PHYSIOLOGY OF EXCRETION. KIDNEY FUNCTIONS. MECHANISMS OF URINE FORMATION.
lungs
Skin- sweat glands
liver
Organs & tissues
kidney
GIT
blood
Excretory system lungs - СО2, Н2О
vapour, ethers, chlorophorm
Sweat glands- Н2О, salts, urea, uric acid, creatinin.
Liver – bile pigments, products of haemoglobin break down
GIT - Н2О, salts Kidney is the main
organ of excretion
EXCRETORY SYSTEM
KIDNEY
NEPHRON
Different types of nephronesCortical
Jucstar-medullar
TYPES OF NEPHRONSCortical – main nephrons allowing urine
formation (60-70%).Jucstar-medullar – have long Henle loops,
enable urine concentration. (10-20%)Superficial – have short Henle loops, play the
role of shunts (20-30%)
MECHANISMS OF URINE MECHANISMS OF URINE FORMATIONFORMATION
FILTRATIONREABSORPTION
SECRETION
ObligatoryREABSORPTION
FacultativeREABSORPTION
Regulated water reabsorp-tionfiltration
Counter-current system
MECHANISM OF MECHANISM OF GLOMERULA GLOMERULA FILTRATIONFILTRATION
GLOMERULA FILTER
GLOMERULA FILTER1 –capillary endothelium2 – basal membrane3 – podocyte4- pores in the endothelium5 – fissura in podocyte membrane
Glomerular diuresis - filtration
hydrostatic
F = Р h. – Р оn. – Р f.=70-30-20=20 mm HgІ Blood hydrostatic pressure (Р h.) -70
mm Hg
ІІ Blood oncotic pressure (Р оn.) - 30 mm Hg
ІІІ Ultrafiltrate hydrostatic pressure (Р f.) - 20 mm Hg
Factors influencing filtration pressure
Increase in hydrostatic pressure
Increase in hydrostatic pressure
Decrease in oncotic pressure
Increase in oncotic pressure
Factors determining high hydrostatic pressure in glomerulus
Short renal artery starts right from the abdomenal aortha
Vas afferens is twice wider than vas efferens
OBLIGATORY REABSORPTION
PCT epithelium structure
OBLIGATORY OBLIGATORY REABSORPTIONREABSORPTION
Na+, K+, Ca+2, Mg +2, Cl--, SO4
2-- , HPO42--, HCO3
--, vitamins - diffusion
Amino acids, glucose –secondary active transport
urea, uric acid – diffusionH2O - оsmosis
2/3 of filtrated urine is reabsorped
SECONDARY ACTIVE TRANSPORT
АТФ
К+
Na+
Na+Glucose
Apical membrane
Basilar membrane
Urea role in urine concentrationReabsorption – 1/3 of
filtered urea is reabsorped in PCT; it increases Рosm. of parenchime & helps to reabsorb water in DCT.
secretion
UreaUric acid
Regulation of obligatory reabsorptionSympathetic nervous system, cateholamines, glucocorticoids
Intracellular messengers
Metabolism in epithelial cells (energy formed)
Substances transport
FACULTATIVE REABSORPTION
Facultative reabsorptionFacultative reabsorption• Sodium, chlorine – is
regulated by aldosterone & natriuretic peptide;
• Calcium - is regulated by parathormone, calcitonin & Vit D3 .
Regulated reabsorption of water under the influence of ADH (vasopressin)
Aldosterone diuresis influence
Adrenal glands
Sodium decrease
aldosterone Collecting duct
DCT
REGULATION OF SODIUM REABSORPTION
Aldosteronincreases
Natriuretic peptideinhibits
Regulation of calcium reabsorption
Parathormone,Vit D3
increases
Calcitonininhibits
АDH effect on water reabsorption in the collecting ducts
Basilar membrane
Apical membrane
V2receptor
GS-protein,Gyanile nucleotide
adenylatecyclase
АDH
c-АМPPROTEINKINAZE
Proteins phosphorilation
Н2О
Н2О
SecretionSecretion – – substances transport substances transport from blood to urinefrom blood to urine
urea, weak acids & bases, ammonium, ammonia (diffusion)
Organic acids & bases, penicilinum (active transport)
Sodium, potassium, аmonia, urea
Counter-current system
Types of epithelium in canaliculli
Counter-current system mechanism
Н2О Н2О
Н2О Na
NaРоsm Роsm
SCHEME OF PROCESSES IN FINAL URINE SCHEME OF PROCESSES IN FINAL URINE FORMATIONFORMATION
FILTRATION
REABSORPTION
SECRETION
EXTRUSIONWITH FINAL
URINE
Filtration Reabsorption Secretion Filtration& reabsorption
Filtration& Secretion
inulin Glucose (normally)
K Urea, glucose in hyperglucemia
Diodrast
Non-threshold substancesNon-threshhold
substances – are substances which are excreted with final urine regardless of their concentration in blood
Velocity of glomerular filtrationVelocity of glomerular filtration - - clearensclearens
Velocity of glomerular filtrationVelocity of glomerular filtration ((clearens)clearens) is a volume of blood plasma which was filtrated via kidney in certain time.
Filtrometric substances are used to Filtrometric substances are used to define clearensdefine clearens (инулин, креатинин), they are non-threshold substances which are neither secreted nor reabsorped
In man – 125 ml/minIn woman -110 ml/min
CLEARENS DETERMINATION
РРcrcr. х . х FF = = UcrUcr. х . х VVРРcrcr.. Creatinin concentration in blood plasma;UU crcr.. Creatinin concentration in final urine; FF –volume of primary urine; VV- volume of final urine.
UcrUcr. х . х VVРРcrcr..
F=F=
Threshold UBSTANCESThreshold
SUBSTANCES – are substances which have threshold of elimination & are excreted with final urine only if their concentration in blood is above threshold
KIDNEY FUNCTIONS CONNECTED WITH URINE FORMATION
EXCRETION OF:
End products of metabolism (urea, uric acid, creatinin)
Pigments which are formed at haemoglobin breakdown (urobilin, urochrome)
Metabolites of hormones & other biologically active substances
Drugs & substances which enter with food
HOMEOSTASIS MAINTENANCE due to excretion of threshold substancesIonic content of blood(Na, Cl, K, SO4,)Osmotic pressure (Na & H2O)Q (volume of blood in circulation) & BP
(due to regulation of water excretion)Glucose & amino acids levelBlood pH regulation (due to regulation of H+
, bicarbonate, sulfate, phosphate anions excretion)
KIDNEY FUNCTIONS NOT CONNECTED WITH URINE FORMATION
ENDOCRINE FUNCTION:
Renin-angiotensine-aldosterone systemVit D3
ErithropoetinsAnticoagulating system factors (urokinase,
heparine,antithrombines)Prostaglandines (A2, E2)Kinins (bradikinin, kallikrein)
METABOLICProtein metabolism (fermentative
hydrolysis of proteins with amino acids formation and their release into the blood stream)
Carbohydrates metabolism (glucose reabsorption & gluconeogenesis)
Lipids metabolism (tryacilglicerides &phospholipids formation)
KIDNEY IN HOMEOSTASIS MAINTENANSE
Salt-water balance regulation
Isotonic solution, food
intestines
v. portae
liver
Physiological swelling (up to 30%) Hepatic osmoreceptors
hypotalamus
АDH
Н2О reabsorption
diuresis Q
Kidney in osmotic pressure regulation
Decrease in ADH secretion
Increase in ADH secretion
Increased water reabsorption in kidney
decreased water reabsorption in kidney Decrease in
plasma osmotic pressure
Decrease in plasma osmotic pressure
Osmotic pressure regulation
Роsm blood
Hypothalamus osmoreceptors
SO & PV nn.
Posterial pituitary
АDH
Н2О reabsorption
diuresis
Q
Роsm
Adrenal glands
aldosterone
Na+ reabsorption
OSMOTIC PRESSURE REGULATION
РOSM
Hypothalamus osmoreceptors
SO & PV nn
Posterior pituitary
АDH
Н2О reabsorption
diuresis
Роsm
Nauretic hormone
выделение Na+
Q REGULATION
Q threshold350 ml
BP
Volume receptorsof hypothalamus
Volume receptorsof atrium
АDH
SO & PV nn.
Н2О reabsorption
diuresisQ
BP
UGА
renin
angiotensin
Adrenal glands
aldosterone
Na+reabsorption Н2О reabsorption
QРosm =
EFP filtration diuresis
Q REGULATION
Q
Volume receptors of hypothalamus
АDH
Н2О reabsorption
diureisRight atrium
Na-uretic hormone
Na+ excretion
Q