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