Question

What are the Functions and physiology of the urinary system?

Answer 1

The Urinary organs include the kidneys, ureters, bladder, and urethra.
1. Kidneys -Bean shaped structure

There are three major regions of the kidney, renal cortex, renal medulla and the renal pelvis. The outer layer is the renal cortexand Inner part is Medulla .This medulla contains pyramid shaped tissue called the renal pyramids, separated by renal columns.

2)The ureters are continuous with the renal pelvis and is the it carries the urine from kidneys to urinary bladder

3)Urinary bladder act as storage of urine
.
4) Urethra --From urinary bladder urine goes into urethra from where it is excreted outside.

Kidneys ---->>Ureters----->>Urinary bladder ----->Urethra ----->>Urine excreted outside

Function of Kidneys
1.Excretory function--->One of the major functions of the Kidney is the process of excretion. Excretion is the process of eliminating, from an organism, waste products of metabolism.eg Urea from protein breakdown ,Creatinine from muscle breakdown ,Urea from nucleic acids breakdown ,bilirubin from haemoglobin breakdown .

2. Regulatory function ---->
a)Water balance though secretion of ADH antidiuretic hormone
b)Electrolyte balance( Na+ K+ Hco3- ) through Alsosterone   and
c)Acid base balance .

3.Endocrine function ---->
a) Erythropoetin production which stimukate to produce RBC red blood cells in Bone marrow .
b) Activates Vitamin D
c) Secretes Renin which through Renin Angiotensin Aldosterone axis controls Blood pressure and blood volume .
d) Prostaglandin synthesis ---> function as Vasodilators of renal afferent arteriole and maintain Glomerular filtration rate .

4) Metabolic function ---->
a) Ammoniogenesis formation of ammonia and help in excretion of excess of acids om ammonium form
b) Gluconeogensis ---Formation of glucose from amino acids
.
Functions of
1)Ureters are narrow thick walled muscular tubes which carrh urine from kidneys to Urinary bladder .

2)Urinary badder --->Storage of urine

3)Urethra --Passage of urine outside of body .

Physiology of urinary system .
Kidneys are made up of millions of nephrons .
Nephron is the microscopic structural and functional unit of the kidney.Around 1.2 million neohrons are present in each kidney . It is composed of 2 parts renal corpuscle and a renal tubule.

1)The renal corpuscle consists of a tuft of capillaries called a glomerulus and an Bowman's capsule.

2)The tubule has five anatomically and functionally different parts:
a)The proximal tubule, which has a convoluted part the proximal convoluted tubule followed by a straight section (proximal straight tubule)
b)The loop of Henle, which has two parts, the descending loop of Henle ("Descending loop") and the ascending loop of Henle ("Ascending loop"); the distal convoluted tubule ("Distal loop");
c)The connecting tubule, and d)The Collecting ducts.

Nephrons have two lengths with different urine concentrating capacities: long juxtamedullary nephrons and short cortical nephrons.

Physiology of urine formation
1.Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion

a)As the blood passes through glomerulus
Ultrafiltrate of plasma is formed containg glucose ,Amino acids vitamins creatinine urea ,uric acid .It is known as ultrafiltarte as all the substances present in plasma are filtered except plasma proteins .Roughly around 1100-1200 ml of blood is filtered through glomerulus which is around 1/5 th of total blood pumped out by ventricels ( Cardiac output )

Ultrafiltrate form because of increasing Hydrostatic pressure pushing the fluids from glomerulus into Bowmans capsule.It reaaches the Proximal convoluted tubule where glucose ,amino acids vitamins is completely reabsorbed hence the filtrate is isotonic to plasma .and the osmolality of filtrate is equal to serum osmolality 285-290 mosm/kg water .

b)Filtrate is not changed even after the process of reabsorption from proximal convoluted tubule ( PCT) .This phenomenon is "Isoosmotic Reabsorption"

c)Counter Current system - Two tubes closed to each other but the direction of flow of fluids in two tubes is in opposite direction .

d)At the tip of Loop of Henle ( serum osmolality is 1200 mosm) After PCT through the thin descending Limb water is being reabsorbed to reach maximum serum osmolaity as It is completely permeable to water and impermeable to solutes like Nacl . This process is known called as "COUNTER CURRENT MULTIPLICATION."

e)Lowest serum osmolality 50 mosm is there at Distal convoluted tubule because thick descending limb of Loop of Henle is permeable to solutes Nacl and impermeable to water .Now as solutes are present in medullary interstitum medullary osmotic gradient is increased .

f)Now from 50 mosm to 800-900 mosm /kg of water is achieved by using ADH hormone Antidiuretic hormone

Along with Loop of Henle Vasa recta are present around peritubular capillaries and responsible for "COUNTER CURRENT EXCHANGE"

For ADH to act Following factors are required
a).Medullary Interstitial osmolality
b) Urea
C) Vasa recta

Thus "COUNTER CURRENT MULTIPLICATION " establishes the medullary osmotic gradient and is maintained by COUNTER CURRENT EXCHANGE".

g)Finally filtrate reaches the Colleting duct where again tubular secretion occur and
ADH act on Principal cells of cortical collecting duct and and act on V2 receptor and through aquaporins cause facultative water absorption and form concentrated
Urine .