Epithelial
tissues are the interface between internal fluids and the external environment,
creating osmotic barriers in lower organisms. Other specialized epithelial
tissues that mediate osmotic and ionic regulation are gills, digestive tract
and specialized excretory tissues in different animal groups. Animals remove
toxic ammonia to less toxic forms by excretion. Three main strategies of
nitrogen excretion are ammonoteles (ammonium), Uricoteles (uric acid) and
Ureotelism (Urea). Most aquatic animals are ammonotelic, whereas terrestrial
animals are uricotelic (reptiles and birds) or ureoteles (mammals). Urea is
produced by the Ornithine cycle/Urea cycle in the liver.
Invertebrates have primitive kidneys such as
protonephridia and metanephridia. Water balance in insects is regulated by
Malphigian tubules. Ion and water regulation in vertebrates are carried out by
the kidneys. The functional units of kidney is the nephron. Urine is formed by
3 processes, Glomerular filtration, tubular reabsorption and tubular secretion.
Filtration occurs at the glomerulus, a ball of capillaries surrounded by the
Bowman’s capsule. From the Bowman’s capsule the primary urine enters the
proximal tubule, and proceeds to the loop of Henle, with its ascending and
descending limbs. The hypertonic fluid then flows to the distal tubule and
through the collecting duct into the ureters, the urinary bladder, after a
short storage it is sent out of the urethra. Central to the nephron is the
counter current system set up between the loop of Henle and the collecting duct
along with the capillaries that serve the nephron.
Kidney function is regulated at different levels.
GFR is affected by colloidal osmotic pressure and capsular hydrostatic pressure
between the glomerulus and Bowman’s capsule, surface area available for
filtration are the factors that affect filtration pressure. The kidneys act
only on the plasma, yet the extra cellular fluid consists of both plasma and
interstitial fluid. The interstitial fluid is the true internal fluid
environment of the body. Interstitial fluid is the only component that comes in
direct contact with the cells. Thus by performing regulatory and excretory
roles on the plasma, the kidneys maintains the proper interstitial fluid
environment for optimum cell functioning.
Various hormones control diuresis. Vasopressin
alters the permeability of the collecting duct, the renin- angiotensin system,
sympathetic system and aldosterone act together to regulate Na+, K+,
water and pressure balance.
Both the
kidneys of Ravi (28 years) were not functioning and he was undergoing dialysis.
He was admitted to a hospital with renal failure. His mother Suganthi (47
years) was willing to donate one of her kidneys to her son after she was given
counseling. Their blood groups were matching and later approval was obtained
from transplant committee and technical committee. Operation was performed for
5 hrs.
He was
administered with immunosuppressive drugs and anti inflammatory drugs.
He
recovered from the operation and returned home.
1.
Name the disease Ravi was suffering from.
2.
What relation is the donor of the kidney
3.
Name the type of matching done to perform the
transplant.
4.
Why approval has to be got from transplant
committee and technical committee?
5.
What do you think about Suganthi donating her
kidney?
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