Download MBBS Physiology Presentations 50 Hematology Normal Lecture Notes

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Hemoglobin Variation

Learning Objectives

Different Hemoglobin variants

Characteristics of Hemoglobin variants and Hb

Different Hemoglobin combinations
Hemoglobin Variants

Hemoglobin Variants

? There must be 2 Alpha and 2 non alpha for oxygen carrying

function, which differs at different stages of foetal and early

neonatal life

? Normal adult hemoglobin (HbA) consists of four polypeptide

chains 22

? Normally in adult blood, small quantities of two other varieties of

hemoglobins i.e. HbA2 and HbF are found.
Normal Hemoglobin Variants

Type

Embryonic

Hb

Fetal Hb

Adult Hb

Hb Gower-1

Hb F

Hb A

Hb A2

structure

22

22

22

22

Primary Hb in

Normal %

embryonic

0.5-0.8 %

96-98 %

2.0-3.0 %

life 8 wks

Normal Hemoglobin Variants

HbA (22)
96% to 98 %
This is basic form of Hb which is important in transport of gases O2 and CO2.
HbA2 (22)
After 6 months to 1 year = 02% to 03 %


Normal Hemoglobin Variants

Fetal hemoglobin (22)
- 141 amino acids
Lifespan of RBC containing HBF is decreased to 80 days only

Embryonic Hb
Hb Gower-1 (22) Primary Hb in embryonic life 8 wks
Portland-1 (22) is the -substituted counterpart of fetal HbF (22) (By 12 weeks of

gestation, embryonic Hb changes into HbF.
Hb Portland-2 (22) since it occurs only in cases of an extreme type of -thalassemia.

Importance of Fetal hemoglobin (22) in fetal life

HbF can take up large volume of oxygen at

lower PO2.


Abnormal hemoglobin Variants - Hemoglobinopathies

GLOBIN CHAINS
The genes for the synthesis of globin are present on chromosome 16 () and

chromosome 11 ().

This determines the different variants of hemoglobin (Normal and abnormal) present at

different ages.

Globin genes and hemoglobin molecules


Sickle Cell Disease (HbS)

First molecular disease to be recognized.

chains are normal and basic abnormality is in beta chain due to a point

mutation.

SICKLE CELL DISEASE

SICKLE CELL TRAIT

Homozygous -HBSS

Heterozygous - HbAS

Sickle Cell Disease

? Most common Hb variant


Sickle Cell Disease

Hb S molecules are only 20% as soluble as Hb

A in deoxygenated blood,

low oxygen tension, Hb S molecules

polymerize

causing sickle shaped RBCs

Self Assessment

Jaundice is also called as ------------------------------when serum bilirubin is above ---------------------
The baby at birth has ------------------------------------------------------------ and excessive RBCs destruction
80% of ------------------------------- is excreted in feces as ---------------------------, which gives brown color of stool and
20% through enterohepatic circulation is excreted in urine as ----------------, which gives yellow color of urine
Pre-hepatic Jaundice is caused by an increased rate of ---------------------------------------------------------------------
Physiological Jaundice in newborns occurs due to ------------------------------------------------------------------------------
Hepatic cause of physiological jaundice in newborns ------------------------------------------------------------------------------------
Kernicterus may occur in new born because ------------------------------and when ------------------------------------------


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