This document provides an overview of the structure and function of nephrons, the functional units of the kidney. It begins with an introduction to nephrons and their role in excretion and homeostasis. It then describes the main parts of the nephron in detail, including the renal corpuscle, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct. It also discusses the types of nephrons and renal circulation. In summary, the document outlines the key components and processes of the nephron to explain its role in filtering blood and forming urine.

1. WELCOME

2. PANCHSHEEL HOMEOPATHIC MEDICAL
COLLEGE AND HOSPITAL KHAMGAON
D BHMS-1ST
PHYSIOLOGY – SEMINAR
PRESENTED BY :-
1)AKSA KHAN (40)
2)VRUSHALI KHARAT (41)
3) NITIN KHARSADE (42) GUIDED BY :- DR.VIPLAV KAVISHWAR SIR
4) BHAKTI KUDALE (43) ( HEAD OF PHYSIOLOGY DEPARTMENT)
DR.PRANSHANT KULKARNI SIR
( ASSISTANT PROFESSOR)

3. STRUCTURE AND FUNCTION OF
NEPHRONS
EXCREATORY SYSTEM

4. INTRODUCTION
• DEFINITION:- THE NEPHRON IS THE MINUTE OR MICROSCOPIC STRUCTURAL AND
FUNCTIONAL UNIT OF THE KIDNEY.
• THE TWO KIDNEYS ARE THE CHIEF EXCRETORY ORGAN OF THE BODY.
• NEPHROLOGY IS THE ADULT AND PEDIATRIC STUDY OF THE KIDNEYS AND ITS
DISEASES.
• EACH KIDNEY CONSISTS OF 1 TO 1.3 MILLION NEPHRONS
• THE NUMBER OF NEPHRONS STARTS DECREASING AFTER THE AGE ABOUT 45-50
YEARS AT THE RATE OF 0.8-1% PER YEAR.
• THEY PERFORM EXCRETORY AND HEMEOSTATIC FUNCTION.
• THE NEPHRONS ULTIMATELY DRAIN INTO THE PELVIS OF THE URETERS.
• FROM HERE URINE IS PASSES DOWN THE URETER AND COLLECTED IN URINARY
BLADDER.

5. PART OF NEPHRONS
EACH NEPHRON IS FROMED BY TWO PARTS:-
1. RENAL CORPUSCLE OR MALPHIGHIAN CORPUSCLE –BLIND END.
2. RENAL TUBULE-A TUBULAR PORTION.

6.  SHAPE – SPHEROIDAL AND SLIGHTLY FLATTENED.
 DIAMETER -200 Μ.
 FUNCTION- FILTRATION OF BLOOD WHICH
FORMS FIRST PHASE OF URINE FORMATION.
 SITUATION –CORTEX OF KIDNEY EITHER
CORTICAL NEPHRONS (NEAR PERIPHERY) OR
JUXTAMEDULLARY NEPHRON (NEAR MEDULLA).
RENAL CORPUSCLE

7. RENAL TUBLE
• BOWMAN’S CAPSULES
• PROXIMAL CONVOLUTED TUBULE
• LOOP OF HENLE:-
1.DESCENDING LIMB
2.HAIRPIN BEND
3.ASCENDING LIMB
• DISTAL CONVOLUTED TUBULE

8. Structure of Nephron

9. TYPE OF NEPHRONS
Histologically there are two types of nephrons',
according to theirs Relative Position in the
Cortex:-
1)CORTICAL NEPHRONS or SUPERFICIAL
NEPHEONS:
 Occupy the outer 2/3 of the cortex and make
up about 85% of total number
 Present in outer cortex near the periphery,
small in size,fully functional under normal
conditions.
It has blood supply of Peritubular capellaries
& has function of formation of urine.

10. 2) JUXTAMEDULLARY NEPHEONS :
 Occupy inner third of cortex and costitute
about 15% of total number.
 Present in inner Cortex near medulla.
 Large in size and work Only in under stress
conditions

11. The nephron consist of following parts :
1.Renal or malphighian corpuscle
2. Proximal convoluted tubule
3. Loop of Henle
4. Distal convoluted tubule
And proximal & distal straight tubule
▪️The proximal convoluted and distal convoluted tubule
are in the cortex
▪️ The loop of Henle extends from the Cortex to
variable distance in the medulla according to the
position of corpuscle in Cortex
Parts of the Nephron :

13. 🔸MALPHIGIAN COURPUSCLE
Found only in Cortex
Diameter : 200 microns
It consist of two parts:
1. GLOMERULUS
2. BOWMAN’S CAPSULE

15.  1) GLOMERULUS
 Glomerulus is the tuft of capillaries enclosed by
bowmen’s capsule.
 It consist of glomerular capillaries interposed between
afferent and efferent arterioles.
 Glomerular capillaries arises from afferent arterioles.
 After entering to bowman’s capsule the afferent
arteriole divides into 4 to 5 large capillaries each large
capillary subdivided into 20 to 50 small capillaries
arranged in irregular loop and forms an anastomosis.
 All small capillary reunite to form efferent arteriole
which is less in diameter than afferent arteriole.

16. FUNCTIONAL HISTOLOGY :-
Capillaries are made
from single layer of
endothelial cells
attached to basement
membrane.
Endothelial cells has
many pore called
fenestrae or filtration
pore

17. BOWMAN’S CAPSULES :-
It is the capsular structure encloses the
glomerulus formed by two layers:
# Inner- Visceral
# Outer-parietal

18. 1)VISCERAL LAYERS:-
 Visceral layer covers the glomerular capillaries and it
continues as the parietal layer at visceral pole .
 Each epithelial cell of visceral layer connected with
basement membrane by cytoplasmic extension called
pedicle .
 This pedicle leaves cleft like space which is called as slit
pore .
 Epithelial cell with pedicle are called as podocytes

19. TUBULAR PORTION OF NEPHRONS
 🔸 PROXIMAL CONVOLUTED TUBULE

 It is the coiled portion arising from
bowmen’s capsule .
 It is situated in cortex it is continued
as descending limb of loop of Henle.
 Length of proximal convoluted
tubule is 14 mm and diameter is 55
μ.

20. FUNCTIONAL HISTOLOGY :-
 Proximal convoluted tubule is
formed by single layer of
cuboidal epithelial cells.
 It has hair like projection
directed towards the lumen of
tubule because of this
projection the epithelial cells
are called brush border cells

21. 🔸LOOP OF HENLE
 Site for osmoregulation
 Length is 10 - 15mm and diameter of 30μ.
 Consist of:
1. Descending limb
2. Hairpin bend
3. Ascending limb

22. 1)DESCENDING LIMB
 It consist of:
A ) Thick descending segment
B )Thin descending segment
 THICK DESCENDING SEGMENT:
- It is direct communication of
proximal convoluted tubule descend down in medulla.
 It is of length 6 mm and 55 μ in diameter and form by brush
border cuboidal epithelial cells .

 THIN DESCENDING SEGMENT :-
 It is formed by flattened epithelial cell without brush border .
 it is continued as hair pin bent of the loop of Henle.



23. 2)HAIRPIN BEND:-
 Hair pin bend formed by
flattened epithelial cells without
brush border.
 It is continues as ascending limb
of loop of Henle.

24. ▪️ ASCENDING LIMB:-
It has two parts:
A)Thin ascending
segment
B)Thick ascending
segment
A)THIN ASCENDING SEGMENT:-
 It is the continuation of hair pin
bend.
It is also line by flattened epithelial
cell without brush border.

25. B)THICK ASCENDING SEGMENT
 It is about 9 mm long and diameter of 30μ.
 It is line by cuboidal epithelial cell without
brush border.
 It is continuous as convoluted tubules.
 This part of nephron runs between afferent and
efferent arterioles forms macula densa.
 Which is part of JG apparatus.

26. 🔸 DISTAL CONVOLUTED TUBULE:-
 It is the continuation of thick ascending segment
and occupies the cortex of kidney.
 It is continues as collecting duct.
 The length of distal convoluted tubule is 14.5 to 15
mm and diameter is 22 to 50μ.

FUNCTIONAL HISTOLOGY:
 Distal convolute tubule are line by single layer of
cuboidal epithelial cells without brush border cells.
 This cell in distal convoluted tubule are called
inter-related cells (I cells).

27. 🔸 COLLECTING DUCT OR STRAIGHT TUBULE :-
 Distal convoluted tubule continuous as initial or
arched collecting duct which is in Cortex.
 The lower part of collecting duct lies in medulla .
 7 to 10 initial collecting duct unite to form straight
collecting duct, which passes through medulla.
 Several collecting duct from different nephron joints
to form Duct of Bellini.
 It is 20 mm long and varies in diameter between 40
to 200 μ.

30. RENAL CIRCULATION
 INTRODUCTION:-
 Blood vessels of Kidney are highly specialized to
facilitate function of formation of urine.
 In adults in resting condition both kidneys receive
1300 ml of blood per minute or about 26 percent of
cardiac output
 Renal arteries supply blood to kidney

32. RENAL BLOOD VESSELS
1-ARTRIL SYSTEM :-
1) RENAL ARTERY:
Arises directly from abdominal arota and enters kidney through hilus
While passing through renal sinus the renal arteries divide into many segment arteries
2)SEGMENTAL ARTERY:
Subdivides into interlobular arteries one for each pyramid
3) INTERLOBAR ARTERY:
Passes between medullary pyramid. At base of pyramid it turns and
run parallel to base of pyramid forming arcuate artery

33. 4)ARCUATE ARTERY:
Gives rise to interlobular artery
5) INTERLOBULAR ARTERY:
Run through renal cortex
perpendicular to arcuate artery From each interlobular
artery numerous afferent arterioles arise

35. 6)AFFERENT ARTERIOLE:
Enters bowman’s capsule and forms glomerular capillary
tuft.
-After entering bowman’s capsule afferent arteriole divides into 4 or 5 large
capillaries Short and wide.
7) GLOMERULAR CAPILLARIES:
Each large capillary divides into small glomerular
capillaries which forms loops.
-Capillary loops unite to form efferent arterioles which leaves the bowman’s
capsules.

36.  8) EFFERENT ARTERIOLES:
Forms a second capillary
network called Peritubular capillary.
- which surrounds tubular portion of nephron Thin and
long.
- Thus renal circulation from a portal system by
presence of two sets of capillaries namely
- a)Glomerular capillaries and
- b)Peritubular capillary

37. 9)PERITUBULAR CAPILLARIES and VASA RECTA :
-Found around the tubular portion of cortical nephron
only
-Juxtamedullary nephron is supplied by some
specialized capillaries and Vasa recta
-Vasa recta arises directly from efferent arterioles of
juxtamedullary nephron and runs parallel to renal tubule
into medulla and ascend towards cortex

39. VENOUS SYSTEM
 Peritubular capillaries and Vasa recta drain
into the venous system.
 Venous system starts with peritubular
venules and continuous as interlobular vein,
arcuate vein , interlobular vein, segmental
vein and finally the renal vein.
 Renal vein leaves kidney through hilum and
joins inferior vena cava.

40. MEASUREMENT OF RENAL BLOOD FLOW
 Blood flow of kidney is
measured by using plasma
clearance of para amino
hippuric acid.

41. REGULATION OF RENAL BLOOD FLOW :
 It is mainly regulated by autoregulation
 AUTOREGULATION:
 is an intrinsic ability of an organ to regulate its own blood flow
 It is highly significant and more efficient in kidney
 It is important to maintain glomerular filtration rate (GFR)
 Blood flow to kidney is normal when mean arterial pressure is between 60-80 mmHg
 Two mechanism are involved in renal regulation
 1) Myogenic response
 2) Tubuloglomerular feedback

42.  1) MYOGENIC RESPONSE
 Increased blood flow to kidney increases the streches on the elastic
walls of afferent arterioles.
 Stretching of vessels wall increases flow of calcium ions from
extracellular fluids into cells.
 Influx of calcium ions lead to contraction of smooth muscles fibers
in afferent arterioles which causes contributions of afferent
arterioles.
 So blood flow decreases.

43. 2) TUBULOGLOMERULAR
FEEDBACK
 Macula densa plays an important role
In tubuloglomerular feedback.
 Which controls renal blood flow and
GFR.

44. PECULIARITIES OF RENAL CIRCULATION
 1) All blood that passes through kidney has to pass
through the glomerular tuft .
 Renal circulation is a portal system.
 The blood has to pass through double capillary network at
first through glomerular capillaries and then through
peritubular capillaries.
 Two capillary system serve two different functions
a) Glomerular tuft filters
b) Tubular tuft reabsorbs

45. PECULIARITIES OF RENAL CIRCULATION
2)RENAL BLOOD PRESSURE IS COMPARATIVELY HIGH
Reasons:
1)RENAL ARTERY is short and wide and arises directly from aorta it divides
into small number of wide branches .
> Because of this blood enters kidney at a comparatively high pressure
2)AFFERENT GLOMERULAR VESSELS is wider and shorter than efferent
vessel.
> Due to this glomerular pressure remains fairly high and is about 3-4
times more than capillary pressure

46.  3) THERE ARE TWO CIRCULATION IN KIDNE
a)GREATER CIRCULATION
b) LESSER CIRCULATION
 A) GREATER CIRCULATION:
 Carriers 85% of blood Blood first passes
through peritubular network and finally joins
the renal vein
PECULIARITIES OF RENAL CIRCULATION

47. 2) LESSER CIRCULATION:
 Carries 15% of blood and passes through
juxtamedullary glomeruli.
 Efferent glomerular vessels after a short
straight course ,Vasa recta ,joins the renal
directly and joins partly the peritubular
network.
 (Under abnormal conditions it may act as
shunt –trueta shunt )
PECULIARITIES OF RENAL CIRCULATION

48. LYMPHATIC SUPPLY
 Lymph drains vis thoracic ducts into venous
circulation in thorax.

49. NERVE SUPPLY
 Mainly supplies by SYMPATHETIC and PARASYMPATHETIC NERVE
FIBERS.
 SYMPATHETIC comes mainly from 10th to 12 th thoracic segments .
 PARASYMPATHETIC from vagus.
 Sympathetic carries vasoconstrictor and afferent fibers .
 Auto fibers also supply the tubular cells and reabsorption of Sodium is
probably influenced by these nerves.

50. JUXTAGLOMERULAR
APPARATUS

51. • DEFINITION:-
Juxtaglomerular apparatus is a Speciliased organ
situated near glomerulus of each Nephron.
• Juxtaglomerular apparatus is formed by three different cells-
• 1.juxtaglomerular cells
• 2. Macula densa
• 3. Extra-glomerular mesangial cells

53. JUXTAGLOMERULAR CELLS
• Juxtaglomerular cells are granular epithelial cells situated
in the Preglomerular portion of afferent and efferent
arterioles.
• These smooth muscle cells are mostly present in tunica
media and tunica adventitia of the wall of the afferent
arteriole.
• Also called as granular cell because presence of secretary
granules in their cytoplasm..

54. FUNCTIONAL KEY FEATURES OF
JUXTAGLOMERULAR APPARATUS :
1.components of GJA Related to control of blood pressure, renal blood
flow, salt balance and Erythropoiesis.
2. Renal hypertension is claimed to be cause of secretion of renin from
JGA helps in formation of Angiotensin II.
3.granulation in JG cells is related with presence of secretable renin
antibodies also localized in JG cells
4.renin secretion is determined by the sodium concentration of macula
densa cells..

55. • 5.the REF or erythrogenin is known to be secretion of JG cells. It’s
production is increase by hypoxia, cobalt salts and androgens.
• 6.cobalt salts stimulates production of erythropoietin it is known
as hormone and it’s having molecular weight of about 25,000-40,
000 causes certain stem cells in bone marrow to be converted to
proerythroblast. Blood level of erythropoietin plays imp part in
the control of erythropoiesis.

56. MACULA DENSA
• Macula densa is a modified epithelial cell in portion of
DCT lying in contact with affrent glomerular vessels of
same Nephron.
• It does not posses basement membrane..
• Macula densa cells possess golgi apparatus which lies in
between nucleus of epithelial cell and outer border of cell.
• Towards glomerular side this cell are taller and thinner.

57. EXTRA GLOMERULAR MESANGIAL CELLS
• Extracurricular mesangial cells or ‘ lacis cell ‘ is also known
as polkisson cell, goormaghtigh’s cells.
• It is a cell mass formed by mainly by the agranular or
occasional granular cells.
• These cell lie in close contact with macula densa.
• Also within the vascular pole formed by afferent and
efferent glomerular vessels..

58. APPLIED PHYSIOLOGY or CLINICAL
PHYSIOLOGY
 Renal diseases are classified in two type
 1)Acute
 2)Chronic
 *1)Acute*
 > Low blood volume
 >Exposure to kidney toxic, substances
 > obstruction of urinary tract
 *2)Chronic*
 >Diabetes mellitus – Glomerular disease.
 >Hypertension – Vascular disease
 >Glomerulonephritis (inflammation of glomeruli)
 >Anemia
 >Bone disease

59.  DIURETIC :-
 Excretion of large quantity_of water
through urine.
 such type of osmotic diuresis the diuresis which
induced by osmotic effects of solutes like glucose
 common in diabetes mellitus.
 Diuretic therapy* can provide advantageous,
effects in many clinical situation such as-
 - Heart Failure a with Edema
 - Hypertension
APPLIED PHYSIOLOGY or CLINICAL
PHYSIOLOGY

60. DIABETES MELLITUS
 A common cause of renal failure is uncontrolled diabetes
mellitus
 Diabetes meaning “running through” denotes increased urinary
volume excreted by the persons suffering with this disease.
 Diabetes can be due to:
1. Deficiency of insulin
2. Decreased responsiveness to insulin
 This abnormality in carbohydrate metabolism leads to high
levels of blood glucose which can lead to considerable damage
to many parts of the body.
 These include kidneys, heart, eyes and blood vessels.

61. Signs and symptoms of Diabetes mellitus
- 1)Frequently urination
- 2)Sudden weight loss
- 3) Always hungry
- 4) Always trusty
- 5) Wounds that won’t heal.
- 6) Blurry Vision
- 7) Numb of Thinning hand or feet
- 8)Woman get diabetes
- 9) Sexual problems.

62. GLOMERULOSCLEROSIS
 Hardening of the glomerulus of kidney due to Scarring.
 Some times diabetic nephropathy is progressive of result in
death in 2-3 years after diagnosis.
 It also leading cause of premature death In young diabetics
patient.
 Important cause of renal failure
 Also cause of nephritic syndrome in children and
adolescents.

63. DIABETES INSIPIDUS
 Cause due to failure of the posterior pituitary to
release the hormone vasopressin or inability of
the kidney to respond to vasopressin.
 In these patients kidneys are unable to conserve
water 💦
 Large quantity of dilute water is produced.
 Hence patient consume more water 💧.
 Also suffer from Dehydration.
 Also condition is called polyuria- increase
urinary outputs.

64. NEPHROGENIC DIABETES MELLITUS
 Some time ADH secretion is normal but dysfunctioning of
renal tubule
 It doesn’t give the response to ADH hormone lead to
excessive Water loss resulting in polyuria like condition
occurs.

65. BARTTER SYNDROME
 It is an genetic disorder cause due to dysfunctioning of Thick
ascending segment and Distal convoluted tubule(DCT).
 This affect on decrease reabsorption of Na,K,Cl ions.
 Resulting in loss of large quantity of Na,K,Cl ions through urine.
 Also large quantity of Ca ions is losses through urine.
COMMON SIGNS AND SYMPTOMS:-
-Muscle weakness
-Cramping
-Spasm and Fatigue
-Excessive Thirst
-Polyuria
- Nocturnal urea (may occur)

66. OLIGOURIA
 Condition in which decreased output of urine.
i.e. Less than 500ml/day.
COMMON CAUSE
1. Acute renal failure
2. Obstacles in urinary tract
3. Trauma or Infection to RENAL.
4. Heart failure
5. Dehydration
6. Medication (Such as Antibiotics,Imunosuppresent
drug and Chemotherapy).