Human Urinary SystemHuman Urinary System

kidney

ureter

urinary bladder

urethra

Human Urinary Human Urinary SystemSystem

aorta

renal arteryureter

surinary

bladder

left kidne

y

renal vein

right kidne

ysphincter muscle

urethra

inferior vena cava

Structure of Structure of Mammalian Kidney Mammalian Kidney

made up of three parts:

-cortex - a light

outer region

-medulla - a dark inner region

-pelvis - a whitish central region

leads to ureter

contains numerous tiny tubules called

nephrons

Structure of Structure of Mammalian Mammalian

Kidney Kidney cortexmedulla

renal arteryrenal vein

ureterpelvis

nephron

Bowman’s capsule(with glomerulus)

afferent arteriole

efferent arteriole

loop of Henle

Structure Structure of of

NephronNephron

collecting duct

first & second convolution

venule

NephronNephron

renal artery

renal veinproximal

convoluted tubule (first convolution)

capillaries around nephron

Loop of Henle

afferent arteriole

glomerulusefferent arteriole

collecting duct

distal convoluted

tubule (second convolution)

How does a nephron How does a nephron work ?work ?

By two ways, one is

ultrafiltration and the other

is reabsorption

UltrafiltrationUltrafiltration

diameter of tiny artery leading to

the glomerulus is larger than the

one leaving, so a pressure is set up

as blood tries to force its way out of

the smaller tube

the high hydrostatic pressure forces

small molecules through the walls of

capillaries and Bowman’s capsule

into the capsular space

fluid which filtered into the nephron is

called glomerular filtrate

glomerular filtrate has the same

composition as that of blood except

that it does not contain blood cells,

blood proteins & blood platelets

Reabsorption reabsorption is the process of

absorbing useful substances into

capillaries which wrapped around

tubule

as in glomerular filtrate, some

substances like glucose and amino

acid are useful to human so they are

absorbed back while fluid travels

along the tubule

those urea which remains in the fluid

pass the whole nephron and finally

drains into collecting duct which

leads to pelvis and form urine

urine contains mostly water, with

urea and excess mineral salts

reabsorption of all the glucose and

amino acids and some salts begins in

the first convolution and finished when

the fluid reaches loop of Henle

useful substances are reabsorbed by

diffusion down the concentration

gradient and active transport against

concentration gradient in collecting duct, water is mainly

reabsorbed by osmosis but the first

convolution actually reabsorbs the

largest amount of water

Functions of KidneyFunctions of Kidney

kidney mainly has three functions:

osmoregulation

removal of excess salt

excretion

Functions of Kidney Functions of Kidney - -

OsmoregulationOsmoregulationdrink a lot of

waterblood becomes

diluted

dilute urine is

formed

small proportion of

water is reabsorbed

Amount of water in blood:

CONSTANT

after sweating

blood becomes

concentratedlarge proportion of

water is reabsorbed

concentrated urine is formed

Amount of water in blood:

CONSTANT

Functions of Kidney Functions of Kidney - -

OsmoregulationOsmoregulation

Functions of Kidney Functions of Kidney - Removal of - Removal of

Excess SaltExcess Saltafter eating a salty meal

salt enters blood, concentration of salt in blood increases

volume of urine increases

concentration of urine is higher

man feels thirsty drink water

Functions of Kidney Functions of Kidney - Excretion - Excretion

amino acids are broken down in

liver to form urea by deamination

Urea is carried by blood to the

kidneys which excrete them from

the body in the form of urine

Kidney Failure and Kidney Failure and Artificial Kidney Artificial Kidney

some kidney diseases can lead to

kidney failure and the kidneys can

no longer function properly

toxic substances will accumulate in

blood and patient will die

KIDNEY FAILURE

Caused byBacterial infectionExternal mechanical damageHigh blood pressure

AirAir

traptrap

AirAirtraptrap

pumppump

DialysisDialysis

fluid influid in

Dialysis Dialysis

fluid outfluid out

‘‘

Blood Blood carryingcarrying

wastewaste

‘‘clean’clean’bloodblood

artificial kidney is a bulky machine

attached to patient which is used to

filter and clean patient’s blood

artificial kidney make use of the

principle of dialysis. It has a filter

made of cellophane which acts as a

selectively permeable membrane

along one side of the membrane is

the patient’s blood while the other

side is dialysis fluid which has the

same contain as plasma except urea

only urea diffuses from patient’s

blood into dialysis fluid through

cellophane filter

blood without urea will return to

patient through his vein

dialysis fluid flows in direction

opposite to that of blood flow to

increase the efficiency of diffusion of

urea into dialysis fluid other than using artificial kidney,

kidney transplant is another possible

method but only few people are

willing to donate their kidneys after

death

KIDNEY MACHINEKIDNEY MACHINE

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