FOETAL PHYSIOLOGY Nutrition Fetal Blood Luecocytes and Fetal

FOETAL PHYSIOLOGY

• • Nutrition Fetal Blood Luecocytes and Fetal Defence Urinary system Skin Gastrointestinal tract Respiratory system Fetal Endocrinology

NUTRITION • There are 3 stages of fetal nutrition following fertilization. 1) Absorption 2) Histotrophic transfer 3) Haemetotrophic 2/3 of total calcium, 3/5 of total protiens and 4/5 of total iron are drained from mother during last 3 months.

FETAL BLOOD • Haematopoesis - embryonic phase is demonstrated first in yolk sac by 14 th day. - By 10 th week liver becomes the major site. - Followed by spleen and bone marrow. - Near term bone marrow becomes the major site of red cell production. • Erythropoesis is magaloblastic in early period but near term it becomes normoblastic.

At term • RBC= 5 to 6 million/cumm • Hb= 16. 5 -18. 5 gm% • Reticulocytes =5% • Erythroblast=10% -During first half, Hb is of fetal type but from 24 weeks onwards, adult type Hb apperas and at term 75 -80% of total Hb is of fetal type. -Total feto-placental blood volume at term is estimated to be 125 ml/kg BW of fetus. -Rh factor- 38 days after conception.

Luecocytes And Fetal Defence • Leucocytes appear after 2 months of gestation. Wbc count at term is 15 -20 k cumm. • Thymus and spleen produce lymphocytes, a major source of antibody formation. • Ig. G crosses placenta from 12 th week onwards to give passive immunity.

URINARY SYSTEM • By the end of first trimeter the nephrons become active and secrete urine. • Near term the urine production rises to 650 ml/day. • Kidneys are important in regulation of the compositioin and volume of the liquor amni.

SKIN • At 16 th week, lanugo appears. • At 20 th week sebaceous glands appear and sweat glands appear later. • Horny layer of the epidermis is absent before 20 th week- it favours transudation from the fetal capillaries into liquor amnii.

GIT • 10 -12 week, fetus swallows amniotic fluid. • Meconium appears from 20 th week and at term.

RESPIRATORY SYSTEM • In early months lungs are solid. • At 28 th week, alveoli expand are lined by cuboidal epithelium. • At 34 th week, lung surfactant related to phospholipids-phosphatidylcholine and phosphatidylglycerol appear. Breathing movements identified by 11 weeks irregular until 20 th week. Frequency varies from 30 -70/min.

FETAL ENDOCRINOLOGY • ACTH, GH, PRL, TSH, GH -10 th week. • Vasopressin and oxytocin- 12 th week. • Fetal pancreas secretes insulin- 12 th week, glucagon 8 th week.