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Ebook Handbook of neonatal intensive care (8th edition): Part 2

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(BQ) Part 2 book "Handbook of neonatal intensive care" presents the following contents: Infection and hematologic diseases of the neonate, common systemic diseases of the neonate, psychosocial aspects of neonatal care. | U FOU NIT R 20 IN C IO A DH M T L G D A S O T E N O A E FE T N N E A O O IC ISE SE F H E N T N EW BO R N H EMAT O LO GY M R Y M N O H SO , C R O E M IN E , R O D K A L V N E , A IL N A C -JO N N H IST PH R cK N Y H N A N PP-C E E G R A DJA IN OA H R Á D Z N C T . ENN E RED BLOOD CELLS Physiology R ed blood cells (R BCs) transport and deliver oxygen to vital organs and body tissues. R ed blood corpuscles are simple cells composed of a membrane encasing hemoglobin with an energy system to fuel the cells. Hemoglobin is the protein in R BCs that carries oxygen, binding and releasing it based on concentration di erences. Ex utero, R BCs absorb oxygen by diffusion in the lungs, where the oxygen tension of the alveolar air is higher than that of the capillary blood, and release it from the systemic capillaries, where the oxygen tension is now higher than that of surrounding tissues. In utero, oxygen diffuses to the fetus from the placental venous circulation. Fetal red cells contain a unique hemoglobin ( etal hemoglobin, hemoglobin F) in which the two beta chains of adult hemoglobin (hemoglobin A 1) are replaced by two gamma chains. Fetal hemoglobin has a higher a nity or oxygen than does adult hemoglobin, allowing etal red cells to compete success ully or available oxygen. Normal etal red cells are characterized by an increased mean corpuscular hemoglobin (MCH), mean corpuscular volume (MCV), hemoglobin, and hematocrit. After birth with the transition to air breathing and a higher blood oxygen tension, the hypoxic stimulus driving fetal red cell production in the bone marrow is removed. The plasma concentration of erythropoietin, the hormone that stimulates bone marrow production o R BCs, alls. The number of circulating reticulocytes, which are young R BCs in the circulation, decreases. Subsequently, the hemoglobin and hematocrit diminish until a new equilibrium is reached. Postnatal changes in red cell production include an increase in the ratio o hemoglobin A to .