excretory system Flashcards
toxic metabolic wastes
nitrogenous wastes
most toxic nitrogenous waste
ammonia, excreated out in forms of urea and uric acid
process of removal of nitrogenous wastes
excretion
osmoconformers
Osmoconformers are animals that do not actively control The osmotic concentration of the body fluids. They change body Fluids according to the osmolarity of the surrounding medium.
Marine and freshwater invertebrates and vertebrate hagfish(myxine)
osmoregulators
maintain an internal osmolarity, different from the surrounding medium that they inhabit by taking in or releasing fluids from their bodies with the expenditure of energy.
most aquatic vertebrates are strict osmoregulators except sharks and rays and hagfish
what is the osmolarity of fresh water and of freshwater organisms
50 mOsm per litre and 200-300 mOsm per litre
how do freshwater organisms combat loss of salts and entry of water from the environment
protozoa like amoeba and paramoecium have special contractile vacuoles that pump out excess water
other organisms have scales of adipose do not drink water dilute urine presence of ionocytes like chloride that can readily uptake salts
osmolarity of seawater
1000mOsm per litre
how do marine and bony fishes prevent water loss in a hypertonic environment
the fish
drink seawater
the cl cells of gill membranes help eliminate excess monovalent ions from body fluid to seawater and divalent cations are eliminated through faecal matter
name two osmolyte
urea and trimethylamine oxide.. they raise osmolarity of the body like in hagfish to make them isotonic to the environment, or slightly hyperosmotic like in sharks
percentage of water required to keep a human alive
at least 88% if they lose 12% of water, they die.
how do desert animals compensate for water loss
they can recover 90% water from metabolic water. once water is available,they rehydrate. example, a can drink 80L of water in 10 mins.
different classifications of animals based on their excretory products
ammonotelism: ammonia, requires large amounts of water to be excreted
found in many bony fishes, aquatic amphibians and aquatic insects such as amoeba,sponge,hydra,cray fish,bony fish and frog tadpole
excreted through diffusion from body surfaces or gills as ammonium ions
ureotelism:terrestrial adaptation, less toxic nitrogenous waste, as urea and uric acid for the conservation of water.urea can be tolerated more as it is 100000 times less toxic than ammonia
in mammals,land amphibians like adult frog and some marine fish
uricotelism:reptiles,birds,land snails,insects. uric acid excreted in form of pellets or gel paste. insolube in water.its important for organisms producing shelled eggs, as uric acid being insoluble precipitates with the egg shell only and doesn’t enter the embryo and harm it.
the ornithine cycle step by step
aka kreb henseleit cycle, occurs in the liver
- co2+ATP+NH3-> carbonyl phosphate
- carbonyl phosphate+orthinine-> citrulline
- citruline+aspartic acid->arginosuccinic acid
- arginosuccinic acid->fumaric acid+arginine
- Arginine+water->urea +orthinine
- the orthinine generated is used in step 2
different excretory structures in different animals
vertebrates: tubular organs called kidneys
Platyhelminthes(like flatworms), rotifers, some annelids and cephalochordate amphioxus: protonephridia/flame cells mainly concerned with osmoregulation
annelids like earthworms: tubular nephridia which remove nitrogenous wastes and help keep an ionic and fluid balance.
insects like a cockroach: Malpighian tubules. help in the removal of wastes and osmoregulation
crustaceans like prawns: green glands/antennal glands
types of nitrogenous wastes
- ammonia: most toxic protein metabolic waste requires a lot of water for its removal. produced in the lives by deamination
- urea: white crystal solid produced by the liver, less toxic, made with CO2+ NH3
- uric acid: produced in the liver, semisolid saves water. found in phosphate-rich bird droppings
- :xanthines and guanines: nucleotide metabolism found in spiders and penguins
- Trimethylamine oxide: specialised product in marine bony fishes
- ornithuric acid: in birds
- Hippuric acid: produced from benzoic acid in mammals
- creatinine: from creatine phosphate present in muscles. increased levels indicate kidney damage.
urea level in blood
18-38mg/100 ml of blood
kidneys location
reddish-brown, bean-shaped at the last thoracic and 3 lumbar vertebrae,close to the inner wall of the abdominal cavity.
left kidney is a little higher than the right one due to the space being occupied by the liver on the right side. it is the opposite in other mammals.
weight of a kidney
120-170 gms
place on the kidney from where vessels, ureters and nerves emerge
hilum, at the inner concave notch
3 protective coverings of the kidney
- renal fascia: outermost fibrous covering linking it with the abdominal wall. the kidneys are fused with the body wall on the dorsal side. the peritoneal cover is present on the ventral side, making it retroperitoneal arrangement
- adipose capsule: middle covering involving adipose tissue and acts as a shock absorber
- renal capsule: it is the innermost tough protective cover made up of white connective tissues, with a few elastic fibres and few muscles.
internal structure of the kidney
inner to the hilum is the broad funnel-shaped base called renal pelvis lined by transitional epithelium with projections called calyces
the outer layer is a tough capsule
there are two zones, the outer cortex and inner darker medulla. the medulla is divided into few conical masses called the medullary pyramids which project into the calyces.
the cortex that extends to the calyces and is in between the pyramids is called columns of Bertini
the renal pyramids
larger base towards the cortical side and apex called renal papilla towards the cavity. the papillae project into the cavity forming minor calyces which join to form major calyces.
medulla region has a higher osmotic concentration equal to 1200mOsm/L due to conc of NaCl and urea
cortex close to the medulla region
juxtamedullary area
ureters
pair of whitish distensible muscular tubes of 25-30 cm in length and 3mm in diameter
walls of ureter
adventitia, middle muscular and inner mucosa. the muscles are always undergoing peristalsis.
outer longitudinal, middle circular and inner longitudinal muscles of the muscular coat.
urinary bladder
median pyriform sac
the fully distended bladder becomes ovoid in shape
has three parts, apex fundus and neck
fundus has a triangular area called trigone. it has openings of ureters and internal urethral orifice
neck region has two sphincters, involuntary internal sphincter and external voluntary sphincter
walls of the urinary bladder
outer adventitia made of soft connective tissue
middle muscular layer aka the detrusor muscle.has involuntary circular muscles in the middle and longitudinal on the sides.
inner mucosa has loose connective tissue towards the side and transitional epithelium/ureothelium towards the luemn.
urethra
only in mammals
straight in females,2-4 cm long, the urinary aperture in the vulva in front of the vaginal aperture.
in males, it is 20cm long, passes through prostate ad the cowpers glands and also releases sperms
structural and functional unit of the kidney
nephron/uniferous tubule
parts of the nephron
glomerulus and renal tubule
glomerulus
tuft of capillaries by branching of afferent arterioles of the renal artery . the glomerular capillaries join to form the efferent arteriole
components of renal tubule
bowman’s capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
describe the bowman’s capsule
blind double walled cup shaped structure which encloses the glomerulus two layers- visceral layer(inner wall):flat squamous epithelial cells on the periphery and specialised podocytes in the middle part.they enclose slits called filtration pores
parietal layer(outer wall):flat squamous epithelium
spaceb/w the two layers is known as capsular space
what does the malphigian body consist of
glomerulus along with bowmans capsule
aka renal corpuscle
proximal convulated tubule
lower part of bowmans capsule leads to pct
highly coiled surrounded by peritubalar capillaries
lined by cuboidal long brush border epithelium
function of pct
there cells have abundant mitochondria, to perform active absorption and secretion
loop of henle
hairpin like tube which descends into the medulla it has a descending limb(L) and ascending limb(R)
what is the distal convoluted tube
the ascending limb continues as the dct, a highly convoluted tube lying close the malpighian body
what are the collecting ducts
the dct of many nephrons open into a straight tube called collecting duct,many of which open into renal pelvis through medullary pyramids in the calyces. though they start from the cortex
they enter the medulla and form ducts of bellini
what is the vasa recta
U shaped minute vessel of the peritubular capillaries that run parallel to the loop of henle
where is vasa recta highly reduced or absent
cortical nephrons
two types of nephrons
cortical nephrons:most abundant. the loop of henle is too short and barely extends into the medulla
juxtamedullary nephrons:very few, the loop of henle is long and extends into the medulla
which parts of the nephron are part of the medulla
loop of henle and collecting tubules
what is the juxtaglomerular apparatus(JGA)
the epithelial cells of the distal convoluted tubule come in contact with the afferent and the efferent arterioles and are more dense than the other tubular cells and collectively called macula densa. along the side of macula densa,the wall of afferent arteriole contains modified smooth muscle cells called juxtaglomerular cells. with the macula densa,they make up the JGA.
release renin which regulates blood pressure and glomerular filtrate rate.
steps in urine formation
glomerular filtration
reabsorption
secretion
how much blood is present in the kidneys at a given time
1.1-1.2 L , 20%of total blood volume
where is glomerular filtration taking place
glomerulus
how does glomerular filtration take place
the glomerular capillary blood pressure causes the filtration through three layers
the endothelium of glomerular capillaries which have small holes called fenestra
the epithelium of Bowman’s capsule made of podocytes arranged in such a manner that there are slit pores formed
the basement membrane between these two layers
what is ultrafiltration
glomerular filtration
what does glomerular filtrate contain
everything except proteins passes into the lumen of Bowmans capsule. the proteins leave via the peritubular tubules then via the vasa recta.
development of filtration pressure
the large diameter of afferent arteriole compared to efferent arteriole
blood pressure in glomerular blood(GHP)
60mm Hg aka glomerular hydrostatic pressure
blood colloidal osmotic pressure(BCOP)
osmotic conc. of proteinaceous content of glomerular blood
30mmHg
capsular hydrostatic pressure(CHP)
the pressure of interstitial fluid and pressure of renal filtrate
20mmHg
glomerular filtration pressure
the pressure exerted on the blood undergoing filtration
GHP-(BCOP+CHP)
60-50
=10mmHg
glomerular filtration rate
180 litres per day
autoregulation of glomerular filtration
- myogenic autoregulation(decreases): rise in blood pressure, increasing the passage of calcium ions due to stretching of vascular walls of the glomerulus. the calcium ions cause the cells to contract and hence check the overstretching of the vascular walls and raise vascular resistance so that the gfr is brought back to normal
- juxtaglomerular apparatus(Increases): at he location of contact between dct and afferent tubules. they release renin when a decrease in blood pressure and GFR. the renin converts angiotensinogen to active hormone angiotensin by constricting the efferent arteriole, therefore, restoring GFR
- neural control(decrease): sympathetic nervous system, constriction of renal arteries, causes the decrease in renal blood flow and GFR
where does tubular reabsorption take place
mainly in proximal convoluted tubule
what is tubular reabsorption
reabsorbing essential items from the primary glomerular filtrate (99% from 180 L per day of filtrate formed)
what is absorbed passively in tubular reabsorption
nitrogenous wastes
water in the initial parts of the nephron
what is absorbed actively in tubular reabsorption
glucose, amino acids, sodium
what is tubular secretion?
secretion of metabolic wastes from tubular cells into the filtrate. it includes secretion of K+,h+,ammonia,hippuric acid,creatinine.drugs,pigments,toxins.
helps in the ionic and acidic balance of body
its the only mode of excretion in animals with no glomeruli like desert animals and amphibians.
function of pct
absorption of 70-80% of electrolytes and water due to cuboidal brush border epithelium
helps maintain pH, ionic balance
absorption of HCO3-
secretion of ammonia and hydrogen and potassium
the function of loop of Henle
The primary function of the Loop of Henle is the recovery of water and sodium chloride from the filtrate. Hence the function of Loop of Henle is the conservation of water.
- the thin descending limb, it is permeable to water but impermeable to electrolytes, it releases water back into the body(medullary fluid)
- the thick ascending limb, from the concentrated urine,ions and electrolytes(nacl) are released back into the blood
function of dct
reabsorption of na and water and HCO3
selective secretion of K, H, NH3
maintains pH, K Na ion balance
the function of collecting tubules
they reabsorb the water and also some urea which makes its way to the medullary region of the loop of Henle, hence facilitating more absorption of water back into the body via osmosis from the descending limb(aka urea recycling)
pH, secretion of hydrogen and potassium, ionic balance
mechanism of concentration of the filtrate
based on the length of the loop of Henle
the flow of filtrate in the two limbs of Henle in opposite directions and thus forms a counter current(even in the vasa recta)
the counter-current helps maintain an increasing osmolarity towards the inner medullary interstitium
300mOsmL in cortex to 1200 in the medulla. this gradient is mainly caused by NaCl and urea.
NaCl transported by ascending limb of the loop of Henle- exchanged with descending branch of vasa recta-nacl returned to interstitium by ascending portion of vasa recta( counter-current mechanism)
this helps in drawing out water back into the body and concentrating the filtrate by at least 4 times than initial filtrate.
regulation of kidney function by ADH
excessive loss of fluid activates receptors in the hypothalamus to release vasopressin from the posterior pituitary and absorb water from latter parts of the nephron
it can also increase blood pressure and GFR
deficiency of ADH
diabetes insipidus
regulation of kidney function by JGA
operates a multi hormonal renin-angiotensin-aldosterone system (RAAS)
when there is a drop in the GFR, the renin released converts the angiotensinogen from the liver to active peptide hormone angiotensin 1 which converts(angiotensin-converting enzyme from lungs ) further to angiotensin 2. angiotensin 2 constricts the efferent arterioles to constrict and more blood in the glomerulus.
signals more reabsorption of NaCl and water from the pct
stimulates the adrenal gland to absorb more water and ions from distal parts of the tubules.
so increases blood pressure and volume, and GFR.
atrial natriuretic factor(ANF)
opposes RAAS
released by the wall of the atria when there is an increase in blood volume and pressure.
vasodilation of blood vessels
inhibits the reabsorption of na+ by the distal tubules(collecting duct) and reduces the release of aldosterone from the adrenal gland. it also increases the excretion of Na+ from the urine.
what causes micturition
the voluntary signal is given by the CNS, contraction of the walls of smooth muscles in the urinary bladder and relaxation of the sphincter.
this mechanism is called micturition reflex
indication of diabetes mellitus
glucosuria and ketonuria in urine
hyposecretion of insulin
albumin in urine disorder
injury in the renal tract, glomerulonephritis
bile salts and pigments in urine
jaundice, bile is excreted via poop
glucosuria
glucose in urine
ketonuria(acetoacetic acid, hydroxybutyric acid)
diabetes mellitus or prolonged fasting
creatinine in urine
hyperthyroidism, starvation
uremia
accumulation of urea in the blood,can cause kidney failure
nephritis
inflammation of the kidney
glomerular nephritis
inflammation of the glomerulas
pyelonephritis
inflammation of the kidney in the pelvis region
cystitis
urinary bladder inflammation
renal calculi
stone or oxalate masses in kidney
polyurea
excessive urine passed out
alkaptonuria
a genetic disease where homogentisic acid is excreted out with urine
pyuria
pus in the urine
haematuria
blood in the urine
average urine expelled out of the body per day
1.5 L
urochrome
Urobilin or urochrome is the chemical primarily responsible for the yellow colour of urine by
processing of dead blood cells in the liver.
haemodialysis
artificial kidney
blood taken out of radial artery of the patient cooled to 0 Celcius and mixed with heparin
pumped into a machine
has a cellophane paper impermeable to plasma proteins
the nitrogenous waste diffuse from the blood channels to the outside dialysis fluid
clean blood pumped back into the radial vein
kidney transplant
treatment of choice for kidney failure, compared with a lifetime on dialysis.
what is inulin
fructose storage polysaccharide which the body cant metabolised
filtered through kidney
therefore used to check the functioning of kidneys
tubular maxima
the maximum amount of substance that can be retained by blood after which its excreted out in the urine
glucose:180mg/100ml of blood
