Biology

Our bodies are complicated and endlessly fascinating. It is estimated that there are roughly 10,000 trillion cells in the average human body, although estimates vary hugely and as many as 50 trillion cells has also been given as an average.

The cell is one of our most basic structures and before we identify the largest and smallest cells in our bodies, let’s take a look at what a cell actually is.

There are many different types of cell in the human body. These include nerve, muscle, sperm and egg cells. To be a little more technical, there are two cell types that make up everything that lives on Earth.

These are called Prokaryotic and Eukaryotic. The former contain no ‘nucleus’ and the latter, like the cells in the human body, have a ‘nucleus’.

A human cell is held within a cell, or plasma, membrane. Inside the membrane are the cytoplasm and the nucleus. A cell is a complex structure and, if you want to know more about how a human cell looks and functions, this resource has vast amounts of information.

So, what does a cell do? Of course, it encloses the cytoplasm but it serves other functions. The cell forms what is known as a selective barrier. It allows certain matter in and keeps other, undesirable matter out.

An excellent interactive video about cells, cytoplasm and organelles can be found here. This site is especially useful if you have a child doing a project on human life.

We’ve established a rough idea of what a cell is and what they do and now it’s time to identify the answers to the question ‘Which are the largest and smallest cells in the human body?’

Both the largest and smallest cells in the human body fall into the category of ‘gametes’. A gamete is a reproductive cell that contains chromosomes, sperm and ova. The fusion of male and female gametes produces the fertilized egg that will eventually develop into new life.

Humans have two particular types of these gametes, the male sperm which is capable of movement (motile) and the female ovum which do not move (non-motile).

The largest cell in the human body is the female ovum or egg. Too put this into perspective, when we use the term largest, we’re not talking the size of hen’s eggs.

The human ovum is roughly one millimeter across and is only just visible to the naked eye. You can find out everything you ever wanted to know about the structure and function of the human ovum here.

This leaves us with the smallest cell in the human body, the partner of the ovum, the sperm. The male equivalent of the female gamete, commonly known as the sperm cell, or spermatozoon, is on 60 micrometers in length.

It is not visible to the naked eye, a microscope usually being used to examine them. Everything you might want to know about the sperm can be found here.

The answer to what are the largest and smallest cells in the human body is probably not one you were expecting, but step forward sperm cell and ovum.