Excretion 3 Flashcards
define micturition
The process of release of urine is called micturition and the neural
mechanisms causing it is called the micturition reflex.
describe the steps of micturition reflex
Urine formed by the nephrons is ultimately carried to the urinary bladder
where it is stored till a voluntary signal is given by the central nervous
system (CNS). This signal is initiated by the stretching of the urinary bladder
as it gets filled with urine. In response, the stretch receptors on the walls
of the bladder send signals to the CNS. The CNS passes on motor messages to initiate the contraction of smooth muscles of the bladder and
simultaneous relaxation of the urethral sphincter causing the release of
urine.
describe urine
An adult human
excretes, on an average, 1 to 1.5 litres of urine per day. The urine formed
is a light yellow coloured watery fluid which is slightly acidic (pH-6.0)
and has a characterestic odour. On an average, 25-30 gm of urea is
excreted out per day. Various conditions can affect the characteristics of
urine.
explain where urine analysis can be unseful
Analysis of urine helps in clinical diagnosis of many metabolic
discorders as well as malfunctioning of the kidney. For example, presence
of glucose (Glycosuria) and ketone bodies (Ketonuria) in urine are
indicative of diabetes mellitus.
In diabetes mellitus, the extra glucose present in the blood is excreted in the urine. Since insulin functioning is improper in diabetes mellitus, the cells use the proteins for energy instead of blood glucose. Hence the breakdown of proteins lead to the formation of ketone bodies which are excretedout
other excretory organ: lungs
Our lungs remove large amounts of CO2
(approximately 200mL/
minute) and also significant quantities of water every day.
other excretory organ: liver
Liver, the largest
gland in our body, secretes bile-containing substances like bilirubin,
biliverdin, cholesterol, degraded steroid hormones, vitamins and drugs.
Most of these substances ultimately pass out alongwith digestive wastes.
other excretory organ: skin and srbaceous glands
The sweat and sebaceous glands in the skin can eliminate certain
substances through their secretions. Sweat produced by the sweat
glands is a watery fluid containing NaCl, small amounts of urea, lactic
acid, etc. Though the primary function of sweat is to facilitate a cooling
effect on the body surface, it also helps in the removal of some of the
wastes mentioned above. Sebaceous glands eliminate certain
substances like sterols, hydrocarbons and waxes through sebum. This
secretion provides a protective oily covering for the skin.
t small amounts of nitrogenous wastes could be eliminated through
saliva
what is renal calculi
Stone or insoluble mass of crystallised salts (oxalates,
etc.) formed within the kidney.
what is glomerulonephritis
Inflammation of glomeruli of kidney.
what is uremia
Malfunctioning of kidneys can lead to accumulation of urea in blood,
a condition called uremia, which is highly harmful and may lead to
kidney failure.
describe hemodialysis
In such patients, urea can be removed by a process
called hemodialysis. Blood drained from a convenient artery is
pumped into a dialysing unit after adding an anticoagulant like heparin.
The unit contains a coiled cellophane tube surrounded by a fluid
(dialysing fluid) having the same composition as that of plasma except
the nitrogenous wastes. The porous cellophane membrance of the tube allows the passage of molecules based on concentration gradient. As
nitrogenous wastes are absent in the dialysing fluid, these substances
freely move out, thereby clearing the blood. The cleared blood is
pumped back to the body through a vein after adding anti-heparin to
it
when do we do kidney transplant
Kidney transplantation is the ultimate method in the correction of
acute renal failures (kidney failure). A functioning kidney is used in
transplantation from a donor, preferably a close relative, to minimise its
chances of rejection by the immune system of the host. Modern clinical
procedures have increased the success rate of such a complicated
technique.
