The main functions of the male and female reproductive systems include the production of gametes, secretion of sex hormones (e.g....

The main functions of the male and female reproductive systems include the production of gametes, secretion of sex hormones (e.g....

Organs of Special Sense are organs specialized in perceiving sensory information. They include the eyes, ears, the nose and the tongue....

Organs of Special Sense are organs specialized in perceiving sensory information. They include the eyes, ears, the nose and the tongue....

The nervous system is the body’s communication network that controls the bodies functions by receiving and sending messages. It has two...

The integumentary system is made of the skin and associated glands, hair follicles, and nails. The skin is largest organ of the body...

The endocrine system is a system that functions in hormone synthesis and secretion. It consists of hormone producing endocrine cells...

The urinary system, the genital system and the female genital system have a common developmental primordium and common early...

The cardiovascular system consists of the heart, blood vessels and lymphatic vessels. The heart is a central pump that pushes blood into...

The musculoskeletal system provides movement, support, protection, and stability to the body and its organs. Development of the...

The respiratory system has several parts which develop independent of each other. The nose and nasal cavity develop from the head...

The development of the digestive system involves the formation of the gastrointestinal tract and the associated organs, namely the liver,...

In the previous chapter we have seen how the embryonic disc transformed into a bilaminar disc as a result of the development of the...

The third week of embryonic development is featured by cells of the bilaminar embryonic disk – made of an epiblast and a hypoblast-...

The process of implantations begins in the first week on the 5th or 6th week and finishes in the second on the 11th or 12th day. The polar trophoblastic cells overlying the inner cell mass come in contact with the uterine epithelium and produce enzymes that erode the epithelial lining. In the second week of embryonic development, the process of implantation progresses and several crucial events that lay the foundation for the embryonic development take place. The blastocyst c

The first week of development coincides with the third week of pregnancy. Pregnancy is dated from the day of the last period (menses) of a woman. Ovulation takes place approximately two weeks after the last menses, i.e. in the 3rd week of pregnancy’ to be followed by cleavage and subsequent stages of the embryonic development. During the first two weeks of pregnancy there is no developing embryo, but a cohort of ovarian follicles are growing under the influence of FSH in prep

These are also known as congenital disorders, congenital malformations or birth defects. They develop prenatally during embryonic development and may be identified before or after birth. They could be structural anomalies or functional abnormalities. Structural anomalies includes anomalies such as cleft lip, open neural tube and heart defects. Functional anomalies include conditions such as phenylketonuria. Congenital anomalies are caused by several factors which are classifi

The Fetal Membranes The fetal membranes, which are also known as the extraembryonic membranes, are membranous structures associated with the developing embryo and fetus; they protect and nourish the embryo and the fetus during their development within the uterus. They are four in number including the amnion, the yolk sac, the chorion, and the allantois. They are made of somatopleure and splanchnopleure. Somatopleure is formed by the fusion of the extraembryonic ectoderm and t

Fertilization is the fusion or union of the male and female gametes - the sperm and the egg - to form a zygote. It is a union of two haploid (1N) cells to give rise to a diploid (2N) cell known as the zygote. It is the starting point for the development of an embryo, and subsequently a fully formed human. The normal site of fertilization is the ampulla of the fallopian tube (oviduct). Both the sperm and the oocyte are produced at places far away from this site of fertilizatio

Gametogenesis is the process of formation of the male and female gametes i.e. the formation of the sperms and ova. It is a process whereby diploid mother sex cells yield haploid gametes with characteristic features. The process involves two different types of cell division, namely mitosis and meiosis in addition to differentiation and change in the cell shape. Formation of the male gamete (sperm) is called spermatogenesis, whereas formation of the female gamete (ovum) is know