Urinary System, Kidney, Nephron, Function of Kidney, Urinary System Disease, Process of urine formation- Glomerular Filtration, Re absorption, Secretion

1. Urinary System
By
Yogeshwary M. Bhongade
Assistant Professor
Kamla Neharu College of Pharmacy, Butibori, Nagpur

2. Urinary System
• The urinary system, also known as the renal
system or urinary tract, consists of the
kidneys, ureters, bladder, and the urethra.
• The purpose of the urinary system is to
eliminate waste from the body, regulate
blood volume and blood pressure, control
levels of electrolytes and metabolites, and
regulate blood pH.

3. Kidneys
• The kidneys are a pair of bean-
shaped organs on either side of your
spine, below your ribs and behind
your belly.
• Each kidney is about 4 or 5 inches
long, roughly the size of a large fist.
• The kidneys' job is to filter your
blood.

4. Functions of Kidney
There are a pair of kidneys that are purplish-brown and are located below
the ribs in the middle of the back.
• Remove waste from the blood in the form of urine
• Keep substances stable in the blood
• Make erythropoietin, a hormone which helps make red blood cells
• Make vitamin D active
• Regulate blood pressure
• The kidneys remove waste from the blood through tiny filtering units
called nephrons.

5. Position of Kidney
• The kidneys lie retroperitoneally (behind the peritoneum) in the
abdomen, either side of the vertebral column.
• They typically extend from T12 to L3, although the right kidney is often
situated slightly lower due to the presence of the liver.
• Each kidney is approximately three vertebrae in length.
• The adrenal glands sit immediately superior to the kidneys within a
separate envelope of the renal fascia.

6. Structure of Kidney
The kidneys are encased in complex layers of fascia and fat. They are
arranged as follows (deep to superficial):The kidneys are encased in complex
layers of fascia and fat.
They are arranged as follows (deep to superficial):
• Renal capsule – tough fibrous capsule.
• Perirenal fat – collection of extraperitoneal fat.
• Renal fascia (also known as Gerota’s fascia or perirenal fascia) – encloses
the kidneys and the suprarenal glands.
• Pararenal fat – mainly located on the posterolateral aspect of the kidney.

8. • Internally, the kidneys have an intricate and unique structure. The renal
parenchyma can be divided into two main areas – the outer cortex and inner
medulla. The cortex extends into the medulla, dividing it into triangular
shapes – these are known as renal pyramids.
• The apex of a renal pyramid is called a renal papilla. Each renal papilla is
associated with a structure known as the minor calyx, which collects urine
from the pyramids. Several minor calices merge to form a major calyx.
Urine passes through the major calices into the renal pelvis, a flattened and
funnel-shaped structure. From the renal pelvis, urine drains into the ureter,
which transports it to the bladder for storage.
• The medial margin of each kidney is marked by a deep fissure, known as
the renal hilum. This acts as a gateway to the kidney – normally the renal
vessels and ureter enter/exit the kidney via this structure.

10. • Microscopically kidneys are made up of number of structural and
functional unit known as nephrons.
• There are about one millions nephron in each kidney.
• A nephron consist of two parts-
1. Malphigian bodies made up of Bowman’s capsule and Glomerulus.
2. Renal Tubules

11. A Nephron
• A nephron is the basic structural and
functional unit of the kidneys that regulates
water and soluble substances in the blood by
filtering the blood, reabsorbing what is
needed, and excreting the rest as urine.
• Its function is vital for homeostasis of blood
volume, blood pressure, and plasma
osmolarity.
• It is regulated by the neuroendocrine system
by hormones such as antidiuretic hormone,
aldosterone, and parathyroid hormone.

12. The Glomerulus
• The glomerulus is a capillary tuft that receives
its blood supply from an afferent arteriole of
the renal circulation. Here, fluid and solutes are
filtered out of the blood and into the space
made by Bowman’s capsule.
• A group of specialized cells known as
juxtaglomerular apparatus (JGA) are located
around the afferent arteriole where it enters the
renal corpuscle. The JGA secretes an enzyme
called renin, due to a variety of stimuli, and it is
involved in the process of blood volume
homeostasis.

13. • The Bowman’s capsule (also called the glomerular capsule) surrounds
the glomerulus. It is composed of visceral (simple squamous epithelial
cells; inner) and parietal (simple squamous epithelial cells; outer)
layers. The visceral layer lies just beneath the thickened glomerular
basement membrane and only allows fluid and small molecules like
glucose and ions like sodium to pass through into the nephron.
• Red blood cells and large proteins, such as serum albumins, cannot pass
through the glomerulus under normal circumstances. However, in some
injuries they may be able to pass through and can cause blood and
protein content to enter the urine, which is a sign of problems in the
kidney.

14. Proximal Convoluted Tubule
• The proximal tubule is the first site of water reabsorption into the
bloodstream, and the site where the majority of water and salt
reabsorption takes place. Water reabsorption in the proximal convoluted
tubule occurs due to both passive diffusion across the basolateral
membrane, and active transport from Na+/K+/ATPase pumps that actively
transports sodium across the basolateral membrane.
• Water and glucose follow sodium through the basolateral membrane via
an osmotic gradient, in a process called co-transport. Approximately
2/3rds of water in the nephron and 100% of the glucose in the nephron are
reabsorbed by cotransport in the proximal convoluted tubule.
• Fluid leaving this tubule generally is unchanged due to the equivalent
water and ion reabsorption, with an osmolarity (ion concentration) of 300
mOSm/L, which is the same osmolarity as normal plasma.

15. The Loop of Henle
• The loop of Henle is a U-shaped tube that consists of a descending limb
and ascending limb.
• It transfers fluid from the proximal to the distal tubule.
• The descending limb is highly permeable to water but completely
impermeable to ions, causing a large amount of water to be reabsorbed,
which increases fluid osmolarity to about 1200 mOSm/L.
• In contrast, the ascending limb of Henle’s loop is impermeable to water
but highly permeable to ions, which causes a large drop in the
osmolarity of fluid passing through the loop, from 1200 mOSM/L to
100 mOSm/L.

16. Distal Convoluted Tubule and Collecting Duct
• The distal convoluted tubule and collecting duct is the final site of
reabsorption in the nephron. Unlike the other components of the nephron, its
permeability to water is variable depending on a hormone stimulus to enable
the complex regulation of blood osmolarity, volume, pressure, and pH.
• Normally, it is impermeable to water and permeable to ions, driving the
osmolarity of fluid even lower. However, anti-diuretic hormone (secreted from
the pituitary gland as a part of homeostasis) will act on the distal convoluted
tubule to increase the permeability of the tubule to water to increase water
reabsorption. This example results in increased blood volume and increased
blood pressure. Many other hormones will induce other important changes in
the distal convoluted tubule that fulfill the other homeostatic functions of the
kidney.

17. • The collecting duct is similar in
function to the distal convoluted
tubule and generally responds the
same way to the same hormone
stimuli. It is, however, different in
terms of histology.
• The osmolarity of fluid through the
distal tubule and collecting duct is
highly variable depending on
hormone stimulus. After passage
through the collecting duct, the fluid
is brought into the ureter, where it
leaves the kidney as urine.

18. • Urine is a waste byproduct formed from excess water and metabolic
waste molecules during the process of renal system filtration. The
primary function of the renal system is to regulate blood volume and
plasma osmolarity, and waste removal via urine is essentially a
convenient way that the body performs many functions using one
process.
• Urine formation occurs during three processes:
1. Filtration
2. Reabsorption
3. Secretion

19. Filtration
• During filtration, blood enters the afferent arteriole and flows into the
glomerulus where filterable blood components, such as water and
nitrogenous waste, will move towards the inside of the glomerulus, and
nonfilterable components, such as cells and serum albumins, will exit via
the efferent arteriole. These filterable components accumulate in the
glomerulus to form the glomerular filtrate.
• Normally, about 20% of the total blood pumped by the heart each minute
will enter the kidneys to undergo filtration; this is called the filtration
fraction. The remaining 80% of the blood flows through the rest of the
body to facilitate tissue perfusion and gas exchange.

20. Reabsorption
• The next step is reabsorption, during which molecules and ions will be
reabsorbed into the circulatory system.
• The fluid passes through the components of the nephron (the
proximal/distal convoluted tubules, loop of Henle, the collecting duct) as
water and ions are removed as the fluid osmolarity (ion concentration)
changes.
• In the collecting duct, secretion will occur before the fluid leaves the
ureter in the form of urine.

21. Secretion
• During secretion some substances±such as hydrogen ions, creatinine,
and drugs—will be removed from the blood through the peritubular
capillary network into the collecting duct.
• The end product of all these processes is urine, which is essentially a
collection of substances that has not been reabsorbed during glomerular
filtration or tubular reabsorbtion.
• Urine is mainly composed of water that has not been reabsorbed, which
is the way in which the body lowers blood volume, by increasing the
amount of water that becomes urine instead of becoming reabsorbed.

22. • The other main component of urine is urea, a highly soluble molecule
composed of ammonia and carbon dioxide, and provides a way for
nitrogen (found in ammonia) to be removed from the body. Urine also
contains many salts and other waste components.
• Red blood cells and sugar are not normally found in urine but may
indicate glomerulus injury and diabetes mellitus respectively.

23. Glomerular Filtration
• Glomerular filtration is the renal process whereby fluid in the blood is
filtered across the capillaries of the glomerulus.
• Glomerular filtration is the first step in urine formation and constitutes
the basic physiologic function of the kidneys. It describes the process
of blood filtration in the kidney, in which fluid, ions, glucose, and
waste products are removed from the glomerular capillaries.
• Many of these materials are reabsorbed by the body as the fluid travels
through the various parts of the nephron, but those that are not
reabsorbed leave the body in the form of urine.

25. Ureter
• The ureter is a tube that carries urine from the kidney to the urinary
bladder.
• There are two ureters, one attached to each kidney.
• The upper half of the ureter is located in the abdomen and the lower half
is located in the pelvic area.
• The ureter is about 10 to 12 inches long in the average adult. The tube
has thick walls composed of a fibrous, a muscular, and a mucus coat,
which are able to contract.

26. Bladder
• The bladder is an organ of the urinary system. It plays two main roles:
• Temporary storage of urine – the bladder is a hollow organ with
distensible walls. It has a folded internal lining (known as rugae), which
allows it to accommodate up to 400-600ml of urine in healthy adults.
• Assists in the expulsion of urine – the musculature of the bladder
contracts during micturition, with concomitant relaxation of the
sphincters.

27. Urethra
• Urethra, duct that transmits urine from the bladder to the exterior of the
body during urination.
• The urethra is held closed by the urethral sphincter, a muscular structure
that helps keep urine in the bladder until voiding can occur.

28. Female urethra
• The female urethra is embedded within the vaginal wall, and its opening
is situated between the labia.
• The female urethra is much shorter than that of the male, being only 4
cm (1.5 inches) long.
• It begins at the bladder neck and opens to the outside just after passing
through the urethral sphincter.

29. Male Urethra
• Male urethra have lenght 20 cm
• It consis of three parts.
1. Pelvic Part
2. Perineal Part
3. Pineal Part

30. Micturation
• It is the act of passing urine.
• when urine accumulate in the bladder, it produce stretching of its
walls.
• This raises the pressure within the bladder.
• This occure within 170 - 230 mof urine has collected in bladder.
• This stimulate the afferent nerves of the bladder.
• The impulses are carried to higher centres which control mixturation.
• Micturation occures due to contraction of muscular coat of bladder
and relaxation of the sphincture.
• It is also assisted by contraction of abdominal muscle.

31. Disease of Urinary System
Glomerulo Nephritis
• Glomerulonephritis is a group
of diseases that injure the part of
the kidney that filters blood
(called glomeruli).
• Other terms you may hear used
are nephritis and nephrotic
syndrome. When the kidney is
injured, it cannot get rid of
wastes and extra fluid in the
body.

32. Pyelitis
• An inflammation in pelvis of kidney due to infection
• Pyelitis (pyelonephritis) is a bacterial infection of the renal pelvis. A
urinary tract infection or a [bladder infection] is usually responsible
for pyelitis.
• If a lower urinary tract infection goes unnoticed or is does not receive
proper treatment, bacteria can spread to the renal pelvis and also
infect this area.
• Pyelitis is treated with antibiotics.

33. Polyurea
• Excessive urination can have causes that aren't due to underlying
disease.
• Examples include intake of large amounts of fluid and alcohol use.

34. Anuria
• Anuria or anuresis occurs when the kidneys aren't producing urine.
• A person may first experience oliguria, or low output of urine, and
then progress to anuria.
• Urination is important in removing both waste and excess fluids from
your body.
• Your kidneys produce between 1 and 2 quarts of urine a day.

35. Renal Calculi
• Kidney stones are hard deposits of minerals and acid salts that stick
together in concentrated urine.
• They can be painful when passing through the urinary tract, but
usually don't cause permanent damage.
• The most common symptom is severe pain, usually in the side of the
abdomen, that's often associated with nausea.
• Treatment includes pain relievers and drinking lots of water to help
pass the stone. Medical procedures may be required to remove or
break up larger stones.

36. Cystis
• Cystitis is an inflammation of the bladder.
• Inflammation is where part of your body becomes irritated, red, or
swollen. In most cases, the cause of cystitis is a urinary tract infection
(UTI).
• A UTI happens when bacteria enter the bladder or urethra and begin to
multiply.

37. Oedema
• Oedema, also known as dropsy, is
the medical term for fluid
retention in the body.
• The build-up of fluid causes
affected tissue to become
swollen.
• The swelling can occur in one
particular part of the body

38. Oedema of renal failure
• It occures when plasma proteins are excreted in kidney failure.
• This produces a decrease in osmotic pressure of blood.
• So entry of fluid at the verious side is decreased .
• This leads to accumulation of fluid in tissue spaces.
• It result in swelling leading to oedema.

39. Oedema of lymphatic obstruction
• It occures mostly after radical mastectomy ( Removal of breast).
• In this procedure , the lymph gland which drain the axilla are also
removed.
• so edema occures in elephantiasis cause by filariasis.
• Oedema is due to obstruction of the lymphatics by parasite

40. Oedema of Thrombosis
• It is seen in thrombosis of deep veins of leg.
• It is due to prolong confinement to bed due to which flow of blood is
sluggish.
• So clots form which further obstruct blood flow producing oedema.

41. Thank You