Egypt. J. Exp. Biol. (Zool.), 9(1): 75 – 78 (2013) © The Egyptian Society of Experimental Biology ISSN: 2090 - 0511 On Line ISSN: 2090 - 0503 http://www.egyseb.org RESEARCH ARTICLE Rafah H. Lateef HISTOLOGICAL STUDY OF UMBILICAL CORD AT DIFFERENT STAGES OF GESTATION ABSTRACT: The umbilical cord is the lifeline between the foetus and placenta. It is formed by the fifth week of development and it functions throughout pregnancy to protect the vessels that travel between the foetus and the placenta. In the present study, 60 term placenta were studied. Out of these 28 were of female and 33 of male babies from healthy looking mothers aged between 25 - 35 years and the parity from one to five. All cords obtained were of normal vaginal deliveries and aborted foetuses. For light microscopy, two cm. of tissue was taken from each cord and fixed in 10% formalin for one week. Grossly the attachments of umbilical cord to the placenta were observed which showed that the eccentric site of insertion was 64.99%, the central insertion 28.33% and the marginal insertion 6.66% from the total observed placenta. The tunica intimae consist of a single continuous wavy layer of small oval or rounded shaped, which bulges into the lumen of arteries. A thick tunica medium which contains two areas of smooth muscle fibres arrange into an inner longitudinal and an outer circular fibres, both being equal in thickness. Between the longitudinal smooth muscles, there are uniformly distributed collagen fibres. In addition there are two to eight folds called Hoboken Folds which cause irregular narrowing of the lumen; some of these folds show bifurcation. Such features of tunica media was observed at nine months umbilical cord section. The Hoboken folds not found at the sections of three and five months of umbilical cord sections. it is concluded that the measurement of thickness of muscular layer (tunica media) increased from 0.6 μ m at the third month of gestation to 9.2 μ m at ninth month (at delivery) which may be lead to increase the strength and elasticity of the cord against torsion and compression as the foetus became near the delivery time. KEY WORDS: Histology, Umbilical Cord, Different Stages of Gestation CORRESPONDENCE: Rafah Hady Lateef College of Science for Women, Babylon University, Iraq E-mail: almolaghanim@yahoo.com ARTICLE CODE: 07.01.13 INTRODUCTION: The umbilical cord is the lifeline between the foetus and placenta. It is formed by the fifth week of development and it functions throughout pregnancy to protect the vessels that travel between the foetus and the placenta. It attains more growth until 28 weeks of pregnancy reaching an average length of 55-65 cm. It is composed of three blood vessels of different structure and function, one vein, which transports oxygenated and nutrition-rich blood from placenta to foetus, and two arteries, which transport deoxygenated blood and metabolic waste products from foetus to placenta. All these vessels are surrounded by Wharton’s jelly (Kliman, 1998; Cruikshank, 2003), which constitutes the major part of human umbilical cord and provides a thick protective mantle around vessels. Wharton’s jelly plays also an important role as storage for some compounds, such as growth factors (Sobolewski et al ., 2005). The extracellular matrix (ECM) in the vascular wall contains many macromolecules (collagen, elastin, proteoglycans, and glycoproteins) necessary for the structural and functional properties of vessel wall. The epithelial covering of the umbilical cord is derived from the amniotic epithelium which covers the cord during the early development of the embryo (Lukashev and Werb, 1998). When umbilical cord reaches the foetal surface of the placenta, the blood vessels divided into many branches which enter the chorionic villi. The oxygenated blood returns to the foetus via the venules and veins in the chronic villi. These join to form the umbilical vein in the umbilical cord (Wigglesworth and Singer, 1998). Variations in the site of the insertion of umbilical cord are thought to result from the process known trophotrophism (Robinson et al., 1983) in which the chorionic frondosum or the early placenta "migrates| with advancing gestation to ensure a better blood supply from a more vascularised area (Monie,1965). The insertion of the umbilical cord to the placenta was central insertion into placenta at midgestation; insertion may become more eccentric as gestation proceeds (Morgan and Ross, 2006).