Erythrocytes, or red blood cells (RBCs), are circular biconcave cells that lack organelles and are primarily responsible for oxygen transport in the body, containing hemoglobin which gives blood its red color. The production of RBCs, known as erythropoiesis, occurs mainly in the bone marrow and involves several stages of development, from committed stem cells to mature erythrocytes over approximately seven days. Key factors influencing RBC production include erythropoietin, vitamin B12, and folic acid, while the lifespan of RBCs is about 120 days, with a negative feedback mechanism maintaining their constant levels.

2. ERYTHROCYTES/RBC
•ERYTHROCYTES DERIVED FROM GREEK WORD.
•" ERYTHROS"- RED , "KYTOS"- HOLLOW VESSEL, "CYTE" - CELL
•JAN SWAMMERDAM(DUTCH BIOLOGIST AND MICROSCOPIST)
1658 , NAMED IT AS " RUDDY GLOBULES"
•RBC CONTAIN HEMOGLOBIN – GIVES RED COLOR
TO THE BLOOD
•LACKS CELL ORGANELLS LIKE RIBOSOMES,
NUCLEOLUS, MITOCHONDRIA

3. STRUCTURE
• SHAPE- CIRCULAR BICONCAVE DISCS IN ALL MAMMALS(EXCEPT
CAMELS AND IILAMAS –OVAL SHAPE)
• SPECTRIN- MAINTAINS SHAPE AND FLEXIBILITY
• SIZE- 7 MICRONS IN DIAMETER
• THICKNESS- 2 MICRONS AT PERIPHERY
AND 1 MICRONS AT CENTRE
• MAMMALIAN RBC- NON NUCLEATED
( OTHER VERTEBRATES CONTAIN NUCLEUS)

4. NORMAL COUNT
ERYTHROCYTE COUNT
NO. OF RBC PER CUBIC MILLIMETRE OF BLOOD
MALE- 4.5-6.5 MILLION/CUBIC MILLIMETRE
FEMALE- 4.5-5 MILLION / CUBIC MILLIMETRE
AT BIRTH – 6.7 MILLION/ CUBIC MILLIMETRE

5. PACKED CELL VOLUME
VOLUME OF RBC PER CUBIC MILLIMETRE OF BLOOD
40-50/CUBIC MILLIMETRE
HEMOGLOBIN
WEIGHT OF HEMOGLOBIN IN WHOLE
BLOOD MEASURED IN GRAMS/100ML
MALE: 13-18 GRAMS/100ML
FEMALE: 11.5-16.5 GRAMS/100ML

6. COMPOSITION

7. ERYTHROPOIESIS
•PROCESS OF PRODUCTION OF RBC
•INVOLVES- ORIGIN, DEVELOPMENT AND MATURATION OF RBC IN
THE BODY
SITE OF ERYTHROPOIESIS
1) 0-2 MONTHS OF INTRAUTERINE LIFE-MESENCHYMAL
CELLS OF YOLK SAC
2) 3-6 MONTHS- LIVER
3) 7- 9 MONTHS AND AFTER BIRTH- BONE MARROW

9. •RED BONE MARROW- SITE OF ERYTHROPOEISIS IN NEW BORN,
CHILDHOOD AND ADULTHOOD
•AT AGE OF 20- SHAFTS OF LONG BONES BECOME YELLOW DUE
TO FAT DEPOSIT AND BECOME UNABLE TO PRODUCE RBC
•THUS FLAT BONES- STERNUM,RIBS,VERTEBRATE, SKULL BONES
PROXIMAL END OF LONG BONES PRODUCE RBC

10. PROCESS OF ERYTHROPOIESIS

11. •COMMITED STEM CELLS THAT PRODUCE ERYTHROCYTES ARE
CALLED COLONY FORMING UNIT ERYTHROCYTE(CFU-E)
•PHSC ARE UNCOMMITED STEM CELLS WHREAS CFU-E ARE
CELLS COMMOTED TO PRODUCE RBC
•CFU-E CELLS DIVIDE INTO PROERYTHROBLAST .
•PROERYTHROBLAST DIVIDE MULTIPLE TIMES AND GIVE RISE TO
MATURE RBC

13. 1. PROERYTHROBLAST
•THESE DEVELOP FROM CFU-E
•LARGE CELL, HAVE DIAMETER OF ABOUT
20 MICRONS
• HAS NUCLEUS WITH 1/MORE NUCLEOLI
• DOES NOT CONTAIN HEMOGLOBIN
• MULTIPLIES NUMEROUS TIMES TO PRODUCE
BASOPHILIC ERYTHROBLASTS

14. 2. BASOPHILIC ERYTHROBLASTS
•DIAMETER – 15 MICRONS
•HAS NUCLEUS BUT NUCLEOLUS DISAPPEARS
•CHROMATIN NETWORK CONDENSES
•HEMOGLOBIN ABSENT
•CYTOPLASM IS BASOPHYLIC IN NATURE
( STAINS BASIC DYES))

15. 3. POLYCHROMATOPHIL ERYTHROBLAST
•DIAMETER 10-12 MICRONS
•NUCLEUS STILL PRESENT
•CHROMATIN NETWORK CONDENSES MORE
•ACCUMULATES HEMOGLOBIN
•CYTOPLASM- BASOPHYLIC .DUE TO HB IT STAINS BOTH
ACIDIC AND BASIC DYES HENS CALLED
POLYCHROMATOPHIL.

16. 4. ORTHOCHROMATIC ERYTHROBLAST
•DIAMETER 8-10 MICRONS
•BEGINNING OF THIS STAGE NUCLEUS BECOMES
EXTREMELY SMALL - 'INK NUCLEUS'
•AT THE END OF STAGE NUCLEUS DISAPPEARS
•ACCUMULATES GREATER HB SO CYTOPLASM BECOMES
MORE ACIDOPHILIC HENCE ORTHOCHROMATIC

17. 5.RETICULOCYTES
•CALLED IMMATURE RBC
•SLIGHTLY LARGE THAN IMMATURE RBC
•STAINS WITH BASIC DYES DUE TO PRESENCE OF GOLGI
APPARATUS, MITOCHONDRIA AND OTHER CELLULAR
ORGANELLES

18. 6.MATURE ERYTHROCYTES/RBC
•DIAMETER 7 MICRONS
•ATTAINS BICONCAVE SHAPE
•LACKS NUCLEUS AND OTHER OGANELLES
•IT TAKES 7 DAYS FOR THE DEVELOPMENT OF RBC FROM
PROERYTHROCYTES
•TAKES 5 DAYS UPTO THE STAGE OF RETICULOCYTES AND 2
MORE DAYS TO FORM RBC

19. FACTORS
1) ERYTHROPOIETIN( CIRCULATING HORMONE)
•PRINCIPLE STIMULUS FOR RBC PRODUCTION IN LOW OXYGEN
STATUS
•90% OF IT IS FORMED IN KIDNEY BY RENAL TUBULAR
EPITHELIAL CELLS, REMAINING FORMED IN LIVER
•STIMULATE THE PRODUCTION OF PROERYTHROBLAST FORM
HEMATOPOIETIC STEM CELLS OF BONE MARROW.

20. 2. VITAMIN B12 AND FOLIC ACID
•NECESSARY FOR THE FINAL MATURATION OF RBC
•PRESENT IN NORMAL DIET CONTAINING DAIRY PRODUCTS,
MEAT, GREEN LEAFY VEGETABLES.
DESTRUCTION OF ERYTHROCYTES
• LIFE SPAN OF RBC IS 120 DAYS
• NO. OF RBC REMAIN FAIRLY CONSTANT , THAT IS THE
BONE MARROW PRODUCES RBC AT THE RATE AT WHICH
THEY ARE DESTROYED-HOMEOSTATIC NEGATIVE
FEEDBACK MECHANISM

21. HEMOGLOBIN
• COMPLEX PROTEIN, MW-68,000
• PROTEIN PART – GLOBIN MADE UP OF
4 POLYPEPTIDE CHAINS (2 ALPHAAND 2 BETA)
• HEME PART IS PORPHYRIN MADE UP OF 4 PYROLE RING
• SYNTHESIZED INSIDE DEVELOPING ERYTHROCYTES OF RED BONE MARROW
• HB IN MATURE RBC COMBINES WITH OXYGEN – OXYHEMOGLOBIN GIVING ARTERIAL BLOOD
RED COLOR
• IN THIS WAY BULK OF OXYGEN ABSORBED FROM LUNGS TRANSPORTED AROUND THE BODY
• EACH HB CONTAINS 4 ATOMS OF IRON. EACH ATOM CAN CARRY 1 MOLECULE OF OXYGEN
THEREFORE ONE HB MOLECULE CARRIES UP TO 4 MOLECULES OF OXYGEN

22. FUNCTIONS
1. PRIMARY FUNCTION-CARRY OXYGEN FROM LUNGS TO
TISSUE AROUND THE BODY.
2.SECONDARY FUNCTION- ABILITY OF RBC TO CARRY CO2
FROM TISSUES TO LUNGS, WHERE IT CAN BE BREATHED OUT.
3.RBC CONTAIN ENZYME CARBONIC ANHYDRASE. AS CO2
ENTERS RBC , THIS ENZYME WITH THE HELP OF WATER
CONVERTS IT TO BICARBONATE WHICH IS USED TO
CONTROL PH AND EXCRETED VIA LUNGS.

23. REFERENCE
1) ANATOMY AND PHYSIOLOGY IN HEALTH AND
ILLNESS BY ROSS AND WILSON
2)ESSENTIALS OF MEDICAL PHYSIOLOGY
BY K.SEMBULINGAM
3)PHYSIOLOGYPLUS.COM
4) WWW.SLIDESHARE.COM