الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
This investigation was carried out on 192 embryos, foetuses and neonatal rabbits ranging from 10 days of ‘gestation period till the 7th day after birth. The specimens used for the histological study were fixed and treated with the normal histological technique. While, the specimens used for the development of the skin blood vessels were perfused by a warm normal saline solution followed by a mixture of indian ink and rabbit serum 1:1. The skin flabs were taken from different regions of the body, as well as, the whole external ear was processed for examination under a binocular dissecting microscope which gave astereoscopic picture for the vascular bed of the skin. This study revealed that the development of the skin with its vasculature could be divided into four stages: In the first stage (First 17 da~ of foetal life), the epidermis is formed mainly of a single layer of cuboidal cells rest on a condensation of mescnohymal C.T. Later on, the epidermis shows two to three layers of cells in most of the regions of the body with the begining of the formation of hair buds in the face region. During this stage, the primordia of the hair follicles are well marked in the outer surface of lips. The blood vessels begins as an irregular islets of immature blood elements. Later on, some of blood spaces are constructed into primitive blood vessels lined with interrupted endothelium. In the second stage, (Rabbit foetuses ranging from 18—22 days, the epidermis of the skin shows a slight increase of its stratification with the disappearance of the peridermal layer with the en—out growth of epithelium demarkating the precursor of the hair follicle formation. The dermis shows the commencement of organization. The cutaneous blood vessels show a primitive pattern of distribution where the primitive arterial retae and venous plexuses were demonstrated. The satellite pattern of the skin blood vessels is seen. The epidermis of the ear shows slight stratification of the convex surface than the concave one. Also, the blood vessels of the skin of the concha auriculae exhibits the primary pattern of ramification which observe in the form of few arterial branches and three main helicine veins. In the third stage (Rabbit foetuses ranging between 23—26 day~, the keratinization of the epidermis begins with the formation of hair nodule and future dermal papilla. The keratine layer is well developed in the lips with the differentiation of the hair buds into tactile hair follicles and normal ones. The tactile hair follicles show the beginning of the hair canal formation, the hair follicle sheaths and the hair shaft not penetrate the epidermis. Also, the primordia of’ the sebaoeous gland appears at this stage and the sweat glands appeared as a consolidated masses of’ cells with cavitation The cutaneous vascular networks become more developed and exhibited a definite pattern of construction. The skin was divided into Unit vascular zones by the plexus venosus dermis profundus. Each unit vascular zone is supplied by several arterial branches of Ramus arteriosus cutaneous. The division of’ the unit vascular zones into subunit vascular zone is clearly marked. Some vessels of’ the plexus venosus dermis profundus present valves. The budding of the hair follicles in the ear concha appears in the convex surface and devoids in the concave one. The blood vessels of the skin of the ear concha show more or less a progressed pattern of distribution on both convex and concave surfaces where they are represented by U arterial rami and three helicine veins. Also the subepidermal and perichondral retae and plexuses are well formed. In the fourth stage (Rabbit foetuses ranged from 27day till the parturition), the skin is covered with thick stratified epithelium with rapid differentiation of the normal body hair follicles and their associated structures.