Renal system. Learning objectives zTo outline the renal system; zTo describe the structure and...

Renal system

Learning objectives

To outline the renal system;To describe the structure and function of neph

ron,processes of urine formation;To describe briefly the processes of urine form

ation;To describe the renin-angiotensin system;To describe the regulationofpotassium, calciu

m and pH.

RENAL SYSTEM

EXCRETION

~ removal of toxic waste productions of metabolism from the body

WASTE

~ nitrogenous waste (urea & ammonia), CO2, bile pigment

RENAL SYSTEM

OSMOREGULATION

~ the process maintaining constant osmotic equilibrium between the internal & external environment of an organism

Mammalian renal system I

KIDNEY paired organs in abdominal cavity

held firmly by peritoneum

embedded in fat

solid, dark red & bean shape

below stomach

renal artery vs renal vein

Structure of kidney

Mammalian renal system II

URETERS narrow tubes

passing urine from kidneys to bladder

valves prevent back flow of urine stop bacteria from going into

kidney

Kidney

Bladder

Urethra

Ureter

Diaphragm

Mammalian renal system III

URINARY BLADDER muscular bag

stores urine temporarily

300 cm3 of urine sensation of urination

contraction of bladder + relaxation of sphincter muscle forces urine out

Ureter

Urethra

Ureteral opening

Urethral orifice

Mammalian renal system IV

URETHRA muscular tube

carries ONLY URINE in female

carries URINE & SEMEN in male

A nephron unit

FLOW OF GLOMERULAR FILTRATEFLOW OF GLOMERULAR FILTRATE

Glomerulus Bowman’s space in Bowman’s capsule

Descending limb of Henle’s loop Proximal convoluted tubule

Ascending limb of Henle’s loop Distal convoluted tubule

Renal pelvis Collecting duct

NEPHRON

1,000,000 nephrons / kidney

structural & functional units

Cortical nephron

~ in cortex, short Loop of Henle, osmoregulation under NORMAL condition

Juxtamedullary nephron

~ at junction of cortex & medulla, long Loop of Henle, osmoregulation when SHORT OF WATER

NephronRenal corouscle Glomerulus: knot of blood capillaries

Bowman’s capsule Proximal convoluted tubuleDescending limb of loop of HenleAscending limb of loop of HenleDistal convoluted tubuleCollecting duct

Functions of kidney

Excretion

~ remove nitrogenous waste i.e. urea, salts, water, heat, toxic substance

Osmoregulation

~ controlling amount of water in body

~ maintain osmotic potential

Urine Formation

Pressure filtration (ultrafiltration)

ReabsorptionTubular secretion

Ultrafiltration

Occur at Malpighian bodyGlomerular filtrate: all substances in blood except R

BCs & plasma protein

Blood pressureBlood pressure: Diameter of afferent arteriole > Diameter of efferent arteriole Glomerular filtrate rate 180l/ day Adaptation large area, great pressure, thin ,membrane

Reabsorption

99% of the glomerular filtrate are reabsorbedmatter reabsorbed:

all glucose, amino acid

mineral salts

other useful substances

SELECTIVE REABSORPTIONMethod of reabsorption

diffusion active transport

Sites of reabsorption

Proximal convoluted tubule

~ major site of reabsorption (80%)

~ microvilli surface area

~ numerous mitochondria

~ surrounded by pertubular capillaries

Sites of reabsorption

Loop of Henle

~ conserve water in terrestrial mammal

~ creates & maintain an increasing osmotic gradient in the medulla

~ Na+ in medulla vigorous osmotic extraction of water from collecting ducts hypertonic urine

Formation of hypertonic urine

Sites of reabsorption

Vasa recta

~ narrow capillaries situated close to loop of Henle

~ freely permeable to ions, urea & water

~ Counter current exchanger system

Counter current exchange system

Sites of reabsorption

Distal convoluted tubule

~ fine control of salt, water & pH balance of the blood

Collecting duct

~ water is extracted by osmosis conc. hypertonic urine

Tubular secretion

Takes place in distal convoluted tubuleabsorption of unnecessary: ammonia,

potassium & drug from capillary network & secrete them into lumen of tubule

Regulation of urine composition

Anti-diuretic hormone(ADH)AldosteroneRenin-angiotensin system

ADH

ADHADH

Aldosterone

Renin angiotensin system

Potassium content

most abundant intracellular ionreabsorbed by proximal convoluted tubule & l

oop of Henle, secreted by collecting ducts K secretion aldosterone secretion of K

Calcium content

Ca excitability of nerve & muscle cell membranes hypocalcemic tetany

Ca cardiac arrthythmiasmost reabsorbed, no secretion

pH level

Metabolic reactions are highly sensitive to H+

Sources of H+ gain or loss

Gain ~ from CO2, metabolism of protein etc,

loss of CO3 2- in diarrhea & urine

Loss ~ in vomitus & urine