Craniopagus twins, this phenomena is the result of an improper separation of the early, developing embryo. Normally, or as normally as an abnormal separation of an embryo can be, each half of the developing embryo would have separated entirely, resulting in identical twins; that didn’t happen here, instead parts of the skull, the meninges (three layers of tissue that lie between the brain and the skull, from deep to superficial they are the pia mater, the arachnoid mater and the dura mater) and sometimes even the brain is shared between the twins.
There are two types of ossification Endochondral and Intramembranous, here we can see prime examples of both.
Endochondral ossification is where hyaline cartilage is replaced by bone tissue, this happens when chondrocytes, which are the cell that makes hyaline cartilage, hypertrophy and die then begin to calcify. Blood vessels penetrate the primary ossification centre (the middle part of developing long bones - the metaphysis and diaphysis) and deposit pluripotent stem cells within the ossification centre, upon coming into contact with the calcified dead chondrocytes, these stem cells differentiate into osteoblasts; osteoblasts secrete bone matrix, which is the stuff that your bones are made of. The newest endochondral growth in this baby is happening at the epiphyseal line, or, the growth plate, which is the dark line at the most proximal and distal end of the humerus. Growth in long bones like the humerus continues for about 18 years.
Intramembranous ossification is a little different, it is the replacement of primitive connective tissue with bone tissue, mesenchymal stem cells in this connective tissue differentiate into osteoprogenitor cells, clumps of these cells then differentiate further into osteoblasts which produce bone matrix in little clumps, you can see these clumps, called spicules, forming in the parietal bone of the skull, spicules are mineralised bone matrix within connective tissue, they will eventually replace all of the primitive connective tissue.
Some other nifty features of this skeleton:
There aren’t any carpels, even newborns don’t have a complete set of carpels, they finish ossifying after birth.
The ends of the long bones (epiphyses) haven’t formed yet.
The most lateral end of the clavicle is visible just above the scapula, this is the first bone to begin ossifying and the last to complete it.
Bloated whale carcass during the decomposition process
Severe defense wounds. The victim was killed by her husband.
More from the heart dissection!
This is a bull’s heart that we dissected today!
The white, branching, stringy fibres here are the chordae tendineae, they attach to the papillary muscles within the left and right ventricle, which contract shortly before systole and tug on the chordae tendineae, which in turn pulls the heart valves closed to prevent a back-flow of blood in the heart.
Also note how fucking thick the wall of the left ventricle/atrium is compared to the right, that’s a meaty ventricle - hot damn!
A human embryo at approximatey 8 weeks.
Idiopathic scrotal calcification is a rare disorder of unknown origin characterized by calcium level of the dermis of the scrotum. Appears in healthy males during childhood or early adulthood, manifested clinically by papules or subcutaneous nodules showing a scrotal location blanquecinamarillenta coloring; injuries have a hard consistency on palpation and occasionally eliminate a pasty white material; are usually asymptomatic, although they may be accompanied by a sense of weight at the genital level.