Although skin ulcers do not seem of great concern at a first glance, they are worrying conditions especially in people with diabetes, as they are at risk of developing diabetic neuropathy. Ulcers may also appear on the cheeks, soft palate, the tongue, and on the inside of the lower lip. These ulcers usually last from 7 to 14 days and can be painful. Discharges
Different types of discharges from ulcer are:
Serous, usually seen in healing ulcer
Purulent, seen in infected ulcer. Yellow creamy discharge is observed in staphylococcal infection; bloody opalescent discharge in streptococcal infection, while greenish discharge is seen in the case of Pseudomonas infection
Bloody (sanguineous), usually seen in malignant ulcers and in healing ulcers with healthy granulation tissue
Seropurulent
Serosanguinous
Serous with sulphur granules, seen in actinomycosis
Yellowish, as seen in tuberculous ulcer

Causes
The wounds from which ulcers arise can be caused by a wide variety of factors, but the main cause is impaired blood circulation. Especially, chronic wounds and ulcers are caused by poor circulation, either through cardiovascular issues or external pressure from a bed or a wheelchair. A very common and dangerous type of skin ulcer is caused by what are called pressure-sensitive sores, more commonly called bed sores, which are frequent in people who are bedridden or who use wheelchairs for long periods.Other causes producing skin ulcers include bacterial and viral infections, fungal infections and cancers. Blood disorders and chronic wounds can result in skin ulcers as well. Venous leg ulcers due to impaired circulation or a blood flow disorder are more common in the elderly.
Occipital twins are joined at the occipital lobe in the back of the head and vertical are joined on the top of the head and usually face opposite directions. The junctional diameter is often smaller in partial forms and occasionally an incomplete layer of bone may be present between the twins. Each child maintains independent calvarial convexities except at the common area of skull junction. The dura of both children may be intact or deficient and cortical gyri may interdigitate. Additionally, shared dural venous sinuses is usually absent, or, if it is present, negligible. These twins usually undergo successful separation and both twins may live to lead normal lives. Gestation and embryology
The exact nature of how conjoined twins develop in utero remains unclear. Embryologists have traditionally attributed identical twinning as "splitting or fission" of either the inner cell mass of pleuripotential cells or early embryonic disc at 13–14 days of gestation just before the primitive streak. Some theorists suggested that conjoined twins develop as a result of the failed fusion of a single fertilized ovum. However a new hypothesis suggests that cranial fusion occurs between two separate embryos before the end of the 4th week of gestation. This can happen because the cranial neuropore is still open, which is responsible for the ultimate fusion and formation of the brain stem and central nervous system. Furthermore, this secondary fusion of embryonic discs could implicate that intact skin will not fuse to other intact skin, including the ectoderm of the embryo.