Histology, the study of biological tissues, is a fun subject in the first year at the IMS at the University of Milan. We observe — literally — the human body at tiny scales.
Histology is a normal part of medical school curricula worldwide. At IMS, it is included in a semester-long module called the Human Body, which also includes embryology and anatomy. Histology is taught by the same professor as cellular biology. The fact that she teaches both courses allows her to integrate, conceptually, the structure and function of tissues and cells. Like each of the three modules this semester, the Human Body will be tested in February.
Our histology lessons are a mixture of lectures and “practicals”, which are sessions in the microscope laboratory, in which we look at real specimens of tissues from humans, cats, rabbits, and other species. Yesterday, the profundity hit me of the fact that organisms so different in external appearance and behavior could have organs so similar. A cat’s pancreas, under a microscope, looks like a human’s pancreas. As different — indeed, perhaps, chauvinistically superior — as people may consider ourselves to cats, the fact is, we are almost exactly the same on the inside.
Histology is colorful. Indeed, in order to highlight specific cellular structures, scientists use stains of blue, red, and yellow. Textbooks and online resources are filled with microscopic images of tissues, in all kinds of hues. They are beautiful.
So far, learning histology seems largely to involve two different components.
The first component is factual, verbal and quantitative knowledge. How many liters of blood are there in the human body (about 5)? Do epithelial tissue — which line the cavities and surfaces of the body — contain blood vessels (no, to my surprise)? How exactly do the cells in glands secrete substances like sweat or hormones (check out merocrine, apocrine, and holocrine secretion)?
The second is practical ability to identify tissue. We have to be able to look into a microscope, adjust for magnification, and say what exactly we are looking at. Is it muscle? Nerve? Connective tissue? What kind — bone, cartilage? Exactly what kind of cartilage is it — hylaline, elastic, fibrous? Where are the cells, and what kind are they? Perhaps most interestingly, why are the components built the way they are? What does that have to do with their function? Hyaline cartilage, for example, occurs at the articulation points of some bones, and so has a type of collagen that makes it suitable to the particular purpose of flexibility and bone growth. When it degenerates, it can lead to arthritis.
When I got back to my apartment yesterday, I kept on looking at my own body, and thinking about how its different parts — skin, joints, intestines — are made of many different and precise types of cells, all of which fulfill their function so efficiently. Histology can help you to appreciate this, in the same way that you might also find it fascinating to look at a skyscraper or a jumbo jet up close, and examine all the little parts from which it is manufactured.