Development of Liver, Heart, flexor and limb buds Liver and Heart The liver and heart are the largest structures in the early embryo and form a distinctive bulge that can be seen externally. Flexures A series of three differential growth centers develop that result in several flexures along the axis of the embryo soon after […]

Development of Pharyngeal Pouches in animals The forming branchial arches encroach on the wall of the pharynx. Lateral outpouchings of the pharyngeal endoderm are formed between the branchial arches as the foregut in the pharyngeal region is compressed dorsoventrally. These are called pharyngeal pouches. Each pharyngeal pouch has specific derivatives. The lateral walls of the pharynx

Development of Brachial Region in animals Another early feature that is distinct in the head region involves the mesenchymal structure around the cranial most part of the foregut. Around this area of the foregut, the mesenchyme aggregates and proliferates to form five pairs of arch like structures lateral and ventral to the foregut. The part

Development of Trunk and Body wall in Animals The lateral folding and ventral fusion described in the formation of the sides of the head continues caudally. As the lateral folding behind the head form the cylindrical shaped embryo, it partitions a part of the coelom and part of the yolksac. These are incorporated into the

Development of Head Region in animals Neural Plate and neural groove The first indication of the formation of the head is a thickening of the ectoderm over the cranial end of the notochord. The thickening is the precursor of the brain which is referred as neural plate. The folds develop from neural plate fuse with one

Development of general body form and early features As a result of Gastrulation, the embryonic part of the gastrula consists of a flat structure in addition to the formation of three basic germ layers. The basic body pattern in adult vertebrate is found to have one tube within another, the outer being synonymous with the

Stages in Prenatal Period and Twining in Animals Stages in Prenatal Period Period of the ovum In which male and female germ meet, unite and form the zygote which develops into the blastula and gastrula covering the first 14 days of intrauterine life. Period of the embryo From end of the second week, it extends

Types of Placenta in Animals Based on Anatomical Classification The placenta is of two varieties- Deciduate and non-deciduate type. Non-deciduate further classified- Cotyledonary, Diffuse and Zonary. Deciduate Placenta in which the foetal part of the placenta is very closely associated with the maternal part and hence part of endometrium also is shed off after parturition,

Placenta of Animals Placenta is the intimate apposition or fusion of extra embryonic membranes to the maternal tissue for the physiological processes of respiration, nutrition and excretion. In addition placenta protects the embryo. Foetal membranes (or) Extra Embryonic membranes Yolk Sac The endoderm lines the inner border of the blastocyst, converting the blastocoele into the

Foetal Membranes of animals In the development of a higher vertebrate embryos like those of chick and mammals, only part of the cleavage cell mass forms the actual embryo, whereas other parts lie outside the embryonic territory and are called extra embryonic. The extra embryonic parts form foetal membranes, which are the auxiliary organs to protect the