cortex.The capillaries coil and form little, knot like structures
called glomeruli. Each glomerulus is almost completely surrounded by a cup-shaped structure
called bowman’s capsule which leads into coiled tubules. The tubule after a progressive series of loops and
coliis( curls and circles), joins different tubules and goes through the medulla and opens into the renal pelvis
at the zenith of a pyramid.
PHYSIOLOGY OF URINE FORMATION ( EXCRETION
SYSTEM)
Pee development (preparation of urine) includes three primary procedures: ultrafiltration, cylindrical
reabsorption and rounded emission.
STEPS ARE: ( EXCRETION SYSTEM)
1)Blood from renal artery enters kidneys through afferent arteriole

5. 2)ULTRAFILTRATION: Blood enters glomerulur capillaries. Water and small solutes are filtered in Bowman’s
capsule.
3)TUBULAR REABSORPTION: Water and many solutes are reabsorbed through the wall of nephric tubule
and return to the blood in particular capillaries.
4)Tubular secretion: Cells of renal tubule remove wastes from blood and pass then into the filtrate.
5)Hormonal action adjusts the urine concentration ADH promotes water reabsorption. Aldosterone influences
reabsorption of sodium and potassium. ( EXCRETION SYSTEM)
6)Urination: Water and solutes flow to renal pelvis, then eliminated out through urinary tract.
An adult man normally passes about 1-1.8 litres of urine in 24 hours. Urine is a transparent yellowish fluid.
Its yellow colour is due to a pigment urochrome derived from the breakdown of haemoglobin of worn out
RBCs.
Its pH ranges from 6-8. It has an unpleasant odour. If allowed to stand, the urea present in it, is degraded by
bacteria to ammonia, which gives a strong awful smell to it.