2. Renal system

3. function of the kidney

4. function of the kidney :
Formation of urine .
1- Role in homeostasis:
Primary function of kidneys is homeostasis such as :
Excretion of waste products
Urea,Uric acid,Creatinine andBilirubin
Maintain water balance
*conserving water when =decreased
*Excreting water when = excess in the body
Maintain electrolytes (Na)
Especially sodium is in relation to water
balance
Maintain acid-base balance
PH in the blood and body fluid maintained in normal range

5. function of the kidney :
2- Hemopoeitic function:
secrete erythropoeitin for erythrocytes
-secrete thrompopoeitin for thrombocytes
3-Endocrine function:
erythropoeitin, thrompopoeitin, renin
4-Regulation of blood pressure
Regulating ECF(extracellular fluid ) volume
Renin –angiotensin mechanism
5- Regulation of blood calcium level
activate vitamin D necessary for absorption of calcium from intestine to blood.

6. NEPHRON

7. 1- renal corpuscle It is structural and functional unit of kidney.
Nephron
It is structural and functional unit of kidney.
Types of nephron:
1- cortical nephron: in outer cortex
2- juxtamedullary nephron: inner cortex
Each nephron is formed from:
1- renal corpuscle
The function of renal corpuscle is filtration of blood  first phase of urine formation
2- renal tubule

9. Structure of Renal corpuscle Two portions:
1- glomerulus
Tuft of capillaries enclosed by Bowman capsule
These capillaries are disposed between afferent arteriole and efferent arteriole
2- Bowman capsule
Is like a funnel with filter paper
Is formed by two layer:
The inner  visceral layer
The outer  parietal layer

11. Renal tubule Is the continuation of Bowman capsule
Consists of 3 part :
-proximal convoluted tubule (PCT)
-loop of Henel: Descending limb, Hairpin bend, Ascending limb
-Distal convoluted tubule (DCT)

12. Juxtaglomerular apparatus
organ situated near glomerulus of each nephrone
3 structures:
1 macula densa
2 extraglomerular
mesangial cell
3 juxtaglomerular cells
Function :
Primary function is
secretion of hormonal sub
1- secretion of renin
2- secretion of other
substances (PGs)
3- regulation of GBF
and GFR

13. Renin- angiotensin system
Renin released into the blood
Angiotensinogen renin angiotensin I ACE(lung) angiotensin II angiotensinase(RBCs) angiotensin III
Functions of Angiotensin II:
Increase blood pressure by vasoconstriction
Stimulate adrenal cortex to secrete aldosterone
Regulate glomerular filtration
Increase water intake by stimulating the thirst center
Increase secretion antidiuretic hormone from hypothalamus

15. Renal circulation Renal blood vessels
Renal artery from abdominal aorta and enter the kidney through the hilus
Regulation of renal blood flow:
By Autoregulation.
Autoregulation :
The ability of an organ to regulate its own blood flow
Present in some vital organs in the body such as brain, heart and kidneys
1- Myogenic response
2- tubuloglomerular
feedback

16. URINE FORMATION

17. Urine formation Introduction :
Urine formation is a blood cleansing function.
Normally about 26% of cardiac output enters the kidneys to get rid of unwanted substances
Kidneys excrete the unwanted substances in urine
Normally about 1 to 1.5 L( ml) of urine is formed every day
The mechanism of urine formation includes three processes :
Glomerular filtration
Tubular reabsorption
Tubular secretion

19. Mechanism of Urine formation
I-Glomerular filteration:
Definition
Glomerular filtration is the process by which the blood that passes through glomerular capillaries is filtered through the filtration membrane
Filteration membrane:
Formed by 3 layer :
Glomerular capillary membrane
Basement membrane
Visceral layer of bowman capsule

22. Process of glomerular filtration :
All substances of plasma even the minute particles are filtered except plasma proteins due to their large molecular size (ultrafilteration).
The filtered fluid is called glomerular filtrate
The glomerular filtrate contain all the substance of plasma except the Plasma proteins
Glomerular filtration rate (GFR)
Total quantity of filtrate formed in all nephrons of both kidneys in the given unit of time
The normal (GFR) (125mL/min)or (180 L/ day)
Filteration fraction:
Is the fraction (portion) of the renal plasma which becomes the filtrate
It is the ratio between renal plasma flow and glomerular filtration rate
It is expressed in percentage = GFR/RPF X 100

23. Factors affecting GFR 1-renal blood flow (RBF):
It is the most important factor for glomerular filtration
2-Tubuloglomerular feedback:
Is the mechanism that regulate GFR
3-Glomerular capillary pressure:
Pressure exerted by blood in glomerular capillary
4-Colloidal osmotic pressure:
Pressure exerted by plasma protein in the glomeruli
5-Hydrostatic pressure in bowman capsule:
Pressure exerted by filterate in Bowman capsule
6-Constriction of afferent & efferent arteriole:
The Constriction of afferent arteriole reduces the blood flow to the glomerular capillary .
If efferent arteriole is constricted, the GFR increases because of stagnation of blood in the capillaries.

24. 7-Systemic arterial pressure: 8-Sympathetic stimulation:
afferent & efferent arteriole are supplied by sympathetic nerves.
Strong sympathetic stimulation cause sever constriction of the blood vessels
9-Surface area of capillary membrane:
10-Permeability of capillary membrane:
11-Hormonal:
increase GFR by vasodilatation: prostaglandin (PGE2)
decrease GFR by vasoconstriction: (Angiotensin II)

25. II- Tubular reabsorption 2- passive reabsorption
Definition
Tubular reabsorption is the process by which water and other substances are transported from renal tubules back to the blood .
Selective reabsorption
Essential substances such as glucose , amino acids and vitamins .
Substances like metabolic waste products are excreted through urine.
Mechanism:
2- passive reabsorption
1- active reabsorption
Is the movement of molecules along the electrochemical gradient .
does not need energy .
substances reabsorbed  urea, water
Is the movement of molecules against the electrochemical gradient .
it needs energy (ATP)
substances reabsorbed  sodium, calcium ,potassium

26. Regulation of tubular reabsorption:
1-Glomerulotubular balance
Is the balance between the filtration and reabsorption of solutes and water in kidney.
2-Hormonal factor
Which regulate GFR.
Aldosterone
Angiotensin ll
Antidiuretic hormone
3-nervous factor
Activation of sympathetic nervous system increase the tubular reabsorption
Transport maximum (Tm) value:
The rate at which a substance is reabsorbed from the renal tubule.
375mg/min for males
300mg/ min for females

27. Reabsorption of important substances:
sodium:
99% reabsorbed
water:
from proximal convoluted tubule (PCT): obligatory water reabsortption
from distal convoluted tubule and collecting duct (DCT): facultative water reabsorption
glucose:
Is completely reabsorbed in the proximal convoluted tubule
Renal threshold for glucose:
Is 180mg/dl in venous blood .
When blood level for glucose reaches 180 mg/dL, glucose is not reabsorbed completely and appear in urine.
bicarbonate :
mostly in proximal tubule in the form of CO2

29. III- tubular secretion
Is the process by which the substance are transported from blood into renal tubules
Substances secreted in renal tubules :
Potassium
Ammonia
Hydrogen ions

30. Concentration & Dilution of urine

31. Concentration of urine
Osmolarity of glomerular filtrate is same as that of plasma and it is 300 mOsm/L.
Normally urine is concentrated and its osmolarity is 4 times more than that of plasma mOsm/L.
Depends on two factors:
Water content in the body.
Antiduiretic hormone .
When the water content in body decreases kidney retains water and excretes concentrated urine
Formation of concentrated by
Secretion of ADH

33. Formation of dilute urine
If water content in the body is more , kidney excretes excess water making the urine dilute .
ADH increases the water reabsorption from renal tubule and collecting duct resulting in concentration of urine .
When the volume of body fluid increases or the osmolarity of body fluid decreases ,ADH secretion stops so water reabsorption from renal tubules dose not take place
Leads to excretion of large amount of water urine making the urine dilute

34. Role of ADH The final concentrated of urine is achieved by ADH
Normally the distal convoluted tubule and the collecting duct are not permeable to water .
In the prescence of ADH distal convoluted tubule and the collecting duct become permeable to water resulting reabsorption
The water reabsorption induced by ADH is called facultative reabsorption of water .

35. Role of kidney in acid-base balance
Kidneys play important role in maintenance of acid- base balance by:
excreting hydrogen ions
retaining bicarbonate ions.
Normally urine is acidic in nature with pH of 4.5 to 6
The metabolic activities in the body produce lot of acids (with hydrogen ions) which threaten to push the body towards acidosis .
Kidney prevent this by excreting hydrogen ions and conserving bicarbonate ions.

36. micturition Filling of urinary bladder: cystometrogram Definition
Is a process by which urine is voided from the urinary bladder it is a reflex process
Filling of urinary bladder:
A reasonable volume of urine can be stored in urinary bladder without any discomfort and without much increase in pressure inside the bladder
It is due to the adaptation of detrusor muscle
The relationship between the volume of urine and pressure in urinary bladder is studied by cystometrogram
cystometrogram
Defintion :
Cystometrogram is the graphical registration of pressure change in urinary bladder in relation to volume of urine collected in it .

37. Micturition reflex It is the reflex by which Micturition occurs
This reflex is elicited by the stimulation of stretch receptors situated on the wall of urinary bladder and urethra.
When about 300 to 400ml of urine is collected in the bladder the pressure inside the bladder increases
This stretches the wall of bladder resulting in stimulation of stretch receptors and generation of sensory impulses .

38. Thank you

39. MCQ

40. Choose the correct answer:
1- kidney function concerned with homeostasis such as:
Maintenence of water balance
Maintenence of electrolyte balance
Maintenence of acid-base balance
All of the above
2- The hormones secreted by the kidney:
Erythropoietin
Thrombopoietin
Rennin
3- the function of renal corpuscle:
Secretion of hormones
Regulattion of blood pressure
Filtration of blood
None of the above
4- The hormone which is secreted by juxtaglomerular apparatus is:
Renin
Antidiuretic hormone
Aldosterone hormone
calcitonin

41. 5- Hormones which regulate GFR are:
Aldosterone
Angiotensin II
Antidiuretic hormone
All of the above
6- the important role of renin-angiotensin system is:
Maintenance of water balance
Maintenance of body temperature
Maintenance of electrolyte balance
Maintenance of blood pressure
7- the pressure exerted by plasma proteins in the glomeruli is called:
Glomerular capillary pressure
Colloidal osmotic pressure
Hydrostatic pressure in Bowman`s capsule
Systemic blood pressure
8- Important substances for reabsorption are:
Water
Glucose
Sodium

42. 9- the most important factor affecting GFR is:
Tubuloglomerular feedback
Renal blood flow
Constriction of afferent arteriole
Sympathetic stimulation
10- mechanism of tubular reabsorption:
By active reabsorption
By passive reabsorption
By endocytosis
A and b
11- substances secreted in different segments of renal tubules are:
Potassuim
Ammonia
Hydrogen ions
All of the above
12- the final concentration of urine is achieved by:
ADH
Aldosterone
Angiotensin I
parothormone

43. 13- kidney regulate acid-base balance by:
Excrete hydrogen ions
Retaining bicarbonate ions
Retaining hydrogen ions
A and b
Fill in the bLank:
The structural and functional unit of kidney is ………………… which is formed by two parts:1- …………… 2-………………
Nephrons are classified into two types:1-…………… 2-……………….
Kidney secrete …………….. which important for erythropoiesis and ………………. for production of thrompocytes.
The mechanism of urine formation includes three processes:
1-……….……………………2-…..………………….. 3-…………………………
Renal blood flow is regulated by ………………….. which involve two mechanisms:1-…………………………………… 2- ………………………………..
Glomerular filteration rate(GFR) is defined as …………………… . ……………..Normal GFR is …………………….
The final concentration of urine is achieved by ………………….. homrone
kidney maintains acid-base balance by……………………… and…………………