2. ANATOMY OF THE KIDNEY:
• THE KIDNEY IS AN ESSENTIAL ORGAN IN THE HUMAN BODY.
• IT IS RESPONSIBLE FOR FILTERING WASTE PRODUCTS AND EXCESS FLUIDS FROM
THE BLOOD
• IT ALSO HELPS REGULATE BLOOD PRESSURE, BALANCE ELECTROLYTES, AND
PRODUCE HORMONES THAT STIMULATE RED BLOOD CELL PRODUCTION.
Location:
It is located in the abdominal cavity or peritoneal cavity, and
each human being has two kidneys.
3. SHAPE :
• EACH KIDNEY IS BEAN-SHAPED .
SIZE :
• APPROXIMATELY 10-12 CM LONG.
• 5-7 CM WIDE. 3 CM THICK.
• THE RIGHT KIDNEY IS SLIGHTLY LOWER THAN THE LEFT DUE TO THE POSITION OF THE LIVER.
• PARTS OF KIDNEY:
• THE KIDNEY IS MADE UP OF THREE MAIN PARTS:
• RENAL CORTEX
• RENAL MEDULLA
• RENAL PELVIS
4. • RENAL CORTEX:
THE RENAL CORTEX IS THE OUTER LAYER OF THE KIDNEY.
CONTAINS MANY TINY BLOOD VESSELS, CALLED GLOMERULI, AND THE RENAL
TUBULES.
• RENAL MEDULLA:
THE RENAL MEDULLA IS THE MIDDLE LAYER OF THE KIDNEY.
CONSISTS OF CONE-SHAPED STRUCTURES CALLED RENAL PYRAMIDS.
EACH PYRAMID CONTAINS THOUSANDS OF TINY TUBES CALLED NEPHRONS.
• RENAL PELVIS:
THE RENAL PELVIS IS THE INNERMOST PART OF THE KIDNEY.
WHERE URINE IS COLLECTED AND TRANSPORTED TO THE BLADDER THROUGH A
TUBE CALLED THE URETER.
5.
6. • NEPHRONS
• THE NEPHRON IS THE FUNCTIONAL UNIT OF THE KIDNEY.
• EACH KIDNEY CONTAINS APPROXIMATELY ONE MILLION NEPHRONS.
• STRUCTURE OF THE NEPHRON:
• THE NEPHRON CONSISTS OF THE RENAL CORPUSCLE, AND THE RENAL TUBULE.
• RENAL CORPUSCLE:
• GLOMERULUS
• BOWMAN'S CAPSULE
• RENAL TUBULE:
• PROXIMAL CONVOLUTED TUBULE
• LOOP OF HENLE
• DISTAL CONVOLUTED TUBULE
• COLLECTING DUCT
7.
8. • BLOOD ENTERS THE KIDNEY THROUGH THE RENAL ARTERY AND
LEAVES THROUGH THE RENAL VEIN.
• THE RENAL ARTERY BRANCHES INTO SMALLER VESSELS,
EVENTUALLY FORMING THE AFFERENT ARTERIOLES THAT SUPPLY
THE GLOMERULI IN THE RENAL CORTEX.
• THE BLOOD THEN FLOWS THROUGH THE CAPILLARIES OF THE
GLOMERULI AND EXITS VIA THE EFFERENT ARTERIOLES.
• FROM THERE, IT TRAVELS THROUGH THE PERITUBULAR
CAPILLARIES SURROUNDING THE RENAL TUBULES BEFORE
ENTERING THE RENAL VEIN.
9. FORMATION OF URINE :
• URINE IS FORMED BY THE KIDNEYS THROUGH A COMPLEX PROCESS CALLED URINE
FORMATION OR URINARY SYSTEM FUNCTION.
• THE PROCESS INVOLVES THE FILTRATION OF BLOOD, SELECTIVE REABSORPTION OF
USEFUL SUBSTANCES, AND SECRETION OF WASTE PRODUCTS.
• THE FOLLOWING ARE THE STEPS INVOLVED IN URINE FORMATION:
• FILTRATION
• REABSORPTION
• CONCENTRATION OF URINE
• SECRETION OF URINE
• EXCRETION OF URINE
10. • FILTRATION:
• FILTRATION OF URINE IS THE PROCESS BY WHICH THE KIDNEYS REMOVE WASTE
AND EXCESS FLUIDS FROM THE BLOOD, PRODUCING URINE AS A RESULT.
• THE PROCESS OF FILTRATION TAKES PLACE IN THE RENAL CORPUSCLE, WHICH
CONSISTS OF THE GLOMERULUS AND BOWMAN’S CAPSULE.
• ULTRAFILTRATION:
• AS BLOOD FLOWS THROUGH THE GLOMERULUS, WATER, SALTS, AND OTHER
SMALL MOLECULES ARE FORCED OUT OF THE CAPILLARIES AND INTO BOWMAN’S
CAPSULE BY A PROCESS CALLED ULTRAFILTRATION.
• THIS PROCESS IS DRIVEN BY THE PRESSURE OF THE BLOOD FLOWING THROUGH
THE GLOMERULUS AND THE UNIQUE STRUCTURE OF THE GLOMERULAR
FILTRATION BARRIER, WHICH PREVENTS LARGER MOLECULES LIKE PROTEINS
FROM PASSING THROUGH.
11. GROMETULUS FILTRATE:
• AS BLOOD FLOWS THROUGH THE GLOMERULUS, SMALL MOLECULES SUCH AS
WATER, ELECTROLYTES, AND WASTE PRODUCTS ARE FILTERED OUT OF THE
BLOOD AND INTO BOWMAN'S CAPSULE.
• ONCE THE FILTRATE ENTERS BOWMAN'S CAPSULE, IT IS CONSIDERED TO BE
URINE.
12. • THE URINE THEN TRAVELS THROUGH THE NEPHRON,
WHERE IT IS FURTHER PROCESSED AND MODIFIED BY
PROCESSES LIKE REABSORPTION AND SECRETION.
ULTIMATELY, THE URINE IS COLLECTED IN THE BLADDER
AND ELIMINATED FROM THE BODY THROUGH THE
URETHRA.
13. • REABSORPTION:
• REABSORPTION OF URINE IS THE PROCESS BY WHICH THE BODY REABSORBS
WATER AND OTHER USEFUL SUBSTANCES FROM THE URINE BEFORE IT IS
EXCRETED.
• THE BODY NEEDS TO MAINTAIN A DELICATE BALANCE OF FLUIDS AND
ELECTROLYTES TO FUNCTION PROPERLY, SO THE KIDNEYS HAVE TO REABSORB
SOME OF THE FILTERED SUBSTANCES BACK INTO THE BLOODSTREAM.
• THE PROCESS OF REABSORPTION OCCURS PRIMARILY IN THE RENAL TUBULES,
WHICH ARE SMALL, TUBE-LIKE STRUCTURES IN THE KIDNEYS.
14. • AS URINE FLOWS THROUGH THE TUBULES, VARIOUS SUBSTANCES ARE
SELECTIVELY REABSORBED BASED ON THEIR CONCENTRATION GRADIENT AND
THE NEEDS OF THE BODY.
• FOR EXAMPLE:
• WATER IS REABSORBED IN LARGE AMOUNTS BECAUSE IT IS ESSENTIAL FOR
MAINTAINING PROPER HYDRATION LEVELS IN THE BODY.
15. • OTHER SUBSTANCES THAT ARE COMMONLY REABSORBED INCLUDE GLUCOSE,
AMINO ACIDS, AND ELECTROLYTES SUCH AS SODIUM, POTASSIUM, AND
CHLORIDE.
• THE REABSORPTION OF THESE SUBSTANCES IS REGULATED BY VARIOUS
HORMONES AND FEEDBACK MECHANISMS IN THE BODY.
• OVERALL, REABSORPTION OF URINE PLAYS A CRITICAL ROLE IN MAINTAINING
FLUID AND ELECTROLYTE BALANCE IN THE BODY AND ENSURING PROPER
KIDNEY FUNCTION.
16. PROXIMAL CONVOLUTED TUBULE (PCT) :
• THE PCT IS LINED WITH SPECIALIZED CELLS CALLED EPITHELIAL CELLS.
• EPITHELIAL CELLS:
• THEY HAVE MICROVILLI ON THEIR SURFACE THAT INCREASE THEIR SURFACE
AREA FOR ABSORPTION.
• THESE CELLS ARE RESPONSIBLE FOR REABSORBING MOST OF THE FILTERED
WATER AND ESSENTIAL SOLUTES, SUCH AS:
• GLUCOSE
• AMINO ACIDS
• ELECTROLYTES BACK INTO THE BLOODSTREAM.
17. • IN ADDITION TO REABSORPTION, THE PCT ALSO PLAYS A ROLE IN THE
SECRETION OF WASTE PRODUCTS, SUCH AS :
• DRUGS AND TOXINS,
• FROM THE BLOODSTREAM INTO THE TUBULAR FLUID.
• THIS PROCESS IS IMPORTANT FOR REMOVING HARMFUL SUBSTANCES FROM THE
BODY AND MAINTAINING OVERALL HEALTH.
18.
19. LOOP OF HENLE:
• THE LOOP OF HENLE IS A PART OF THE KIDNEY’S NEPHRON RESPONSIBLE FOR
PRODUCING CONCENTRATED URINE AND MAINTAINING THE BODY’S WATER
BALANCE.
• THE LOOP OF HENLE IS DIVIDED INTO THREE SEGMENTS:
• THE THIN DESCENDING LIMB
• THE THIN ASCENDING LIMB
• THE THICK ASCENDING LIMB
20. THE THIN DESCENDING LIMB :
• IT IS PERMEABLE TO WATER, BUT NOT TO SOLUTES, AND WATER MOVES OUT OF
IT PASSIVELY INTO THE SURROUNDING MEDULLARY INTERSTITIUM, MAKING THE
TUBULAR FLUID MORE CONCENTRATED.
21. THE THIN ASCENDING LIMB :
• IT IS PERMEABLE TO SOLUTES, BUT NOT TO WATER, AND IT ACTIVELY PUMPS
OUT IONS SUCH AS SODIUM, CHLORIDE, AND POTASSIUM, FURTHER
CONTRIBUTING TO THE CONCENTRATION OF THE TUBULAR FLUID.
22. THE THICK ASCENDING LIMB :
• IT IS ALSO PERMEABLE TO SOLUTES, AND IT ACTIVELY REABSORBS SODIUM AND
CHLORIDE IONS, BUT IS IMPERMEABLE TO WATER.
23. DISTAL CONVOLUTED TUBULE (DCT) :
• IT IS RESPONSIBLE FOR FINE-TUNING THE REABSORPTION AND SECRETION OF
IONS AND WATER IN THE URINE, THEREBY REGULATING THE BODY'S
ELECTROLYTE BALANCE AND FLUID VOLUME.
• IN THE DCT, SODIUM, CHLORIDE, AND CALCIUM IONS ARE ACTIVELY
REABSORBED FROM THE FILTRATE AND TRANSPORTED BACK INTO THE
BLOODSTREAM.
• POTASSIUM AND HYDROGEN IONS ARE SECRETED INTO THE FILTRATE.
24. • THIS PROCESS IS REGULATED BY SEVERAL HORMONES INCLUDING :
• ALDOSTERONE, WHICH PROMOTES SODIUM REABSORPTION AND POTASSIUM
SECRETION.
• PARATHYROID HORMONE, WHICH STIMULATES CALCIUM REABSORPTION.
25. • ADDITIONALLY, IT IS INVOLVED IN THE PROCESS OF URINE CONCENTRATION
AND DILUTION BY RESPONDING TO THE HORMONE VASOPRESSIN, WHICH
REGULATES WATER REABSORPTION IN THE COLLECTING DUCTS.
26. COLLECTING DUCT :
• THE FINAL STEP IN URINE FORMATION TAKES PLACE IN THE COLLECTING DUCT.
• IT IS RESPONSIBLE FOR THE FINAL CONCENTRATION OR DILUTION OF URINE,
AND PLAYS A CRUCIAL ROLE IN MAINTAINING THE BODY’S WATER AND
ELECTROLYTE BALANCE.
27. REGULATION:
• THE COLLECTING DUCT IS REGULATED BY HORMONES SUCH AS ANTIDIURETIC
HORMONE (ADH) AND ALDOSTERONE.
• WHICH CAN INCREASE OR DECREASE WATER AND ELECTROLYTE REABSORPTION,
DEPENDING ON THE BODY’S NEEDS.
• ADH INCREASES THE PERMEABILITY OF THE COLLECTING DUCT TO WATER,
ALLOWING MORE WATER TO BE REABSORBED AND PRODUCING A MORE
CONCENTRATED URINE.
28. • ALDOSTERONE, ON THE OTHER HAND, INCREASES SODIUM REABSORPTION AND
POTASSIUM SECRETION, WHICH CAN ALSO AFFECT WATER REABSORPTION.
• IN ADDITION TO REGULATING WATER AND ELECTROLYTE BALANCE.
• THE COLLECTING DUCT ALSO PLAYS A ROLE IN ACID-BASE BALANCE BY
SECRETING HYDROGEN IONS AND REABSORBING BICARBONATE IONS.
• OVERALL, THE COLLECTING DUCT IS AN IMPORTANT COMPONENT OF THE
KIDNEY’S FILTRATION AND REABSORPTION SYSTEM, HELPING TO MAINTAIN THE
BODY’S INTERNAL ENVIRONMENT WITHIN A NARROW RANGE OF PARAMETERS.
29. • SECRETION OF URINE:
• THE PROCESS OF URINE SECRETION BEGINS WITH THE FILTRATION OF BLOOD IN
THE KIDNEYS.
• BLOOD ENTERS THE KIDNEYS THROUGH THE RENAL ARTERY, WHICH BRANCHES
OUT INTO SMALLER AND SMALLER VESSELS UNTIL IT REACHES THE TINY
FILTERING UNITS OF THE KIDNEY CALLED NEPHRONS.
• EACH NEPHRON CONSISTS OF A FILTERING UNIT CALLED THE GLOMERULUS AND
A TUBULE THAT COLLECTS THE FILTERED FLUID.
30. • AS BLOOD PASSES THROUGH THE GLOMERULUS, WASTE PRODUCTS, SUCH AS
UREA AND CREATININE, ALONG WITH EXCESS WATER AND ELECTROLYTES, ARE
FILTERED OUT OF THE BLOOD AND INTO THE TUBULE.
• THIS FILTERED FLUID IS KNOWN AS THE GLOMERULAR FILTRATE.
31. • THE NEXT STEP IN URINE SECRETION IS TUBULAR
REABSORPTION, WHERE MOST OF THE WATER,
ELECTROLYTES, AND NUTRIENTS THAT WERE FILTERED OUT
OF THE BLOOD ARE REABSORBED BACK INTO THE BODY
THROUGH THE WALLS OF THE TUBULES.
• THIS PROCESS HELPS TO MAINTAIN THE BALANCE OF
FLUIDS AND ELECTROLYTES IN THE BODY.
32. • THE FINAL STEP IN URINE SECRETION IS TUBULAR SECRETION,
WHERE THE REMAINING WASTE PRODUCTS, SUCH AS EXCESS
POTASSIUM, HYDROGEN IONS, AND DRUGS, ARE ACTIVELY
SECRETED INTO THE TUBULES. THIS PROCESS HELPS TO ELIMINATE
THESE WASTE PRODUCTS FROM THE BODY.
33. • ONCE THE URINE IS FORMED, IT TRAVELS THROUGH THE URETERS,
TWO THIN TUBES THAT CONNECT THE KIDNEYS TO THE BLADDER.
THE BLADDER STORES URINE UNTIL IT IS FULL, AND THEN THE
URINE IS EXPELLED FROM THE BODY THROUGH THE URETHRA
DURING URINATION.
34. • CONCENTRATION OF URINE :
• CONCENTRATION OF URINE REFERS TO THE PROCESS BY WHICH THE KIDNEYS
REMOVE EXCESS WATER AND SOLUTES FROM THE BLOOD AND PRODUCE A
SMALLER VOLUME OF MORE CONCENTRATED URINE.
• THIS PROCESS IS ESSENTIAL FOR MAINTAINING THE BODY’S FLUID BALANCE AND
ELECTROLYTE LEVELS.
• THE CONCENTRATION OF URINE IS REGULATED BY THE HORMONE ANTIDIURETIC
HORMONE (ADH), ALSO KNOWN AS VASOPRESSIN.
35. • ADH IS PRODUCED IN THE HYPOTHALAMUS OF THE BRAIN AND RELEASED FROM
THE PITUITARY GLAND IN RESPONSE TO CHANGES IN THE BODY'S FLUID
BALANCE.
• WHEN THE BODY NEEDS TO CONSERVE WATER, SUCH AS DURING
DEHYDRATION, ADH LEVELS INCREASE AND THE KIDNEYS RESPOND BY
REABSORBING MORE WATER FROM THE URINE, RESULTING IN A MORE
CONCENTRATED URINE OUTPUT.
• CONVERSELY, WHEN THE BODY NEEDS TO ELIMINATE EXCESS WATER, SUCH AS
DURING OVER HYDRATION, ADH LEVELS DECREASE AND THE KIDNEYS PRODUCE
A MORE DILUTE URINE.
36. • EXCRETION OF URINE :
• FINALLY, THE URINE IS COLLECTED IN THE BLADDER AND EXCRETED FROM THE BODY THROUGH THE
URETHRA DURING URINATION.
• THE AMOUNT AND COMPOSITION OF URINE EXCRETED BY THE BODY CAN VARY DEPENDING ON
FACTORS SUCH AS:
• FLUID INTAKE
• DIET
• EXERCISE
• OVERALL HEALTH
• IN GENERAL:
HEALTHY ADULTS EXCRETE 800 TO 2,000 MILLILITERS (27 TO 68 OUNCES) OF URINE
PER DAY, DEPENDING ON THEIR BODY SIZE AND ACTIVITY LEVEL.
37. • THE EXCRETION OF URINE PLAYS A VITAL ROLE IN MAINTAINING THE BODY'S
FLUID AND ELECTROLYTE BALANCE, AS WELL AS ELIMINATING WASTE PRODUCTS
SUCH AS:
• UREA, CREATININE, AND URIC ACID.
• DYSFUNCTION OF THE URINARY SYSTEM, SUCH AS:
• URINARY TRACT INFECTIONS,
• KIDNEY DISEASE, OR BLADDER PROBLEMS, CAN INTERFERE WITH THE PROPER
EXCRETION OF URINE AND LEAD TO HEALTH PROBLEMS.
38. CONCLUSION
• IN CONCLUSION, THE KIDNEY IS A COMPLEX
ORGAN THAT PLAYS A CRITICAL ROLE IN
MAINTAINING HOMEOSTASIS IN THE BODY.
