Urinary system of man

Waste products

Products of metabolism which are not needed by organism

Waste products such as…

Uric acid, urea, toxins, drugs, food additives etc

Excretion

The process by which metabolic waste products and toxic materials are removed from the body of organism

Kidney structure

Kidney is reddish brown in colour.

It is bean shaped

Enclosed in tough transparent memb.rane called capsule.

Right kidney is slightly higher than left kidney

Kidneys location

Kidneys are located in the back of the abdominal cavity, one on each side of the vertebral column.

Concave side faces the vertebral column.

Ureter

A thin tube, connecting kidney with urinary bladder

Urinary bladder

A muscular elastic bag which stores urine

Urethra

Tube that leads urine out of body.

Structure of kidney

Renal cortex, Renal medulla, renal pelvis

Renal cortex

Darker outer region, consisting of blood capillaries

Renal medulla

Inner light region, consisting of conical structures called renal pyramids

Nephron

Nephron is the structural and functional unit of kidney. It consists of renale corpuscle and renal tubule

Renal corpuscle consists of

Glomerulus and bowman's capsule

Bowman's capsule

Double walled hollow cup

Glomerulus

A bundle of blood capillaries surrounded by bowman's capsule

Renale tubule consists of

Proximal convoluted tube, loop of Henle, and distal convoluted tube

Afferent arteriole

Brings unfiltered blood to kidney

Efferent arteriole

Takes away filtered blood and wastes away from kidney

Collecting duct

Collecting duct opens up into larger ducts in renal pelvis

Three steps of removal of waste from kidney

Glomerular filtration, tubular or selective reabsorption, tubular secretion

Glomerular filtration

Movement of small molecules across glomerular wall due to blood oressure

Glomerular filtrate

Fluid that leaves the blood is called glomerular filtrate

Selective reasborption

Water and salts are reabsorbed and returned to main stream while the filtrate flows along the nephron

Reabsorption occurs through

Osmosis, diffusion and active transport

Which substances are commonly absorbed

Substances like glucose and amino acids are completely reabsorbed

Descending loop of henle

Reabsorption of salts

Ascending loop of henle

Reabsorption of water

Distal convoluted tube

Reabsorption of water in blood

Tubular secretion

Substances actively transported from blood capillaries to nephron tubules

Tubular secretion substances include

K and H ions, drugs, uric acid, creatinine

Urine

After all steps taken by nephron, filtrate remaining in renal tubules is urine, which moves to collecting duct and then pelvis

Water content in urine

95%

Urea content

9.3g/L

Cl ions

1.87 g/L

Na ions

1.17 g/L

K ions

0.750 g/L

Other ions and compounds

Variable

Thirst centre

Hypothalamus

Excess water in body

Kidneys form dilute urine (hypotonic)

More water is filtered

less water is reabsorbed

Shortage of water

Kidneys form concentrated (hypertonic) urine

Less water is filtered

More water is reabsorbed