EXCRETION

EXCRETION.
-->NEPHRON :-
          Each kidney has about million of nephron, nephron is structural and functional unit of kidney, each nephron consists of 2 type
1) Renal Corpuscle or Malphigian body :-
           It is upper part of nephron and consists of glomerulus and Bowman's capsule
i) Glomerules :-
           Network of blood capillaries. The arteriole which send the blood to glomerulus called afferent arteriole and which take place off the blood is called efferent arteriole, glomerulural blood capillaries have afferent osteriole is more compare to efferent arteriole which cause pressure
Bowman's capsule :-
            A cup shaped structure in which glomerulus embedded
ii) Tubule :-
          Consists of PCT, loop of Henle ,DCT and collecting tubule
- PCT :-
       Proximal convoluted tubule, this situated at neck of nephron. It is lined by Simple cuboidal epithelium contain brush border which help in reabsorption
- Loop of Henle :-
         U-shaped structure consist ascending and descending limb ,Descending limb is permeable for water not the salt, Ascending limb permeable for salt not water
iii) DCT:-
          It controlled by anti-diuretic harmone which is secreted by posterior lobe of pituitary gland by action of this harmone water reabsorbption take place by DCT
iv) Collecting tubule :-
            Portion helpful in connecting urine
Function of nephron of kidney :-
# Formation of urine :-
- Ultrafication:-
                    In the 1st step of formation about 1100-1200 ml blood flow in the glomerulus /minute
# Filteration of blood :-
          Take place through 3 layer in which one is endothelium layer of glomerulus capillaries
Glomerulus filteration rate (GFR):-
       Amount of blood which filter by glomerulus /minute called GFR, it's value is 125 ml ,
     3 type of pressure involve in ultrafication
1) Glomerular hydrostatic pressure (GHP)  :-
           This pressure create due to narrower efferent arteriole, it's valve is about 75mm Hg
2) Blood colloidal osmotic pressure :- (BCOP)
                Creates due to presence of plasma protein, it value about 32mmHg
3) Capsular hydrostatic pressure (CHP) :-
           This pressure creates due to presence of fluid in Bowman's capsule . It's value is about 18mmHg
Net Filteration pressure (NFP) = GHP -(BCOP+CHP)
= 75-(32+18)
= 25-50
= 25 mmHg
- Reabsorption :-
# In PCT:-
        Coiled anterior tubule which is lined by brush bowlder on simple cuboidal epithelium, it play great role in reabsorption. In PCT almost all glucose, 75% water, 70% Na+, 70% K+ and Cl- ,HCO3- ,reabsorb
# In loop of Henle :-
         About 75% water reabsorb by descending limb of Henle ,this limb not permeable for salt Na+, Cl-, K+, HCO3- reabsorb by ascending limb of loop of henle .it is not permeable for water, so both limb of loop of Henle maintain concentration
# In DCT:-
        About 19% water reabsorbed by DCT by the reaction of antidiuratic harmone which is secreted by posterior lobe of pituitary gland
NaCl, KHCO3, also reabsorb by DCT
# Secretion :-
         NH3, Urea, Uric acid, creative ultimately come into collecting tubule and urine collect in collecting tubule and then enters into pelvic by pyramidal colyceas
Note:
Water reabsorb by PCT and descending limb of Henle without any action of harmone i.e. it take place under normal condition this type of water reabsorbption
Obligatory water reabsorption :-
        About 19% water reabsorb by the action of ADH said to be obligatory water reabsorption
Types of nephron
# Cortical nephron:-
           In most of nephron malphigian body PCT, DCT situated in Renal cortex ,whereas loop of Henle is short, so called cortical nephron (80-90%)
# Juxtamedullary nephron :-
             Some of nephron have been long loop of Henle and malphigian body situated at the junction of cortex and medulla, so they called juxtamedullary nephron (10-20%)
Mechanism of concentration of filterate :-
+ mammals have ability to produce concentrated urine, loop of Henle and vasa recta play important role in this process, the flow of loop of Henle take place In opposite direction and form counter current .the flow of blood in vasa recta is in opposite manner and also form counter current. Both loop of Henle and vasa recta of counter current maintaining the concentration of urine. In these osomolarity increases toward inner medulla whereas decreases in cortex region, this gradient is mainly caused by NaCl and urea. NaCl is transported by ascending limb of loop of Henle and exchange with descending limb of vasa recta,NaCl is returned by ascending portion of vasa recta. similarly small amount of urea enter into thin segment. Ascending limb of loop of Henle and transported to collecting tubule, the above transport of substances fascilitated by special arrangement of loop of Henle and vasa recta. So this process called counter current mechanism and this maintain concentration of filtrate and ultimately urine collect in collecting duct
Regulation of excretory activity :-
Function of kidney regulated by harmonal feedback mechanism by involvement of hypothalamus, juxtaglomerules apparatus (JGA) and heart
1) Hypothalamus :-
            Situated in fore-brain, when excessive loss of food from body take Place so this Activity stimulate hypothalamus to release ADH from posterior lobe of pituitary gland, ADH fascilitates water absorption by DCT and decreases as the volume of urine
Note:-
Diabetes Insipitus :-
                   When a person taking tea, milk or alchohal so decreases release of ADH from pituitary gland, so less reabsorption of water take place by DCT and volume of urine increase,
2) JGA:-
        Fall in glomerular blood flow activate the juxtaglomerular cell to release renin, Renin convert into angiotensinogen II. Which constrict blood vessel and increases glomerular blood pressure and regulate GFR
Angiotension II activate adrenal cortex to secrete aldosterone which help in reaf of Na+ and H2O from DCT, so TBP and GFR. This complete process called Renin angiotensin system
3) Heart :-
       When B.P increase activity activate the artria of heart to release ANF (Atrial Natriuretic factor) which dialates blood vessel and decreases B.P
Micturation :-
       It is volumetric process controlled by CNS  when signal comes from brain initiate contraction of smooth muscle of urinary bladder and stimultaneous relaxation of urethral sphincter causes release of urine
The act of passing of urine from body under the control of CNS
Volume =1.5 L/day
Colour = yellow due to presence of urochrome (breakdown of haemoglobin)
Slightly acidic pH=6.0
Wt. Of urea = 25-30 gm/day
Role of other organ:-
- Lungs:-
       Excrete CO2 (18L/day)
- Liver :-
      Excrete bile pigment (Bile Rubin and bile urdin)
- Sweat gland:-
      Release sweat Containing Nacl, Uretic, H2O
- Sebaceous gland:-
       Release serum
- Sebum :-
     Protective oily covering of skin
Disorder :-
# Urenia = increase amount of urea in blood
# Ketonuria = increase ketone body in urine
# Renal calculi = also called kidney stone, insoluble mass of crystalline salt like oxylate in kidney
# Glomerulone phritis :-
      Inflammation of glomerulus of kidney
# Glycosouria:-
           Presence of glucose in urine
# Heinodialysis or Renal failure :-
        When both kidney become non-functional so accumulation of urea take place in body, which cause ureamia or removal of this urea from body by artificial kidney called haemodialysis