Animal Reproduction and Embryogenesis

Spontaneous miscarriage is the spontaneous end of a pregnancy at a stage where the fetus is incapable of surviving independently. It can happen before the 20^th week of pregnancy.

Oral contraceptives contain synthetic hormones. They contain both estrogen and progestin and mainly work by preventing ovulation and by making the lining of the uterus thinner. Hormonal contraceptives are best avoided in case of heart patients.

Cephalocaudal development in an infant characterises development as starting with the head and brain areas and moving downwards. He gains control of his head movement, then neck, shoulders, back, hips, legs and feet.

This period of development starts during the ninth week and lasts until birth. The early body systems and structures formed in the embryonic stage continue to develop. In this stage the neural tube develops into the brain and spinal cord. In this stage all the organs of the fetus predicate their specialised functions.

An embryo is a multicellular diploid structure in its earliest stage of development, from the time of the first cell division until birth. The internal cluster of cells forming the blastocyst later forms an embryo.

A spermatozoon is a motile sperm cell or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. In mammals, the sex of the offspring is determined by the sperm cell: a spermatozoon bearing a Y chromosome will lead to a male (XY) offspring, while one bearing an X chromosome will lead to a female (XX) offspring.

It is the lining of the inside of the uterus. During the follicular phase of the menstrual cycle, the endometrium thickens in preparation to accept an embryo should conception occur. In a female, during the pregnancy, the blastocyst digests its way through the endometrium.

On the superior end of the labia minora is a small mass of erectile tissue known as the clitoris that contains many nerve endings for sensing sexual pleasure.

The tunica vaginalis is the serous covering of the testes. 

It is the prenatal stage that begins at conception and lasts through the second week.  In this stage zygote begins to have cell reproduction. Consequently, the zygote becomes a multi celled ball that attaches itself to the wall of the uterus of the mother.

The secretion of this gland is more serous in dogs and more mucous in bulls. It serves to promote the movement of spermatozoa in all the mammals and to form a vaginal plug.

Quickening is the early signs of the foetus movements during pregnancy. 

The process of organogenesis takes place in the embryonic period. The formation of the nasal structure is a part of organogenesis and thus occurs in embryonic period.

In 1909, Richard Richter developed the first intrauterine device made from silkworm gut.

An intrauterine device is a small contraceptive device, often 'T'-shaped and containing either copper or levonorgestrel, which is inserted into the uterus.

The raphe is the visible ridge between the lateral halves of the penis.

Basal cells are the shorter, pyramid-shaped cells which contact the basal lamina but taper off before their apical surfaces reach the lumen.

A genetic disorder is an illness caused by abnormalities in genes or chromosomes, especially before birth. To know the genetic causes of a variety of such diseases and for performing such tests, one needs fetal cells and these cells are obtained by invasive methods like aminocentesis, etc.

Dysgerminomas produce placental alkaline phosphatase and lactate dehydrogenase, so their level rises. Serum lactate dehydrogenase is most often measured to check for tissue damage.

The ampulla is the second portion of the fallopian tube.

The broad ligament serves as a mesentery for the uterus, ovaries and the uterine tubes. It helps in maintaining the uterus in its position.

Dysgerminomas are the most common malignant germ cell tumors, appraising for about 35% to 45% of all ovarian cancers of germ cell origin in females.

Around the 9th day, cells from the hypoblast spread around the blastocoele, forming the exocoelomic or Heuser's membrane. When the blastocoele is surrounded by this membrane, it is referred to as the primary yolk sac or exocoelomic cavity.

The chorion laeve forms from the mural (abembryonic) pole of the embryo trophoblast.

The most common site of ectopic implantation is the uterine tube. The growth of the embryo in this site usually causes rupture of the tube and severe hemorrhage in the mother. Abdominally, an ectopic pregnancy often occurs in the rectouterine pouch, an area between the uterus and the rectum.